xref: /system/update_engine/scripts/brillo_update_payload

#!/bin/bash

#
# Copyright (C) 2015 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

# Script to generate a Brillo update for use by the update engine.
#
# usage: brillo_update_payload COMMAND [ARGS]
# The following commands are supported:
#  generate    generate an unsigned payload
#  hash        generate a payload or metadata hash
#  sign        generate a signed payload
#  properties  generate a properties file from a payload
#  verify      verify a payload by recreating a target image.
#
#  Generate command arguments:
#  --payload             generated unsigned payload output file
#  --source_image        if defined, generate a delta payload from the specified
#                        image to the target_image
#  --target_image        the target image that should be sent to clients
#  --metadata_size_file  if defined, generate a file containing the size of the
#                        payload metadata in bytes to the specified file
#
#  Hash command arguments:
#  --unsigned_payload    the input unsigned payload to generate the hash from
#  --signature_size      signature sizes in bytes in the following format:
#                        "size1:size2[:...]"
#  --payload_hash_file   if defined, generate a payload hash and output to the
#                        specified file
#  --metadata_hash_file  if defined, generate a metadata hash and output to the
#                        specified file
#
#  Sign command arguments:
#  --unsigned_payload        the input unsigned payload to insert the signatures
#  --payload                 the output signed payload
#  --signature_size          signature sizes in bytes in the following format:
#                            "size1:size2[:...]"
#  --payload_signature_file  the payload signature files in the following
#                            format:
#                            "payload_signature1:payload_signature2[:...]"
#  --metadata_signature_file the metadata signature files in the following
#                            format:
#                            "metadata_signature1:metadata_signature2[:...]"
#  --metadata_size_file      if defined, generate a file containing the size of
#                            the signed payload metadata in bytes to the
#                            specified file
#  Note that the number of signature sizes and payload signatures have to match.
#
#  Properties command arguments:
#  --payload                 the input signed or unsigned payload
#  --properties_file         the output path where to write the properties, or
#                            '-' for stdout.
#  Verify command arguments:
#  --payload             payload input file
#  --source_image        verify payload to the specified source image.
#  --target_image        the target image to verify upon.


# Exit codes:
EX_UNSUPPORTED_DELTA=100

warn() {
  echo "brillo_update_payload: warning: $*" >&2
}

die() {
  echo "brillo_update_payload: error: $*" >&2
  exit 1
}

# Loads shflags. We first look at the default install location; then look for
# crosutils (chroot); finally check our own directory (au-generator zipfile).
load_shflags() {
  local my_dir="$(dirname "$(readlink -f "$0")")"
  local path
  for path in /usr/share/misc {/usr/lib/crosutils,"${my_dir}"}/lib/shflags; do
    if [[ -r "${path}/shflags" ]]; then
      . "${path}/shflags" || die "Could not load ${path}/shflags."
      return
    fi
  done
  die "Could not find shflags."
}

load_shflags

HELP_GENERATE="generate: Generate an unsigned update payload."
HELP_HASH="hash: Generate the hashes of the unsigned payload and metadata used \
for signing."
HELP_SIGN="sign: Insert the signatures into the unsigned payload."
HELP_PROPERTIES="properties: Extract payload properties to a file."
HELP_VERIFY="verify: Verify a (signed) update payload."

usage() {
  echo "Supported commands:"
  echo
  echo "${HELP_GENERATE}"
  echo "${HELP_HASH}"
  echo "${HELP_SIGN}"
  echo "${HELP_PROPERTIES}"
  echo "${HELP_VERIFY}"
  echo
  echo "Use: \"$0 <command> --help\" for more options."
}

# Check that a command is specified.
if [[ $# -lt 1 ]]; then
  echo "Please specify a command [generate|hash|sign|properties]"
  exit 1
fi

