mkiso

#!/usr/bin/env bash

# Embeds a preseed file into a Debian ISO image. (amd64, arm64)
# Optionally encrypts the filesystem
# Optionally encrypts /boot

# Commands from:
# https://wiki.debian.org/DebianInstaller/Modify/CD
# https://wiki.debian.org/RepackBootableISO
# https://wiki.debian.org/ManipulatingISOs
# https://wiki.debian.org/DebianInstaller/Preseed/EditIso
# https://help.ubuntu.com/community/Grub2/Submenus

# You may need to modify the "version" variable if you're using a different iso
# format than debian-11.0.0-arm64-netinst.iso

# Print commands and their arguments as they are executed
# set -x

iso_files="isofiles"
orig_iso="${1}"
output_dir="output"
preseed_files="files/preseed_files"
settings_file="${2-options.env}"
settings=$(sed -e 's/\r//' -e '/^#/d;/^\s*$/d;/^\w*$/d' "${settings_file}")

shopt -s extglob
arch="${1##"debian-"}"
arch="${arch##+([0-9.])-}"
arch="${arch%%-netinst.iso}"

release="${1##firmware-}"
release="${release##debian-}"
release="${release%%.*}"

version="${1##firmware-}"
version="${version##debian-}"
version="${version%%"-${arch}-netinst.iso"}"
shopt -u extglob

volume_id="Debian ${version} ${arch} n"

# Set variables based on release version
case "${release}" in
  '9')  codename="stretch";;
  '10') codename="buster";;
  '11') codename="bullseye";;
  '12') codename="bookworm";;
  '13') codename="trixie";;
  '14') codename="forky";;
esac

# Colored output
code_grn() { tput setaf 2; printf '%s\n' "${1}"; tput sgr0; }
code_red() { tput setaf 1; printf '%s\n' "${1}"; tput sgr0; }
code_yel() { tput setaf 3; printf '%s\n' "${1}"; tput sgr0; }

# Error checks
if ! command -v "xorriso" >/dev/null 2>&1; then
  code_red "[ERROR] xorriso not installed!"
  echo
  exit 1
fi

if [ -z "${1}" ]; then
  code_red "[ERROR] Usage:"
  printf '%s\n' "  ./$(basename "${0}") debian-xx.x.x-xxx64-netinst.iso"
  echo
  exit 1
fi

if [ ! -f "${settings_file}" ]; then
  code_red "[INFO] missing ${settings_file} file"
  echo
  exit 1
fi

if [ -d "${iso_files}" ]; then
  code_red "[ERROR] Directory ${iso_files} exists; Please correct and re-run"
  echo
  exit 1
fi

[ ! -d "${output_dir}" ] && mkdir "${output_dir}"

# Export environment variables
load_env() {
  while IFS='=' read -r key value; do
    value="${value//\"/}"
    value="${value//\'/}"
    # shellcheck disable=SC2163
    printf -v "${key}" '%s' "${value}" && export "${key}"
  done <<< "${settings}"
}

# Unset environment variables
unload_env() {
  while IFS='=' read -r key _; do
    unset "${key}"
  done <<< "${settings}"
}

# Prompt for amd64 options
preseed_amd64() {
  printf '%s\n' "Select which type of ISO you would like to generate: "
  PS3='Please choose: '

  options=("kvm" "kvm: encrypted" "workstation: encrypted"
           "workstation: encrypted boot")

  select opt in "${options[@]}"; do
    case $REPLY in
      1)
        printf '%s\n\n' "  Configuring preseed iso for $opt"
        new_iso="Debian-${version}-PRESEED-kvm.iso"
        preseed_file="${preseed_files}/kvm-${codename}.cfg"
        break
        ;;
      2)
        printf '%s\n\n' "  Configuring preseed iso for $opt"
        new_iso="Debian-${version}-PRESEED-kvm_encrypted.iso"
        preseed_file="${preseed_files}/kvm-${codename}-encrypted.cfg"
        break
        ;;
      3)
        printf '%s\n\n' "  Configuring preseed iso for $opt"
        new_iso="Debian-${version}-PRESEED-ws-full_encrypted.iso"
        preseed_file="${preseed_files}/workstation-${codename}-encrypted.cfg"
        break
        ;;
      4)
        printf '%s\n\n' "  Configuring preseed iso for $opt"
        new_iso="Debian-${version}-PRESEED-ws-full_encrypted.iso"
        preseed_file="${preseed_files}/workstation-${codename}-encrypted_boot.cfg"
        break
        ;;
      *) code_red  "[ERROR] Invalid option: $REPLY" ;;
    esac
  done
}

