#!/bin/sh
#
# Script for automatic setup of an IPsec VPN server on Ubuntu, Debian,
# CentOS/RHEL, Rocky Linux, AlmaLinux, Amazon Linux 2 and Alpine Linux
# Works on any dedicated server or virtual private server (VPS)
#
# DO NOT RUN THIS SCRIPT ON YOUR PC OR MAC!
#
# The latest version of this script is available at:
# https://github.com/hwdsl2/setup-ipsec-vpn
#
# Copyright (C) 2021 Lin Song <linsongui@gmail.com>
#
# This work is licensed under the Creative Commons Attribution-ShareAlike 3.0
# Unported License: http://creativecommons.org/licenses/by-sa/3.0/
#
# Attribution required: please include my name in any derivative and let me
# know how you have improved it!

# =====================================================

# Define your own values for these variables
# - IPsec pre-shared key, VPN username and password
# - All values MUST be placed inside 'single quotes'
# - DO NOT use these special characters within values: \ " '

YOUR_IPSEC_PSK=''
YOUR_USERNAME=''
YOUR_PASSWORD=''

# Important notes:   https://git.io/vpnnotes
# Setup VPN clients: https://git.io/vpnclients
# IKEv2 guide:       https://git.io/ikev2

# =====================================================

export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

exiterr() { echo "Error: $1" >&2; exit 1; }

check_ip() {
  IP_REGEX='^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$'
  printf '%s' "$1" | tr -d '\n' | grep -Eq "$IP_REGEX"
}

check_root() {
  if [ "$(id -u)" != 0 ]; then
    exiterr "Script must be run as root. Try 'sudo sh $0'"
  fi
}

check_vz() {
  if [ -f /proc/user_beancounters ]; then
    exiterr "OpenVZ VPS is not supported."
  fi
}

check_os() {
  os_type=centos
  rh_file="/etc/redhat-release"
  if grep -qs "Red Hat" "$rh_file"; then
    os_type=rhel
  fi
  if grep -qs "release 7" "$rh_file"; then
    os_ver=7
  elif grep -qs "release 8" "$rh_file"; then
    os_ver=8
    grep -qi stream "$rh_file" && os_ver=8s
    grep -qi rocky "$rh_file" && os_type=rocky
    grep -qi alma "$rh_file" && os_type=alma
  elif grep -qs "Amazon Linux release 2" /etc/system-release; then
    os_type=amzn
    os_ver=2
  else
    os_type=$(lsb_release -si 2>/dev/null)
    [ -z "$os_type" ] && [ -f /etc/os-release ] && os_type=$(. /etc/os-release && printf '%s' "$ID")
    case $os_type in
      [Uu]buntu)
        os_type=ubuntu
        ;;
      [Dd]ebian)
        os_type=debian
        ;;
      [Rr]aspbian)
        os_type=raspbian
        ;;
      [Aa]lpine)
        os_type=alpine
        ;;
      *)
        echo "Error: This script only supports one of the following OS:" >&2
        echo "       Ubuntu, Debian, CentOS/RHEL, Rocky Linux, AlmaLinux," >&2
        echo "       Amazon Linux 2 and Alpine Linux" >&2
        exit 1
        ;;
    esac
    if [ "$os_type" = "alpine" ]; then
      os_ver=$(. /etc/os-release && printf '%s' "$VERSION_ID" | cut -d '.' -f 1,2)
      if [ "$os_ver" != "3.14" ]; then
        exiterr "This script only supports Alpine Linux 3.14."
      fi
    else
      os_ver=$(sed 's/\..*//' /etc/debian_version | tr -dc 'A-Za-z0-9')
      if [ "$os_ver" = "8" ] || [ "$os_ver" = "jessiesid" ]; then
        exiterr "Debian 8 or Ubuntu < 16.04 is not supported."
      fi
      if { [ "$os_ver" = "10" ] || [ "$os_ver" = "11" ]; } && [ ! -e /dev/ppp ]; then
        exiterr "/dev/ppp is missing. Debian 11 or 10 users, see: https://git.io/vpndebian10"
      fi
    fi
  fi
}

check_iface() {
  def_iface=$(route 2>/dev/null | grep -m 1 '^default' | grep -o '[^ ]*$')
  if [ "$os_type" != "alpine" ]; then
    [ -z "$def_iface" ] && def_iface=$(ip -4 route list 0/0 2>/dev/null | grep -m 1 -Po '(?<=dev )(\S+)')
  fi
  def_state=$(cat "/sys/class/net/$def_iface/operstate" 2>/dev/null)
  check_wl=0
  if [ -n "$def_state" ] && [ "$def_state" != "down" ]; then
    if [ "$os_type" = "ubuntu" ] || [ "$os_type" = "debian" ] || [ "$os_type" = "raspbian" ]; then
      if ! uname -m | grep -qi -e '^arm' -e '^aarch64'; then
        check_wl=1
      fi
    else
      check_wl=1
    fi
  fi
  if [ "$check_wl" = "1" ]; then
    case $def_iface in
      wl*)
        exiterr "Wireless interface '$def_iface' detected. DO NOT run this script on your PC or Mac!"
        ;;
    esac
  fi
}

check_creds() {
  [ -n "$YOUR_IPSEC_PSK" ] && VPN_IPSEC_PSK="$YOUR_IPSEC_PSK"
  [ -n "$YOUR_USERNAME" ] && VPN_USER="$YOUR_USERNAME"
  [ -n "$YOUR_PASSWORD" ] && VPN_PASSWORD="$YOUR_PASSWORD"

