chromeos-base/chromeos-sshd-init/files/sshd-pre

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

SSH_DIR=/mnt/stateful_partition/etc/ssh
mkdir -p "${SSH_DIR}"

if ! sshd -t -q ; then
  # sshd will not start with current config, generate a new set of keys.
  for KEY_TYPE in rsa ed25519 ; do
    KEY_FILE="${SSH_DIR}/ssh_host_${KEY_TYPE}_key"
    # If keys exist delete them because they are not valid and ssh-keygen
    # will not overwrite them.
    rm -f "${KEY_FILE}" "${KEY_FILE}.pub"
    ssh-keygen -q -f "${KEY_FILE}" -N '' -t ${KEY_TYPE} ||
      logger -t "${UPSTART_JOB}" "Failed to generate ssh key."
  done
fi

for cmd in iptables ip6tables ; do
  $cmd -A INPUT -p tcp --dport 22 -j ACCEPT -w ||
    logger -t "${UPSTART_JOB}" "Failed to configure $cmd."
done