#!/bin/bash
# SPDX-Version: 3.0
# SPDX-CreationInfo: 2025-06-17; WEIDNER, Marc S.; <msw@coresecret.dev>
# SPDX-ExternalRef: GIT https://git.coresecret.dev/msw/CISS.debian.installer.git
# SPDX-FileContributor: WEIDNER, Marc S.; Centurion Intelligence Consulting Agency
# SPDX-FileCopyrightText: 2024-2025; WEIDNER, Marc S.; <msw@coresecret.dev>
# SPDX-FileType: SOURCE
# SPDX-License-Identifier: EUPL-1.2 OR LicenseRef-CCLA-1.0
# SPDX-LicenseComment: This file is part of the CISS.debian.installer.secure framework.
# SPDX-PackageName: CISS.debian.installer
# SPDX-Security-Contact: security@coresecret.eu
# SPDX-Comment: unlock_wrapper.sh to be executed as '/etc/crypttab' keyscript and as dropbear SSH forced command.

set -Ceuo pipefail

#######################################
# Variable declaration
#######################################
declare -r ASKPASS='/lib/cryptsetup/askpass'
declare -r REGEX='^\$[a-z0-9]+\$[./A-Za-z0-9]+\$[./A-Za-z0-9]+$'
# shellcheck disable=SC2155
declare -r CURRENTDATE=$(date +"%F %T")
declare -r GRE='\e[0;92m'
declare -r MAG='\e[0;95m'
declare -r RED='\e[0;91m'
declare -r RES='\e[0m'
declare -r NL='\n'
declare -g NUKE_ENABLED='false'
declare -g NUKE_HASH=''
declare -g PASSPHRASE=''

#######################################
# Print-colored text.
# Arguments:
#   1: Color code.
#   *: Text to print.
#######################################
color_echo() { declare c="$1"; shift; declare msg="${*}"; printf "%s%s %s%s" "${c}" "${msg}" "${RES}" "${NL}"; }

#######################################
# Die helper: print and exit hard.
# Globals:
#   NC
#   RED
# Arguments:
#   1: Message string to print.
#######################################
die() { printf "%s✘ %s %s%s" "${RED}" "$1" "${RES}" "${NL}" >&2; power_off 3; }

#######################################
# Drop to bash environment.
# Arguments:
#   None
#######################################
drop_bash() { stty echo; prompt_string; exec /bin/bash -i; }

#######################################
# Extract the 'nuke='-parameter from '/proc/cmdline'.
# Globals:
#   NUKE_ENABLED
#   NUKE_HASH
#   RED
# Arguments:
#   None
# Returns:
#   0: if 'nuke=' was found and extracted.
#   1: if not found.
#######################################
extract_nuke_hash() {
  declare ARG="" CMDLINE=""

  ### Read '/proc/cmdline' into a single line safely.
  read -r CMDLINE < /proc/cmdline
  for ARG in ${CMDLINE}; do
    case "${ARG}" in
      nuke=*)
        NUKE_HASH="${ARG#nuke=}"
        if [[ "${NUKE_HASH}" =~ ${REGEX} ]]; then
          NUKE_ENABLED="true"
          return 0
        else
          ### If there is a malformed Grub Bootparameter 'nuke=HASH', drop to bash.
          color_echo "${RED}" "✘ Nuke Hash Malformat : [${REGEX}] [${NUKE_HASH}]." >&2
          color_echo "${RED}" "✘ Dropping to bash ...:" >&2
          drop_bash
        fi
      ;;
    esac
  done
  ### No 'nuke=HASH' entry found.
  return 1
}

#######################################
# Gather information of all LUKS Devices available on the system.
# Arguments:
#   None
#######################################
gather_luks_devices() {
  declare prev=() curr=()
  declare -i tries=0

  while ((tries < 10)); do
    # shellcheck disable=SC2312
    mapfile -t curr < <(blkid -t TYPE=crypto_LUKS -o device | sort)

    if cmp <(printf '%s\n' "${curr[@]}") <(printf '%s\n' "${prev[@]}") >/dev/null; then
      break
    fi

    prev=("${curr[@]}")
    tries=$((tries + 1))
    sleep 1

  done

  printf '%s\n' "${curr[@]}"
}

#######################################
# Erase LUKS headers on all LUKS devices and shutdown system.
# Globals:
#   DEVICES_LUKS
#   RED
# Arguments:
#   None
#######################################
nuke() {
  declare dev=""
  for dev in "${DEVICES_LUKS[@]}"; do
    cryptsetup erase --batch-mode "${dev}" || true
    color_echo "${RED}" "✘ Error: LUKS Device Header malfunction: [${dev}]."
  done
  secure_unset_pass
  color_echo "${RED}" "✘ Error: LUKS Device malfunction. System Power Off in 16 seconds."
  power_off 16
}

