#!/bin/sh

# SPDX-FileCopyrightText: 2017 Jean-Philippe Ouellet <jpo@vt.edu>
# SPDX-FileCopyrightText: 2022 daktak <daktak@gmail.com>
# SPDX-FileCopyrightText: 2023 Frederic Pierret <frederic.pierret@qubes-os.org>
# SPDX-FileCopyrightText: 2024 Benjamin Grande M. S. <ben.grande.b@gmail.com>
#
# SPDX-License-Identifier: MIT
#
# Credits: https://gist.github.com/daktak/f887352d564b54f9e529404cc0eb60d5
# Credits: https://gist.github.com/jpouellet/d8cd0eb8589a5b9bf0c53a28fc530369
# Credits: https://gist.github.com/fepitre/941d7161ae1150d90e15f778027e3248

set -eu

run_qube(){
  qube="${1}"
  shift
  qvm-run --pass-io --user=root "${qube}" -- "${@}"
}

create_net_dir(){
  qube="${1}"
  run_qube "${qube}" mkdir -p "${hook_dir}"
}

validate_handle(){
  qube="${1}"
  untrusted_handle="${2}"
  case "${untrusted_handle}" in
    ""|*[!0-9]*)
      echo "error: ${qube}: invalid handle" >&2
      exit 1
      ;;
    *) ;;
  esac
}

validate_ipv4(){
  qube="${1}"
  untrusted_ip="${2}"
  case "${untrusted_ip}" in
    ""|*[!0-9./]*)
      echo "error: ${qube}: invalid IPv4 address" >&2
      exit 1
      ;;
    *) ;;
  esac
}

validate_ipv6(){
  qube="${1}"
  untrusted_ip="${2}"
  case "${untrusted_ip}" in
    ""|*[!0-9a-f:/]*)
      echo "error: ${qube}: invalid IPv6 address" >&2
      exit 1
      ;;
    *) ;;
  esac
}

validate_dev(){
  qube="${1}"
  untrusted_dev="${2}"
  case "${untrusted_dev}" in
    ""|*[!0-9A-Za-z]*)
      echo "error: ${qube}: invalid device name" >&2
      exit 1
      ;;
    *) ;;
  esac
}

get_rule_handle(){
  qube="${1}"
  chain="${2}"
  rule="${3}"
  run_qube "${qube}" \
    "nft --handle --stateless list chain ip qubes ${chain} |
    tr -d '\"' | grep '^\s\+${rule} # handle ' | awk '{print \$NF}' |
    tr '\n' ' '" 2>/dev/null
}

delete_rule_handle(){
  qube="${1}"
  chain="${2}"
  handle="${3}"
  run_qube "${qube}" "nft delete rule ip qubes ${chain} handle ${handle}"
}

delete_rule(){
  qube="${1}"
  chain="${2}"
  rule="${3}"
  untrusted_handle_list="$(get_rule_handle "${qube}" "${chain}" "${rule}")"
  if test -n "${untrusted_handle_list}"; then
    for untrusted_handle in ${untrusted_handle_list}; do
      unset handle
      validate_handle "${qube}" "${untrusted_handle}"
      handle="${untrusted_handle}"
      delete_rule_handle "${qube}" "${chain}" "${handle}"
    done
  fi
}

forward() {
  from_qube="${1}"
  to_qube="${2}"
  create_net_dir "${from_qube}"

  unset dev
  ## TODO: Handle multiple interfaces in upstream.
  untrusted_dev="$(run_qube "${from_qube}" ip -4 route | \
                    awk '/^default via /{print $5}' | head -1)"
  validate_dev "${from_qube}" "${untrusted_dev}"
  dev="${untrusted_dev}"

  unset from_ip
  untrusted_from_ip="$(run_qube "${from_qube}" ip -4 -o addr show dev \
                        "${dev}" | awk '{print $4}' | cut -d "/" -f 1)"
  validate_ipv4 "${from_qube}" "${untrusted_from_ip}"
  from_ip="${untrusted_from_ip}"

  to_ip="$(qvm-prefs --get -- "${to_qube}" ip)"
  to_ip_escaped="$(echo "${to_ip}" | tr "." "-")"
  hook="${hook_prefix}${to_ip}-${proto}-${port}.sh"

  if test "${from_ip}" = "None"; then
    from_ip=""
  fi

  dnat_chain="custom-pf-${to_ip_escaped}"
  dnat_rule="iifname ${dev} ip saddr ${lan_ip} ${proto} dport ${port} ct"
  dnat_rule="${dnat_rule} state established,related,new counter dnat to"
  dnat_rule="${dnat_rule} ${to_ip}"
  forward_chain="custom-forward"
  forward_rule="iifname ${dev} ip saddr ${lan_ip} ip daddr ${to_ip} ${proto}"
  forward_rule="${forward_rule} dport ${port} ct state"
  forward_rule="${forward_rule} established,related,new counter accept"
  dnat_policy="type nat hook prerouting priority filter +1; policy accept;"
  dnat_policy="{ ${dnat_policy} }"
  full_rule="nft 'add chain ip qubes ${dnat_chain} ${dnat_policy}
add rule ip qubes ${dnat_chain} ${dnat_rule}
add rule ip qubes ${forward_chain} ${forward_rule}'"

  delete_rule "${from_qube}" "${forward_chain}" "${forward_rule}"
  delete_rule "${from_qube}" "${dnat_chain}" "${dnat_rule}"
  if test "${action}" = "del"; then
    echo "info: ${from_qube}: deleting rules" >&2
    run_qube "${from_qube}" "rm -f ${hook}"
  else
    msg="adding forward rule dev ${dev} saddr ${lan_ip} daddr ${to_ip}"
    echo "info: ${from_qube}: ${msg}" >&2
    run_qube "${from_qube}" "${full_rule}"

    if test "${persistent}" = "1"; then
      class="$(qvm-prefs --get -- "${from_qube}" klass)"
      if test "${class}" = "DispVM"; then
        from_qube="$(qvm-prefs --get -- "${from_qube}" template)"
      fi

      full_rule="#!/bin/sh
get_handle(){
  chain=\\\${1}
  rule=\\\${2}
  nft --handle --stateless list chain ip qubes \\\${chain} | \\\
    tr -d '\\\"' | grep '^\\\s\\\+\\\${rule} \\# handle ' | \\\
    awk '{print \\\$NF}' | tr \\\"\\\n\\\" \\\" \\\"
}

forward_handle=\\\$(get_handle ${forward_chain} \\\"${forward_rule}\\\")
if test -n \\\"\\\${forward_handle:-}\\\"; then
  for h in \\\${forward_handle}; do
    nft delete rule ip qubes ${forward_chain} handle \\\${h}
  done
fi

dnat_handle=\\\$(get_handle ${dnat_chain} \\\"${dnat_rule}\\\")
if test -n \\\"\\\${dnat_handle:-}\\\"; then
  for h in \\\${dnat_handle}; do
    nft delete rule ip qubes ${dnat_chain} handle \\\${h}
  done
fi

${full_rule}"

      create_net_dir "${from_qube}"
      run_qube "${from_qube}" \
        "echo \"${full_rule}\" | tee \"${hook}\" >/dev/null"
      run_qube "${from_qube}" "chmod +x ${hook}"
    fi
  fi
}

input() {
  qube="${1}"
  to_ip="$(qvm-prefs --get -- "${qube}" ip)"
  hook="${hook_prefix}${to_ip}-${proto}-${port}.sh"
  create_net_dir "${qube}"

  custom_input_rule="${proto} dport ${port} ip daddr ${to_ip} ct state new"
  custom_input_rule="${custom_input_rule} counter accept"
  input_rule="nft add rule ip qubes custom-input ${custom_input_rule}"

  delete_rule "${qube}" "custom-input" "${custom_input_rule}"
  if test "${action}" = "del"; then
    echo "info: ${qube}: deleting rules" >&2
    run_qube "${qube}" "rm -f ${hook}"
  else
    echo "info: ${qube}: adding input rule daddr ${to_ip}" >&2
    run_qube "${qube}" "${input_rule}"
    if test "${persistent}" = "1"; then
      input_rule="#!/bin/sh
get_handle(){
  chain=\\\${1}
  rule=\\\${2}
  nft --handle --stateless list chain ip qubes \\\${chain} | \\\
    tr -d '\\\"' | grep '^\\\s\\\+\\\${rule} \\# handle ' | \\\
    awk '{print \\\$NF}' | tr \\\"\\\n\\\" \\\" \\\"
}

input_handle=\\\$(get_handle custom-input \\\"${custom_input_rule}\\\")
if test -n \\\"\\\${input_handle:-}\\\"; then
  for h in \\\${input_handle}; do
    nft delete rule ip qubes custom-input handle \\\${h}
  done
fi

${input_rule}"

      run_qube "${qube}" "echo \"${input_rule}\" | tee \"${hook}\" >/dev/null"
      run_qube "${qube}" "chmod +x ${hook}"
    fi
  fi
}

get_lan(){
  qube="${1}"

  unset dev
  ## TODO: Handle multiple interfaces in upstream.
  untrusted_dev="$(run_qube "${qube}" ip -4 route | \
                    awk '/^default via /{print $5}' | head -1)"
  validate_dev "${qube}" "${untrusted_dev}"
  dev="${untrusted_dev}"

  if test -z "${dev}"; then
    echo "error: ${qube}: could not find any device that is up" >&2
    exit 1
  fi

  unset lan_ip
  untrusted_lan_ip="$(run_qube "${qube}" ip -4 route show dev "${dev}" \
                      prot kernel | cut -d " " -f 1)"
  validate_ipv4 "${qube}" "${untrusted_lan_ip}"
  lan_ip="${untrusted_lan_ip}"

  if test -z "${lan_ip}"; then
    echo "error: ${qube}: could not find LAN from device ${dev}" >&2
    exit 1
  fi
}

test_qvm_run(){
  qube="${1}"
  # shellcheck disable=SC2310
  if ! run_qube "${qube}" echo "Test QUBESRPC" >/dev/null 2>&1; then
    echo "error: ${qube}: RPC qubes.VMShell failed, use a different qube" >&2
    exit 1
  fi
}

recurse_netvms() {
  cmd="${1}"
  rec_qube="${2}"
  rec_netvm="$(qvm-prefs --get -- "${rec_qube}" netvm)"
  if test -n "${rec_netvm}" && test "${rec_netvm}" != "None"; then
    case "${cmd}" in
      show-upstream) test_qvm_run "${rec_qube}";;
      apply-rules) forward "${rec_netvm}" "${rec_qube}";;
      *) echo "Unsupported command passed to recurse_netvms()" >&2; exit 1;;
    esac
    recurse_netvms "${cmd}" "${rec_netvm}"
  fi
  case "${cmd}" in
    show-upstream) get_lan "${rec_qube}";;
    apply-rules) ;;
    *) echo "Unsupported command passed to recurse_netvms()" >&2; exit 1;;
  esac
}

usage() {
  echo "Usage: ${0##*/} OPTIONS
Option syntax:
  --action ACTION --qube QUBE --port PORT --proto PROTO [--persistent]
Options:
  -a, --action ACTION        add or delete a rule (add, del)
  -q, --qube QUBE            qube name which holds the service to be exposed
  -p, --port PORT            port number to be exposed
  -n, --proto PROTO          protocol the service uses (tcp, udp)
  -s, --persistent           persist rules across reboots
Example:
  ${0##*/} --action add --qube work --port 22 --proto tcp
  ${0##*/} --action add --qube work --port 444 --proto udp --persistent
  ${0##*/} --action del --qube work --port 22 --proto tcp
  ${0##*/} --action del --qube work --port 444 --proto udp
Note: Defaults to temporary rules
Warn: Persistent rules of disposable netvm are saved to its template" >&2
  exit 1
}

check_opt(){
  case "${action:-}" in
    add|del);;
    *) echo "error: action must be either 'add' or 'del'" >&2; exit 1;;
  esac

  case "${proto:-}" in
    tcp|udp);;
    *) echo "error: protocol must be only 'tcp' or 'udp'" >&2; exit 1;;
  esac

  case "${port:-}" in
    ""|*[!0-9]*) echo "error: port must be only numbers" >&2; exit 1;;
    *)
  esac

  if test "${port}" -ge 1 && test "${port}" -le 65535; then
    true
  else
    echo "error: port must be in range 1-65535" >&2
    exit 1
  fi

  if test -z "${target_qube:-}"; then
    echo "error: qube name not provided" >&2
    exit 1
  fi

  if ! qvm-check -- "${target_qube}" >/dev/null 2>&1; then
    echo "error: qube '${target_qube}' not found." >&2
    exit 1
  fi
}

hook_dir="/rw/config/network-hooks.d"
hook_prefix="${hook_dir}/90-port-forward-"
persistent=""

if ! OPTS=$(getopt -o h,a:q:p:n:s \
  --long help,action:,qube:,port:,proto:,persistent -n "${0}" -- "${@}")
then
  echo "An error occurred while parsing options." >&2
  exit 1
fi

eval set -- "${OPTS}"
if test "${OPTS}" = " --"; then
  usage
fi
while test "${#}" -gt "0"; do
  case "${1}" in
    -a|--action) action="${2}"; shift;;
    -q|--qube) target_qube="${2}"; shift;;
    -p|--port) port="${2}"; shift;;
    -n|--proto) proto="${2}"; shift;;
    -s|--persistent) persistent=1; shift;;
    -h|--help) usage;;
    --) break;;
    *) echo "Unsupported option" >&2; exit 1;;
  esac
  shift
done

check_opt
recurse_netvms show-upstream "${target_qube}"
input "${target_qube}"
recurse_netvms apply-rules "${target_qube}"