make-keytab

#!/usr/bin/env bash

# Copyright (c) 2020 Genome Research Ltd.
#
# Author: Christopher Harrison <ch12@sanger.ac.uk>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

set -euo pipefail

source krb.rc

get_password() {
  # Prompt for user password
  local user="$1"
  local password

  read -srp "Enter Kerberos password for ${user}: " password
  echo "${password}"
}

create_ktutil_script() {
  # Create the ktutil script that creates the Kerberos keytab
  local user="$1"
  local password="$2"
  local krb_realm="$3"
  local keytab="$4"

  for cipher in $(krb_ciphers); do
    echo "addent -password -p ${user}@${krb_realm} -k 1 -e ${cipher}"
    echo "${password}"
  done

  echo "wkt ${keytab}"
  echo "quit"
}

create_keytab() {
  # Create a new Kerberos keytab file for user principal
  local user="$1"
  local password="$2"
  local krb_realm="$3"
  local keytab="${user}.keytab"

  rm -f "${keytab}"
  ktutil < <(create_ktutil_script "${user}" "${password}" "${krb_realm}" "${keytab}") > /dev/null
}

main() {
  local user="${1-$(whoami)}"
  local password="$(get_password "${user}")"
  echo

  create_keytab "${user}" "${password}" "$(krb_realm)"
}

main "$@"