Add IKEv2-only mode script

- New: Helper script to enable or disable IKEv2-only mode

extras/ikev2onlymode.sh

@@ -0,0 +1,178 @@
+#!/bin/bash
+#
+# Script to enable or disable IKEv2-only mode
+#
+# Copyright (C) 2022 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!
+
+export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
+
+exiterr() { echo "Error: $1" >&2; exit 1; }
+bigecho() { echo "## $1"; }
+
+check_root() {
+  if [ "$(id -u)" != 0 ]; then
+    exiterr "Script must be run as root. Try 'sudo bash $0'"
+  fi
+}
+
+abort_and_exit() {
+  echo "Abort. No changes were made." >&2
+  exit 1
+}
+
+confirm_or_abort() {
+  printf '%s' "$1"
+  read -r response
+  case $response in
+    [yY][eE][sS]|[yY])
+      echo
+      ;;
+    *)
+      abort_and_exit
+      ;;
+  esac
+}
+
+check_ikev2_exists() {
+  grep -qs "conn ikev2-cp" /etc/ipsec.conf || [ -f /etc/ipsec.d/ikev2.conf ]
+}
+
+check_libreswan() {
+  ipsec_ver=$(ipsec --version 2>/dev/null)
+  swan_ver=$(printf '%s' "$ipsec_ver" | sed -e 's/.*Libreswan U\?//' -e 's/\( (\|\/K\).*//')
+  if ! grep -qs "hwdsl2 VPN script" /etc/sysctl.conf \
+    || ! grep -qs "config setup" /etc/ipsec.conf \
+    || ! printf '%s' "$ipsec_ver" | grep -q "Libreswan"; then
+cat 1>&2 <<'EOF'
+Error: Your must first set up the IPsec VPN server before selecting IKEv2-only mode.
+       See: https://github.com/hwdsl2/setup-ipsec-vpn
+EOF
+    exit 1
+  fi
+  if ! check_ikev2_exists; then
+cat 1>&2 <<'EOF'
+Error: Your must first set up IKEv2 before selecting IKEv2-only mode.
+       See: https://git.io/ikev2
+EOF
+    exit 1
+  fi
+  case $swan_ver in
+    4.[2-9]|4.[1-9][0-9])
+      true
+      ;;
+    *)
+cat 1>&2 <<EOF
+Error: Libreswan version '$swan_ver' is not supported.
+       IKEv2-only mode requires Libreswan 4.2 or newer.
+       To update Libreswan, run:
+       wget https://git.io/vpnupgrade -O vpnup.sh && sudo sh vpnup.sh
+EOF
+      exit 1
+      ;;
+  esac
+}
+
+get_ikev2_only_status() {
+  if grep -qs "ikev1-policy=drop" /etc/ipsec.conf \
+    || grep -qs "ikev1-policy=reject" /etc/ipsec.conf; then
+    ikev2_only_status=ENABLED
+    option_text="Disable IKEv2-only mode"
+  else
+    ikev2_only_status=DISABLED
+    option_text="Enable IKEv2-only mode"
+  fi
+}
+
+confirm_disable_ikev2_only() {
+cat <<'EOF'
+
+Note: This option will disable IKEv2-only mode on this VPN server. With IKEv2-only
+      mode disabled, VPN clients can connect to this server using IKEv1 (including
+      IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes) in addition to IKEv2.
+
+EOF
+  confirm_or_abort "Do you want to continue? [y/N] "
+}
+
+confirm_enable_ikev2_only() {
+cat <<'EOF'
+
+Note: This option will enable IKEv2-only mode on this VPN server. With IKEv2-only
+      mode enabled, VPN clients can *only* connect to this server using IKEv2.
+      All IKEv1 connections (including IPsec/L2TP and IPsec/XAuth ("Cisco IPsec")
+      modes) will be dropped.
+
+EOF
+  confirm_or_abort "Do you want to continue? [y/N] "
+}
+
+toggle_ikev2_only() {
+  if [ "$ikev2_only_status" = "ENABLED" ]; then
+    confirm_disable_ikev2_only
+    bigecho "Disabling IKEv2-only mode..."
+    sed -i "/ikev1-policy=/d" /etc/ipsec.conf
+  elif [ "$ikev2_only_status" = "DISABLED" ]; then
+    confirm_enable_ikev2_only
+    bigecho "Enabling IKEv2-only mode..."
+    sed -i "/ikev1-policy=/d" /etc/ipsec.conf
+    sed -i "/config setup/a \  ikev1-policy=drop" /etc/ipsec.conf
+  fi
+}
+
+restart_ipsec_service() {
+  bigecho "Restarting IPsec service..."
+  mkdir -p /run/pluto
+  service ipsec restart 2>/dev/null
+}
+
+print_complete() {
+cat <<'EOF'
+Done!
+
+EOF
+}
+
+select_menu_option() {
+cat <<EOF
+
+IKEv2-only mode is currently $ikev2_only_status on this VPN server.
+
+Select an option:
+  1) $option_text
+  2) Exit
+EOF
+  read -rp "Option: " selected_option
+  until [[ "$selected_option" =~ ^[1-2]$ ]]; do
+    printf '%s\n' "$selected_option: invalid selection."
+    read -rp "Option: " selected_option
+  done
+}
+
+ikev2onlymode() {
+  check_root
+  check_libreswan
+  get_ikev2_only_status
+  select_menu_option
+  case $selected_option in
+    1)
+      toggle_ikev2_only
+      restart_ipsec_service
+      print_complete
+      exit 0
+      ;;
+    *)
+      exit 0
+      ;;
+  esac
+}
+
+## Defer until we have the complete script
+ikev2onlymode "$@"
+
+exit 0