// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/dns/fuzzed_host_resolver.h"

#include <stdint.h>

#include <limits>
#include <string>

#include "base/bind.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/single_thread_task_runner.h"
#include "base/test/fuzzed_data_provider.h"
#include "base/threading/thread_task_runner_handle.h"
#include "net/base/address_list.h"
#include "net/base/ip_address.h"
#include "net/base/ip_endpoint.h"
#include "net/base/net_errors.h"
#include "net/dns/dns_client.h"
#include "net/dns/dns_config_service.h"
#include "net/dns/dns_hosts.h"

namespace net {

namespace {

// Returns a fuzzed non-zero port number.
uint16_t FuzzPort(base::FuzzedDataProvider* data_provider) {
  return data_provider->ConsumeUint16();
}

// Returns a fuzzed IPv4 address.  Can return invalid / reserved addresses.
IPAddress FuzzIPv4Address(base::FuzzedDataProvider* data_provider) {
  return IPAddress(data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8());
}

// Returns a fuzzed IPv6 address.  Can return invalid / reserved addresses.
IPAddress FuzzIPv6Address(base::FuzzedDataProvider* data_provider) {
  return IPAddress(data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8(),
                   data_provider->ConsumeUint8());
}

// Returns a fuzzed address, which can be either IPv4 or IPv6.  Can return
// invalid / reserved addresses.
IPAddress FuzzIPAddress(base::FuzzedDataProvider* data_provider) {
  if (data_provider->ConsumeBool())
    return FuzzIPv4Address(data_provider);
  return FuzzIPv6Address(data_provider);
}

// HostResolverProc that returns a random set of results, and can succeed or
// fail. Must only be run on the thread it's created on.
class FuzzedHostResolverProc : public HostResolverProc {
 public:
  // Can safely be used after the destruction of |data_provider|. This can
  // happen if a request is issued but the code never waits for the result
  // before the test ends.
  explicit FuzzedHostResolverProc(
      base::WeakPtr<base::FuzzedDataProvider> data_provider)
      : HostResolverProc(nullptr),
        data_provider_(data_provider),
        network_task_runner_(base::ThreadTaskRunnerHandle::Get()) {}

  int Resolve(const std::string& host,
              AddressFamily address_family,
              HostResolverFlags host_resolver_flags,
              AddressList* addrlist,
              int* os_error) override {
    DCHECK(network_task_runner_->BelongsToCurrentThread());

    if (os_error)
      *os_error = 0;

    // If the data provider is no longer avaiable, just fail. The HostResolver
    // has already been deleted by this point, anyways.
    if (!data_provider_)
      return ERR_FAILED;

    AddressList result;

    // Put IPv6 addresses before IPv4 ones. This code doesn't sort addresses
    // correctly, but when sorted according to spec, IPv6 addresses are
    // generally before IPv4 ones.
    if (address_family == ADDRESS_FAMILY_UNSPECIFIED ||
        address_family == ADDRESS_FAMILY_IPV6) {
      size_t num_ipv6_addresses = data_provider_->ConsumeUint8();
      for (size_t i = 0; i < num_ipv6_addresses; ++i) {
        result.push_back(
            net::IPEndPoint(FuzzIPv6Address(data_provider_.get()), 0));
      }
    }

    if (address_family == ADDRESS_FAMILY_UNSPECIFIED ||
        address_family == ADDRESS_FAMILY_IPV4) {
      size_t num_ipv4_addresses = data_provider_->ConsumeUint8();
      for (size_t i = 0; i < num_ipv4_addresses; ++i) {
        result.push_back(
            net::IPEndPoint(FuzzIPv4Address(data_provider_.get()), 0));
      }
    }

    if (result.empty())
      return ERR_NAME_NOT_RESOLVED;

    if (host_resolver_flags & HOST_RESOLVER_CANONNAME) {
      // Don't bother to fuzz this - almost nothing cares.
      result.set_canonical_name("foo.com");
    }

    *addrlist = result;
    return OK;
  }

 private:
  ~FuzzedHostResolverProc() override = default;

  base::WeakPtr<base::FuzzedDataProvider> data_provider_;