#######################################
# Unified power-off routine.
# Arguments:
#   1: Sleep time before power-off in seconds (Default to 0 seconds).
#######################################
power_off() {
  declare -r wait="${1:-0}"
  sleep "${wait}"
  sync
  echo 1 >| /proc/sys/kernel/sysrq
  echo o >| /proc/sysrq-trigger
  ### The System powers off immediately; no further code is executed.
}

#######################################
# Print Error Message for Trap on 'ERR' on Terminal.
# Globals:
#   NL
#   RED
# Arguments:
#   1: ${?}
#   2: ${BASH_SOURCE[0]}
#   3: ${LINENO}
#   4: ${FUNCNAME[0]:-main}
#   5: ${BASH_COMMAND}
#######################################
print_scr_err() {
  declare -r scr_err_errcode="$1"
  declare -r scr_err_errscrt="$2"
  declare -r scr_err_errline="$3"
  declare -r scr_err_errfunc="$4"
  declare -r scr_err_errcmmd="$5"
  printf "%s" "${NL}"
  color_echo "${RED}" "✘ System caught an 'ERROR'. System Power Off in 16 seconds." >&2
  printf "%s" "${NL}"
  color_echo "${RED}" "✘ Error               : [${scr_err_errcode}]" >&2
  color_echo "${RED}" "✘ Line                : [${scr_err_errline}]" >&2
  color_echo "${RED}" "✘ Script              : [${scr_err_errscrt}]" >&2
  color_echo "${RED}" "✘ Function            : [${scr_err_errfunc}]" >&2
  color_echo "${RED}" "✘ Command             : [${scr_err_errcmmd}]" >&2
  printf "%s" "${NL}"
}

#######################################
# Print Error Message for '0'-Exit-Code on Terminal.
# Globals:
#   GRE
# Arguments:
#   None
#######################################
print_scr_scc() { color_echo "${GRE}" "✅ Script exited successfully. Proceeding with booting."; }

#######################################
# Generates informative shell prompt.
# Globals:
#   PS1
# Arguments:
#   None
#######################################
prompt_string() {
  declare -gx PS1="\
\[\033[1;91m\]\d\[\033[0m\]|\[\033[1;91m\]\u\[\033[0m\]@\
\[\033[1;95m\]\h\[\033[0m\]:\
\[\033[1;96m\]\w\[\033[0m\]/>>\
\$(if [[ \$? -eq 0 ]]; then \
  # Show exit status in green if zero
  echo -e \"\[\033[1;92m\]\$?\[\033[0m\]\"; \
else \
  # Show exit status in red otherwise
  echo -e \"\[\033[1;91m\]\$?\[\033[0m\]\"; \
fi)\
|~\$ "
}

#######################################
# Read Passphrase interactively.
# Globals:
#   ASKPASS
#   NUKE_ENABLED
#   NUKE_HASH
#   PASSPHRASE
# Arguments:
#   None
# Returns:
#   0: on success
#######################################
read_passphrase() {
  declare -a METHODS=("sha512crypt" "yescrypt" "scrypt" "bcrypt")
  declare METHOD="" SALT=""

  PASSPHRASE="$(${ASKPASS} "Enter passphrase: ")"

  if [[ "${NUKE_ENABLED,,}" == 'true' ]]; then
    ### Validate NUKE_HASH format (e.g., $id$salt$hash)
    if [[ "${NUKE_HASH}" =~ ${REGEX} ]]; then
      SALT="$(cut -d'$' -f3 <<< "${NUKE_HASH}")"
      for METHOD in "${METHODS[@]}"; do
        if mkpasswd -m "${METHOD}" -S "${SALT}" "${PASSPHRASE}" 2>/dev/null | grep -qF -- "${NUKE_HASH}"; then
          nuke
        fi
      done
    fi
  fi

  return 0
}

#######################################
# Securely unset the passphrase variable.
# Globals:
#   PASSPHRASE
# Arguments:
#   None
#######################################
secure_unset_pass() { unset PASSPHRASE; PASSPHRASE=""; }

