Generate throwaway SSH key pairs for automated ... things.

throwaway_ssh_keypair.sh

#!/bin/bash

error () {
  local msg="${1}"

  echo "${msg}"
  exit 1
}

make_tempdir () {
  local dir="${1}"

  # Create a temp dir, and make this user the only owner
  (umask 077 && mkdir -p $dir)

}

create_key () {
  local key_type='rsa'
  local num_bits='4096'
  local out_file="${1}/our_key"
  local comment="${@:2}"

  # Generate without a passphrase
  (umask 077 && ssh-keygen -q -N "" -t $key_type -b $num_bits -f ${out_file} $comment)

}

print_key () {
  local key="$1/our_key"
  local pub="${key}.pub"

  if ! cat $key || ! cat $pub ; then
    return 1
  fi
}

delete_key () {
  local tmp_dir="$1"
  local key="${tmp_dir}/our_key"
  local pub="${key}.pub"

  if ! rm $key || ! rm $pub ; then
    my_error="Unable to delete key pair in ${tmp_dir}/${our_tmp_dir}!"
  fi

}

main () {
  local tmp_dir="/tmp"
  local our_tmp_dir="$(pwgen)"
  
  if [[ ! -z "$1" ]] ; then
    local comment="-C ${1}"
  fi

  make_tempdir "${tmp_dir}/${our_tmp_dir}"
  if ! create_key "${tmp_dir}/${our_tmp_dir}" "${comment}" ; then
    error "Unable to create SSH key"
  fi
  if ! print_key "${tmp_dir}/${our_tmp_dir}" ; then
    echo "Unable to print key(s).  Attempting to delete it, to be safe"
  fi
  # We either printed or did not.  Either way, delete the keys if possible.
  delete_key "${tmp_dir}/${our_tmp_dir}" 

  rmdir $our_tmp_dir
}

main "$@"