# Parse command.
COMMAND="${1:-}"
shift

case "${COMMAND}" in
  generate)
    FLAGS_HELP="${HELP_GENERATE}"
    ;;

  hash)
    FLAGS_HELP="${HELP_HASH}"
    ;;

  sign)
    FLAGS_HELP="${HELP_SIGN}"
    ;;

  properties)
    FLAGS_HELP="${HELP_PROPERTIES}"
    ;;

  verify)
    FLAGS_HELP="${HELP_VERIFY}"
    ;;

  *)
    echo "Unrecognized command: \"${COMMAND}\"" >&2
    usage >&2
    exit 1
    ;;
esac

# Flags
FLAGS_HELP="Usage: $0 ${COMMAND} [flags]
${FLAGS_HELP}"

if [[ "${COMMAND}" == "generate" ]]; then
  DEFINE_string payload "" \
    "Path to output the generated unsigned payload file."
  DEFINE_string target_image "" \
    "Path to the target image that should be sent to clients."
  DEFINE_string source_image "" \
    "Optional: Path to a source image. If specified, this makes a delta update."
  DEFINE_string metadata_size_file "" \
    "Optional: Path to output metadata size."
  DEFINE_string max_timestamp "" \
    "Optional: The maximum unix timestamp of the OS allowed to apply this \
payload, should be set to a number higher than the build timestamp of the \
system running on the device, 0 if not specified."
fi
if [[ "${COMMAND}" == "hash" || "${COMMAND}" == "sign" ]]; then
  DEFINE_string unsigned_payload "" "Path to the input unsigned payload."
  DEFINE_string signature_size "" \
    "Signature sizes in bytes in the following format: size1:size2[:...]"
fi
if [[ "${COMMAND}" == "hash" ]]; then
  DEFINE_string metadata_hash_file "" \
    "Optional: Path to output metadata hash file."
  DEFINE_string payload_hash_file "" \
    "Optional: Path to output payload hash file."
fi
if [[ "${COMMAND}" == "sign" ]]; then
  DEFINE_string payload "" \
    "Path to output the generated unsigned payload file."
  DEFINE_string metadata_signature_file "" \
    "The metatada signatures in the following format: \
metadata_signature1:metadata_signature2[:...]"
  DEFINE_string payload_signature_file "" \
    "The payload signatures in the following format: \
payload_signature1:payload_signature2[:...]"
  DEFINE_string metadata_size_file "" \
    "Optional: Path to output metadata size."
fi
if [[ "${COMMAND}" == "properties" ]]; then
  DEFINE_string payload "" \
    "Path to the input signed or unsigned payload file."
  DEFINE_string properties_file "-" \
    "Path to output the extracted property files. If '-' is passed stdout will \
be used."
fi
if [[ "${COMMAND}" == "verify" ]]; then
  DEFINE_string payload "" \
    "Path to the input payload file."
  DEFINE_string target_image "" \
    "Path to the target image to verify upon."
  DEFINE_string source_image "" \
    "Optional: Path to a source image. If specified, the delta update is \
applied to this."
fi

DEFINE_string work_dir "${TMPDIR:-/tmp}" "Where to dump temporary files."

# Parse command line flag arguments
FLAGS "$@" || exit 1
eval set -- "${FLAGS_ARGV}"
set -e

# Override the TMPDIR with the passed work_dir flags, which anyway defaults to
# ${TMPDIR}.
TMPDIR="${FLAGS_work_dir}"
export TMPDIR

# Associative arrays from partition name to file in the source and target
# images. The size of the updated area must be the size of the file.
declare -A SRC_PARTITIONS
declare -A DST_PARTITIONS

# Associative arrays for the .map files associated with each src/dst partition
# file in SRC_PARTITIONS and DST_PARTITIONS.
declare -A SRC_PARTITIONS_MAP
declare -A DST_PARTITIONS_MAP