# Prompt for arm64 options
preseed_arm64() {
  printf '%s\n' "Select which type of ISO you would like to generate: "
  PS3='Please choose: '

  options=("utm" "utm: encrypted")

  select opt in "${options[@]}"; do
    case $REPLY in
      1)
        printf '%s\n\n' "  Configuring preseed iso for $opt"
        new_iso="Debian-${version}-PRESEED-utm.iso"
        preseed_file="${preseed_files}/utm-${codename}.cfg"
        break
        ;;
      2)
        printf '%s\n\n' "  Configuring preseed iso for $opt"
        new_iso="Debian-${version}-PRESEED-utm_encrypted.iso"
        preseed_file="${preseed_files}/utm-${codename}-encrypted.cfg"
        break
        ;;
      *) code_red "[ERROR] Invalid option: $REPLY" ;;
    esac
  done
}

# Validate the preseed file
check_debconf_selections() {
  local updated_seed_file="${1}"
  debconf-set-selections --checkonly "${updated_seed_file}" || {
    code_red "[ERROR] debconf-set-selections failed. Error in preseed file?"
    exit 1
  }
}

# Error if $new_iso exists
iso_exists() {
  if [ -f "${new_iso}" ]; then
    code_red "[ERROR] ISO ${new_iso} exists; Please correct and re-run"
    exit 1
  fi
}

# amd64 preparation
extract_mbr_amd64() {
  # Extract mbr from ISO
  dd if="${orig_iso}" bs=1 count=446 of="${mbr_template}"
}

# arm64 preparation
extract_efi_arm64() {
  code_yel "[INFO] sudo access needed for fdisk operation on ${orig_iso}"
  start_block=$(sudo fdisk -l "${orig_iso}" | grep -F "${orig_iso}"2 | awk '{print $2}')
  block_count=$(sudo fdisk -l "${orig_iso}" | grep -F "${orig_iso}"2 | awk '{print $4}')

  # Extract EFI partition image
  if test "${start_block}" -gt 0 -a "${block_count}" -gt 0 2> /dev/null; then
    dd if="${orig_iso}" bs=512 skip="${start_block}" count="${block_count}" of="${efi_template}"
  else
    code_red "[ERROR] Cannot read start block and block count from fdisk" >&2
  fi
}

# Unpack the ISO image
unpack_iso() {
  mkdir -p "${iso_files}"
  xorriso -osirrox on -indev "${orig_iso}" -extract / "${iso_files}"
}

# Copy preseed files to the extracted ISO
put_preseed() {
  load_env
  envsubst < "${preseed_file}" > "${iso_files}/preseed.cfg"
  check_debconf_selections "${iso_files}/preseed.cfg"
  unload_env
  chmod 0644 "${iso_files}/preseed.cfg"
  cp -a "files/preseed_scripts" "${iso_files}"
}

# Configure the amd64 install menu
auto_select_amd64() {
  # Enable write permissions on menu files
  chmod u+w "${iso_files}/isolinux" "${iso_files}/isolinux/isolinux.cfg"

  # Configure default selection
  sed -i 's/^default .*/default auto/g' "${iso_files}/isolinux/isolinux.cfg"

  # Disable write permissions on menu files
  chmod u-w "${iso_files}/isolinux" "${iso_files}/isolinux/isolinux.cfg"

  # Set permissions for grub menu
  chmod -R u+w "${iso_files}/boot/grub"

  # Autoselect uefi menu
  sed -i "/^menuentry --hotkey=g/i set default=\'Advanced options ...>... Automated install\'\nset timeout=5" isofiles/boot/grub/grub.cfg

  # Disable write permissions on grub menu
  chmod -R u-w "${iso_files}/boot/grub"
}

# Configure the arm64 install menu
auto_select_arm64() {
  # Set permissions for grub menu
  chmod -R u+w "${iso_files}/boot/grub"

