rename-user

#!/bin/bash

# SPDX-FileCopyrightText: 2018 - 2024 sudorook <daemon@nullcodon.com>
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
# 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 <https://www.gnu.org/licenses/>.

set -euo pipefail

ROOT="$(dirname "${0}")"

source "${ROOT}"/globals

! check_command awk find ps sed && exit 3

#
# Functions
#

function migrate_symlink() {
  local symlink
  local sympath
  local newsympath
  symlink="${1}"
  sympath="$(readlink "${symlink}")"
  if [[ "${sympath}" =~ ^/home/${OLDNAME} ]]; then
    newsympath=${sympath/${OLDNAME}/${NEWNAME}/}
    rm "${symlink}"
    ln -s "${newsympath}" "${symlink}"
  fi
}
export -f migrate_symlink

function is_username_valid() {
  local re='^[a-z_][a-z0-9_-]*$'
  [ -z "${1}" ] && return 1
  ((${#1} > 16))   && return 1
  [[ ${1} =~ ${re} ]]
}

function is_old_user_valid() {
  local all_user
  local all_sys
  local uid_min
  local uid_max
  local user="${1}"

  uid_min="$(sed -n "s/^UID_MIN\s\+\([0-9]\+\)$/\1/p" /etc/login.defs)"
  uid_max="$(sed -n "s/^UID_MAX\s\+\([0-9]\+\)$/\1/p" /etc/login.defs)"

  all_sys="$(getent passwd |
             awk -F ":" -v mn="${uid_min}" -v mx="${uid_max}" \
               '{if (($3 < mn) && ($3 > mx)) print $1}')"
  all_user="$(getent passwd |
              awk -F ":" -v mn="${uid_min}" -v mx="${uid_max}" \
                '{if (($3 >= mn) && ($3 <= mx)) print $1}')"

  if [[ "${all_sys}" =~ ${user} ]]; then
    show_warning "${user@Q} is a system user."
    return 1
  fi
  if [[ "${all_user}" =~ ${user} ]]; then
    # Check that old user has no currently running processes.
    if ps -u "${user}" > /dev/null 2>&1; then
      show_warning "User ${user@Q} has running processes."
      return 1
    else
      return 0
    fi
  fi
  return 1
}

function is_new_user_valid() {
  local all_user
  local all_sys
  local uid_min
  local uid_max
  local user="${1}"

  uid_min="$(sed -n "s/^UID_MIN\s\+\([0-9]\+\)$/\1/p" /etc/login.defs)"
  uid_max="$(sed -n "s/^UID_MAX\s\+\([0-9]\+\)$/\1/p" /etc/login.defs)"

  all_sys="$(getent passwd |
             awk -F ":" -v mn="${uid_min}" -v mx="${uid_max}" \
               '{if (($3 < mn) && ($3 > mx)) print $1}')"
  all_user="$(getent passwd |
              awk -F ":" -v mn="${uid_min}" -v mx="${uid_max}" \
                '{if (($3 >= mn) && ($3 <= mx)) print $1}')"

  if [[ "${all_sys}" =~ ${user} ]]; then
    show_warning "${user@Q} is a system user."
    return 1
  fi
  if [[ "${all_user}" =~ ${user} ]]; then
    show_warning "${user@Q} already exists."
    return 1
  fi
  return 0
}

function print_usage() {
  show_header "Usage: rename-user"
  show_listitem "  -n|--new  new username"
  show_listitem "  -o|--old  current username"
}

#
# Parse command line parameters
#

OLDNAME=
NEWNAME=

OPTIONS=ho:n:
LONGOPTIONS=help,old:,new:
PARSED=$(getopt -o "${OPTIONS}" --long "${LONGOPTIONS}" -n "${0}" -- "${@}")
eval set -- "${PARSED}"

while [ ${#} -ge 1 ]; do
  case "${1}" in
    -h | --help)
      print_usage
      exit
      ;;
    -o | --old)
      OLDNAME="${2}"
      shift 2
      ;;
    -n | --new)
      NEWNAME="${2}"
      shift 2
      ;;
    --)
      shift
      break
      ;;
    *)
      show_error "ERROR: invalid input. Exiting."
      exit 3
      ;;
  esac
done

# If the user didn't supply user names via that command line, ask for them in
# the prompt.
if [ -z "${OLDNAME}" ]; then
  OLDNAME=$(ask_question "Change which user name?")
fi
if [ -z "${NEWNAME}" ]; then
  NEWNAME=$(ask_question "What is the new user name?")
fi

# Make sure that OLDNAME and NEWNAME entries are valid.
if ! is_username_valid "${OLDNAME}"; then
  show_error "ERROR: ${OLDNAME@Q} is not a valid name. Exiting."
  exit 3
fi

if ! is_username_valid "${NEWNAME}"; then
  show_error "ERROR: ${NEWNAME@Q} is not a valid name. Exiting."
  exit 3
fi

if ! is_old_user_valid "${OLDNAME}"; then
  show_error "ERROR: ${OLDNAME@Q} invalid. Exiting."
  exit 3
fi

if ! is_new_user_valid "${NEWNAME}"; then
  show_error "ERROR: ${NEWNAME@Q} invalid. Exiting."
  exit 3
fi

export OLDNAME
export NEWNAME

#
# Rename user and migrate files
#

# Migrate the user.
show_info "Renaming user ${OLDNAME@Q} to ${NEWNAME@Q}..."
sudo usermod -l "${NEWNAME}" -d "/home/${NEWNAME}" -m "${OLDNAME}"
sudo groupmod -n "${NEWNAME}" "${OLDNAME}"

show_info "Fixing symlinks in /home/${NEWNAME} (provide ${NEWNAME} password)."
su "${NEWNAME}" - -c \
  "cd /home/${NEWNAME} && find . -type l -exec bash -c 'migrate_symlink \"{}\"' \;"

# Prompt to change password.
REPLY=$(ask_question "Change password for ${NEWNAME}? (y/N)")
if [[ "${REPLY}" =~ ^([Yy][Ee][Ss]|[Yy])$ ]]; then
  passwd "${NEWNAME}"
fi

show_success "Migrated!"