From 99b5b8c775e3a3b6d92c27f1e655c5b6078a7a1a Mon Sep 17 00:00:00 2001 From: Neur0toxine Date: Sat, 18 Nov 2023 21:51:44 +0300 Subject: [PATCH] ssh with fake host support (wip) --- Makefile | 15 + go.mod | 3 +- internal/server/driver/ssh/driver.go | 2 +- internal/server/driver/ssh/sshtun/auth.go | 2 +- internal/server/driver/ssh/sshtun/printer.go | 2 +- .../server/driver/ssh/sshtun/sish_compat.go | 76 - internal/server/driver/ssh/sshtun/ssh.go | 21 +- patch/ssh_fakehost.patch | 23 + pkg/proto/ssh/agent/client.go | 854 ++++++++ pkg/proto/ssh/agent/forward.go | 103 + pkg/proto/ssh/agent/keyring.go | 241 +++ pkg/proto/ssh/agent/server.go | 570 ++++++ pkg/proto/ssh/buffer.go | 97 + pkg/proto/ssh/certs.go | 611 ++++++ pkg/proto/ssh/channel.go | 633 ++++++ pkg/proto/ssh/cipher.go | 789 ++++++++ pkg/proto/ssh/client.go | 282 +++ pkg/proto/ssh/client_auth.go | 761 ++++++++ pkg/proto/ssh/common.go | 468 +++++ pkg/proto/ssh/connection.go | 143 ++ pkg/proto/ssh/doc.go | 23 + pkg/proto/ssh/handshake.go | 758 ++++++++ .../ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go | 93 + .../ssh/internal/poly1305/bits_compat.go | 39 + .../ssh/internal/poly1305/bits_go1.13.go | 21 + pkg/proto/ssh/internal/poly1305/mac_noasm.go | 9 + pkg/proto/ssh/internal/poly1305/poly1305.go | 99 + pkg/proto/ssh/internal/poly1305/sum_amd64.go | 47 + pkg/proto/ssh/internal/poly1305/sum_amd64.s | 108 ++ .../ssh/internal/poly1305/sum_generic.go | 309 +++ .../ssh/internal/poly1305/sum_ppc64le.go | 47 + pkg/proto/ssh/internal/poly1305/sum_ppc64le.s | 181 ++ pkg/proto/ssh/internal/poly1305/sum_s390x.go | 76 + pkg/proto/ssh/internal/poly1305/sum_s390x.s | 503 +++++ pkg/proto/ssh/kex.go | 786 ++++++++ pkg/proto/ssh/keys.go | 1728 +++++++++++++++++ pkg/proto/ssh/knownhosts/knownhosts.go | 540 ++++++ pkg/proto/ssh/mac.go | 68 + pkg/proto/ssh/messages.go | 891 +++++++++ pkg/proto/ssh/mux.go | 357 ++++ pkg/proto/ssh/server.go | 800 ++++++++ pkg/proto/ssh/session.go | 647 ++++++ pkg/proto/ssh/ssh_gss.go | 139 ++ pkg/proto/ssh/streamlocal.go | 116 ++ pkg/proto/ssh/tcpip.go | 478 +++++ pkg/proto/ssh/terminal/terminal.go | 76 + pkg/proto/ssh/transport.go | 358 ++++ 47 files changed, 14906 insertions(+), 87 deletions(-) delete mode 100644 internal/server/driver/ssh/sshtun/sish_compat.go create mode 100644 patch/ssh_fakehost.patch create mode 100644 pkg/proto/ssh/agent/client.go create mode 100644 pkg/proto/ssh/agent/forward.go create mode 100644 pkg/proto/ssh/agent/keyring.go create mode 100644 pkg/proto/ssh/agent/server.go create mode 100644 pkg/proto/ssh/buffer.go create mode 100644 pkg/proto/ssh/certs.go create mode 100644 pkg/proto/ssh/channel.go create mode 100644 pkg/proto/ssh/cipher.go create mode 100644 pkg/proto/ssh/client.go create mode 100644 pkg/proto/ssh/client_auth.go create mode 100644 pkg/proto/ssh/common.go create mode 100644 pkg/proto/ssh/connection.go create mode 100644 pkg/proto/ssh/doc.go create mode 100644 pkg/proto/ssh/handshake.go create mode 100644 pkg/proto/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go create mode 100644 pkg/proto/ssh/internal/poly1305/bits_compat.go create mode 100644 pkg/proto/ssh/internal/poly1305/bits_go1.13.go create mode 100644 pkg/proto/ssh/internal/poly1305/mac_noasm.go create mode 100644 pkg/proto/ssh/internal/poly1305/poly1305.go create mode 100644 pkg/proto/ssh/internal/poly1305/sum_amd64.go create mode 100644 pkg/proto/ssh/internal/poly1305/sum_amd64.s create mode 100644 pkg/proto/ssh/internal/poly1305/sum_generic.go create mode 100644 pkg/proto/ssh/internal/poly1305/sum_ppc64le.go create mode 100644 pkg/proto/ssh/internal/poly1305/sum_ppc64le.s create mode 100644 pkg/proto/ssh/internal/poly1305/sum_s390x.go create mode 100644 pkg/proto/ssh/internal/poly1305/sum_s390x.s create mode 100644 pkg/proto/ssh/kex.go create mode 100644 pkg/proto/ssh/keys.go create mode 100644 pkg/proto/ssh/knownhosts/knownhosts.go create mode 100644 pkg/proto/ssh/mac.go create mode 100644 pkg/proto/ssh/messages.go create mode 100644 pkg/proto/ssh/mux.go create mode 100644 pkg/proto/ssh/server.go create mode 100644 pkg/proto/ssh/session.go create mode 100644 pkg/proto/ssh/ssh_gss.go create mode 100644 pkg/proto/ssh/streamlocal.go create mode 100644 pkg/proto/ssh/tcpip.go create mode 100644 pkg/proto/ssh/terminal/terminal.go create mode 100644 pkg/proto/ssh/transport.go diff --git a/Makefile b/Makefile index a7073df..b4aadae 100644 --- a/Makefile +++ b/Makefile @@ -39,3 +39,18 @@ generate: install_protobuf: @go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.28 @go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@v1.2 + +update_sshlib: + @rm -rf cryptolib && \ + git clone https://go.googlesource.com/crypto cryptolib && \ + rm -rf pkg/proto/ssh && \ + mv cryptolib/ssh pkg/proto/ && \ + mv cryptolib/internal/poly1305 pkg/proto/ssh/internal/ && \ + find pkg/proto/ssh -type f -name '*.go' -exec sed -i 's?golang.org/x/crypto/ssh?github.com/Neur0toxine/sshpoke/pkg/proto/ssh?g' {} \; && \ + find pkg/proto/ssh -type f -name '*.go' -exec sed -i 's?golang.org/x/crypto/internal/poly1305?github.com/Neur0toxine/sshpoke/pkg/proto/ssh/internal/poly1305?g' {} \; && \ + find pkg/proto/ssh -type f -name '*_test.go' -delete && \ + patch -p0 < patch/ssh_fakehost.patch && \ + rm -rf pkg/proto/ssh/test && \ + rm -rf pkg/proto/ssh/testdata && \ + rm -rf cryptolib + diff --git a/go.mod b/go.mod index 8ecb0e3..2eac9ba 100644 --- a/go.mod +++ b/go.mod @@ -15,6 +15,8 @@ require ( go.uber.org/zap v1.26.0 golang.design/x/lockfree v0.0.1 golang.org/x/crypto v0.14.0 + golang.org/x/sys v0.13.0 + golang.org/x/term v0.13.0 google.golang.org/grpc v1.58.2 google.golang.org/protobuf v1.31.0 ) @@ -52,7 +54,6 @@ require ( golang.org/x/mod v0.12.0 // indirect golang.org/x/net v0.17.0 // indirect golang.org/x/sync v0.3.0 // indirect - golang.org/x/sys v0.13.0 // indirect golang.org/x/text v0.13.0 // indirect golang.org/x/tools v0.13.0 // indirect google.golang.org/genproto/googleapis/rpc v0.0.0-20230920204549-e6e6cdab5c13 // indirect diff --git a/internal/server/driver/ssh/driver.go b/internal/server/driver/ssh/driver.go index 220ff43..852210f 100644 --- a/internal/server/driver/ssh/driver.go +++ b/internal/server/driver/ssh/driver.go @@ -13,7 +13,7 @@ import ( "github.com/Neur0toxine/sshpoke/internal/server/driver/ssh/types" "github.com/Neur0toxine/sshpoke/internal/server/driver/util" "github.com/Neur0toxine/sshpoke/pkg/dto" - "golang.org/x/crypto/ssh" + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" ) type SSH struct { diff --git a/internal/server/driver/ssh/sshtun/auth.go b/internal/server/driver/ssh/sshtun/auth.go index 80bfe71..106d84e 100644 --- a/internal/server/driver/ssh/sshtun/auth.go +++ b/internal/server/driver/ssh/sshtun/auth.go @@ -8,7 +8,7 @@ import ( "strings" "github.com/Neur0toxine/sshpoke/internal/server/driver/ssh/types" - "golang.org/x/crypto/ssh" + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" ) func AuthKeyFile(keyFile types.SmartPath) (ssh.AuthMethod, error) { diff --git a/internal/server/driver/ssh/sshtun/printer.go b/internal/server/driver/ssh/sshtun/printer.go index 89ad3c8..b5653cd 100644 --- a/internal/server/driver/ssh/sshtun/printer.go +++ b/internal/server/driver/ssh/sshtun/printer.go @@ -3,8 +3,8 @@ package sshtun import ( "bufio" + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" "go.uber.org/zap" - "golang.org/x/crypto/ssh" ) func StdoutPrinterSessionCallback(log *zap.SugaredLogger) SessionCallback { diff --git a/internal/server/driver/ssh/sshtun/sish_compat.go b/internal/server/driver/ssh/sshtun/sish_compat.go deleted file mode 100644 index 9f8c2d4..0000000 --- a/internal/server/driver/ssh/sshtun/sish_compat.go +++ /dev/null @@ -1,76 +0,0 @@ -package sshtun - -import ( - "errors" - "net" - "reflect" - "sync" - "unsafe" - - "golang.org/x/crypto/ssh" -) - -type sishHostListener struct { - parent *ssh.Client -} - -func newSishHostListener(parent *ssh.Client) *sishHostListener { - return &sishHostListener{parent: parent} -} - -func (c *sishHostListener) ListenFakeRemoteHost(ep Endpoint) (net.Listener, error) { - c.doHandleForwardsOnce() - m := channelForwardMsg{ - ep.Host, - uint32(ep.Port), - } - // send message - ok, resp, err := c.parent.SendRequest("tcpip-forward", true, ssh.Marshal(&m)) - if err != nil { - return nil, err - } - if !ok { - return nil, errors.New("ssh: tcpip-forward request denied by peer") - } - - laddr := &net.TCPAddr{ - IP: net.ParseIP("127.0.0.1"), - Port: ep.Port, - } - if ep.Port == 0 { - var p struct { - Port uint32 - } - if err := ssh.Unmarshal(resp, &p); err != nil { - return nil, err - } - - laddr.Port = int(p.Port) - } - c.registerForward(laddr) - return nil, nil -} - -func (c *sishHostListener) registerForward(addr *net.TCPAddr) { - cl := reflect.ValueOf(c.parent).Elem() - forwardsUn := cl.FieldByName("forwards") - forwards := reflect.NewAt(forwardsUn.Type(), unsafe.Pointer(forwardsUn.UnsafeAddr())).Elem() - forwardVal := forwards.MethodByName("add").Call([]reflect.Value{reflect.ValueOf(addr)})[0] - _ = forwardVal -} - -func (c *sishHostListener) doHandleForwardsOnce() { - cl := reflect.ValueOf(c.parent) - clVal := cl.Elem() - onceField := clVal.FieldByName("handleForwardsOnce") - once := reflect.NewAt(onceField.Type(), unsafe.Pointer(onceField.UnsafeAddr())).Interface().(*sync.Once) - handleForwards := clVal.MethodByName("handleForwards") - once.Do(func() { - handleForwards.Call(nil) - }) -} - -type channelForwardMsg struct { - addr string - rport uint32 -} diff --git a/internal/server/driver/ssh/sshtun/ssh.go b/internal/server/driver/ssh/sshtun/ssh.go index 04f910c..791eada 100644 --- a/internal/server/driver/ssh/sshtun/ssh.go +++ b/internal/server/driver/ssh/sshtun/ssh.go @@ -4,15 +4,14 @@ import ( "context" "fmt" "net" - "os" "sync" "sync/atomic" "time" + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" "github.com/function61/gokit/app/backoff" "github.com/function61/gokit/io/bidipipe" "go.uber.org/zap" - "golang.org/x/crypto/ssh" ) type SessionCallback func(*ssh.Session) @@ -132,12 +131,18 @@ func (c *Tunnel) connect(ctx context.Context, sessionCb SessionCallback) error { // // nonblocking flow: if Accept() call fails, stops goroutine and returns error on ch listenerStopped func (c *Tunnel) reverseForwardOnePort(sshClient *ssh.Client, listenerStopped chan<- error) error { + var ( + listener net.Listener + err error + ) if c.fakeRemoteHost { - newSishHostListener(sshClient).ListenFakeRemoteHost(c.forward.Remote) - time.Sleep(time.Second) - os.Exit(0) + listener, err = sshClient.ListenTCP(&net.TCPAddr{ + IP: c.ipFromAddr(sshClient.Conn.RemoteAddr()), + Port: c.forward.Remote.Port, + }, c.forward.Remote.Host) + } else { + listener, err = sshClient.Listen("tcp", c.forward.Remote.String()) } - listener, err := sshClient.Listen("tcp", c.forward.Remote.String()) if err != nil { return err } @@ -160,7 +165,9 @@ func (c *Tunnel) reverseForwardOnePort(sshClient *ssh.Client, listenerStopped ch return nil } -func (c *Tunnel) listenTCPWithoutResolving() { +func (c *Tunnel) ipFromAddr(addr net.Addr) net.IP { + host, _, _ := net.SplitHostPort(addr.String()) + return net.ParseIP(host) } func handleReverseForwardConn(client net.Conn, forward Forward, log *zap.SugaredLogger) { diff --git a/patch/ssh_fakehost.patch b/patch/ssh_fakehost.patch new file mode 100644 index 0000000..cd62087 --- /dev/null +++ b/patch/ssh_fakehost.patch @@ -0,0 +1,23 @@ +--- pkg/proto/ssh/tcpip.go 2023-11-18 21:39:15.394837005 +0300 ++++ pkg/proto/ssh/tcpip.go 2023-11-18 21:38:25.706173351 +0300 +@@ -101,14 +101,18 @@ + // ListenTCP requests the remote peer open a listening socket + // on laddr. Incoming connections will be available by calling + // Accept on the returned net.Listener. +-func (c *Client) ListenTCP(laddr *net.TCPAddr) (net.Listener, error) { ++func (c *Client) ListenTCP(laddr *net.TCPAddr, fakeHost ...string) (net.Listener, error) { + c.handleForwardsOnce.Do(c.handleForwards) + if laddr.Port == 0 && isBrokenOpenSSHVersion(string(c.ServerVersion())) { + return c.autoPortListenWorkaround(laddr) + } + ++ host := laddr.IP.String() ++ if len(fakeHost) > 0 { ++ host = fakeHost[0] ++ } + m := channelForwardMsg{ +- laddr.IP.String(), ++ host, + uint32(laddr.Port), + } + // send message diff --git a/pkg/proto/ssh/agent/client.go b/pkg/proto/ssh/agent/client.go new file mode 100644 index 0000000..2a0d0de --- /dev/null +++ b/pkg/proto/ssh/agent/client.go @@ -0,0 +1,854 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package agent implements the ssh-agent protocol, and provides both +// a client and a server. The client can talk to a standard ssh-agent +// that uses UNIX sockets, and one could implement an alternative +// ssh-agent process using the sample server. +// +// References: +// +// [PROTOCOL.agent]: https://tools.ietf.org/html/draft-miller-ssh-agent-00 +package agent // import "github.com/Neur0toxine/sshpoke/pkg/proto/ssh/agent" + +import ( + "bytes" + "crypto/dsa" + "crypto/ecdsa" + "crypto/ed25519" + "crypto/elliptic" + "crypto/rsa" + "encoding/base64" + "encoding/binary" + "errors" + "fmt" + "io" + "math/big" + "sync" + + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" +) + +// SignatureFlags represent additional flags that can be passed to the signature +// requests an defined in [PROTOCOL.agent] section 4.5.1. +type SignatureFlags uint32 + +// SignatureFlag values as defined in [PROTOCOL.agent] section 5.3. +const ( + SignatureFlagReserved SignatureFlags = 1 << iota + SignatureFlagRsaSha256 + SignatureFlagRsaSha512 +) + +// Agent represents the capabilities of an ssh-agent. +type Agent interface { + // List returns the identities known to the agent. + List() ([]*Key, error) + + // Sign has the agent sign the data using a protocol 2 key as defined + // in [PROTOCOL.agent] section 2.6.2. + Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) + + // Add adds a private key to the agent. + Add(key AddedKey) error + + // Remove removes all identities with the given public key. + Remove(key ssh.PublicKey) error + + // RemoveAll removes all identities. + RemoveAll() error + + // Lock locks the agent. Sign and Remove will fail, and List will empty an empty list. + Lock(passphrase []byte) error + + // Unlock undoes the effect of Lock + Unlock(passphrase []byte) error + + // Signers returns signers for all the known keys. + Signers() ([]ssh.Signer, error) +} + +type ExtendedAgent interface { + Agent + + // SignWithFlags signs like Sign, but allows for additional flags to be sent/received + SignWithFlags(key ssh.PublicKey, data []byte, flags SignatureFlags) (*ssh.Signature, error) + + // Extension processes a custom extension request. Standard-compliant agents are not + // required to support any extensions, but this method allows agents to implement + // vendor-specific methods or add experimental features. See [PROTOCOL.agent] section 4.7. + // If agent extensions are unsupported entirely this method MUST return an + // ErrExtensionUnsupported error. Similarly, if just the specific extensionType in + // the request is unsupported by the agent then ErrExtensionUnsupported MUST be + // returned. + // + // In the case of success, since [PROTOCOL.agent] section 4.7 specifies that the contents + // of the response are unspecified (including the type of the message), the complete + // response will be returned as a []byte slice, including the "type" byte of the message. + Extension(extensionType string, contents []byte) ([]byte, error) +} + +// ConstraintExtension describes an optional constraint defined by users. +type ConstraintExtension struct { + // ExtensionName consist of a UTF-8 string suffixed by the + // implementation domain following the naming scheme defined + // in Section 4.2 of RFC 4251, e.g. "foo@example.com". + ExtensionName string + // ExtensionDetails contains the actual content of the extended + // constraint. + ExtensionDetails []byte +} + +// AddedKey describes an SSH key to be added to an Agent. +type AddedKey struct { + // PrivateKey must be a *rsa.PrivateKey, *dsa.PrivateKey, + // ed25519.PrivateKey or *ecdsa.PrivateKey, which will be inserted into the + // agent. + PrivateKey interface{} + // Certificate, if not nil, is communicated to the agent and will be + // stored with the key. + Certificate *ssh.Certificate + // Comment is an optional, free-form string. + Comment string + // LifetimeSecs, if not zero, is the number of seconds that the + // agent will store the key for. + LifetimeSecs uint32 + // ConfirmBeforeUse, if true, requests that the agent confirm with the + // user before each use of this key. + ConfirmBeforeUse bool + // ConstraintExtensions are the experimental or private-use constraints + // defined by users. + ConstraintExtensions []ConstraintExtension +} + +// See [PROTOCOL.agent], section 3. +const ( + agentRequestV1Identities = 1 + agentRemoveAllV1Identities = 9 + + // 3.2 Requests from client to agent for protocol 2 key operations + agentAddIdentity = 17 + agentRemoveIdentity = 18 + agentRemoveAllIdentities = 19 + agentAddIDConstrained = 25 + + // 3.3 Key-type independent requests from client to agent + agentAddSmartcardKey = 20 + agentRemoveSmartcardKey = 21 + agentLock = 22 + agentUnlock = 23 + agentAddSmartcardKeyConstrained = 26 + + // 3.7 Key constraint identifiers + agentConstrainLifetime = 1 + agentConstrainConfirm = 2 + // Constraint extension identifier up to version 2 of the protocol. A + // backward incompatible change will be required if we want to add support + // for SSH_AGENT_CONSTRAIN_MAXSIGN which uses the same ID. + agentConstrainExtensionV00 = 3 + // Constraint extension identifier in version 3 and later of the protocol. + agentConstrainExtension = 255 +) + +// maxAgentResponseBytes is the maximum agent reply size that is accepted. This +// is a sanity check, not a limit in the spec. +const maxAgentResponseBytes = 16 << 20 + +// Agent messages: +// These structures mirror the wire format of the corresponding ssh agent +// messages found in [PROTOCOL.agent]. + +// 3.4 Generic replies from agent to client +const agentFailure = 5 + +type failureAgentMsg struct{} + +const agentSuccess = 6 + +type successAgentMsg struct{} + +// See [PROTOCOL.agent], section 2.5.2. +const agentRequestIdentities = 11 + +type requestIdentitiesAgentMsg struct{} + +// See [PROTOCOL.agent], section 2.5.2. +const agentIdentitiesAnswer = 12 + +type identitiesAnswerAgentMsg struct { + NumKeys uint32 `sshtype:"12"` + Keys []byte `ssh:"rest"` +} + +// See [PROTOCOL.agent], section 2.6.2. +const agentSignRequest = 13 + +type signRequestAgentMsg struct { + KeyBlob []byte `sshtype:"13"` + Data []byte + Flags uint32 +} + +// See [PROTOCOL.agent], section 2.6.2. + +// 3.6 Replies from agent to client for protocol 2 key operations +const agentSignResponse = 14 + +type signResponseAgentMsg struct { + SigBlob []byte `sshtype:"14"` +} + +type publicKey struct { + Format string + Rest []byte `ssh:"rest"` +} + +// 3.7 Key constraint identifiers +type constrainLifetimeAgentMsg struct { + LifetimeSecs uint32 `sshtype:"1"` +} + +type constrainExtensionAgentMsg struct { + ExtensionName string `sshtype:"255|3"` + ExtensionDetails []byte + + // Rest is a field used for parsing, not part of message + Rest []byte `ssh:"rest"` +} + +// See [PROTOCOL.agent], section 4.7 +const agentExtension = 27 +const agentExtensionFailure = 28 + +// ErrExtensionUnsupported indicates that an extension defined in +// [PROTOCOL.agent] section 4.7 is unsupported by the agent. Specifically this +// error indicates that the agent returned a standard SSH_AGENT_FAILURE message +// as the result of a SSH_AGENTC_EXTENSION request. Note that the protocol +// specification (and therefore this error) does not distinguish between a +// specific extension being unsupported and extensions being unsupported entirely. +var ErrExtensionUnsupported = errors.New("agent: extension unsupported") + +type extensionAgentMsg struct { + ExtensionType string `sshtype:"27"` + // NOTE: this matches OpenSSH's PROTOCOL.agent, not the IETF draft [PROTOCOL.agent], + // so that it matches what OpenSSH actually implements in the wild. + Contents []byte `ssh:"rest"` +} + +// Key represents a protocol 2 public key as defined in +// [PROTOCOL.agent], section 2.5.2. +type Key struct { + Format string + Blob []byte + Comment string +} + +func clientErr(err error) error { + return fmt.Errorf("agent: client error: %v", err) +} + +// String returns the storage form of an agent key with the format, base64 +// encoded serialized key, and the comment if it is not empty. +func (k *Key) String() string { + s := string(k.Format) + " " + base64.StdEncoding.EncodeToString(k.Blob) + + if k.Comment != "" { + s += " " + k.Comment + } + + return s +} + +// Type returns the public key type. +func (k *Key) Type() string { + return k.Format +} + +// Marshal returns key blob to satisfy the ssh.PublicKey interface. +func (k *Key) Marshal() []byte { + return k.Blob +} + +// Verify satisfies the ssh.PublicKey interface. +func (k *Key) Verify(data []byte, sig *ssh.Signature) error { + pubKey, err := ssh.ParsePublicKey(k.Blob) + if err != nil { + return fmt.Errorf("agent: bad public key: %v", err) + } + return pubKey.Verify(data, sig) +} + +type wireKey struct { + Format string + Rest []byte `ssh:"rest"` +} + +func parseKey(in []byte) (out *Key, rest []byte, err error) { + var record struct { + Blob []byte + Comment string + Rest []byte `ssh:"rest"` + } + + if err := ssh.Unmarshal(in, &record); err != nil { + return nil, nil, err + } + + var wk wireKey + if err := ssh.Unmarshal(record.Blob, &wk); err != nil { + return nil, nil, err + } + + return &Key{ + Format: wk.Format, + Blob: record.Blob, + Comment: record.Comment, + }, record.Rest, nil +} + +// client is a client for an ssh-agent process. +type client struct { + // conn is typically a *net.UnixConn + conn io.ReadWriter + // mu is used to prevent concurrent access to the agent + mu sync.Mutex +} + +// NewClient returns an Agent that talks to an ssh-agent process over +// the given connection. +func NewClient(rw io.ReadWriter) ExtendedAgent { + return &client{conn: rw} +} + +// call sends an RPC to the agent. On success, the reply is +// unmarshaled into reply and replyType is set to the first byte of +// the reply, which contains the type of the message. +func (c *client) call(req []byte) (reply interface{}, err error) { + buf, err := c.callRaw(req) + if err != nil { + return nil, err + } + reply, err = unmarshal(buf) + if err != nil { + return nil, clientErr(err) + } + return reply, nil +} + +// callRaw sends an RPC to the agent. On success, the raw +// bytes of the response are returned; no unmarshalling is +// performed on the response. +func (c *client) callRaw(req []byte) (reply []byte, err error) { + c.mu.Lock() + defer c.mu.Unlock() + + msg := make([]byte, 4+len(req)) + binary.BigEndian.PutUint32(msg, uint32(len(req))) + copy(msg[4:], req) + if _, err = c.conn.Write(msg); err != nil { + return nil, clientErr(err) + } + + var respSizeBuf [4]byte + if _, err = io.ReadFull(c.conn, respSizeBuf[:]); err != nil { + return nil, clientErr(err) + } + respSize := binary.BigEndian.Uint32(respSizeBuf[:]) + if respSize > maxAgentResponseBytes { + return nil, clientErr(errors.New("response too large")) + } + + buf := make([]byte, respSize) + if _, err = io.ReadFull(c.conn, buf); err != nil { + return nil, clientErr(err) + } + return buf, nil +} + +func (c *client) simpleCall(req []byte) error { + resp, err := c.call(req) + if err != nil { + return err + } + if _, ok := resp.(*successAgentMsg); ok { + return nil + } + return errors.New("agent: failure") +} + +func (c *client) RemoveAll() error { + return c.simpleCall([]byte{agentRemoveAllIdentities}) +} + +func (c *client) Remove(key ssh.PublicKey) error { + req := ssh.Marshal(&agentRemoveIdentityMsg{ + KeyBlob: key.Marshal(), + }) + return c.simpleCall(req) +} + +func (c *client) Lock(passphrase []byte) error { + req := ssh.Marshal(&agentLockMsg{ + Passphrase: passphrase, + }) + return c.simpleCall(req) +} + +func (c *client) Unlock(passphrase []byte) error { + req := ssh.Marshal(&agentUnlockMsg{ + Passphrase: passphrase, + }) + return c.simpleCall(req) +} + +// List returns the identities known to the agent. +func (c *client) List() ([]*Key, error) { + // see [PROTOCOL.agent] section 2.5.2. + req := []byte{agentRequestIdentities} + + msg, err := c.call(req) + if err != nil { + return nil, err + } + + switch msg := msg.(type) { + case *identitiesAnswerAgentMsg: + if msg.NumKeys > maxAgentResponseBytes/8 { + return nil, errors.New("agent: too many keys in agent reply") + } + keys := make([]*Key, msg.NumKeys) + data := msg.Keys + for i := uint32(0); i < msg.NumKeys; i++ { + var key *Key + var err error + if key, data, err = parseKey(data); err != nil { + return nil, err + } + keys[i] = key + } + return keys, nil + case *failureAgentMsg: + return nil, errors.New("agent: failed to list keys") + } + panic("unreachable") +} + +// Sign has the agent sign the data using a protocol 2 key as defined +// in [PROTOCOL.agent] section 2.6.2. +func (c *client) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) { + return c.SignWithFlags(key, data, 0) +} + +func (c *client) SignWithFlags(key ssh.PublicKey, data []byte, flags SignatureFlags) (*ssh.Signature, error) { + req := ssh.Marshal(signRequestAgentMsg{ + KeyBlob: key.Marshal(), + Data: data, + Flags: uint32(flags), + }) + + msg, err := c.call(req) + if err != nil { + return nil, err + } + + switch msg := msg.(type) { + case *signResponseAgentMsg: + var sig ssh.Signature + if err := ssh.Unmarshal(msg.SigBlob, &sig); err != nil { + return nil, err + } + + return &sig, nil + case *failureAgentMsg: + return nil, errors.New("agent: failed to sign challenge") + } + panic("unreachable") +} + +// unmarshal parses an agent message in packet, returning the parsed +// form and the message type of packet. +func unmarshal(packet []byte) (interface{}, error) { + if len(packet) < 1 { + return nil, errors.New("agent: empty packet") + } + var msg interface{} + switch packet[0] { + case agentFailure: + return new(failureAgentMsg), nil + case agentSuccess: + return new(successAgentMsg), nil + case agentIdentitiesAnswer: + msg = new(identitiesAnswerAgentMsg) + case agentSignResponse: + msg = new(signResponseAgentMsg) + case agentV1IdentitiesAnswer: + msg = new(agentV1IdentityMsg) + default: + return nil, fmt.Errorf("agent: unknown type tag %d", packet[0]) + } + if err := ssh.Unmarshal(packet, msg); err != nil { + return nil, err + } + return msg, nil +} + +type rsaKeyMsg struct { + Type string `sshtype:"17|25"` + N *big.Int + E *big.Int + D *big.Int + Iqmp *big.Int // IQMP = Inverse Q Mod P + P *big.Int + Q *big.Int + Comments string + Constraints []byte `ssh:"rest"` +} + +type dsaKeyMsg struct { + Type string `sshtype:"17|25"` + P *big.Int + Q *big.Int + G *big.Int + Y *big.Int + X *big.Int + Comments string + Constraints []byte `ssh:"rest"` +} + +type ecdsaKeyMsg struct { + Type string `sshtype:"17|25"` + Curve string + KeyBytes []byte + D *big.Int + Comments string + Constraints []byte `ssh:"rest"` +} + +type ed25519KeyMsg struct { + Type string `sshtype:"17|25"` + Pub []byte + Priv []byte + Comments string + Constraints []byte `ssh:"rest"` +} + +// Insert adds a private key to the agent. +func (c *client) insertKey(s interface{}, comment string, constraints []byte) error { + var req []byte + switch k := s.(type) { + case *rsa.PrivateKey: + if len(k.Primes) != 2 { + return fmt.Errorf("agent: unsupported RSA key with %d primes", len(k.Primes)) + } + k.Precompute() + req = ssh.Marshal(rsaKeyMsg{ + Type: ssh.KeyAlgoRSA, + N: k.N, + E: big.NewInt(int64(k.E)), + D: k.D, + Iqmp: k.Precomputed.Qinv, + P: k.Primes[0], + Q: k.Primes[1], + Comments: comment, + Constraints: constraints, + }) + case *dsa.PrivateKey: + req = ssh.Marshal(dsaKeyMsg{ + Type: ssh.KeyAlgoDSA, + P: k.P, + Q: k.Q, + G: k.G, + Y: k.Y, + X: k.X, + Comments: comment, + Constraints: constraints, + }) + case *ecdsa.PrivateKey: + nistID := fmt.Sprintf("nistp%d", k.Params().BitSize) + req = ssh.Marshal(ecdsaKeyMsg{ + Type: "ecdsa-sha2-" + nistID, + Curve: nistID, + KeyBytes: elliptic.Marshal(k.Curve, k.X, k.Y), + D: k.D, + Comments: comment, + Constraints: constraints, + }) + case ed25519.PrivateKey: + req = ssh.Marshal(ed25519KeyMsg{ + Type: ssh.KeyAlgoED25519, + Pub: []byte(k)[32:], + Priv: []byte(k), + Comments: comment, + Constraints: constraints, + }) + // This function originally supported only *ed25519.PrivateKey, however the + // general idiom is to pass ed25519.PrivateKey by value, not by pointer. + // We still support the pointer variant for backwards compatibility. + case *ed25519.PrivateKey: + req = ssh.Marshal(ed25519KeyMsg{ + Type: ssh.KeyAlgoED25519, + Pub: []byte(*k)[32:], + Priv: []byte(*k), + Comments: comment, + Constraints: constraints, + }) + default: + return fmt.Errorf("agent: unsupported key type %T", s) + } + + // if constraints are present then the message type needs to be changed. + if len(constraints) != 0 { + req[0] = agentAddIDConstrained + } + + resp, err := c.call(req) + if err != nil { + return err + } + if _, ok := resp.(*successAgentMsg); ok { + return nil + } + return errors.New("agent: failure") +} + +type rsaCertMsg struct { + Type string `sshtype:"17|25"` + CertBytes []byte + D *big.Int + Iqmp *big.Int // IQMP = Inverse Q Mod P + P *big.Int + Q *big.Int + Comments string + Constraints []byte `ssh:"rest"` +} + +type dsaCertMsg struct { + Type string `sshtype:"17|25"` + CertBytes []byte + X *big.Int + Comments string + Constraints []byte `ssh:"rest"` +} + +type ecdsaCertMsg struct { + Type string `sshtype:"17|25"` + CertBytes []byte + D *big.Int + Comments string + Constraints []byte `ssh:"rest"` +} + +type ed25519CertMsg struct { + Type string `sshtype:"17|25"` + CertBytes []byte + Pub []byte + Priv []byte + Comments string + Constraints []byte `ssh:"rest"` +} + +// Add adds a private key to the agent. If a certificate is given, +// that certificate is added instead as public key. +func (c *client) Add(key AddedKey) error { + var constraints []byte + + if secs := key.LifetimeSecs; secs != 0 { + constraints = append(constraints, ssh.Marshal(constrainLifetimeAgentMsg{secs})...) + } + + if key.ConfirmBeforeUse { + constraints = append(constraints, agentConstrainConfirm) + } + + cert := key.Certificate + if cert == nil { + return c.insertKey(key.PrivateKey, key.Comment, constraints) + } + return c.insertCert(key.PrivateKey, cert, key.Comment, constraints) +} + +func (c *client) insertCert(s interface{}, cert *ssh.Certificate, comment string, constraints []byte) error { + var req []byte + switch k := s.(type) { + case *rsa.PrivateKey: + if len(k.Primes) != 2 { + return fmt.Errorf("agent: unsupported RSA key with %d primes", len(k.Primes)) + } + k.Precompute() + req = ssh.Marshal(rsaCertMsg{ + Type: cert.Type(), + CertBytes: cert.Marshal(), + D: k.D, + Iqmp: k.Precomputed.Qinv, + P: k.Primes[0], + Q: k.Primes[1], + Comments: comment, + Constraints: constraints, + }) + case *dsa.PrivateKey: + req = ssh.Marshal(dsaCertMsg{ + Type: cert.Type(), + CertBytes: cert.Marshal(), + X: k.X, + Comments: comment, + Constraints: constraints, + }) + case *ecdsa.PrivateKey: + req = ssh.Marshal(ecdsaCertMsg{ + Type: cert.Type(), + CertBytes: cert.Marshal(), + D: k.D, + Comments: comment, + Constraints: constraints, + }) + case ed25519.PrivateKey: + req = ssh.Marshal(ed25519CertMsg{ + Type: cert.Type(), + CertBytes: cert.Marshal(), + Pub: []byte(k)[32:], + Priv: []byte(k), + Comments: comment, + Constraints: constraints, + }) + // This function originally supported only *ed25519.PrivateKey, however the + // general idiom is to pass ed25519.PrivateKey by value, not by pointer. + // We still support the pointer variant for backwards compatibility. + case *ed25519.PrivateKey: + req = ssh.Marshal(ed25519CertMsg{ + Type: cert.Type(), + CertBytes: cert.Marshal(), + Pub: []byte(*k)[32:], + Priv: []byte(*k), + Comments: comment, + Constraints: constraints, + }) + default: + return fmt.Errorf("agent: unsupported key type %T", s) + } + + // if constraints are present then the message type needs to be changed. + if len(constraints) != 0 { + req[0] = agentAddIDConstrained + } + + signer, err := ssh.NewSignerFromKey(s) + if err != nil { + return err + } + if !bytes.Equal(cert.Key.Marshal(), signer.PublicKey().Marshal()) { + return errors.New("agent: signer and cert have different public key") + } + + resp, err := c.call(req) + if err != nil { + return err + } + if _, ok := resp.(*successAgentMsg); ok { + return nil + } + return errors.New("agent: failure") +} + +// Signers provides a callback for client authentication. +func (c *client) Signers() ([]ssh.Signer, error) { + keys, err := c.List() + if err != nil { + return nil, err + } + + var result []ssh.Signer + for _, k := range keys { + result = append(result, &agentKeyringSigner{c, k}) + } + return result, nil +} + +type agentKeyringSigner struct { + agent *client + pub ssh.PublicKey +} + +func (s *agentKeyringSigner) PublicKey() ssh.PublicKey { + return s.pub +} + +func (s *agentKeyringSigner) Sign(rand io.Reader, data []byte) (*ssh.Signature, error) { + // The agent has its own entropy source, so the rand argument is ignored. + return s.agent.Sign(s.pub, data) +} + +func (s *agentKeyringSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*ssh.Signature, error) { + if algorithm == "" || algorithm == underlyingAlgo(s.pub.Type()) { + return s.Sign(rand, data) + } + + var flags SignatureFlags + switch algorithm { + case ssh.KeyAlgoRSASHA256: + flags = SignatureFlagRsaSha256 + case ssh.KeyAlgoRSASHA512: + flags = SignatureFlagRsaSha512 + default: + return nil, fmt.Errorf("agent: unsupported algorithm %q", algorithm) + } + + return s.agent.SignWithFlags(s.pub, data, flags) +} + +var _ ssh.AlgorithmSigner = &agentKeyringSigner{} + +// certKeyAlgoNames is a mapping from known certificate algorithm names to the +// corresponding public key signature algorithm. +// +// This map must be kept in sync with the one in certs.go. +var certKeyAlgoNames = map[string]string{ + ssh.CertAlgoRSAv01: ssh.KeyAlgoRSA, + ssh.CertAlgoRSASHA256v01: ssh.KeyAlgoRSASHA256, + ssh.CertAlgoRSASHA512v01: ssh.KeyAlgoRSASHA512, + ssh.CertAlgoDSAv01: ssh.KeyAlgoDSA, + ssh.CertAlgoECDSA256v01: ssh.KeyAlgoECDSA256, + ssh.CertAlgoECDSA384v01: ssh.KeyAlgoECDSA384, + ssh.CertAlgoECDSA521v01: ssh.KeyAlgoECDSA521, + ssh.CertAlgoSKECDSA256v01: ssh.KeyAlgoSKECDSA256, + ssh.CertAlgoED25519v01: ssh.KeyAlgoED25519, + ssh.CertAlgoSKED25519v01: ssh.KeyAlgoSKED25519, +} + +// underlyingAlgo returns the signature algorithm associated with algo (which is +// an advertised or negotiated public key or host key algorithm). These are +// usually the same, except for certificate algorithms. +func underlyingAlgo(algo string) string { + if a, ok := certKeyAlgoNames[algo]; ok { + return a + } + return algo +} + +// Calls an extension method. It is up to the agent implementation as to whether or not +// any particular extension is supported and may always return an error. Because the +// type of the response is up to the implementation, this returns the bytes of the +// response and does not attempt any type of unmarshalling. +func (c *client) Extension(extensionType string, contents []byte) ([]byte, error) { + req := ssh.Marshal(extensionAgentMsg{ + ExtensionType: extensionType, + Contents: contents, + }) + buf, err := c.callRaw(req) + if err != nil { + return nil, err + } + if len(buf) == 0 { + return nil, errors.New("agent: failure; empty response") + } + // [PROTOCOL.agent] section 4.7 indicates that an SSH_AGENT_FAILURE message + // represents an agent that does not support the extension + if buf[0] == agentFailure { + return nil, ErrExtensionUnsupported + } + if buf[0] == agentExtensionFailure { + return nil, errors.New("agent: generic extension failure") + } + + return buf, nil +} diff --git a/pkg/proto/ssh/agent/forward.go b/pkg/proto/ssh/agent/forward.go new file mode 100644 index 0000000..8bf2bc0 --- /dev/null +++ b/pkg/proto/ssh/agent/forward.go @@ -0,0 +1,103 @@ +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package agent + +import ( + "errors" + "io" + "net" + "sync" + + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" +) + +// RequestAgentForwarding sets up agent forwarding for the session. +// ForwardToAgent or ForwardToRemote should be called to route +// the authentication requests. +func RequestAgentForwarding(session *ssh.Session) error { + ok, err := session.SendRequest("auth-agent-req@openssh.com", true, nil) + if err != nil { + return err + } + if !ok { + return errors.New("forwarding request denied") + } + return nil +} + +// ForwardToAgent routes authentication requests to the given keyring. +func ForwardToAgent(client *ssh.Client, keyring Agent) error { + channels := client.HandleChannelOpen(channelType) + if channels == nil { + return errors.New("agent: already have handler for " + channelType) + } + + go func() { + for ch := range channels { + channel, reqs, err := ch.Accept() + if err != nil { + continue + } + go ssh.DiscardRequests(reqs) + go func() { + ServeAgent(keyring, channel) + channel.Close() + }() + } + }() + return nil +} + +const channelType = "auth-agent@openssh.com" + +// ForwardToRemote routes authentication requests to the ssh-agent +// process serving on the given unix socket. +func ForwardToRemote(client *ssh.Client, addr string) error { + channels := client.HandleChannelOpen(channelType) + if channels == nil { + return errors.New("agent: already have handler for " + channelType) + } + conn, err := net.Dial("unix", addr) + if err != nil { + return err + } + conn.Close() + + go func() { + for ch := range channels { + channel, reqs, err := ch.Accept() + if err != nil { + continue + } + go ssh.DiscardRequests(reqs) + go forwardUnixSocket(channel, addr) + } + }() + return nil +} + +func forwardUnixSocket(channel ssh.Channel, addr string) { + conn, err := net.Dial("unix", addr) + if err != nil { + return + } + + var wg sync.WaitGroup + wg.Add(2) + go func() { + io.Copy(conn, channel) + conn.(*net.UnixConn).CloseWrite() + wg.Done() + }() + go func() { + io.Copy(channel, conn) + channel.CloseWrite() + wg.Done() + }() + + wg.Wait() + conn.Close() + channel.Close() +} diff --git a/pkg/proto/ssh/agent/keyring.go b/pkg/proto/ssh/agent/keyring.go new file mode 100644 index 0000000..dcd403f --- /dev/null +++ b/pkg/proto/ssh/agent/keyring.go @@ -0,0 +1,241 @@ +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package agent + +import ( + "bytes" + "crypto/rand" + "crypto/subtle" + "errors" + "fmt" + "sync" + "time" + + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" +) + +type privKey struct { + signer ssh.Signer + comment string + expire *time.Time +} + +type keyring struct { + mu sync.Mutex + keys []privKey + + locked bool + passphrase []byte +} + +var errLocked = errors.New("agent: locked") + +// NewKeyring returns an Agent that holds keys in memory. It is safe +// for concurrent use by multiple goroutines. +func NewKeyring() Agent { + return &keyring{} +} + +// RemoveAll removes all identities. +func (r *keyring) RemoveAll() error { + r.mu.Lock() + defer r.mu.Unlock() + if r.locked { + return errLocked + } + + r.keys = nil + return nil +} + +// removeLocked does the actual key removal. The caller must already be holding the +// keyring mutex. +func (r *keyring) removeLocked(want []byte) error { + found := false + for i := 0; i < len(r.keys); { + if bytes.Equal(r.keys[i].signer.PublicKey().Marshal(), want) { + found = true + r.keys[i] = r.keys[len(r.keys)-1] + r.keys = r.keys[:len(r.keys)-1] + continue + } else { + i++ + } + } + + if !found { + return errors.New("agent: key not found") + } + return nil +} + +// Remove removes all identities with the given public key. +func (r *keyring) Remove(key ssh.PublicKey) error { + r.mu.Lock() + defer r.mu.Unlock() + if r.locked { + return errLocked + } + + return r.removeLocked(key.Marshal()) +} + +// Lock locks the agent. Sign and Remove will fail, and List will return an empty list. +func (r *keyring) Lock(passphrase []byte) error { + r.mu.Lock() + defer r.mu.Unlock() + if r.locked { + return errLocked + } + + r.locked = true + r.passphrase = passphrase + return nil +} + +// Unlock undoes the effect of Lock +func (r *keyring) Unlock(passphrase []byte) error { + r.mu.Lock() + defer r.mu.Unlock() + if !r.locked { + return errors.New("agent: not locked") + } + if 1 != subtle.ConstantTimeCompare(passphrase, r.passphrase) { + return fmt.Errorf("agent: incorrect passphrase") + } + + r.locked = false + r.passphrase = nil + return nil +} + +// expireKeysLocked removes expired keys from the keyring. If a key was added +// with a lifetimesecs contraint and seconds >= lifetimesecs seconds have +// elapsed, it is removed. The caller *must* be holding the keyring mutex. +func (r *keyring) expireKeysLocked() { + for _, k := range r.keys { + if k.expire != nil && time.Now().After(*k.expire) { + r.removeLocked(k.signer.PublicKey().Marshal()) + } + } +} + +// List returns the identities known to the agent. +func (r *keyring) List() ([]*Key, error) { + r.mu.Lock() + defer r.mu.Unlock() + if r.locked { + // section 2.7: locked agents return empty. + return nil, nil + } + + r.expireKeysLocked() + var ids []*Key + for _, k := range r.keys { + pub := k.signer.PublicKey() + ids = append(ids, &Key{ + Format: pub.Type(), + Blob: pub.Marshal(), + Comment: k.comment}) + } + return ids, nil +} + +// Insert adds a private key to the keyring. If a certificate +// is given, that certificate is added as public key. Note that +// any constraints given are ignored. +func (r *keyring) Add(key AddedKey) error { + r.mu.Lock() + defer r.mu.Unlock() + if r.locked { + return errLocked + } + signer, err := ssh.NewSignerFromKey(key.PrivateKey) + + if err != nil { + return err + } + + if cert := key.Certificate; cert != nil { + signer, err = ssh.NewCertSigner(cert, signer) + if err != nil { + return err + } + } + + p := privKey{ + signer: signer, + comment: key.Comment, + } + + if key.LifetimeSecs > 0 { + t := time.Now().Add(time.Duration(key.LifetimeSecs) * time.Second) + p.expire = &t + } + + r.keys = append(r.keys, p) + + return nil +} + +// Sign returns a signature for the data. +func (r *keyring) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) { + return r.SignWithFlags(key, data, 0) +} + +func (r *keyring) SignWithFlags(key ssh.PublicKey, data []byte, flags SignatureFlags) (*ssh.Signature, error) { + r.mu.Lock() + defer r.mu.Unlock() + if r.locked { + return nil, errLocked + } + + r.expireKeysLocked() + wanted := key.Marshal() + for _, k := range r.keys { + if bytes.Equal(k.signer.PublicKey().Marshal(), wanted) { + if flags == 0 { + return k.signer.Sign(rand.Reader, data) + } else { + if algorithmSigner, ok := k.signer.(ssh.AlgorithmSigner); !ok { + return nil, fmt.Errorf("agent: signature does not support non-default signature algorithm: %T", k.signer) + } else { + var algorithm string + switch flags { + case SignatureFlagRsaSha256: + algorithm = ssh.KeyAlgoRSASHA256 + case SignatureFlagRsaSha512: + algorithm = ssh.KeyAlgoRSASHA512 + default: + return nil, fmt.Errorf("agent: unsupported signature flags: %d", flags) + } + return algorithmSigner.SignWithAlgorithm(rand.Reader, data, algorithm) + } + } + } + } + return nil, errors.New("not found") +} + +// Signers returns signers for all the known keys. +func (r *keyring) Signers() ([]ssh.Signer, error) { + r.mu.Lock() + defer r.mu.Unlock() + if r.locked { + return nil, errLocked + } + + r.expireKeysLocked() + s := make([]ssh.Signer, 0, len(r.keys)) + for _, k := range r.keys { + s = append(s, k.signer) + } + return s, nil +} + +// The keyring does not support any extensions +func (r *keyring) Extension(extensionType string, contents []byte) ([]byte, error) { + return nil, ErrExtensionUnsupported +} diff --git a/pkg/proto/ssh/agent/server.go b/pkg/proto/ssh/agent/server.go new file mode 100644 index 0000000..ae83d29 --- /dev/null +++ b/pkg/proto/ssh/agent/server.go @@ -0,0 +1,570 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package agent + +import ( + "crypto/dsa" + "crypto/ecdsa" + "crypto/ed25519" + "crypto/elliptic" + "crypto/rsa" + "encoding/binary" + "errors" + "fmt" + "io" + "log" + "math/big" + + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" +) + +// server wraps an Agent and uses it to implement the agent side of +// the SSH-agent, wire protocol. +type server struct { + agent Agent +} + +func (s *server) processRequestBytes(reqData []byte) []byte { + rep, err := s.processRequest(reqData) + if err != nil { + if err != errLocked { + // TODO(hanwen): provide better logging interface? + log.Printf("agent %d: %v", reqData[0], err) + } + return []byte{agentFailure} + } + + if err == nil && rep == nil { + return []byte{agentSuccess} + } + + return ssh.Marshal(rep) +} + +func marshalKey(k *Key) []byte { + var record struct { + Blob []byte + Comment string + } + record.Blob = k.Marshal() + record.Comment = k.Comment + + return ssh.Marshal(&record) +} + +// See [PROTOCOL.agent], section 2.5.1. +const agentV1IdentitiesAnswer = 2 + +type agentV1IdentityMsg struct { + Numkeys uint32 `sshtype:"2"` +} + +type agentRemoveIdentityMsg struct { + KeyBlob []byte `sshtype:"18"` +} + +type agentLockMsg struct { + Passphrase []byte `sshtype:"22"` +} + +type agentUnlockMsg struct { + Passphrase []byte `sshtype:"23"` +} + +func (s *server) processRequest(data []byte) (interface{}, error) { + switch data[0] { + case agentRequestV1Identities: + return &agentV1IdentityMsg{0}, nil + + case agentRemoveAllV1Identities: + return nil, nil + + case agentRemoveIdentity: + var req agentRemoveIdentityMsg + if err := ssh.Unmarshal(data, &req); err != nil { + return nil, err + } + + var wk wireKey + if err := ssh.Unmarshal(req.KeyBlob, &wk); err != nil { + return nil, err + } + + return nil, s.agent.Remove(&Key{Format: wk.Format, Blob: req.KeyBlob}) + + case agentRemoveAllIdentities: + return nil, s.agent.RemoveAll() + + case agentLock: + var req agentLockMsg + if err := ssh.Unmarshal(data, &req); err != nil { + return nil, err + } + + return nil, s.agent.Lock(req.Passphrase) + + case agentUnlock: + var req agentUnlockMsg + if err := ssh.Unmarshal(data, &req); err != nil { + return nil, err + } + return nil, s.agent.Unlock(req.Passphrase) + + case agentSignRequest: + var req signRequestAgentMsg + if err := ssh.Unmarshal(data, &req); err != nil { + return nil, err + } + + var wk wireKey + if err := ssh.Unmarshal(req.KeyBlob, &wk); err != nil { + return nil, err + } + + k := &Key{ + Format: wk.Format, + Blob: req.KeyBlob, + } + + var sig *ssh.Signature + var err error + if extendedAgent, ok := s.agent.(ExtendedAgent); ok { + sig, err = extendedAgent.SignWithFlags(k, req.Data, SignatureFlags(req.Flags)) + } else { + sig, err = s.agent.Sign(k, req.Data) + } + + if err != nil { + return nil, err + } + return &signResponseAgentMsg{SigBlob: ssh.Marshal(sig)}, nil + + case agentRequestIdentities: + keys, err := s.agent.List() + if err != nil { + return nil, err + } + + rep := identitiesAnswerAgentMsg{ + NumKeys: uint32(len(keys)), + } + for _, k := range keys { + rep.Keys = append(rep.Keys, marshalKey(k)...) + } + return rep, nil + + case agentAddIDConstrained, agentAddIdentity: + return nil, s.insertIdentity(data) + + case agentExtension: + // Return a stub object where the whole contents of the response gets marshaled. + var responseStub struct { + Rest []byte `ssh:"rest"` + } + + if extendedAgent, ok := s.agent.(ExtendedAgent); !ok { + // If this agent doesn't implement extensions, [PROTOCOL.agent] section 4.7 + // requires that we return a standard SSH_AGENT_FAILURE message. + responseStub.Rest = []byte{agentFailure} + } else { + var req extensionAgentMsg + if err := ssh.Unmarshal(data, &req); err != nil { + return nil, err + } + res, err := extendedAgent.Extension(req.ExtensionType, req.Contents) + if err != nil { + // If agent extensions are unsupported, return a standard SSH_AGENT_FAILURE + // message as required by [PROTOCOL.agent] section 4.7. + if err == ErrExtensionUnsupported { + responseStub.Rest = []byte{agentFailure} + } else { + // As the result of any other error processing an extension request, + // [PROTOCOL.agent] section 4.7 requires that we return a + // SSH_AGENT_EXTENSION_FAILURE code. + responseStub.Rest = []byte{agentExtensionFailure} + } + } else { + if len(res) == 0 { + return nil, nil + } + responseStub.Rest = res + } + } + + return responseStub, nil + } + + return nil, fmt.Errorf("unknown opcode %d", data[0]) +} + +func parseConstraints(constraints []byte) (lifetimeSecs uint32, confirmBeforeUse bool, extensions []ConstraintExtension, err error) { + for len(constraints) != 0 { + switch constraints[0] { + case agentConstrainLifetime: + lifetimeSecs = binary.BigEndian.Uint32(constraints[1:5]) + constraints = constraints[5:] + case agentConstrainConfirm: + confirmBeforeUse = true + constraints = constraints[1:] + case agentConstrainExtension, agentConstrainExtensionV00: + var msg constrainExtensionAgentMsg + if err = ssh.Unmarshal(constraints, &msg); err != nil { + return 0, false, nil, err + } + extensions = append(extensions, ConstraintExtension{ + ExtensionName: msg.ExtensionName, + ExtensionDetails: msg.ExtensionDetails, + }) + constraints = msg.Rest + default: + return 0, false, nil, fmt.Errorf("unknown constraint type: %d", constraints[0]) + } + } + return +} + +func setConstraints(key *AddedKey, constraintBytes []byte) error { + lifetimeSecs, confirmBeforeUse, constraintExtensions, err := parseConstraints(constraintBytes) + if err != nil { + return err + } + + key.LifetimeSecs = lifetimeSecs + key.ConfirmBeforeUse = confirmBeforeUse + key.ConstraintExtensions = constraintExtensions + return nil +} + +func parseRSAKey(req []byte) (*AddedKey, error) { + var k rsaKeyMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + if k.E.BitLen() > 30 { + return nil, errors.New("agent: RSA public exponent too large") + } + priv := &rsa.PrivateKey{ + PublicKey: rsa.PublicKey{ + E: int(k.E.Int64()), + N: k.N, + }, + D: k.D, + Primes: []*big.Int{k.P, k.Q}, + } + priv.Precompute() + + addedKey := &AddedKey{PrivateKey: priv, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func parseEd25519Key(req []byte) (*AddedKey, error) { + var k ed25519KeyMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + priv := ed25519.PrivateKey(k.Priv) + + addedKey := &AddedKey{PrivateKey: &priv, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func parseDSAKey(req []byte) (*AddedKey, error) { + var k dsaKeyMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + priv := &dsa.PrivateKey{ + PublicKey: dsa.PublicKey{ + Parameters: dsa.Parameters{ + P: k.P, + Q: k.Q, + G: k.G, + }, + Y: k.Y, + }, + X: k.X, + } + + addedKey := &AddedKey{PrivateKey: priv, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func unmarshalECDSA(curveName string, keyBytes []byte, privScalar *big.Int) (priv *ecdsa.PrivateKey, err error) { + priv = &ecdsa.PrivateKey{ + D: privScalar, + } + + switch curveName { + case "nistp256": + priv.Curve = elliptic.P256() + case "nistp384": + priv.Curve = elliptic.P384() + case "nistp521": + priv.Curve = elliptic.P521() + default: + return nil, fmt.Errorf("agent: unknown curve %q", curveName) + } + + priv.X, priv.Y = elliptic.Unmarshal(priv.Curve, keyBytes) + if priv.X == nil || priv.Y == nil { + return nil, errors.New("agent: point not on curve") + } + + return priv, nil +} + +func parseEd25519Cert(req []byte) (*AddedKey, error) { + var k ed25519CertMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + pubKey, err := ssh.ParsePublicKey(k.CertBytes) + if err != nil { + return nil, err + } + priv := ed25519.PrivateKey(k.Priv) + cert, ok := pubKey.(*ssh.Certificate) + if !ok { + return nil, errors.New("agent: bad ED25519 certificate") + } + + addedKey := &AddedKey{PrivateKey: &priv, Certificate: cert, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func parseECDSAKey(req []byte) (*AddedKey, error) { + var k ecdsaKeyMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + + priv, err := unmarshalECDSA(k.Curve, k.KeyBytes, k.D) + if err != nil { + return nil, err + } + + addedKey := &AddedKey{PrivateKey: priv, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func parseRSACert(req []byte) (*AddedKey, error) { + var k rsaCertMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + + pubKey, err := ssh.ParsePublicKey(k.CertBytes) + if err != nil { + return nil, err + } + + cert, ok := pubKey.