  // Just used for thread-safety checks.
  scoped_refptr<base::SingleThreadTaskRunner> network_task_runner_;

  DISALLOW_COPY_AND_ASSIGN(FuzzedHostResolverProc);
};

}  // namespace

FuzzedHostResolver::FuzzedHostResolver(const Options& options,
                                       NetLog* net_log,
                                       base::FuzzedDataProvider* data_provider)
    : HostResolverImpl(options, net_log),
      data_provider_(data_provider),
      socket_factory_(data_provider),
      is_ipv6_reachable_(data_provider->ConsumeBool()),
      net_log_(net_log),
      data_provider_weak_factory_(data_provider) {
  HostResolverImpl::ProcTaskParams proc_task_params(
      new FuzzedHostResolverProc(data_provider_weak_factory_.GetWeakPtr()),
      // Retries are only used when the original request hangs, which this class
      // currently can't simulate.
      0 /* max_retry_attempts */);
  set_proc_params_for_test(proc_task_params);
  SetTaskRunnerForTesting(base::SequencedTaskRunnerHandle::Get());
}

FuzzedHostResolver::~FuzzedHostResolver() = default;

void FuzzedHostResolver::SetDnsClientEnabled(bool enabled) {
  if (!enabled) {
    HostResolverImpl::SetDnsClientEnabled(false);
    return;
  }

  // Fuzz DNS configuration.

  DnsConfig config;

  // Fuzz name servers.
  uint32_t num_nameservers = data_provider_->ConsumeUint32InRange(0, 4);
  for (uint32_t i = 0; i < num_nameservers; ++i) {
    config.nameservers.push_back(
        IPEndPoint(FuzzIPAddress(data_provider_), FuzzPort(data_provider_)));
  }

  // Fuzz suffix search list. Each case deliberately falls through.
  switch (data_provider_->ConsumeUint32InRange(0, 3)) {
    case 3:
      config.search.push_back("foo.com");
    case 2:
      config.search.push_back("bar");
    case 1:
      config.search.push_back("com");
    default:
      break;
  }

  net::DnsHosts hosts;
  // Fuzz hosts file.
  uint8_t num_hosts_entries = data_provider_->ConsumeUint8();
  for (uint8_t i = 0; i < num_hosts_entries; ++i) {
    const char* kHostnames[] = {"foo", "foo.com",   "a.foo.com",
                                "bar", "localhost", "localhost6"};
    const char* hostname = data_provider_->PickValueInArray(kHostnames);
    net::IPAddress address = FuzzIPAddress(data_provider_);
    config.hosts[net::DnsHostsKey(hostname, net::GetAddressFamily(address))] =
        address;
  }

  config.unhandled_options = data_provider_->ConsumeBool();
  config.append_to_multi_label_name = data_provider_->ConsumeBool();
  config.randomize_ports = data_provider_->ConsumeBool();
  config.ndots = data_provider_->ConsumeInt32InRange(0, 3);
  config.attempts = data_provider_->ConsumeInt32InRange(1, 3);

  // Timeouts don't really work for fuzzing. Even a timeout of 0 milliseconds
  // will be increased after the first timeout, resulting in inconsistent
  // behavior.
  config.timeout = base::TimeDelta::FromDays(10);

  config.rotate = data_provider_->ConsumeBool();

  // Doesn't currently seem to do anything.
  config.edns0 = false;

  config.use_local_ipv6 = data_provider_->ConsumeBool();

  std::unique_ptr<DnsClient> dns_client = DnsClient::CreateClientForTesting(
      net_log_, &socket_factory_,
      base::Bind(&base::FuzzedDataProvider::ConsumeInt32InRange,
                 base::Unretained(data_provider_)));
  dns_client->SetConfig(config);
  SetDnsClient(std::move(dns_client));
}

bool FuzzedHostResolver::IsGloballyReachable(const IPAddress& dest,
                                             const NetLogWithSource& net_log) {
  return is_ipv6_reachable_;
}

void FuzzedHostResolver::RunLoopbackProbeJob() {
  SetHaveOnlyLoopbackAddresses(data_provider_->ConsumeBool());
}

}  // namespace net