# List of partition names in order.
declare -a PARTITIONS_ORDER

# A list of temporary files to remove during cleanup.
CLEANUP_FILES=()

# Global options to force the version of the payload.
FORCE_MAJOR_VERSION=""
FORCE_MINOR_VERSION=""

# Path to the postinstall config file in target image if exists.
POSTINSTALL_CONFIG_FILE=""

# read_option_int <file.txt> <option_key> [default_value]
#
# Reads the unsigned integer value associated with |option_key| in a key=value
# file |file.txt|. Prints the read value if found and valid, otherwise prints
# the |default_value|.
read_option_uint() {
  local file_txt="$1"
  local option_key="$2"
  local default_value="${3:-}"
  local value
  if value=$(look "${option_key}=" "${file_txt}" | tail -n 1); then
    if value=$(echo "${value}" | cut -f 2- -d "=" | grep -E "^[0-9]+$"); then
      echo "${value}"
      return
    fi
  fi
  echo "${default_value}"
}

# truncate_file <file_path> <file_size>
#
# Truncate the given |file_path| to |file_size| using perl.
# The truncate binary might not be available.
truncate_file() {
  local file_path="$1"
  local file_size="$2"
  perl -e "open(FILE, \"+<\", \$ARGV[0]); \
           truncate(FILE, ${file_size}); \
           close(FILE);" "${file_path}"
}

# Create a temporary file in the work_dir with an optional pattern name.
# Prints the name of the newly created file.
create_tempfile() {
  local pattern="${1:-tempfile.XXXXXX}"
  mktemp --tmpdir="${FLAGS_work_dir}" "${pattern}"
}

cleanup() {
  local err=""
  rm -f "${CLEANUP_FILES[@]}" || err=1

  # If we are cleaning up after an error, or if we got an error during
  # cleanup (even if we eventually succeeded) return a non-zero exit
  # code. This triggers additional logging in most environments that call
  # this script.
  if [[ -n "${err}" ]]; then
    die "Cleanup encountered an error."
  fi
}

cleanup_on_error() {
  trap - INT TERM ERR EXIT
  cleanup
  die "Cleanup success after an error."
}

cleanup_on_exit() {
  trap - INT TERM ERR EXIT
  cleanup
}

trap cleanup_on_error INT TERM ERR
trap cleanup_on_exit EXIT


# extract_image <image> <partitions_array> [partitions_order]
#
# Detect the format of the |image| file and extract its updatable partitions
# into new temporary files. Add the list of partition names and its files to the
# associative array passed in |partitions_array|. If |partitions_order| is
# passed, set it to list of partition names in order.
extract_image() {
  local image="$1"

  # Brillo images are zip files. We detect the 4-byte magic header of the zip
  # file.
  local magic=$(head --bytes=4 "${image}" | hexdump -e '1/1 "%.2x"')
  if [[ "${magic}" == "504b0304" ]]; then
    echo "Detected .zip file, extracting Brillo image."
    extract_image_brillo "$@"
    return
  fi

  # Chrome OS images are GPT partitioned disks. We should have the cgpt binary
  # bundled here and we will use it to extract the partitions, so the GPT
  # headers must be valid.
  if cgpt show -q -n "${image}" >/dev/null; then
    echo "Detected GPT image, extracting Chrome OS image."
    extract_image_cros "$@"
    return
  fi

  die "Couldn't detect the image format of ${image}"
}

# extract_image_cros <image.bin> <partitions_array> [partitions_order]
#
# Extract Chromium OS recovery images into new temporary files.
extract_image_cros() {
  local image="$1"
  local partitions_array="$2"
  local partitions_order="${3:-}"

  local kernel root
  kernel=$(create_tempfile "kernel.bin.XXXXXX")
  CLEANUP_FILES+=("${kernel}")
  root=$(create_tempfile "root.bin.XXXXXX")
  CLEANUP_FILES+=("${root}")

  cros_generate_update_payload --extract \
    --image "${image}" \
    --kern_path "${kernel}" --root_path "${root}" \
    --work_dir "${FLAGS_work_dir}" --outside_chroot