(*ssh.Certificate) + if !ok { + return nil, errors.New("agent: bad RSA certificate") + } + + // An RSA publickey as marshaled by rsaPublicKey.Marshal() in keys.go + var rsaPub struct { + Name string + E *big.Int + N *big.Int + } + if err := ssh.Unmarshal(cert.Key.Marshal(), &rsaPub); err != nil { + return nil, fmt.Errorf("agent: Unmarshal failed to parse public key: %v", err) + } + + if rsaPub.E.BitLen() > 30 { + return nil, errors.New("agent: RSA public exponent too large") + } + + priv := rsa.PrivateKey{ + PublicKey: rsa.PublicKey{ + E: int(rsaPub.E.Int64()), + N: rsaPub.N, + }, + D: k.D, + Primes: []*big.Int{k.Q, k.P}, + } + priv.Precompute() + + addedKey := &AddedKey{PrivateKey: &priv, Certificate: cert, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func parseDSACert(req []byte) (*AddedKey, error) { + var k dsaCertMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + pubKey, err := ssh.ParsePublicKey(k.CertBytes) + if err != nil { + return nil, err + } + cert, ok := pubKey.(*ssh.Certificate) + if !ok { + return nil, errors.New("agent: bad DSA certificate") + } + + // A DSA publickey as marshaled by dsaPublicKey.Marshal() in keys.go + var w struct { + Name string + P, Q, G, Y *big.Int + } + if err := ssh.Unmarshal(cert.Key.Marshal(), &w); err != nil { + return nil, fmt.Errorf("agent: Unmarshal failed to parse public key: %v", err) + } + + priv := &dsa.PrivateKey{ + PublicKey: dsa.PublicKey{ + Parameters: dsa.Parameters{ + P: w.P, + Q: w.Q, + G: w.G, + }, + Y: w.Y, + }, + X: k.X, + } + + addedKey := &AddedKey{PrivateKey: priv, Certificate: cert, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func parseECDSACert(req []byte) (*AddedKey, error) { + var k ecdsaCertMsg + if err := ssh.Unmarshal(req, &k); err != nil { + return nil, err + } + + pubKey, err := ssh.ParsePublicKey(k.CertBytes) + if err != nil { + return nil, err + } + cert, ok := pubKey.(*ssh.Certificate) + if !ok { + return nil, errors.New("agent: bad ECDSA certificate") + } + + // An ECDSA publickey as marshaled by ecdsaPublicKey.Marshal() in keys.go + var ecdsaPub struct { + Name string + ID string + Key []byte + } + if err := ssh.Unmarshal(cert.Key.Marshal(), &ecdsaPub); err != nil { + return nil, err + } + + priv, err := unmarshalECDSA(ecdsaPub.ID, ecdsaPub.Key, k.D) + if err != nil { + return nil, err + } + + addedKey := &AddedKey{PrivateKey: priv, Certificate: cert, Comment: k.Comments} + if err := setConstraints(addedKey, k.Constraints); err != nil { + return nil, err + } + return addedKey, nil +} + +func (s *server) insertIdentity(req []byte) error { + var record struct { + Type string `sshtype:"17|25"` + Rest []byte `ssh:"rest"` + } + + if err := ssh.Unmarshal(req, &record); err != nil { + return err + } + + var addedKey *AddedKey + var err error + + switch record.Type { + case ssh.KeyAlgoRSA: + addedKey, err = parseRSAKey(req) + case ssh.KeyAlgoDSA: + addedKey, err = parseDSAKey(req) + case ssh.KeyAlgoECDSA256, ssh.KeyAlgoECDSA384, ssh.KeyAlgoECDSA521: + addedKey, err = parseECDSAKey(req) + case ssh.KeyAlgoED25519: + addedKey, err = parseEd25519Key(req) + case ssh.CertAlgoRSAv01: + addedKey, err = parseRSACert(req) + case ssh.CertAlgoDSAv01: + addedKey, err = parseDSACert(req) + case ssh.CertAlgoECDSA256v01, ssh.CertAlgoECDSA384v01, ssh.CertAlgoECDSA521v01: + addedKey, err = parseECDSACert(req) + case ssh.CertAlgoED25519v01: + addedKey, err = parseEd25519Cert(req) + default: + return fmt.Errorf("agent: not implemented: %q", record.Type) + } + + if err != nil { + return err + } + return s.agent.Add(*addedKey) +} + +// ServeAgent serves the agent protocol on the given connection. It +// returns when an I/O error occurs. +func ServeAgent(agent Agent, c io.ReadWriter) error { + s := &server{agent} + + var length [4]byte + for { + if _, err := io.ReadFull(c, length[:]); err != nil { + return err + } + l := binary.BigEndian.Uint32(length[:]) + if l == 0 { + return fmt.Errorf("agent: request size is 0") + } + if l > maxAgentResponseBytes { + // We also cap requests. + return fmt.Errorf("agent: request too large: %d", l) + } + + req := make([]byte, l) + if _, err := io.ReadFull(c, req); err != nil { + return err + } + + repData := s.processRequestBytes(req) + if len(repData) > maxAgentResponseBytes { + return fmt.Errorf("agent: reply too large: %d bytes", len(repData)) + } + + binary.BigEndian.PutUint32(length[:], uint32(len(repData))) + if _, err := c.Write(length[:]); err != nil { + return err + } + if _, err := c.Write(repData); err != nil { + return err + } + } +} diff --git a/pkg/proto/ssh/buffer.go b/pkg/proto/ssh/buffer.go new file mode 100644 index 0000000..1ab07d0 --- /dev/null +++ b/pkg/proto/ssh/buffer.go @@ -0,0 +1,97 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "io" + "sync" +) + +// buffer provides a linked list buffer for data exchange +// between producer and consumer. Theoretically the buffer is +// of unlimited capacity as it does no allocation of its own. +type buffer struct { + // protects concurrent access to head, tail and closed + *sync.Cond + + head *element // the buffer that will be read first + tail *element // the buffer that will be read last + + closed bool +} + +// An element represents a single link in a linked list. +type element struct { + buf []byte + next *element +} + +// newBuffer returns an empty buffer that is not closed. +func newBuffer() *buffer { + e := new(element) + b := &buffer{ + Cond: newCond(), + head: e, + tail: e, + } + return b +} + +// write makes buf available for Read to receive. +// buf must not be modified after the call to write. +func (b *buffer) write(buf []byte) { + b.Cond.L.Lock() + e := &element{buf: buf} + b.tail.next = e + b.tail = e + b.Cond.Signal() + b.Cond.L.Unlock() +} + +// eof closes the buffer. Reads from the buffer once all +// the data has been consumed will receive io.EOF. +func (b *buffer) eof() { + b.Cond.L.Lock() + b.closed = true + b.Cond.Signal() + b.Cond.L.Unlock() +} + +// Read reads data from the internal buffer in buf. Reads will block +// if no data is available, or until the buffer is closed. +func (b *buffer) Read(buf []byte) (n int, err error) { + b.Cond.L.Lock() + defer b.Cond.L.Unlock() + + for len(buf) > 0 { + // if there is data in b.head, copy it + if len(b.head.buf) > 0 { + r := copy(buf, b.head.buf) + buf, b.head.buf = buf[r:], b.head.buf[r:] + n += r + continue + } + // if there is a next buffer, make it the head + if len(b.head.buf) == 0 && b.head != b.tail { + b.head = b.head.next + continue + } + + // if at least one byte has been copied, return + if n > 0 { + break + } + + // if nothing was read, and there is nothing outstanding + // check to see if the buffer is closed. + if b.closed { + err = io.EOF + break + } + // out of buffers, wait for producer + b.Cond.Wait() + } + return +} diff --git a/pkg/proto/ssh/certs.go b/pkg/proto/ssh/certs.go new file mode 100644 index 0000000..27d0e14 --- /dev/null +++ b/pkg/proto/ssh/certs.go @@ -0,0 +1,611 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "bytes" + "errors" + "fmt" + "io" + "net" + "sort" + "time" +) + +// Certificate algorithm names from [PROTOCOL.certkeys]. These values can appear +// in Certificate.Type, PublicKey.Type, and ClientConfig.HostKeyAlgorithms. +// Unlike key algorithm names, these are not passed to AlgorithmSigner nor +// returned by MultiAlgorithmSigner and don't appear in the Signature.Format +// field. +const ( + CertAlgoRSAv01 = "ssh-rsa-cert-v01@openssh.com" + CertAlgoDSAv01 = "ssh-dss-cert-v01@openssh.com" + CertAlgoECDSA256v01 = "ecdsa-sha2-nistp256-cert-v01@openssh.com" + CertAlgoECDSA384v01 = "ecdsa-sha2-nistp384-cert-v01@openssh.com" + CertAlgoECDSA521v01 = "ecdsa-sha2-nistp521-cert-v01@openssh.com" + CertAlgoSKECDSA256v01 = "sk-ecdsa-sha2-nistp256-cert-v01@openssh.com" + CertAlgoED25519v01 = "ssh-ed25519-cert-v01@openssh.com" + CertAlgoSKED25519v01 = "sk-ssh-ed25519-cert-v01@openssh.com" + + // CertAlgoRSASHA256v01 and CertAlgoRSASHA512v01 can't appear as a + // Certificate.Type (or PublicKey.Type), but only in + // ClientConfig.HostKeyAlgorithms. + CertAlgoRSASHA256v01 = "rsa-sha2-256-cert-v01@openssh.com" + CertAlgoRSASHA512v01 = "rsa-sha2-512-cert-v01@openssh.com" +) + +const ( + // Deprecated: use CertAlgoRSAv01. + CertSigAlgoRSAv01 = CertAlgoRSAv01 + // Deprecated: use CertAlgoRSASHA256v01. + CertSigAlgoRSASHA2256v01 = CertAlgoRSASHA256v01 + // Deprecated: use CertAlgoRSASHA512v01. + CertSigAlgoRSASHA2512v01 = CertAlgoRSASHA512v01 +) + +// Certificate types distinguish between host and user +// certificates. The values can be set in the CertType field of +// Certificate. +const ( + UserCert = 1 + HostCert = 2 +) + +// Signature represents a cryptographic signature. +type Signature struct { + Format string + Blob []byte + Rest []byte `ssh:"rest"` +} + +// CertTimeInfinity can be used for OpenSSHCertV01.ValidBefore to indicate that +// a certificate does not expire. +const CertTimeInfinity = 1<<64 - 1 + +// An Certificate represents an OpenSSH certificate as defined in +// [PROTOCOL.certkeys]?rev=1.8. The Certificate type implements the +// PublicKey interface, so it can be unmarshaled using +// ParsePublicKey. +type Certificate struct { + Nonce []byte + Key PublicKey + Serial uint64 + CertType uint32 + KeyId string + ValidPrincipals []string + ValidAfter uint64 + ValidBefore uint64 + Permissions + Reserved []byte + SignatureKey PublicKey + Signature *Signature +} + +// genericCertData holds the key-independent part of the certificate data. +// Overall, certificates contain an nonce, public key fields and +// key-independent fields. +type genericCertData struct { + Serial uint64 + CertType uint32 + KeyId string + ValidPrincipals []byte + ValidAfter uint64 + ValidBefore uint64 + CriticalOptions []byte + Extensions []byte + Reserved []byte + SignatureKey []byte + Signature []byte +} + +func marshalStringList(namelist []string) []byte { + var to []byte + for _, name := range namelist { + s := struct{ N string }{name} + to = append(to, Marshal(&s)...) + } + return to +} + +type optionsTuple struct { + Key string + Value []byte +} + +type optionsTupleValue struct { + Value string +} + +// serialize a map of critical options or extensions +// issue #10569 - per [PROTOCOL.certkeys] and SSH implementation, +// we need two length prefixes for a non-empty string value +func marshalTuples(tups map[string]string) []byte { + keys := make([]string, 0, len(tups)) + for key := range tups { + keys = append(keys, key) + } + sort.Strings(keys) + + var ret []byte + for _, key := range keys { + s := optionsTuple{Key: key} + if value := tups[key]; len(value) > 0 { + s.Value = Marshal(&optionsTupleValue{value}) + } + ret = append(ret, Marshal(&s)...) + } + return ret +} + +// issue #10569 - per [PROTOCOL.certkeys] and SSH implementation, +// we need two length prefixes for a non-empty option value +func parseTuples(in []byte) (map[string]string, error) { + tups := map[string]string{} + var lastKey string + var haveLastKey bool + + for len(in) > 0 { + var key, val, extra []byte + var ok bool + + if key, in, ok = parseString(in); !ok { + return nil, errShortRead + } + keyStr := string(key) + // according to [PROTOCOL.certkeys], the names must be in + // lexical order. + if haveLastKey && keyStr <= lastKey { + return nil, fmt.Errorf("ssh: certificate options are not in lexical order") + } + lastKey, haveLastKey = keyStr, true + // the next field is a data field, which if non-empty has a string embedded + if val, in, ok = parseString(in); !ok { + return nil, errShortRead + } + if len(val) > 0 { + val, extra, ok = parseString(val) + if !ok { + return nil, errShortRead + } + if len(extra) > 0 { + return nil, fmt.Errorf("ssh: unexpected trailing data after certificate option value") + } + tups[keyStr] = string(val) + } else { + tups[keyStr] = "" + } + } + return tups, nil +} + +func parseCert(in []byte, privAlgo string) (*Certificate, error) { + nonce, rest, ok := parseString(in) + if !ok { + return nil, errShortRead + } + + key, rest, err := parsePubKey(rest, privAlgo) + if err != nil { + return nil, err + } + + var g genericCertData + if err := Unmarshal(rest, &g); err != nil { + return nil, err + } + + c := &Certificate{ + Nonce: nonce, + Key: key, + Serial: g.Serial, + CertType: g.CertType, + KeyId: g.KeyId, + ValidAfter: g.ValidAfter, + ValidBefore: g.ValidBefore, + } + + for principals := g.ValidPrincipals; len(principals) > 0; { + principal, rest, ok := parseString(principals) + if !ok { + return nil, errShortRead + } + c.ValidPrincipals = append(c.ValidPrincipals, string(principal)) + principals = rest + } + + c.CriticalOptions, err = parseTuples(g.CriticalOptions) + if err != nil { + return nil, err + } + c.Extensions, err = parseTuples(g.Extensions) + if err != nil { + return nil, err + } + c.Reserved = g.Reserved + k, err := ParsePublicKey(g.SignatureKey) + if err != nil { + return nil, err + } + + c.SignatureKey = k + c.Signature, rest, ok = parseSignatureBody(g.Signature) + if !ok || len(rest) > 0 { + return nil, errors.New("ssh: signature parse error") + } + + return c, nil +} + +type openSSHCertSigner struct { + pub *Certificate + signer Signer +} + +type algorithmOpenSSHCertSigner struct { + *openSSHCertSigner + algorithmSigner AlgorithmSigner +} + +// NewCertSigner returns a Signer that signs with the given Certificate, whose +// private key is held by signer. It returns an error if the public key in cert +// doesn't match the key used by signer. +func NewCertSigner(cert *Certificate, signer Signer) (Signer, error) { + if !bytes.Equal(cert.Key.Marshal(), signer.PublicKey().Marshal()) { + return nil, errors.New("ssh: signer and cert have different public key") + } + + switch s := signer.(type) { + case MultiAlgorithmSigner: + return &multiAlgorithmSigner{ + AlgorithmSigner: &algorithmOpenSSHCertSigner{ + &openSSHCertSigner{cert, signer}, s}, + supportedAlgorithms: s.Algorithms(), + }, nil + case AlgorithmSigner: + return &algorithmOpenSSHCertSigner{ + &openSSHCertSigner{cert, signer}, s}, nil + default: + return &openSSHCertSigner{cert, signer}, nil + } +} + +func (s *openSSHCertSigner) Sign(rand io.Reader, data []byte) (*Signature, error) { + return s.signer.Sign(rand, data) +} + +func (s *openSSHCertSigner) PublicKey() PublicKey { + return s.pub +} + +func (s *algorithmOpenSSHCertSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { + return s.algorithmSigner.SignWithAlgorithm(rand, data, algorithm) +} + +const sourceAddressCriticalOption = "source-address" + +// CertChecker does the work of verifying a certificate. Its methods +// can be plugged into ClientConfig.HostKeyCallback and +// ServerConfig.PublicKeyCallback. For the CertChecker to work, +// minimally, the IsAuthority callback should be set. +type CertChecker struct { + // SupportedCriticalOptions lists the CriticalOptions that the + // server application layer understands. These are only used + // for user certificates. + SupportedCriticalOptions []string + + // IsUserAuthority should return true if the key is recognized as an + // authority for the given user certificate. This allows for + // certificates to be signed by other certificates. This must be set + // if this CertChecker will be checking user certificates. + IsUserAuthority func(auth PublicKey) bool + + // IsHostAuthority should report whether the key is recognized as + // an authority for this host. This allows for certificates to be + // signed by other keys, and for those other keys to only be valid + // signers for particular hostnames. This must be set if this + // CertChecker will be checking host certificates. + IsHostAuthority func(auth PublicKey, address string) bool + + // Clock is used for verifying time stamps. If nil, time.Now + // is used. + Clock func() time.Time + + // UserKeyFallback is called when CertChecker.Authenticate encounters a + // public key that is not a certificate. It must implement validation + // of user keys or else, if nil, all such keys are rejected. + UserKeyFallback func(conn ConnMetadata, key PublicKey) (*Permissions, error) + + // HostKeyFallback is called when CertChecker.CheckHostKey encounters a + // public key that is not a certificate. It must implement host key + // validation or else, if nil, all such keys are rejected. + HostKeyFallback HostKeyCallback + + // IsRevoked is called for each certificate so that revocation checking + // can be implemented. It should return true if the given certificate + // is revoked and false otherwise. If nil, no certificates are + // considered to have been revoked. + IsRevoked func(cert *Certificate) bool +} + +// CheckHostKey checks a host key certificate. This method can be +// plugged into ClientConfig.HostKeyCallback. +func (c *CertChecker) CheckHostKey(addr string, remote net.Addr, key PublicKey) error { + cert, ok := key.(*Certificate) + if !ok { + if c.HostKeyFallback != nil { + return c.HostKeyFallback(addr, remote, key) + } + return errors.New("ssh: non-certificate host key") + } + if cert.CertType != HostCert { + return fmt.Errorf("ssh: certificate presented as a host key has type %d", cert.CertType) + } + if !c.IsHostAuthority(cert.SignatureKey, addr) { + return fmt.Errorf("ssh: no authorities for hostname: %v", addr) + } + + hostname, _, err := net.SplitHostPort(addr) + if err != nil { + return err + } + + // Pass hostname only as principal for host certificates (consistent with OpenSSH) + return c.CheckCert(hostname, cert) +} + +// Authenticate checks a user certificate. Authenticate can be used as +// a value for ServerConfig.PublicKeyCallback. +func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permissions, error) { + cert, ok := pubKey.(*Certificate) + if !ok { + if c.UserKeyFallback != nil { + return c.UserKeyFallback(conn, pubKey) + } + return nil, errors.New("ssh: normal key pairs not accepted") + } + + if cert.CertType != UserCert { + return nil, fmt.Errorf("ssh: cert has type %d", cert.CertType) + } + if !c.IsUserAuthority(cert.SignatureKey) { + return nil, fmt.Errorf("ssh: certificate signed by unrecognized authority") + } + + if err := c.CheckCert(conn.User(), cert); err != nil { + return nil, err + } + + return &cert.Permissions, nil +} + +// CheckCert checks CriticalOptions, ValidPrincipals, revocation, timestamp and +// the signature of the certificate. +func (c *CertChecker) CheckCert(principal string, cert *Certificate) error { + if c.IsRevoked != nil && c.IsRevoked(cert) { + return fmt.Errorf("ssh: certificate serial %d revoked", cert.Serial) + } + + for opt := range cert.CriticalOptions { + // sourceAddressCriticalOption will be enforced by + // serverAuthenticate + if opt == sourceAddressCriticalOption { + continue + } + + found := false + for _, supp := range c.SupportedCriticalOptions { + if supp == opt { + found = true + break + } + } + if !found { + return fmt.Errorf("ssh: unsupported critical option %q in certificate", opt) + } + } + + if len(cert.ValidPrincipals) > 0 { + // By default, certs are valid for all users/hosts. + found := false + for _, p := range cert.ValidPrincipals { + if p == principal { + found = true + break + } + } + if !found { + return fmt.Errorf("ssh: principal %q not in the set of valid principals for given certificate: %q", principal, cert.ValidPrincipals) + } + } + + clock := c.Clock + if clock == nil { + clock = time.Now + } + + unixNow := clock().Unix() + if after := int64(cert.ValidAfter); after < 0 || unixNow < int64(cert.ValidAfter) { + return fmt.Errorf("ssh: cert is not yet valid") + } + if before := int64(cert.ValidBefore); cert.ValidBefore != uint64(CertTimeInfinity) && (unixNow >= before || before < 0) { + return fmt.Errorf("ssh: cert has expired") + } + if err := cert.SignatureKey.Verify(cert.bytesForSigning(), cert.Signature); err != nil { + return fmt.Errorf("ssh: certificate signature does not verify") + } + + return nil +} + +// SignCert signs the certificate with an authority, setting the Nonce, +// SignatureKey, and Signature fields. If the authority implements the +// MultiAlgorithmSigner interface the first algorithm in the list is used. This +// is useful if you want to sign with a specific algorithm. +func (c *Certificate) SignCert(rand io.Reader, authority Signer) error { + c.Nonce = make([]byte, 32) + if _, err := io.ReadFull(rand, c.Nonce); err != nil { + return err + } + c.SignatureKey = authority.PublicKey() + + if v, ok := authority.(MultiAlgorithmSigner); ok { + if len(v.Algorithms()) == 0 { + return errors.New("the provided authority has no signature algorithm") + } + // Use the first algorithm in the list. + sig, err := v.SignWithAlgorithm(rand, c.bytesForSigning(), v.Algorithms()[0]) + if err != nil { + return err + } + c.Signature = sig + return nil + } else if v, ok := authority.(AlgorithmSigner); ok && v.PublicKey().Type() == KeyAlgoRSA { + // Default to KeyAlgoRSASHA512 for ssh-rsa signers. + // TODO: consider using KeyAlgoRSASHA256 as default. + sig, err := v.SignWithAlgorithm(rand, c.bytesForSigning(), KeyAlgoRSASHA512) + if err != nil { + return err + } + c.Signature = sig + return nil + } + + sig, err := authority.Sign(rand, c.bytesForSigning()) + if err != nil { + return err + } + c.Signature = sig + return nil +} + +// certKeyAlgoNames is a mapping from known certificate algorithm names to the +// corresponding public key signature algorithm. +// +// This map must be kept in sync with the one in agent/client.go. +var certKeyAlgoNames = map[string]string{ + CertAlgoRSAv01: KeyAlgoRSA, + CertAlgoRSASHA256v01: KeyAlgoRSASHA256, + CertAlgoRSASHA512v01: KeyAlgoRSASHA512, + CertAlgoDSAv01: KeyAlgoDSA, + CertAlgoECDSA256v01: KeyAlgoECDSA256, + CertAlgoECDSA384v01: KeyAlgoECDSA384, + CertAlgoECDSA521v01: KeyAlgoECDSA521, + CertAlgoSKECDSA256v01: KeyAlgoSKECDSA256, + CertAlgoED25519v01: KeyAlgoED25519, + CertAlgoSKED25519v01: KeyAlgoSKED25519, +} + +// underlyingAlgo returns the signature algorithm associated with algo (which is +// an advertised or negotiated public key or host key algorithm). These are +// usually the same, except for certificate algorithms. +func underlyingAlgo(algo string) string { + if a, ok := certKeyAlgoNames[algo]; ok { + return a + } + return algo +} + +// certificateAlgo returns the certificate algorithms that uses the provided +// underlying signature algorithm. +func certificateAlgo(algo string) (certAlgo string, ok bool) { + for certName, algoName := range certKeyAlgoNames { + if algoName == algo { + return certName, true + } + } + return "", false +} + +func (cert *Certificate) bytesForSigning() []byte { + c2 := *cert + c2.Signature = nil + out := c2.Marshal() + // Drop trailing signature length. + return out[:len(out)-4] +} + +// Marshal serializes c into OpenSSH's wire format. It is part of the +// PublicKey interface. +func (c *Certificate) Marshal() []byte { + generic := genericCertData{ + Serial: c.Serial, + CertType: c.CertType, + KeyId: c.KeyId, + ValidPrincipals: marshalStringList(c.ValidPrincipals), + ValidAfter: uint64(c.ValidAfter), + ValidBefore: uint64(c.ValidBefore), + CriticalOptions: marshalTuples(c.CriticalOptions), + Extensions: marshalTuples(c.Extensions), + Reserved: c.Reserved, + SignatureKey: c.SignatureKey.Marshal(), + } + if c.Signature != nil { + generic.Signature = Marshal(c.Signature) + } + genericBytes := Marshal(&generic) + keyBytes := c.Key.Marshal() + _, keyBytes, _ = parseString(keyBytes) + prefix := Marshal(&struct { + Name string + Nonce []byte + Key []byte `ssh:"rest"` + }{c.Type(), c.Nonce, keyBytes}) + + result := make([]byte, 0, len(prefix)+len(genericBytes)) + result = append(result, prefix...) + result = append(result, genericBytes...) + return result +} + +// Type returns the certificate algorithm name. It is part of the PublicKey interface. +func (c *Certificate) Type() string { + certName, ok := certificateAlgo(c.Key.Type()) + if !ok { + panic("unknown certificate type for key type " + c.Key.Type()) + } + return certName +} + +// Verify verifies a signature against the certificate's public +// key. It is part of the PublicKey interface. +func (c *Certificate) Verify(data []byte, sig *Signature) error { + return c.Key.Verify(data, sig) +} + +func parseSignatureBody(in []byte) (out *Signature, rest []byte, ok bool) { + format, in, ok := parseString(in) + if !ok { + return + } + + out = &Signature{ + Format: string(format), + } + + if out.Blob, in, ok = parseString(in); !ok { + return + } + + switch out.Format { + case KeyAlgoSKECDSA256, CertAlgoSKECDSA256v01, KeyAlgoSKED25519, CertAlgoSKED25519v01: + out.Rest = in + return out, nil, ok + } + + return out, in, ok +} + +func parseSignature(in []byte) (out *Signature, rest []byte, ok bool) { + sigBytes, rest, ok := parseString(in) + if !ok { + return + } + + out, trailing, ok := parseSignatureBody(sigBytes) + if !ok || len(trailing) > 0 { + return nil, nil, false + } + return +} diff --git a/pkg/proto/ssh/channel.go b/pkg/proto/ssh/channel.go new file mode 100644 index 0000000..c0834c0 --- /dev/null +++ b/pkg/proto/ssh/channel.go @@ -0,0 +1,633 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "encoding/binary" + "errors" + "fmt" + "io" + "log" + "sync" +) + +const ( + minPacketLength = 9 + // channelMaxPacket contains the maximum number of bytes that will be + // sent in a single packet. As per RFC 4253, section 6.1, 32k is also + // the minimum. + channelMaxPacket = 1 << 15 + // We follow OpenSSH here. + channelWindowSize = 64 * channelMaxPacket +) + +// NewChannel represents an incoming request to a channel. It must either be +// accepted for use by calling Accept, or rejected by calling Reject. +type NewChannel interface { + // Accept accepts the channel creation request. It returns the Channel + // and a Go channel containing SSH requests. The Go channel must be + // serviced otherwise the Channel will hang. + Accept() (Channel, <-chan *Request, error) + + // Reject rejects the channel creation request. After calling + // this, no other methods on the Channel may be called. + Reject(reason RejectionReason, message string) error + + // ChannelType returns the type of the channel, as supplied by the + // client. + ChannelType() string + + // ExtraData returns the arbitrary payload for this channel, as supplied + // by the client. This data is specific to the channel type. + ExtraData() []byte +} + +// A Channel is an ordered, reliable, flow-controlled, duplex stream +// that is multiplexed over an SSH connection. +type Channel interface { + // Read reads up to len(data) bytes from the channel. + Read(data []byte) (int, error) + + // Write writes len(data) bytes to the channel. + Write(data []byte) (int, error) + + // Close signals end of channel use. No data may be sent after this + // call. + Close() error + + // CloseWrite signals the end of sending in-band + // data. Requests may still be sent, and the other side may + // still send data + CloseWrite() error + + // SendRequest sends a channel request. If wantReply is true, + // it will wait for a reply and return the result as a + // boolean, otherwise the return value will be false. Channel + // requests are out-of-band messages so they may be sent even + // if the data stream is closed or blocked by flow control. + // If the channel is closed before a reply is returned, io.EOF + // is returned. + SendRequest(name string, wantReply bool, payload []byte) (bool, error) + + // Stderr returns an io.ReadWriter that writes to this channel + // with the extended data type set to stderr. Stderr may + // safely be read and written from a different goroutine than + // Read and Write respectively. + Stderr() io.ReadWriter +} + +// Request is a request sent outside of the normal stream of +// data. Requests can either be specific to an SSH channel, or they +// can be global. +type Request struct { + Type string + WantReply bool + Payload []byte + + ch *channel + mux *mux +} + +// Reply sends a response to a request. It must be called for all requests +// where WantReply is true and is a no-op otherwise. The payload argument is +// ignored for replies to channel-specific requests. +func (r *Request) Reply(ok bool, payload []byte) error { + if !r.WantReply { + return nil + } + + if r.ch == nil { + return r.mux.ackRequest(ok, payload) + } + + return r.ch.ackRequest(ok) +} + +// RejectionReason is an enumeration used when rejecting channel creation +// requests. See RFC 4254, section 5.1. +type RejectionReason uint32 + +const ( + Prohibited RejectionReason = iota + 1 + ConnectionFailed + UnknownChannelType + ResourceShortage +) + +// String converts the rejection reason to human readable form. +func (r RejectionReason) String() string { + switch r { + case Prohibited: + return "administratively prohibited" + case ConnectionFailed: + return "connect failed" + case UnknownChannelType: + return "unknown channel type" + case ResourceShortage: + return "resource shortage" + } + return fmt.Sprintf("unknown reason %d", int(r)) +} + +func min(a uint32, b int) uint32 { + if a < uint32(b) { + return a + } + return uint32(b) +} + +type channelDirection uint8 + +const ( + channelInbound channelDirection = iota + channelOutbound +) + +// channel is an implementation of the Channel interface that works +// with the mux class. +type channel struct { + // R/O after creation + chanType string + extraData []byte + localId, remoteId uint32 + + // maxIncomingPayload and maxRemotePayload are the maximum + // payload sizes of normal and extended data packets for + // receiving and sending, respectively. The wire packet will + // be 9 or 13 bytes larger (excluding encryption overhead). + maxIncomingPayload uint32 + maxRemotePayload uint32 + + mux *mux + + // decided is set to true if an accept or reject message has been sent + // (for outbound channels) or received (for inbound channels). + decided bool + + // direction contains either channelOutbound, for channels created + // locally, or channelInbound, for channels created by the peer. + direction channelDirection + + // Pending internal channel messages. + msg chan interface{} + + // Since requests have no ID, there can be only one request + // with WantReply=true outstanding. This lock is held by a + // goroutine that has such an outgoing request pending. + sentRequestMu sync.Mutex + + incomingRequests chan *Request + + sentEOF bool + + // thread-safe data + remoteWin window + pending *buffer + extPending *buffer + + // windowMu protects myWindow, the flow-control window. + windowMu sync.Mutex + myWindow uint32 + + // writeMu serializes calls to mux.conn.writePacket() and + // protects sentClose and packetPool. This mutex must be + // different from windowMu, as writePacket can block if there + // is a key exchange pending. + writeMu sync.Mutex + sentClose bool + + // packetPool has a buffer for each extended channel ID to + // save allocations during writes. + packetPool map[uint32][]byte +} + +// writePacket sends a packet. If the packet is a channel close, it updates +// sentClose. This method takes the lock c.writeMu. +func (ch *channel) writePacket(packet []byte) error { + ch.writeMu.Lock() + if ch.sentClose { + ch.writeMu.Unlock() + return io.EOF + } + ch.sentClose = (packet[0] == msgChannelClose) + err := ch.mux.conn.writePacket(packet) + ch.writeMu.Unlock() + return err +} + +func (ch *channel) sendMessage(msg interface{}) error { + if debugMux { + log.Printf("send(%d): %#v", ch.mux.chanList.offset, msg) + } + + p := Marshal(msg) + binary.BigEndian.PutUint32(p[1:], ch.remoteId) + return ch.writePacket(p) +} + +// WriteExtended writes data to a specific extended stream. These streams are +// used, for example, for stderr. +func (ch *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err error) { + if ch.sentEOF { + return 0, io.EOF + } + // 1 byte message type, 4 bytes remoteId, 4 bytes data length + opCode := byte(msgChannelData) + headerLength := uint32(9) + if extendedCode > 0 { + headerLength += 4 + opCode = msgChannelExtendedData + } + + ch.writeMu.Lock() + packet := ch.packetPool[extendedCode] + // We don't remove the buffer from packetPool, so + // WriteExtended calls from different goroutines will be + // flagged as errors by the race detector. + ch.writeMu.Unlock() + + for len(data) > 0 { + space := min(ch.maxRemotePayload, len(data)) + if space, err = ch.remoteWin.reserve(space); err != nil { + return n, err + } + if want := headerLength + space; uint32(cap(packet)) < want { + packet = make([]byte, want) + } else { + packet = packet[:want] + } + + todo := data[:space] + + packet[0] = opCode + binary.BigEndian.PutUint32(packet[1:], ch.remoteId) + if extendedCode > 0 { + binary.BigEndian.PutUint32(packet[5:], uint32(extendedCode)) + } + binary.BigEndian.PutUint32(packet[headerLength-4:], uint32(len(todo))) + copy(packet[headerLength:], todo) + if err = ch.writePacket(packet); err != nil { + return n, err + } + + n += len(todo) + data = data[len(todo):] + } + + ch.writeMu.Lock() + ch.packetPool[extendedCode] = packet + ch.writeMu.Unlock() + + return n, err +} + +func (ch *channel) handleData(packet []byte) error { + headerLen := 9 + isExtendedData := packet[0] == msgChannelExtendedData + if isExtendedData { + headerLen = 13 + } + if len(packet) < headerLen { + // malformed data packet + return parseError(packet[0]) + } + + var extended uint32 + if isExtendedData { + extended = binary.BigEndian.Uint32(packet[5:]) + } + + length := binary.BigEndian.Uint32(packet[headerLen-4 : headerLen]) + if length == 0 { + return nil + } + if length > ch.maxIncomingPayload { + // TODO(hanwen): should send Disconnect? + return errors.New("ssh: incoming packet exceeds maximum payload size") + } + + data := packet[headerLen:] + if length != uint32(len(data)) { + return errors.New("ssh: wrong packet length") + } + + ch.windowMu.Lock() + if ch.myWindow < length { + ch.windowMu.Unlock() + // TODO(hanwen): should send Disconnect with reason? + return errors.New("ssh: remote side wrote too much") + } + ch.myWindow -= length + ch.windowMu.Unlock() + + if extended == 1 { + ch.extPending.write(data) + } else if extended > 0 { + // discard other extended data. + } else { + ch.pending.write(data) + } + return nil +} + +func (c *channel) adjustWindow(n uint32) error { + c.windowMu.Lock() + // Since myWindow is managed on our side, and can never exceed + // the initial window setting, we don't worry about overflow. + c.myWindow += uint32(n) + c.windowMu.Unlock() + return c.sendMessage(windowAdjustMsg{ + AdditionalBytes: uint32(n), + }) +} + +func (c *channel) ReadExtended(data []byte, extended uint32) (n int, err error) { + switch extended { + case 1: + n, err = c.extPending.Read(data) + case 0: + n, err = c.pending.Read(data) + default: + return 0, fmt.Errorf("ssh: extended code %d unimplemented", extended) + } + + if n > 0 { + err = c.adjustWindow(uint32(n)) + // sendWindowAdjust can return io.EOF if the remote + // peer has closed the connection, however we want to + // defer forwarding io.EOF to the caller of Read until + // the buffer has been drained. + if n > 0 && err == io.EOF { + err = nil + } + } + + return n, err +} + +func (c *channel) close() { + c.pending.eof() + c.extPending.eof() + close(c.msg) + close(c.incomingRequests) + c.writeMu.Lock() + // This is not necessary for a normal channel teardown, but if + // there was another error, it is. + c.sentClose = true + c.writeMu.Unlock() + // Unblock writers. + c.remoteWin.close() +} + +// responseMessageReceived is called when a success or failure message is +// received on a channel to check that such a message is reasonable for the +// given channel. +func (ch *channel) responseMessageReceived() error { + if ch.direction == channelInbound { + return errors.New("ssh: channel response message received on inbound channel") + } + if ch.decided { + return errors.New("ssh: duplicate response received for channel") + } + ch.decided = true + return nil +} + +func (ch *channel) handlePacket(packet []byte) error { + switch packet[0] { + case msgChannelData, msgChannelExtendedData: + return ch.handleData(packet) + case msgChannelClose: + ch.sendMessage(channelCloseMsg{PeersID: ch.remoteId}) + ch.mux.chanList.remove(ch.localId) + ch.close() + return nil + case msgChannelEOF: + // RFC 4254 is mute on how EOF affects dataExt messages but + // it is logical to signal EOF at the same time. + ch.extPending.eof() + ch.pending.eof() + return nil + } + + decoded, err := decode(packet) + if err != nil { + return err + } + + switch msg := decoded.(type) { + case *channelOpenFailureMsg: + if err := ch.responseMessageReceived(); err != nil { + return err + } + ch.mux.chanList.remove(msg.PeersID) + ch.msg <- msg + case *channelOpenConfirmMsg: + if err := ch.responseMessageReceived(); err != nil { + return err + } + if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 { + return fmt.Errorf("ssh: invalid MaxPacketSize %d from peer", msg.MaxPacketSize) + } + ch.remoteId = msg.MyID + ch.maxRemotePayload = msg.MaxPacketSize + ch.remoteWin.add(msg.MyWindow) + ch.msg <- msg + case *windowAdjustMsg: + if !ch.remoteWin.add(msg.AdditionalBytes) { + return fmt.Errorf("ssh: invalid window update for %d bytes", msg.AdditionalBytes) + } + case *channelRequestMsg: + req := Request{ + Type: msg.Request, + WantReply: msg.WantReply, + Payload: msg.RequestSpecificData, + ch: ch, + } + + ch.incomingRequests <- &req + default: + ch.msg <- msg + } + return nil +} + +func (m *mux) newChannel(chanType string, direction channelDirection, extraData []byte) *channel { + ch := &channel{ + remoteWin: window{Cond: newCond()}, + myWindow: channelWindowSize, + pending: newBuffer(), + extPending: newBuffer(), + direction: direction, + incomingRequests: make(chan *Request, chanSize), + msg: make(chan interface{}, chanSize), + chanType: chanType, + extraData: extraData, + mux: m, + packetPool: make(map[uint32][]byte), + } + ch.localId = m.chanList.add(ch) + return ch +} + +var errUndecided = errors.New("ssh: must Accept or Reject channel") +var errDecidedAlready = errors.New("ssh: can call Accept or Reject only once") + +type extChannel struct { + code uint32 + ch *channel +} + +func (e *extChannel) Write(data []byte) (n int, err error) { + return e.ch.WriteExtended(data, e.code) +} + +func (e *extChannel) Read(data []byte) (n int, err error) { + return e.ch.ReadExtended(data, e.code) +} + +func (ch *channel) Accept() (Channel, <-chan *Request, error) { + if ch.decided { + return nil, nil, errDecidedAlready + } + ch.maxIncomingPayload = channelMaxPacket + confirm := channelOpenConfirmMsg{ + PeersID: ch.remoteId, + MyID: ch.localId, + MyWindow: ch.myWindow, + MaxPacketSize: ch.maxIncomingPayload, + } + ch.decided = true + if err := ch.sendMessage(confirm); err != nil { + return nil, nil, err + } + + return ch, ch.incomingRequests, nil +} + +func (ch *channel) Reject(reason RejectionReason, message string) error { + if ch.decided { + return errDecidedAlready + } + reject := channelOpenFailureMsg{ + PeersID: ch.remoteId, + Reason: reason, + Message: message, + Language: "en", + } + ch.decided = true + return ch.sendMessage(reject) +} + +func (ch *channel) Read(data []byte) (int, error) { + if !ch.decided { + return 0, errUndecided + } + return ch.ReadExtended(data, 0) +} + +func (ch *channel) Write(data []byte) (int, error) { + if !ch.decided { + return 0, errUndecided + } + return ch.WriteExtended(data, 0) +} + +func (ch *channel) CloseWrite() error { + if !ch.decided { + return errUndecided + } + ch.sentEOF = true + return ch.sendMessage(channelEOFMsg{ + PeersID: ch.remoteId}) +} + +func (ch *channel) Close() error { + if !ch.decided { + return errUndecided + } + + return ch.sendMessage(channelCloseMsg{ + PeersID: ch.remoteId}) +} + +// Extended returns an io.ReadWriter that sends and receives data on the given, +// SSH extended stream. Such streams are used, for example, for stderr. +func (ch *channel) Extended(code uint32) io.ReadWriter { + if !ch.decided { + return nil + } + return &extChannel{code, ch} +} + +func (ch *channel) Stderr() io.ReadWriter { + return ch.Extended(1) +} + +func (ch *channel) SendRequest(name string, wantReply bool, payload []byte) (bool, error) { + if !ch.decided { + return false, errUndecided + } + + if wantReply { + ch.sentRequestMu.Lock() + defer ch.sentRequestMu.Unlock() + } + + msg := channelRequestMsg{ + PeersID: ch.remoteId, + Request: name, + WantReply: wantReply, + RequestSpecificData: payload, + } + + if err := ch.sendMessage(msg); err != nil { + return false, err + } + + if wantReply { + m, ok := (<-ch.msg) + if !ok { + return false, io.EOF + } + switch m.(type) { + case *channelRequestFailureMsg: + return false, nil + case *channelRequestSuccessMsg: + return true, nil + default: + return false, fmt.Errorf("ssh: unexpected response to channel request: %#v", m) + } + } + + return false, nil +} + +// ackRequest either sends an ack or nack to the channel request. +func (ch *channel) ackRequest(ok bool) error { + if !ch.decided { + return errUndecided + } + + var msg interface{} + if !ok { + msg = channelRequestFailureMsg{ + PeersID: ch.remoteId, + } + } else { + msg = channelRequestSuccessMsg{ + PeersID: ch.remoteId, + } + } + return ch.sendMessage(msg) +} + +func (ch *channel) ChannelType() string { + return ch.chanType +} + +func (ch *channel) ExtraData() []byte { + return ch.extraData +} diff --git a/pkg/proto/ssh/cipher.go b/pkg/proto/ssh/cipher.go new file mode 100644 index 0000000..a4c8f45 --- /dev/null +++ b/pkg/proto/ssh/cipher.go @@ -0,0 +1,789 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "crypto/aes" + "crypto/cipher" + "crypto/des" + "crypto/rc4" + "crypto/subtle" + "encoding/binary" + "errors" + "fmt" + "hash" + "io" + + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh/internal/poly1305" + "golang.org/x/crypto/chacha20" +) + +const ( + packetSizeMultiple = 16 // TODO(huin) this should be determined by the cipher. + + // RFC 4253 section 6.1 defines a minimum packet size of 32768 that implementations + // MUST be able to process (plus a few more kilobytes for padding and mac). The RFC + // indicates implementations SHOULD be able to handle larger packet sizes, but then + // waffles on about reasonable limits. + // + // OpenSSH caps their maxPacket at 256kB so we choose to do + // the same. maxPacket is also used to ensure that uint32 + // length fields do not overflow, so it should remain well + // below 4G. + maxPacket = 256 * 1024 +) + +// noneCipher implements cipher.Stream and provides no encryption. It is used +// by the transport before the first key-exchange. +type noneCipher struct{} + +func (c noneCipher) XORKeyStream(dst, src []byte) { + copy(dst, src) +} + +func newAESCTR(key, iv []byte) (cipher.Stream, error) { + c, err := aes.NewCipher(key) + if err != nil { + return nil, err + } + return cipher.NewCTR(c, iv), nil +} + +func newRC4(key, iv []byte) (cipher.Stream, error) { + return rc4.NewCipher(key) +} + +type cipherMode struct { + keySize int + ivSize int + create func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error) +} + +func streamCipherMode(skip int, createFunc func(key, iv []byte) (cipher.Stream, error)) func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error) { + return func(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { + stream, err := createFunc(key, iv) + if err != nil { + return nil, err + } + + var streamDump []byte + if skip > 0 { + streamDump = make([]byte, 512) + } + + for remainingToDump := skip; remainingToDump > 0; { + dumpThisTime := remainingToDump + if dumpThisTime > len(streamDump) { + dumpThisTime = len(streamDump) + } + stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime]) + remainingToDump -= dumpThisTime + } + + mac := macModes[algs.MAC].new(macKey) + return &streamPacketCipher{ + mac: mac, + etm: macModes[algs.MAC].etm, + macResult: make([]byte, mac.Size()), + cipher: stream, + }, nil + } +} + +// cipherModes documents properties of supported ciphers. Ciphers not included +// are not supported and will not be negotiated, even if explicitly requested in +// ClientConfig.Crypto.Ciphers. +var cipherModes = map[string]*cipherMode{ + // Ciphers from RFC 4344, which introduced many CTR-based ciphers. Algorithms + // are defined in the order specified in the RFC. + "aes128-ctr": {16, aes.BlockSize, streamCipherMode(0, newAESCTR)}, + "aes192-ctr": {24, aes.BlockSize, streamCipherMode(0, newAESCTR)}, + "aes256-ctr": {32, aes.BlockSize, streamCipherMode(0, newAESCTR)}, + + // Ciphers from RFC 4345, which introduces security-improved arcfour ciphers. + // They are defined in the order specified in the RFC. + "arcfour128": {16, 0, streamCipherMode(1536, newRC4)}, + "arcfour256": {32, 0, streamCipherMode(1536, newRC4)}, + + // Cipher defined in RFC 4253, which describes SSH Transport Layer Protocol. + // Note that this cipher is not safe, as stated in RFC 4253: "Arcfour (and + // RC4) has problems with weak keys, and should be used with caution." + // RFC 4345 introduces improved versions of Arcfour. + "arcfour": {16, 0, streamCipherMode(0, newRC4)}, + + // AEAD ciphers + gcm128CipherID: {16, 12, newGCMCipher}, + gcm256CipherID: {32, 12, newGCMCipher}, + chacha20Poly1305ID: {64, 0, newChaCha20Cipher}, + + // CBC mode is insecure and so is not included in the default config. + // (See https://www.ieee-security.org/TC/SP2013/papers/4977a526.pdf). If absolutely + // needed, it's possible to specify a custom Config to enable it. + // You should expect that an active attacker can recover plaintext if + // you do. + aes128cbcID: {16, aes.BlockSize, newAESCBCCipher}, + + // 3des-cbc is insecure and is not included in the default + // config. + tripledescbcID: {24, des.BlockSize, newTripleDESCBCCipher}, +} + +// prefixLen is the length of the packet prefix that contains the packet length +// and number of padding bytes. +const prefixLen = 5 + +// streamPacketCipher is a packetCipher using a stream cipher. +type streamPacketCipher struct { + mac hash.Hash + cipher cipher.Stream + etm bool + + // The following members are to avoid per-packet allocations. + prefix [prefixLen]byte + seqNumBytes [4]byte + padding [2 * packetSizeMultiple]byte + packetData []byte + macResult []byte +} + +// readCipherPacket reads and decrypt a single packet from the reader argument. +func (s *streamPacketCipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) { + if _, err := io.ReadFull(r, s.prefix[:]); err != nil { + return nil, err + } + + var encryptedPaddingLength [1]byte + if s.mac != nil && s.etm { + copy(encryptedPaddingLength[:], s.prefix[4:5]) + s.cipher.XORKeyStream(s.prefix[4:5], s.prefix[4:5]) + } else { + s.cipher.XORKeyStream(s.prefix[:], s.prefix[:]) + } + + length := binary.BigEndian.Uint32(s.prefix[0:4]) + paddingLength := uint32(s.prefix[4]) + + var macSize uint32 + if s.mac != nil { + s.mac.Reset() + binary.BigEndian.PutUint32(s.seqNumBytes[:], seqNum) + s.mac.Write(s.seqNumBytes[:]) + if s.etm { + s.mac.Write(s.prefix[:4]) + s.mac.Write(encryptedPaddingLength[:]) + } else { + s.mac.Write(s.prefix[:]) + } + macSize = uint32(s.mac.Size()) + } + + if length <= paddingLength+1 { + return nil, errors.New("ssh: invalid packet length, packet too small") + } + + if length > maxPacket { + return nil, errors.New("ssh: invalid packet length, packet too large") + } + + // the maxPacket check above ensures that length-1+macSize + // does not overflow. + if uint32(cap(s.packetData)) < length-1+macSize { + s.packetData = make([]byte, length-1+macSize) + } else { + s.packetData = s.packetData[:length-1+macSize] + } + + if _, err := io.ReadFull(r, s.packetData); err != nil { + return nil, err + } + mac := s.packetData[length-1:] + data := s.packetData[:length-1] + + if s.mac != nil && s.etm { + s.mac.Write(data) + } + + s.cipher.XORKeyStream(data, data) + + if s.mac != nil { + if !s.etm { + s.mac.Write(data) + } + s.macResult = s.mac.Sum(s.macResult[:0]) + if subtle.ConstantTimeCompare(s.macResult, mac) != 1 { + return nil, errors.New("ssh: MAC failure") + } + } + + return s.packetData[:length-paddingLength-1], nil +} + +// writeCipherPacket encrypts and sends a packet of data to the writer argument +func (s *streamPacketCipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error { + if len(packet) > maxPacket { + return errors.New("ssh: packet too large") + } + + aadlen := 0 + if s.mac != nil && s.etm { + // packet length is not encrypted for EtM modes + aadlen = 4 + } + + paddingLength := packetSizeMultiple - (prefixLen+len(packet)-aadlen)%packetSizeMultiple + if paddingLength < 4 { + paddingLength += packetSizeMultiple + } + + length := len(packet) + 1 + paddingLength + binary.BigEndian.PutUint32(s.prefix[:], uint32(length)) + s.prefix[4] = byte(paddingLength) + padding := s.padding[:paddingLength] + if _, err := io.ReadFull(rand, padding); err != nil { + return err + } + + if s.mac != nil { + s.mac.Reset() + binary.BigEndian.PutUint32(s.seqNumBytes[:], seqNum) + s.mac.Write(s.seqNumBytes[:]) + + if s.etm { + // For EtM algorithms, the packet length must stay unencrypted, + // but the following data (padding length) must be encrypted + s.cipher.XORKeyStream(s.prefix[4:5], s.prefix[4:5]) + } + + s.mac.Write(s.prefix[:]) + + if !s.etm { + // For non-EtM algorithms, the algorithm is applied on unencrypted data + s.mac.Write(packet) + s.mac.Write(padding) + } + } + + if !(s.mac != nil && s.etm) { + // For EtM algorithms, the padding length has already been encrypted + // and the packet length must remain unencrypted + s.cipher.XORKeyStream(s.prefix[:], s.prefix[:]) + } + + s.cipher.XORKeyStream(packet, packet) + s.cipher.XORKeyStream(padding, padding) + + if s.mac != nil && s.etm { + // For EtM algorithms, packet and padding must be encrypted + s.mac.Write(packet) + s.mac.Write(padding) + } + + if _, err := w.Write(s.prefix[:]); err != nil { + return err + } + if _, err := w.Write(packet); err != nil { + return err + } + if _, err := w.Write(padding); err != nil { + return err + } + + if s.mac != nil { + s.macResult = s.mac.Sum(s.macResult[:0]) + if _, err := w.Write(s.macResult); err != nil { + return err + } + } + + return nil +} + +type gcmCipher struct { + aead cipher.AEAD + prefix [4]byte + iv []byte + buf []byte +} + +func newGCMCipher(key, iv, unusedMacKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) { + c, err := aes.NewCipher(key) + if err != nil { + return nil, err + } + + aead, err := cipher.NewGCM(c) + if err != nil { + return nil, err + } + + return &gcmCipher{ + aead: aead, + iv: iv, + }, nil +} + +const gcmTagSize = 16 + +func (c *gcmCipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error { + // Pad out to multiple of 16 bytes. This is different from the + // stream cipher because that encrypts the length too. + padding := byte(packetSizeMultiple - (1+len(packet))%packetSizeMultiple) + if padding < 4 { + padding += packetSizeMultiple + } + + length := uint32(len(packet) + int(padding) + 1) + binary.BigEndian.PutUint32(c.prefix[:], length) + if _, err := w.Write(c.prefix[:]); err != nil { + return err + } + + if cap(c.buf) < int(length) { + c.buf = make([]byte, length) + } else { + c.buf = c.buf[:length] + } + + c.buf[0] = padding + copy(c.buf[1:], packet) + if _, err := io.ReadFull(rand, c.buf[1+len(packet):]); err != nil { + return err + } + c.buf = c.aead.Seal(c.buf[:0], c.iv, c.buf, c.prefix[:]) + if _, err := w.Write(c.buf); err != nil { + return err + } + c.incIV() + + return nil +} + +func (c *gcmCipher) incIV() { + for i := 4 + 7; i >= 4; i-- { + c.iv[i]++ + if c.iv[i] != 0 { + break + } + } +} + +func (c *gcmCipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) { + if _, err := io.ReadFull(r, c.prefix[:]); err != nil { + return nil, err + } + length := binary.BigEndian.Uint32(c.prefix[:]) + if length > maxPacket { + return nil, errors.New("ssh: max packet length exceeded") + } + + if cap(c.buf) < int(length+gcmTagSize) { + c.buf = make([]byte, length+gcmTagSize) + } else { + c.buf = c.buf[:length+gcmTagSize] + } + + if _, err := io.ReadFull(r, c.buf); err != nil { + return nil, err + } + + plain, err := c.aead.Open(c.buf[:0], c.iv, c.buf, c.prefix[:]) + if err != nil { + return nil, err + } + c.incIV() + + if len(plain) == 0 { + return nil, errors.New("ssh: empty packet") + } + + padding := plain[0] + if padding < 4 { + // padding is a byte, so it automatically satisfies + // the maximum size, which is 255. + return nil, fmt.Errorf("ssh: illegal padding %d", padding) + } + + if int(padding+1) >= len(plain) { + return nil, fmt.Errorf("ssh: padding %d too large", padding) + } + plain = plain[1 : length-uint32(padding)] + return plain, nil +} + +// cbcCipher implements aes128-cbc cipher defined in RFC 4253 section 6.1 +type cbcCipher struct { + mac hash.Hash + macSize uint32 + decrypter cipher.BlockMode + encrypter cipher.BlockMode + + // The following members are to avoid per-packet allocations. + seqNumBytes [4]byte + packetData []byte + macResult []byte + + // Amount of data we should still read to hide which + // verification error triggered. + oracleCamouflage uint32 +} + +func newCBCCipher(c cipher.Block, key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { + cbc := &cbcCipher{ + mac: macModes[algs.MAC].new(macKey), + decrypter: cipher.NewCBCDecrypter(c, iv), + encrypter: cipher.NewCBCEncrypter(c, iv), + packetData: make([]byte, 1024), + } + if cbc.mac != nil { + cbc.macSize = uint32(cbc.mac.Size()) + } + + return cbc, nil +} + +func newAESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { + c, err := aes.NewCipher(key) + if err != nil { + return nil, err + } + + cbc, err := newCBCCipher(c, key, iv, macKey, algs) + if err != nil { + return nil, err + } + + return cbc, nil +} + +func newTripleDESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { + c, err := des.NewTripleDESCipher(key) + if err != nil { + return nil, err + } + + cbc, err := newCBCCipher(c, key, iv, macKey, algs) + if err != nil { + return nil, err + } + + return cbc, nil +} + +func maxUInt32(a, b int) uint32 { + if a > b { + return uint32(a) + } + return uint32(b) +} + +const ( + cbcMinPacketSizeMultiple = 8 + cbcMinPacketSize = 16 + cbcMinPaddingSize = 4 +) + +// cbcError represents a verification error that may leak information. +type cbcError string + +func (e cbcError) Error() string { return string(e) } + +func (c *cbcCipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) { + p, err := c.readCipherPacketLeaky(seqNum, r) + if err != nil { + if _, ok := err.