  if [ -z "$VPN_IPSEC_PSK" ] && [ -z "$VPN_USER" ] && [ -z "$VPN_PASSWORD" ]; then
    return 0
  fi

  if [ -z "$VPN_IPSEC_PSK" ] || [ -z "$VPN_USER" ] || [ -z "$VPN_PASSWORD" ]; then
    exiterr "All VPN credentials must be specified. Edit the script and re-enter them."
  fi

  if printf '%s' "$VPN_IPSEC_PSK $VPN_USER $VPN_PASSWORD" | LC_ALL=C grep -q '[^ -~]\+'; then
    exiterr "VPN credentials must not contain non-ASCII characters."
  fi

  case "$VPN_IPSEC_PSK $VPN_USER $VPN_PASSWORD" in
    *[\\\"\']*)
      exiterr "VPN credentials must not contain these special characters: \\ \" '"
      ;;
  esac
}

check_dns() {
  if { [ -n "$VPN_DNS_SRV1" ] && ! check_ip "$VPN_DNS_SRV1"; } \
    || { [ -n "$VPN_DNS_SRV2" ] && ! check_ip "$VPN_DNS_SRV2"; } then
    exiterr "The DNS server specified is invalid."
  fi
}

check_iptables() {
  if [ "$os_type" = "ubuntu" ] || [ "$os_type" = "debian" ] || [ "$os_type" = "raspbian" ]; then
    if [ -x /sbin/iptables ] && ! iptables -nL INPUT >/dev/null 2>&1; then
      exiterr "IPTables check failed. Reboot and re-run this script."
    fi
  fi
}

wait_for_apt() {
  count=0
  apt_lk=/var/lib/apt/lists/lock
  pkg_lk=/var/lib/dpkg/lock
  while fuser "$apt_lk" "$pkg_lk" >/dev/null 2>&1 \
    || lsof "$apt_lk" >/dev/null 2>&1 || lsof "$pkg_lk" >/dev/null 2>&1; do
    [ "$count" = "0" ] && echo "## Waiting for apt to be available..."
    [ "$count" -ge "100" ] && exiterr "Could not get apt/dpkg lock."
    count=$((count+1))
    printf '%s' '.'
    sleep 3
  done
}

install_pkgs() {
  if ! command -v wget >/dev/null 2>&1; then
    if [ "$os_type" = "ubuntu" ] || [ "$os_type" = "debian" ] || [ "$os_type" = "raspbian" ]; then
      wait_for_apt
      export DEBIAN_FRONTEND=noninteractive
      (
        set -x
        apt-get -yqq update
      ) || exiterr "'apt-get update' failed."
      (
        set -x
        apt-get -yqq install wget >/dev/null
      ) || exiterr "'apt-get install wget' failed."
    elif [ "$os_type" != "alpine" ]; then
      (
        set -x
        yum -y -q install wget >/dev/null
      ) || exiterr "'yum install wget' failed."
    fi
  fi
  if [ "$os_type" = "alpine" ]; then
    (
      set -x
      apk add -U -q bash net-tools wget sed grep
    ) || exiterr "'apk add' failed."
  fi
}

get_setup_url() {
  base_url="https://github.com/hwdsl2/setup-ipsec-vpn/raw/master"
  sh_file="vpnsetup_ubuntu.sh"
  if [ "$os_type" = "centos" ] || [ "$os_type" = "rhel" ] || [ "$os_type" = "rocky" ] || [ "$os_type" = "alma" ]; then
    sh_file="vpnsetup_centos.sh"
  elif [ "$os_type" = "amzn" ]; then
    sh_file="vpnsetup_amzn.sh"
  elif [ "$os_type" = "alpine" ]; then
    sh_file="vpnsetup_alpine.sh"
  fi
  setup_url="$base_url/$sh_file"
}

run_setup() {
  status=0
  if tmpdir=$(mktemp --tmpdir -d vpn.XXXXX 2>/dev/null); then
    if ( set -x; wget -t 3 -T 30 -q -O "$tmpdir/vpn.sh" "$setup_url" \
      || curl -fsL "$setup_url" -o "$tmpdir/vpn.sh" 2>/dev/null ); then
      VPN_IPSEC_PSK="$VPN_IPSEC_PSK" VPN_USER="$VPN_USER" VPN_PASSWORD="$VPN_PASSWORD" \
      VPN_PUBLIC_IP="$VPN_PUBLIC_IP" VPN_L2TP_NET="$VPN_L2TP_NET" \
      VPN_L2TP_LOCAL="$VPN_L2TP_LOCAL" VPN_L2TP_POOL="$VPN_L2TP_POOL" \
      VPN_XAUTH_NET="$VPN_XAUTH_NET" VPN_XAUTH_POOL="$VPN_XAUTH_POOL" \
      VPN_DNS_SRV1="$VPN_DNS_SRV1" VPN_DNS_SRV2="$VPN_DNS_SRV2" \
      /bin/bash "$tmpdir/vpn.sh" || status=1
    else
      status=1
      echo "Error: Could not download VPN setup script." >&2
    fi
    /bin/rm -f "$tmpdir/vpn.sh"
    /bin/rmdir "$tmpdir"
  else
    exiterr "Could not create temporary directory."
  fi
}

vpnsetup() {
  check_root
  check_vz
  check_os
  check_iface
  check_creds
  check_dns
  check_iptables
  install_pkgs
  get_setup_url
  run_setup
}

## Defer setup until we have the complete script
vpnsetup "$@"

exit "$status"