  # Autoselect uefi menu
  sed -i "/^insmod gzio/a set default=\'Advanced options ...>... Automated install\'\nset timeout=5" isofiles/boot/grub/grub.cfg

  # Disable write permissions on grub dir
  chmod -R u-w "${iso_files}/boot/grub"
}

# Update the initrd
mod_initrd() {
  # Enter the isofiles directory
  cd "${iso_files}" || exit

  # Enable write permissions on initrd directory
  chmod -R u+w "${initrd_dir}/"

  # Unzip initrd
  gunzip "${initrd_dir}/initrd.gz"

  # Add the preseed to the initrd
  echo preseed.cfg | cpio -H newc -o -A -F "${initrd_dir}/initrd"

  # Re-Zip initrd
  gzip "${initrd_dir}/initrd"

  # Enable write permissions on md5sum.txt
  chmod u+w md5sum.txt

  # Generate new md5sum.txt
  find . ! -name "md5sum.txt" ! -path "./isolinux/*" -follow -type f -print0 |
    xargs -0 md5sum > md5sum.txt

  # Disable write permissions on md5sum.txt before writing iso
  chmod u-w md5sum.txt

  # Disable write permissions on initrd directory before writing iso
  chmod -R u-w "${initrd_dir}/"

  # Move back a directory
  cd .. || exit
}

# Re-pack amd64 ISO image
pack_amd64() {
  xorriso -as mkisofs \
    -r -V "${volume_id}" \
    -o "${output_dir}/${new_iso}" \
    -J -joliet-long -cache-inodes \
    -isohybrid-mbr "${mbr_template}" \
    -b isolinux/isolinux.bin \
    -c isolinux/boot.cat \
    -boot-load-size 4 -boot-info-table -no-emul-boot \
    -eltorito-alt-boot \
    -e boot/grub/efi.img -no-emul-boot \
    -isohybrid-gpt-basdat -isohybrid-apm-hfsplus \
    "${iso_files}" 2> /dev/null
}

# Re-pack arm64 ISO image
pack_arm64() {
  xorriso -as mkisofs \
    -r -V "${volume_id}" \
    -o "${output_dir}/${new_iso}" \
    -J -joliet-long -cache-inodes \
    -e boot/grub/efi.img \
    -no-emul-boot \
    -append_partition 2 0xef "${efi_template}" \
    -partition_cyl_align all \
    "${iso_files}" 2> /dev/null
}

# Generate SHA512SUM file
gen_sha() {
  cd "${output_dir}" || exit
  shasum=$(sha512sum "${new_iso}")
  printf '%s\n' "${shasum}" >> "SHA512SUMS"
  cd .. || exit
}

# Clean up temporary files
clean_up() {
  # Need write permissions so we can delete
  chmod -R u+w "${iso_files}"
  [ -f "${efi_template}" ] && rm -f "${efi_template}"
  [ -f "${mbr_template}" ] && rm -f "${mbr_template}"
  rm -rf "${iso_files}"
}

# Do the things..
case "${arch}" in
  "amd64")
    mbr_template="/tmp/isohdpfx.bin"
    initrd_dir="install.amd"
    preseed_amd64
    iso_exists
    extract_mbr_amd64
    unpack_iso
    put_preseed
    auto_select_amd64
    mod_initrd
    pack_amd64
    gen_sha
    ;;
  "arm64")
    efi_template="/tmp/efi.img"
    initrd_dir="install.a64"
    preseed_arm64
    iso_exists
    extract_efi_arm64
    unpack_iso
    put_preseed
    auto_select_arm64
    mod_initrd
    pack_arm64
    gen_sha
    ;;
esac

# Newline for cleaner output formatting
echo

# Clean up
read -rp "Would you like to remove ${iso_files} directory? [Yy|Nn] " response

case "${response}" in
  "Y" | "y")
    printf '%s\n' "[INFO] Cleaning up!"
    clean_up
    ;;
  *)
    printf '%s\n' "[INFO] Exiting without cleaning up"
    exit 0
    ;;
esac

code_grn "Done, enjoy!"

# vim: ft=sh ts=2 sts=2 sw=2 sr et