(cbcError); ok { + // Verification error: read a fixed amount of + // data, to make distinguishing between + // failing MAC and failing length check more + // difficult. + io.CopyN(io.Discard, r, int64(c.oracleCamouflage)) + } + } + return p, err +} + +func (c *cbcCipher) readCipherPacketLeaky(seqNum uint32, r io.Reader) ([]byte, error) { + blockSize := c.decrypter.BlockSize() + + // Read the header, which will include some of the subsequent data in the + // case of block ciphers - this is copied back to the payload later. + // How many bytes of payload/padding will be read with this first read. + firstBlockLength := uint32((prefixLen + blockSize - 1) / blockSize * blockSize) + firstBlock := c.packetData[:firstBlockLength] + if _, err := io.ReadFull(r, firstBlock); err != nil { + return nil, err + } + + c.oracleCamouflage = maxPacket + 4 + c.macSize - firstBlockLength + + c.decrypter.CryptBlocks(firstBlock, firstBlock) + length := binary.BigEndian.Uint32(firstBlock[:4]) + if length > maxPacket { + return nil, cbcError("ssh: packet too large") + } + if length+4 < maxUInt32(cbcMinPacketSize, blockSize) { + // The minimum size of a packet is 16 (or the cipher block size, whichever + // is larger) bytes. + return nil, cbcError("ssh: packet too small") + } + // The length of the packet (including the length field but not the MAC) must + // be a multiple of the block size or 8, whichever is larger. + if (length+4)%maxUInt32(cbcMinPacketSizeMultiple, blockSize) != 0 { + return nil, cbcError("ssh: invalid packet length multiple") + } + + paddingLength := uint32(firstBlock[4]) + if paddingLength < cbcMinPaddingSize || length <= paddingLength+1 { + return nil, cbcError("ssh: invalid packet length") + } + + // Positions within the c.packetData buffer: + macStart := 4 + length + paddingStart := macStart - paddingLength + + // Entire packet size, starting before length, ending at end of mac. + entirePacketSize := macStart + c.macSize + + // Ensure c.packetData is large enough for the entire packet data. + if uint32(cap(c.packetData)) < entirePacketSize { + // Still need to upsize and copy, but this should be rare at runtime, only + // on upsizing the packetData buffer. + c.packetData = make([]byte, entirePacketSize) + copy(c.packetData, firstBlock) + } else { + c.packetData = c.packetData[:entirePacketSize] + } + + n, err := io.ReadFull(r, c.packetData[firstBlockLength:]) + if err != nil { + return nil, err + } + c.oracleCamouflage -= uint32(n) + + remainingCrypted := c.packetData[firstBlockLength:macStart] + c.decrypter.CryptBlocks(remainingCrypted, remainingCrypted) + + mac := c.packetData[macStart:] + if c.mac != nil { + c.mac.Reset() + binary.BigEndian.PutUint32(c.seqNumBytes[:], seqNum) + c.mac.Write(c.seqNumBytes[:]) + c.mac.Write(c.packetData[:macStart]) + c.macResult = c.mac.Sum(c.macResult[:0]) + if subtle.ConstantTimeCompare(c.macResult, mac) != 1 { + return nil, cbcError("ssh: MAC failure") + } + } + + return c.packetData[prefixLen:paddingStart], nil +} + +func (c *cbcCipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error { + effectiveBlockSize := maxUInt32(cbcMinPacketSizeMultiple, c.encrypter.BlockSize()) + + // Length of encrypted portion of the packet (header, payload, padding). + // Enforce minimum padding and packet size. + encLength := maxUInt32(prefixLen+len(packet)+cbcMinPaddingSize, cbcMinPaddingSize) + // Enforce block size. + encLength = (encLength + effectiveBlockSize - 1) / effectiveBlockSize * effectiveBlockSize + + length := encLength - 4 + paddingLength := int(length) - (1 + len(packet)) + + // Overall buffer contains: header, payload, padding, mac. + // Space for the MAC is reserved in the capacity but not the slice length. + bufferSize := encLength + c.macSize + if uint32(cap(c.packetData)) < bufferSize { + c.packetData = make([]byte, encLength, bufferSize) + } else { + c.packetData = c.packetData[:encLength] + } + + p := c.packetData + + // Packet header. + binary.BigEndian.PutUint32(p, length) + p = p[4:] + p[0] = byte(paddingLength) + + // Payload. + p = p[1:] + copy(p, packet) + + // Padding. + p = p[len(packet):] + if _, err := io.ReadFull(rand, p); err != nil { + return err + } + + if c.mac != nil { + c.mac.Reset() + binary.BigEndian.PutUint32(c.seqNumBytes[:], seqNum) + c.mac.Write(c.seqNumBytes[:]) + c.mac.Write(c.packetData) + // The MAC is now appended into the capacity reserved for it earlier. + c.packetData = c.mac.Sum(c.packetData) + } + + c.encrypter.CryptBlocks(c.packetData[:encLength], c.packetData[:encLength]) + + if _, err := w.Write(c.packetData); err != nil { + return err + } + + return nil +} + +const chacha20Poly1305ID = "chacha20-poly1305@openssh.com" + +// chacha20Poly1305Cipher implements the chacha20-poly1305@openssh.com +// AEAD, which is described here: +// +// https://tools.ietf.org/html/draft-josefsson-ssh-chacha20-poly1305-openssh-00 +// +// the methods here also implement padding, which RFC 4253 Section 6 +// also requires of stream ciphers. +type chacha20Poly1305Cipher struct { + lengthKey [32]byte + contentKey [32]byte + buf []byte +} + +func newChaCha20Cipher(key, unusedIV, unusedMACKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) { + if len(key) != 64 { + panic(len(key)) + } + + c := &chacha20Poly1305Cipher{ + buf: make([]byte, 256), + } + + copy(c.contentKey[:], key[:32]) + copy(c.lengthKey[:], key[32:]) + return c, nil +} + +func (c *chacha20Poly1305Cipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) { + nonce := make([]byte, 12) + binary.BigEndian.PutUint32(nonce[8:], seqNum) + s, err := chacha20.NewUnauthenticatedCipher(c.contentKey[:], nonce) + if err != nil { + return nil, err + } + var polyKey, discardBuf [32]byte + s.XORKeyStream(polyKey[:], polyKey[:]) + s.XORKeyStream(discardBuf[:], discardBuf[:]) // skip the next 32 bytes + + encryptedLength := c.buf[:4] + if _, err := io.ReadFull(r, encryptedLength); err != nil { + return nil, err + } + + var lenBytes [4]byte + ls, err := chacha20.NewUnauthenticatedCipher(c.lengthKey[:], nonce) + if err != nil { + return nil, err + } + ls.XORKeyStream(lenBytes[:], encryptedLength) + + length := binary.BigEndian.Uint32(lenBytes[:]) + if length > maxPacket { + return nil, errors.New("ssh: invalid packet length, packet too large") + } + + contentEnd := 4 + length + packetEnd := contentEnd + poly1305.TagSize + if uint32(cap(c.buf)) < packetEnd { + c.buf = make([]byte, packetEnd) + copy(c.buf[:], encryptedLength) + } else { + c.buf = c.buf[:packetEnd] + } + + if _, err := io.ReadFull(r, c.buf[4:packetEnd]); err != nil { + return nil, err + } + + var mac [poly1305.TagSize]byte + copy(mac[:], c.buf[contentEnd:packetEnd]) + if !poly1305.Verify(&mac, c.buf[:contentEnd], &polyKey) { + return nil, errors.New("ssh: MAC failure") + } + + plain := c.buf[4:contentEnd] + s.XORKeyStream(plain, plain) + + if len(plain) == 0 { + return nil, errors.New("ssh: empty packet") + } + + padding := plain[0] + if padding < 4 { + // padding is a byte, so it automatically satisfies + // the maximum size, which is 255. + return nil, fmt.Errorf("ssh: illegal padding %d", padding) + } + + if int(padding)+1 >= len(plain) { + return nil, fmt.Errorf("ssh: padding %d too large", padding) + } + + plain = plain[1 : len(plain)-int(padding)] + + return plain, nil +} + +func (c *chacha20Poly1305Cipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, payload []byte) error { + nonce := make([]byte, 12) + binary.BigEndian.PutUint32(nonce[8:], seqNum) + s, err := chacha20.NewUnauthenticatedCipher(c.contentKey[:], nonce) + if err != nil { + return err + } + var polyKey, discardBuf [32]byte + s.XORKeyStream(polyKey[:], polyKey[:]) + s.XORKeyStream(discardBuf[:], discardBuf[:]) // skip the next 32 bytes + + // There is no blocksize, so fall back to multiple of 8 byte + // padding, as described in RFC 4253, Sec 6. + const packetSizeMultiple = 8 + + padding := packetSizeMultiple - (1+len(payload))%packetSizeMultiple + if padding < 4 { + padding += packetSizeMultiple + } + + // size (4 bytes), padding (1), payload, padding, tag. + totalLength := 4 + 1 + len(payload) + padding + poly1305.TagSize + if cap(c.buf) < totalLength { + c.buf = make([]byte, totalLength) + } else { + c.buf = c.buf[:totalLength] + } + + binary.BigEndian.PutUint32(c.buf, uint32(1+len(payload)+padding)) + ls, err := chacha20.NewUnauthenticatedCipher(c.lengthKey[:], nonce) + if err != nil { + return err + } + ls.XORKeyStream(c.buf, c.buf[:4]) + c.buf[4] = byte(padding) + copy(c.buf[5:], payload) + packetEnd := 5 + len(payload) + padding + if _, err := io.ReadFull(rand, c.buf[5+len(payload):packetEnd]); err != nil { + return err + } + + s.XORKeyStream(c.buf[4:], c.buf[4:packetEnd]) + + var mac [poly1305.TagSize]byte + poly1305.Sum(&mac, c.buf[:packetEnd], &polyKey) + + copy(c.buf[packetEnd:], mac[:]) + + if _, err := w.Write(c.buf); err != nil { + return err + } + return nil +} diff --git a/pkg/proto/ssh/client.go b/pkg/proto/ssh/client.go new file mode 100644 index 0000000..bdc356c --- /dev/null +++ b/pkg/proto/ssh/client.go @@ -0,0 +1,282 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "bytes" + "errors" + "fmt" + "net" + "os" + "sync" + "time" +) + +// Client implements a traditional SSH client that supports shells, +// subprocesses, TCP port/streamlocal forwarding and tunneled dialing. +type Client struct { + Conn + + handleForwardsOnce sync.Once // guards calling (*Client).handleForwards + + forwards forwardList // forwarded tcpip connections from the remote side + mu sync.Mutex + channelHandlers map[string]chan NewChannel +} + +// HandleChannelOpen returns a channel on which NewChannel requests +// for the given type are sent. If the type already is being handled, +// nil is returned. The channel is closed when the connection is closed. +func (c *Client) HandleChannelOpen(channelType string) <-chan NewChannel { + c.mu.Lock() + defer c.mu.Unlock() + if c.channelHandlers == nil { + // The SSH channel has been closed. + c := make(chan NewChannel) + close(c) + return c + } + + ch := c.channelHandlers[channelType] + if ch != nil { + return nil + } + + ch = make(chan NewChannel, chanSize) + c.channelHandlers[channelType] = ch + return ch +} + +// NewClient creates a Client on top of the given connection. +func NewClient(c Conn, chans <-chan NewChannel, reqs <-chan *Request) *Client { + conn := &Client{ + Conn: c, + channelHandlers: make(map[string]chan NewChannel, 1), + } + + go conn.handleGlobalRequests(reqs) + go conn.handleChannelOpens(chans) + go func() { + conn.Wait() + conn.forwards.closeAll() + }() + return conn +} + +// NewClientConn establishes an authenticated SSH connection using c +// as the underlying transport. The Request and NewChannel channels +// must be serviced or the connection will hang. +func NewClientConn(c net.Conn, addr string, config *ClientConfig) (Conn, <-chan NewChannel, <-chan *Request, error) { + fullConf := *config + fullConf.SetDefaults() + if fullConf.HostKeyCallback == nil { + c.Close() + return nil, nil, nil, errors.New("ssh: must specify HostKeyCallback") + } + + conn := &connection{ + sshConn: sshConn{conn: c, user: fullConf.User}, + } + + if err := conn.clientHandshake(addr, &fullConf); err != nil { + c.Close() + return nil, nil, nil, fmt.Errorf("ssh: handshake failed: %v", err) + } + conn.mux = newMux(conn.transport) + return conn, conn.mux.incomingChannels, conn.mux.incomingRequests, nil +} + +// clientHandshake performs the client side key exchange. See RFC 4253 Section +// 7. +func (c *connection) clientHandshake(dialAddress string, config *ClientConfig) error { + if config.ClientVersion != "" { + c.clientVersion = []byte(config.ClientVersion) + } else { + c.clientVersion = []byte(packageVersion) + } + var err error + c.serverVersion, err = exchangeVersions(c.sshConn.conn, c.clientVersion) + if err != nil { + return err + } + + c.transport = newClientTransport( + newTransport(c.sshConn.conn, config.Rand, true /* is client */), + c.clientVersion, c.serverVersion, config, dialAddress, c.sshConn.RemoteAddr()) + if err := c.transport.waitSession(); err != nil { + return err + } + + c.sessionID = c.transport.getSessionID() + return c.clientAuthenticate(config) +} + +// verifyHostKeySignature verifies the host key obtained in the key exchange. +// algo is the negotiated algorithm, and may be a certificate type. +func verifyHostKeySignature(hostKey PublicKey, algo string, result *kexResult) error { + sig, rest, ok := parseSignatureBody(result.Signature) + if len(rest) > 0 || !ok { + return errors.New("ssh: signature parse error") + } + + if a := underlyingAlgo(algo); sig.Format != a { + return fmt.Errorf("ssh: invalid signature algorithm %q, expected %q", sig.Format, a) + } + + return hostKey.Verify(result.H, sig) +} + +// NewSession opens a new Session for this client. (A session is a remote +// execution of a program.) +func (c *Client) NewSession() (*Session, error) { + ch, in, err := c.OpenChannel("session", nil) + if err != nil { + return nil, err + } + return newSession(ch, in) +} + +func (c *Client) handleGlobalRequests(incoming <-chan *Request) { + for r := range incoming { + // This handles keepalive messages and matches + // the behaviour of OpenSSH. + r.Reply(false, nil) + } +} + +// handleChannelOpens channel open messages from the remote side. +func (c *Client) handleChannelOpens(in <-chan NewChannel) { + for ch := range in { + c.mu.Lock() + handler := c.channelHandlers[ch.ChannelType()] + c.mu.Unlock() + + if handler != nil { + handler <- ch + } else { + ch.Reject(UnknownChannelType, fmt.Sprintf("unknown channel type: %v", ch.ChannelType())) + } + } + + c.mu.Lock() + for _, ch := range c.channelHandlers { + close(ch) + } + c.channelHandlers = nil + c.mu.Unlock() +} + +// Dial starts a client connection to the given SSH server. It is a +// convenience function that connects to the given network address, +// initiates the SSH handshake, and then sets up a Client. For access +// to incoming channels and requests, use net.Dial with NewClientConn +// instead. +func Dial(network, addr string, config *ClientConfig) (*Client, error) { + conn, err := net.DialTimeout(network, addr, config.Timeout) + if err != nil { + return nil, err + } + c, chans, reqs, err := NewClientConn(conn, addr, config) + if err != nil { + return nil, err + } + return NewClient(c, chans, reqs), nil +} + +// HostKeyCallback is the function type used for verifying server +// keys. A HostKeyCallback must return nil if the host key is OK, or +// an error to reject it. It receives the hostname as passed to Dial +// or NewClientConn. The remote address is the RemoteAddr of the +// net.Conn underlying the SSH connection. +type HostKeyCallback func(hostname string, remote net.Addr, key PublicKey) error + +// BannerCallback is the function type used for treat the banner sent by +// the server. A BannerCallback receives the message sent by the remote server. +type BannerCallback func(message string) error + +// A ClientConfig structure is used to configure a Client. It must not be +// modified after having been passed to an SSH function. +type ClientConfig struct { + // Config contains configuration that is shared between clients and + // servers. + Config + + // User contains the username to authenticate as. + User string + + // Auth contains possible authentication methods to use with the + // server. Only the first instance of a particular RFC 4252 method will + // be used during authentication. + Auth []AuthMethod + + // HostKeyCallback is called during the cryptographic + // handshake to validate the server's host key. The client + // configuration must supply this callback for the connection + // to succeed. The functions InsecureIgnoreHostKey or + // FixedHostKey can be used for simplistic host key checks. + HostKeyCallback HostKeyCallback + + // BannerCallback is called during the SSH dance to display a custom + // server's message. The client configuration can supply this callback to + // handle it as wished. The function BannerDisplayStderr can be used for + // simplistic display on Stderr. + BannerCallback BannerCallback + + // ClientVersion contains the version identification string that will + // be used for the connection. If empty, a reasonable default is used. + ClientVersion string + + // HostKeyAlgorithms lists the public key algorithms that the client will + // accept from the server for host key authentication, in order of + // preference. If empty, a reasonable default is used. Any + // string returned from a PublicKey.Type method may be used, or + // any of the CertAlgo and KeyAlgo constants. + HostKeyAlgorithms []string + + // Timeout is the maximum amount of time for the TCP connection to establish. + // + // A Timeout of zero means no timeout. + Timeout time.Duration +} + +// InsecureIgnoreHostKey returns a function that can be used for +// ClientConfig.HostKeyCallback to accept any host key. It should +// not be used for production code. +func InsecureIgnoreHostKey() HostKeyCallback { + return func(hostname string, remote net.Addr, key PublicKey) error { + return nil + } +} + +type fixedHostKey struct { + key PublicKey +} + +func (f *fixedHostKey) check(hostname string, remote net.Addr, key PublicKey) error { + if f.key == nil { + return fmt.Errorf("ssh: required host key was nil") + } + if !bytes.Equal(key.Marshal(), f.key.Marshal()) { + return fmt.Errorf("ssh: host key mismatch") + } + return nil +} + +// FixedHostKey returns a function for use in +// ClientConfig.HostKeyCallback to accept only a specific host key. +func FixedHostKey(key PublicKey) HostKeyCallback { + hk := &fixedHostKey{key} + return hk.check +} + +// BannerDisplayStderr returns a function that can be used for +// ClientConfig.BannerCallback to display banners on os.Stderr. +func BannerDisplayStderr() BannerCallback { + return func(banner string) error { + _, err := os.Stderr.WriteString(banner) + + return err + } +} diff --git a/pkg/proto/ssh/client_auth.go b/pkg/proto/ssh/client_auth.go new file mode 100644 index 0000000..5c3bc25 --- /dev/null +++ b/pkg/proto/ssh/client_auth.go @@ -0,0 +1,761 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "bytes" + "errors" + "fmt" + "io" + "strings" +) + +type authResult int + +const ( + authFailure authResult = iota + authPartialSuccess + authSuccess +) + +// clientAuthenticate authenticates with the remote server. See RFC 4252. +func (c *connection) clientAuthenticate(config *ClientConfig) error { + // initiate user auth session + if err := c.transport.writePacket(Marshal(&serviceRequestMsg{serviceUserAuth})); err != nil { + return err + } + packet, err := c.transport.readPacket() + if err != nil { + return err + } + // The server may choose to send a SSH_MSG_EXT_INFO at this point (if we + // advertised willingness to receive one, which we always do) or not. See + // RFC 8308, Section 2.4. + extensions := make(map[string][]byte) + if len(packet) > 0 && packet[0] == msgExtInfo { + var extInfo extInfoMsg + if err := Unmarshal(packet, &extInfo); err != nil { + return err + } + payload := extInfo.Payload + for i := uint32(0); i < extInfo.NumExtensions; i++ { + name, rest, ok := parseString(payload) + if !ok { + return parseError(msgExtInfo) + } + value, rest, ok := parseString(rest) + if !ok { + return parseError(msgExtInfo) + } + extensions[string(name)] = value + payload = rest + } + packet, err = c.transport.readPacket() + if err != nil { + return err + } + } + var serviceAccept serviceAcceptMsg + if err := Unmarshal(packet, &serviceAccept); err != nil { + return err + } + + // during the authentication phase the client first attempts the "none" method + // then any untried methods suggested by the server. + var tried []string + var lastMethods []string + + sessionID := c.transport.getSessionID() + for auth := AuthMethod(new(noneAuth)); auth != nil; { + ok, methods, err := auth.auth(sessionID, config.User, c.transport, config.Rand, extensions) + if err != nil { + // We return the error later if there is no other method left to + // try. + ok = authFailure + } + if ok == authSuccess { + // success + return nil + } else if ok == authFailure { + if m := auth.method(); !contains(tried, m) { + tried = append(tried, m) + } + } + if methods == nil { + methods = lastMethods + } + lastMethods = methods + + auth = nil + + findNext: + for _, a := range config.Auth { + candidateMethod := a.method() + if contains(tried, candidateMethod) { + continue + } + for _, meth := range methods { + if meth == candidateMethod { + auth = a + break findNext + } + } + } + + if auth == nil && err != nil { + // We have an error and there are no other authentication methods to + // try, so we return it. + return err + } + } + return fmt.Errorf("ssh: unable to authenticate, attempted methods %v, no supported methods remain", tried) +} + +func contains(list []string, e string) bool { + for _, s := range list { + if s == e { + return true + } + } + return false +} + +// An AuthMethod represents an instance of an RFC 4252 authentication method. +type AuthMethod interface { + // auth authenticates user over transport t. + // Returns true if authentication is successful. + // If authentication is not successful, a []string of alternative + // method names is returned. If the slice is nil, it will be ignored + // and the previous set of possible methods will be reused. + auth(session []byte, user string, p packetConn, rand io.Reader, extensions map[string][]byte) (authResult, []string, error) + + // method returns the RFC 4252 method name. + method() string +} + +// "none" authentication, RFC 4252 section 5.2. +type noneAuth int + +func (n *noneAuth) auth(session []byte, user string, c packetConn, rand io.Reader, _ map[string][]byte) (authResult, []string, error) { + if err := c.writePacket(Marshal(&userAuthRequestMsg{ + User: user, + Service: serviceSSH, + Method: "none", + })); err != nil { + return authFailure, nil, err + } + + return handleAuthResponse(c) +} + +func (n *noneAuth) method() string { + return "none" +} + +// passwordCallback is an AuthMethod that fetches the password through +// a function call, e.g. by prompting the user. +type passwordCallback func() (password string, err error) + +func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand io.Reader, _ map[string][]byte) (authResult, []string, error) { + type passwordAuthMsg struct { + User string `sshtype:"50"` + Service string + Method string + Reply bool + Password string + } + + pw, err := cb() + // REVIEW NOTE: is there a need to support skipping a password attempt? + // The program may only find out that the user doesn't have a password + // when prompting. + if err != nil { + return authFailure, nil, err + } + + if err := c.writePacket(Marshal(&passwordAuthMsg{ + User: user, + Service: serviceSSH, + Method: cb.method(), + Reply: false, + Password: pw, + })); err != nil { + return authFailure, nil, err + } + + return handleAuthResponse(c) +} + +func (cb passwordCallback) method() string { + return "password" +} + +// Password returns an AuthMethod using the given password. +func Password(secret string) AuthMethod { + return passwordCallback(func() (string, error) { return secret, nil }) +} + +// PasswordCallback returns an AuthMethod that uses a callback for +// fetching a password. +func PasswordCallback(prompt func() (secret string, err error)) AuthMethod { + return passwordCallback(prompt) +} + +type publickeyAuthMsg struct { + User string `sshtype:"50"` + Service string + Method string + // HasSig indicates to the receiver packet that the auth request is signed and + // should be used for authentication of the request. + HasSig bool + Algoname string + PubKey []byte + // Sig is tagged with "rest" so Marshal will exclude it during + // validateKey + Sig []byte `ssh:"rest"` +} + +// publicKeyCallback is an AuthMethod that uses a set of key +// pairs for authentication. +type publicKeyCallback func() ([]Signer, error) + +func (cb publicKeyCallback) method() string { + return "publickey" +} + +func pickSignatureAlgorithm(signer Signer, extensions map[string][]byte) (MultiAlgorithmSigner, string, error) { + var as MultiAlgorithmSigner + keyFormat := signer.PublicKey().Type() + + // If the signer implements MultiAlgorithmSigner we use the algorithms it + // support, if it implements AlgorithmSigner we assume it supports all + // algorithms, otherwise only the key format one. + switch s := signer.(type) { + case MultiAlgorithmSigner: + as = s + case AlgorithmSigner: + as = &multiAlgorithmSigner{ + AlgorithmSigner: s, + supportedAlgorithms: algorithmsForKeyFormat(underlyingAlgo(keyFormat)), + } + default: + as = &multiAlgorithmSigner{ + AlgorithmSigner: algorithmSignerWrapper{signer}, + supportedAlgorithms: []string{underlyingAlgo(keyFormat)}, + } + } + + getFallbackAlgo := func() (string, error) { + // Fallback to use if there is no "server-sig-algs" extension or a + // common algorithm cannot be found. We use the public key format if the + // MultiAlgorithmSigner supports it, otherwise we return an error. + if !contains(as.Algorithms(), underlyingAlgo(keyFormat)) { + return "", fmt.Errorf("ssh: no common public key signature algorithm, server only supports %q for key type %q, signer only supports %v", + underlyingAlgo(keyFormat), keyFormat, as.Algorithms()) + } + return keyFormat, nil + } + + extPayload, ok := extensions["server-sig-algs"] + if !ok { + // If there is no "server-sig-algs" extension use the fallback + // algorithm. + algo, err := getFallbackAlgo() + return as, algo, err + } + + // The server-sig-algs extension only carries underlying signature + // algorithm, but we are trying to select a protocol-level public key + // algorithm, which might be a certificate type. Extend the list of server + // supported algorithms to include the corresponding certificate algorithms. + serverAlgos := strings.Split(string(extPayload), ",") + for _, algo := range serverAlgos { + if certAlgo, ok := certificateAlgo(algo); ok { + serverAlgos = append(serverAlgos, certAlgo) + } + } + + // Filter algorithms based on those supported by MultiAlgorithmSigner. + var keyAlgos []string + for _, algo := range algorithmsForKeyFormat(keyFormat) { + if contains(as.Algorithms(), underlyingAlgo(algo)) { + keyAlgos = append(keyAlgos, algo) + } + } + + algo, err := findCommon("public key signature algorithm", keyAlgos, serverAlgos) + if err != nil { + // If there is no overlap, return the fallback algorithm to support + // servers that fail to list all supported algorithms. + algo, err := getFallbackAlgo() + return as, algo, err + } + return as, algo, nil +} + +func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand io.Reader, extensions map[string][]byte) (authResult, []string, error) { + // Authentication is performed by sending an enquiry to test if a key is + // acceptable to the remote. If the key is acceptable, the client will + // attempt to authenticate with the valid key. If not the client will repeat + // the process with the remaining keys. + + signers, err := cb() + if err != nil { + return authFailure, nil, err + } + var methods []string + var errSigAlgo error + for _, signer := range signers { + pub := signer.PublicKey() + as, algo, err := pickSignatureAlgorithm(signer, extensions) + if err != nil && errSigAlgo == nil { + // If we cannot negotiate a signature algorithm store the first + // error so we can return it to provide a more meaningful message if + // no other signers work. + errSigAlgo = err + continue + } + ok, err := validateKey(pub, algo, user, c) + if err != nil { + return authFailure, nil, err + } + if !ok { + continue + } + + pubKey := pub.Marshal() + data := buildDataSignedForAuth(session, userAuthRequestMsg{ + User: user, + Service: serviceSSH, + Method: cb.method(), + }, algo, pubKey) + sign, err := as.SignWithAlgorithm(rand, data, underlyingAlgo(algo)) + if err != nil { + return authFailure, nil, err + } + + // manually wrap the serialized signature in a string + s := Marshal(sign) + sig := make([]byte, stringLength(len(s))) + marshalString(sig, s) + msg := publickeyAuthMsg{ + User: user, + Service: serviceSSH, + Method: cb.method(), + HasSig: true, + Algoname: algo, + PubKey: pubKey, + Sig: sig, + } + p := Marshal(&msg) + if err := c.writePacket(p); err != nil { + return authFailure, nil, err + } + var success authResult + success, methods, err = handleAuthResponse(c) + if err != nil { + return authFailure, nil, err + } + + // If authentication succeeds or the list of available methods does not + // contain the "publickey" method, do not attempt to authenticate with any + // other keys. According to RFC 4252 Section 7, the latter can occur when + // additional authentication methods are required. + if success == authSuccess || !contains(methods, cb.method()) { + return success, methods, err + } + } + + return authFailure, methods, errSigAlgo +} + +// validateKey validates the key provided is acceptable to the server. +func validateKey(key PublicKey, algo string, user string, c packetConn) (bool, error) { + pubKey := key.Marshal() + msg := publickeyAuthMsg{ + User: user, + Service: serviceSSH, + Method: "publickey", + HasSig: false, + Algoname: algo, + PubKey: pubKey, + } + if err := c.writePacket(Marshal(&msg)); err != nil { + return false, err + } + + return confirmKeyAck(key, algo, c) +} + +func confirmKeyAck(key PublicKey, algo string, c packetConn) (bool, error) { + pubKey := key.Marshal() + + for { + packet, err := c.readPacket() + if err != nil { + return false, err + } + switch packet[0] { + case msgUserAuthBanner: + if err := handleBannerResponse(c, packet); err != nil { + return false, err + } + case msgUserAuthPubKeyOk: + var msg userAuthPubKeyOkMsg + if err := Unmarshal(packet, &msg); err != nil { + return false, err + } + if msg.Algo != algo || !bytes.Equal(msg.PubKey, pubKey) { + return false, nil + } + return true, nil + case msgUserAuthFailure: + return false, nil + default: + return false, unexpectedMessageError(msgUserAuthPubKeyOk, packet[0]) + } + } +} + +// PublicKeys returns an AuthMethod that uses the given key +// pairs. +func PublicKeys(signers ...Signer) AuthMethod { + return publicKeyCallback(func() ([]Signer, error) { return signers, nil }) +} + +// PublicKeysCallback returns an AuthMethod that runs the given +// function to obtain a list of key pairs. +func PublicKeysCallback(getSigners func() (signers []Signer, err error)) AuthMethod { + return publicKeyCallback(getSigners) +} + +// handleAuthResponse returns whether the preceding authentication request succeeded +// along with a list of remaining authentication methods to try next and +// an error if an unexpected response was received. +func handleAuthResponse(c packetConn) (authResult, []string, error) { + gotMsgExtInfo := false + for { + packet, err := c.readPacket() + if err != nil { + return authFailure, nil, err + } + + switch packet[0] { + case msgUserAuthBanner: + if err := handleBannerResponse(c, packet); err != nil { + return authFailure, nil, err + } + case msgExtInfo: + // Ignore post-authentication RFC 8308 extensions, once. + if gotMsgExtInfo { + return authFailure, nil, unexpectedMessageError(msgUserAuthSuccess, packet[0]) + } + gotMsgExtInfo = true + case msgUserAuthFailure: + var msg userAuthFailureMsg + if err := Unmarshal(packet, &msg); err != nil { + return authFailure, nil, err + } + if msg.PartialSuccess { + return authPartialSuccess, msg.Methods, nil + } + return authFailure, msg.Methods, nil + case msgUserAuthSuccess: + return authSuccess, nil, nil + default: + return authFailure, nil, unexpectedMessageError(msgUserAuthSuccess, packet[0]) + } + } +} + +func handleBannerResponse(c packetConn, packet []byte) error { + var msg userAuthBannerMsg + if err := Unmarshal(packet, &msg); err != nil { + return err + } + + transport, ok := c.(*handshakeTransport) + if !ok { + return nil + } + + if transport.bannerCallback != nil { + return transport.bannerCallback(msg.Message) + } + + return nil +} + +// KeyboardInteractiveChallenge should print questions, optionally +// disabling echoing (e.g. for passwords), and return all the answers. +// Challenge may be called multiple times in a single session. After +// successful authentication, the server may send a challenge with no +// questions, for which the name and instruction messages should be +// printed. RFC 4256 section 3.3 details how the UI should behave for +// both CLI and GUI environments. +type KeyboardInteractiveChallenge func(name, instruction string, questions []string, echos []bool) (answers []string, err error) + +// KeyboardInteractive returns an AuthMethod using a prompt/response +// sequence controlled by the server. +func KeyboardInteractive(challenge KeyboardInteractiveChallenge) AuthMethod { + return challenge +} + +func (cb KeyboardInteractiveChallenge) method() string { + return "keyboard-interactive" +} + +func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packetConn, rand io.Reader, _ map[string][]byte) (authResult, []string, error) { + type initiateMsg struct { + User string `sshtype:"50"` + Service string + Method string + Language string + Submethods string + } + + if err := c.writePacket(Marshal(&initiateMsg{ + User: user, + Service: serviceSSH, + Method: "keyboard-interactive", + })); err != nil { + return authFailure, nil, err + } + + gotMsgExtInfo := false + for { + packet, err := c.readPacket() + if err != nil { + return authFailure, nil, err + } + + // like handleAuthResponse, but with less options. + switch packet[0] { + case msgUserAuthBanner: + if err := handleBannerResponse(c, packet); err != nil { + return authFailure, nil, err + } + continue + case msgExtInfo: + // Ignore post-authentication RFC 8308 extensions, once. + if gotMsgExtInfo { + return authFailure, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0]) + } + gotMsgExtInfo = true + continue + case msgUserAuthInfoRequest: + // OK + case msgUserAuthFailure: + var msg userAuthFailureMsg + if err := Unmarshal(packet, &msg); err != nil { + return authFailure, nil, err + } + if msg.PartialSuccess { + return authPartialSuccess, msg.Methods, nil + } + return authFailure, msg.Methods, nil + case msgUserAuthSuccess: + return authSuccess, nil, nil + default: + return authFailure, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0]) + } + + var msg userAuthInfoRequestMsg + if err := Unmarshal(packet, &msg); err != nil { + return authFailure, nil, err + } + + // Manually unpack the prompt/echo pairs. + rest := msg.Prompts + var prompts []string + var echos []bool + for i := 0; i < int(msg.NumPrompts); i++ { + prompt, r, ok := parseString(rest) + if !ok || len(r) == 0 { + return authFailure, nil, errors.New("ssh: prompt format error") + } + prompts = append(prompts, string(prompt)) + echos = append(echos, r[0] != 0) + rest = r[1:] + } + + if len(rest) != 0 { + return authFailure, nil, errors.New("ssh: extra data following keyboard-interactive pairs") + } + + answers, err := cb(msg.Name, msg.Instruction, prompts, echos) + if err != nil { + return authFailure, nil, err + } + + if len(answers) != len(prompts) { + return authFailure, nil, fmt.Errorf("ssh: incorrect number of answers from keyboard-interactive callback %d (expected %d)", len(answers), len(prompts)) + } + responseLength := 1 + 4 + for _, a := range answers { + responseLength += stringLength(len(a)) + } + serialized := make([]byte, responseLength) + p := serialized + p[0] = msgUserAuthInfoResponse + p = p[1:] + p = marshalUint32(p, uint32(len(answers))) + for _, a := range answers { + p = marshalString(p, []byte(a)) + } + + if err := c.writePacket(serialized); err != nil { + return authFailure, nil, err + } + } +} + +type retryableAuthMethod struct { + authMethod AuthMethod + maxTries int +} + +func (r *retryableAuthMethod) auth(session []byte, user string, c packetConn, rand io.Reader, extensions map[string][]byte) (ok authResult, methods []string, err error) { + for i := 0; r.maxTries <= 0 || i < r.maxTries; i++ { + ok, methods, err = r.authMethod.auth(session, user, c, rand, extensions) + if ok != authFailure || err != nil { // either success, partial success or error terminate + return ok, methods, err + } + } + return ok, methods, err +} + +func (r *retryableAuthMethod) method() string { + return r.authMethod.method() +} + +// RetryableAuthMethod is a decorator for other auth methods enabling them to +// be retried up to maxTries before considering that AuthMethod itself failed. +// If maxTries is <= 0, will retry indefinitely +// +// This is useful for interactive clients using challenge/response type +// authentication (e.g. Keyboard-Interactive, Password, etc) where the user +// could mistype their response resulting in the server issuing a +// SSH_MSG_USERAUTH_FAILURE (rfc4252 #8 [password] and rfc4256 #3.4 +// [keyboard-interactive]); Without this decorator, the non-retryable +// AuthMethod would be removed from future consideration, and never tried again +// (and so the user would never be able to retry their entry). +func RetryableAuthMethod(auth AuthMethod, maxTries int) AuthMethod { + return &retryableAuthMethod{authMethod: auth, maxTries: maxTries} +} + +// GSSAPIWithMICAuthMethod is an AuthMethod with "gssapi-with-mic" authentication. +// See RFC 4462 section 3 +// gssAPIClient is implementation of the GSSAPIClient interface, see the definition of the interface for details. +// target is the server host you want to log in to. +func GSSAPIWithMICAuthMethod(gssAPIClient GSSAPIClient, target string) AuthMethod { + if gssAPIClient == nil { + panic("gss-api client must be not nil with enable gssapi-with-mic") + } + return &gssAPIWithMICCallback{gssAPIClient: gssAPIClient, target: target} +} + +type gssAPIWithMICCallback struct { + gssAPIClient GSSAPIClient + target string +} + +func (g *gssAPIWithMICCallback) auth(session []byte, user string, c packetConn, rand io.Reader, _ map[string][]byte) (authResult, []string, error) { + m := &userAuthRequestMsg{ + User: user, + Service: serviceSSH, + Method: g.method(), + } + // The GSS-API authentication method is initiated when the client sends an SSH_MSG_USERAUTH_REQUEST. + // See RFC 4462 section 3.2. + m.Payload = appendU32(m.Payload, 1) + m.Payload = appendString(m.Payload, string(krb5OID)) + if err := c.writePacket(Marshal(m)); err != nil { + return authFailure, nil, err + } + // The server responds to the SSH_MSG_USERAUTH_REQUEST with either an + // SSH_MSG_USERAUTH_FAILURE if none of the mechanisms are supported or + // with an SSH_MSG_USERAUTH_GSSAPI_RESPONSE. + // See RFC 4462 section 3.3. + // OpenSSH supports Kerberos V5 mechanism only for GSS-API authentication,so I don't want to check + // selected mech if it is valid. + packet, err := c.readPacket() + if err != nil { + return authFailure, nil, err + } + userAuthGSSAPIResp := &userAuthGSSAPIResponse{} + if err := Unmarshal(packet, userAuthGSSAPIResp); err != nil { + return authFailure, nil, err + } + // Start the loop into the exchange token. + // See RFC 4462 section 3.4. + var token []byte + defer g.gssAPIClient.DeleteSecContext() + for { + // Initiates the establishment of a security context between the application and a remote peer. + nextToken, needContinue, err := g.gssAPIClient.InitSecContext("host@"+g.target, token, false) + if err != nil { + return authFailure, nil, err + } + if len(nextToken) > 0 { + if err := c.writePacket(Marshal(&userAuthGSSAPIToken{ + Token: nextToken, + })); err != nil { + return authFailure, nil, err + } + } + if !needContinue { + break + } + packet, err = c.readPacket() + if err != nil { + return authFailure, nil, err + } + switch packet[0] { + case msgUserAuthFailure: + var msg userAuthFailureMsg + if err := Unmarshal(packet, &msg); err != nil { + return authFailure, nil, err + } + if msg.PartialSuccess { + return authPartialSuccess, msg.Methods, nil + } + return authFailure, msg.Methods, nil + case msgUserAuthGSSAPIError: + userAuthGSSAPIErrorResp := &userAuthGSSAPIError{} + if err := Unmarshal(packet, userAuthGSSAPIErrorResp); err != nil { + return authFailure, nil, err + } + return authFailure, nil, fmt.Errorf("GSS-API Error:\n"+ + "Major Status: %d\n"+ + "Minor Status: %d\n"+ + "Error Message: %s\n", userAuthGSSAPIErrorResp.MajorStatus, userAuthGSSAPIErrorResp.MinorStatus, + userAuthGSSAPIErrorResp.Message) + case msgUserAuthGSSAPIToken: + userAuthGSSAPITokenReq := &userAuthGSSAPIToken{} + if err := Unmarshal(packet, userAuthGSSAPITokenReq); err != nil { + return authFailure, nil, err + } + token = userAuthGSSAPITokenReq.Token + } + } + // Binding Encryption Keys. + // See RFC 4462 section 3.5. + micField := buildMIC(string(session), user, "ssh-connection", "gssapi-with-mic") + micToken, err := g.gssAPIClient.GetMIC(micField) + if err != nil { + return authFailure, nil, err + } + if err := c.writePacket(Marshal(&userAuthGSSAPIMIC{ + MIC: micToken, + })); err != nil { + return authFailure, nil, err + } + return handleAuthResponse(c) +} + +func (g *gssAPIWithMICCallback) method() string { + return "gssapi-with-mic" +} diff --git a/pkg/proto/ssh/common.go b/pkg/proto/ssh/common.go new file mode 100644 index 0000000..dd2ab0d --- /dev/null +++ b/pkg/proto/ssh/common.go @@ -0,0 +1,468 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "crypto" + "crypto/rand" + "fmt" + "io" + "math" + "sync" + + _ "crypto/sha1" + _ "crypto/sha256" + _ "crypto/sha512" +) + +// These are string constants in the SSH protocol. +const ( + compressionNone = "none" + serviceUserAuth = "ssh-userauth" + serviceSSH = "ssh-connection" +) + +// supportedCiphers lists ciphers we support but might not recommend. +var supportedCiphers = []string{ + "aes128-ctr", "aes192-ctr", "aes256-ctr", + "aes128-gcm@openssh.com", gcm256CipherID, + chacha20Poly1305ID, + "arcfour256", "arcfour128", "arcfour", + aes128cbcID, + tripledescbcID, +} + +// preferredCiphers specifies the default preference for ciphers. +var preferredCiphers = []string{ + "aes128-gcm@openssh.com", gcm256CipherID, + chacha20Poly1305ID, + "aes128-ctr", "aes192-ctr", "aes256-ctr", +} + +// supportedKexAlgos specifies the supported key-exchange algorithms in +// preference order. +var supportedKexAlgos = []string{ + kexAlgoCurve25519SHA256, kexAlgoCurve25519SHA256LibSSH, + // P384 and P521 are not constant-time yet, but since we don't + // reuse ephemeral keys, using them for ECDH should be OK. + kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521, + kexAlgoDH14SHA256, kexAlgoDH16SHA512, kexAlgoDH14SHA1, + kexAlgoDH1SHA1, +} + +// serverForbiddenKexAlgos contains key exchange algorithms, that are forbidden +// for the server half. +var serverForbiddenKexAlgos = map[string]struct{}{ + kexAlgoDHGEXSHA1: {}, // server half implementation is only minimal to satisfy the automated tests + kexAlgoDHGEXSHA256: {}, // server half implementation is only minimal to satisfy the automated tests +} + +// preferredKexAlgos specifies the default preference for key-exchange +// algorithms in preference order. The diffie-hellman-group16-sha512 algorithm +// is disabled by default because it is a bit slower than the others. +var preferredKexAlgos = []string{ + kexAlgoCurve25519SHA256, kexAlgoCurve25519SHA256LibSSH, + kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521, + kexAlgoDH14SHA256, kexAlgoDH14SHA1, +} + +// supportedHostKeyAlgos specifies the supported host-key algorithms (i.e. methods +// of authenticating servers) in preference order. +var supportedHostKeyAlgos = []string{ + CertAlgoRSASHA256v01, CertAlgoRSASHA512v01, + CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, + CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoED25519v01, + + KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521, + KeyAlgoRSASHA256, KeyAlgoRSASHA512, + KeyAlgoRSA, KeyAlgoDSA, + + KeyAlgoED25519, +} + +// supportedMACs specifies a default set of MAC algorithms in preference order. +// This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed +// because they have reached the end of their useful life. +var supportedMACs = []string{ + "hmac-sha2-256-etm@openssh.com", "hmac-sha2-512-etm@openssh.com", "hmac-sha2-256", "hmac-sha2-512", "hmac-sha1", "hmac-sha1-96", +} + +var supportedCompressions = []string{compressionNone} + +// hashFuncs keeps the mapping of supported signature algorithms to their +// respective hashes needed for signing and verification. +var hashFuncs = map[string]crypto.Hash{ + KeyAlgoRSA: crypto.SHA1, + KeyAlgoRSASHA256: crypto.SHA256, + KeyAlgoRSASHA512: crypto.SHA512, + KeyAlgoDSA: crypto.SHA1, + KeyAlgoECDSA256: crypto.SHA256, + KeyAlgoECDSA384: crypto.SHA384, + KeyAlgoECDSA521: crypto.SHA512, + // KeyAlgoED25519 doesn't pre-hash. + KeyAlgoSKECDSA256: crypto.SHA256, + KeyAlgoSKED25519: crypto.SHA256, +} + +// algorithmsForKeyFormat returns the supported signature algorithms for a given +// public key format (PublicKey.Type), in order of preference. See RFC 8332, +// Section 2. See also the note in sendKexInit on backwards compatibility. +func algorithmsForKeyFormat(keyFormat string) []string { + switch keyFormat { + case KeyAlgoRSA: + return []string{KeyAlgoRSASHA256, KeyAlgoRSASHA512, KeyAlgoRSA} + case CertAlgoRSAv01: + return []string{CertAlgoRSASHA256v01, CertAlgoRSASHA512v01, CertAlgoRSAv01} + default: + return []string{keyFormat} + } +} + +// isRSA returns whether algo is a supported RSA algorithm, including certificate +// algorithms. +func isRSA(algo string) bool { + algos := algorithmsForKeyFormat(KeyAlgoRSA) + return contains(algos, underlyingAlgo(algo)) +} + +// supportedPubKeyAuthAlgos specifies the supported client public key +// authentication algorithms. Note that this doesn't include certificate types +// since those use the underlying algorithm. This list is sent to the client if +// it supports the server-sig-algs extension. Order is irrelevant. +var supportedPubKeyAuthAlgos = []string{ + KeyAlgoED25519, + KeyAlgoSKED25519, KeyAlgoSKECDSA256, + KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521, + KeyAlgoRSASHA256, KeyAlgoRSASHA512, KeyAlgoRSA, + KeyAlgoDSA, +} + +// unexpectedMessageError results when the SSH message that we received didn't +// match what we wanted. +func unexpectedMessageError(expected, got uint8) error { + return fmt.Errorf("ssh: unexpected message type %d (expected %d)", got, expected) +} + +// parseError results from a malformed SSH message. +func parseError(tag uint8) error { + return fmt.Errorf("ssh: parse error in message type %d", tag) +} + +func findCommon(what string, client []string, server []string) (common string, err error) { + for _, c := range client { + for _, s := range server { + if c == s { + return c, nil + } + } + } + return "", fmt.Errorf("ssh: no common algorithm for %s; client offered: %v, server offered: %v", what, client, server) +} + +// directionAlgorithms records algorithm choices in one direction (either read or write) +type directionAlgorithms struct { + Cipher string + MAC string + Compression string +} + +// rekeyBytes returns a rekeying intervals in bytes. +func (a *directionAlgorithms) rekeyBytes() int64 { + // According to RFC 4344 block ciphers should rekey after + // 2^(BLOCKSIZE/4) blocks. For all AES flavors BLOCKSIZE is + // 128. + switch a.Cipher { + case "aes128-ctr", "aes192-ctr", "aes256-ctr", gcm128CipherID, gcm256CipherID, aes128cbcID: + return 16 * (1 << 32) + + } + + // For others, stick with RFC 4253 recommendation to rekey after 1 Gb of data. + return 1 << 30 +} + +var aeadCiphers = map[string]bool{ + gcm128CipherID: true, + gcm256CipherID: true, + chacha20Poly1305ID: true, +} + +type algorithms struct { + kex string + hostKey string + w directionAlgorithms + r directionAlgorithms +} + +func findAgreedAlgorithms(isClient bool, clientKexInit, serverKexInit *kexInitMsg) (algs *algorithms, err error) { + result := &algorithms{} + + result.kex, err = findCommon("key exchange", clientKexInit.KexAlgos, serverKexInit.KexAlgos) + if err != nil { + return + } + + result.hostKey, err = findCommon("host key", clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos) + if err != nil { + return + } + + stoc, ctos := &result.w, &result.r + if isClient { + ctos, stoc = stoc, ctos + } + + ctos.Cipher, err = findCommon("client to server cipher", clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer) + if err != nil { + return + } + + stoc.Cipher, err = findCommon("server to client cipher", clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient) + if err != nil { + return + } + + if !aeadCiphers[ctos.Cipher] { + ctos.MAC, err = findCommon("client to server MAC", clientKexInit.MACsClientServer, serverKexInit.MACsClientServer) + if err != nil { + return + } + } + + if !aeadCiphers[stoc.Cipher] { + stoc.MAC, err = findCommon("server to client MAC", clientKexInit.MACsServerClient, serverKexInit.MACsServerClient) + if err != nil { + return + } + } + + ctos.Compression, err = findCommon("client to server compression", clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer) + if err != nil { + return + } + + stoc.Compression, err = findCommon("server to client compression", clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient) + if err != nil { + return + } + + return result, nil +} + +// If rekeythreshold is too small, we can't make any progress sending +// stuff. +const minRekeyThreshold uint64 = 256 + +// Config contains configuration data common to both ServerConfig and +// ClientConfig. +type Config struct { + // Rand provides the source of entropy for cryptographic + // primitives. If Rand is nil, the cryptographic random reader + // in package crypto/rand will be used. + Rand io.Reader + + // The maximum number of bytes sent or received after which a + // new key is negotiated. It must be at least 256. If + // unspecified, a size suitable for the chosen cipher is used. + RekeyThreshold uint64 + + // The allowed key exchanges algorithms. If unspecified then a default set + // of algorithms is used. Unsupported values are silently ignored. + KeyExchanges []string + + // The allowed cipher algorithms. If unspecified then a sensible default is + // used. Unsupported values are silently ignored. + Ciphers []string + + // The allowed MAC algorithms. If unspecified then a sensible default is + // used. Unsupported values are silently ignored. + MACs []string +} + +// SetDefaults sets sensible values for unset fields in config. This is +// exported for testing: Configs passed to SSH functions are copied and have +// default values set automatically. +func (c *Config) SetDefaults() { + if c.Rand == nil { + c.Rand = rand.Reader + } + if c.Ciphers == nil { + c.Ciphers = preferredCiphers + } + var ciphers []string + for _, c := range c.Ciphers { + if cipherModes[c] != nil { + // Ignore the cipher if we have no cipherModes definition. + ciphers = append(ciphers, c) + } + } + c.Ciphers = ciphers + + if c.KeyExchanges == nil { + c.KeyExchanges = preferredKexAlgos + } + var kexs []string + for _, k := range c.KeyExchanges { + if kexAlgoMap[k] != nil { + // Ignore the KEX if we have no kexAlgoMap definition. + kexs = append(kexs, k) + } + } + c.KeyExchanges = kexs + + if c.MACs == nil { + c.MACs = supportedMACs + } + var macs []string + for _, m := range c.MACs { + if macModes[m] != nil { + // Ignore the MAC if we have no macModes definition. + macs = append(macs, m) + } + } + c.MACs = macs + + if c.RekeyThreshold == 0 { + // cipher specific default + } else if c.RekeyThreshold < minRekeyThreshold { + c.RekeyThreshold = minRekeyThreshold + } else if c.RekeyThreshold >= math.MaxInt64 { + // Avoid weirdness if somebody uses -1 as a threshold. + c.RekeyThreshold = math.MaxInt64 + } +} + +// buildDataSignedForAuth returns the data that is signed in order to prove +// possession of a private key. See RFC 4252, section 7. algo is the advertised +// algorithm, and may be a certificate type. +func buildDataSignedForAuth(sessionID []byte, req userAuthRequestMsg, algo string, pubKey []byte) []byte { + data := struct { + Session []byte + Type byte + User string + Service string + Method string + Sign bool + Algo string + PubKey []byte + }{ + sessionID, + msgUserAuthRequest, + req.User, + req.Service, + req.Method, + true, + algo, + pubKey, + } + return Marshal(data) +} + +func appendU16(buf []byte, n uint16) []byte { + return append(buf, byte(n>>8), byte(n)) +} + +func appendU32(buf []byte, n uint32) []byte { + return append(buf, byte(n>>24), byte(n>>16), byte(n>>8), byte(n)) +} + +func appendU64(buf []byte, n uint64) []byte { + return append(buf, + byte(n>>56), byte(n>>48), byte(n>>40), byte(n>>32), + byte(n>>24), byte(n>>16), byte(n>>8), byte(n)) +} + +func appendInt(buf []byte, n int) []byte { + return appendU32(buf, uint32(n)) +} + +func appendString(buf []byte, s string) []byte { + buf = appendU32(buf, uint32(len(s))) + buf = append(buf, s...) + return buf +} + +func appendBool(buf []byte, b bool) []byte { + if b { + return append(buf, 1) + } + return append(buf, 0) +} + +// newCond is a helper to hide the fact that there is no usable zero +// value for sync.Cond. +func newCond() *sync.Cond { return sync.NewCond(new(sync.Mutex)) } + +// window represents the buffer available to clients +// wishing to write to a channel. +type window struct { + *sync.Cond + win uint32 // RFC 4254 5.2 says the window size can grow to 2^32-1 + writeWaiters int + closed bool +} + +// add adds win to the amount of window available +// for consumers. +func (w *window) add(win uint32) bool { + // a zero sized window adjust is a noop. + if win == 0 { + return true + } + w.L.Lock() + if w.win+win < win { + w.L.Unlock() + return false + } + w.win += win + // It is unusual that multiple goroutines would be attempting to reserve + // window space, but not guaranteed. Use broadcast to notify all waiters + // that additional window is available. + w.Broadcast() + w.L.Unlock() + return true +} + +// close sets the window to closed, so all reservations fail +// immediately. +func (w *window) close() { + w.L.Lock() + w.closed = true + w.Broadcast() + w.L.Unlock() +} + +// reserve reserves win from the available window capacity. +// If no capacity remains, reserve will block. reserve may +// return less than requested. +func (w *window) reserve(win uint32) (uint32, error) { + var err error + w.L.Lock() + w.writeWaiters++ + w.Broadcast() + for w.win == 0 && !w.closed { + w.Wait() + } + w.writeWaiters-- + if w.win < win { + win = w.win + } + w.win -= win + if w.closed { + err = io.EOF + } + w.L.Unlock() + return win, err +} + +// waitWriterBlocked waits until some goroutine is blocked for further +// writes. It is used in tests only. +func (w *window) waitWriterBlocked() { + w.Cond.L.Lock() + for w.writeWaiters == 0 { + w.Cond.Wait() + } + w.Cond.L.Unlock() +} diff --git a/pkg/proto/ssh/connection.go b/pkg/proto/ssh/connection.go new file mode 100644 index 0000000..8f345ee --- /dev/null +++ b/pkg/proto/ssh/connection.go @@ -0,0 +1,143 @@ +// Copyright 2013 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "fmt" + "net" +) + +// OpenChannelError is returned if the other side rejects an +// OpenChannel request. +type OpenChannelError struct { + Reason RejectionReason + Message string +} + +func (e *OpenChannelError) Error() string { + return fmt.Sprintf("ssh: rejected: %s (%s)", e.Reason, e.Message) +} + +// ConnMetadata holds metadata for the connection. +type ConnMetadata interface { + // User returns the user ID for this connection. + User() string + + // SessionID returns the session hash, also denoted by H. + SessionID() []byte + + // ClientVersion returns the client's version string as hashed + // into the session ID. + ClientVersion() []byte + + // ServerVersion returns the server's version string as hashed + // into the session ID. + ServerVersion() []byte + + // RemoteAddr returns the remote address for this connection. + RemoteAddr() net.Addr + + // LocalAddr returns the local address for this connection. + LocalAddr() net.Addr +} + +// Conn represents an SSH connection for both server and client roles. +// Conn is the basis for implementing an application layer, such +// as ClientConn, which implements the traditional shell access for +// clients. +type Conn interface { + ConnMetadata + + // SendRequest sends a global request, and returns the + // reply. If wantReply is true, it returns the response status + // and payload. See also RFC 4254, section 4. + SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error) + + // OpenChannel tries to open an channel. If the request is + // rejected, it returns *OpenChannelError. On success it returns + // the SSH Channel and a Go channel for incoming, out-of-band + // requests. The Go channel must be serviced, or the + // connection will hang. + OpenChannel(name string, data []byte) (Channel, <-chan *Request, error) + + // Close closes the underlying network connection + Close() error + + // Wait blocks until the connection has shut down, and returns the + // error causing the shutdown. + Wait() error + + // TODO(hanwen): consider exposing: + // RequestKeyChange + // Disconnect +} + +// DiscardRequests consumes and rejects all requests from the +// passed-in channel. +func DiscardRequests(in <-chan *Request) { + for req := range in { + if req.WantReply { + req.Reply(false, nil) + } + } +} + +// A connection represents an incoming connection. +type connection struct { + transport *handshakeTransport + sshConn + + // The connection protocol. + *mux +} + +func (c *connection) Close() error { + return c.sshConn.conn.Close() +} + +// sshConn provides net.Conn metadata, but disallows direct reads and +// writes. +type sshConn struct { + conn net.Conn + + user string + sessionID []byte + clientVersion []byte + serverVersion []byte +} + +func dup(src []byte) []byte { + dst := make([]byte, len(src)) + copy(dst, src) + return dst +} + +func (c *sshConn) User() string { + return c.user +} + +func (c *sshConn) RemoteAddr() net.Addr { + return c.conn.RemoteAddr() +} + +func (c *sshConn) Close() error { + return c.conn.Close() +} + +func (c *sshConn) LocalAddr() net.Addr { + return c.conn.LocalAddr() +} + +func (c *sshConn) SessionID() []byte { + return dup(c.sessionID) +} + +func (c *sshConn) ClientVersion() []byte { + return dup(c.clientVersion) +} + +func (c *sshConn) ServerVersion() []byte { + return dup(c.serverVersion) +} diff --git a/pkg/proto/ssh/doc.go b/pkg/proto/ssh/doc.go new file mode 100644 index 0000000..fbda266 --- /dev/null +++ b/pkg/proto/ssh/doc.go @@ -0,0 +1,23 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +/* +Package ssh implements an SSH client and server. + +SSH is a transport security protocol, an authentication protocol and a +family of application protocols. The most typical application level +protocol is a remote shell and this is specifically implemented. However, +the multiplexed nature of SSH is exposed to users that wish to support +others. + +References: + + [PROTOCOL]: https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL?rev=HEAD + [PROTOCOL.certkeys]: http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.certkeys?rev=HEAD + [SSH-PARAMETERS]: http://www.iana.org/assignments/ssh-parameters/ssh-parameters.xml#ssh-parameters-1 + +This package does not fall under the stability promise of the Go language itself, +so its API may be changed when pressing needs arise. +*/ +package ssh // import "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" diff --git a/pkg/proto/ssh/handshake.go b/pkg/proto/ssh/handshake.go new file mode 100644 index 0000000..49bbba7 --- /dev/null +++ b/pkg/proto/ssh/handshake.go @@ -0,0 +1,758 @@ +// Copyright 2013 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "crypto/rand" + "errors" + "fmt" + "io" + "log" + "net" + "strings" + "sync" +) + +// debugHandshake, if set, prints messages sent and received. Key +// exchange messages are printed as if DH were used, so the debug +// messages are wrong when using ECDH. +const debugHandshake = false + +// chanSize sets the amount of buffering SSH connections. This is +// primarily for testing: setting chanSize=0 uncovers deadlocks more +// quickly. +const chanSize = 16 + +// keyingTransport is a packet based transport that supports key +// changes. It need not be thread-safe. It should pass through +// msgNewKeys in both directions. +type keyingTransport interface { + packetConn + + // prepareKeyChange sets up a key change. The key change for a + // direction will be effected if a msgNewKeys message is sent + // or received. + prepareKeyChange(*algorithms, *kexResult) error +} + +// handshakeTransport implements rekeying on top of a keyingTransport +// and offers a thread-safe writePacket() interface. +type handshakeTransport struct { + conn keyingTransport + config *Config + + serverVersion []byte + clientVersion []byte + + // hostKeys is non-empty if we are the server. In that case, + // it contains all host keys that can be used to sign the + // connection. + hostKeys []Signer + + // publicKeyAuthAlgorithms is non-empty if we are the server. In that case, + // it contains the supported client public key authentication algorithms. + publicKeyAuthAlgorithms []string + + // hostKeyAlgorithms is non-empty if we are the client. In that case, + // we accept these key types from the server as host key. + hostKeyAlgorithms []string + + // On read error, incoming is closed, and readError is set. + incoming chan []byte + readError error + + mu sync.Mutex + writeError error + sentInitPacket []byte + sentInitMsg *kexInitMsg + pendingPackets [][]byte // Used when a key exchange is in progress. + writePacketsLeft uint32 + writeBytesLeft int64 + + // If the read loop wants to schedule a kex, it pings this + // channel, and the write loop will send out a kex + // message. + requestKex chan struct{} + + // If the other side requests or confirms a kex, its kexInit + // packet is sent here for the write loop to find it. + startKex chan *pendingKex + kexLoopDone chan struct{} // closed (with writeError non-nil) when kexLoop exits + + // data for host key checking + hostKeyCallback HostKeyCallback + dialAddress string + remoteAddr net.Addr + + // bannerCallback is non-empty if we are the client and it has been set in + // ClientConfig. In that case it is called during the user authentication + // dance to handle a custom server's message. + bannerCallback BannerCallback + + // Algorithms agreed in the last key exchange. + algorithms *algorithms + + // Counters exclusively owned by readLoop. + readPacketsLeft uint32 + readBytesLeft int64 + + // The session ID or nil if first kex did not complete yet. + sessionID []byte +} + +type pendingKex struct { + otherInit []byte + done chan error +} + +func newHandshakeTransport(conn keyingTransport, config *Config, clientVersion, serverVersion []byte) *handshakeTransport { + t := &handshakeTransport{ + conn: conn, + serverVersion: serverVersion, + clientVersion: clientVersion, + incoming: make(chan []byte, chanSize), + requestKex: make(chan struct{}, 1), + startKex: make(chan *pendingKex), + kexLoopDone: make(chan struct{}), + + config: config, + } + t.resetReadThresholds() + t.resetWriteThresholds() + + // We always start with a mandatory key exchange. + t.requestKex <- struct{}{} + return t +} + +func newClientTransport(conn keyingTransport, clientVersion, serverVersion []byte, config *ClientConfig, dialAddr string, addr net.Addr) *handshakeTransport { + t := newHandshakeTransport(conn, &config.Config, clientVersion, serverVersion) + t.dialAddress = dialAddr + t.remoteAddr = addr + t.hostKeyCallback = config.HostKeyCallback + t.bannerCallback = config.BannerCallback + if config.HostKeyAlgorithms != nil { + t.hostKeyAlgorithms = config.HostKeyAlgorithms + } else { + t.hostKeyAlgorithms = supportedHostKeyAlgos + } + go t.readLoop() + go t.kexLoop() + return t +} + +func newServerTransport(conn keyingTransport, clientVersion, serverVersion []byte, config *ServerConfig) *handshakeTransport { + t := newHandshakeTransport(conn, &config.Config, clientVersion, serverVersion) + t.hostKeys = config.hostKeys + t.publicKeyAuthAlgorithms = config.PublicKeyAuthAlgorithms + go t.readLoop() + go t.kexLoop() + return t +} + +func (t *handshakeTransport) getSessionID() []byte { + return t.sessionID +} + +// waitSession waits for the session to be established. This should be +// the first thing to call after instantiating handshakeTransport. +func (t *handshakeTransport) waitSession() error { + p, err := t.readPacket() + if err != nil { + return err + } + if p[0] != msgNewKeys { + return fmt.Errorf("ssh: first packet should be msgNewKeys") + } + + return nil +} + +func (t *handshakeTransport) id() string { + if len(t.hostKeys) > 0 { + return "server" + } + return "client" +} + +func (t *handshakeTransport) printPacket(p []byte, write bool) { + action := "got" + if write { + action = "sent" + } + + if p[0] == msgChannelData || p[0] == msgChannelExtendedData { + log.Printf("%s %s data (packet %d bytes)", t.id(), action, len(p)) + } else { + msg, err := decode(p) + log.Printf("%s %s %T %v (%v)", t.id(), action, msg, msg, err) + } +} + +func (t *handshakeTransport) readPacket() ([]byte, error) { + p, ok := <-t.incoming + if !ok { + return nil, t.readError + } + return p, nil +} + +func (t *handshakeTransport) readLoop() { + first := true + for { + p, err := t.readOnePacket(first) + first = false + if err != nil { + t.readError = err + close(t.incoming) + break + } + if p[0] == msgIgnore || p[0] == msgDebug { + continue + } + t.incoming <- p + } + + // Stop writers too. + t.recordWriteError(t.readError) + + // Unblock the writer should it wait for this. + close(t.startKex) + + // Don't close t.requestKex; it's also written to from writePacket. +} + +func (t *handshakeTransport) pushPacket(p []byte) error { + if debugHandshake { + t.printPacket(p, true) + } + return t.conn.writePacket(p) +} + +func (t *handshakeTransport) getWriteError() error { + t.mu.Lock() + defer t.mu.Unlock() + return t.writeError +} + +func (t *handshakeTransport) recordWriteError(err error) { + t.mu.Lock() + defer t.mu.Unlock() + if t.writeError == nil && err != nil { + t.writeError = err + } +} + +func (t *handshakeTransport) requestKeyExchange() { + select { + case t.requestKex <- struct{}{}: + default: + // something already requested a kex, so do nothing. + } +} + +func (t *handshakeTransport) resetWriteThresholds() { + t.writePacketsLeft = packetRekeyThreshold + if t.config.RekeyThreshold > 0 { + t.writeBytesLeft = int64(t.config.RekeyThreshold) + } else if t.algorithms != nil { + t.writeBytesLeft = t.algorithms.w.rekeyBytes() + } else { + t.writeBytesLeft = 1 << 30 + } +} + +func (t *handshakeTransport) kexLoop() { + +write: + for t.getWriteError() == nil { + var request *pendingKex + var sent bool + + for request == nil || !sent { + var ok bool + select { + case request, ok = <-t.startKex: + if !ok { + break write + } + case <-t.requestKex: + break + } + + if !sent { + if err := t.sendKexInit(); err != nil { + t.recordWriteError(err) + break + } + sent = true + } + } + + if err := t.getWriteError(); err != nil { + if request != nil { + request.done <- err + } + break + } + + // We're not servicing t.requestKex, but that is OK: + // we never block on sending to t.requestKex. + + // We're not servicing t.startKex, but the remote end + // has just sent us a kexInitMsg, so it can't send + // another key change request, until we close the done + // channel on the pendingKex request. + + err := t.enterKeyExchange(request.otherInit) + + t.mu.Lock() + t.writeError = err + t.sentInitPacket = nil + t.sentInitMsg = nil + + t.resetWriteThresholds() + + // we have completed the key exchange. Since the + // reader is still blocked, it is safe to clear out + // the requestKex channel. This avoids the situation + // where: 1) we consumed our own request for the + // initial kex, and 2) the kex from the remote side + // caused another send on the requestKex channel, + clear: + for { + select { + case <-t.requestKex: + // + default: + break clear + } + } + + request.done <- t.writeError + + // kex finished. Push packets that we received while + // the kex was in progress. Don't look at t.startKex + // and don't increment writtenSinceKex: if we trigger + // another kex while we are still busy with the last + // one, things will become very confusing. + for _, p := range t.pendingPackets { + t.writeError = t.pushPacket(p) + if t.writeError != nil { + break + } + } + t.pendingPackets = t.pendingPackets[:0] + t.mu.Unlock() + } + + // Unblock reader. + t.conn.Close() + + // drain startKex channel. We don't service t.requestKex + // because nobody does blocking sends there. + for request := range t.startKex { + request.done <- t.getWriteError() + } + + // Mark that the loop is done so that Close can return. + close(t.kexLoopDone) +} + +// The protocol uses uint32 for packet counters, so we can't let them +// reach 1<<32. We will actually read and write more packets than +// this, though: the other side may send more packets, and after we +// hit this limit on writing we will send a few more packets for the +// key exchange itself. +const packetRekeyThreshold = (1 << 31) + +func (t *handshakeTransport) resetReadThresholds() { + t.readPacketsLeft = packetRekeyThreshold + if t.config.RekeyThreshold > 0 { + t.readBytesLeft = int64(t.config.RekeyThreshold) + } else if t.algorithms != nil { + t.readBytesLeft = t.algorithms.r.rekeyBytes() + } else { + t.readBytesLeft = 1 << 30 + } +} + +func (t *handshakeTransport) readOnePacket(first bool) ([]byte, error) { + p, err := t.conn.readPacket() + if err != nil { + return nil, err + } + + if t.readPacketsLeft > 0 { + t.readPacketsLeft-- + } else { + t.requestKeyExchange() + } + + if t.readBytesLeft > 0 { + t.readBytesLeft -= int64(len(p)) + } else { + t.requestKeyExchange() + } + + if debugHandshake { + t.printPacket(p, false) + } + + if first && p[0] != msgKexInit { + return nil, fmt.Errorf("ssh: first packet should be msgKexInit") + } + + if p[0] != msgKexInit { + return p, nil + } + + firstKex := t.sessionID == nil + + kex := pendingKex{ + done: make(chan error, 1), + otherInit: p, + } + t.startKex <- &kex + err = <-kex.done + + if debugHandshake { + log.Printf("%s exited key exchange (first %v), err %v", t.id(), firstKex, err) + } + + if err != nil { + return nil, err + } + + t.resetReadThresholds() + + // By default, a key exchange is hidden from higher layers by + // translating it into msgIgnore. + successPacket := []byte{msgIgnore} + if firstKex { + // sendKexInit() for the first kex waits for + // msgNewKeys so the authentication process is + // guaranteed to happen over an encrypted transport. + successPacket = []byte{msgNewKeys} + } + + return successPacket, nil +} + +// sendKexInit sends a key change message. +func (t *handshakeTransport) sendKexInit() error { + t.mu.Lock() + defer t.mu.Unlock() + if t.sentInitMsg != nil { + // kexInits may be sent either in response to the other side, + // or because our side wants to initiate a key change, so we + // may have already sent a kexInit. In that case, don't send a + // second kexInit. + return nil + } + + msg := &kexInitMsg{ + KexAlgos: t.config.KeyExchanges, + CiphersClientServer: t.config.Ciphers, + CiphersServerClient: t.config.Ciphers, + MACsClientServer: t.config.MACs, + MACsServerClient: t.config.MACs, + CompressionClientServer: supportedCompressions, + CompressionServerClient: supportedCompressions, + } + io.ReadFull(rand.Reader, msg.Cookie[:]) + + isServer := len(t.hostKeys) > 0 + if isServer { + for _, k := range t.hostKeys { + // If k is a MultiAlgorithmSigner, we restrict the signature + // algorithms. If k is a AlgorithmSigner, presume it supports all + // signature algorithms associated with the key format. If k is not + // an AlgorithmSigner, we can only assume it only supports the + // algorithms that matches the key format. (This means that Sign + // can't pick a different default). + keyFormat := k.PublicKey().Type() + + switch s := k.(type) { + case MultiAlgorithmSigner: + for _, algo := range algorithmsForKeyFormat(keyFormat) { + if contains(s.Algorithms(), underlyingAlgo(algo)) { + msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, algo) + } + } + case AlgorithmSigner: + msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, algorithmsForKeyFormat(keyFormat)...) + default: + msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, keyFormat) + } + } + } else { + msg.ServerHostKeyAlgos = t.hostKeyAlgorithms + + // As a client we opt in to receiving SSH_MSG_EXT_INFO so we know what + // algorithms the server supports for public key authentication. See RFC + // 8308, Section 2.1. + if firstKeyExchange := t.sessionID == nil; firstKeyExchange { + msg.KexAlgos = make([]string, 0, len(t.config.KeyExchanges)+1) + msg.KexAlgos = append(msg.KexAlgos, t.config.KeyExchanges...) + msg.KexAlgos = append(msg.KexAlgos, "ext-info-c") + } + } + + packet := Marshal(msg) + + // writePacket destroys the contents, so save a copy. + packetCopy := make([]byte, len(packet)) + copy(packetCopy, packet) + + if err := t.pushPacket(packetCopy); err != nil { + return err + } + + t.sentInitMsg = msg + t.sentInitPacket = packet + + return nil +} + +func (t *handshakeTransport) writePacket(p []byte) error { + switch p[0] { + case msgKexInit: + return errors.New("ssh: only handshakeTransport can send kexInit") + case msgNewKeys: + return errors.New("ssh: only handshakeTransport can send newKeys") + } + + t.mu.Lock() + defer t.mu.Unlock() + if t.writeError != nil { + return t.writeError + } + + if t.sentInitMsg != nil { + // Copy the packet so the writer can reuse the buffer. + cp := make([]byte, len(p)) + copy(cp, p) + t.pendingPackets = append(t.pendingPackets, cp) + return nil + } + + if t.writeBytesLeft > 0 { + t.writeBytesLeft -= int64(len(p)) + } else { + t.requestKeyExchange() + } + + if t.writePacketsLeft > 0 { + t.writePacketsLeft-- + } else { + t.requestKeyExchange() + } + + if err := t.pushPacket(p); err != nil { + t.writeError = err + } + + return nil +} + +func (t *handshakeTransport) Close() error { + // Close the connection. This should cause the readLoop goroutine to wake up + // and close t.startKex, which will shut down kexLoop if running. + err := t.conn.Close() + + // Wait for the kexLoop goroutine to complete. + // At that point we know that the readLoop goroutine is complete too, + // because kexLoop itself waits for readLoop to close the startKex channel. + <-t.kexLoopDone + + return err +} + +func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error { + if debugHandshake { + log.Printf("%s entered key exchange", t.id()) + } + + otherInit := &kexInitMsg{} + if err := Unmarshal(otherInitPacket, otherInit); err != nil { + return err + } + + magics := handshakeMagics{ + clientVersion: t.clientVersion, + serverVersion: t.serverVersion, + clientKexInit: otherInitPacket, + serverKexInit: t.sentInitPacket, + } + + clientInit := otherInit + serverInit := t.sentInitMsg + isClient := len(t.hostKeys) == 0 + if isClient { + clientInit, serverInit = serverInit, clientInit + + magics.clientKexInit = t.sentInitPacket + magics.serverKexInit = otherInitPacket + } + + var err error + t.algorithms, err = findAgreedAlgorithms(isClient, clientInit, serverInit) + if err != nil { + return err + } + + // We don't send FirstKexFollows, but we handle receiving it. + // + // RFC 4253 section 7 defines the kex and the agreement method for + // first_kex_packet_follows. It states that the guessed packet + // should be ignored if the "kex algorithm and/or the host + // key algorithm is guessed wrong (server and client have + // different preferred algorithm), or if any of the other + // algorithms cannot be agreed upon". The other algorithms have + // already been checked above so the kex algorithm and host key + // algorithm are checked here. + if otherInit.FirstKexFollows && (clientInit.KexAlgos[0] != serverInit.KexAlgos[0] || clientInit.ServerHostKeyAlgos[0] != serverInit.ServerHostKeyAlgos[0]) { + // other side sent a kex message for the wrong algorithm, + // which we have to ignore. + if _, err := t.conn.readPacket(); err != nil { + return err + } + } + + kex, ok := kexAlgoMap[t.algorithms.kex] + if !ok { + return fmt.Errorf("ssh: unexpected key exchange algorithm %v", t.algorithms.kex) + } + + var result *kexResult + if len(t.hostKeys) > 0 { + result, err = t.server(kex, &magics) + } else { + result, err = t.client(kex, &magics) + } + + if err != nil { + return err + } + + firstKeyExchange := t.sessionID == nil + if firstKeyExchange { + t.sessionID = result.H + } + result.SessionID = t.sessionID + + if err := t.conn.prepareKeyChange(t.algorithms, result); err != nil { + return err + } + if err = t.conn.writePacket([]byte{msgNewKeys}); err != nil { + return err + } + + // On the server side, after the first SSH_MSG_NEWKEYS, send a SSH_MSG_EXT_INFO + // message with the server-sig-algs extension if the client supports it. See + // RFC 8308, Sections 2.4 and 3.1, and [PROTOCOL], Section 1.9. + if !isClient && firstKeyExchange && contains(clientInit.KexAlgos, "ext-info-c") { + supportedPubKeyAuthAlgosList := strings.Join(t.publicKeyAuthAlgorithms, ",") + extInfo := &extInfoMsg{ + NumExtensions: 2, + Payload: make([]byte, 0, 4+15+4+len(supportedPubKeyAuthAlgosList)+4+16+4+1), + } + extInfo.Payload = appendInt(extInfo.Payload, len("server-sig-algs")) + extInfo.Payload = append(extInfo.Payload, "server-sig-algs"...) + extInfo.Payload = appendInt(extInfo.Payload, len(supportedPubKeyAuthAlgosList)) + extInfo.Payload = append(extInfo.Payload, supportedPubKeyAuthAlgosList...) + extInfo.Payload = appendInt(extInfo.Payload, len("ping@openssh.com")) + extInfo.Payload = append(extInfo.Payload, "ping@openssh.com"...) + extInfo.Payload = appendInt(extInfo.Payload, 1) + extInfo.Payload = append(extInfo.Payload, "0"...) + if err := t.conn.writePacket(Marshal(extInfo)); err != nil { + return err + } + } + + if packet, err := t.conn.readPacket(); err != nil { + return err + } else if packet[0] != msgNewKeys { + return unexpectedMessageError(msgNewKeys, packet[0]) + } + + return nil +} + +// algorithmSignerWrapper is an AlgorithmSigner that only supports the default +// key format algorithm. +// +// This is technically a violation of the AlgorithmSigner interface, but it +// should be unreachable given where we use this. Anyway, at least it returns an +// error instead of panicing or producing an incorrect signature. +type algorithmSignerWrapper struct { + Signer +} + +func (a algorithmSignerWrapper) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { + if algorithm != underlyingAlgo(a.PublicKey().Type()) { + return nil, errors.New("ssh: internal error: algorithmSignerWrapper invoked with non-default algorithm") + } + return a.Sign(rand, data) +} + +func pickHostKey(hostKeys []Signer, algo string) AlgorithmSigner { + for _, k := range hostKeys { + if s, ok := k.(MultiAlgorithmSigner); ok { + if !contains(s.Algorithms(), underlyingAlgo(algo)) { + continue + } + } + + if algo == k.PublicKey().Type() { + return algorithmSignerWrapper{k} + } + + k, ok := k.(AlgorithmSigner) + if !ok { + continue + } + for _, a := range algorithmsForKeyFormat(k.PublicKey().Type()) { + if algo == a { + return k + } + } + } + return nil +} + +func (t *handshakeTransport) server(kex kexAlgorithm, magics *handshakeMagics) (*kexResult, error) { + hostKey := pickHostKey(t.hostKeys, t.algorithms.hostKey) + if hostKey == nil { + return nil, errors.New("ssh: internal error: negotiated unsupported signature type") + } + + r, err := kex.Server(t.conn, t.config.Rand, magics, hostKey, t.algorithms.hostKey) + return r, err +} + +func (t *handshakeTransport) client(kex kexAlgorithm, magics *handshakeMagics) (*kexResult, error) { + result, err := kex.Client(t.conn, t.config.Rand, magics) + if err != nil { + return nil, err + } + + hostKey, err := ParsePublicKey(result.HostKey) + if err != nil { + return nil, err + } + + if err := verifyHostKeySignature(hostKey, t.algorithms.hostKey, result); err != nil { + return nil, err + } + + err = t.hostKeyCallback(t.dialAddress, t.remoteAddr, hostKey) + if err != nil { + return nil, err + } + + return result, nil +} diff --git a/pkg/proto/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go b/pkg/proto/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go new file mode 100644 index 0000000..af81d26 --- /dev/null +++ b/pkg/proto/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go @@ -0,0 +1,93 @@ +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package bcrypt_pbkdf implements bcrypt_pbkdf(3) from OpenBSD. +// +// See https://flak.tedunangst.com/post/bcrypt-pbkdf and +// https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libutil/bcrypt_pbkdf.c. +package bcrypt_pbkdf + +import ( + "crypto/sha512" + "errors" + "golang.org/x/crypto/blowfish" +) + +const blockSize = 32 + +// Key derives a key from the password, salt and rounds count, returning a +// []byte of length keyLen that can be used as cryptographic key. +func Key(password, salt []byte, rounds, keyLen int) ([]byte, error) { + if rounds < 1 { + return nil, errors.New("bcrypt_pbkdf: number of rounds is too small") + } + if len(password) == 0 { + return nil, errors.New("bcrypt_pbkdf: empty password") + } + if len(salt) == 0 || len(salt) > 1<<20 { + return nil, errors.New("bcrypt_pbkdf: bad salt length") + } + if keyLen > 1024 { + return nil, errors.New("bcrypt_pbkdf: keyLen is too large") + } + + numBlocks := (keyLen + blockSize - 1) / blockSize + key := make([]byte, numBlocks*blockSize) + + h := sha512.New() + h.Write(password) + shapass := h.Sum(nil) + + shasalt := make([]byte, 0, sha512.Size) + cnt, tmp := make([]byte, 4), make([]byte, blockSize) + for block := 1; block <= numBlocks; block++ { + h.Reset() + h.Write(salt) + cnt[0] = byte(block >> 24) + cnt[1] = byte(block >> 16) + cnt[2] = byte(block >> 8) + cnt[3] = byte(block) + h.Write(cnt) + bcryptHash(tmp, shapass, h.Sum(shasalt)) + + out := make([]byte, blockSize) + copy(out, tmp) + for i := 2; i <= rounds; i++ { + h.Reset() + h.Write(tmp) + bcryptHash(tmp, shapass, h.Sum(shasalt)) + for j := 0; j < len(out); j++ { + out[j] ^= tmp[j] + } + } + + for i, v := range out { + key[i*numBlocks+(block-1)] = v + } + } + return key[:keyLen], nil +} + +var magic = []byte("OxychromaticBlowfishSwatDynamite") + +func bcryptHash(out, shapass, shasalt []byte) { + c, err := blowfish.NewSaltedCipher(shapass, shasalt) + if err != nil { + panic(err) + } + for i := 0; i < 64; i++ { + blowfish.ExpandKey(shasalt, c) + blowfish.ExpandKey(shapass, c) + } + copy(out, magic) + for i := 0; i < 32; i += 8 { + for j := 0; j < 64; j++ { + c.Encrypt(out[i:i+8], out[i:i+8]) + } + } + // Swap bytes due to different endianness. + for i := 0; i < 32; i += 4 { + out[i+3], out[i+2], out[i+1], out[i] = out[i], out[i+1], out[i+2], out[i+3] + } +} diff --git a/pkg/proto/ssh/internal/poly1305/bits_compat.go b/pkg/proto/ssh/internal/poly1305/bits_compat.go new file mode 100644 index 0000000..d33c889 --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/bits_compat.go @@ -0,0 +1,39 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build !go1.13 + +package poly1305 + +// Generic fallbacks for the math/bits intrinsics, copied from +// src/math/bits/bits.go. They were added in Go 1.12, but Add64 and Sum64 had +// variable time fallbacks until Go 1.13. + +func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) { + sum = x + y + carry + carryOut = ((x & y) | ((x | y) &^ sum)) >> 63 + return +} + +func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) { + diff = x - y - borrow + borrowOut = ((^x & y) | (^(x ^ y) & diff)) >> 63 + return +} + +func bitsMul64(x, y uint64) (hi, lo uint64) { + const mask32 = 1<<32 - 1 + x0 := x & mask32 + x1 := x >> 32 + y0 := y & mask32 + y1 := y >> 32 + w0 := x0 * y0 + t := x1*y0 + w0>>32 + w1 := t & mask32 + w2 := t >> 32 + w1 += x0 * y1 + hi = x1*y1 + w2 + w1>>32 + lo = x * y + return +} diff --git a/pkg/proto/ssh/internal/poly1305/bits_go1.13.go b/pkg/proto/ssh/internal/poly1305/bits_go1.13.go new file mode 100644 index 0000000..495c1fa --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/bits_go1.13.go @@ -0,0 +1,21 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build go1.13 + +package poly1305 + +import "math/bits" + +func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) { + return bits.Add64(x, y, carry) +} + +func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) { + return bits.Sub64(x, y, borrow) +} + +func bitsMul64(x, y uint64) (hi, lo uint64) { + return bits.Mul64(x, y) +} diff --git a/pkg/proto/ssh/internal/poly1305/mac_noasm.go b/pkg/proto/ssh/internal/poly1305/mac_noasm.go new file mode 100644 index 0000000..333da28 --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/mac_noasm.go @@ -0,0 +1,9 @@ +// Copyright 2018 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build (!amd64 && !ppc64le && !s390x) || !gc || purego + +package poly1305 + +type mac struct{ macGeneric } diff --git a/pkg/proto/ssh/internal/poly1305/poly1305.go b/pkg/proto/ssh/internal/poly1305/poly1305.go new file mode 100644 index 0000000..4aaea81 --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/poly1305.go @@ -0,0 +1,99 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package poly1305 implements Poly1305 one-time message authentication code as +// specified in https://cr.yp.to/mac/poly1305-20050329.pdf. +// +// Poly1305 is a fast, one-time authentication function. It is infeasible for an +// attacker to generate an authenticator for a message without the key. However, a +// key must only be used for a single message. Authenticating two different +// messages with the same key allows an attacker to forge authenticators for other +// messages with the same key. +// +// Poly1305 was originally coupled with AES in order to make Poly1305-AES. AES was +// used with a fixed key in order to generate one-time keys from an nonce. +// However, in this package AES isn't used and the one-time key is specified +// directly. +package poly1305 + +import "crypto/subtle" + +// TagSize is the size, in bytes, of a poly1305 authenticator. +const TagSize = 16 + +// Sum generates an authenticator for msg using a one-time key and puts the +// 16-byte result into out. Authenticating two different messages with the same +// key allows an attacker to forge messages at will. +func Sum(out *[16]byte, m []byte, key *[32]byte) { + h := New(key) + h.Write(m) + h.Sum(out[:0]) +} + +// Verify returns true if mac is a valid authenticator for m with the given key. +func Verify(mac *[16]byte, m []byte, key *[32]byte) bool { + var tmp [16]byte + Sum(&tmp, m, key) + return subtle.ConstantTimeCompare(tmp[:], mac[:]) == 1 +} + +// New returns a new MAC computing an authentication +// tag of all data written to it with the given key. +// This allows writing the message progressively instead +// of passing it as a single slice. Common users should use +// the Sum function instead. +// +// The key must be unique for each message, as authenticating +// two different messages with the same key allows an attacker +// to forge messages at will. +func New(key *[32]byte) *MAC { + m := &MAC{} + initialize(key, &m.macState) + return m +} + +// MAC is an io.Writer computing an authentication tag +// of the data written to it. +// +// MAC cannot be used like common hash.Hash implementations, +// because using a poly1305 key twice breaks its security. +// Therefore writing data to a running MAC after calling +// Sum or Verify causes it to panic. +type MAC struct { + mac // platform-dependent implementation + + finalized bool +} + +// Size returns the number of bytes Sum will return. +func (h *MAC) Size() int { return TagSize } + +// Write adds more data to the running message authentication code. +// It never returns an error. +// +// It must not be called after the first call of Sum or Verify. +func (h *MAC) Write(p []byte) (n int, err error) { + if h.finalized { + panic("poly1305: write to MAC after Sum or Verify") + } + return h.mac.Write(p) +} + +// Sum computes the authenticator of all data written to the +// message authentication code. +func (h *MAC) Sum(b []byte) []byte { + var mac [TagSize]byte + h.mac.Sum(&mac) + h.finalized = true + return append(b, mac[:]...) +} + +// Verify returns whether the authenticator of all data written to +// the message authentication code matches the expected value. +func (h *MAC) Verify(expected []byte) bool { + var mac [TagSize]byte + h.mac.Sum(&mac) + h.finalized = true + return subtle.ConstantTimeCompare(expected, mac[:]) == 1 +} diff --git a/pkg/proto/ssh/internal/poly1305/sum_amd64.go b/pkg/proto/ssh/internal/poly1305/sum_amd64.go new file mode 100644 index 0000000..164cd47 --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/sum_amd64.go @@ -0,0 +1,47 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build gc && !purego + +package poly1305 + +//go:noescape +func update(state *macState, msg []byte) + +// mac is a wrapper for macGeneric that redirects calls that would have gone to +// updateGeneric to update. +// +// Its Write and Sum methods are otherwise identical to the macGeneric ones, but +// using function pointers would carry a major performance cost. +type mac struct{ macGeneric } + +func (h *mac) Write(p []byte) (int, error) { + nn := len(p) + if h.offset > 0 { + n := copy(h.buffer[h.offset:], p) + if h.offset+n < TagSize { + h.offset += n + return nn, nil + } + p = p[n:] + h.offset = 0 + update(&h.macState, h.buffer[:]) + } + if n := len(p) - (len(p) % TagSize); n > 0 { + update(&h.macState, p[:n]) + p = p[n:] + } + if len(p) > 0 { + h.offset += copy(h.buffer[h.offset:], p) + } + return nn, nil +} + +func (h *mac) Sum(out *[16]byte) { + state := h.macState + if h.offset > 0 { + update(&state, h.buffer[:h.offset]) + } + finalize(out, &state.h, &state.s) +} diff --git a/pkg/proto/ssh/internal/poly1305/sum_amd64.s b/pkg/proto/ssh/internal/poly1305/sum_amd64.s new file mode 100644 index 0000000..e0d3c64 --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/sum_amd64.s @@ -0,0 +1,108 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build gc && !purego + +#include "textflag.h" + +#define POLY1305_ADD(msg, h0, h1, h2) \ + ADDQ 0(msg), h0; \ + ADCQ 8(msg), h1; \ + ADCQ $1, h2; \ + LEAQ 16(msg), msg + +#define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3) \ + MOVQ r0, AX; \ + MULQ h0; \ + MOVQ AX, t0; \ + MOVQ DX, t1; \ + MOVQ r0, AX; \ + MULQ h1; \ + ADDQ AX, t1; \ + ADCQ $0, DX; \ + MOVQ r0, t2; \ + IMULQ h2, t2; \ + ADDQ DX, t2; \ + \ + MOVQ r1, AX; \ + MULQ h0; \ + ADDQ AX, t1; \ + ADCQ $0, DX; \ + MOVQ DX, h0; \ + MOVQ r1, t3; \ + IMULQ h2, t3; \ + MOVQ r1, AX; \ + MULQ h1; \ + ADDQ AX, t2; \ + ADCQ DX, t3; \ + ADDQ h0, t2; \ + ADCQ $0, t3; \ + \ + MOVQ t0, h0; \ + MOVQ t1, h1; \ + MOVQ t2, h2; \ + ANDQ $3, h2; \ + MOVQ t2, t0; \ + ANDQ $0xFFFFFFFFFFFFFFFC, t0; \ + ADDQ t0, h0; \ + ADCQ t3, h1; \ + ADCQ $0, h2; \ + SHRQ $2, t3, t2; \ + SHRQ $2, t3; \ + ADDQ t2, h0; \ + ADCQ t3, h1; \ + ADCQ $0, h2 + +// func update(state *[7]uint64, msg []byte) +TEXT ·update(SB), $0-32 + MOVQ state+0(FP), DI + MOVQ msg_base+8(FP), SI + MOVQ msg_len+16(FP), R15 + + MOVQ 0(DI), R8 // h0 + MOVQ 8(DI), R9 // h1 + MOVQ 16(DI), R10 // h2 + MOVQ 24(DI), R11 // r0 + MOVQ 32(DI), R12 // r1 + + CMPQ R15, $16 + JB bytes_between_0_and_15 + +loop: + POLY1305_ADD(SI, R8, R9, R10) + +multiply: + POLY1305_MUL(R8, R9, R10, R11, R12, BX, CX, R13, R14) + SUBQ $16, R15 + CMPQ R15, $16 + JAE loop + +bytes_between_0_and_15: + TESTQ R15, R15 + JZ done + MOVQ $1, BX + XORQ CX, CX + XORQ R13, R13 + ADDQ R15, SI + +flush_buffer: + SHLQ $8, BX, CX + SHLQ $8, BX + MOVB -1(SI), R13 + XORQ R13, BX + DECQ SI + DECQ R15 + JNZ flush_buffer + + ADDQ BX, R8 + ADCQ CX, R9 + ADCQ $0, R10 + MOVQ $16, R15 + JMP multiply + +done: + MOVQ R8, 0(DI) + MOVQ R9, 8(DI) + MOVQ R10, 16(DI) + RET diff --git a/pkg/proto/ssh/internal/poly1305/sum_generic.go b/pkg/proto/ssh/internal/poly1305/sum_generic.go new file mode 100644 index 0000000..e041da5 --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/sum_generic.go @@ -0,0 +1,309 @@ +// Copyright 2018 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// This file provides the generic implementation of Sum and MAC. Other files +// might provide optimized assembly implementations of some of this code. + +package poly1305 + +import "encoding/binary" + +// Poly1305 [RFC 7539] is a relatively simple algorithm: the authentication tag +// for a 64 bytes message is approximately +// +// s + m[0:16] * r⁴ + m[16:32] * r³ + m[32:48] * r² + m[48:64] * r mod 2¹³⁰ - 5 +// +// for some secret r and s. It can be computed sequentially like +// +// for len(msg) > 0: +// h += read(msg, 16) +// h *= r +// h %= 2¹³⁰ - 5 +// return h + s +// +// All the complexity is about doing performant constant-time math on numbers +// larger than any available numeric type. + +func sumGeneric(out *[TagSize]byte, msg []byte, key *[32]byte) { + h := newMACGeneric(key) + h.Write(msg) + h.Sum(out) +} + +func newMACGeneric(key *[32]byte) macGeneric { + m := macGeneric{} + initialize(key, &m.macState) + return m +} + +// macState holds numbers in saturated 64-bit little-endian limbs. That is, +// the value of [x0, x1, x2] is x[0] + x[1] * 2⁶⁴ + x[2] * 2¹²⁸. +type macState struct { + // h is the main accumulator. It is to be interpreted modulo 2¹³⁰ - 5, but + // can grow larger during and after rounds. It must, however, remain below + // 2 * (2¹³⁰ - 5). + h [3]uint64 + // r and s are the private key components. + r [2]uint64 + s [2]uint64 +} + +type macGeneric struct { + macState + + buffer [TagSize]byte + offset int +} + +// Write splits the incoming message into TagSize chunks, and passes them to +// update. It buffers incomplete chunks. +func (h *macGeneric) Write(p []byte) (int, error) { + nn := len(p) + if h.offset > 0 { + n := copy(h.buffer[h.offset:], p) + if h.offset+n < TagSize { + h.offset += n + return nn, nil + } + p = p[n:] + h.offset = 0 + updateGeneric(&h.macState, h.buffer[:]) + } + if n := len(p) - (len(p) % TagSize); n > 0 { + updateGeneric(&h.macState, p[:n]) + p = p[n:] + } + if len(p) > 0 { + h.offset += copy(h.buffer[h.offset:], p) + } + return nn, nil +} + +// Sum flushes the last incomplete chunk from the buffer, if any, and generates +// the MAC output. It does not modify its state, in order to allow for multiple +// calls to Sum, even if no Write is allowed after Sum. +func (h *macGeneric) Sum(out *[TagSize]byte) { + state := h.macState + if h.offset > 0 { + updateGeneric(&state, h.buffer[:h.offset]) + } + finalize(out, &state.h, &state.s) +} + +// [rMask0, rMask1] is the specified Poly1305 clamping mask in little-endian. It +// clears some bits of the secret coefficient to make it possible to implement +// multiplication more efficiently. +const ( + rMask0 = 0x0FFFFFFC0FFFFFFF + rMask1 = 0x0FFFFFFC0FFFFFFC +) + +// initialize loads the 256-bit key into the two 128-bit secret values r and s. +func initialize(key *[32]byte, m *macState) { + m.r[0] = binary.LittleEndian.Uint64(key[0:8]) & rMask0 + m.r[1] = binary.LittleEndian.Uint64(key[8:16]) & rMask1 + m.s[0] = binary.LittleEndian.Uint64(key[16:24]) + m.s[1] = binary.LittleEndian.Uint64(key[24:32]) +} + +// uint128 holds a 128-bit number as two 64-bit limbs, for use with the +// bits.Mul64 and bits.Add64 intrinsics. +type uint128 struct { + lo, hi uint64 +} + +func mul64(a, b uint64) uint128 { + hi, lo := bitsMul64(a, b) + return uint128{lo, hi} +} + +func add128(a, b uint128) uint128 { + lo, c := bitsAdd64(a.lo, b.lo, 0) + hi, c := bitsAdd64(a.hi, b.hi, c) + if c != 0 { + panic("poly1305: unexpected overflow") + } + return uint128{lo, hi} +} + +func shiftRightBy2(a uint128) uint128 { + a.lo = a.lo>>2 | (a.hi&3)<<62 + a.hi = a.hi >> 2 + return a +} + +// updateGeneric absorbs msg into the state.h accumulator. For each chunk m of +// 128 bits of message, it computes +// +// h₊ = (h + m) * r mod 2¹³⁰ - 5 +// +// If the msg length is not a multiple of TagSize, it assumes the last +// incomplete chunk is the final one. +func updateGeneric(state *macState, msg []byte) { + h0, h1, h2 := state.h[0], state.h[1], state.h[2] + r0, r1 := state.r[0], state.r[1] + + for len(msg) > 0 { + var c uint64 + + // For the first step, h + m, we use a chain of bits.Add64 intrinsics. + // The resulting value of h might exceed 2¹³⁰ - 5, but will be partially + // reduced at the end of the multiplication below. + // + // The spec requires us to set a bit just above the message size, not to + // hide leading zeroes. For full chunks, that's 1 << 128, so we can just + // add 1 to the most significant (2¹²⁸) limb, h2. + if len(msg) >= TagSize { + h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0) + h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(msg[8:16]), c) + h2 += c + 1 + + msg = msg[TagSize:] + } else { + var buf [TagSize]byte + copy(buf[:], msg) + buf[len(msg)] = 1 + + h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0) + h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(buf[8:16]), c) + h2 += c + + msg = nil + } + + // Multiplication of big number limbs is similar to elementary school + // columnar multiplication. Instead of digits, there are 64-bit limbs. + // + // We are multiplying a 3 limbs number, h, by a 2 limbs number, r. + // + // h2 h1 h0 x + // r1 r0 = + // ---------------- + // h2r0 h1r0 h0r0 <-- individual 128-bit products + // + h2r1 h1r1 h0r1 + // ------------------------ + // m3 m2 m1 m0 <-- result in 128-bit overlapping limbs + // ------------------------ + // m3.hi m2.hi m1.hi m0.hi <-- carry propagation + // + m3.lo m2.lo m1.lo m0.lo + // ------------------------------- + // t4 t3 t2 t1 t0 <-- final result in 64-bit limbs + // + // The main difference from pen-and-paper multiplication is that we do + // carry propagation in a separate step, as if we wrote two digit sums + // at first (the 128-bit limbs), and then carried the tens all at once. + + h0r0 := mul64(h0, r0) + h1r0 := mul64(h1, r0) + h2r0 := mul64(h2, r0) + h0r1 := mul64(h0, r1) + h1r1 := mul64(h1, r1) + h2r1 := mul64(h2, r1) + + // Since h2 is known to be at most 7 (5 + 1 + 1), and r0 and r1 have their + // top 4 bits cleared by rMask{0,1}, we know that their product is not going + // to overflow 64 bits, so we can ignore the high part of the products. + // + // This also means that the product doesn't have a fifth limb (t4). + if h2r0.hi != 0 { + panic("poly1305: unexpected overflow") + } + if h2r1.hi != 0 { + panic("poly1305: unexpected overflow") + } + + m0 := h0r0 + m1 := add128(h1r0, h0r1) // These two additions don't overflow thanks again + m2 := add128(h2r0, h1r1) // to the 4 masked bits at the top of r0 and r1. + m3 := h2r1 + + t0 := m0.lo + t1, c := bitsAdd64(m1.lo, m0.hi, 0) + t2, c := bitsAdd64(m2.lo, m1.hi, c) + t3, _ := bitsAdd64(m3.lo, m2.hi, c) + + // Now we have the result as 4 64-bit limbs, and we need to reduce it + // modulo 2¹³⁰ - 5. The special shape of this Crandall prime lets us do + // a cheap partial reduction according to the reduction identity + // + // c * 2¹³⁰ + n = c * 5 + n mod 2¹³⁰ - 5 + // + // because 2¹³⁰ = 5 mod 2¹³⁰ - 5. Partial reduction since the result is + // likely to be larger than 2¹³⁰ - 5, but still small enough to fit the + // assumptions we make about h in the rest of the code. + // + // See also https://speakerdeck.com/gtank/engineering-prime-numbers?slide=23 + + // We split the final result at the 2¹³⁰ mark into h and cc, the carry. + // Note that the carry bits are effectively shifted left by 2, in other + // words, cc = c * 4 for the c in the reduction identity. + h0, h1, h2 = t0, t1, t2&maskLow2Bits + cc := uint128{t2 & maskNotLow2Bits, t3} + + // To add c * 5 to h, we first add cc = c * 4, and then add (cc >> 2) = c. + + h0, c = bitsAdd64(h0, cc.lo, 0) + h1, c = bitsAdd64(h1, cc.hi, c) + h2 += c + + cc = shiftRightBy2(cc) + + h0, c = bitsAdd64(h0, cc.lo, 0) + h1, c = bitsAdd64(h1, cc.hi, c) + h2 += c + + // h2 is at most 3 + 1 + 1 = 5, making the whole of h at most + // + // 5 * 2¹²⁸ + (2¹²⁸ - 1) = 6 * 2¹²⁸ - 1 + } + + state.h[0], state.h[1], state.h[2] = h0, h1, h2 +} + +const ( + maskLow2Bits uint64 = 0x0000000000000003 + maskNotLow2Bits uint64 = ^maskLow2Bits +) + +// select64 returns x if v == 1 and y if v == 0, in constant time. +func select64(v, x, y uint64) uint64 { return ^(v-1)&x | (v-1)&y } + +// [p0, p1, p2] is 2¹³⁰ - 5 in little endian order. +const ( + p0 = 0xFFFFFFFFFFFFFFFB + p1 = 0xFFFFFFFFFFFFFFFF + p2 = 0x0000000000000003 +) + +// finalize completes the modular reduction of h and computes +// +// out = h + s mod 2¹²⁸ +func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) { + h0, h1, h2 := h[0], h[1], h[2] + + // After the partial reduction in updateGeneric, h might be more than + // 2¹³⁰ - 5, but will be less than 2 * (2¹³⁰ - 5). To complete the reduction + // in constant time, we compute t = h - (2¹³⁰ - 5), and select h as the + // result if the subtraction underflows, and t otherwise. + + hMinusP0, b := bitsSub64(h0, p0, 0) + hMinusP1, b := bitsSub64(h1, p1, b) + _, b = bitsSub64(h2, p2, b) + + // h = h if h < p else h - p + h0 = select64(b, h0, hMinusP0) + h1 = select64(b, h1, hMinusP1) + + // Finally, we compute the last Poly1305 step + // + // tag = h + s mod 2¹²⁸ + // + // by just doing a wide addition with the 128 low bits of h and discarding + // the overflow. + h0, c := bitsAdd64(h0, s[0], 0) + h1, _ = bitsAdd64(h1, s[1], c) + + binary.LittleEndian.PutUint64(out[0:8], h0) + binary.LittleEndian.PutUint64(out[8:16], h1) +} diff --git a/pkg/proto/ssh/internal/poly1305/sum_ppc64le.go b/pkg/proto/ssh/internal/poly1305/sum_ppc64le.go new file mode 100644 index 0000000..4aec487 --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/sum_ppc64le.go @@ -0,0 +1,47 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build gc && !purego + +package poly1305 + +//go:noescape +func update(state *macState, msg []byte) + +// mac is a wrapper for macGeneric that redirects calls that would have gone to +// updateGeneric to update. +// +// Its Write and Sum methods are otherwise identical to the macGeneric ones, but +// using function pointers would carry a major performance cost. +type mac struct{ macGeneric } + +func (h *mac) Write(p []byte) (int, error) { + nn := len(p) + if h.offset > 0 { + n := copy(h.buffer[h.offset:], p) + if h.offset+n < TagSize { + h.offset += n + return nn, nil + } + p = p[n:] + h.offset = 0 + update(&h.macState, h.buffer[:]) + } + if n := len(p) - (len(p) % TagSize); n > 0 { + update(&h.macState, p[:n]) + p = p[n:] + } + if len(p) > 0 { + h.offset += copy(h.buffer[h.offset:], p) + } + return nn, nil +} + +func (h *mac) Sum(out *[16]byte) { + state := h.macState + if h.offset > 0 { + update(&state, h.buffer[:h.offset]) + } + finalize(out, &state.h, &state.s) +} diff --git a/pkg/proto/ssh/internal/poly1305/sum_ppc64le.s b/pkg/proto/ssh/internal/poly1305/sum_ppc64le.s new file mode 100644 index 0000000..d2ca5de --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/sum_ppc64le.s @@ -0,0 +1,181 @@ +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build gc && !purego + +#include "textflag.h" + +// This was ported from the amd64 implementation. + +#define POLY1305_ADD(msg, h0, h1, h2, t0, t1, t2) \ + MOVD (msg), t0; \ + MOVD 8(msg), t1; \ + MOVD $1, t2; \ + ADDC t0, h0, h0; \ + ADDE t1, h1, h1; \ + ADDE t2, h2; \ + ADD $16, msg + +#define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3, t4, t5) \ + MULLD r0, h0, t0; \ + MULLD r0, h1, t4; \ + MULHDU r0, h0, t1; \ + MULHDU r0, h1, t5; \ + ADDC t4, t1, t1; \ + MULLD r0, h2, t2; \ + ADDZE t5; \ + MULHDU r1, h0, t4; \ + MULLD r1, h0, h0; \ + ADD t5, t2, t2; \ + ADDC h0, t1, t1; \ + MULLD h2, r1, t3; \ + ADDZE t4, h0; \ + MULHDU r1, h1, t5; \ + MULLD r1, h1, t4; \ + ADDC t4, t2, t2; \ + ADDE t5, t3, t3; \ + ADDC h0, t2, t2; \ + MOVD $-4, t4; \ + MOVD t0, h0; \ + MOVD t1, h1; \ + ADDZE t3; \ + ANDCC $3, t2, h2; \ + AND t2, t4, t0; \ + ADDC t0, h0, h0; \ + ADDE t3, h1, h1; \ + SLD $62, t3, t4; \ + SRD $2, t2; \ + ADDZE h2; \ + OR t4, t2, t2; \ + SRD $2, t3; \ + ADDC t2, h0, h0; \ + ADDE t3, h1, h1; \ + ADDZE h2 + +DATA ·poly1305Mask<>+0x00(SB)/8, $0x0FFFFFFC0FFFFFFF +DATA ·poly1305Mask<>+0x08(SB)/8, $0x0FFFFFFC0FFFFFFC +GLOBL ·poly1305Mask<>(SB), RODATA, $16 + +// func update(state *[7]uint64, msg []byte) +TEXT ·update(SB), $0-32 + MOVD state+0(FP), R3 + MOVD msg_base+8(FP), R4 + MOVD msg_len+16(FP), R5 + + MOVD 0(R3), R8 // h0 + MOVD 8(R3), R9 // h1 + MOVD 16(R3), R10 // h2 + MOVD 24(R3), R11 // r0 + MOVD 32(R3), R12 // r1 + + CMP R5, $16 + BLT bytes_between_0_and_15 + +loop: + POLY1305_ADD(R4, R8, R9, R10, R20, R21, R22) + +multiply: + POLY1305_MUL(R8, R9, R10, R11, R12, R16, R17, R18, R14, R20, R21) + ADD $-16, R5 + CMP R5, $16 + BGE loop + +bytes_between_0_and_15: + CMP R5, $0 + BEQ done + MOVD $0, R16 // h0 + MOVD $0, R17 // h1 + +flush_buffer: + CMP R5, $8 + BLE just1 + + MOVD $8, R21 + SUB R21, R5, R21 + + // Greater than 8 -- load the rightmost remaining bytes in msg + // and put into R17 (h1) + MOVD (R4)(R21), R17 + MOVD $16, R22 + + // Find the offset to those bytes + SUB R5, R22, R22 + SLD $3, R22 + + // Shift to get only the bytes in msg + SRD R22, R17, R17 + + // Put 1 at high end + MOVD $1, R23 + SLD $3, R21 + SLD R21, R23, R23 + OR R23, R17, R17 + + // Remainder is 8 + MOVD $8, R5 + +just1: + CMP R5, $8 + BLT less8 + + // Exactly 8 + MOVD (R4), R16 + + CMP R17, $0 + + // Check if we've already set R17; if not + // set 1 to indicate end of msg. + BNE carry + MOVD $1, R17 + BR carry + +less8: + MOVD $0, R16 // h0 + MOVD $0, R22 // shift count + CMP R5, $4 + BLT less4 + MOVWZ (R4), R16 + ADD $4, R4 + ADD $-4, R5 + MOVD $32, R22 + +less4: + CMP R5, $2 + BLT less2 + MOVHZ (R4), R21 + SLD R22, R21, R21 + OR R16, R21, R16 + ADD $16, R22 + ADD $-2, R5 + ADD $2, R4 + +less2: + CMP R5, $0 + BEQ insert1 + MOVBZ (R4), R21 + SLD R22, R21, R21 + OR R16, R21, R16 + ADD $8, R22 + +insert1: + // Insert 1 at end of msg + MOVD $1, R21 + SLD R22, R21, R21 + OR R16, R21, R16 + +carry: + // Add new values to h0, h1, h2 + ADDC R16, R8 + ADDE R17, R9 + ADDZE R10, R10 + MOVD $16, R5 + ADD R5, R4 + BR multiply + +done: + // Save h0, h1, h2 in state + MOVD R8, 0(R3) + MOVD R9, 8(R3) + MOVD R10, 16(R3) + RET diff --git a/pkg/proto/ssh/internal/poly1305/sum_s390x.go b/pkg/proto/ssh/internal/poly1305/sum_s390x.go new file mode 100644 index 0000000..e1d033a --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/sum_s390x.go @@ -0,0 +1,76 @@ +// Copyright 2018 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build gc && !purego + +package poly1305 + +import ( + "golang.org/x/sys/cpu" +) + +// updateVX is an assembly implementation of Poly1305 that uses vector +// instructions. It must only be called if the vector facility (vx) is +// available. +// +//go:noescape +func updateVX(state *macState, msg []byte) + +// mac is a replacement for macGeneric that uses a larger buffer and redirects +// calls that would have gone to updateGeneric to updateVX if the vector +// facility is installed. +// +// A larger buffer is required for good performance because the vector +// implementation has a higher fixed cost per call than the generic +// implementation. +type mac struct { + macState + + buffer [16 * TagSize]byte // size must be a multiple of block size (16) + offset int +} + +func (h *mac) Write(p []byte) (int, error) { + nn := len(p) + if h.offset > 0 { + n := copy(h.buffer[h.offset:], p) + if h.offset+n < len(h.buffer) { + h.offset += n + return nn, nil + } + p = p[n:] + h.offset = 0 + if cpu.S390X.HasVX { + updateVX(&h.macState, h.buffer[:]) + } else { + updateGeneric(&h.macState, h.buffer[:]) + } + } + + tail := len(p) % len(h.buffer) // number of bytes to copy into buffer + body := len(p) - tail // number of bytes to process now + if body > 0 { + if cpu.S390X.HasVX { + updateVX(&h.macState, p[:body]) + } else { + updateGeneric(&h.macState, p[:body]) + } + } + h.offset = copy(h.buffer[:], p[body:]) // copy tail bytes - can be 0 + return nn, nil +} + +func (h *mac) Sum(out *[TagSize]byte) { + state := h.macState + remainder := h.buffer[:h.offset] + + // Use the generic implementation if we have 2 or fewer blocks left + // to sum. The vector implementation has a higher startup time. + if cpu.S390X.HasVX && len(remainder) > 2*TagSize { + updateVX(&state, remainder) + } else if len(remainder) > 0 { + updateGeneric(&state, remainder) + } + finalize(out, &state.h, &state.s) +} diff --git a/pkg/proto/ssh/internal/poly1305/sum_s390x.s b/pkg/proto/ssh/internal/poly1305/sum_s390x.s new file mode 100644 index 0000000..0fe3a7c --- /dev/null +++ b/pkg/proto/ssh/internal/poly1305/sum_s390x.s @@ -0,0 +1,503 @@ +// Copyright 2018 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build gc && !purego + +#include "textflag.h" + +// This implementation of Poly1305 uses the vector facility (vx) +// to process up to 2 blocks (32 bytes) per iteration using an +// algorithm based on the one described in: +// +// NEON crypto, Daniel J. Bernstein & Peter Schwabe +// https://cryptojedi.org/papers/neoncrypto-20120320.pdf +// +// This algorithm uses 5 26-bit limbs to represent a 130-bit +// value. These limbs are, for the most part, zero extended and +// placed into 64-bit vector register elements. Each vector +// register is 128-bits wide and so holds 2 of these elements. +// Using 26-bit limbs allows us plenty of headroom to accommodate +// accumulations before and after multiplication without +// overflowing either 32-bits (before multiplication) or 64-bits +// (after multiplication). +// +// In order to parallelise the operations required to calculate +// the sum we use two separate accumulators and then sum those +// in an extra final step. For compatibility with the generic +// implementation we perform this summation at the end of every +// updateVX call. +// +// To use two accumulators we must multiply the message blocks +// by r² rather than r. Only the final message block should be +// multiplied by r. +// +// Example: +// +// We want to calculate the sum (h) for a 64 byte message (m): +// +// h = m[0:16]r⁴ + m[16:32]r³ + m[32:48]r² + m[48:64]r +// +// To do this we split the calculation into the even indices +// and odd indices of the message. These form our SIMD 'lanes': +// +// h = m[ 0:16]r⁴ + m[32:48]r² + <- lane 0 +// m[16:32]r³ + m[48:64]r <- lane 1 +// +// To calculate this iteratively we refactor so that both lanes +// are written in terms of r² and r: +// +// h = (m[ 0:16]r² + m[32:48])r² + <- lane 0 +// (m[16:32]r² + m[48:64])r <- lane 1 +// ^ ^ +// | coefficients for second iteration +// coefficients for first iteration +// +// So in this case we would have two iterations. In the first +// both lanes are multiplied by r². In the second only the +// first lane is multiplied by r² and the second lane is +// instead multiplied by r. This gives use the odd and even +// powers of r that we need from the original equation. +// +// Notation: +// +// h - accumulator +// r - key +// m - message +// +// [a, b] - SIMD register holding two 64-bit values +// [a, b, c, d] - SIMD register holding four 32-bit values +// xᵢ[n] - limb n of variable x with bit width i +// +// Limbs are expressed in little endian order, so for 26-bit +// limbs x₂₆[4] will be the most significant limb and x₂₆[0] +// will be the least significant limb. + +// masking constants +#define MOD24 V0 // [0x0000000000ffffff, 0x0000000000ffffff] - mask low 24-bits +#define MOD26 V1 // [0x0000000003ffffff, 0x0000000003ffffff] - mask low 26-bits + +// expansion constants (see EXPAND macro) +#define EX0 V2 +#define EX1 V3 +#define EX2 V4 + +// key (r², r or 1 depending on context) +#define R_0 V5 +#define R_1 V6 +#define R_2 V7 +#define R_3 V8 +#define R_4 V9 + +// precalculated coefficients (5r², 5r or 0 depending on context) +#define R5_1 V10 +#define R5_2 V11 +#define R5_3 V12 +#define R5_4 V13 + +// message block (m) +#define M_0 V14 +#define M_1 V15 +#define M_2 V16 +#define M_3 V17 +#define M_4 V18 + +// accumulator (h) +#define H_0 V19 +#define H_1 V20 +#define H_2 V21 +#define H_3 V22 +#define H_4 V23 + +// temporary registers (for short-lived values) +#define T_0 V24 +#define T_1 V25 +#define T_2 V26 +#define T_3 V27 +#define T_4 V28 + +GLOBL ·constants<>(SB), RODATA, $0x30 +// EX0 +DATA ·constants<>+0x00(SB)/8, $0x0006050403020100 +DATA ·constants<>+0x08(SB)/8, $0x1016151413121110 +// EX1 +DATA ·constants<>+0x10(SB)/8, $0x060c0b0a09080706 +DATA ·constants<>+0x18(SB)/8, $0x161c1b1a19181716 +// EX2 +DATA ·constants<>+0x20(SB)/8, $0x0d0d0d0d0d0f0e0d +DATA ·constants<>+0x28(SB)/8, $0x1d1d1d1d1d1f1e1d + +// MULTIPLY multiplies each lane of f and g, partially reduced +// modulo 2¹³⁰ - 5. The result, h, consists of partial products +// in each lane that need to be reduced further to produce the +// final result. +// +// h₁₃₀ = (f₁₃₀g₁₃₀) % 2¹³⁰ + (5f₁₃₀g₁₃₀) / 2¹³⁰ +// +// Note that the multiplication by 5 of the high bits is +// achieved by precalculating the multiplication of four of the +// g coefficients by 5. These are g51-g54. +#define MULTIPLY(f0, f1, f2, f3, f4, g0, g1, g2, g3, g4, g51, g52, g53, g54, h0, h1, h2, h3, h4) \ + VMLOF f0, g0, h0 \ + VMLOF f0, g3, h3 \ + VMLOF f0, g1, h1 \ + VMLOF f0, g4, h4 \ + VMLOF f0, g2, h2 \ + VMLOF f1, g54, T_0 \ + VMLOF f1, g2, T_3 \ + VMLOF f1, g0, T_1 \ + VMLOF f1, g3, T_4 \ + VMLOF f1, g1, T_2 \ + VMALOF f2, g53, h0, h0 \ + VMALOF f2, g1, h3, h3 \ + VMALOF f2, g54, h1, h1 \ + VMALOF f2, g2, h4, h4 \ + VMALOF f2, g0, h2, h2 \ + VMALOF f3, g52, T_0, T_0 \ + VMALOF f3, g0, T_3, T_3 \ + VMALOF f3, g53, T_1, T_1 \ + VMALOF f3, g1, T_4, T_4 \ + VMALOF f3, g54, T_2, T_2 \ + VMALOF f4, g51, h0, h0 \ + VMALOF f4, g54, h3, h3 \ + VMALOF f4, g52, h1, h1 \ + VMALOF f4, g0, h4, h4 \ + VMALOF f4, g53, h2, h2 \ + VAG T_0, h0, h0 \ + VAG T_3, h3, h3 \ + VAG T_1, h1, h1 \ + VAG T_4, h4, h4 \ + VAG T_2, h2, h2 + +// REDUCE performs the following carry operations in four +// stages, as specified in Bernstein & Schwabe: +// +// 1: h₂₆[0]->h₂₆[1] h₂₆[3]->h₂₆[4] +// 2: h₂₆[1]->h₂₆[2] h₂₆[4]->h₂₆[0] +// 3: h₂₆[0]->h₂₆[1] h₂₆[2]->h₂₆[3] +// 4: h₂₆[3]->h₂₆[4] +// +// The result is that all of the limbs are limited to 26-bits +// except for h₂₆[1] and h₂₆[4] which are limited to 27-bits. +// +// Note that although each limb is aligned at 26-bit intervals +// they may contain values that exceed 2²⁶ - 1, hence the need +// to carry the excess bits in each limb. +#define REDUCE(h0, h1, h2, h3, h4) \ + VESRLG $26, h0, T_0 \ + VESRLG $26, h3, T_1 \ + VN MOD26, h0, h0 \ + VN MOD26, h3, h3 \ + VAG T_0, h1, h1 \ + VAG T_1, h4, h4 \ + VESRLG $26, h1, T_2 \ + VESRLG $26, h4, T_3 \ + VN MOD26, h1, h1 \ + VN MOD26, h4, h4 \ + VESLG $2, T_3, T_4 \ + VAG T_3, T_4, T_4 \ + VAG T_2, h2, h2 \ + VAG T_4, h0, h0 \ + VESRLG $26, h2, T_0 \ + VESRLG $26, h0, T_1 \ + VN MOD26, h2, h2 \ + VN MOD26, h0, h0 \ + VAG T_0, h3, h3 \ + VAG T_1, h1, h1 \ + VESRLG $26, h3, T_2 \ + VN MOD26, h3, h3 \ + VAG T_2, h4, h4 + +// EXPAND splits the 128-bit little-endian values in0 and in1 +// into 26-bit big-endian limbs and places the results into +// the first and second lane of d₂₆[0:4] respectively. +// +// The EX0, EX1 and EX2 constants are arrays of byte indices +// for permutation. The permutation both reverses the bytes +// in the input and ensures the bytes are copied into the +// destination limb ready to be shifted into their final +// position. +#define EXPAND(in0, in1, d0, d1, d2, d3, d4) \ + VPERM in0, in1, EX0, d0 \ + VPERM in0, in1, EX1, d2 \ + VPERM in0, in1, EX2, d4 \ + VESRLG $26, d0, d1 \ + VESRLG $30, d2, d3 \ + VESRLG $4, d2, d2 \ + VN MOD26, d0, d0 \ // [in0₂₆[0], in1₂₆[0]] + VN MOD26, d3, d3 \ // [in0₂₆[3], in1₂₆[3]] + VN MOD26, d1, d1 \ // [in0₂₆[1], in1₂₆[1]] + VN MOD24, d4, d4 \ // [in0₂₆[4], in1₂₆[4]] + VN MOD26, d2, d2 // [in0₂₆[2], in1₂₆[2]] + +// func updateVX(state *macState, msg []byte) +TEXT ·updateVX(SB), NOSPLIT, $0 + MOVD state+0(FP), R1 + LMG msg+8(FP), R2, R3 // R2=msg_base, R3=msg_len + + // load EX0, EX1 and EX2 + MOVD $·constants<>(SB), R5 + VLM (R5), EX0, EX2 + + // generate masks + VGMG $(64-24), $63, MOD24 // [0x00ffffff, 0x00ffffff] + VGMG $(64-26), $63, MOD26 // [0x03ffffff, 0x03ffffff] + + // load h (accumulator) and r (key) from state + VZERO T_1 // [0, 0] + VL 0(R1), T_0 // [h₆₄[0], h₆₄[1]] + VLEG $0, 16(R1), T_1 // [h₆₄[2], 0] + VL 24(R1), T_2 // [r₆₄[0], r₆₄[1]] + VPDI $0, T_0, T_2, T_3 // [h₆₄[0], r₆₄[0]] + VPDI $5, T_0, T_2, T_4 // [h₆₄[1], r₆₄[1]] + + // unpack h and r into 26-bit limbs + // note: h₆₄[2] may have the low 3 bits set, so h₂₆[4] is a 27-bit value + VN MOD26, T_3, H_0 // [h₂₆[0], r₂₆[0]] + VZERO H_1 // [0, 0] + VZERO H_3 // [0, 0] + VGMG $(64-12-14), $(63-12), T_0 // [0x03fff000, 0x03fff000] - 26-bit mask with low 12 bits masked out + VESLG $24, T_1, T_1 // [h₆₄[2]<<24, 0] + VERIMG $-26&63, T_3, MOD26, H_1 // [h₂₆[1], r₂₆[1]] + VESRLG $+52&63, T_3, H_2 // [h₂₆[2], r₂₆[2]] - low 12 bits only + VERIMG $-14&63, T_4, MOD26, H_3 // [h₂₆[1], r₂₆[1]] + VESRLG $40, T_4, H_4 // [h₂₆[4], r₂₆[4]] - low 24 bits only + VERIMG $+12&63, T_4, T_0, H_2 // [h₂₆[2], r₂₆[2]] - complete + VO T_1, H_4, H_4 // [h₂₆[4], r₂₆[4]] - complete + + // replicate r across all 4 vector elements + VREPF $3, H_0, R_0 // [r₂₆[0], r₂₆[0], r₂₆[0], r₂₆[0]] + VREPF $3, H_1, R_1 // [r₂₆[1], r₂₆[1], r₂₆[1], r₂₆[1]] + VREPF $3, H_2, R_2 // [r₂₆[2], r₂₆[2], r₂₆[2], r₂₆[2]] + VREPF $3, H_3, R_3 // [r₂₆[3], r₂₆[3], r₂₆[3], r₂₆[3]] + VREPF $3, H_4, R_4 // [r₂₆[4], r₂₆[4], r₂₆[4], r₂₆[4]] + + // zero out lane 1 of h + VLEIG $1, $0, H_0 // [h₂₆[0], 0] + VLEIG $1, $0, H_1 // [h₂₆[1], 0] + VLEIG $1, $0, H_2 // [h₂₆[2], 0] + VLEIG $1, $0, H_3 // [h₂₆[3], 0] + VLEIG $1, $0, H_4 // [h₂₆[4], 0] + + // calculate 5r (ignore least significant limb) + VREPIF $5, T_0 + VMLF T_0, R_1, R5_1 // [5r₂₆[1], 5r₂₆[1], 5r₂₆[1], 5r₂₆[1]] + VMLF T_0, R_2, R5_2 // [5r₂₆[2], 5r₂₆[2], 5r₂₆[2], 5r₂₆[2]] + VMLF T_0, R_3, R5_3 // [5r₂₆[3], 5r₂₆[3], 5r₂₆[3], 5r₂₆[3]] + VMLF T_0, R_4, R5_4 // [5r₂₆[4], 5r₂₆[4], 5r₂₆[4], 5r₂₆[4]] + + // skip r² calculation if we are only calculating one block + CMPBLE R3, $16, skip + + // calculate r² + MULTIPLY(R_0, R_1, R_2, R_3, R_4, R_0, R_1, R_2, R_3, R_4, R5_1, R5_2, R5_3, R5_4, M_0, M_1, M_2, M_3, M_4) + REDUCE(M_0, M_1, M_2, M_3, M_4) + VGBM $0x0f0f, T_0 + VERIMG $0, M_0, T_0, R_0 // [r₂₆[0], r²₂₆[0], r₂₆[0], r²₂₆[0]] + VERIMG $0, M_1, T_0, R_1 // [r₂₆[1], r²₂₆[1], r₂₆[1], r²₂₆[1]] + VERIMG $0, M_2, T_0, R_2 // [r₂₆[2], r²₂₆[2], r₂₆[2], r²₂₆[2]] + VERIMG $0, M_3, T_0, R_3 // [r₂₆[3], r²₂₆[3], r₂₆[3], r²₂₆[3]] + VERIMG $0, M_4, T_0, R_4 // [r₂₆[4], r²₂₆[4], r₂₆[4], r²₂₆[4]] + + // calculate 5r² (ignore least significant limb) + VREPIF $5, T_0 + VMLF T_0, R_1, R5_1 // [5r₂₆[1], 5r²₂₆[1], 5r₂₆[1], 5r²₂₆[1]] + VMLF T_0, R_2, R5_2 // [5r₂₆[2], 5r²₂₆[2], 5r₂₆[2], 5r²₂₆[2]] + VMLF T_0, R_3, R5_3 // [5r₂₆[3], 5r²₂₆[3], 5r₂₆[3], 5r²₂₆[3]] + VMLF T_0, R_4, R5_4 // [5r₂₆[4], 5r²₂₆[4], 5r₂₆[4], 5r²₂₆[4]] + +loop: + CMPBLE R3, $32, b2 // 2 or fewer blocks remaining, need to change key coefficients + + // load next 2 blocks from message + VLM (R2), T_0, T_1 + + // update message slice + SUB $32, R3 + MOVD $32(R2), R2 + + // unpack message blocks into 26-bit big-endian limbs + EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4) + + // add 2¹²⁸ to each message block value + VLEIB $4, $1, M_4 + VLEIB $12, $1, M_4 + +multiply: + // accumulate the incoming message + VAG H_0, M_0, M_0 + VAG H_3, M_3, M_3 + VAG H_1, M_1, M_1 + VAG H_4, M_4, M_4 + VAG H_2, M_2, M_2 + + // multiply the accumulator by the key coefficient + MULTIPLY(M_0, M_1, M_2, M_3, M_4, R_0, R_1, R_2, R_3, R_4, R5_1, R5_2, R5_3, R5_4, H_0, H_1, H_2, H_3, H_4) + + // carry and partially reduce the partial products + REDUCE(H_0, H_1, H_2, H_3, H_4) + + CMPBNE R3, $0, loop + +finish: + // sum lane 0 and lane 1 and put the result in lane 1 + VZERO T_0 + VSUMQG H_0, T_0, H_0 + VSUMQG H_3, T_0, H_3 + VSUMQG H_1, T_0, H_1 + VSUMQG H_4, T_0, H_4 + VSUMQG H_2, T_0, H_2 + + // reduce again after summation + // TODO(mundaym): there might be a more efficient way to do this + // now that we only have 1 active lane. For example, we could + // simultaneously pack the values as we reduce them. + REDUCE(H_0, H_1, H_2, H_3, H_4) + + // carry h[1] through to h[4] so that only h[4] can exceed 2²⁶ - 1 + // TODO(mundaym): in testing this final carry was unnecessary. + // Needs a proof before it can be removed though. + VESRLG $26, H_1, T_1 + VN MOD26, H_1, H_1 + VAQ T_1, H_2, H_2 + VESRLG $26, H_2, T_2 + VN MOD26, H_2, H_2 + VAQ T_2, H_3, H_3 + VESRLG $26, H_3, T_3 + VN MOD26, H_3, H_3 + VAQ T_3, H_4, H_4 + + // h is now < 2(2¹³⁰ - 5) + // Pack each lane in h₂₆[0:4] into h₁₂₈[0:1]. + VESLG $26, H_1, H_1 + VESLG $26, H_3, H_3 + VO H_0, H_1, H_0 + VO H_2, H_3, H_2 + VESLG $4, H_2, H_2 + VLEIB $7, $48, H_1 + VSLB H_1, H_2, H_2 + VO H_0, H_2, H_0 + VLEIB $7, $104, H_1 + VSLB H_1, H_4, H_3 + VO H_3, H_0, H_0 + VLEIB $7, $24, H_1 + VSRLB H_1, H_4, H_1 + + // update state + VSTEG $1, H_0, 0(R1) + VSTEG $0, H_0, 8(R1) + VSTEG $1, H_1, 16(R1) + RET + +b2: // 2 or fewer blocks remaining + CMPBLE R3, $16, b1 + + // Load the 2 remaining blocks (17-32 bytes remaining). + MOVD $-17(R3), R0 // index of final byte to load modulo 16 + VL (R2), T_0 // load full 16 byte block + VLL R0, 16(R2), T_1 // load final (possibly partial) block and pad with zeros to 16 bytes + + // The Poly1305 algorithm requires that a 1 bit be appended to + // each message block. If the final block is less than 16 bytes + // long then it is easiest to insert the 1 before the message + // block is split into 26-bit limbs. If, on the other hand, the + // final message block is 16 bytes long then we append the 1 bit + // after expansion as normal. + MOVBZ $1, R0 + MOVD $-16(R3), R3 // index of byte in last block to insert 1 at (could be 16) + CMPBEQ R3, $16, 2(PC) // skip the insertion if the final block is 16 bytes long + VLVGB R3, R0, T_1 // insert 1 into the byte at index R3 + + // Split both blocks into 26-bit limbs in the appropriate lanes. + EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4) + + // Append a 1 byte to the end of the second to last block. + VLEIB $4, $1, M_4 + + // Append a 1 byte to the end of the last block only if it is a + // full 16 byte block. + CMPBNE R3, $16, 2(PC) + VLEIB $12, $1, M_4 + + // Finally, set up the coefficients for the final multiplication. + // We have previously saved r and 5r in the 32-bit even indexes + // of the R_[0-4] and R5_[1-4] coefficient registers. + // + // We want lane 0 to be multiplied by r² so that can be kept the + // same. We want lane 1 to be multiplied by r so we need to move + // the saved r value into the 32-bit odd index in lane 1 by + // rotating the 64-bit lane by 32. + VGBM $0x00ff, T_0 // [0, 0xffffffffffffffff] - mask lane 1 only + VERIMG $32, R_0, T_0, R_0 // [_, r²₂₆[0], _, r₂₆[0]] + VERIMG $32, R_1, T_0, R_1 // [_, r²₂₆[1], _, r₂₆[1]] + VERIMG $32, R_2, T_0, R_2 // [_, r²₂₆[2], _, r₂₆[2]] + VERIMG $32, R_3, T_0, R_3 // [_, r²₂₆[3], _, r₂₆[3]] + VERIMG $32, R_4, T_0, R_4 // [_, r²₂₆[4], _, r₂₆[4]] + VERIMG $32, R5_1, T_0, R5_1 // [_, 5r²₂₆[1], _, 5r₂₆[1]] + VERIMG $32, R5_2, T_0, R5_2 // [_, 5r²₂₆[2], _, 5r₂₆[2]] + VERIMG $32, R5_3, T_0, R5_3 // [_, 5r²₂₆[3], _, 5r₂₆[3]] + VERIMG $32, R5_4, T_0, R5_4 // [_, 5r²₂₆[4], _, 5r₂₆[4]] + + MOVD $0, R3 + BR multiply + +skip: + CMPBEQ R3, $0, finish + +b1: // 1 block remaining + + // Load the final block (1-16 bytes). This will be placed into + // lane 0. + MOVD $-1(R3), R0 + VLL R0, (R2), T_0 // pad to 16 bytes with zeros + + // The Poly1305 algorithm requires that a 1 bit be appended to + // each message block. If the final block is less than 16 bytes + // long then it is easiest to insert the 1 before the message + // block is split into 26-bit limbs. If, on the other hand, the + // final message block is 16 bytes long then we append the 1 bit + // after expansion as normal. + MOVBZ $1, R0 + CMPBEQ R3, $16, 2(PC) + VLVGB R3, R0, T_0 + + // Set the message block in lane 1 to the value 0 so that it + // can be accumulated without affecting the final result. + VZERO T_1 + + // Split the final message block into 26-bit limbs in lane 0. + // Lane 1 will be contain 0. + EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4) + + // Append a 1 byte to the end of the last block only if it is a + // full 16 byte block. + CMPBNE R3, $16, 2(PC) + VLEIB $4, $1, M_4 + + // We have previously saved r and 5r in the 32-bit even indexes + // of the R_[0-4] and R5_[1-4] coefficient registers. + // + // We want lane 0 to be multiplied by r so we need to move the + // saved r value into the 32-bit odd index in lane 0. We want + // lane 1 to be set to the value 1. This makes multiplication + // a no-op. We do this by setting lane 1 in every register to 0 + // and then just setting the 32-bit index 3 in R_0 to 1. + VZERO T_0 + MOVD $0, R0 + MOVD $0x10111213, R12 + VLVGP R12, R0, T_1 // [_, 0x10111213, _, 0x00000000] + VPERM T_0, R_0, T_1, R_0 // [_, r₂₆[0], _, 0] + VPERM T_0, R_1, T_1, R_1 // [_, r₂₆[1], _, 0] + VPERM T_0, R_2, T_1, R_2 // [_, r₂₆[2], _, 0] + VPERM T_0, R_3, T_1, R_3 // [_, r₂₆[3], _, 0] + VPERM T_0, R_4, T_1, R_4 // [_, r₂₆[4], _, 0] + VPERM T_0, R5_1, T_1, R5_1 // [_, 5r₂₆[1], _, 0] + VPERM T_0, R5_2, T_1, R5_2 // [_, 5r₂₆[2], _, 0] + VPERM T_0, R5_3, T_1, R5_3 // [_, 5r₂₆[3], _, 0] + VPERM T_0, R5_4, T_1, R5_4 // [_, 5r₂₆[4], _, 0] + + // Set the value of lane 1 to be 1. + VLEIF $3, $1, R_0 // [_, r₂₆[0], _, 1] + + MOVD $0, R3 + BR multiply diff --git a/pkg/proto/ssh/kex.go b/pkg/proto/ssh/kex.go new file mode 100644 index 0000000..8a05f79 --- /dev/null +++ b/pkg/proto/ssh/kex.go @@ -0,0 +1,786 @@ +// Copyright 2013 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "crypto" + "crypto/ecdsa" + "crypto/elliptic" + "crypto/rand" + "crypto/subtle" + "encoding/binary" + "errors" + "fmt" + "io" + "math/big" + + "golang.org/x/crypto/curve25519" +) + +const ( + kexAlgoDH1SHA1 = "diffie-hellman-group1-sha1" + kexAlgoDH14SHA1 = "diffie-hellman-group14-sha1" + kexAlgoDH14SHA256 = "diffie-hellman-group14-sha256" + kexAlgoDH16SHA512 = "diffie-hellman-group16-sha512" + kexAlgoECDH256 = "ecdh-sha2-nistp256" + kexAlgoECDH384 = "ecdh-sha2-nistp384" + kexAlgoECDH521 = "ecdh-sha2-nistp521" + kexAlgoCurve25519SHA256LibSSH = "curve25519-sha256@libssh.org" + kexAlgoCurve25519SHA256 = "curve25519-sha256" + + // For the following kex only the client half contains a production + // ready implementation. The server half only consists of a minimal + // implementation to satisfy the automated tests. + kexAlgoDHGEXSHA1 = "diffie-hellman-group-exchange-sha1" + kexAlgoDHGEXSHA256 = "diffie-hellman-group-exchange-sha256" +) + +// kexResult captures the outcome of a key exchange. +type kexResult struct { + // Session hash. See also RFC 4253, section 8. + H []byte + + // Shared secret. See also RFC 4253, section 8. + K []byte + + // Host key as hashed into H. + HostKey []byte + + // Signature of H. + Signature []byte + + // A cryptographic hash function that matches the security + // level of the key exchange algorithm. It is used for + // calculating H, and for deriving keys from H and K. + Hash crypto.Hash + + // The session ID, which is the first H computed. This is used + // to derive key material inside the transport. + SessionID []byte +} + +// handshakeMagics contains data that is always included in the +// session hash. +type handshakeMagics struct { + clientVersion, serverVersion []byte + clientKexInit, serverKexInit []byte +} + +func (m *handshakeMagics) write(w io.Writer) { + writeString(w, m.clientVersion) + writeString(w, m.serverVersion) + writeString(w, m.clientKexInit) + writeString(w, m.serverKexInit) +} + +// kexAlgorithm abstracts different key exchange algorithms. +type kexAlgorithm interface { + // Server runs server-side key agreement, signing the result + // with a hostkey. algo is the negotiated algorithm, and may + // be a certificate type. + Server(p packetConn, rand io.Reader, magics *handshakeMagics, s AlgorithmSigner, algo string) (*kexResult, error) + + // Client runs the client-side key agreement. Caller is + // responsible for verifying the host key signature. + Client(p packetConn, rand io.Reader, magics *handshakeMagics) (*kexResult, error) +} + +// dhGroup is a multiplicative group suitable for implementing Diffie-Hellman key agreement. +type dhGroup struct { + g, p, pMinus1 *big.Int + hashFunc crypto.Hash +} + +func (group *dhGroup) diffieHellman(theirPublic, myPrivate *big.Int) (*big.Int, error) { + if theirPublic.Cmp(bigOne) <= 0 || theirPublic.Cmp(group.pMinus1) >= 0 { + return nil, errors.New("ssh: DH parameter out of bounds") + } + return new(big.Int).Exp(theirPublic, myPrivate, group.p), nil +} + +func (group *dhGroup) Client(c packetConn, randSource io.Reader, magics *handshakeMagics) (*kexResult, error) { + var x *big.Int + for { + var err error + if x, err = rand.Int(randSource, group.pMinus1); err != nil { + return nil, err + } + if x.Sign() > 0 { + break + } + } + + X := new(big.Int).Exp(group.g, x, group.p) + kexDHInit := kexDHInitMsg{ + X: X, + } + if err := c.writePacket(Marshal(&kexDHInit)); err != nil { + return nil, err + } + + packet, err := c.readPacket() + if err != nil { + return nil, err + } + + var kexDHReply kexDHReplyMsg + if err = Unmarshal(packet, &kexDHReply); err != nil { + return nil, err + } + + ki, err := group.diffieHellman(kexDHReply.Y, x) + if err != nil { + return nil, err + } + + h := group.hashFunc.New() + magics.write(h) + writeString(h, kexDHReply.HostKey) + writeInt(h, X) + writeInt(h, kexDHReply.Y) + K := make([]byte, intLength(ki)) + marshalInt(K, ki) + h.Write(K) + + return &kexResult{ + H: h.Sum(nil), + K: K, + HostKey: kexDHReply.HostKey, + Signature: kexDHReply.Signature, + Hash: group.hashFunc, + }, nil +} + +func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { + packet, err := c.readPacket() + if err != nil { + return + } + var kexDHInit kexDHInitMsg + if err = Unmarshal(packet, &kexDHInit); err != nil { + return + } + + var y *big.Int + for { + if y, err = rand.Int(randSource, group.pMinus1); err != nil { + return + } + if y.Sign() > 0 { + break + } + } + + Y := new(big.Int).Exp(group.g, y, group.p) + ki, err := group.diffieHellman(kexDHInit.X, y) + if err != nil { + return nil, err + } + + hostKeyBytes := priv.PublicKey().Marshal() + + h := group.hashFunc.New() + magics.write(h) + writeString(h, hostKeyBytes) + writeInt(h, kexDHInit.X) + writeInt(h, Y) + + K := make([]byte, intLength(ki)) + marshalInt(K, ki) + h.Write(K) + + H := h.Sum(nil) + + // H is already a hash, but the hostkey signing will apply its + // own key-specific hash algorithm. + sig, err := signAndMarshal(priv, randSource, H, algo) + if err != nil { + return nil, err + } + + kexDHReply := kexDHReplyMsg{ + HostKey: hostKeyBytes, + Y: Y, + Signature: sig, + } + packet = Marshal(&kexDHReply) + + err = c.writePacket(packet) + return &kexResult{ + H: H, + K: K, + HostKey: hostKeyBytes, + Signature: sig, + Hash: group.hashFunc, + }, err +} + +// ecdh performs Elliptic Curve Diffie-Hellman key exchange as +// described in RFC 5656, section 4. +type ecdh struct { + curve elliptic.Curve +} + +func (kex *ecdh) Client(c packetConn, rand io.Reader, magics *handshakeMagics) (*kexResult, error) { + ephKey, err := ecdsa.GenerateKey(kex.curve, rand) + if err != nil { + return nil, err + } + + kexInit := kexECDHInitMsg{ + ClientPubKey: elliptic.Marshal(kex.curve, ephKey.PublicKey.X, ephKey.PublicKey.Y), + } + + serialized := Marshal(&kexInit) + if err := c.writePacket(serialized); err != nil { + return nil, err + } + + packet, err := c.readPacket() + if err != nil { + return nil, err + } + + var reply kexECDHReplyMsg + if err = Unmarshal(packet, &reply); err != nil { + return nil, err + } + + x, y, err := unmarshalECKey(kex.curve, reply.EphemeralPubKey) + if err != nil { + return nil, err + } + + // generate shared secret + secret, _ := kex.curve.ScalarMult(x, y, ephKey.D.Bytes()) + + h := ecHash(kex.curve).New() + magics.write(h) + writeString(h, reply.HostKey) + writeString(h, kexInit.ClientPubKey) + writeString(h, reply.EphemeralPubKey) + K := make([]byte, intLength(secret)) + marshalInt(K, secret) + h.Write(K) + + return &kexResult{ + H: h.Sum(nil), + K: K, + HostKey: reply.HostKey, + Signature: reply.Signature, + Hash: ecHash(kex.curve), + }, nil +} + +// unmarshalECKey parses and checks an EC key. +func unmarshalECKey(curve elliptic.Curve, pubkey []byte) (x, y *big.Int, err error) { + x, y = elliptic.Unmarshal(curve, pubkey) + if x == nil { + return nil, nil, errors.New("ssh: elliptic.Unmarshal failure") + } + if !validateECPublicKey(curve, x, y) { + return nil, nil, errors.New("ssh: public key not on curve") + } + return x, y, nil +} + +// validateECPublicKey checks that the point is a valid public key for +// the given curve. See [SEC1], 3.2.2 +func validateECPublicKey(curve elliptic.Curve, x, y *big.Int) bool { + if x.Sign() == 0 && y.Sign() == 0 { + return false + } + + if x.Cmp(curve.Params().P) >= 0 { + return false + } + + if y.Cmp(curve.Params().P) >= 0 { + return false + } + + if !curve.IsOnCurve(x, y) { + return false + } + + // We don't check if N * PubKey == 0, since + // + // - the NIST curves have cofactor = 1, so this is implicit. + // (We don't foresee an implementation that supports non NIST + // curves) + // + // - for ephemeral keys, we don't need to worry about small + // subgroup attacks. + return true +} + +func (kex *ecdh) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { + packet, err := c.readPacket() + if err != nil { + return nil, err + } + + var kexECDHInit kexECDHInitMsg + if err = Unmarshal(packet, &kexECDHInit); err != nil { + return nil, err + } + + clientX, clientY, err := unmarshalECKey(kex.curve, kexECDHInit.ClientPubKey) + if err != nil { + return nil, err + } + + // We could cache this key across multiple users/multiple + // connection attempts, but the benefit is small. OpenSSH + // generates a new key for each incoming connection. + ephKey, err := ecdsa.GenerateKey(kex.curve, rand) + if err != nil { + return nil, err + } + + hostKeyBytes := priv.PublicKey().Marshal() + + serializedEphKey := elliptic.Marshal(kex.curve, ephKey.PublicKey.X, ephKey.PublicKey.Y) + + // generate shared secret + secret, _ := kex.curve.ScalarMult(clientX, clientY, ephKey.D.Bytes()) + + h := ecHash(kex.curve).New() + magics.write(h) + writeString(h, hostKeyBytes) + writeString(h, kexECDHInit.ClientPubKey) + writeString(h, serializedEphKey) + + K := make([]byte, intLength(secret)) + marshalInt(K, secret) + h.Write(K) + + H := h.Sum(nil) + + // H is already a hash, but the hostkey signing will apply its + // own key-specific hash algorithm. + sig, err := signAndMarshal(priv, rand, H, algo) + if err != nil { + return nil, err + } + + reply := kexECDHReplyMsg{ + EphemeralPubKey: serializedEphKey, + HostKey: hostKeyBytes, + Signature: sig, + } + + serialized := Marshal(&reply) + if err := c.writePacket(serialized); err != nil { + return nil, err + } + + return &kexResult{ + H: H, + K: K, + HostKey: reply.HostKey, + Signature: sig, + Hash: ecHash(kex.curve), + }, nil +} + +// ecHash returns the hash to match the given elliptic curve, see RFC +// 5656, section 6.2.1 +func ecHash(curve elliptic.Curve) crypto.Hash { + bitSize := curve.Params().BitSize + switch { + case bitSize <= 256: + return crypto.SHA256 + case bitSize <= 384: + return crypto.SHA384 + } + return crypto.SHA512 +} + +var kexAlgoMap = map[string]kexAlgorithm{} + +func init() { + // This is the group called diffie-hellman-group1-sha1 in + // RFC 4253 and Oakley Group 2 in RFC 2409. + p, _ := new(big.Int).SetString("FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF", 16) + kexAlgoMap[kexAlgoDH1SHA1] = &dhGroup{ + g: new(big.Int).SetInt64(2), + p: p, + pMinus1: new(big.Int).Sub(p, bigOne), + hashFunc: crypto.SHA1, + } + + // This are the groups called diffie-hellman-group14-sha1 and + // diffie-hellman-group14-sha256 in RFC 4253 and RFC 8268, + // and Oakley Group 14 in RFC 3526. + p, _ = new(big.Int).SetString("FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF6955817183995497CEA956AE515D2261898FA051015728E5A8AACAA68FFFFFFFFFFFFFFFF", 16) + group14 := &dhGroup{ + g: new(big.Int).SetInt64(2), + p: p, + pMinus1: new(big.Int).Sub(p, bigOne), + } + + kexAlgoMap[kexAlgoDH14SHA1] = &dhGroup{ + g: group14.g, p: group14.p, pMinus1: group14.pMinus1, + hashFunc: crypto.SHA1, + } + kexAlgoMap[kexAlgoDH14SHA256] = &dhGroup{ + g: group14.g, p: group14.p, pMinus1: group14.pMinus1, + hashFunc: crypto.SHA256, + } + + // This is the group called diffie-hellman-group16-sha512 in RFC + // 8268 and Oakley Group 16 in RFC 3526. + p, _ = new(big.Int).SetString("FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF6955817183995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7DB3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D2261AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200CBBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFCE0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B2699C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934063199FFFFFFFFFFFFFFFF", 16) + + kexAlgoMap[kexAlgoDH16SHA512] = &dhGroup{ + g: new(big.Int).SetInt64(2), + p: p, + pMinus1: new(big.Int).Sub(p, bigOne), + hashFunc: crypto.SHA512, + } + + kexAlgoMap[kexAlgoECDH521] = &ecdh{elliptic.P521()} + kexAlgoMap[kexAlgoECDH384] = &ecdh{elliptic.P384()} + kexAlgoMap[kexAlgoECDH256] = &ecdh{elliptic.P256()} + kexAlgoMap[kexAlgoCurve25519SHA256] = &curve25519sha256{} + kexAlgoMap[kexAlgoCurve25519SHA256LibSSH] = &curve25519sha256{} + kexAlgoMap[kexAlgoDHGEXSHA1] = &dhGEXSHA{hashFunc: crypto.SHA1} + kexAlgoMap[kexAlgoDHGEXSHA256] = &dhGEXSHA{hashFunc: crypto.SHA256} +} + +// curve25519sha256 implements the curve25519-sha256 (formerly known as +// curve25519-sha256@libssh.org) key exchange method, as described in RFC 8731. +type curve25519sha256 struct{} + +type curve25519KeyPair struct { + priv [32]byte + pub [32]byte +} + +func (kp *curve25519KeyPair) generate(rand io.Reader) error { + if _, err := io.ReadFull(rand, kp.priv[:]); err != nil { + return err + } + curve25519.ScalarBaseMult(&kp.pub, &kp.priv) + return nil +} + +// curve25519Zeros is just an array of 32 zero bytes so that we have something +// convenient to compare against in order to reject curve25519 points with the +// wrong order. +var curve25519Zeros [32]byte + +func (kex *curve25519sha256) Client(c packetConn, rand io.Reader, magics *handshakeMagics) (*kexResult, error) { + var kp curve25519KeyPair + if err := kp.generate(rand); err != nil { + return nil, err + } + if err := c.writePacket(Marshal(&kexECDHInitMsg{kp.pub[:]})); err != nil { + return nil, err + } + + packet, err := c.readPacket() + if err != nil { + return nil, err + } + + var reply kexECDHReplyMsg + if err = Unmarshal(packet, &reply); err != nil { + return nil, err + } + if len(reply.EphemeralPubKey) != 32 { + return nil, errors.New("ssh: peer's curve25519 public value has wrong length") + } + + var servPub, secret [32]byte + copy(servPub[:], reply.EphemeralPubKey) + curve25519.ScalarMult(&secret, &kp.priv, &servPub) + if subtle.ConstantTimeCompare(secret[:], curve25519Zeros[:]) == 1 { + return nil, errors.New("ssh: peer's curve25519 public value has wrong order") + } + + h := crypto.SHA256.New() + magics.write(h) + writeString(h, reply.HostKey) + writeString(h, kp.pub[:]) + writeString(h, reply.EphemeralPubKey) + + ki := new(big.Int).SetBytes(secret[:]) + K := make([]byte, intLength(ki)) + marshalInt(K, ki) + h.Write(K) + + return &kexResult{ + H: h.Sum(nil), + K: K, + HostKey: reply.HostKey, + Signature: reply.Signature, + Hash: crypto.SHA256, + }, nil +} + +func (kex *curve25519sha256) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { + packet, err := c.readPacket() + if err != nil { + return + } + var kexInit kexECDHInitMsg + if err = Unmarshal(packet, &kexInit); err != nil { + return + } + + if len(kexInit.ClientPubKey) != 32 { + return nil, errors.New("ssh: peer's curve25519 public value has wrong length") + } + + var kp curve25519KeyPair + if err := kp.generate(rand); err != nil { + return nil, err + } + + var clientPub, secret [32]byte + copy(clientPub[:], kexInit.ClientPubKey) + curve25519.ScalarMult(&secret, &kp.priv, &clientPub) + if subtle.ConstantTimeCompare(secret[:], curve25519Zeros[:]) == 1 { + return nil, errors.New("ssh: peer's curve25519 public value has wrong order") + } + + hostKeyBytes := priv.PublicKey().Marshal() + + h := crypto.SHA256.New() + magics.write(h) + writeString(h, hostKeyBytes) + writeString(h, kexInit.ClientPubKey) + writeString(h, kp.pub[:]) + + ki := new(big.Int).SetBytes(secret[:]) + K := make([]byte, intLength(ki)) + marshalInt(K, ki) + h.Write(K) + + H := h.Sum(nil) + + sig, err := signAndMarshal(priv, rand, H, algo) + if err != nil { + return nil, err + } + + reply := kexECDHReplyMsg{ + EphemeralPubKey: kp.pub[:], + HostKey: hostKeyBytes, + Signature: sig, + } + if err := c.writePacket(Marshal(&reply)); err != nil { + return nil, err + } + return &kexResult{ + H: H, + K: K, + HostKey: hostKeyBytes, + Signature: sig, + Hash: crypto.SHA256, + }, nil +} + +// dhGEXSHA implements the diffie-hellman-group-exchange-sha1 and +// diffie-hellman-group-exchange-sha256 key agreement protocols, +// as described in RFC 4419 +type dhGEXSHA struct { + hashFunc crypto.Hash +} + +const ( + dhGroupExchangeMinimumBits = 2048 + dhGroupExchangePreferredBits = 2048 + dhGroupExchangeMaximumBits = 8192 +) + +func (gex *dhGEXSHA) Client(c packetConn, randSource io.Reader, magics *handshakeMagics) (*kexResult, error) { + // Send GexRequest + kexDHGexRequest := kexDHGexRequestMsg{ + MinBits: dhGroupExchangeMinimumBits, + PreferedBits: dhGroupExchangePreferredBits, + MaxBits: dhGroupExchangeMaximumBits, + } + if err := c.writePacket(Marshal(&kexDHGexRequest)); err != nil { + return nil, err + } + + // Receive GexGroup + packet, err := c.readPacket() + if err != nil { + return nil, err + } + + var msg kexDHGexGroupMsg + if err = Unmarshal(packet, &msg); err != nil { + return nil, err + } + + // reject if p's bit length < dhGroupExchangeMinimumBits or > dhGroupExchangeMaximumBits + if msg.P.BitLen() < dhGroupExchangeMinimumBits || msg.P.BitLen() > dhGroupExchangeMaximumBits { + return nil, fmt.Errorf("ssh: server-generated gex p is out of range (%d bits)", msg.P.BitLen()) + } + + // Check if g is safe by verifying that 1 < g < p-1 + pMinusOne := new(big.Int).Sub(msg.P, bigOne) + if msg.G.Cmp(bigOne) <= 0 || msg.G.Cmp(pMinusOne) >= 0 { + return nil, fmt.Errorf("ssh: server provided gex g is not safe") + } + + // Send GexInit + pHalf := new(big.Int).Rsh(msg.P, 1) + x, err := rand.Int(randSource, pHalf) + if err != nil { + return nil, err + } + X := new(big.Int).Exp(msg.G, x, msg.P) + kexDHGexInit := kexDHGexInitMsg{ + X: X, + } + if err := c.writePacket(Marshal(&kexDHGexInit)); err != nil { + return nil, err + } + + // Receive GexReply + packet, err = c.readPacket() + if err != nil { + return nil, err + } + + var kexDHGexReply kexDHGexReplyMsg + if err = Unmarshal(packet, &kexDHGexReply); err != nil { + return nil, err + } + + if kexDHGexReply.Y.Cmp(bigOne) <= 0 || kexDHGexReply.Y.Cmp(pMinusOne) >= 0 { + return nil, errors.New("ssh: DH parameter out of bounds") + } + kInt := new(big.Int).Exp(kexDHGexReply.Y, x, msg.P) + + // Check if k is safe by verifying that k > 1 and k < p - 1 + if kInt.Cmp(bigOne) <= 0 || kInt.Cmp(pMinusOne) >= 0 { + return nil, fmt.Errorf("ssh: derived k is not safe") + } + + h := gex.hashFunc.New() + magics.write(h) + writeString(h, kexDHGexReply.HostKey) + binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMinimumBits)) + binary.Write(h, binary.BigEndian, uint32(dhGroupExchangePreferredBits)) + binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMaximumBits)) + writeInt(h, msg.P) + writeInt(h, msg.G) + writeInt(h, X) + writeInt(h, kexDHGexReply.Y) + K := make([]byte, intLength(kInt)) + marshalInt(K, kInt) + h.Write(K) + + return &kexResult{ + H: h.Sum(nil), + K: K, + HostKey: kexDHGexReply.HostKey, + Signature: kexDHGexReply.Signature, + Hash: gex.hashFunc, + }, nil +} + +// Server half implementation of the Diffie Hellman Key Exchange with SHA1 and SHA256. +// +// This is a minimal implementation to satisfy the automated tests. +func (gex dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { + // Receive GexRequest + packet, err := c.readPacket() + if err != nil { + return + } + var kexDHGexRequest kexDHGexRequestMsg + if err = Unmarshal(packet, &kexDHGexRequest); err != nil { + return + } + + // Send GexGroup + // This is the group called diffie-hellman-group14-sha1 in RFC + // 4253 and Oakley Group 14 in RFC 3526. + p, _ := new(big.Int).SetString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g := big.NewInt(2) + + msg := &kexDHGexGroupMsg{ + P: p, + G: g, + } + if err := c.writePacket(Marshal(msg)); err != nil { + return nil, err + } + + // Receive GexInit + packet, err = c.readPacket() + if err != nil { + return + } + var kexDHGexInit kexDHGexInitMsg + if err = Unmarshal(packet, &kexDHGexInit); err != nil { + return + } + + pHalf := new(big.Int).Rsh(p, 1) + + y, err := rand.Int(randSource, pHalf) + if err != nil { + return + } + Y := new(big.Int).Exp(g, y, p) + + pMinusOne := new(big.Int).Sub(p, bigOne) + if kexDHGexInit.X.Cmp(bigOne) <= 0 || kexDHGexInit.X.Cmp(pMinusOne) >= 0 { + return nil, errors.New("ssh: DH parameter out of bounds") + } + kInt := new(big.Int).Exp(kexDHGexInit.X, y, p) + + hostKeyBytes := priv.PublicKey().Marshal() + + h := gex.hashFunc.New() + magics.write(h) + writeString(h, hostKeyBytes) + binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMinimumBits)) + binary.Write(h, binary.BigEndian, uint32(dhGroupExchangePreferredBits)) + binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMaximumBits)) + writeInt(h, p) + writeInt(h, g) + writeInt(h, kexDHGexInit.X) + writeInt(h, Y) + + K := make([]byte, intLength(kInt)) + marshalInt(K, kInt) + h.Write(K) + + H := h.Sum(nil) + + // H is already a hash, but the hostkey signing will apply its + // own key-specific hash algorithm. + sig, err := signAndMarshal(priv, randSource, H, algo) + if err != nil { + return nil, err + } + + kexDHGexReply := kexDHGexReplyMsg{ + HostKey: hostKeyBytes, + Y: Y, + Signature: sig, + } + packet = Marshal(&kexDHGexReply) + + err = c.writePacket(packet) + + return &kexResult{ + H: H, + K: K, + HostKey: hostKeyBytes, + Signature: sig, + Hash: gex.hashFunc, + }, err +} diff --git a/pkg/proto/ssh/keys.go b/pkg/proto/ssh/keys.go new file mode 100644 index 0000000..231b26d --- /dev/null +++ b/pkg/proto/ssh/keys.go @@ -0,0 +1,1728 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "bytes" + "crypto" + "crypto/aes" + "crypto/cipher" + "crypto/dsa" + "crypto/ecdsa" + "crypto/ed25519" + "crypto/elliptic" + "crypto/md5" + "crypto/rand" + "crypto/rsa" + "crypto/sha256" + "crypto/x509" + "encoding/asn1" + "encoding/base64" + "encoding/binary" + "encoding/hex" + "encoding/pem" + "errors" + "fmt" + "io" + "math/big" + "strings" + + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh/internal/bcrypt_pbkdf" +) + +// Public key algorithms names. These values can appear in PublicKey.Type, +// ClientConfig.HostKeyAlgorithms, Signature.Format, or as AlgorithmSigner +// arguments. +const ( + KeyAlgoRSA = "ssh-rsa" + KeyAlgoDSA = "ssh-dss" + KeyAlgoECDSA256 = "ecdsa-sha2-nistp256" + KeyAlgoSKECDSA256 = "sk-ecdsa-sha2-nistp256@openssh.com" + KeyAlgoECDSA384 = "ecdsa-sha2-nistp384" + KeyAlgoECDSA521 = "ecdsa-sha2-nistp521" + KeyAlgoED25519 = "ssh-ed25519" + KeyAlgoSKED25519 = "sk-ssh-ed25519@openssh.com" + + // KeyAlgoRSASHA256 and KeyAlgoRSASHA512 are only public key algorithms, not + // public key formats, so they can't appear as a PublicKey.Type. The + // corresponding PublicKey.Type is KeyAlgoRSA. See RFC 8332, Section 2. + KeyAlgoRSASHA256 = "rsa-sha2-256" + KeyAlgoRSASHA512 = "rsa-sha2-512" +) + +const ( + // Deprecated: use KeyAlgoRSA. + SigAlgoRSA = KeyAlgoRSA + // Deprecated: use KeyAlgoRSASHA256. + SigAlgoRSASHA2256 = KeyAlgoRSASHA256 + // Deprecated: use KeyAlgoRSASHA512. + SigAlgoRSASHA2512 = KeyAlgoRSASHA512 +) + +// parsePubKey parses a public key of the given algorithm. +// Use ParsePublicKey for keys with prepended algorithm. +func parsePubKey(in []byte, algo string) (pubKey PublicKey, rest []byte, err error) { + switch algo { + case KeyAlgoRSA: + return parseRSA(in) + case KeyAlgoDSA: + return parseDSA(in) + case KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521: + return parseECDSA(in) + case KeyAlgoSKECDSA256: + return parseSKECDSA(in) + case KeyAlgoED25519: + return parseED25519(in) + case KeyAlgoSKED25519: + return parseSKEd25519(in) + case CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoSKECDSA256v01, CertAlgoED25519v01, CertAlgoSKED25519v01: + cert, err := parseCert(in, certKeyAlgoNames[algo]) + if err != nil { + return nil, nil, err + } + return cert, nil, nil + } + return nil, nil, fmt.Errorf("ssh: unknown key algorithm: %v", algo) +} + +// parseAuthorizedKey parses a public key in OpenSSH authorized_keys format +// (see sshd(8) manual page) once the options and key type fields have been +// removed. +func parseAuthorizedKey(in []byte) (out PublicKey, comment string, err error) { + in = bytes.TrimSpace(in) + + i := bytes.IndexAny(in, " \t") + if i == -1 { + i = len(in) + } + base64Key := in[:i] + + key := make([]byte, base64.StdEncoding.DecodedLen(len(base64Key))) + n, err := base64.StdEncoding.Decode(key, base64Key) + if err != nil { + return nil, "", err + } + key = key[:n] + out, err = ParsePublicKey(key) + if err != nil { + return nil, "", err + } + comment = string(bytes.TrimSpace(in[i:])) + return out, comment, nil +} + +// ParseKnownHosts parses an entry in the format of the known_hosts file. +// +// The known_hosts format is documented in the sshd(8) manual page. This +// function will parse a single entry from in. On successful return, marker +// will contain the optional marker value (i.e. "cert-authority" or "revoked") +// or else be empty, hosts will contain the hosts that this entry matches, +// pubKey will contain the public key and comment will contain any trailing +// comment at the end of the line. See the sshd(8) manual page for the various +// forms that a host string can take. +// +// The unparsed remainder of the input will be returned in rest. This function +// can be called repeatedly to parse multiple entries. +// +// If no entries were found in the input then err will be io.EOF. Otherwise a +// non-nil err value indicates a parse error. +func ParseKnownHosts(in []byte) (marker string, hosts []string, pubKey PublicKey, comment string, rest []byte, err error) { + for len(in) > 0 { + end := bytes.IndexByte(in, '\n') + if end != -1 { + rest = in[end+1:] + in = in[:end] + } else { + rest = nil + } + + end = bytes.IndexByte(in, '\r') + if end != -1 { + in = in[:end] + } + + in = bytes.TrimSpace(in) + if len(in) == 0 || in[0] == '#' { + in = rest + continue + } + + i := bytes.IndexAny(in, " \t") + if i == -1 { + in = rest + continue + } + + // Strip out the beginning of the known_host key. + // This is either an optional marker or a (set of) hostname(s). + keyFields := bytes.Fields(in) + if len(keyFields) < 3 || len(keyFields) > 5 { + return "", nil, nil, "", nil, errors.New("ssh: invalid entry in known_hosts data") + } + + // keyFields[0] is either "@cert-authority", "@revoked" or a comma separated + // list of hosts + marker := "" + if keyFields[0][0] == '@' { + marker = string(keyFields[0][1:]) + keyFields = keyFields[1:] + } + + hosts := string(keyFields[0]) + // keyFields[1] contains the key type (e.g. “ssh-rsa”). + // However, that information is duplicated inside the + // base64-encoded key and so is ignored here. + + key := bytes.Join(keyFields[2:], []byte(" ")) + if pubKey, comment, err = parseAuthorizedKey(key); err != nil { + return "", nil, nil, "", nil, err + } + + return marker, strings.Split(hosts, ","), pubKey, comment, rest, nil + } + + return "", nil, nil, "", nil, io.EOF +} + +// ParseAuthorizedKey parses a public key from an authorized_keys +// file used in OpenSSH according to the sshd(8) manual page. +func ParseAuthorizedKey(in []byte) (out PublicKey, comment string, options []string, rest []byte, err error) { + for len(in) > 0 { + end := bytes.IndexByte(in, '\n') + if end != -1 { + rest = in[end+1:] + in = in[:end] + } else { + rest = nil + } + + end = bytes.IndexByte(in, '\r') + if end != -1 { + in = in[:end] + } + + in = bytes.TrimSpace(in) + if len(in) == 0 || in[0] == '#' { + in = rest + continue + } + + i := bytes.IndexAny(in, " \t") + if i == -1 { + in = rest + continue + } + + if out, comment, err = parseAuthorizedKey(in[i:]); err == nil { + return out, comment, options, rest, nil + } + + // No key type recognised. Maybe there's an options field at + // the beginning. + var b byte + inQuote := false + var candidateOptions []string + optionStart := 0 + for i, b = range in { + isEnd := !inQuote && (b == ' ' || b == '\t') + if (b == ',' && !inQuote) || isEnd { + if i-optionStart > 0 { + candidateOptions = append(candidateOptions, string(in[optionStart:i])) + } + optionStart = i + 1 + } + if isEnd { + break + } + if b == '"' && (i == 0 || (i > 0 && in[i-1] != '\\')) { + inQuote = !inQuote + } + } + for i < len(in) && (in[i] == ' ' || in[i] == '\t') { + i++ + } + if i == len(in) { + // Invalid line: unmatched quote + in = rest + continue + } + + in = in[i:] + i = bytes.IndexAny(in, " \t") + if i == -1 { + in = rest + continue + } + + if out, comment, err = parseAuthorizedKey(in[i:]); err == nil { + options = candidateOptions + return out, comment, options, rest, nil + } + + in = rest + continue + } + + return nil, "", nil, nil, errors.New("ssh: no key found") +} + +// ParsePublicKey parses an SSH public key formatted for use in +// the SSH wire protocol according to RFC 4253, section 6.6. +func ParsePublicKey(in []byte) (out PublicKey, err error) { + algo, in, ok := parseString(in) + if !ok { + return nil, errShortRead + } + var rest []byte + out, rest, err = parsePubKey(in, string(algo)) + if len(rest) > 0 { + return nil, errors.New("ssh: trailing junk in public key") + } + + return out, err +} + +// MarshalAuthorizedKey serializes key for inclusion in an OpenSSH +// authorized_keys file. The return value ends with newline. +func MarshalAuthorizedKey(key PublicKey) []byte { + b := &bytes.Buffer{} + b.WriteString(key.Type()) + b.WriteByte(' ') + e := base64.NewEncoder(base64.StdEncoding, b) + e.Write(key.Marshal()) + e.Close() + b.WriteByte('\n') + return b.Bytes() +} + +// MarshalPrivateKey returns a PEM block with the private key serialized in the +// OpenSSH format. +func MarshalPrivateKey(key crypto.PrivateKey, comment string) (*pem.Block, error) { + return marshalOpenSSHPrivateKey(key, comment, unencryptedOpenSSHMarshaler) +} + +// MarshalPrivateKeyWithPassphrase returns a PEM block holding the encrypted +// private key serialized in the OpenSSH format. +func MarshalPrivateKeyWithPassphrase(key crypto.PrivateKey, comment string, passphrase []byte) (*pem.Block, error) { + return marshalOpenSSHPrivateKey(key, comment, passphraseProtectedOpenSSHMarshaler(passphrase)) +} + +// PublicKey represents a public key using an unspecified algorithm. +// +// Some PublicKeys provided by this package also implement CryptoPublicKey. +type PublicKey interface { + // Type returns the key format name, e.g. "ssh-rsa". + Type() string + + // Marshal returns the serialized key data in SSH wire format, with the name + // prefix. To unmarshal the returned data, use the ParsePublicKey function. + Marshal() []byte + + // Verify that sig is a signature on the given data using this key. This + // method will hash the data appropriately first. sig.Format is allowed to + // be any signature algorithm compatible with the key type, the caller + // should check if it has more stringent requirements. + Verify(data []byte, sig *Signature) error +} + +// CryptoPublicKey, if implemented by a PublicKey, +// returns the underlying crypto.PublicKey form of the key. +type CryptoPublicKey interface { + CryptoPublicKey() crypto.PublicKey +} + +// A Signer can create signatures that verify against a public key. +// +// Some Signers provided by this package also implement MultiAlgorithmSigner. +type Signer interface { + // PublicKey returns the associated PublicKey. + PublicKey() PublicKey + + // Sign returns a signature for the given data. This method will hash the + // data appropriately first. The signature algorithm is expected to match + // the key format returned by the PublicKey.Type method (and not to be any + // alternative algorithm supported by the key format). + Sign(rand io.Reader, data []byte) (*Signature, error) +} + +// An AlgorithmSigner is a Signer that also supports specifying an algorithm to +// use for signing. +// +// An AlgorithmSigner can't advertise the algorithms it supports, unless it also +// implements MultiAlgorithmSigner, so it should be prepared to be invoked with +// every algorithm supported by the public key format. +type AlgorithmSigner interface { + Signer + + // SignWithAlgorithm is like Signer.Sign, but allows specifying a desired + // signing algorithm. Callers may pass an empty string for the algorithm in + // which case the AlgorithmSigner will use a default algorithm. This default + // doesn't currently control any behavior in this package. + SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) +} + +// MultiAlgorithmSigner is an AlgorithmSigner that also reports the algorithms +// supported by that signer. +type MultiAlgorithmSigner interface { + AlgorithmSigner + + // Algorithms returns the available algorithms in preference order. The list + // must not be empty, and it must not include certificate types. + Algorithms() []string +} + +// NewSignerWithAlgorithms returns a signer restricted to the specified +// algorithms. The algorithms must be set in preference order. The list must not +// be empty, and it must not include certificate types. An error is returned if +// the specified algorithms are incompatible with the public key type. +func NewSignerWithAlgorithms(signer AlgorithmSigner, algorithms []string) (MultiAlgorithmSigner, error) { + if len(algorithms) == 0 { + return nil, errors.New("ssh: please specify at least one valid signing algorithm") + } + var signerAlgos []string + supportedAlgos := algorithmsForKeyFormat(underlyingAlgo(signer.PublicKey().Type())) + if s, ok := signer.(*multiAlgorithmSigner); ok { + signerAlgos = s.Algorithms() + } else { + signerAlgos = supportedAlgos + } + + for _, algo := range algorithms { + if !contains(supportedAlgos, algo) { + return nil, fmt.Errorf("ssh: algorithm %q is not supported for key type %q", + algo, signer.PublicKey().Type()) + } + if !contains(signerAlgos, algo) { + return nil, fmt.Errorf("ssh: algorithm %q is restricted for the provided signer", algo) + } + } + return &multiAlgorithmSigner{ + AlgorithmSigner: signer, + supportedAlgorithms: algorithms, + }, nil +} + +type multiAlgorithmSigner struct { + AlgorithmSigner + supportedAlgorithms []string +} + +func (s *multiAlgorithmSigner) Algorithms() []string { + return s.supportedAlgorithms +} + +func (s *multiAlgorithmSigner) isAlgorithmSupported(algorithm string) bool { + if algorithm == "" { + algorithm = underlyingAlgo(s.PublicKey().Type()) + } + for _, algo := range s.supportedAlgorithms { + if algorithm == algo { + return true + } + } + return false +} + +func (s *multiAlgorithmSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { + if !s.isAlgorithmSupported(algorithm) { + return nil, fmt.Errorf("ssh: algorithm %q is not supported: %v", algorithm, s.supportedAlgorithms) + } + return s.AlgorithmSigner.SignWithAlgorithm(rand, data, algorithm) +} + +type rsaPublicKey rsa.PublicKey + +func (r *rsaPublicKey) Type() string { + return "ssh-rsa" +} + +// parseRSA parses an RSA key according to RFC 4253, section 6.6. +func parseRSA(in []byte) (out PublicKey, rest []byte, err error) { + var w struct { + E *big.Int + N *big.Int + Rest []byte `ssh:"rest"` + } + if err := Unmarshal(in, &w); err != nil { + return nil, nil, err + } + + if w.E.BitLen() > 24 { + return nil, nil, errors.New("ssh: exponent too large") + } + e := w.E.Int64() + if e < 3 || e&1 == 0 { + return nil, nil, errors.New("ssh: incorrect exponent") + } + + var key rsa.PublicKey + key.E = int(e) + key.N = w.N + return (*rsaPublicKey)(&key), w.Rest, nil +} + +func (r *rsaPublicKey) Marshal() []byte { + e := new(big.Int).SetInt64(int64(r.E)) + // RSA publickey struct layout should match the struct used by + // parseRSACert in the x/crypto/ssh/agent package. + wirekey := struct { + Name string + E *big.Int + N *big.Int + }{ + KeyAlgoRSA, + e, + r.N, + } + return Marshal(&wirekey) +} + +func (r *rsaPublicKey) Verify(data []byte, sig *Signature) error { + supportedAlgos := algorithmsForKeyFormat(r.Type()) + if !contains(supportedAlgos, sig.Format) { + return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, r.Type()) + } + hash := hashFuncs[sig.Format] + h := hash.New() + h.Write(data) + digest := h.Sum(nil) + return rsa.VerifyPKCS1v15((*rsa.PublicKey)(r), hash, digest, sig.Blob) +} + +func (r *rsaPublicKey) CryptoPublicKey() crypto.PublicKey { + return (*rsa.PublicKey)(r) +} + +type dsaPublicKey dsa.PublicKey + +func (k *dsaPublicKey) Type() string { + return "ssh-dss" +} + +func checkDSAParams(param *dsa.Parameters) error { + // SSH specifies FIPS 186-2, which only provided a single size + // (1024 bits) DSA key. FIPS 186-3 allows for larger key + // sizes, which would confuse SSH. + if l := param.P.BitLen(); l != 1024 { + return fmt.Errorf("ssh: unsupported DSA key size %d", l) + } + + return nil +} + +// parseDSA parses an DSA key according to RFC 4253, section 6.6. +func parseDSA(in []byte) (out PublicKey, rest []byte, err error) { + var w struct { + P, Q, G, Y *big.Int + Rest []byte `ssh:"rest"` + } + if err := Unmarshal(in, &w); err != nil { + return nil, nil, err + } + + param := dsa.Parameters{ + P: w.P, + Q: w.Q, + G: w.G, + } + if err := checkDSAParams(¶m); err != nil { + return nil, nil, err + } + + key := &dsaPublicKey{ + Parameters: param, + Y: w.Y, + } + return key, w.Rest, nil +} + +func (k *dsaPublicKey) Marshal() []byte { + // DSA publickey struct layout should match the struct used by + // parseDSACert in the x/crypto/ssh/agent package. + w := struct { + Name string + P, Q, G, Y *big.Int + }{ + k.Type(), + k.P, + k.Q, + k.G, + k.Y, + } + + return Marshal(&w) +} + +func (k *dsaPublicKey) Verify(data []byte, sig *Signature) error { + if sig.Format != k.Type() { + return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) + } + h := hashFuncs[sig.Format].New() + h.Write(data) + digest := h.Sum(nil) + + // Per RFC 4253, section 6.6, + // The value for 'dss_signature_blob' is encoded as a string containing + // r, followed by s (which are 160-bit integers, without lengths or + // padding, unsigned, and in network byte order). + // For DSS purposes, sig.Blob should be exactly 40 bytes in length. + if len(sig.Blob) != 40 { + return errors.New("ssh: DSA signature parse error") + } + r := new(big.Int).SetBytes(sig.Blob[:20]) + s := new(big.Int).SetBytes(sig.Blob[20:]) + if dsa.Verify((*dsa.PublicKey)(k), digest, r, s) { + return nil + } + return errors.New("ssh: signature did not verify") +} + +func (k *dsaPublicKey) CryptoPublicKey() crypto.PublicKey { + return (*dsa.PublicKey)(k) +} + +type dsaPrivateKey struct { + *dsa.PrivateKey +} + +func (k *dsaPrivateKey) PublicKey() PublicKey { + return (*dsaPublicKey)(&k.PrivateKey.PublicKey) +} + +func (k *dsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) { + return k.SignWithAlgorithm(rand, data, k.PublicKey().Type()) +} + +func (k *dsaPrivateKey) Algorithms() []string { + return []string{k.PublicKey().Type()} +} + +func (k *dsaPrivateKey) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { + if algorithm != "" && algorithm != k.PublicKey().Type() { + return nil, fmt.Errorf("ssh: unsupported signature algorithm %s", algorithm) + } + + h := hashFuncs[k.PublicKey().Type()].New() + h.Write(data) + digest := h.Sum(nil) + r, s, err := dsa.Sign(rand, k.PrivateKey, digest) + if err != nil { + return nil, err + } + + sig := make([]byte, 40) + rb := r.Bytes() + sb := s.Bytes() + + copy(sig[20-len(rb):20], rb) + copy(sig[40-len(sb):], sb) + + return &Signature{ + Format: k.PublicKey().Type(), + Blob: sig, + }, nil +} + +type ecdsaPublicKey ecdsa.PublicKey + +func (k *ecdsaPublicKey) Type() string { + return "ecdsa-sha2-" + k.nistID() +} + +func (k *ecdsaPublicKey) nistID() string { + switch k.Params().BitSize { + case 256: + return "nistp256" + case 384: + return "nistp384" + case 521: + return "nistp521" + } + panic("ssh: unsupported ecdsa key size") +} + +type ed25519PublicKey ed25519.PublicKey + +func (k ed25519PublicKey) Type() string { + return KeyAlgoED25519 +} + +func parseED25519(in []byte) (out PublicKey, rest []byte, err error) { + var w struct { + KeyBytes []byte + Rest []byte `ssh:"rest"` + } + + if err := Unmarshal(in, &w); err != nil { + return nil, nil, err + } + + if l := len(w.KeyBytes); l != ed25519.PublicKeySize { + return nil, nil, fmt.Errorf("invalid size %d for Ed25519 public key", l) + } + + return ed25519PublicKey(w.KeyBytes), w.Rest, nil +} + +func (k ed25519PublicKey) Marshal() []byte { + w := struct { + Name string + KeyBytes []byte + }{ + KeyAlgoED25519, + []byte(k), + } + return Marshal(&w) +} + +func (k ed25519PublicKey) Verify(b []byte, sig *Signature) error { + if sig.Format != k.Type() { + return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) + } + if l := len(k); l != ed25519.PublicKeySize { + return fmt.Errorf("ssh: invalid size %d for Ed25519 public key", l) + } + + if ok := ed25519.Verify(ed25519.PublicKey(k), b, sig.Blob); !ok { + return errors.New("ssh: signature did not verify") + } + + return nil +} + +func (k ed25519PublicKey) CryptoPublicKey() crypto.PublicKey { + return ed25519.PublicKey(k) +} + +func supportedEllipticCurve(curve elliptic.Curve) bool { + return curve == elliptic.P256() || curve == elliptic.P384() || curve == elliptic.P521() +} + +// parseECDSA parses an ECDSA key according to RFC 5656, section 3.1. +func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) { + var w struct { + Curve string + KeyBytes []byte + Rest []byte `ssh:"rest"` + } + + if err := Unmarshal(in, &w); err != nil { + return nil, nil, err + } + + key := new(ecdsa.PublicKey) + + switch w.Curve { + case "nistp256": + key.Curve = elliptic.P256() + case "nistp384": + key.Curve = elliptic.P384() + case "nistp521": + key.Curve = elliptic.P521() + default: + return nil, nil, errors.New("ssh: unsupported curve") + } + + key.X, key.Y = elliptic.Unmarshal(key.Curve, w.KeyBytes) + if key.X == nil || key.Y == nil { + return nil, nil, errors.New("ssh: invalid curve point") + } + return (*ecdsaPublicKey)(key), w.Rest, nil +} + +func (k *ecdsaPublicKey) Marshal() []byte { + // See RFC 5656, section 3.1. + keyBytes := elliptic.Marshal(k.Curve, k.X, k.Y) + // ECDSA publickey struct layout should match the struct used by + // parseECDSACert in the x/crypto/ssh/agent package. + w := struct { + Name string + ID string + Key []byte + }{ + k.Type(), + k.nistID(), + keyBytes, + } + + return Marshal(&w) +} + +func (k *ecdsaPublicKey) Verify(data []byte, sig *Signature) error { + if sig.Format != k.Type() { + return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) + } + + h := hashFuncs[sig.Format].New() + h.Write(data) + digest := h.Sum(nil) + + // Per RFC 5656, section 3.1.2, + // The ecdsa_signature_blob value has the following specific encoding: + // mpint r + // mpint s + var ecSig struct { + R *big.Int + S *big.Int + } + + if err := Unmarshal(sig.Blob, &ecSig); err != nil { + return err + } + + if ecdsa.Verify((*ecdsa.PublicKey)(k), digest, ecSig.R, ecSig.S) { + return nil + } + return errors.New("ssh: signature did not verify") +} + +func (k *ecdsaPublicKey) CryptoPublicKey() crypto.PublicKey { + return (*ecdsa.PublicKey)(k) +} + +// skFields holds the additional fields present in U2F/FIDO2 signatures. +// See openssh/PROTOCOL.u2f 'SSH U2F Signatures' for details. +type skFields struct { + // Flags contains U2F/FIDO2 flags such as 'user present' + Flags byte + // Counter is a monotonic signature counter which can be + // used to detect concurrent use of a private key, should + // it be extracted from hardware. + Counter uint32 +} + +type skECDSAPublicKey struct { + // application is a URL-like string, typically "ssh:" for SSH. + // see openssh/PROTOCOL.u2f for details. + application string + ecdsa.PublicKey +} + +func (k *skECDSAPublicKey) Type() string { + return KeyAlgoSKECDSA256 +} + +func (k *skECDSAPublicKey) nistID() string { + return "nistp256" +} + +func parseSKECDSA(in []byte) (out PublicKey, rest []byte, err error) { + var w struct { + Curve string + KeyBytes []byte + Application string + Rest []byte `ssh:"rest"` + } + + if err := Unmarshal(in, &w); err != nil { + return nil, nil, err + } + + key := new(skECDSAPublicKey) + key.application = w.Application + + if w.Curve != "nistp256" { + return nil, nil, errors.New("ssh: unsupported curve") + } + key.Curve = elliptic.P256() + + key.X, key.Y = elliptic.Unmarshal(key.Curve, w.KeyBytes) + if key.X == nil || key.Y == nil { + return nil, nil, errors.New("ssh: invalid curve point") + } + + return key, w.Rest, nil +} + +func (k *skECDSAPublicKey) Marshal() []byte { + // See RFC 5656, section 3.1. + keyBytes := elliptic.Marshal(k.Curve, k.X, k.Y) + w := struct { + Name string + ID string + Key []byte + Application string + }{ + k.Type(), + k.nistID(), + keyBytes, + k.application, + } + + return Marshal(&w) +} + +func (k *skECDSAPublicKey) Verify(data []byte, sig *Signature) error { + if sig.Format != k.Type() { + return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) + } + + h := hashFuncs[sig.Format].New() + h.Write([]byte(k.application)) + appDigest := h.Sum(nil) + + h.Reset() + h.Write(data) + dataDigest := h.Sum(nil) + + var ecSig struct { + R *big.Int + S *big.Int + } + if err := Unmarshal(sig.Blob, &ecSig); err != nil { + return err + } + + var skf skFields + if err := Unmarshal(sig.Rest, &skf); err != nil { + return err + } + + blob := struct { + ApplicationDigest []byte `ssh:"rest"` + Flags byte + Counter uint32 + MessageDigest []byte `ssh:"rest"` + }{ + appDigest, + skf.Flags, + skf.Counter, + dataDigest, + } + + original := Marshal(blob) + + h.Reset() + h.Write(original) + digest := h.Sum(nil) + + if ecdsa.Verify((*ecdsa.PublicKey)(&k.PublicKey), digest, ecSig.R, ecSig.S) { + return nil + } + return errors.New("ssh: signature did not verify") +} + +type skEd25519PublicKey struct { + // application is a URL-like string, typically "ssh:" for SSH. + // see openssh/PROTOCOL.u2f for details. + application string + ed25519.PublicKey +} + +func (k *skEd25519PublicKey) Type() string { + return KeyAlgoSKED25519 +} + +func parseSKEd25519(in []byte) (out PublicKey, rest []byte, err error) { + var w struct { + KeyBytes []byte + Application string + Rest []byte `ssh:"rest"` + } + + if err := Unmarshal(in, &w); err != nil { + return nil, nil, err + } + + if l := len(w.KeyBytes); l != ed25519.PublicKeySize { + return nil, nil, fmt.Errorf("invalid size %d for Ed25519 public key", l) + } + + key := new(skEd25519PublicKey) + key.application = w.Application + key.PublicKey = ed25519.PublicKey(w.KeyBytes) + + return key, w.Rest, nil +} + +func (k *skEd25519PublicKey) Marshal() []byte { + w := struct { + Name string + KeyBytes []byte + Application string + }{ + KeyAlgoSKED25519, + []byte(k.PublicKey), + k.application, + } + return Marshal(&w) +} + +func (k *skEd25519PublicKey) Verify(data []byte, sig *Signature) error { + if sig.Format != k.Type() { + return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) + } + if l := len(k.PublicKey); l != ed25519.PublicKeySize { + return fmt.Errorf("invalid size %d for Ed25519 public key", l) + } + + h := hashFuncs[sig.Format].New() + h.Write([]byte(k.application)) + appDigest := h.Sum(nil) + + h.Reset() + h.Write(data) + dataDigest := h.Sum(nil) + + var edSig struct { + Signature []byte `ssh:"rest"` + } + + if err := Unmarshal(sig.Blob, &edSig); err != nil { + return err + } + + var skf skFields + if err := Unmarshal(sig.Rest, &skf); err != nil { + return err + } + + blob := struct { + ApplicationDigest []byte `ssh:"rest"` + Flags byte + Counter uint32 + MessageDigest []byte `ssh:"rest"` + }{ + appDigest, + skf.Flags, + skf.Counter, + dataDigest, + } + + original := Marshal(blob) + + if ok := ed25519.Verify(k.PublicKey, original, edSig.Signature); !ok { + return errors.New("ssh: signature did not verify") + } + + return nil +} + +// NewSignerFromKey takes an *rsa.PrivateKey, *dsa.PrivateKey, +// *ecdsa.PrivateKey or any other crypto.Signer and returns a +// corresponding Signer instance. ECDSA keys must use P-256, P-384 or +// P-521. DSA keys must use parameter size L1024N160. +func NewSignerFromKey(key interface{}) (Signer, error) { + switch key := key.(type) { + case crypto.Signer: + return NewSignerFromSigner(key) + case *dsa.PrivateKey: + return newDSAPrivateKey(key) + default: + return nil, fmt.Errorf("ssh: unsupported key type %T", key) + } +} + +func newDSAPrivateKey(key *dsa.PrivateKey) (Signer, error) { + if err := checkDSAParams(&key.PublicKey.Parameters); err != nil { + return nil, err + } + + return &dsaPrivateKey{key}, nil +} + +type wrappedSigner struct { + signer crypto.Signer + pubKey PublicKey +} + +// NewSignerFromSigner takes any crypto.Signer implementation and +// returns a corresponding Signer interface. This can be used, for +// example, with keys kept in hardware modules. +func NewSignerFromSigner(signer crypto.Signer) (Signer, error) { + pubKey, err := NewPublicKey(signer.Public()) + if err != nil { + return nil, err + } + + return &wrappedSigner{signer, pubKey}, nil +} + +func (s *wrappedSigner) PublicKey() PublicKey { + return s.pubKey +} + +func (s *wrappedSigner) Sign(rand io.Reader, data []byte) (*Signature, error) { + return s.SignWithAlgorithm(rand, data, s.pubKey.Type()) +} + +func (s *wrappedSigner) Algorithms() []string { + return algorithmsForKeyFormat(s.pubKey.Type()) +} + +func (s *wrappedSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { + if algorithm == "" { + algorithm = s.pubKey.Type() + } + + if !contains(s.Algorithms(), algorithm) { + return nil, fmt.Errorf("ssh: unsupported signature algorithm %q for key format %q", algorithm, s.pubKey.Type()) + } + + hashFunc := hashFuncs[algorithm] + var digest []byte + if hashFunc != 0 { + h := hashFunc.New() + h.Write(data) + digest = h.Sum(nil) + } else { + digest = data + } + + signature, err := s.signer.Sign(rand, digest, hashFunc) + if err != nil { + return nil, err + } + + // crypto.Signer.Sign is expected to return an ASN.1-encoded signature + // for ECDSA and DSA, but that's not the encoding expected by SSH, so + // re-encode. + switch s.pubKey.(type) { + case *ecdsaPublicKey, *dsaPublicKey: + type asn1Signature struct { + R, S *big.Int + } + asn1Sig := new(asn1Signature) + _, err := asn1.Unmarshal(signature, asn1Sig) + if err != nil { + return nil, err + } + + switch s.pubKey.(type) { + case *ecdsaPublicKey: + signature = Marshal(asn1Sig) + + case *dsaPublicKey: + signature = make([]byte, 40) + r := asn1Sig.R.Bytes() + s := asn1Sig.S.Bytes() + copy(signature[20-len(r):20], r) + copy(signature[40-len(s):40], s) + } + } + + return &Signature{ + Format: algorithm, + Blob: signature, + }, nil +} + +// NewPublicKey takes an *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey, +// or ed25519.PublicKey returns a corresponding PublicKey instance. +// ECDSA keys must use P-256, P-384 or P-521. +func NewPublicKey(key interface{}) (PublicKey, error) { + switch key := key.(type) { + case *rsa.PublicKey: + return (*rsaPublicKey)(key), nil + case *ecdsa.PublicKey: + if !supportedEllipticCurve(key.Curve) { + return nil, errors.New("ssh: only P-256, P-384 and P-521 EC keys are supported") + } + return (*ecdsaPublicKey)(key), nil + case *dsa.PublicKey: + return (*dsaPublicKey)(key), nil + case ed25519.PublicKey: + if l := len(key); l != ed25519.PublicKeySize { + return nil, fmt.Errorf("ssh: invalid size %d for Ed25519 public key", l) + } + return ed25519PublicKey(key), nil + default: + return nil, fmt.Errorf("ssh: unsupported key type %T", key) + } +} + +// ParsePrivateKey returns a Signer from a PEM encoded private key. It supports +// the same keys as ParseRawPrivateKey. If the private key is encrypted, it +// will return a PassphraseMissingError. +func ParsePrivateKey(pemBytes []byte) (Signer, error) { + key, err := ParseRawPrivateKey(pemBytes) + if err != nil { + return nil, err + } + + return NewSignerFromKey(key) +} + +// ParsePrivateKeyWithPassphrase returns a Signer from a PEM encoded private +// key and passphrase. It supports the same keys as +// ParseRawPrivateKeyWithPassphrase. +func ParsePrivateKeyWithPassphrase(pemBytes, passphrase []byte) (Signer, error) { + key, err := ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase) + if err != nil { + return nil, err + } + + return NewSignerFromKey(key) +} + +// encryptedBlock tells whether a private key is +// encrypted by examining its Proc-Type header +// for a mention of ENCRYPTED +// according to RFC 1421 Section 4.6.1.1. +func encryptedBlock(block *pem.Block) bool { + return strings.Contains(block.Headers["Proc-Type"], "ENCRYPTED") +} + +// A PassphraseMissingError indicates that parsing this private key requires a +// passphrase. Use ParsePrivateKeyWithPassphrase. +type PassphraseMissingError struct { + // PublicKey will be set if the private key format includes an unencrypted + // public key along with the encrypted private key. + PublicKey PublicKey +} + +func (*PassphraseMissingError) Error() string { + return "ssh: this private key is passphrase protected" +} + +// ParseRawPrivateKey returns a private key from a PEM encoded private key. It supports +// RSA, DSA, ECDSA, and Ed25519 private keys in PKCS#1, PKCS#8, OpenSSL, and OpenSSH +// formats. If the private key is encrypted, it will return a PassphraseMissingError. +func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) { + block, _ := pem.Decode(pemBytes) + if block == nil { + return nil, errors.New("ssh: no key found") + } + + if encryptedBlock(block) { + return nil, &PassphraseMissingError{} + } + + switch block.Type { + case "RSA PRIVATE KEY": + return x509.ParsePKCS1PrivateKey(block.Bytes) + // RFC5208 - https://tools.ietf.org/html/rfc5208 + case "PRIVATE KEY": + return x509.ParsePKCS8PrivateKey(block.Bytes) + case "EC PRIVATE KEY": + return x509.ParseECPrivateKey(block.Bytes) + case "DSA PRIVATE KEY": + return ParseDSAPrivateKey(block.Bytes) + case "OPENSSH PRIVATE KEY": + return parseOpenSSHPrivateKey(block.Bytes, unencryptedOpenSSHKey) + default: + return nil, fmt.Errorf("ssh: unsupported key type %q", block.Type) + } +} + +// ParseRawPrivateKeyWithPassphrase returns a private key decrypted with +// passphrase from a PEM encoded private key. If the passphrase is wrong, it +// will return x509.IncorrectPasswordError. +func ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase []byte) (interface{}, error) { + block, _ := pem.Decode(pemBytes) + if block == nil { + return nil, errors.New("ssh: no key found") + } + + if block.Type == "OPENSSH PRIVATE KEY" { + return parseOpenSSHPrivateKey(block.Bytes, passphraseProtectedOpenSSHKey(passphrase)) + } + + if !encryptedBlock(block) || !x509.IsEncryptedPEMBlock(block) { + return nil, errors.New("ssh: not an encrypted key") + } + + buf, err := x509.DecryptPEMBlock(block, passphrase) + if err != nil { + if err == x509.IncorrectPasswordError { + return nil, err + } + return nil, fmt.Errorf("ssh: cannot decode encrypted private keys: %v", err) + } + + var result interface{} + + switch block.Type { + case "RSA PRIVATE KEY": + result, err = x509.ParsePKCS1PrivateKey(buf) + case "EC PRIVATE KEY": + result, err = x509.ParseECPrivateKey(buf) + case "DSA PRIVATE KEY": + result, err = ParseDSAPrivateKey(buf) + default: + err = fmt.Errorf("ssh: unsupported key type %q", block.Type) + } + // Because of deficiencies in the format, DecryptPEMBlock does not always + // detect an incorrect password. In these cases decrypted DER bytes is + // random noise. If the parsing of the key returns an asn1.StructuralError + // we return x509.IncorrectPasswordError. + if _, ok := err.(asn1.StructuralError); ok { + return nil, x509.IncorrectPasswordError + } + + return result, err +} + +// ParseDSAPrivateKey returns a DSA private key from its ASN.1 DER encoding, as +// specified by the OpenSSL DSA man page. +func ParseDSAPrivateKey(der []byte) (*dsa.PrivateKey, error) { + var k struct { + Version int + P *big.Int + Q *big.Int + G *big.Int + Pub *big.Int + Priv *big.Int + } + rest, err := asn1.Unmarshal(der, &k) + if err != nil { + return nil, errors.New("ssh: failed to parse DSA key: " + err.Error()) + } + if len(rest) > 0 { + return nil, errors.New("ssh: garbage after DSA key") + } + + return &dsa.PrivateKey{ + PublicKey: dsa.PublicKey{ + Parameters: dsa.Parameters{ + P: k.P, + Q: k.Q, + G: k.G, + }, + Y: k.Pub, + }, + X: k.Priv, + }, nil +} + +func unencryptedOpenSSHKey(cipherName, kdfName, kdfOpts string, privKeyBlock []byte) ([]byte, error) { + if kdfName != "none" || cipherName != "none" { + return nil, &PassphraseMissingError{} + } + if kdfOpts != "" { + return nil, errors.New("ssh: invalid openssh private key") + } + return privKeyBlock, nil +} + +func passphraseProtectedOpenSSHKey(passphrase []byte) openSSHDecryptFunc { + return func(cipherName, kdfName, kdfOpts string, privKeyBlock []byte) ([]byte, error) { + if kdfName == "none" || cipherName == "none" { + return nil, errors.New("ssh: key is not password protected") + } + if kdfName != "bcrypt" { + return nil, fmt.Errorf("ssh: unknown KDF %q, only supports %q", kdfName, "bcrypt") + } + + var opts struct { + Salt string + Rounds uint32 + } + if err := Unmarshal([]byte(kdfOpts), &opts); err != nil { + return nil, err + } + + k, err := bcrypt_pbkdf.Key(passphrase, []byte(opts.Salt), int(opts.Rounds), 32+16) + if err != nil { + return nil, err + } + key, iv := k[:32], k[32:] + + c, err := aes.NewCipher(key) + if err != nil { + return nil, err + } + switch cipherName { + case "aes256-ctr": + ctr := cipher.NewCTR(c, iv) + ctr.XORKeyStream(privKeyBlock, privKeyBlock) + case "aes256-cbc": + if len(privKeyBlock)%c.BlockSize() != 0 { + return nil, fmt.Errorf("ssh: invalid encrypted private key length, not a multiple of the block size") + } + cbc := cipher.NewCBCDecrypter(c, iv) + cbc.CryptBlocks(privKeyBlock, privKeyBlock) + default: + return nil, fmt.Errorf("ssh: unknown cipher %q, only supports %q or %q", cipherName, "aes256-ctr", "aes256-cbc") + } + + return privKeyBlock, nil + } +} + +func unencryptedOpenSSHMarshaler(privKeyBlock []byte) ([]byte, string, string, string, error) { + key := generateOpenSSHPadding(privKeyBlock, 8) + return key, "none", "none", "", nil +} + +func passphraseProtectedOpenSSHMarshaler(passphrase []byte) openSSHEncryptFunc { + return func(privKeyBlock []byte) ([]byte, string, string, string, error) { + salt := make([]byte, 16) + if _, err := rand.Read(salt); err != nil { + return nil, "", "", "", err + } + + opts := struct { + Salt []byte + Rounds uint32 + }{salt, 16} + + // Derive key to encrypt the private key block. + k, err := bcrypt_pbkdf.Key(passphrase, salt, int(opts.Rounds), 32+aes.BlockSize) + if err != nil { + return nil, "", "", "", err + } + + // Add padding matching the block size of AES. + keyBlock := generateOpenSSHPadding(privKeyBlock, aes.BlockSize) + + // Encrypt the private key using the derived secret. + + dst := make([]byte, len(keyBlock)) + key, iv := k[:32], k[32:] + block, err := aes.NewCipher(key) + if err != nil { + return nil, "", "", "", err + } + + stream := cipher.NewCTR(block, iv) + stream.XORKeyStream(dst, keyBlock) + + return dst, "aes256-ctr", "bcrypt", string(Marshal(opts)), nil + } +} + +const privateKeyAuthMagic = "openssh-key-v1\x00" + +type openSSHDecryptFunc func(CipherName, KdfName, KdfOpts string, PrivKeyBlock []byte) ([]byte, error) +type openSSHEncryptFunc func(PrivKeyBlock []byte) (ProtectedKeyBlock []byte, cipherName, kdfName, kdfOptions string, err error) + +type openSSHEncryptedPrivateKey struct { + CipherName string + KdfName string + KdfOpts string + NumKeys uint32 + PubKey []byte + PrivKeyBlock []byte +} + +type openSSHPrivateKey struct { + Check1 uint32 + Check2 uint32 + Keytype string + Rest []byte `ssh:"rest"` +} + +type openSSHRSAPrivateKey struct { + N *big.Int + E *big.Int + D *big.Int + Iqmp *big.Int + P *big.Int + Q *big.Int + Comment string + Pad []byte `ssh:"rest"` +} + +type openSSHEd25519PrivateKey struct { + Pub []byte + Priv []byte + Comment string + Pad []byte `ssh:"rest"` +} + +type openSSHECDSAPrivateKey struct { + Curve string + Pub []byte + D *big.Int + Comment string + Pad []byte `ssh:"rest"` +} + +// parseOpenSSHPrivateKey parses an OpenSSH private key, using the decrypt +// function to unwrap the encrypted portion. unencryptedOpenSSHKey can be used +// as the decrypt function to parse an unencrypted private key. See +// https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key. +func parseOpenSSHPrivateKey(key []byte, decrypt openSSHDecryptFunc) (crypto.PrivateKey, error) { + if len(key) < len(privateKeyAuthMagic) || string(key[:len(privateKeyAuthMagic)]) != privateKeyAuthMagic { + return nil, errors.New("ssh: invalid openssh private key format") + } + remaining := key[len(privateKeyAuthMagic):] + + var w openSSHEncryptedPrivateKey + if err := Unmarshal(remaining, &w); err != nil { + return nil, err + } + if w.NumKeys != 1 { + // We only support single key files, and so does OpenSSH. + // https://github.com/openssh/openssh-portable/blob/4103a3ec7/sshkey.c#L4171 + return nil, errors.New("ssh: multi-key files are not supported") + } + + privKeyBlock, err := decrypt(w.CipherName, w.KdfName, w.KdfOpts, w.PrivKeyBlock) + if err != nil { + if err, ok := err.(*PassphraseMissingError); ok { + pub, errPub := ParsePublicKey(w.PubKey) + if errPub != nil { + return nil, fmt.Errorf("ssh: failed to parse embedded public key: %v", errPub) + } + err.PublicKey = pub + } + return nil, err + } + + var pk1 openSSHPrivateKey + if err := Unmarshal(privKeyBlock, &pk1); err != nil || pk1.Check1 != pk1.Check2 { + if w.CipherName != "none" { + return nil, x509.IncorrectPasswordError + } + return nil, errors.New("ssh: malformed OpenSSH key") + } + + switch pk1.Keytype { + case KeyAlgoRSA: + var key openSSHRSAPrivateKey + if err := Unmarshal(pk1.Rest, &key); err != nil { + return nil, err + } + + if err := checkOpenSSHKeyPadding(key.Pad); err != nil { + return nil, err + } + + pk := &rsa.PrivateKey{ + PublicKey: rsa.PublicKey{ + N: key.N, + E: int(key.E.Int64()), + }, + D: key.D, + Primes: []*big.Int{key.P, key.Q}, + } + + if err := pk.Validate(); err != nil { + return nil, err + } + + pk.Precompute() + + return pk, nil + case KeyAlgoED25519: + var key openSSHEd25519PrivateKey + if err := Unmarshal(pk1.Rest, &key); err != nil { + return nil, err + } + + if len(key.Priv) != ed25519.PrivateKeySize { + return nil, errors.New("ssh: private key unexpected length") + } + + if err := checkOpenSSHKeyPadding(key.Pad); err != nil { + return nil, err + } + + pk := ed25519.PrivateKey(make([]byte, ed25519.PrivateKeySize)) + copy(pk, key.Priv) + return &pk, nil + case KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521: + var key openSSHECDSAPrivateKey + if err := Unmarshal(pk1.Rest, &key); err != nil { + return nil, err + } + + if err := checkOpenSSHKeyPadding(key.Pad); err != nil { + return nil, err + } + + var curve elliptic.Curve + switch key.Curve { + case "nistp256": + curve = elliptic.P256() + case "nistp384": + curve = elliptic.P384() + case "nistp521": + curve = elliptic.P521() + default: + return nil, errors.New("ssh: unhandled elliptic curve: " + key.Curve) + } + + X, Y := elliptic.Unmarshal(curve, key.Pub) + if X == nil || Y == nil { + return nil, errors.New("ssh: failed to unmarshal public key") + } + + if key.D.Cmp(curve.Params().N) >= 0 { + return nil, errors.New("ssh: scalar is out of range") + } + + x, y := curve.ScalarBaseMult(key.D.Bytes()) + if x.Cmp(X) != 0 || y.Cmp(Y) != 0 { + return nil, errors.New("ssh: public key does not match private key") + } + + return &ecdsa.PrivateKey{ + PublicKey: ecdsa.PublicKey{ + Curve: curve, + X: X, + Y: Y, + }, + D: key.D, + }, nil + default: + return nil, errors.New("ssh: unhandled key type") + } +} + +func marshalOpenSSHPrivateKey(key crypto.PrivateKey, comment string, encrypt openSSHEncryptFunc) (*pem.Block, error) { + var w openSSHEncryptedPrivateKey + var pk1 openSSHPrivateKey + + // Random check bytes. + var check uint32 + if err := binary.Read(rand.Reader, binary.BigEndian, &check); err != nil { + return nil, err + } + + pk1.Check1 = check + pk1.Check2 = check + w.NumKeys = 1 + + // Use a []byte directly on ed25519 keys. + if k, ok := key.(*ed25519.PrivateKey); ok { + key = *k + } + + switch k := key.(type) { + case *rsa.PrivateKey: + E := new(big.Int).SetInt64(int64(k.PublicKey.E)) + // Marshal public key: + // E and N are in reversed order in the public and private key. + pubKey := struct { + KeyType string + E *big.Int + N *big.Int + }{ + KeyAlgoRSA, + E, k.PublicKey.N, + } + w.PubKey = Marshal(pubKey) + + // Marshal private key. + key := openSSHRSAPrivateKey{ + N: k.PublicKey.N, + E: E, + D: k.D, + Iqmp: k.Precomputed.Qinv, + P: k.Primes[0], + Q: k.Primes[1], + Comment: comment, + } + pk1.Keytype = KeyAlgoRSA + pk1.Rest = Marshal(key) + case ed25519.PrivateKey: + pub := make([]byte, ed25519.PublicKeySize) + priv := make([]byte, ed25519.PrivateKeySize) + copy(pub, k[32:]) + copy(priv, k) + + // Marshal public key. + pubKey := struct { + KeyType string + Pub []byte + }{ + KeyAlgoED25519, pub, + } + w.PubKey = Marshal(pubKey) + + // Marshal private key. + key := openSSHEd25519PrivateKey{ + Pub: pub, + Priv: priv, + Comment: comment, + } + pk1.Keytype = KeyAlgoED25519 + pk1.Rest = Marshal(key) + case *ecdsa.PrivateKey: + var curve, keyType string + switch name := k.Curve.Params().Name; name { + case "P-256": + curve = "nistp256" + keyType = KeyAlgoECDSA256 + case "P-384": + curve = "nistp384" + keyType = KeyAlgoECDSA384 + case "P-521": + curve = "nistp521" + keyType = KeyAlgoECDSA521 + default: + return nil, errors.New("ssh: unhandled elliptic curve " + name) + } + + pub := elliptic.Marshal(k.Curve, k.PublicKey.X, k.PublicKey.Y) + + // Marshal public key. + pubKey := struct { + KeyType string + Curve string + Pub []byte + }{ + keyType, curve, pub, + } + w.PubKey = Marshal(pubKey) + + // Marshal private key. + key := openSSHECDSAPrivateKey{ + Curve: curve, + Pub: pub, + D: k.D, + Comment: comment, + } + pk1.Keytype = keyType + pk1.Rest = Marshal(key) + default: + return nil, fmt.Errorf("ssh: unsupported key type %T", k) + } + + var err error + // Add padding and encrypt the key if necessary. + w.PrivKeyBlock, w.CipherName, w.KdfName, w.KdfOpts, err = encrypt(Marshal(pk1)) + if err != nil { + return nil, err + } + + b := Marshal(w) + block := &pem.Block{ + Type: "OPENSSH PRIVATE KEY", + Bytes: append([]byte(privateKeyAuthMagic), b...), + } + return block, nil +} + +func checkOpenSSHKeyPadding(pad []byte) error { + for i, b := range pad { + if int(b) != i+1 { + return errors.New("ssh: padding not as expected") + } + } + return nil +} + +func generateOpenSSHPadding(block []byte, blockSize int) []byte { + for i, l := 0, len(block); (l+i)%blockSize != 0; i++ { + block = append(block, byte(i+1)) + } + return block +} + +// FingerprintLegacyMD5 returns the user presentation of the key's +// fingerprint as described by RFC 4716 section 4. +func FingerprintLegacyMD5(pubKey PublicKey) string { + md5sum := md5.Sum(pubKey.Marshal()) + hexarray := make([]string, len(md5sum)) + for i, c := range md5sum { + hexarray[i] = hex.EncodeToString([]byte{c}) + } + return strings.Join(hexarray, ":") +} + +// FingerprintSHA256 returns the user presentation of the key's +// fingerprint as unpadded base64 encoded sha256 hash. +// This format was introduced from OpenSSH 6.8. +// https://www.openssh.com/txt/release-6.8 +// https://tools.ietf.org/html/rfc4648#section-3.2 (unpadded base64 encoding) +func FingerprintSHA256(pubKey PublicKey) string { + sha256sum := sha256.Sum256(pubKey.Marshal()) + hash := base64.RawStdEncoding.EncodeToString(sha256sum[:]) + return "SHA256:" + hash +} diff --git a/pkg/proto/ssh/knownhosts/knownhosts.go b/pkg/proto/ssh/knownhosts/knownhosts.go new file mode 100644 index 0000000..267b9e6 --- /dev/null +++ b/pkg/proto/ssh/knownhosts/knownhosts.go @@ -0,0 +1,540 @@ +// Copyright 2017 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package knownhosts implements a parser for the OpenSSH known_hosts +// host key database, and provides utility functions for writing +// OpenSSH compliant known_hosts files. +package knownhosts + +import ( + "bufio" + "bytes" + "crypto/hmac" + "crypto/rand" + "crypto/sha1" + "encoding/base64" + "errors" + "fmt" + "io" + "net" + "os" + "strings" + + "github.com/Neur0toxine/sshpoke/pkg/proto/ssh" +) + +// See the sshd manpage +// (http://man.openbsd.org/sshd#SSH_KNOWN_HOSTS_FILE_FORMAT) for +// background. + +type addr struct{ host, port string } + +func (a *addr) String() string { + h := a.host + if strings.Contains(h, ":") { + h = "[" + h + "]" + } + return h + ":" + a.port +} + +type matcher interface { + match(addr) bool +} + +type hostPattern struct { + negate bool + addr addr +} + +func (p *hostPattern) String() string { + n := "" + if p.negate { + n = "!" + } + + return n + p.addr.String() +} + +type hostPatterns []hostPattern + +func (ps hostPatterns) match(a addr) bool { + matched := false + for _, p := range ps { + if !p.match(a) { + continue + } + if p.negate { + return false + } + matched = true + } + return matched +} + +// See +// https://android.googlesource.com/platform/external/openssh/+/ab28f5495c85297e7a597c1ba62e996416da7c7e/addrmatch.c +// The matching of * has no regard for separators, unlike filesystem globs +func wildcardMatch(pat []byte, str []byte) bool { + for { + if len(pat) == 0 { + return len(str) == 0 + } + if len(str) == 0 { + return false + } + + if pat[0] == '*' { + if len(pat) == 1 { + return true + } + + for j := range str { + if wildcardMatch(pat[1:], str[j:]) { + return true + } + } + return false + } + + if pat[0] == '?' || pat[0] == str[0] { + pat = pat[1:] + str = str[1:] + } else { + return false + } + } +} + +func (p *hostPattern) match(a addr) bool { + return wildcardMatch([]byte(p.addr.host), []byte(a.host)) && p.addr.port == a.port +} + +type keyDBLine struct { + cert bool + matcher matcher + knownKey KnownKey +} + +func serialize(k ssh.PublicKey) string { + return k.Type() + " " + base64.StdEncoding.EncodeToString(k.Marshal()) +} + +func (l *keyDBLine) match(a addr) bool { + return l.matcher.match(a) +} + +type hostKeyDB struct { + // Serialized version of revoked keys + revoked map[string]*KnownKey + lines []keyDBLine +} + +func newHostKeyDB() *hostKeyDB { + db := &hostKeyDB{ + revoked: make(map[string]*KnownKey), + } + + return db +} + +func keyEq(a, b ssh.PublicKey) bool { + return bytes.Equal(a.Marshal(), b.Marshal()) +} + +// IsHostAuthority can be used as a callback in ssh.CertChecker +func (db *hostKeyDB) IsHostAuthority(remote ssh.PublicKey, address string) bool { + h, p, err := net.SplitHostPort(address) + if err != nil { + return false + } + a := addr{host: h, port: p} + + for _, l := range db.lines { + if l.cert && keyEq(l.knownKey.Key, remote) && l.match(a) { + return true + } + } + return false +} + +// IsRevoked can be used as a callback in ssh.CertChecker +func (db *hostKeyDB) IsRevoked(key *ssh.Certificate) bool { + _, ok := db.revoked[string(key.Marshal())] + return ok +} + +const markerCert = "@cert-authority" +const markerRevoked = "@revoked" + +func nextWord(line []byte) (string, []byte) { + i := bytes.IndexAny(line, "\t ") + if i == -1 { + return string(line), nil + } + + return string(line[:i]), bytes.TrimSpace(line[i:]) +} + +func parseLine(line []byte) (marker, host string, key ssh.PublicKey, err error) { + if w, next := nextWord(line); w == markerCert || w == markerRevoked { + marker = w + line = next + } + + host, line = nextWord(line) + if len(line) == 0 { + return "", "", nil, errors.New("knownhosts: missing host pattern") + } + + // ignore the keytype as it's in the key blob anyway. + _, line = nextWord(line) + if len(line) == 0 { + return "", "", nil, errors.New("knownhosts: missing key type pattern") + } + + keyBlob, _ := nextWord(line) + + keyBytes, err := base64.StdEncoding.DecodeString(keyBlob) + if err != nil { + return "", "", nil, err + } + key, err = ssh.ParsePublicKey(keyBytes) + if err != nil { + return "", "", nil, err + } + + return marker, host, key, nil +} + +func (db *hostKeyDB) parseLine(line []byte, filename string, linenum int) error { + marker, pattern, key, err := parseLine(line) + if err != nil { + return err + } + + if marker == markerRevoked { + db.revoked[string(key.Marshal())] = &KnownKey{ + Key: key, + Filename: filename, + Line: linenum, + } + + return nil + } + + entry := keyDBLine{ + cert: marker == markerCert, + knownKey: KnownKey{ + Filename: filename, + Line: linenum, + Key: key, + }, + } + + if pattern[0] == '|' { + entry.matcher, err = newHashedHost(pattern) + } else { + entry.matcher, err = newHostnameMatcher(pattern) + } + + if err != nil { + return err + } + + db.lines = append(db.lines, entry) + return nil +} + +func newHostnameMatcher(pattern string) (matcher, error) { + var hps hostPatterns + for _, p := range strings.Split(pattern, ",") { + if len(p) == 0 { + continue + } + + var a addr + var negate bool + if p[0] == '!' { + negate = true + p = p[1:] + } + + if len(p) == 0 { + return nil, errors.New("knownhosts: negation without following hostname") + } + + var err error + if p[0] == '[' { + a.host, a.port, err = net.SplitHostPort(p) + if err != nil { + return nil, err + } + } else { + a.host, a.port, err = net.SplitHostPort(p) + if err != nil { + a.host = p + a.port = "22" + } + } + hps = append(hps, hostPattern{ + negate: negate, + addr: a, + }) + } + return hps, nil +} + +// KnownKey represents a key declared in a known_hosts file. +type KnownKey struct { + Key ssh.PublicKey + Filename string + Line int +} + +func (k *KnownKey) String() string { + return fmt.Sprintf("%s:%d: %s", k.Filename, k.Line, serialize(k.Key)) +} + +// KeyError is returned if we did not find the key in the host key +// database, or there was a mismatch. Typically, in batch +// applications, this should be interpreted as failure. Interactive +// applications can offer an interactive prompt to the user. +type KeyError struct { + // Want holds the accepted host keys. For each key algorithm, + // there can be one hostkey. If Want is empty, the host is + // unknown. If Want is non-empty, there was a mismatch, which + // can signify a MITM attack. + Want []KnownKey +} + +func (u *KeyError) Error() string { + if len(u.Want) == 0 { + return "knownhosts: key is unknown" + } + return "knownhosts: key mismatch" +} + +// RevokedError is returned if we found a key that was revoked. +type RevokedError struct { + Revoked KnownKey +} + +func (r *RevokedError) Error() string { + return "knownhosts: key is revoked" +} + +// check checks a key against the host database. This should not be +// used for verifying certificates. +func (db *hostKeyDB) check(address string, remote net.Addr, remoteKey ssh.PublicKey) error { + if revoked := db.revoked[string(remoteKey.Marshal())]; revoked != nil { + return &RevokedError{Revoked: *revoked} + } + + host, port, err := net.SplitHostPort(remote.String()) + if err != nil { + return fmt.Errorf("knownhosts: SplitHostPort(%s): %v", remote, err) + } + + hostToCheck := addr{host, port} + if address != "" { + // Give preference to the hostname if available. + host, port, err := net.SplitHostPort(address) + if err != nil { + return fmt.Errorf("knownhosts: SplitHostPort(%s): %v", address, err) + } + + hostToCheck = addr{host, port} + } + + return db.checkAddr(hostToCheck, remoteKey) +} + +// checkAddr checks if we can find the given public key for the +// given address. If we only find an entry for the IP address, +// or only the hostname, then this still succeeds. +func (db *hostKeyDB) checkAddr(a addr, remoteKey ssh.PublicKey) error { + // TODO(hanwen): are these the right semantics? What if there + // is just a key for the IP address, but not for the + // hostname? + + // Algorithm => key. + knownKeys := map[string]KnownKey{} + for _, l := range db.lines { + if l.match(a) { + typ := l.knownKey.Key.Type() + if _, ok := knownKeys[typ]; !ok { + knownKeys[typ] = l.knownKey + } + } + } + + keyErr := &KeyError{} + for _, v := range knownKeys { + keyErr.Want = append(keyErr.Want, v) + } + + // Unknown remote host. + if len(knownKeys) == 0 { + return keyErr + } + + // If the remote host starts using a different, unknown key type, we + // also interpret that as a mismatch. + if known, ok := knownKeys[remoteKey.Type()]; !ok || !keyEq(known.Key, remoteKey) { + return keyErr + } + + return nil +} + +// The Read function parses file contents. +func (db *hostKeyDB) Read(r io.Reader, filename string) error { + scanner := bufio.NewScanner(r) + + lineNum := 0 + for scanner.Scan() { + lineNum++ + line := scanner.Bytes() + line = bytes.TrimSpace(line) + if len(line) == 0 || line[0] == '#' { + continue + } + + if err := db.parseLine(line, filename, lineNum); err != nil { + return fmt.Errorf("knownhosts: %s:%d: %v", filename, lineNum, err) + } + } + return scanner.Err() +} + +// New creates a host key callback from the given OpenSSH host key +// files. The returned callback is for use in +// ssh.ClientConfig.HostKeyCallback. By preference, the key check +// operates on the hostname if available, i.e. if a server changes its +// IP address, the host key check will still succeed, even though a +// record of the new IP address is not available. +func New(files ...string) (ssh.HostKeyCallback, error) { + db := newHostKeyDB() + for _, fn := range files { + f, err := os.Open(fn) + if err != nil { + return nil, err + } + defer f.Close() + if err := db.Read(f, fn); err != nil { + return nil, err + } + } + + var certChecker ssh.CertChecker + certChecker.IsHostAuthority = db.IsHostAuthority + certChecker.IsRevoked = db.IsRevoked + certChecker.HostKeyFallback = db.check + + return certChecker.CheckHostKey, nil +} + +// Normalize normalizes an address into the form used in known_hosts +func Normalize(address string) string { + host, port, err := net.SplitHostPort(address) + if err != nil { + host = address + port = "22" + } + entry := host + if port != "22" { + entry = "[" + entry + "]:" + port + } else if strings.Contains(host, ":") && !strings.HasPrefix(host, "[") { + entry = "[" + entry + "]" + } + return entry +} + +// Line returns a line to add append to the known_hosts files. +func Line(addresses []string, key ssh.PublicKey) string { + var trimmed []string + for _, a := range addresses { + trimmed = append(trimmed, Normalize(a)) + } + + return strings.Join(trimmed, ",") + " " + serialize(key) +} + +// HashHostname hashes the given hostname. The hostname is not +// normalized before hashing. +func HashHostname(hostname string) string { + // TODO(hanwen): check if we can safely normalize this always. + salt := make([]byte, sha1.Size) + + _, err := rand.Read(salt) + if err != nil { + panic(fmt.Sprintf("crypto/rand failure %v", err)) + } + + hash := hashHost(hostname, salt) + return encodeHash(sha1HashType, salt, hash) +} + +func decodeHash(encoded string) (hashType string, salt, hash []byte, err error) { + if len(encoded) == 0 || encoded[0] != '|' { + err = errors.New("knownhosts: hashed host must start with '|'") + return + } + components := strings.Split(encoded, "|") + if len(components) != 4 { + err = fmt.Errorf("knownhosts: got %d components, want 3", len(components)) + return + } + + hashType = components[1] + if salt, err = base64.StdEncoding.DecodeString(components[2]); err != nil { + return + } + if hash, err = base64.StdEncoding.DecodeString(components[3]); err != nil { + return + } + return +} + +func encodeHash(typ string, salt []byte, hash []byte) string { + return strings.Join([]string{"", + typ, + base64.StdEncoding.EncodeToString(salt), + base64.StdEncoding.EncodeToString(hash), + }, "|") +} + +// See https://android.googlesource.com/platform/external/openssh/+/ab28f5495c85297e7a597c1ba62e996416da7c7e/hostfile.c#120 +func hashHost(hostname string, salt []byte) []byte { + mac := hmac.New(sha1.New, salt) + mac.Write([]byte(hostname)) + return mac.Sum(nil) +} + +type hashedHost struct { + salt []byte + hash []byte +} + +const sha1HashType = "1" + +func newHashedHost(encoded string) (*hashedHost, error) { + typ, salt, hash, err := decodeHash(encoded) + if err != nil { + return nil, err + } + + // The type field seems for future algorithm agility, but it's + // actually hardcoded in openssh currently, see + // https://android.googlesource.com/platform/external/openssh/+/ab28f5495c85297e7a597c1ba62e996416da7c7e/hostfile.c#120 + if typ != sha1HashType { + return nil, fmt.Errorf("knownhosts: got hash type %s, must be '1'", typ) + } + + return &hashedHost{salt: salt, hash: hash}, nil +} + +func (h *hashedHost) match(a addr) bool { + return bytes.Equal(hashHost(Normalize(a.String()), h.salt), h.hash) +} diff --git a/pkg/proto/ssh/mac.go b/pkg/proto/ssh/mac.go new file mode 100644 index 0000000..06a1b27 --- /dev/null +++ b/pkg/proto/ssh/mac.go @@ -0,0 +1,68 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +// Message authentication support + +import ( + "crypto/hmac" + "crypto/sha1" + "crypto/sha256" + "crypto/sha512" + "hash" +) + +type macMode struct { + keySize int + etm bool + new func(key []byte) hash.Hash +} + +// truncatingMAC wraps around a hash.Hash and truncates the output digest to +// a given size. +type truncatingMAC struct { + length int + hmac hash.Hash +} + +func (t truncatingMAC) Write(data []byte) (int, error) { + return t.hmac.Write(data) +} + +func (t truncatingMAC) Sum(in []byte) []byte { + out := t.hmac.Sum(in) + return out[:len(in)+t.length] +} + +func (t truncatingMAC) Reset() { + t.hmac.Reset() +} + +func (t truncatingMAC) Size() int { + return t.length +} + +func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() } + +var macModes = map[string]*macMode{ + "hmac-sha2-512-etm@openssh.com": {64, true, func(key []byte) hash.Hash { + return hmac.New(sha512.New, key) + }}, + "hmac-sha2-256-etm@openssh.com": {32, true, func(key []byte) hash.Hash { + return hmac.New(sha256.New, key) + }}, + "hmac-sha2-512": {64, false, func(key []byte) hash.Hash { + return hmac.New(sha512.New, key) + }}, + "hmac-sha2-256": {32, false, func(key []byte) hash.Hash { + return hmac.New(sha256.New, key) + }}, + "hmac-sha1": {20, false, func(key []byte) hash.Hash { + return hmac.New(sha1.New, key) + }}, + "hmac-sha1-96": {20, false, func(key []byte) hash.Hash { + return truncatingMAC{12, hmac.New(sha1.New, key)} + }}, +} diff --git a/pkg/proto/ssh/messages.go b/pkg/proto/ssh/messages.go new file mode 100644 index 0000000..b55f860 --- /dev/null +++ b/pkg/proto/ssh/messages.go @@ -0,0 +1,891 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "bytes" + "encoding/binary" + "errors" + "fmt" + "io" + "math/big" + "reflect" + "strconv" + "strings" +) + +// These are SSH message type numbers. They are scattered around several +// documents but many were taken from [SSH-PARAMETERS]. +const ( + msgIgnore = 2 + msgUnimplemented = 3 + msgDebug = 4 + msgNewKeys = 21 +) + +// SSH messages: +// +// These structures mirror the wire format of the corresponding SSH messages. +// They are marshaled using reflection with the marshal and unmarshal functions +// in this file. The only wrinkle is that a final member of type []byte with a +// ssh tag of "rest" receives the remainder of a packet when unmarshaling. + +// See RFC 4253, section 11.1. +const msgDisconnect = 1 + +// disconnectMsg is the message that signals a disconnect. It is also +// the error type returned from mux.Wait() +type disconnectMsg struct { + Reason uint32 `sshtype:"1"` + Message string + Language string +} + +func (d *disconnectMsg) Error() string { + return fmt.Sprintf("ssh: disconnect, reason %d: %s", d.Reason, d.Message) +} + +// See RFC 4253, section 7.1. +const msgKexInit = 20 + +type kexInitMsg struct { + Cookie [16]byte `sshtype:"20"` + KexAlgos []string + ServerHostKeyAlgos []string + CiphersClientServer []string + CiphersServerClient []string + MACsClientServer []string + MACsServerClient []string + CompressionClientServer []string + CompressionServerClient []string + LanguagesClientServer []string + LanguagesServerClient []string + FirstKexFollows bool + Reserved uint32 +} + +// See RFC 4253, section 8. + +// Diffie-Hellman +const msgKexDHInit = 30 + +type kexDHInitMsg struct { + X *big.Int `sshtype:"30"` +} + +const msgKexECDHInit = 30 + +type kexECDHInitMsg struct { + ClientPubKey []byte `sshtype:"30"` +} + +const msgKexECDHReply = 31 + +type kexECDHReplyMsg struct { + HostKey []byte `sshtype:"31"` + EphemeralPubKey []byte + Signature []byte +} + +const msgKexDHReply = 31 + +type kexDHReplyMsg struct { + HostKey []byte `sshtype:"31"` + Y *big.Int + Signature []byte +} + +// See RFC 4419, section 5. +const msgKexDHGexGroup = 31 + +type kexDHGexGroupMsg struct { + P *big.Int `sshtype:"31"` + G *big.Int +} + +const msgKexDHGexInit = 32 + +type kexDHGexInitMsg struct { + X *big.Int `sshtype:"32"` +} + +const msgKexDHGexReply = 33 + +type kexDHGexReplyMsg struct { + HostKey []byte `sshtype:"33"` + Y *big.Int + Signature []byte +} + +const msgKexDHGexRequest = 34 + +type kexDHGexRequestMsg struct { + MinBits uint32 `sshtype:"34"` + PreferedBits uint32 + MaxBits uint32 +} + +// See RFC 4253, section 10. +const msgServiceRequest = 5 + +type serviceRequestMsg struct { + Service string `sshtype:"5"` +} + +// See RFC 4253, section 10. +const msgServiceAccept = 6 + +type serviceAcceptMsg struct { + Service string `sshtype:"6"` +} + +// See RFC 8308, section 2.3 +const msgExtInfo = 7 + +type extInfoMsg struct { + NumExtensions uint32 `sshtype:"7"` + Payload []byte `ssh:"rest"` +} + +// See RFC 4252, section 5. +const msgUserAuthRequest = 50 + +type userAuthRequestMsg struct { + User string `sshtype:"50"` + Service string + Method string + Payload []byte `ssh:"rest"` +} + +// Used for debug printouts of packets. +type userAuthSuccessMsg struct { +} + +// See RFC 4252, section 5.1 +const msgUserAuthFailure = 51 + +type userAuthFailureMsg struct { + Methods []string `sshtype:"51"` + PartialSuccess bool +} + +// See RFC 4252, section 5.1 +const msgUserAuthSuccess = 52 + +// See RFC 4252, section 5.4 +const msgUserAuthBanner = 53 + +type userAuthBannerMsg struct { + Message string `sshtype:"53"` + // unused, but required to allow message parsing + Language string +} + +// See RFC 4256, section 3.2 +const msgUserAuthInfoRequest = 60 +const msgUserAuthInfoResponse = 61 + +type userAuthInfoRequestMsg struct { + Name string `sshtype:"60"` + Instruction string + Language string + NumPrompts uint32 + Prompts []byte `ssh:"rest"` +} + +// See RFC 4254, section 5.1. +const msgChannelOpen = 90 + +type channelOpenMsg struct { + ChanType string `sshtype:"90"` + PeersID uint32 + PeersWindow uint32 + MaxPacketSize uint32 + TypeSpecificData []byte `ssh:"rest"` +} + +const msgChannelExtendedData = 95 +const msgChannelData = 94 + +// Used for debug print outs of packets. +type channelDataMsg struct { + PeersID uint32 `sshtype:"94"` + Length uint32 + Rest []byte `ssh:"rest"` +} + +// See RFC 4254, section 5.1. +const msgChannelOpenConfirm = 91 + +type channelOpenConfirmMsg struct { + PeersID uint32 `sshtype:"91"` + MyID uint32 + MyWindow uint32 + MaxPacketSize uint32 + TypeSpecificData []byte `ssh:"rest"` +} + +// See RFC 4254, section 5.1. +const msgChannelOpenFailure = 92 + +type channelOpenFailureMsg struct { + PeersID uint32 `sshtype:"92"` + Reason RejectionReason + Message string + Language string +} + +const msgChannelRequest = 98 + +type channelRequestMsg struct { + PeersID uint32 `sshtype:"98"` + Request string + WantReply bool + RequestSpecificData []byte `ssh:"rest"` +} + +// See RFC 4254, section 5.4. +const msgChannelSuccess = 99 + +type channelRequestSuccessMsg struct { + PeersID uint32 `sshtype:"99"` +} + +// See RFC 4254, section 5.4. +const msgChannelFailure = 100 + +type channelRequestFailureMsg struct { + PeersID uint32 `sshtype:"100"` +} + +// See RFC 4254, section 5.3 +const msgChannelClose = 97 + +type channelCloseMsg struct { + PeersID uint32 `sshtype:"97"` +} + +// See RFC 4254, section 5.3 +const msgChannelEOF = 96 + +type channelEOFMsg struct { + PeersID uint32 `sshtype:"96"` +} + +// See RFC 4254, section 4 +const msgGlobalRequest = 80 + +type globalRequestMsg struct { + Type string `sshtype:"80"` + WantReply bool + Data []byte `ssh:"rest"` +} + +// See RFC 4254, section 4 +const msgRequestSuccess = 81 + +type globalRequestSuccessMsg struct { + Data []byte `ssh:"rest" sshtype:"81"` +} + +// See RFC 4254, section 4 +const msgRequestFailure = 82 + +type globalRequestFailureMsg struct { + Data []byte `ssh:"rest" sshtype:"82"` +} + +// See RFC 4254, section 5.2 +const msgChannelWindowAdjust = 93 + +type windowAdjustMsg struct { + PeersID uint32 `sshtype:"93"` + AdditionalBytes uint32 +} + +// See RFC 4252, section 7 +const msgUserAuthPubKeyOk = 60 + +type userAuthPubKeyOkMsg struct { + Algo string `sshtype:"60"` + PubKey []byte +} + +// See RFC 4462, section 3 +const msgUserAuthGSSAPIResponse = 60 + +type userAuthGSSAPIResponse struct { + SupportMech []byte `sshtype:"60"` +} + +const msgUserAuthGSSAPIToken = 61 + +type userAuthGSSAPIToken struct { + Token []byte `sshtype:"61"` +} + +const msgUserAuthGSSAPIMIC = 66 + +type userAuthGSSAPIMIC struct { + MIC []byte `sshtype:"66"` +} + +// See RFC 4462, section 3.9 +const msgUserAuthGSSAPIErrTok = 64 + +type userAuthGSSAPIErrTok struct { + ErrorToken []byte `sshtype:"64"` +} + +// See RFC 4462, section 3.8 +const msgUserAuthGSSAPIError = 65 + +type userAuthGSSAPIError struct { + MajorStatus uint32 `sshtype:"65"` + MinorStatus uint32 + Message string + LanguageTag string +} + +// Transport layer OpenSSH extension. See [PROTOCOL], section 1.9 +const msgPing = 192 + +type pingMsg struct { + Data string `sshtype:"192"` +} + +// Transport layer OpenSSH extension. See [PROTOCOL], section 1.9 +const msgPong = 193 + +type pongMsg struct { + Data string `sshtype:"193"` +} + +// typeTags returns the possible type bytes for the given reflect.Type, which +// should be a struct. The possible values are separated by a '|' character. +func typeTags(structType reflect.Type) (tags []byte) { + tagStr := structType.Field(0).Tag.Get("sshtype") + + for _, tag := range strings.Split(tagStr, "|") { + i, err := strconv.Atoi(tag) + if err == nil { + tags = append(tags, byte(i)) + } + } + + return tags +} + +func fieldError(t reflect.Type, field int, problem string) error { + if problem != "" { + problem = ": " + problem + } + return fmt.Errorf("ssh: unmarshal error for field %s of type %s%s", t.Field(field).Name, t.Name(), problem) +} + +var errShortRead = errors.New("ssh: short read") + +// Unmarshal parses data in SSH wire format into a structure. The out +// argument should be a pointer to struct. If the first member of the +// struct has the "sshtype" tag set to a '|'-separated set of numbers +// in decimal, the packet must start with one of those numbers. In +// case of error, Unmarshal returns a ParseError or +// UnexpectedMessageError. +func Unmarshal(data []byte, out interface{}) error { + v := reflect.ValueOf(out).Elem() + structType := v.Type() + expectedTypes := typeTags(structType) + + var expectedType byte + if len(expectedTypes) > 0 { + expectedType = expectedTypes[0] + } + + if len(data) == 0 { + return parseError(expectedType) + } + + if len(expectedTypes) > 0 { + goodType := false + for _, e := range expectedTypes { + if e > 0 && data[0] == e { + goodType = true + break + } + } + if !goodType { + return fmt.Errorf("ssh: unexpected message type %d (expected one of %v)", data[0], expectedTypes) + } + data = data[1:] + } + + var ok bool + for i := 0; i < v.NumField(); i++ { + field := v.Field(i) + t := field.Type() + switch t.Kind() { + case reflect.Bool: + if len(data) < 1 { + return errShortRead + } + field.SetBool(data[0] != 0) + data = data[1:] + case reflect.Array: + if t.Elem().Kind() != reflect.Uint8 { + return fieldError(structType, i, "array of unsupported type") + } + if len(data) < t.Len() { + return errShortRead + } + for j, n := 0, t.Len(); j < n; j++ { + field.Index(j).Set(reflect.ValueOf(data[j])) + } + data = data[t.Len():] + case reflect.Uint64: + var u64 uint64 + if u64, data, ok = parseUint64(data); !ok { + return errShortRead + } + field.SetUint(u64) + case reflect.Uint32: + var u32 uint32 + if u32, data, ok = parseUint32(data); !ok { + return errShortRead + } + field.SetUint(uint64(u32)) + case reflect.Uint8: + if len(data) < 1 { + return errShortRead + } + field.SetUint(uint64(data[0])) + data = data[1:] + case reflect.String: + var s []byte + if s, data, ok = parseString(data); !ok { + return fieldError(structType, i, "") + } + field.SetString(string(s)) + case reflect.Slice: + switch t.Elem().Kind() { + case reflect.Uint8: + if structType.Field(i).Tag.Get("ssh") == "rest" { + field.Set(reflect.ValueOf(data)) + data = nil + } else { + var s []byte + if s, data, ok = parseString(data); !ok { + return errShortRead + } + field.Set(reflect.ValueOf(s)) + } + case reflect.String: + var nl []string + if nl, data, ok = parseNameList(data); !ok { + return errShortRead + } + field.Set(reflect.ValueOf(nl)) + default: + return fieldError(structType, i, "slice of unsupported type") + } + case reflect.Ptr: + if t == bigIntType { + var n *big.Int + if n, data, ok = parseInt(data); !ok { + return errShortRead + } + field.Set(reflect.ValueOf(n)) + } else { + return fieldError(structType, i, "pointer to unsupported type") + } + default: + return fieldError(structType, i, fmt.Sprintf("unsupported type: %v", t)) + } + } + + if len(data) != 0 { + return parseError(expectedType) + } + + return nil +} + +// Marshal serializes the message in msg to SSH wire format. The msg +// argument should be a struct or pointer to struct. If the first +// member has the "sshtype" tag set to a number in decimal, that +// number is prepended to the result. If the last of member has the +// "ssh" tag set to "rest", its contents are appended to the output. +func Marshal(msg interface{}) []byte { + out := make([]byte, 0, 64) + return marshalStruct(out, msg) +} + +func marshalStruct(out []byte, msg interface{}) []byte { + v := reflect.Indirect(reflect.ValueOf(msg)) + msgTypes := typeTags(v.Type()) + if len(msgTypes) > 0 { + out = append(out, msgTypes[0]) + } + + for i, n := 0, v.NumField(); i < n; i++ { + field := v.Field(i) + switch t := field.Type(); t.Kind() { + case reflect.Bool: + var v uint8 + if field.Bool() { + v = 1 + } + out = append(out, v) + case reflect.Array: + if t.Elem().Kind() != reflect.Uint8 { + panic(fmt.Sprintf("array of non-uint8 in field %d: %T", i, field.Interface())) + } + for j, l := 0, t.Len(); j < l; j++ { + out = append(out, uint8(field.Index(j).Uint())) + } + case reflect.Uint32: + out = appendU32(out, uint32(field.Uint())) + case reflect.Uint64: + out = appendU64(out, uint64(field.Uint())) + case reflect.Uint8: + out = append(out, uint8(field.Uint())) + case reflect.String: + s := field.String() + out = appendInt(out, len(s)) + out = append(out, s...) + case reflect.Slice: + switch t.Elem().Kind() { + case reflect.Uint8: + if v.Type().Field(i).Tag.Get("ssh") != "rest" { + out = appendInt(out, field.Len()) + } + out = append(out, field.Bytes()...) + case reflect.String: + offset := len(out) + out = appendU32(out, 0) + if n := field.Len(); n > 0 { + for j := 0; j < n; j++ { + f := field.Index(j) + if j != 0 { + out = append(out, ',') + } + out = append(out, f.String()...) + } + // overwrite length value + binary.BigEndian.PutUint32(out[offset:], uint32(len(out)-offset-4)) + } + default: + panic(fmt.Sprintf("slice of unknown type in field %d: %T", i, field.Interface())) + } + case reflect.Ptr: + if t == bigIntType { + var n *big.Int + nValue := reflect.ValueOf(&n) + nValue.Elem().Set(field) + needed := intLength(n) + oldLength := len(out) + + if cap(out)-len(out) < needed { + newOut := make([]byte, len(out), 2*(len(out)+needed)) + copy(newOut, out) + out = newOut + } + out = out[:oldLength+needed] + marshalInt(out[oldLength:], n) + } else { + panic(fmt.Sprintf("pointer to unknown type in field %d: %T", i, field.Interface())) + } + } + } + + return out +} + +var bigOne = big.NewInt(1) + +func parseString(in []byte) (out, rest []byte, ok bool) { + if len(in) < 4 { + return + } + length := binary.BigEndian.Uint32(in) + in = in[4:] + if uint32(len(in)) < length { + return + } + out = in[:length] + rest = in[length:] + ok = true + return +} + +var ( + comma = []byte{','} + emptyNameList = []string{} +) + +func parseNameList(in []byte) (out []string, rest []byte, ok bool) { + contents, rest, ok := parseString(in) + if !ok { + return + } + if len(contents) == 0 { + out = emptyNameList + return + } + parts := bytes.Split(contents, comma) + out = make([]string, len(parts)) + for i, part := range parts { + out[i] = string(part) + } + return +} + +func parseInt(in []byte) (out *big.Int, rest []byte, ok bool) { + contents, rest, ok := parseString(in) + if !ok { + return + } + out = new(big.Int) + + if len(contents) > 0 && contents[0]&0x80 == 0x80 { + // This is a negative number + notBytes := make([]byte, len(contents)) + for i := range notBytes { + notBytes[i] = ^contents[i] + } + out.SetBytes(notBytes) + out.Add(out, bigOne) + out.Neg(out) + } else { + // Positive number + out.SetBytes(contents) + } + ok = true + return +} + +func parseUint32(in []byte) (uint32, []byte, bool) { + if len(in) < 4 { + return 0, nil, false + } + return binary.BigEndian.Uint32(in), in[4:], true +} + +func parseUint64(in []byte) (uint64, []byte, bool) { + if len(in) < 8 { + return 0, nil, false + } + return binary.BigEndian.Uint64(in), in[8:], true +} + +func intLength(n *big.Int) int { + length := 4 /* length bytes */ + if n.Sign() < 0 { + nMinus1 := new(big.Int).Neg(n) + nMinus1.Sub(nMinus1, bigOne) + bitLen := nMinus1.BitLen() + if bitLen%8 == 0 { + // The number will need 0xff padding + length++ + } + length += (bitLen + 7) / 8 + } else if n.Sign() == 0 { + // A zero is the zero length string + } else { + bitLen := n.BitLen() + if bitLen%8 == 0 { + // The number will need 0x00 padding + length++ + } + length += (bitLen + 7) / 8 + } + + return length +} + +func marshalUint32(to []byte, n uint32) []byte { + binary.BigEndian.PutUint32(to, n) + return to[4:] +} + +func marshalUint64(to []byte, n uint64) []byte { + binary.BigEndian.PutUint64(to, n) + return to[8:] +} + +func marshalInt(to []byte, n *big.Int) []byte { + lengthBytes := to + to = to[4:] + length := 0 + + if n.Sign() < 0 { + // A negative number has to be converted to two's-complement + // form. So we'll subtract 1 and invert. If the + // most-significant-bit isn't set then we'll need to pad the + // beginning with 0xff in order to keep the number negative. + nMinus1 := new(big.Int).Neg(n) + nMinus1.Sub(nMinus1, bigOne) + bytes := nMinus1.Bytes() + for i := range bytes { + bytes[i] ^= 0xff + } + if len(bytes) == 0 || bytes[0]&0x80 == 0 { + to[0] = 0xff + to = to[1:] + length++ + } + nBytes := copy(to, bytes) + to = to[nBytes:] + length += nBytes + } else if n.Sign() == 0 { + // A zero is the zero length string + } else { + bytes := n.Bytes() + if len(bytes) > 0 && bytes[0]&0x80 != 0 { + // We'll have to pad this with a 0x00 in order to + // stop it looking like a negative number. + to[0] = 0 + to = to[1:] + length++ + } + nBytes := copy(to, bytes) + to = to[nBytes:] + length += nBytes + } + + lengthBytes[0] = byte(length >> 24) + lengthBytes[1] = byte(length >> 16) + lengthBytes[2] = byte(length >> 8) + lengthBytes[3] = byte(length) + return to +} + +func writeInt(w io.Writer, n *big.Int) { + length := intLength(n) + buf := make([]byte, length) + marshalInt(buf, n) + w.Write(buf) +} + +func writeString(w io.Writer, s []byte) { + var lengthBytes [4]byte + lengthBytes[0] = byte(len(s) >> 24) + lengthBytes[1] = byte(len(s) >> 16) + lengthBytes[2] = byte(len(s) >> 8) + lengthBytes[3] = byte(len(s)) + w.Write(lengthBytes[:]) + w.Write(s) +} + +func stringLength(n int) int { + return 4 + n +} + +func marshalString(to []byte, s []byte) []byte { + to[0] = byte(len(s) >> 24) + to[1] = byte(len(s) >> 16) + to[2] = byte(len(s) >> 8) + to[3] = byte(len(s)) + to = to[4:] + copy(to, s) + return to[len(s):] +} + +var bigIntType = reflect.TypeOf((*big.Int)(nil)) + +// Decode a packet into its corresponding message. +func decode(packet []byte) (interface{}, error) { + var msg interface{} + switch packet[0] { + case msgDisconnect: + msg = new(disconnectMsg) + case msgServiceRequest: + msg = new(serviceRequestMsg) + case msgServiceAccept: + msg = new(serviceAcceptMsg) + case msgExtInfo: + msg = new(extInfoMsg) + case msgKexInit: + msg = new(kexInitMsg) + case msgKexDHInit: + msg = new(kexDHInitMsg) + case msgKexDHReply: + msg = new(kexDHReplyMsg) + case msgUserAuthRequest: + msg = new(userAuthRequestMsg) + case msgUserAuthSuccess: + return new(userAuthSuccessMsg), nil + case msgUserAuthFailure: + msg = new(userAuthFailureMsg) + case msgUserAuthPubKeyOk: + msg = new(userAuthPubKeyOkMsg) + case msgGlobalRequest: + msg = new(globalRequestMsg) + case msgRequestSuccess: + msg = new(globalRequestSuccessMsg) + case msgRequestFailure: + msg = new(globalRequestFailureMsg) + case msgChannelOpen: + msg = new(channelOpenMsg) + case msgChannelData: + msg = new(channelDataMsg) + case msgChannelOpenConfirm: + msg = new(channelOpenConfirmMsg) + case msgChannelOpenFailure: + msg = new(channelOpenFailureMsg) + case msgChannelWindowAdjust: + msg = new(windowAdjustMsg) + case msgChannelEOF: + msg = new(channelEOFMsg) + case msgChannelClose: + msg = new(channelCloseMsg) + case msgChannelRequest: + msg = new(channelRequestMsg) + case msgChannelSuccess: + msg = new(channelRequestSuccessMsg) + case msgChannelFailure: + msg = new(channelRequestFailureMsg) + case msgUserAuthGSSAPIToken: + msg = new(userAuthGSSAPIToken) + case msgUserAuthGSSAPIMIC: + msg = new(userAuthGSSAPIMIC) + case msgUserAuthGSSAPIErrTok: + msg = new(userAuthGSSAPIErrTok) + case msgUserAuthGSSAPIError: + msg = new(userAuthGSSAPIError) + default: + return nil, unexpectedMessageError(0, packet[0]) + } + if err := Unmarshal(packet, msg); err != nil { + return nil, err + } + return msg, nil +} + +var packetTypeNames = map[byte]string{ + msgDisconnect: "disconnectMsg", + msgServiceRequest: "serviceRequestMsg", + msgServiceAccept: "serviceAcceptMsg", + msgExtInfo: "extInfoMsg", + msgKexInit: "kexInitMsg", + msgKexDHInit: "kexDHInitMsg", + msgKexDHReply: "kexDHReplyMsg", + msgUserAuthRequest: "userAuthRequestMsg", + msgUserAuthSuccess: "userAuthSuccessMsg", + msgUserAuthFailure: "userAuthFailureMsg", + msgUserAuthPubKeyOk: "userAuthPubKeyOkMsg", + msgGlobalRequest: "globalRequestMsg", + msgRequestSuccess: "globalRequestSuccessMsg", + msgRequestFailure: "globalRequestFailureMsg", + msgChannelOpen: "channelOpenMsg", + msgChannelData: "channelDataMsg", + msgChannelOpenConfirm: "channelOpenConfirmMsg", + msgChannelOpenFailure: "channelOpenFailureMsg", + msgChannelWindowAdjust: "windowAdjustMsg", + msgChannelEOF: "channelEOFMsg", + msgChannelClose: "channelCloseMsg", + msgChannelRequest: "channelRequestMsg", + msgChannelSuccess: "channelRequestSuccessMsg", + msgChannelFailure: "channelRequestFailureMsg", +} diff --git a/pkg/proto/ssh/mux.go b/pkg/proto/ssh/mux.go new file mode 100644 index 0000000..d2d24c6 --- /dev/null +++ b/pkg/proto/ssh/mux.go @@ -0,0 +1,357 @@ +// Copyright 2013 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "encoding/binary" + "fmt" + "io" + "log" + "sync" + "sync/atomic" +) + +// debugMux, if set, causes messages in the connection protocol to be +// logged. +const debugMux = false + +// chanList is a thread safe channel list. +type chanList struct { + // protects concurrent access to chans + sync.Mutex + + // chans are indexed by the local id of the channel, which the + // other side should send in the PeersId field. + chans []*channel + + // This is a debugging aid: it offsets all IDs by this + // amount. This helps distinguish otherwise identical + // server/client muxes + offset uint32 +} + +// Assigns a channel ID to the given channel. +func (c *chanList) add(ch *channel) uint32 { + c.Lock() + defer c.Unlock() + for i := range c.chans { + if c.chans[i] == nil { + c.chans[i] = ch + return uint32(i) + c.offset + } + } + c.chans = append(c.chans, ch) + return uint32(len(c.chans)-1) + c.offset +} + +// getChan returns the channel for the given ID. +func (c *chanList) getChan(id uint32) *channel { + id -= c.offset + + c.Lock() + defer c.Unlock() + if id < uint32(len(c.chans)) { + return c.chans[id] + } + return nil +} + +func (c *chanList) remove(id uint32) { + id -= c.offset + c.Lock() + if id < uint32(len(c.chans)) { + c.chans[id] = nil + } + c.Unlock() +} + +// dropAll forgets all channels it knows, returning them in a slice. +func (c *chanList) dropAll() []*channel { + c.Lock() + defer c.Unlock() + var r []*channel + + for _, ch := range c.chans { + if ch == nil { + continue + } + r = append(r, ch) + } + c.chans = nil + return r +} + +// mux represents the state for the SSH connection protocol, which +// multiplexes many channels onto a single packet transport. +type mux struct { + conn packetConn + chanList chanList + + incomingChannels chan NewChannel + + globalSentMu sync.Mutex + globalResponses chan interface{} + incomingRequests chan *Request + + errCond *sync.Cond + err error +} + +// When debugging, each new chanList instantiation has a different +// offset. +var globalOff uint32 + +func (m *mux) Wait() error { + m.errCond.L.Lock() + defer m.errCond.L.Unlock() + for m.err == nil { + m.errCond.Wait() + } + return m.err +} + +// newMux returns a mux that runs over the given connection. +func newMux(p packetConn) *mux { + m := &mux{ + conn: p, + incomingChannels: make(chan NewChannel, chanSize), + globalResponses: make(chan interface{}, 1), + incomingRequests: make(chan *Request, chanSize), + errCond: newCond(), + } + if debugMux { + m.chanList.offset = atomic.AddUint32(&globalOff, 1) + } + + go m.loop() + return m +} + +func (m *mux) sendMessage(msg interface{}) error { + p := Marshal(msg) + if debugMux { + log.Printf("send global(%d): %#v", m.chanList.offset, msg) + } + return m.conn.writePacket(p) +} + +func (m *mux) SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error) { + if wantReply { + m.globalSentMu.Lock() + defer m.globalSentMu.Unlock() + } + + if err := m.sendMessage(globalRequestMsg{ + Type: name, + WantReply: wantReply, + Data: payload, + }); err != nil { + return false, nil, err + } + + if !wantReply { + return false, nil, nil + } + + msg, ok := <-m.globalResponses + if !ok { + return false, nil, io.EOF + } + switch msg := msg.(type) { + case *globalRequestFailureMsg: + return false, msg.Data, nil + case *globalRequestSuccessMsg: + return true, msg.Data, nil + default: + return false, nil, fmt.Errorf("ssh: unexpected response to request: %#v", msg) + } +} + +// ackRequest must be called after processing a global request that +// has WantReply set. +func (m *mux) ackRequest(ok bool, data []byte) error { + if ok { + return m.sendMessage(globalRequestSuccessMsg{Data: data}) + } + return m.sendMessage(globalRequestFailureMsg{Data: data}) +} + +func (m *mux) Close() error { + return m.conn.Close() +} + +// loop runs the connection machine. It will process packets until an +// error is encountered. To synchronize on loop exit, use mux.Wait. +func (m *mux) loop() { + var err error + for err == nil { + err = m.onePacket() + } + + for _, ch := range m.chanList.dropAll() { + ch.close() + } + + close(m.incomingChannels) + close(m.incomingRequests) + close(m.globalResponses) + + m.conn.Close() + + m.errCond.L.Lock() + m.err = err + m.errCond.Broadcast() + m.errCond.L.Unlock() + + if debugMux { + log.Println("loop exit", err) + } +} + +// onePacket reads and processes one packet. +func (m *mux) onePacket() error { + packet, err := m.conn.readPacket() + if err != nil { + return err + } + + if debugMux { + if packet[0] == msgChannelData || packet[0] == msgChannelExtendedData { + log.Printf("decoding(%d): data packet - %d bytes", m.chanList.offset, len(packet)) + } else { + p, _ := decode(packet) + log.Printf("decoding(%d): %d %#v - %d bytes", m.chanList.offset, packet[0], p, len(packet)) + } + } + + switch packet[0] { + case msgChannelOpen: + return m.handleChannelOpen(packet) + case msgGlobalRequest, msgRequestSuccess, msgRequestFailure: + return m.handleGlobalPacket(packet) + case msgPing: + var msg pingMsg + if err := Unmarshal(packet, &msg); err != nil { + return fmt.Errorf("failed to unmarshal ping@openssh.com message: %w", err) + } + return m.sendMessage(pongMsg(msg)) + } + + // assume a channel packet. + if len(packet) < 5 { + return parseError(packet[0]) + } + id := binary.BigEndian.Uint32(packet[1:]) + ch := m.chanList.getChan(id) + if ch == nil { + return m.handleUnknownChannelPacket(id, packet) + } + + return ch.handlePacket(packet) +} + +func (m *mux) handleGlobalPacket(packet []byte) error { + msg, err := decode(packet) + if err != nil { + return err + } + + switch msg := msg.(type) { + case *globalRequestMsg: + m.incomingRequests <- &Request{ + Type: msg.Type, + WantReply: msg.WantReply, + Payload: msg.Data, + mux: m, + } + case *globalRequestSuccessMsg, *globalRequestFailureMsg: + m.globalResponses <- msg + default: + panic(fmt.Sprintf("not a global message %#v", msg)) + } + + return nil +} + +// handleChannelOpen schedules a channel to be Accept()ed. +func (m *mux) handleChannelOpen(packet []byte) error { + var msg channelOpenMsg + if err := Unmarshal(packet, &msg); err != nil { + return err + } + + if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 { + failMsg := channelOpenFailureMsg{ + PeersID: msg.PeersID, + Reason: ConnectionFailed, + Message: "invalid request", + Language: "en_US.UTF-8", + } + return m.sendMessage(failMsg) + } + + c := m.newChannel(msg.ChanType, channelInbound, msg.TypeSpecificData) + c.remoteId = msg.PeersID + c.maxRemotePayload = msg.MaxPacketSize + c.remoteWin.add(msg.PeersWindow) + m.incomingChannels <- c + return nil +} + +func (m *mux) OpenChannel(chanType string, extra []byte) (Channel, <-chan *Request, error) { + ch, err := m.openChannel(chanType, extra) + if err != nil { + return nil, nil, err + } + + return ch, ch.incomingRequests, nil +} + +func (m *mux) openChannel(chanType string, extra []byte) (*channel, error) { + ch := m.newChannel(chanType, channelOutbound, extra) + + ch.maxIncomingPayload = channelMaxPacket + + open := channelOpenMsg{ + ChanType: chanType, + PeersWindow: ch.myWindow, + MaxPacketSize: ch.maxIncomingPayload, + TypeSpecificData: extra, + PeersID: ch.localId, + } + if err := m.sendMessage(open); err != nil { + return nil, err + } + + switch msg := (<-ch.msg).(type) { + case *channelOpenConfirmMsg: + return ch, nil + case *channelOpenFailureMsg: + return nil, &OpenChannelError{msg.Reason, msg.Message} + default: + return nil, fmt.Errorf("ssh: unexpected packet in response to channel open: %T", msg) + } +} + +func (m *mux) handleUnknownChannelPacket(id uint32, packet []byte) error { + msg, err := decode(packet) + if err != nil { + return err + } + + switch msg := msg.(type) { + // RFC 4254 section 5.4 says unrecognized channel requests should + // receive a failure response. + case *channelRequestMsg: + if msg.WantReply { + return m.sendMessage(channelRequestFailureMsg{ + PeersID: msg.PeersID, + }) + } + return nil + default: + return fmt.Errorf("ssh: invalid channel %d", id) + } +} diff --git a/pkg/proto/ssh/server.go b/pkg/proto/ssh/server.go new file mode 100644 index 0000000..7f0c236 --- /dev/null +++ b/pkg/proto/ssh/server.go @@ -0,0 +1,800 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "bytes" + "errors" + "fmt" + "io" + "net" + "strings" +) + +// The Permissions type holds fine-grained permissions that are +// specific to a user or a specific authentication method for a user. +// The Permissions value for a successful authentication attempt is +// available in ServerConn, so it can be used to pass information from +// the user-authentication phase to the application layer. +type Permissions struct { + // CriticalOptions indicate restrictions to the default + // permissions, and are typically used in conjunction with + // user certificates. The standard for SSH certificates + // defines "force-command" (only allow the given command to + // execute) and "source-address" (only allow connections from + // the given address). The SSH package currently only enforces + // the "source-address" critical option. It is up to server + // implementations to enforce other critical options, such as + // "force-command", by checking them after the SSH handshake + // is successful. In general, SSH servers should reject + // connections that specify critical options that are unknown + // or not supported. + CriticalOptions map[string]string + + // Extensions are extra functionality that the server may + // offer on authenticated connections. Lack of support for an + // extension does not preclude authenticating a user. Common + // extensions are "permit-agent-forwarding", + // "permit-X11-forwarding". The Go SSH library currently does + // not act on any extension, and it is up to server + // implementations to honor them. Extensions can be used to + // pass data from the authentication callbacks to the server + // application layer. + Extensions map[string]string +} + +type GSSAPIWithMICConfig struct { + // AllowLogin, must be set, is called when gssapi-with-mic + // authentication is selected (RFC 4462 section 3). The srcName is from the + // results of the GSS-API authentication. The format is username@DOMAIN. + // GSSAPI just guarantees to the server who the user is, but not if they can log in, and with what permissions. + // This callback is called after the user identity is established with GSSAPI to decide if the user can login with + // which permissions. If the user is allowed to login, it should return a nil error. + AllowLogin func(conn ConnMetadata, srcName string) (*Permissions, error) + + // Server must be set. It's the implementation + // of the GSSAPIServer interface. See GSSAPIServer interface for details. + Server GSSAPIServer +} + +// ServerConfig holds server specific configuration data. +type ServerConfig struct { + // Config contains configuration shared between client and server. + Config + + // PublicKeyAuthAlgorithms specifies the supported client public key + // authentication algorithms. Note that this should not include certificate + // types since those use the underlying algorithm. This list is sent to the + // client if it supports the server-sig-algs extension. Order is irrelevant. + // If unspecified then a default set of algorithms is used. + PublicKeyAuthAlgorithms []string + + hostKeys []Signer + + // NoClientAuth is true if clients are allowed to connect without + // authenticating. + // To determine NoClientAuth at runtime, set NoClientAuth to true + // and the optional NoClientAuthCallback to a non-nil value. + NoClientAuth bool + + // NoClientAuthCallback, if non-nil, is called when a user + // attempts to authenticate with auth method "none". + // NoClientAuth must also be set to true for this be used, or + // this func is unused. + NoClientAuthCallback func(ConnMetadata) (*Permissions, error) + + // MaxAuthTries specifies the maximum number of authentication attempts + // permitted per connection. If set to a negative number, the number of + // attempts are unlimited. If set to zero, the number of attempts are limited + // to 6. + MaxAuthTries int + + // PasswordCallback, if non-nil, is called when a user + // attempts to authenticate using a password. + PasswordCallback func(conn ConnMetadata, password []byte) (*Permissions, error) + + // PublicKeyCallback, if non-nil, is called when a client + // offers a public key for authentication. It must return a nil error + // if the given public key can be used to authenticate the + // given user. For example, see CertChecker.Authenticate. A + // call to this function does not guarantee that the key + // offered is in fact used to authenticate. To record any data + // depending on the public key, store it inside a + // Permissions.Extensions entry. + PublicKeyCallback func(conn ConnMetadata, key PublicKey) (*Permissions, error) + + // KeyboardInteractiveCallback, if non-nil, is called when + // keyboard-interactive authentication is selected (RFC + // 4256). The client object's Challenge function should be + // used to query the user. The callback may offer multiple + // Challenge rounds. To avoid information leaks, the client + // should be presented a challenge even if the user is + // unknown. + KeyboardInteractiveCallback func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error) + + // AuthLogCallback, if non-nil, is called to log all authentication + // attempts. + AuthLogCallback func(conn ConnMetadata, method string, err error) + + // ServerVersion is the version identification string to announce in + // the public handshake. + // If empty, a reasonable default is used. + // Note that RFC 4253 section 4.2 requires that this string start with + // "SSH-2.0-". + ServerVersion string + + // BannerCallback, if present, is called and the return string is sent to + // the client after key exchange completed but before authentication. + BannerCallback func(conn ConnMetadata) string + + // GSSAPIWithMICConfig includes gssapi server and callback, which if both non-nil, is used + // when gssapi-with-mic authentication is selected (RFC 4462 section 3). + GSSAPIWithMICConfig *GSSAPIWithMICConfig +} + +// AddHostKey adds a private key as a host key. If an existing host +// key exists with the same public key format, it is replaced. Each server +// config must have at least one host key. +func (s *ServerConfig) AddHostKey(key Signer) { + for i, k := range s.hostKeys { + if k.PublicKey().Type() == key.PublicKey().Type() { + s.hostKeys[i] = key + return + } + } + + s.hostKeys = append(s.hostKeys, key) +} + +// cachedPubKey contains the results of querying whether a public key is +// acceptable for a user. +type cachedPubKey struct { + user string + pubKeyData []byte + result error + perms *Permissions +} + +const maxCachedPubKeys = 16 + +// pubKeyCache caches tests for public keys. Since SSH clients +// will query whether a public key is acceptable before attempting to +// authenticate with it, we end up with duplicate queries for public +// key validity. The cache only applies to a single ServerConn. +type pubKeyCache struct { + keys []cachedPubKey +} + +// get returns the result for a given user/algo/key tuple. +func (c *pubKeyCache) get(user string, pubKeyData []byte) (cachedPubKey, bool) { + for _, k := range c.keys { + if k.user == user && bytes.Equal(k.pubKeyData, pubKeyData) { + return k, true + } + } + return cachedPubKey{}, false +} + +// add adds the given tuple to the cache. +func (c *pubKeyCache) add(candidate cachedPubKey) { + if len(c.keys) < maxCachedPubKeys { + c.keys = append(c.keys, candidate) + } +} + +// ServerConn is an authenticated SSH connection, as seen from the +// server +type ServerConn struct { + Conn + + // If the succeeding authentication callback returned a + // non-nil Permissions pointer, it is stored here. + Permissions *Permissions +} + +// NewServerConn starts a new SSH server with c as the underlying +// transport. It starts with a handshake and, if the handshake is +// unsuccessful, it closes the connection and returns an error. The +// Request and NewChannel channels must be serviced, or the connection +// will hang. +// +// The returned error may be of type *ServerAuthError for +// authentication errors. +func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewChannel, <-chan *Request, error) { + fullConf := *config + fullConf.SetDefaults() + if fullConf.MaxAuthTries == 0 { + fullConf.MaxAuthTries = 6 + } + if len(fullConf.PublicKeyAuthAlgorithms) == 0 { + fullConf.PublicKeyAuthAlgorithms = supportedPubKeyAuthAlgos + } else { + for _, algo := range fullConf.PublicKeyAuthAlgorithms { + if !contains(supportedPubKeyAuthAlgos, algo) { + return nil, nil, nil, fmt.Errorf("ssh: unsupported public key authentication algorithm %s", algo) + } + } + } + // Check if the config contains any unsupported key exchanges + for _, kex := range fullConf.KeyExchanges { + if _, ok := serverForbiddenKexAlgos[kex]; ok { + return nil, nil, nil, fmt.Errorf("ssh: unsupported key exchange %s for server", kex) + } + } + + s := &connection{ + sshConn: sshConn{conn: c}, + } + perms, err := s.serverHandshake(&fullConf) + if err != nil { + c.Close() + return nil, nil, nil, err + } + return &ServerConn{s, perms}, s.mux.incomingChannels, s.mux.incomingRequests, nil +} + +// signAndMarshal signs the data with the appropriate algorithm, +// and serializes the result in SSH wire format. algo is the negotiate +// algorithm and may be a certificate type. +func signAndMarshal(k AlgorithmSigner, rand io.Reader, data []byte, algo string) ([]byte, error) { + sig, err := k.SignWithAlgorithm(rand, data, underlyingAlgo(algo)) + if err != nil { + return nil, err + } + + return Marshal(sig), nil +} + +// handshake performs key exchange and user authentication. +func (s *connection) serverHandshake(config *ServerConfig) (*Permissions, error) { + if len(config.hostKeys) == 0 { + return nil, errors.New("ssh: server has no host keys") + } + + if !config.NoClientAuth && config.PasswordCallback == nil && config.PublicKeyCallback == nil && + config.KeyboardInteractiveCallback == nil && (config.GSSAPIWithMICConfig == nil || + config.GSSAPIWithMICConfig.AllowLogin == nil || config.GSSAPIWithMICConfig.Server == nil) { + return nil, errors.New("ssh: no authentication methods configured but NoClientAuth is also false") + } + + if config.ServerVersion != "" { + s.serverVersion = []byte(config.ServerVersion) + } else { + s.serverVersion = []byte(packageVersion) + } + var err error + s.clientVersion, err = exchangeVersions(s.sshConn.conn, s.serverVersion) + if err != nil { + return nil, err + } + + tr := newTransport(s.sshConn.conn, config.Rand, false /* not client */) + s.transport = newServerTransport(tr, s.clientVersion, s.serverVersion, config) + + if err := s.transport.waitSession(); err != nil { + return nil, err + } + + // We just did the key change, so the session ID is established. + s.sessionID = s.transport.getSessionID() + + var packet []byte + if packet, err = s.transport.readPacket(); err != nil { + return nil, err + } + + var serviceRequest serviceRequestMsg + if err = Unmarshal(packet, &serviceRequest); err != nil { + return nil, err + } + if serviceRequest.Service != serviceUserAuth { + return nil, errors.New("ssh: requested service '" + serviceRequest.Service + "' before authenticating") + } + serviceAccept := serviceAcceptMsg{ + Service: serviceUserAuth, + } + if err := s.transport.writePacket(Marshal(&serviceAccept)); err != nil { + return nil, err + } + + perms, err := s.serverAuthenticate(config) + if err != nil { + return nil, err + } + s.mux = newMux(s.transport) + return perms, err +} + +func checkSourceAddress(addr net.Addr, sourceAddrs string) error { + if addr == nil { + return errors.New("ssh: no address known for client, but source-address match required") + } + + tcpAddr, ok := addr.(*net.TCPAddr) + if !ok { + return fmt.Errorf("ssh: remote address %v is not an TCP address when checking source-address match", addr) + } + + for _, sourceAddr := range strings.Split(sourceAddrs, ",") { + if allowedIP := net.ParseIP(sourceAddr); allowedIP != nil { + if allowedIP.Equal(tcpAddr.IP) { + return nil + } + } else { + _, ipNet, err := net.ParseCIDR(sourceAddr) + if err != nil { + return fmt.Errorf("ssh: error parsing source-address restriction %q: %v", sourceAddr, err) + } + + if ipNet.Contains(tcpAddr.IP) { + return nil + } + } + } + + return fmt.Errorf("ssh: remote address %v is not allowed because of source-address restriction", addr) +} + +func gssExchangeToken(gssapiConfig *GSSAPIWithMICConfig, token []byte, s *connection, + sessionID []byte, userAuthReq userAuthRequestMsg) (authErr error, perms *Permissions, err error) { + gssAPIServer := gssapiConfig.Server + defer gssAPIServer.DeleteSecContext() + var srcName string + for { + var ( + outToken []byte + needContinue bool + ) + outToken, srcName, needContinue, err = gssAPIServer.AcceptSecContext(token) + if err != nil { + return err, nil, nil + } + if len(outToken) != 0 { + if err := s.transport.writePacket(Marshal(&userAuthGSSAPIToken{ + Token: outToken, + })); err != nil { + return nil, nil, err + } + } + if !needContinue { + break + } + packet, err := s.transport.readPacket() + if err != nil { + return nil, nil, err + } + userAuthGSSAPITokenReq := &userAuthGSSAPIToken{} + if err := Unmarshal(packet, userAuthGSSAPITokenReq); err != nil { + return nil, nil, err + } + token = userAuthGSSAPITokenReq.Token + } + packet, err := s.transport.readPacket() + if err != nil { + return nil, nil, err + } + userAuthGSSAPIMICReq := &userAuthGSSAPIMIC{} + if err := Unmarshal(packet, userAuthGSSAPIMICReq); err != nil { + return nil, nil, err + } + mic := buildMIC(string(sessionID), userAuthReq.User, userAuthReq.Service, userAuthReq.Method) + if err := gssAPIServer.VerifyMIC(mic, userAuthGSSAPIMICReq.MIC); err != nil { + return err, nil, nil + } + perms, authErr = gssapiConfig.AllowLogin(s, srcName) + return authErr, perms, nil +} + +// isAlgoCompatible checks if the signature format is compatible with the +// selected algorithm taking into account edge cases that occur with old +// clients. +func isAlgoCompatible(algo, sigFormat string) bool { + // Compatibility for old clients. + // + // For certificate authentication with OpenSSH 7.2-7.7 signature format can + // be rsa-sha2-256 or rsa-sha2-512 for the algorithm + // ssh-rsa-cert-v01@openssh.com. + // + // With gpg-agent < 2.2.6 the algorithm can be rsa-sha2-256 or rsa-sha2-512 + // for signature format ssh-rsa. + if isRSA(algo) && isRSA(sigFormat) { + return true + } + // Standard case: the underlying algorithm must match the signature format. + return underlyingAlgo(algo) == sigFormat +} + +// ServerAuthError represents server authentication errors and is +// sometimes returned by NewServerConn. It appends any authentication +// errors that may occur, and is returned if all of the authentication +// methods provided by the user failed to authenticate. +type ServerAuthError struct { + // Errors contains authentication errors returned by the authentication + // callback methods. The first entry is typically ErrNoAuth. + Errors []error +} + +func (l ServerAuthError) Error() string { + var errs []string + for _, err := range l.Errors { + errs = append(errs, err.Error()) + } + return "[" + strings.Join(errs, ", ") + "]" +} + +// ErrNoAuth is the error value returned if no +// authentication method has been passed yet. This happens as a normal +// part of the authentication loop, since the client first tries +// 'none' authentication to discover available methods. +// It is returned in ServerAuthError.Errors from NewServerConn. +var ErrNoAuth = errors.New("ssh: no auth passed yet") + +func (s *connection) serverAuthenticate(config *ServerConfig) (*Permissions, error) { + sessionID := s.transport.getSessionID() + var cache pubKeyCache + var perms *Permissions + + authFailures := 0 + var authErrs []error + var displayedBanner bool + +userAuthLoop: + for { + if authFailures >= config.MaxAuthTries && config.MaxAuthTries > 0 { + discMsg := &disconnectMsg{ + Reason: 2, + Message: "too many authentication failures", + } + + if err := s.transport.writePacket(Marshal(discMsg)); err != nil { + return nil, err + } + + return nil, discMsg + } + + var userAuthReq userAuthRequestMsg + if packet, err := s.transport.readPacket(); err != nil { + if err == io.EOF { + return nil, &ServerAuthError{Errors: authErrs} + } + return nil, err + } else if err = Unmarshal(packet, &userAuthReq); err != nil { + return nil, err + } + + if userAuthReq.Service != serviceSSH { + return nil, errors.New("ssh: client attempted to negotiate for unknown service: " + userAuthReq.Service) + } + + s.user = userAuthReq.User + + if !displayedBanner && config.BannerCallback != nil { + displayedBanner = true + msg := config.BannerCallback(s) + if msg != "" { + bannerMsg := &userAuthBannerMsg{ + Message: msg, + } + if err := s.transport.writePacket(Marshal(bannerMsg)); err != nil { + return nil, err + } + } + } + + perms = nil + authErr := ErrNoAuth + + switch userAuthReq.Method { + case "none": + if config.NoClientAuth { + if config.NoClientAuthCallback != nil { + perms, authErr = config.NoClientAuthCallback(s) + } else { + authErr = nil + } + } + + // allow initial attempt of 'none' without penalty + if authFailures == 0 { + authFailures-- + } + case "password": + if config.PasswordCallback == nil { + authErr = errors.New("ssh: password auth not configured") + break + } + payload := userAuthReq.Payload + if len(payload) < 1 || payload[0] != 0 { + return nil, parseError(msgUserAuthRequest) + } + payload = payload[1:] + password, payload, ok := parseString(payload) + if !ok || len(payload) > 0 { + return nil, parseError(msgUserAuthRequest) + } + + perms, authErr = config.PasswordCallback(s, password) + case "keyboard-interactive": + if config.KeyboardInteractiveCallback == nil { + authErr = errors.New("ssh: keyboard-interactive auth not configured") + break + } + + prompter := &sshClientKeyboardInteractive{s} + perms, authErr = config.KeyboardInteractiveCallback(s, prompter.Challenge) + case "publickey": + if config.PublicKeyCallback == nil { + authErr = errors.New("ssh: publickey auth not configured") + break + } + payload := userAuthReq.Payload + if len(payload) < 1 { + return nil, parseError(msgUserAuthRequest) + } + isQuery := payload[0] == 0 + payload = payload[1:] + algoBytes, payload, ok := parseString(payload) + if !ok { + return nil, parseError(msgUserAuthRequest) + } + algo := string(algoBytes) + if !contains(config.PublicKeyAuthAlgorithms, underlyingAlgo(algo)) { + authErr = fmt.Errorf("ssh: algorithm %q not accepted", algo) + break + } + + pubKeyData, payload, ok := parseString(payload) + if !ok { + return nil, parseError(msgUserAuthRequest) + } + + pubKey, err := ParsePublicKey(pubKeyData) + if err != nil { + return nil, err + } + + candidate, ok := cache.get(s.user, pubKeyData) + if !ok { + candidate.user = s.user + candidate.pubKeyData = pubKeyData + candidate.perms, candidate.result = config.PublicKeyCallback(s, pubKey) + if candidate.result == nil && candidate.perms != nil && candidate.perms.CriticalOptions != nil && candidate.perms.CriticalOptions[sourceAddressCriticalOption] != "" { + candidate.result = checkSourceAddress( + s.RemoteAddr(), + candidate.perms.CriticalOptions[sourceAddressCriticalOption]) + } + cache.add(candidate) + } + + if isQuery { + // The client can query if the given public key + // would be okay. + + if len(payload) > 0 { + return nil, parseError(msgUserAuthRequest) + } + + if candidate.result == nil { + okMsg := userAuthPubKeyOkMsg{ + Algo: algo, + PubKey: pubKeyData, + } + if err = s.transport.writePacket(Marshal(&okMsg)); err != nil { + return nil, err + } + continue userAuthLoop + } + authErr = candidate.result + } else { + sig, payload, ok := parseSignature(payload) + if !ok || len(payload) > 0 { + return nil, parseError(msgUserAuthRequest) + } + // Ensure the declared public key algo is compatible with the + // decoded one. This check will ensure we don't accept e.g. + // ssh-rsa-cert-v01@openssh.com algorithm with ssh-rsa public + // key type. The algorithm and public key type must be + // consistent: both must be certificate algorithms, or neither. + if !contains(algorithmsForKeyFormat(pubKey.Type()), algo) { + authErr = fmt.Errorf("ssh: public key type %q not compatible with selected algorithm %q", + pubKey.Type(), algo) + break + } + // Ensure the public key algo and signature algo + // are supported. Compare the private key + // algorithm name that corresponds to algo with + // sig.Format. This is usually the same, but + // for certs, the names differ. + if !contains(config.PublicKeyAuthAlgorithms, sig.Format) { + authErr = fmt.Errorf("ssh: algorithm %q not accepted", sig.Format) + break + } + if !isAlgoCompatible(algo, sig.Format) { + authErr = fmt.Errorf("ssh: signature %q not compatible with selected algorithm %q", sig.Format, algo) + break + } + + signedData := buildDataSignedForAuth(sessionID, userAuthReq, algo, pubKeyData) + + if err := pubKey.Verify(signedData, sig); err != nil { + return nil, err + } + + authErr = candidate.result + perms = candidate.perms + } + case "gssapi-with-mic": + if config.GSSAPIWithMICConfig == nil { + authErr = errors.New("ssh: gssapi-with-mic auth not configured") + break + } + gssapiConfig := config.GSSAPIWithMICConfig + userAuthRequestGSSAPI, err := parseGSSAPIPayload(userAuthReq.Payload) + if err != nil { + return nil, parseError(msgUserAuthRequest) + } + // OpenSSH supports Kerberos V5 mechanism only for GSS-API authentication. + if userAuthRequestGSSAPI.N == 0 { + authErr = fmt.Errorf("ssh: Mechanism negotiation is not supported") + break + } + var i uint32 + present := false + for i = 0; i < userAuthRequestGSSAPI.N; i++ { + if userAuthRequestGSSAPI.OIDS[i].Equal(krb5Mesh) { + present = true + break + } + } + if !present { + authErr = fmt.Errorf("ssh: GSSAPI authentication must use the Kerberos V5 mechanism") + break + } + // Initial server response, see RFC 4462 section 3.3. + if err := s.transport.writePacket(Marshal(&userAuthGSSAPIResponse{ + SupportMech: krb5OID, + })); err != nil { + return nil, err + } + // Exchange token, see RFC 4462 section 3.4. + packet, err := s.transport.readPacket() + if err != nil { + return nil, err + } + userAuthGSSAPITokenReq := &userAuthGSSAPIToken{} + if err := Unmarshal(packet, userAuthGSSAPITokenReq); err != nil { + return nil, err + } + authErr, perms, err = gssExchangeToken(gssapiConfig, userAuthGSSAPITokenReq.Token, s, sessionID, + userAuthReq) + if err != nil { + return nil, err + } + default: + authErr = fmt.Errorf("ssh: unknown method %q", userAuthReq.Method) + } + + authErrs = append(authErrs, authErr) + + if config.AuthLogCallback != nil { + config.AuthLogCallback(s, userAuthReq.Method, authErr) + } + + if authErr == nil { + break userAuthLoop + } + + authFailures++ + if config.MaxAuthTries > 0 && authFailures >= config.MaxAuthTries { + // If we have hit the max attempts, don't bother sending the + // final SSH_MSG_USERAUTH_FAILURE message, since there are + // no more authentication methods which can be attempted, + // and this message may cause the client to re-attempt + // authentication while we send the disconnect message. + // Continue, and trigger the disconnect at the start of + // the loop. + // + // The SSH specification is somewhat confusing about this, + // RFC 4252 Section 5.1 requires each authentication failure + // be responded to with a respective SSH_MSG_USERAUTH_FAILURE + // message, but Section 4 says the server should disconnect + // after some number of attempts, but it isn't explicit which + // message should take precedence (i.e. should there be a failure + // message than a disconnect message, or if we are going to + // disconnect, should we only send that message.) + // + // Either way, OpenSSH disconnects immediately after the last + // failed authnetication attempt, and given they are typically + // considered the golden implementation it seems reasonable + // to match that behavior. + continue + } + + var failureMsg userAuthFailureMsg + if config.PasswordCallback != nil { + failureMsg.Methods = append(failureMsg.Methods, "password") + } + if config.PublicKeyCallback != nil { + failureMsg.Methods = append(failureMsg.Methods, "publickey") + } + if config.KeyboardInteractiveCallback != nil { + failureMsg.Methods = append(failureMsg.Methods, "keyboard-interactive") + } + if config.GSSAPIWithMICConfig != nil && config.GSSAPIWithMICConfig.Server != nil && + config.GSSAPIWithMICConfig.AllowLogin != nil { + failureMsg.Methods = append(failureMsg.Methods, "gssapi-with-mic") + } + + if len(failureMsg.Methods) == 0 { + return nil, errors.New("ssh: no authentication methods configured but NoClientAuth is also false") + } + + if err := s.transport.writePacket(Marshal(&failureMsg)); err != nil { + return nil, err + } + } + + if err := s.transport.writePacket([]byte{msgUserAuthSuccess}); err != nil { + return nil, err + } + return perms, nil +} + +// sshClientKeyboardInteractive implements a ClientKeyboardInteractive by +// asking the client on the other side of a ServerConn. +type sshClientKeyboardInteractive struct { + *connection +} + +func (c *sshClientKeyboardInteractive) Challenge(name, instruction string, questions []string, echos []bool) (answers []string, err error) { + if len(questions) != len(echos) { + return nil, errors.New("ssh: echos and questions must have equal length") + } + + var prompts []byte + for i := range questions { + prompts = appendString(prompts, questions[i]) + prompts = appendBool(prompts, echos[i]) + } + + if err := c.transport.writePacket(Marshal(&userAuthInfoRequestMsg{ + Name: name, + Instruction: instruction, + NumPrompts: uint32(len(questions)), + Prompts: prompts, + })); err != nil { + return nil, err + } + + packet, err := c.transport.readPacket() + if err != nil { + return nil, err + } + if packet[0] != msgUserAuthInfoResponse { + return nil, unexpectedMessageError(msgUserAuthInfoResponse, packet[0]) + } + packet = packet[1:] + + n, packet, ok := parseUint32(packet) + if !ok || int(n) != len(questions) { + return nil, parseError(msgUserAuthInfoResponse) + } + + for i := uint32(0); i < n; i++ { + ans, rest, ok := parseString(packet) + if !ok { + return nil, parseError(msgUserAuthInfoResponse) + } + + answers = append(answers, string(ans)) + packet = rest + } + if len(packet) != 0 { + return nil, errors.New("ssh: junk at end of message") + } + + return answers, nil +} diff --git a/pkg/proto/ssh/session.go b/pkg/proto/ssh/session.go new file mode 100644 index 0000000..acef622 --- /dev/null +++ b/pkg/proto/ssh/session.go @@ -0,0 +1,647 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +// Session implements an interactive session described in +// "RFC 4254, section 6". + +import ( + "bytes" + "encoding/binary" + "errors" + "fmt" + "io" + "sync" +) + +type Signal string + +// POSIX signals as listed in RFC 4254 Section 6.10. +const ( + SIGABRT Signal = "ABRT" + SIGALRM Signal = "ALRM" + SIGFPE Signal = "FPE" + SIGHUP Signal = "HUP" + SIGILL Signal = "ILL" + SIGINT Signal = "INT" + SIGKILL Signal = "KILL" + SIGPIPE Signal = "PIPE" + SIGQUIT Signal = "QUIT" + SIGSEGV Signal = "SEGV" + SIGTERM Signal = "TERM" + SIGUSR1 Signal = "USR1" + SIGUSR2 Signal = "USR2" +) + +var signals = map[Signal]int{ + SIGABRT: 6, + SIGALRM: 14, + SIGFPE: 8, + SIGHUP: 1, + SIGILL: 4, + SIGINT: 2, + SIGKILL: 9, + SIGPIPE: 13, + SIGQUIT: 3, + SIGSEGV: 11, + SIGTERM: 15, +} + +type TerminalModes map[uint8]uint32 + +// POSIX terminal mode flags as listed in RFC 4254 Section 8. +const ( + tty_OP_END = 0 + VINTR = 1 + VQUIT = 2 + VERASE = 3 + VKILL = 4 + VEOF = 5 + VEOL = 6 + VEOL2 = 7 + VSTART = 8 + VSTOP = 9 + VSUSP = 10 + VDSUSP = 11 + VREPRINT = 12 + VWERASE = 13 + VLNEXT = 14 + VFLUSH = 15 + VSWTCH = 16 + VSTATUS = 17 + VDISCARD = 18 + IGNPAR = 30 + PARMRK = 31 + INPCK = 32 + ISTRIP = 33 + INLCR = 34 + IGNCR = 35 + ICRNL = 36 + IUCLC = 37 + IXON = 38 + IXANY = 39 + IXOFF = 40 + IMAXBEL = 41 + IUTF8 = 42 // RFC 8160 + ISIG = 50 + ICANON = 51 + XCASE = 52 + ECHO = 53 + ECHOE = 54 + ECHOK = 55 + ECHONL = 56 + NOFLSH = 57 + TOSTOP = 58 + IEXTEN = 59 + ECHOCTL = 60 + ECHOKE = 61 + PENDIN = 62 + OPOST = 70 + OLCUC = 71 + ONLCR = 72 + OCRNL = 73 + ONOCR = 74 + ONLRET = 75 + CS7 = 90 + CS8 = 91 + PARENB = 92 + PARODD = 93 + TTY_OP_ISPEED = 128 + TTY_OP_OSPEED = 129 +) + +// A Session represents a connection to a remote command or shell. +type Session struct { + // Stdin specifies the remote process's standard input. + // If Stdin is nil, the remote process reads from an empty + // bytes.Buffer. + Stdin io.Reader + + // Stdout and Stderr specify the remote process's standard + // output and error. + // + // If either is nil, Run connects the corresponding file + // descriptor to an instance of io.Discard. There is a + // fixed amount of buffering that is shared for the two streams. + // If either blocks it may eventually cause the remote + // command to block. + Stdout io.Writer + Stderr io.Writer + + ch Channel // the channel backing this session + started bool // true once Start, Run or Shell is invoked. + copyFuncs []func() error + errors chan error // one send per copyFunc + + // true if pipe method is active + stdinpipe, stdoutpipe, stderrpipe bool + + // stdinPipeWriter is non-nil if StdinPipe has not been called + // and Stdin was specified by the user; it is the write end of + // a pipe connecting Session.Stdin to the stdin channel. + stdinPipeWriter io.WriteCloser + + exitStatus chan error +} + +// SendRequest sends an out-of-band channel request on the SSH channel +// underlying the session. +func (s *Session) SendRequest(name string, wantReply bool, payload []byte) (bool, error) { + return s.ch.SendRequest(name, wantReply, payload) +} + +func (s *Session) Close() error { + return s.ch.Close() +} + +// RFC 4254 Section 6.4. +type setenvRequest struct { + Name string + Value string +} + +// Setenv sets an environment variable that will be applied to any +// command executed by Shell or Run. +func (s *Session) Setenv(name, value string) error { + msg := setenvRequest{ + Name: name, + Value: value, + } + ok, err := s.ch.SendRequest("env", true, Marshal(&msg)) + if err == nil && !ok { + err = errors.New("ssh: setenv failed") + } + return err +} + +// RFC 4254 Section 6.2. +type ptyRequestMsg struct { + Term string + Columns uint32 + Rows uint32 + Width uint32 + Height uint32 + Modelist string +} + +// RequestPty requests the association of a pty with the session on the remote host. +func (s *Session) RequestPty(term string, h, w int, termmodes TerminalModes) error { + var tm []byte + for k, v := range termmodes { + kv := struct { + Key byte + Val uint32 + }{k, v} + + tm = append(tm, Marshal(&kv)...) + } + tm = append(tm, tty_OP_END) + req := ptyRequestMsg{ + Term: term, + Columns: uint32(w), + Rows: uint32(h), + Width: uint32(w * 8), + Height: uint32(h * 8), + Modelist: string(tm), + } + ok, err := s.ch.SendRequest("pty-req", true, Marshal(&req)) + if err == nil && !ok { + err = errors.New("ssh: pty-req failed") + } + return err +} + +// RFC 4254 Section 6.5. +type subsystemRequestMsg struct { + Subsystem string +} + +// RequestSubsystem requests the association of a subsystem with the session on the remote host. +// A subsystem is a predefined command that runs in the background when the ssh session is initiated +func (s *Session) RequestSubsystem(subsystem string) error { + msg := subsystemRequestMsg{ + Subsystem: subsystem, + } + ok, err := s.ch.SendRequest("subsystem", true, Marshal(&msg)) + if err == nil && !ok { + err = errors.New("ssh: subsystem request failed") + } + return err +} + +// RFC 4254 Section 6.7. +type ptyWindowChangeMsg struct { + Columns uint32 + Rows uint32 + Width uint32 + Height uint32 +} + +// WindowChange informs the remote host about a terminal window dimension change to h rows and w columns. +func (s *Session) WindowChange(h, w int) error { + req := ptyWindowChangeMsg{ + Columns: uint32(w), + Rows: uint32(h), + Width: uint32(w * 8), + Height: uint32(h * 8), + } + _, err := s.ch.SendRequest("window-change", false, Marshal(&req)) + return err +} + +// RFC 4254 Section 6.9. +type signalMsg struct { + Signal string +} + +// Signal sends the given signal to the remote process. +// sig is one of the SIG* constants. +func (s *Session) Signal(sig Signal) error { + msg := signalMsg{ + Signal: string(sig), + } + + _, err := s.ch.SendRequest("signal", false, Marshal(&msg)) + return err +} + +// RFC 4254 Section 6.5. +type execMsg struct { + Command string +} + +// Start runs cmd on the remote host. Typically, the remote +// server passes cmd to the shell for interpretation. +// A Session only accepts one call to Run, Start or Shell. +func (s *Session) Start(cmd string) error { + if s.started { + return errors.New("ssh: session already started") + } + req := execMsg{ + Command: cmd, + } + + ok, err := s.ch.SendRequest("exec", true, Marshal(&req)) + if err == nil && !ok { + err = fmt.Errorf("ssh: command %v failed", cmd) + } + if err != nil { + return err + } + return s.start() +} + +// Run runs cmd on the remote host. Typically, the remote +// server passes cmd to the shell for interpretation. +// A Session only accepts one call to Run, Start, Shell, Output, +// or CombinedOutput. +// +// The returned error is nil if the command runs, has no problems +// copying stdin, stdout, and stderr, and exits with a zero exit +// status. +// +// If the remote server does not send an exit status, an error of type +// *ExitMissingError is returned. If the command completes +// unsuccessfully or is interrupted by a signal, the error is of type +// *ExitError. Other error types may be returned for I/O problems. +func (s *Session) Run(cmd string) error { + err := s.Start(cmd) + if err != nil { + return err + } + return s.Wait() +} + +// Output runs cmd on the remote host and returns its standard output. +func (s *Session) Output(cmd string) ([]byte, error) { + if s.Stdout != nil { + return nil, errors.New("ssh: Stdout already set") + } + var b bytes.Buffer + s.Stdout = &b + err := s.Run(cmd) + return b.Bytes(), err +} + +type singleWriter struct { + b bytes.Buffer + mu sync.Mutex +} + +func (w *singleWriter) Write(p []byte) (int, error) { + w.mu.Lock() + defer w.mu.Unlock() + return w.b.Write(p) +} + +// CombinedOutput runs cmd on the remote host and returns its combined +// standard output and standard error. +func (s *Session) CombinedOutput(cmd string) ([]byte, error) { + if s.Stdout != nil { + return nil, errors.New("ssh: Stdout already set") + } + if s.Stderr != nil { + return nil, errors.New("ssh: Stderr already set") + } + var b singleWriter + s.Stdout = &b + s.Stderr = &b + err := s.Run(cmd) + return b.b.Bytes(), err +} + +// Shell starts a login shell on the remote host. A Session only +// accepts one call to Run, Start, Shell, Output, or CombinedOutput. +func (s *Session) Shell() error { + if s.started { + return errors.New("ssh: session already started") + } + + ok, err := s.ch.SendRequest("shell", true, nil) + if err == nil && !ok { + return errors.New("ssh: could not start shell") + } + if err != nil { + return err + } + return s.start() +} + +func (s *Session) start() error { + s.started = true + + type F func(*Session) + for _, setupFd := range []F{(*Session).stdin, (*Session).stdout, (*Session).stderr} { + setupFd(s) + } + + s.errors = make(chan error, len(s.copyFuncs)) + for _, fn := range s.copyFuncs { + go func(fn func() error) { + s.errors <- fn() + }(fn) + } + return nil +} + +// Wait waits for the remote command to exit. +// +// The returned error is nil if the command runs, has no problems +// copying stdin, stdout, and stderr, and exits with a zero exit +// status. +// +// If the remote server does not send an exit status, an error of type +// *ExitMissingError is returned. If the command completes +// unsuccessfully or is interrupted by a signal, the error is of type +// *ExitError. Other error types may be returned for I/O problems. +func (s *Session) Wait() error { + if !s.started { + return errors.New("ssh: session not started") + } + waitErr := <-s.exitStatus + + if s.stdinPipeWriter != nil { + s.stdinPipeWriter.Close() + } + var copyError error + for range s.copyFuncs { + if err := <-s.errors; err != nil && copyError == nil { + copyError = err + } + } + if waitErr != nil { + return waitErr + } + return copyError +} + +func (s *Session) wait(reqs <-chan *Request) error { + wm := Waitmsg{status: -1} + // Wait for msg channel to be closed before returning. + for msg := range reqs { + switch msg.Type { + case "exit-status": + wm.status = int(binary.BigEndian.Uint32(msg.Payload)) + case "exit-signal": + var sigval struct { + Signal string + CoreDumped bool + Error string + Lang string + } + if err := Unmarshal(msg.Payload, &sigval); err != nil { + return err + } + + // Must sanitize strings? + wm.signal = sigval.Signal + wm.msg = sigval.Error + wm.lang = sigval.Lang + default: + // This handles keepalives and matches + // OpenSSH's behaviour. + if msg.WantReply { + msg.Reply(false, nil) + } + } + } + if wm.status == 0 { + return nil + } + if wm.status == -1 { + // exit-status was never sent from server + if wm.signal == "" { + // signal was not sent either. RFC 4254 + // section 6.10 recommends against this + // behavior, but it is allowed, so we let + // clients handle it. + return &ExitMissingError{} + } + wm.status = 128 + if _, ok := signals[Signal(wm.signal)]; ok { + wm.status += signals[Signal(wm.signal)] + } + } + + return &ExitError{wm} +} + +// ExitMissingError is returned if a session is torn down cleanly, but +// the server sends no confirmation of the exit status. +type ExitMissingError struct{} + +func (e *ExitMissingError) Error() string { + return "wait: remote command exited without exit status or exit signal" +} + +func (s *Session) stdin() { + if s.stdinpipe { + return + } + var stdin io.Reader + if s.Stdin == nil { + stdin = new(bytes.Buffer) + } else { + r, w := io.Pipe() + go func() { + _, err := io.Copy(w, s.Stdin) + w.CloseWithError(err) + }() + stdin, s.stdinPipeWriter = r, w + } + s.copyFuncs = append(s.copyFuncs, func() error { + _, err := io.Copy(s.ch, stdin) + if err1 := s.ch.CloseWrite(); err == nil && err1 != io.EOF { + err = err1 + } + return err + }) +} + +func (s *Session) stdout() { + if s.stdoutpipe { + return + } + if s.Stdout == nil { + s.Stdout = io.Discard + } + s.copyFuncs = append(s.copyFuncs, func() error { + _, err := io.Copy(s.Stdout, s.ch) + return err + }) +} + +func (s *Session) stderr() { + if s.stderrpipe { + return + } + if s.Stderr == nil { + s.Stderr = io.Discard + } + s.copyFuncs = append(s.copyFuncs, func() error { + _, err := io.Copy(s.Stderr, s.ch.Stderr()) + return err + }) +} + +// sessionStdin reroutes Close to CloseWrite. +type sessionStdin struct { + io.Writer + ch Channel +} + +func (s *sessionStdin) Close() error { + return s.ch.CloseWrite() +} + +// StdinPipe returns a pipe that will be connected to the +// remote command's standard input when the command starts. +func (s *Session) StdinPipe() (io.WriteCloser, error) { + if s.Stdin != nil { + return nil, errors.New("ssh: Stdin already set") + } + if s.started { + return nil, errors.New("ssh: StdinPipe after process started") + } + s.stdinpipe = true + return &sessionStdin{s.ch, s.ch}, nil +} + +// StdoutPipe returns a pipe that will be connected to the +// remote command's standard output when the command starts. +// There is a fixed amount of buffering that is shared between +// stdout and stderr streams. If the StdoutPipe reader is +// not serviced fast enough it may eventually cause the +// remote command to block. +func (s *Session) StdoutPipe() (io.Reader, error) { + if s.Stdout != nil { + return nil, errors.New("ssh: Stdout already set") + } + if s.started { + return nil, errors.New("ssh: StdoutPipe after process started") + } + s.stdoutpipe = true + return s.ch, nil +} + +// StderrPipe returns a pipe that will be connected to the +// remote command's standard error when the command starts. +// There is a fixed amount of buffering that is shared between +// stdout and stderr streams. If the StderrPipe reader is +// not serviced fast enough it may eventually cause the +// remote command to block. +func (s *Session) StderrPipe() (io.Reader, error) { + if s.Stderr != nil { + return nil, errors.New("ssh: Stderr already set") + } + if s.started { + return nil, errors.New("ssh: StderrPipe after process started") + } + s.stderrpipe = true + return s.ch.Stderr(), nil +} + +// newSession returns a new interactive session on the remote host. +func newSession(ch Channel, reqs <-chan *Request) (*Session, error) { + s := &Session{ + ch: ch, + } + s.exitStatus = make(chan error, 1) + go func() { + s.exitStatus <- s.wait(reqs) + }() + + return s, nil +} + +// An ExitError reports unsuccessful completion of a remote command. +type ExitError struct { + Waitmsg +} + +func (e *ExitError) Error() string { + return e.Waitmsg.String() +} + +// Waitmsg stores the information about an exited remote command +// as reported by Wait. +type Waitmsg struct { + status int + signal string + msg string + lang string +} + +// ExitStatus returns the exit status of the remote command. +func (w Waitmsg) ExitStatus() int { + return w.status +} + +// Signal returns the exit signal of the remote command if +// it was terminated violently. +func (w Waitmsg) Signal() string { + return w.signal +} + +// Msg returns the exit message given by the remote command +func (w Waitmsg) Msg() string { + return w.msg +} + +// Lang returns the language tag. See RFC 3066 +func (w Waitmsg) Lang() string { + return w.lang +} + +func (w Waitmsg) String() string { + str := fmt.Sprintf("Process exited with status %v", w.status) + if w.signal != "" { + str += fmt.Sprintf(" from signal %v", w.signal) + } + if w.msg != "" { + str += fmt.Sprintf(". Reason was: %v", w.msg) + } + return str +} diff --git a/pkg/proto/ssh/ssh_gss.go b/pkg/proto/ssh/ssh_gss.go new file mode 100644 index 0000000..24bd7c8 --- /dev/null +++ b/pkg/proto/ssh/ssh_gss.go @@ -0,0 +1,139 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "encoding/asn1" + "errors" +) + +var krb5OID []byte + +func init() { + krb5OID, _ = asn1.Marshal(krb5Mesh) +} + +// GSSAPIClient provides the API to plug-in GSSAPI authentication for client logins. +type GSSAPIClient interface { + // InitSecContext initiates the establishment of a security context for GSS-API between the + // ssh client and ssh server. Initially the token parameter should be specified as nil. + // The routine may return a outputToken which should be transferred to + // the ssh server, where the ssh server will present it to + // AcceptSecContext. If no token need be sent, InitSecContext will indicate this by setting + // needContinue to false. To complete the context + // establishment, one or more reply tokens may be required from the ssh + // server;if so, InitSecContext will return a needContinue which is true. + // In this case, InitSecContext should be called again when the + // reply token is received from the ssh server, passing the reply + // token to InitSecContext via the token parameters. + // See RFC 2743 section 2.2.1 and RFC 4462 section 3.4. + InitSecContext(target string, token []byte, isGSSDelegCreds bool) (outputToken []byte, needContinue bool, err error) + // GetMIC generates a cryptographic MIC for the SSH2 message, and places + // the MIC in a token for transfer to the ssh server. + // The contents of the MIC field are obtained by calling GSS_GetMIC() + // over the following, using the GSS-API context that was just + // established: + // string session identifier + // byte SSH_MSG_USERAUTH_REQUEST + // string user name + // string service + // string "gssapi-with-mic" + // See RFC 2743 section 2.3.1 and RFC 4462 3.5. + GetMIC(micFiled []byte) ([]byte, error) + // Whenever possible, it should be possible for + // DeleteSecContext() calls to be successfully processed even + // if other calls cannot succeed, thereby enabling context-related + // resources to be released. + // In addition to deleting established security contexts, + // gss_delete_sec_context must also be able to delete "half-built" + // security contexts resulting from an incomplete sequence of + // InitSecContext()/AcceptSecContext() calls. + // See RFC 2743 section 2.2.3. + DeleteSecContext() error +} + +// GSSAPIServer provides the API to plug in GSSAPI authentication for server logins. +type GSSAPIServer interface { + // AcceptSecContext allows a remotely initiated security context between the application + // and a remote peer to be established by the ssh client. The routine may return a + // outputToken which should be transferred to the ssh client, + // where the ssh client will present it to InitSecContext. + // If no token need be sent, AcceptSecContext will indicate this + // by setting the needContinue to false. To + // complete the context establishment, one or more reply tokens may be + // required from the ssh client. if so, AcceptSecContext + // will return a needContinue which is true, in which case it + // should be called again when the reply token is received from the ssh + // client, passing the token to AcceptSecContext via the + // token parameters. + // The srcName return value is the authenticated username. + // See RFC 2743 section 2.2.2 and RFC 4462 section 3.4. + AcceptSecContext(token []byte) (outputToken []byte, srcName string, needContinue bool, err error) + // VerifyMIC verifies that a cryptographic MIC, contained in the token parameter, + // fits the supplied message is received from the ssh client. + // See RFC 2743 section 2.3.2. + VerifyMIC(micField []byte, micToken []byte) error + // Whenever possible, it should be possible for + // DeleteSecContext() calls to be successfully processed even + // if other calls cannot succeed, thereby enabling context-related + // resources to be released. + // In addition to deleting established security contexts, + // gss_delete_sec_context must also be able to delete "half-built" + // security contexts resulting from an incomplete sequence of + // InitSecContext()/AcceptSecContext() calls. + // See RFC 2743 section 2.2.3. + DeleteSecContext() error +} + +var ( + // OpenSSH supports Kerberos V5 mechanism only for GSS-API authentication, + // so we also support the krb5 mechanism only. + // See RFC 1964 section 1. + krb5Mesh = asn1.ObjectIdentifier{1, 2, 840, 113554, 1, 2, 2} +) + +// The GSS-API authentication method is initiated when the client sends an SSH_MSG_USERAUTH_REQUEST +// See RFC 4462 section 3.2. +type userAuthRequestGSSAPI struct { + N uint32 + OIDS []asn1.ObjectIdentifier +} + +func parseGSSAPIPayload(payload []byte) (*userAuthRequestGSSAPI, error) { + n, rest, ok := parseUint32(payload) + if !ok { + return nil, errors.New("parse uint32 failed") + } + s := &userAuthRequestGSSAPI{ + N: n, + OIDS: make([]asn1.ObjectIdentifier, n), + } + for i := 0; i < int(n); i++ { + var ( + desiredMech []byte + err error + ) + desiredMech, rest, ok = parseString(rest) + if !ok { + return nil, errors.New("parse string failed") + } + if rest, err = asn1.Unmarshal(desiredMech, &s.OIDS[i]); err != nil { + return nil, err + } + + } + return s, nil +} + +// See RFC 4462 section 3.6. +func buildMIC(sessionID string, username string, service string, authMethod string) []byte { + out := make([]byte, 0, 0) + out = appendString(out, sessionID) + out = append(out, msgUserAuthRequest) + out = appendString(out, username) + out = appendString(out, service) + out = appendString(out, authMethod) + return out +} diff --git a/pkg/proto/ssh/streamlocal.go b/pkg/proto/ssh/streamlocal.go new file mode 100644 index 0000000..b171b33 --- /dev/null +++ b/pkg/proto/ssh/streamlocal.go @@ -0,0 +1,116 @@ +package ssh + +import ( + "errors" + "io" + "net" +) + +// streamLocalChannelOpenDirectMsg is a struct used for SSH_MSG_CHANNEL_OPEN message +// with "direct-streamlocal@openssh.com" string. +// +// See openssh-portable/PROTOCOL, section 2.4. connection: Unix domain socket forwarding +// https://github.com/openssh/openssh-portable/blob/master/PROTOCOL#L235 +type streamLocalChannelOpenDirectMsg struct { + socketPath string + reserved0 string + reserved1 uint32 +} + +// forwardedStreamLocalPayload is a struct used for SSH_MSG_CHANNEL_OPEN message +// with "forwarded-streamlocal@openssh.com" string. +type forwardedStreamLocalPayload struct { + SocketPath string + Reserved0 string +} + +// streamLocalChannelForwardMsg is a struct used for SSH2_MSG_GLOBAL_REQUEST message +// with "streamlocal-forward@openssh.com"/"cancel-streamlocal-forward@openssh.com" string. +type streamLocalChannelForwardMsg struct { + socketPath string +} + +// ListenUnix is similar to ListenTCP but uses a Unix domain socket. +func (c *Client) ListenUnix(socketPath string) (net.Listener, error) { + c.handleForwardsOnce.Do(c.handleForwards) + m := streamLocalChannelForwardMsg{ + socketPath, + } + // send message + ok, _, err := c.SendRequest("streamlocal-forward@openssh.com", true, Marshal(&m)) + if err != nil { + return nil, err + } + if !ok { + return nil, errors.New("ssh: streamlocal-forward@openssh.com request denied by peer") + } + ch := c.forwards.add(&net.UnixAddr{Name: socketPath, Net: "unix"}) + + return &unixListener{socketPath, c, ch}, nil +} + +func (c *Client) dialStreamLocal(socketPath string) (Channel, error) { + msg := streamLocalChannelOpenDirectMsg{ + socketPath: socketPath, + } + ch, in, err := c.OpenChannel("direct-streamlocal@openssh.com", Marshal(&msg)) + if err != nil { + return nil, err + } + go DiscardRequests(in) + return ch, err +} + +type unixListener struct { + socketPath string + + conn *Client + in <-chan forward +} + +// Accept waits for and returns the next connection to the listener. +func (l *unixListener) Accept() (net.Conn, error) { + s, ok := <-l.in + if !ok { + return nil, io.EOF + } + ch, incoming, err := s.newCh.Accept() + if err != nil { + return nil, err + } + go DiscardRequests(incoming) + + return &chanConn{ + Channel: ch, + laddr: &net.UnixAddr{ + Name: l.socketPath, + Net: "unix", + }, + raddr: &net.UnixAddr{ + Name: "@", + Net: "unix", + }, + }, nil +} + +// Close closes the listener. +func (l *unixListener) Close() error { + // this also closes the listener. + l.conn.forwards.remove(&net.UnixAddr{Name: l.socketPath, Net: "unix"}) + m := streamLocalChannelForwardMsg{ + l.socketPath, + } + ok, _, err := l.conn.SendRequest("cancel-streamlocal-forward@openssh.com", true, Marshal(&m)) + if err == nil && !ok { + err = errors.New("ssh: cancel-streamlocal-forward@openssh.com failed") + } + return err +} + +// Addr returns the listener's network address. +func (l *unixListener) Addr() net.Addr { + return &net.UnixAddr{ + Name: l.socketPath, + Net: "unix", + } +} diff --git a/pkg/proto/ssh/tcpip.go b/pkg/proto/ssh/tcpip.go new file mode 100644 index 0000000..f12cf97 --- /dev/null +++ b/pkg/proto/ssh/tcpip.go @@ -0,0 +1,478 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "errors" + "fmt" + "io" + "math/rand" + "net" + "strconv" + "strings" + "sync" + "time" +) + +// Listen requests the remote peer open a listening socket on +// addr. Incoming connections will be available by calling Accept on +// the returned net.Listener. The listener must be serviced, or the +// SSH connection may hang. +// N must be "tcp", "tcp4", "tcp6", or "unix". +func (c *Client) Listen(n, addr string) (net.Listener, error) { + switch n { + case "tcp", "tcp4", "tcp6": + laddr, err := net.ResolveTCPAddr(n, addr) + if err != nil { + return nil, err + } + return c.ListenTCP(laddr) + case "unix": + return c.ListenUnix(addr) + default: + return nil, fmt.Errorf("ssh: unsupported protocol: %s", n) + } +} + +// Automatic port allocation is broken with OpenSSH before 6.0. See +// also https://bugzilla.mindrot.org/show_bug.cgi?id=2017. In +// particular, OpenSSH 5.9 sends a channelOpenMsg with port number 0, +// rather than the actual port number. This means you can never open +// two different listeners with auto allocated ports. We work around +// this by trying explicit ports until we succeed. + +const openSSHPrefix = "OpenSSH_" + +var portRandomizer = rand.New(rand.NewSource(time.Now().UnixNano())) + +// isBrokenOpenSSHVersion returns true if the given version string +// specifies a version of OpenSSH that is known to have a bug in port +// forwarding. +func isBrokenOpenSSHVersion(versionStr string) bool { + i := strings.Index(versionStr, openSSHPrefix) + if i < 0 { + return false + } + i += len(openSSHPrefix) + j := i + for ; j < len(versionStr); j++ { + if versionStr[j] < '0' || versionStr[j] > '9' { + break + } + } + version, _ := strconv.Atoi(versionStr[i:j]) + return version < 6 +} + +// autoPortListenWorkaround simulates automatic port allocation by +// trying random ports repeatedly. +func (c *Client) autoPortListenWorkaround(laddr *net.TCPAddr) (net.Listener, error) { + var sshListener net.Listener + var err error + const tries = 10 + for i := 0; i < tries; i++ { + addr := *laddr + addr.Port = 1024 + portRandomizer.Intn(60000) + sshListener, err = c.ListenTCP(&addr) + if err == nil { + laddr.Port = addr.Port + return sshListener, err + } + } + return nil, fmt.Errorf("ssh: listen on random port failed after %d tries: %v", tries, err) +} + +// RFC 4254 7.1 +type channelForwardMsg struct { + addr string + rport uint32 +} + +// handleForwards starts goroutines handling forwarded connections. +// It's called on first use by (*Client).ListenTCP to not launch +// goroutines until needed. +func (c *Client) handleForwards() { + go c.forwards.handleChannels(c.HandleChannelOpen("forwarded-tcpip")) + go c.forwards.handleChannels(c.HandleChannelOpen("forwarded-streamlocal@openssh.com")) +} + +// ListenTCP requests the remote peer open a listening socket +// on laddr. Incoming connections will be available by calling +// Accept on the returned net.Listener. +func (c *Client) ListenTCP(laddr *net.TCPAddr, fakeHost ...string) (net.Listener, error) { + c.handleForwardsOnce.Do(c.handleForwards) + if laddr.Port == 0 && isBrokenOpenSSHVersion(string(c.ServerVersion())) { + return c.autoPortListenWorkaround(laddr) + } + + host := laddr.IP.String() + if len(fakeHost) > 0 { + host = fakeHost[0] + } + m := channelForwardMsg{ + host, + uint32(laddr.Port), + } + // send message + ok, resp, err := c.SendRequest("tcpip-forward", true, Marshal(&m)) + if err != nil { + return nil, err + } + if !ok { + return nil, errors.New("ssh: tcpip-forward request denied by peer") + } + + // If the original port was 0, then the remote side will + // supply a real port number in the response. + if laddr.Port == 0 { + var p struct { + Port uint32 + } + if err := Unmarshal(resp, &p); err != nil { + return nil, err + } + laddr.Port = int(p.Port) + } + + // Register this forward, using the port number we obtained. + ch := c.forwards.add(laddr) + + return &tcpListener{laddr, c, ch}, nil +} + +// forwardList stores a mapping between remote +// forward requests and the tcpListeners. +type forwardList struct { + sync.Mutex + entries []forwardEntry +} + +// forwardEntry represents an established mapping of a laddr on a +// remote ssh server to a channel connected to a tcpListener. +type forwardEntry struct { + laddr net.Addr + c chan forward +} + +// forward represents an incoming forwarded tcpip connection. The +// arguments to add/remove/lookup should be address as specified in +// the original forward-request. +type forward struct { + newCh NewChannel // the ssh client channel underlying this forward + raddr net.Addr // the raddr of the incoming connection +} + +func (l *forwardList) add(addr net.Addr) chan forward { + l.Lock() + defer l.Unlock() + f := forwardEntry{ + laddr: addr, + c: make(chan forward, 1), + } + l.entries = append(l.entries, f) + return f.c +} + +// See RFC 4254, section 7.2 +type forwardedTCPPayload struct { + Addr string + Port uint32 + OriginAddr string + OriginPort uint32 +} + +// parseTCPAddr parses the originating address from the remote into a *net.TCPAddr. +func parseTCPAddr(addr string, port uint32) (*net.TCPAddr, error) { + if port == 0 || port > 65535 { + return nil, fmt.Errorf("ssh: port number out of range: %d", port) + } + ip := net.ParseIP(string(addr)) + if ip == nil { + return nil, fmt.Errorf("ssh: cannot parse IP address %q", addr) + } + return &net.TCPAddr{IP: ip, Port: int(port)}, nil +} + +func (l *forwardList) handleChannels(in <-chan NewChannel) { + for ch := range in { + var ( + laddr net.Addr + raddr net.Addr + err error + ) + switch channelType := ch.ChannelType(); channelType { + case "forwarded-tcpip": + var payload forwardedTCPPayload + if err = Unmarshal(ch.ExtraData(), &payload); err != nil { + ch.Reject(ConnectionFailed, "could not parse forwarded-tcpip payload: "+err.Error()) + continue + } + + // RFC 4254 section 7.2 specifies that incoming + // addresses should list the address, in string + // format. It is implied that this should be an IP + // address, as it would be impossible to connect to it + // otherwise. + laddr, err = parseTCPAddr(payload.Addr, payload.Port) + if err != nil { + ch.Reject(ConnectionFailed, err.Error()) + continue + } + raddr, err = parseTCPAddr(payload.OriginAddr, payload.OriginPort) + if err != nil { + ch.Reject(ConnectionFailed, err.Error()) + continue + } + + case "forwarded-streamlocal@openssh.com": + var payload forwardedStreamLocalPayload + if err = Unmarshal(ch.ExtraData(), &payload); err != nil { + ch.Reject(ConnectionFailed, "could not parse forwarded-streamlocal@openssh.com payload: "+err.Error()) + continue + } + laddr = &net.UnixAddr{ + Name: payload.SocketPath, + Net: "unix", + } + raddr = &net.UnixAddr{ + Name: "@", + Net: "unix", + } + default: + panic(fmt.Errorf("ssh: unknown channel type %s", channelType)) + } + if ok := l.forward(laddr, raddr, ch); !ok { + // Section 7.2, implementations MUST reject spurious incoming + // connections. + ch.Reject(Prohibited, "no forward for address") + continue + } + + } +} + +// remove removes the forward entry, and the channel feeding its +// listener. +func (l *forwardList) remove(addr net.Addr) { + l.Lock() + defer l.Unlock() + for i, f := range l.entries { + if addr.Network() == f.laddr.Network() && addr.String() == f.laddr.String() { + l.entries = append(l.entries[:i], l.entries[i+1:]...) + close(f.c) + return + } + } +} + +// closeAll closes and clears all forwards. +func (l *forwardList) closeAll() { + l.Lock() + defer l.Unlock() + for _, f := range l.entries { + close(f.c) + } + l.entries = nil +} + +func (l *forwardList) forward(laddr, raddr net.Addr, ch NewChannel) bool { + l.Lock() + defer l.Unlock() + for _, f := range l.entries { + if laddr.Network() == f.laddr.Network() && laddr.String() == f.laddr.String() { + f.c <- forward{newCh: ch, raddr: raddr} + return true + } + } + return false +} + +type tcpListener struct { + laddr *net.TCPAddr + + conn *Client + in <-chan forward +} + +// Accept waits for and returns the next connection to the listener. +func (l *tcpListener) Accept() (net.Conn, error) { + s, ok := <-l.in + if !ok { + return nil, io.EOF + } + ch, incoming, err := s.newCh.Accept() + if err != nil { + return nil, err + } + go DiscardRequests(incoming) + + return &chanConn{ + Channel: ch, + laddr: l.laddr, + raddr: s.raddr, + }, nil +} + +// Close closes the listener. +func (l *tcpListener) Close() error { + m := channelForwardMsg{ + l.laddr.IP.String(), + uint32(l.laddr.Port), + } + + // this also closes the listener. + l.conn.forwards.remove(l.laddr) + ok, _, err := l.conn.SendRequest("cancel-tcpip-forward", true, Marshal(&m)) + if err == nil && !ok { + err = errors.New("ssh: cancel-tcpip-forward failed") + } + return err +} + +// Addr returns the listener's network address. +func (l *tcpListener) Addr() net.Addr { + return l.laddr +} + +// Dial initiates a connection to the addr from the remote host. +// The resulting connection has a zero LocalAddr() and RemoteAddr(). +func (c *Client) Dial(n, addr string) (net.Conn, error) { + var ch Channel + switch n { + case "tcp", "tcp4", "tcp6": + // Parse the address into host and numeric port. + host, portString, err := net.SplitHostPort(addr) + if err != nil { + return nil, err + } + port, err := strconv.ParseUint(portString, 10, 16) + if err != nil { + return nil, err + } + ch, err = c.dial(net.IPv4zero.String(), 0, host, int(port)) + if err != nil { + return nil, err + } + // Use a zero address for local and remote address. + zeroAddr := &net.TCPAddr{ + IP: net.IPv4zero, + Port: 0, + } + return &chanConn{ + Channel: ch, + laddr: zeroAddr, + raddr: zeroAddr, + }, nil + case "unix": + var err error + ch, err = c.dialStreamLocal(addr) + if err != nil { + return nil, err + } + return &chanConn{ + Channel: ch, + laddr: &net.UnixAddr{ + Name: "@", + Net: "unix", + }, + raddr: &net.UnixAddr{ + Name: addr, + Net: "unix", + }, + }, nil + default: + return nil, fmt.Errorf("ssh: unsupported protocol: %s", n) + } +} + +// DialTCP connects to the remote address raddr on the network net, +// which must be "tcp", "tcp4", or "tcp6". If laddr is not nil, it is used +// as the local address for the connection. +func (c *Client) DialTCP(n string, laddr, raddr *net.TCPAddr) (net.Conn, error) { + if laddr == nil { + laddr = &net.TCPAddr{ + IP: net.IPv4zero, + Port: 0, + } + } + ch, err := c.dial(laddr.IP.String(), laddr.Port, raddr.IP.String(), raddr.Port) + if err != nil { + return nil, err + } + return &chanConn{ + Channel: ch, + laddr: laddr, + raddr: raddr, + }, nil +} + +// RFC 4254 7.2 +type channelOpenDirectMsg struct { + raddr string + rport uint32 + laddr string + lport uint32 +} + +func (c *Client) dial(laddr string, lport int, raddr string, rport int) (Channel, error) { + msg := channelOpenDirectMsg{ + raddr: raddr, + rport: uint32(rport), + laddr: laddr, + lport: uint32(lport), + } + ch, in, err := c.OpenChannel("direct-tcpip", Marshal(&msg)) + if err != nil { + return nil, err + } + go DiscardRequests(in) + return ch, err +} + +type tcpChan struct { + Channel // the backing channel +} + +// chanConn fulfills the net.Conn interface without +// the tcpChan having to hold laddr or raddr directly. +type chanConn struct { + Channel + laddr, raddr net.Addr +} + +// LocalAddr returns the local network address. +func (t *chanConn) LocalAddr() net.Addr { + return t.laddr +} + +// RemoteAddr returns the remote network address. +func (t *chanConn) RemoteAddr() net.Addr { + return t.raddr +} + +// SetDeadline sets the read and write deadlines associated +// with the connection. +func (t *chanConn) SetDeadline(deadline time.Time) error { + if err := t.SetReadDeadline(deadline); err != nil { + return err + } + return t.SetWriteDeadline(deadline) +} + +// SetReadDeadline sets the read deadline. +// A zero value for t means Read will not time out. +// After the deadline, the error from Read will implement net.Error +// with Timeout() == true. +func (t *chanConn) SetReadDeadline(deadline time.Time) error { + // for compatibility with previous version, + // the error message contains "tcpChan" + return errors.New("ssh: tcpChan: deadline not supported") +} + +// SetWriteDeadline exists to satisfy the net.Conn interface +// but is not implemented by this type. It always returns an error. +func (t *chanConn) SetWriteDeadline(deadline time.Time) error { + return errors.New("ssh: tcpChan: deadline not supported") +} diff --git a/pkg/proto/ssh/terminal/terminal.go b/pkg/proto/ssh/terminal/terminal.go new file mode 100644 index 0000000..a4d1919 --- /dev/null +++ b/pkg/proto/ssh/terminal/terminal.go @@ -0,0 +1,76 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package terminal provides support functions for dealing with terminals, as +// commonly found on UNIX systems. +// +// Deprecated: this package moved to golang.org/x/term. +package terminal + +import ( + "io" + + "golang.org/x/term" +) + +// EscapeCodes contains escape sequences that can be written to the terminal in +// order to achieve different styles of text. +type EscapeCodes = term.EscapeCodes + +// Terminal contains the state for running a VT100 terminal that is capable of +// reading lines of input. +type Terminal = term.Terminal + +// NewTerminal runs a VT100 terminal on the given ReadWriter. If the ReadWriter is +// a local terminal, that terminal must first have been put into raw mode. +// prompt is a string that is written at the start of each input line (i.e. +// "> "). +func NewTerminal(c io.ReadWriter, prompt string) *Terminal { + return term.NewTerminal(c, prompt) +} + +// ErrPasteIndicator may be returned from ReadLine as the error, in addition +// to valid line data. It indicates that bracketed paste mode is enabled and +// that the returned line consists only of pasted data. Programs may wish to +// interpret pasted data more literally than typed data. +var ErrPasteIndicator = term.ErrPasteIndicator + +// State contains the state of a terminal. +type State = term.State + +// IsTerminal returns whether the given file descriptor is a terminal. +func IsTerminal(fd int) bool { + return term.IsTerminal(fd) +} + +// ReadPassword reads a line of input from a terminal without local echo. This +// is commonly used for inputting passwords and other sensitive data. The slice +// returned does not include the \n. +func ReadPassword(fd int) ([]byte, error) { + return term.ReadPassword(fd) +} + +// MakeRaw puts the terminal connected to the given file descriptor into raw +// mode and returns the previous state of the terminal so that it can be +// restored. +func MakeRaw(fd int) (*State, error) { + return term.MakeRaw(fd) +} + +// Restore restores the terminal connected to the given file descriptor to a +// previous state. +func Restore(fd int, oldState *State) error { + return term.Restore(fd, oldState) +} + +// GetState returns the current state of a terminal which may be useful to +// restore the terminal after a signal. +func GetState(fd int) (*State, error) { + return term.GetState(fd) +} + +// GetSize returns the dimensions of the given terminal. +func GetSize(fd int) (width, height int, err error) { + return term.GetSize(fd) +} diff --git a/pkg/proto/ssh/transport.go b/pkg/proto/ssh/transport.go new file mode 100644 index 0000000..da01580 --- /dev/null +++ b/pkg/proto/ssh/transport.go @@ -0,0 +1,358 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ssh + +import ( + "bufio" + "bytes" + "errors" + "io" + "log" +) + +// debugTransport if set, will print packet types as they go over the +// wire. No message decoding is done, to minimize the impact on timing. +const debugTransport = false + +const ( + gcm128CipherID = "aes128-gcm@openssh.com" + gcm256CipherID = "aes256-gcm@openssh.com" + aes128cbcID = "aes128-cbc" + tripledescbcID = "3des-cbc" +) + +// packetConn represents a transport that implements packet based +// operations. +type packetConn interface { + // Encrypt and send a packet of data to the remote peer. + writePacket(packet []byte) error + + // Read a packet from the connection. The read is blocking, + // i.e. if error is nil, then the returned byte slice is + // always non-empty. + readPacket() ([]byte, error) + + // Close closes the write-side of the connection. + Close() error +} + +// transport is the keyingTransport that implements the SSH packet +// protocol. +type transport struct { + reader connectionState + writer connectionState + + bufReader *bufio.Reader + bufWriter *bufio.Writer + rand io.Reader + isClient bool + io.Closer +} + +// packetCipher represents a combination of SSH encryption/MAC +// protocol. A single instance should be used for one direction only. +type packetCipher interface { + // writeCipherPacket encrypts the packet and writes it to w. The + // contents of the packet are generally scrambled. + writeCipherPacket(seqnum uint32, w io.Writer, rand io.Reader, packet []byte) error + + // readCipherPacket reads and decrypts a packet of data. The + // returned packet may be overwritten by future calls of + // readPacket. + readCipherPacket(seqnum uint32, r io.Reader) ([]byte, error) +} + +// connectionState represents one side (read or write) of the +// connection. This is necessary because each direction has its own +// keys, and can even have its own algorithms +type connectionState struct { + packetCipher + seqNum uint32 + dir direction + pendingKeyChange chan packetCipher +} + +// prepareKeyChange sets up key material for a keychange. The key changes in +// both directions are triggered by reading and writing a msgNewKey packet +// respectively. +func (t *transport) prepareKeyChange(algs *algorithms, kexResult *kexResult) error { + ciph, err := newPacketCipher(t.reader.dir, algs.r, kexResult) + if err != nil { + return err + } + t.reader.pendingKeyChange <- ciph + + ciph, err = newPacketCipher(t.writer.dir, algs.w, kexResult) + if err != nil { + return err + } + t.writer.pendingKeyChange <- ciph + + return nil +} + +func (t *transport) printPacket(p []byte, write bool) { + if len(p) == 0 { + return + } + who := "server" + if t.isClient { + who = "client" + } + what := "read" + if write { + what = "write" + } + + log.Println(what, who, p[0]) +} + +// Read and decrypt next packet. +func (t *transport) readPacket() (p []byte, err error) { + for { + p, err = t.reader.readPacket(t.bufReader) + if err != nil { + break + } + if len(p) == 0 || (p[0] != msgIgnore && p[0] != msgDebug) { + break + } + } + if debugTransport { + t.printPacket(p, false) + } + + return p, err +} + +func (s *connectionState) readPacket(r *bufio.Reader) ([]byte, error) { + packet, err := s.packetCipher.readCipherPacket(s.seqNum, r) + s.seqNum++ + if err == nil && len(packet) == 0 { + err = errors.New("ssh: zero length packet") + } + + if len(packet) > 0 { + switch packet[0] { + case msgNewKeys: + select { + case cipher := <-s.pendingKeyChange: + s.packetCipher = cipher + default: + return nil, errors.New("ssh: got bogus newkeys message") + } + + case msgDisconnect: + // Transform a disconnect message into an + // error. Since this is lowest level at which + // we interpret message types, doing it here + // ensures that we don't have to handle it + // elsewhere. + var msg disconnectMsg + if err := Unmarshal(packet, &msg); err != nil { + return nil, err + } + return nil, &msg + } + } + + // The packet may point to an internal buffer, so copy the + // packet out here. + fresh := make([]byte, len(packet)) + copy(fresh, packet) + + return fresh, err +} + +func (t *transport) writePacket(packet []byte) error { + if debugTransport { + t.printPacket(packet, true) + } + return t.writer.writePacket(t.bufWriter, t.rand, packet) +} + +func (s *connectionState) writePacket(w *bufio.Writer, rand io.Reader, packet []byte) error { + changeKeys := len(packet) > 0 && packet[0] == msgNewKeys + + err := s.packetCipher.writeCipherPacket(s.seqNum, w, rand, packet) + if err != nil { + return err + } + if err = w.Flush(); err != nil { + return err + } + s.seqNum++ + if changeKeys { + select { + case cipher := <-s.pendingKeyChange: + s.packetCipher = cipher + default: + panic("ssh: no key material for msgNewKeys") + } + } + return err +} + +func newTransport(rwc io.ReadWriteCloser, rand io.Reader, isClient bool) *transport { + t := &transport{ + bufReader: bufio.NewReader(rwc), + bufWriter: bufio.NewWriter(rwc), + rand: rand, + reader: connectionState{ + packetCipher: &streamPacketCipher{cipher: noneCipher{}}, + pendingKeyChange: make(chan packetCipher, 1), + }, + writer: connectionState{ + packetCipher: &streamPacketCipher{cipher: noneCipher{}}, + pendingKeyChange: make(chan packetCipher, 1), + }, + Closer: rwc, + } + t.isClient = isClient + + if isClient { + t.reader.dir = serverKeys + t.writer.dir = clientKeys + } else { + t.reader.dir = clientKeys + t.writer.dir = serverKeys + } + + return t +} + +type direction struct { + ivTag []byte + keyTag []byte + macKeyTag []byte +} + +var ( + serverKeys = direction{[]byte{'B'}, []byte{'D'}, []byte{'F'}} + clientKeys = direction{[]byte{'A'}, []byte{'C'}, []byte{'E'}} +) + +// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as +// described in RFC 4253, section 6.4. direction should either be serverKeys +// (to setup server->client keys) or clientKeys (for client->server keys). +func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) { + cipherMode := cipherModes[algs.Cipher] + + iv := make([]byte, cipherMode.ivSize) + key := make([]byte, cipherMode.keySize) + + generateKeyMaterial(iv, d.ivTag, kex) + generateKeyMaterial(key, d.keyTag, kex) + + var macKey []byte + if !aeadCiphers[algs.Cipher] { + macMode := macModes[algs.MAC] + macKey = make([]byte, macMode.keySize) + generateKeyMaterial(macKey, d.macKeyTag, kex) + } + + return cipherModes[algs.Cipher].create(key, iv, macKey, algs) +} + +// generateKeyMaterial fills out with key material generated from tag, K, H +// and sessionId, as specified in RFC 4253, section 7.2. +func generateKeyMaterial(out, tag []byte, r *kexResult) { + var digestsSoFar []byte + + h := r.Hash.New() + for len(out) > 0 { + h.Reset() + h.Write(r.K) + h.Write(r.H) + + if len(digestsSoFar) == 0 { + h.Write(tag) + h.Write(r.SessionID) + } else { + h.Write(digestsSoFar) + } + + digest := h.Sum(nil) + n := copy(out, digest) + out = out[n:] + if len(out) > 0 { + digestsSoFar = append(digestsSoFar, digest...) + } + } +} + +const packageVersion = "SSH-2.0-Go" + +// Sends and receives a version line. The versionLine string should +// be US ASCII, start with "SSH-2.0-", and should not include a +// newline. exchangeVersions returns the other side's version line. +func exchangeVersions(rw io.ReadWriter, versionLine []byte) (them []byte, err error) { + // Contrary to the RFC, we do not ignore lines that don't + // start with "SSH-2.0-" to make the library usable with + // nonconforming servers. + for _, c := range versionLine { + // The spec disallows non US-ASCII chars, and + // specifically forbids null chars. + if c < 32 { + return nil, errors.New("ssh: junk character in version line") + } + } + if _, err = rw.Write(append(versionLine, '\r', '\n')); err != nil { + return + } + + them, err = readVersion(rw) + return them, err +} + +// maxVersionStringBytes is the maximum number of bytes that we'll +// accept as a version string. RFC 4253 section 4.2 limits this at 255 +// chars +const maxVersionStringBytes = 255 + +// Read version string as specified by RFC 4253, section 4.2. +func readVersion(r io.Reader) ([]byte, error) { + versionString := make([]byte, 0, 64) + var ok bool + var buf [1]byte + + for length := 0; length < maxVersionStringBytes; length++ { + _, err := io.ReadFull(r, buf[:]) + if err != nil { + return nil, err + } + // The RFC says that the version should be terminated with \r\n + // but several SSH servers actually only send a \n. + if buf[0] == '\n' { + if !bytes.HasPrefix(versionString, []byte("SSH-")) { + // RFC 4253 says we need to ignore all version string lines + // except the one containing the SSH version (provided that + // all the lines do not exceed 255 bytes in total). + versionString = versionString[:0] + continue + } + ok = true + break + } + + // non ASCII chars are disallowed, but we are lenient, + // since Go doesn't use null-terminated strings. + + // The RFC allows a comment after a space, however, + // all of it (version and comments) goes into the + // session hash. + versionString = append(versionString, buf[0]) + } + + if !ok { + return nil, errors.New("ssh: overflow reading version string") + } + + // There might be a '\r' on the end which we should remove. + if len(versionString) > 0 && versionString[len(versionString)-1] == '\r' { + versionString = versionString[:len(versionString)-1] + } + return versionString, nil +}