#######################################
# Trap function to be called on 'ERR'.
# Arguments:
#   1: ${?}
#   2: ${BASH_SOURCE[0]}
#   3: ${LINENO}
#   4: ${FUNCNAME[0]:-main}
#   5: ${BASH_COMMAND}
#######################################
trap_on_err() {
  declare -r errcode="$1"
  declare -r errscrt="$2"
  declare -r errline="$3"
  declare -r errfunc="$4"
  declare -r errcmmd="$5"
  trap - ERR INT TERM
  stty echo
  print_scr_err "${errcode}" "${errscrt}" "${errline}" "${errfunc}" "${errcmmd}"
  power_off 16
}

#######################################
# Security Trap on 'INT' and 'TERM' to provide a deterministic way to not circumvent the nuke routine.
# Globals:
#   NL
#   RED
# Arguments:
#   None
#######################################
trap_on_term() {
  trap - ERR INT TERM
  stty echo
  printf "%s" "${NL}"
  color_echo "${RED}" "✘ Received termination signal. System Power Off in 3 seconds." >&2
  power_off 3
}

#######################################
# Check the integrity and authenticity of this script itself.
# Globals:
#   GRE
#   MAG
#   RED
# Arguments:
#   0: Script Name
#######################################
verify_script() {
  declare dir
  # shellcheck disable=SC2312
  dir="$(dirname "$(readlink -f "${0}")")"
  declare script; script="$(basename "${0}")"
  declare -a algo=("sha512" "sha384")
  declare cmd="" computed="" expected="" hashfile="" item="" sigfile=""

  for item in "${algo[@]}"; do
    hashfile="${dir}/${script}.${item}"
    sigfile="${hashfile}.sig"
    cmd="${item}sum"

    color_echo "${MAG}" "🔏 Verifying signature of: [${hashfile}]"
    gpgv --keyring /etc/keys/pubring.gpg "${sigfile}" "${hashfile}" || {
      color_echo "${RED}" "✘ Signature verification failed for: [${hashfile}]"
      color_echo "${RED}" "✘ System Power Off in 3 seconds ...."
      power_off 3
    }
    color_echo "${GRE}" "🔏 Verifying signature of: [${hashfile}] successful."

    color_echo "${MAG}" "🔢 Recomputing Hash: [${item}]"
    computed=$(${cmd} "${dir}/${script}" | awk '{print $1}')
    expected=$(cat "${hashfile}")

    if [[ "${computed}" != "${expected}" ]]; then
      color_echo "${RED}" "✘ Recomputed hash mismatch for     : [${item}]" >&2
      color_echo "${RED}" "✘ System Power Off in 3 seconds ...." >&2
      power_off 3
    fi
    color_echo "${GRE}" "🔢 Recomputing Hash: [${item}] successful."
  done

  color_echo "${GRE}" "🔏 All signatures and hashes verified successfully. Proceeding."
}

#######################################
# Main Program Sequence
# Globals:
#   CURRENTDATE
#   DEVICES_LUKS
#   GRE
#   MAG
#   NL
#   PASSPHRASE
#   RED
# Arguments:
#   None
#######################################
main() {
  trap 'trap_on_err "$?" "${BASH_SOURCE[0]}" "${LINENO}" "${FUNCNAME[0]:-main}" "${BASH_COMMAND}"' ERR
  trap 'trap_on_term' INT TERM

  color_echo "${RED}" "Coresecret Connection established."
  color_echo "${RED}" "Starting Time: ${CURRENTDATE}"
  color_echo "${MAG}" "Integrity self-check ..."
  printf "%s" "${NL}"

  verify_script

  ### Read newline-separated output into an array.
  color_echo "${MAG}" "Scanning for LUKS devices ..."
  printf "%s" "${NL}"
  # shellcheck disable=SC2312
  mapfile -t DEVICES_LUKS < <(gather_luks_devices)

  ### If there are no LUKS devices at all, drop to bash.
  if (( ${#DEVICES_LUKS[@]} == 0 )); then
    color_echo "${RED}" "✘ No LUKS Devices found. Dropping to bash ..."
    drop_bash
  fi

  ### Extract the 'nuke='-parameter from '/proc/cmdline'.
  extract_nuke_hash

  ### Read passphrase interactively.
  read_passphrase

  if printf "%s" "${PASSPHRASE}" | cryptroot-unlock; then

    secure_unset_pass
    exit 0

  else

    printf "%s" "${NL}"
    color_echo "${RED}" "✘ Unsuccessful command 'cryptroot-unlock'."
    color_echo "${GRE}" "✘ No LUKS operations performed. Dropping to bash ..."
    color_echo "${GRE}" "✘ To unlock 'root' partition, and maybe others like 'swap', run 'cryptroot-unlock'."
    drop_bash

  fi
}

main "${@}"
# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh