#!/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

guard_sourcing

#######################################
# --- UEFI GRUB Installation Strategy ---
#
# We explicitly install GRUB using '--no-nvram' to avoid modifying NVRAM entries inside the chroot environment, which is
# unreliable and can break host firmware boot order. Instead of relying on '--removable', we manually copy the GRUB EFI binary
# to the fallback location 'EFI/BOOT/BOOTX64.EFI'. This mirrors the behavior of '--removable', but gives us more control over
# the bootloader ID and file paths.
# Result:
# - GRUB is available under 'EFI/debian/grubx64.efi' (for manual boot entries).
# - GRUB is also available as 'EFI/BOOT/BOOTX64.EFI' (UEFI fallback path, no NVRAM needed).
# This setup ensures compatibility with systems that do not retain NVRAM entries (e.g., removable drives, VM firmware).
#######################################

#######################################
# Installation and setup of the GRUB2 (backported) version.
# The backported version MUST be installed for LUKS2 '/boot' encryption.
# Every 'apt-get install' command is invoked by adding 'export INITRD=No'
# to suppress the 'update-initramfs'-Kernel-Hooks, according to the initramfs-tools manpage:
# https://manpages.debian.org/testing/initramfs-tools-core/initramfs-tools.7.en.html
# Globals:
#   TARGET
#   VAR_ARCHITECTURE
#   VAR_RECIPE_FIRMWARE
#   VAR_SETUP_PATH
#   grub_background_enable
#   grub_background_path
#   grub_bootdev
#   grub_force_efi
#   grub_prober
#   grub_skip
#   grub_update_nvram
#   var_update_grub_required
# Arguments:
#   None
# Returns:
#   0: on success
#   ERR_GRUB_ARCHITECTURE: on failure
#######################################
installation_grub() {
  ### Declare Arrays, HashMaps, and Variables.
  declare -g  var_update_grub_required="false" grub_update_nvram=${grub_update_nvram:-false}
  declare -r  var_logfile="/root/.ciss/cdi/log/4230_update_grub.log"
  declare     var_background=""

  chroot_logger "${TARGET}${var_logfile}"

  get_grub_modinfo_path

  ensure_lowercase "grub_skip"
  ensure_lowercase "grub_background_enable"
  ensure_lowercase "grub_prober"
  ensure_lowercase "grub_update_nvram"
  ensure_lowercase "grub_force_efi"

  do_log "debug" "file_only" "4230() Preseeded firmware: '${VAR_RECIPE_FIRMWARE}', architecture: '${VAR_ARCHITECTURE}'"

  if [[ "${grub_skip}" != "true" ]]; then

    ### Install the GRUB2 backported version from the Bookworm backports repository.
    if [[ "${VAR_RECIPE_FIRMWARE}" == "uefi" ]]; then

      case "${VAR_ARCHITECTURE}" in

        amd64)
          chroot_script "${TARGET}" "
            export INITRD=No
            [[ -r /root/ciss_xdg_tmp.sh ]] && . /root/ciss_xdg_tmp.sh
            apt-get install -y --no-install-recommends grub2-common grub-efi-amd64 grub-efi-amd64-bin 2>&1 | tee -a ${var_logfile}
          "
          ;;

        arm64)
          chroot_script "${TARGET}" "
            export INITRD=No
            [[ -r /root/ciss_xdg_tmp.sh ]] && . /root/ciss_xdg_tmp.sh
            apt-get install -y --no-install-recommends grub2-common grub-efi-arm64 grub-efi-arm64-bin 2>&1 | tee -a ${var_logfile}
          "
          ;;

        *)
          do_log "emergency" "file_only" "4230() Unsupported architecture: ${VAR_ARCHITECTURE}"; return "${ERR_GRUB_ARCHITECTURE}"
          ;;

      esac

    else

      chroot_script "${TARGET}" "
        export INITRD=No
        [[ -r /root/ciss_xdg_tmp.sh ]] && . /root/ciss_xdg_tmp.sh
        apt-get install -y --no-install-recommends grub2-common grub-pc grub-pc-bin 2>&1 | tee -a ${var_logfile}
      "

    fi

    ### Enable booting from LUKS encrypted devices by default.
    cat << EOF >> "${TARGET}/etc/default/grub"

# Enable booting from LUKS encrypted devices by default.
GRUB_ENABLE_CRYPTODISK=y

EOF

    var_update_grub_required="true"

    ### Install a boot menu background.
    if [[ "${grub_background_enable}" == "true" ]]; then

      var_background=$(basename "${grub_background_path}")
      mkdir -p "${TARGET}/boot/grub"
      install -m 0640 -o root -g root "${VAR_SETUP_PATH}${grub_background_path}" "${TARGET}/boot/grub/${var_background}"

      cat << EOF >> "${TARGET}/etc/default/grub"
# Enable boot menu background.
GRUB_BACKGROUND="/boot/grub/${var_background}"

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command 'vbeinfo'
# GRUB_GFXMODE=1920x1080,1280x1024,1280x720,1024x768,800x600,640x480
GRUB_GFXMODE=1280x720
GRUB_GFXPAYLOAD_LINUX=keep

EOF

      var_update_grub_required="true"

    fi

    ### Change the GRUB OS detection configuration accordingly.
    if [[ "${grub_prober}" == "true" ]]; then

      chroot_exec "${TARGET}" export INITRD=No; apt-get install -y --no-install-recommends os-prober

      cat << EOF >> "${TARGET}/etc/default/grub"
# If your computer has multiple operating systems installed, then you
# probably want to run os-prober. However, if your computer is a host
# for guest OSes installed via LVM or raw disk devices, running
# os-prober can cause damage to those guest OSes as it mounts
# filesystems to look for things.
GRUB_DISABLE_OS_PROBER=false

EOF

      var_update_grub_required="true"

    elif [[ "${grub_prober}" == "false" ]]; then

      cat << EOF >> "${TARGET}/etc/default/grub"
# If your computer has multiple operating systems installed, then you
# probably want to run os-prober. However, if your computer is a host
# for guest OSes installed via LVM or raw disk devices, running
# os-prober can cause damage to those guest OSes as it mounts
# filesystems to look for things.
GRUB_DISABLE_OS_PROBER=true

EOF

      var_update_grub_required="true"

    fi

  else

    do_log "info" "file_only" "4230() GRUB2 setup skipped."
    return 0

  fi

  ### Install grub on the specific device.
  if [[ "${VAR_RECIPE_FIRMWARE}" == "uefi" ]]; then

    install_grub_uefi

  elif [[ "${VAR_RECIPE_FIRMWARE}" == "bios" ]]; then

    install_grub_bios

  fi

  [[ "${var_update_grub_required}" == "true" ]] && chroot_exec "${TARGET}" update-grub

  if [[ "${grub_force_efi}" == "true" ]]; then

    mkdir -p "${TARGET}/boot/efi/EFI/BOOT"
    cp "${TARGET}/boot/efi/EFI/debian/grubx64.efi" "${TARGET}/boot/efi/EFI/BOOT/BOOTX64.EFI"
    do_log "info" "file_only" "4230() Installed: GRUB on Device: '${grub_bootdev}' [UEFI] on: Default EFI Boot-Path."

  fi

  ### Setting the permissions to read and write for root only prevents non-root users from seeing the boot parameters or changing them.
  if [[ -f "${TARGET}/boot/grub/grub.cfg" ]]; then
    chown root:root "${TARGET}/boot/grub/grub.cfg"
    chmod 0640 "${TARGET}/boot/grub/grub.cfg"
  fi
  chmod -R 0700 "${TARGET}/etc/grub.d"

  guard_dir && return 0
}
### Prevents accidental 'unset -f'.
# shellcheck disable=SC2034
readonly -f installation_grub

#######################################
# Installs GRUB to BIOS in BIOS mode.
# Globals:
#   TARGET
#   VAR_MODINFO_PATH
#   grub_bootdev
#   var_update_grub_required
# Arguments:
#   None
# Returns:
#   0: on success
#   ERR_GRUB_INSTALL: on failure
#######################################
install_grub_bios() {
  ### Declare Arrays, HashMaps, and Variables.
  declare -a  ary_bios_arg=()
  declare     var_bios_mod=""

  if ! [[ -x "${TARGET}${VAR_MODINFO_PATH}" ]]; then
    do_log "emergency" "file_only" "4230() Missing: [${VAR_MODINFO_PATH}]."
    return "${ERR_GRUB_INSTALL}"
  fi

  ### Cryptographic modules.
  var_bios_mod+="cryptodisk gcry_rijndael gcry_sha256 gcry_sha512 gcry_whirlpool gcry_serpent gcry_twofish luks luks2 "
  ### Filesystem modules.
  var_bios_mod+="btrfs ext2 "
  ### Partitioning / Device / GPT
  var_bios_mod+="biosdisk mdraid1x part_gpt "
  ### Device / Terminal modules.
  var_bios_mod+="boot linux efi_gop efi_uga gfxterm gfxterm_background gfxterm_menu normal search search_fs_uuid search_label "
  ### Debug modules.
  var_bios_mod+="cat echo hexdump ls test terminfo"

  ary_bios_arg+=( --target=i386-pc --boot-directory=/boot "--modules=${var_bios_mod}" )

  chroot_exec "${TARGET}" grub-install "${ary_bios_arg[@]}" "${grub_bootdev}"
  do_log "info" "file_only" "4230() Installed: GRUB on Device: '${grub_bootdev}' [BIOS]."
  var_update_grub_required="true"

  return 0
}
### Prevents accidental 'unset -f'.
# shellcheck disable=SC2034
readonly -f install_grub_bios

#######################################
# Installs GRUB to ESP in UEFI mode.
# Globals:
#   TARGET
#   VAR_MODINFO_PATH
#   grub_bootdev
#   grub_update_nvram
#   var_update_grub_required
# Arguments:
#   None
# Returns:
#   0: on success
#   ERR_GRUB_INSTALL: on failure
#######################################
install_grub_uefi() {
  ### Declare Arrays, HashMaps, and Variables.
  declare -a  ary_uefi_arg=()
  declare     var_uefi_mod=""

  if ! [[ -x "${TARGET}${VAR_MODINFO_PATH}" ]]; then
    do_log "emergency" "file_only" "4230() Missing: [${VAR_MODINFO_PATH}]."
    return "${ERR_GRUB_INSTALL}"
  fi

  ### Cryptographic modules.
  var_uefi_mod+="cryptodisk gcry_rijndael gcry_sha256 gcry_sha512 gcry_whirlpool gcry_serpent gcry_twofish luks luks2 "
  ### Filesystem modules.
  var_uefi_mod+="btrfs ext2 "
  ### Partitioning / Device / GPT
  var_uefi_mod+="mdraid1x part_gpt "
  ### Device / Terminal modules.
  var_uefi_mod+="boot linux efi_gop efi_uga gfxterm gfxterm_background gfxterm_menu normal search search_fs_uuid search_label "
  ### Debug modules.
  var_uefi_mod+="cat echo hexdump ls test terminfo"

  ary_uefi_arg+=( --target=x86_64-efi --boot-directory=/boot --efi-directory=/boot/efi --bootloader-id=debian "--modules=${var_uefi_mod}" )

  [[ "${grub_update_nvram}" == "false" ]] && ary_uefi_arg+=( --no-nvram )

  chroot_exec "${TARGET}" grub-install "${ary_uefi_arg[@]}" "${grub_bootdev}" || return "${ERR_GRUB_INSTALL}"
  do_log "info" "file_only" "4230() Installed: GRUB on Device: '${grub_bootdev}' [UEFI]."
  var_update_grub_required="true"

  return 0
}
### Prevents accidental 'unset -f'.
# shellcheck disable=SC2034
readonly -f install_grub_uefi

#######################################
# Get the path of the required Grub modules.
# Globals:
#   VAR_ARCHITECTURE
#   VAR_MODINFO_PATH
#   VAR_RECIPE_FIRMWARE
# Arguments:
#   None
# Returns:
#   0: on success
#######################################
get_grub_modinfo_path() {
  ### Declare Arrays, HashMaps, and Variables.
  declare -gx VAR_MODINFO_PATH=""

  # shellcheck disable=SC2249
  case "${VAR_RECIPE_FIRMWARE}" in

    uefi)

      case "${VAR_ARCHITECTURE}" in

        amd64) VAR_MODINFO_PATH="/usr/lib/grub/x86_64-efi/modinfo.sh" ;;
        arm64) VAR_MODINFO_PATH="/usr/lib/grub/arm64-efi/modinfo.sh"  ;;
        i386)  VAR_MODINFO_PATH="/usr/lib/grub/i386-efi/modinfo.sh"   ;;
        *)     ;;

      esac
      ;;

    bios)

      VAR_MODINFO_PATH="/usr/lib/grub/i386-pc/modinfo.sh"
      ;;

  esac

  return 0
}
### Prevents accidental 'unset -f'.
# shellcheck disable=SC2034
readonly -f get_grub_modinfo_path
# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh