fs/skeleton/usr/bin/ssh-manager

#!/bin/sh
# Copyright 2016 Google Inc. All Rights Reserved.
#
# Enable or Disable ssh access.
#
# By default ssh access is disabled but for debugging purposes
# we need to have a way to enable/disable it.

usage()
{
  echo "Usage:"
  echo
  echo "  -h   This help screen"
  echo "  -e   Enable SSH access"
  echo "  -d   Disable SSH access"
}

admin_file="/tmp/ADMINMODE_SSHD"

if_ssh_mounted() {
  if [ ! -z "$(cat /proc/mounts | grep '.ssh')" ]; then
    return 1
  fi
  return 0
}

do_mount() {
  echo "mounting .ssh ..."

  if_ssh_mounted
  if [ $? -ne 0 ]; then
    echo "already mounted"
    exit 1
  fi

  mkdir /tmp/.ssh
  mount --bind /tmp/.ssh /root/.ssh
  if [ $? -ne 0 ]; then
    echo "mounting .ssh failed"
    exit 1
  fi
}

do_unmount() {
  echo "unmounting .ssh ..."
  rm -f /tmp/.ssh/authorized_keys
  if_ssh_mounted
  while [ $? -ne 0 ]; do
    umount /root/.ssh
    if [ $? -ne 0 ]; then
      echo "failed to unmount"
      exit 1
    fi
    if_ssh_mounted
  done
  rm -rf /tmp/.ssh
}

do_enable() {
  echo "enabling ssh ..."
  if [  -f "$admin_file" ]; then
    echo "ssh was enabled already"
    exit 0
  fi

  do_mount
  >$admin_file
  start dropbear
}

do_disable() {
  echo "disabling ssh ..."

  if [ ! -f "$admin_file" ]; then
    echo "ssh was not enabled yet"
    exit 0
  fi

  stop dropbear

  rm -f $admin_file

  do_unmount
}

while getopts ":edh" option
do
  case "$option" in
    e)
      option_found=1 && do_enable
      ;;
    d)
      option_found=1 && do_disable
      ;;
    h)
      option_found=1 && usage
      ;;
    \?|:|*)
      bad_option=1
      ;;
  esac
done

if [ -z "$option_found" ] || [ -n "$bad_option" ]; then
  echo "$0: Unknown options: $@"
  usage
  exit 1
fi