  # Chrome OS uses major_version 1 payloads for all versions, even if the
  # updater supports a newer major version.
  FORCE_MAJOR_VERSION="1"

  # When generating legacy Chrome OS images, we need to use "boot" and "system"
  # for the partition names to be compatible with updating Brillo devices with
  # Chrome OS images.
  eval ${partitions_array}[boot]=\""${kernel}"\"
  eval ${partitions_array}[system]=\""${root}"\"

  if [[ -n "${partitions_order}" ]]; then
    eval "${partitions_order}=( \"system\" \"boot\" )"
  fi

  local part varname
  for part in boot system; do
    varname="${partitions_array}[${part}]"
    printf "md5sum of %s: " "${varname}"
    md5sum "${!varname}"
  done
}

# extract_image_brillo <target_files.zip> <partitions_array> [partitions_order]
#
# Extract the A/B updated partitions from a Brillo target_files zip file into
# new temporary files.
extract_image_brillo() {
  local image="$1"
  local partitions_array="$2"
  local partitions_order="${3:-}"

  local partitions=( "boot" "system" )
  local ab_partitions_list
  ab_partitions_list=$(create_tempfile "ab_partitions_list.XXXXXX")
  CLEANUP_FILES+=("${ab_partitions_list}")
  if unzip -p "${image}" "META/ab_partitions.txt" >"${ab_partitions_list}"; then
    if grep -v -E '^[a-zA-Z0-9_-]*$' "${ab_partitions_list}" >&2; then
      die "Invalid partition names found in the partition list."
    fi
    # Get partition list without duplicates.
    partitions=($(awk '!seen[$0]++' "${ab_partitions_list}"))
    if [[ ${#partitions[@]} -eq 0 ]]; then
      die "The list of partitions is empty. Can't generate a payload."
    fi
  else
    warn "No ab_partitions.txt found. Using default."
  fi
  echo "List of A/B partitions: ${partitions[@]}"

  if [[ -n "${partitions_order}" ]]; then
    eval "${partitions_order}=(${partitions[@]})"
  fi

  # All Brillo updaters support major version 2.
  FORCE_MAJOR_VERSION="2"

  if [[ "${partitions_array}" == "SRC_PARTITIONS" ]]; then
    # Source image
    local ue_config=$(create_tempfile "ue_config.XXXXXX")
    CLEANUP_FILES+=("${ue_config}")
    if ! unzip -p "${image}" "META/update_engine_config.txt" \
        >"${ue_config}"; then
      warn "No update_engine_config.txt found. Assuming pre-release image, \
using payload minor version 2"
    fi
    # For delta payloads, we use the major and minor version supported by the
    # old updater.
    FORCE_MINOR_VERSION=$(read_option_uint "${ue_config}" \
      "PAYLOAD_MINOR_VERSION" 2)
    FORCE_MAJOR_VERSION=$(read_option_uint "${ue_config}" \
      "PAYLOAD_MAJOR_VERSION" 2)

    # Brillo support for deltas started with minor version 3.
    if [[ "${FORCE_MINOR_VERSION}" -le 2 ]]; then
      warn "No delta support from minor version ${FORCE_MINOR_VERSION}. \
Disabling deltas for this source version."
      exit ${EX_UNSUPPORTED_DELTA}
    fi
  else
    # Target image
    local postinstall_config=$(create_tempfile "postinstall_config.XXXXXX")
    CLEANUP_FILES+=("${postinstall_config}")
    if unzip -p "${image}" "META/postinstall_config.txt" \
        >"${postinstall_config}"; then
      POSTINSTALL_CONFIG_FILE="${postinstall_config}"
    fi
  fi

  local part part_file temp_raw filesize
  for part in "${partitions[@]}"; do
    part_file=$(create_tempfile "${part}.img.XXXXXX")
    CLEANUP_FILES+=("${part_file}")
    unzip -p "${image}" "IMAGES/${part}.img" >"${part_file}"

    # If the partition is stored as an Android sparse image file, we need to
    # convert them to a raw image for the update.
    local magic=$(head --bytes=4 "${part_file}" | hexdump -e '1/1 "%.2x"')
    if [[ "${magic}" == "3aff26ed" ]]; then
      temp_raw=$(create_tempfile "${part}.raw.XXXXXX")
      CLEANUP_FILES+=("${temp_raw}")
      echo "Converting Android sparse image ${part}.img to RAW."
      simg2img "${part_file}" "${temp_raw}"
      # At this point, we can drop the contents of the old part_file file, but
      # we can't delete the file because it will be deleted in cleanup.
      true >"${part_file}"
      part_file="${temp_raw}"
    fi

    # Extract the .map file (if one is available).
    part_map_file=$(create_tempfile "${part}.map.XXXXXX")
    CLEANUP_FILES+=("${part_map_file}")
    unzip -p "${image}" "IMAGES/${part}.map" >"${part_map_file}" || \
      part_map_file=""

    # delta_generator only supports images multiple of 4 KiB. For target images
    # we pad the data with zeros if needed, but for source images we truncate
    # down the data since the last block of the old image could be padded on
    # disk with unknown data.
    filesize=$(stat -c%s "${part_file}")
    if [[ $(( filesize % 4096 )) -ne 0 ]]; then
      if [[ "${partitions_array}" == "SRC_PARTITIONS" ]]; then
        echo "Rounding DOWN partition ${part}.img to a multiple of 4 KiB."
        : $(( filesize = filesize & -4096 ))
        if [[ ${filesize} == 0 ]]; then
          echo "Source partition ${part}.img is empty after rounding down," \
            "skipping."
          continue
        fi
      else
        echo "Rounding UP partition ${part}.img to a multiple of 4 KiB."
        : $(( filesize = (filesize + 4095) & -4096 ))
      fi
      truncate_file "${part_file}" "${filesize}"
    fi

    eval "${partitions_array}[\"${part}\"]=\"${part_file}\""
    eval "${partitions_array}_MAP[\"${part}\"]=\"${part_map_file}\""
    echo "Extracted ${partitions_array}[${part}]: ${filesize} bytes"
  done
}

validate_generate() {
  [[ -n "${FLAGS_payload}" ]] ||
    die "You must specify an output filename with --payload FILENAME"

  [[ -n "${FLAGS_target_image}" ]] ||
    die "You must specify a target image with --target_image FILENAME"
}

cmd_generate() {
  local payload_type="delta"
  if [[ -z "${FLAGS_source_image}" ]]; then
    payload_type="full"
  fi

  echo "Extracting images for ${payload_type} update."

  extract_image "${FLAGS_target_image}" DST_PARTITIONS PARTITIONS_ORDER
  if [[ "${payload_type}" == "delta" ]]; then
    extract_image "${FLAGS_source_image}" SRC_PARTITIONS
  fi

  echo "Generating ${payload_type} update."
  # Common payload args:
  GENERATOR_ARGS=( -out_file="${FLAGS_payload}" )

  local part old_partitions="" new_partitions="" partition_names=""
  local old_mapfiles="" new_mapfiles=""
  for part in "${PARTITIONS_ORDER[@]}"; do
    if [[ -n "${partition_names}" ]]; then
      partition_names+=":"
      new_partitions+=":"
      old_partitions+=":"
      new_mapfiles+=":"
      old_mapfiles+=":"
    fi
    partition_names+="${part}"
    new_partitions+="${DST_PARTITIONS[${part}]}"
    old_partitions+="${SRC_PARTITIONS[${part}]:-}"
    new_mapfiles+="${DST_PARTITIONS_MAP[${part}]:-}"
    old_mapfiles+="${SRC_PARTITIONS_MAP[${part}]:-}"
  done

  # Target image args:
  GENERATOR_ARGS+=(
    -partition_names="${partition_names}"
    -new_partitions="${new_partitions}"
    -new_mapfiles="${new_mapfiles}"
  )

  if [[ "${payload_type}" == "delta" ]]; then
    # Source image args:
    GENERATOR_ARGS+=(
      -old_partitions="${old_partitions}"
      -old_mapfiles="${old_mapfiles}"
    )
    if [[ -n "${FORCE_MINOR_VERSION}" ]]; then
      GENERATOR_ARGS+=( --minor_version="${FORCE_MINOR_VERSION}" )
    fi
  fi

  if [[ -n "${FORCE_MAJOR_VERSION}" ]]; then
    GENERATOR_ARGS+=( --major_version="${FORCE_MAJOR_VERSION}" )
  fi

  if [[ -n "${FLAGS_metadata_size_file}" ]]; then
    GENERATOR_ARGS+=( --out_metadata_size_file="${FLAGS_metadata_size_file}" )
  fi

  if [[ -n "${FLAGS_max_timestamp}" ]]; then
    GENERATOR_ARGS+=( --max_timestamp="${FLAGS_max_timestamp}" )
  fi

  if [[ -n "${POSTINSTALL_CONFIG_FILE}" ]]; then
    GENERATOR_ARGS+=(
      --new_postinstall_config_file="${POSTINSTALL_CONFIG_FILE}"
    )
  fi

  echo "Running delta_generator with args: ${GENERATOR_ARGS[@]}"
  "${GENERATOR}" "${GENERATOR_ARGS[@]}"

  echo "Done generating ${payload_type} update."
}

validate_hash() {
  [[ -n "${FLAGS_signature_size}" ]] ||
    die "You must specify signature size with --signature_size SIZES"

  [[ -n "${FLAGS_unsigned_payload}" ]] ||
    die "You must specify the input unsigned payload with \
--unsigned_payload FILENAME"

  [[ -n "${FLAGS_payload_hash_file}" ]] ||
    die "You must specify --payload_hash_file FILENAME"

  [[ -n "${FLAGS_metadata_hash_file}" ]] ||
    die "You must specify --metadata_hash_file FILENAME"
}

cmd_hash() {
  "${GENERATOR}" \
      -in_file="${FLAGS_unsigned_payload}" \
      -signature_size="${FLAGS_signature_size}" \
      -out_hash_file="${FLAGS_payload_hash_file}" \
      -out_metadata_hash_file="${FLAGS_metadata_hash_file}"

  echo "Done generating hash."
}

validate_sign() {
  [[ -n "${FLAGS_signature_size}" ]] ||
    die "You must specify signature size with --signature_size SIZES"

  [[ -n "${FLAGS_unsigned_payload}" ]] ||
    die "You must specify the input unsigned payload with \
--unsigned_payload FILENAME"

  [[ -n "${FLAGS_payload}" ]] ||
    die "You must specify the output signed payload with --payload FILENAME"

  [[ -n "${FLAGS_payload_signature_file}" ]] ||
    die "You must specify the payload signature file with \
--payload_signature_file SIGNATURES"

  [[ -n "${FLAGS_metadata_signature_file}" ]] ||
    die "You must specify the metadata signature file with \
--metadata_signature_file SIGNATURES"
}

cmd_sign() {
  GENERATOR_ARGS=(
    -in_file="${FLAGS_unsigned_payload}"
    -signature_size="${FLAGS_signature_size}"
    -signature_file="${FLAGS_payload_signature_file}"
    -metadata_signature_file="${FLAGS_metadata_signature_file}"
    -out_file="${FLAGS_payload}"
  )

  if [[ -n "${FLAGS_metadata_size_file}" ]]; then
    GENERATOR_ARGS+=( --out_metadata_size_file="${FLAGS_metadata_size_file}" )
  fi

  "${GENERATOR}" "${GENERATOR_ARGS[@]}"
  echo "Done signing payload."
}

validate_properties() {
  [[ -n "${FLAGS_payload}" ]] ||
    die "You must specify the payload file with --payload FILENAME"

  [[ -n "${FLAGS_properties_file}" ]] ||
    die "You must specify a non empty --properties_file FILENAME"
}

cmd_properties() {
  "${GENERATOR}" \
      -in_file="${FLAGS_payload}" \
      -properties_file="${FLAGS_properties_file}"
}

validate_verify() {
  [[ -n "${FLAGS_payload}" ]] ||
    die "Error: you must specify an input filename with --payload FILENAME"

  [[ -n "${FLAGS_target_image}" ]] ||
    die "Error: you must specify a target image with --target_image FILENAME"
}

cmd_verify() {
  local payload_type="delta"
  if [[ -z "${FLAGS_source_image}" ]]; then
    payload_type="full"
  fi

  echo "Extracting images for ${payload_type} update."

  if [[ "${payload_type}" == "delta" ]]; then
    extract_image "${FLAGS_source_image}" SRC_PARTITIONS
  fi
  extract_image "${FLAGS_target_image}" DST_PARTITIONS PARTITIONS_ORDER

  declare -A TMP_PARTITIONS
  for part in "${PARTITIONS_ORDER[@]}"; do
    local tmp_part=$(create_tempfile "tmp_part.bin.XXXXXX")
    echo "Creating temporary target partition ${tmp_part} for ${part}"
    CLEANUP_FILES+=("${tmp_part}")
    TMP_PARTITIONS[${part}]=${tmp_part}
    local FILESIZE=$(stat -c%s "${DST_PARTITIONS[${part}]}")
    echo "Truncating ${TMP_PARTITIONS[${part}]} to ${FILESIZE}"
    truncate_file "${TMP_PARTITIONS[${part}]}" "${FILESIZE}"
  done

  echo "Verifying ${payload_type} update."
  # Common payload args:
  GENERATOR_ARGS=( -in_file="${FLAGS_payload}" )

  local part old_partitions="" new_partitions="" partition_names=""
  for part in "${PARTITIONS_ORDER[@]}"; do
    if [[ -n "${partition_names}" ]]; then
      partition_names+=":"
      new_partitions+=":"
      old_partitions+=":"
    fi
    partition_names+="${part}"
    new_partitions+="${TMP_PARTITIONS[${part}]}"
    old_partitions+="${SRC_PARTITIONS[${part}]:-}"
  done

  # Target image args:
  GENERATOR_ARGS+=(
    -partition_names="${partition_names}"
    -new_partitions="${new_partitions}"
  )

  if [[ "${payload_type}" == "delta" ]]; then
    # Source image args:
    GENERATOR_ARGS+=(
      -old_partitions="${old_partitions}"
    )
  fi

  if [[ -n "${FORCE_MAJOR_VERSION}" ]]; then
    GENERATOR_ARGS+=( --major_version="${FORCE_MAJOR_VERSION}" )
  fi

  echo "Running delta_generator to verify ${payload_type} payload with args: \
${GENERATOR_ARGS[@]}"
  "${GENERATOR}" "${GENERATOR_ARGS[@]}"

  if [[ $? -eq 0 ]]; then
    echo "Done applying ${payload_type} update."
    echo "Checking the newly generated partitions against the target partitions"
    for part in "${PARTITIONS_ORDER[@]}"; do
      cmp "${TMP_PARTITIONS[${part}]}" "${DST_PARTITIONS[${part}]}"
      local not_str=""
      if [[ $? -ne 0 ]]; then
        not_str="in"
      fi
      echo "The new partition (${part}) is ${not_str}valid."
    done
  else
    echo "Failed to apply ${payload_type} update."
  fi
}

# Sanity check that the real generator exists:
GENERATOR="$(which delta_generator || true)"
[[ -x "${GENERATOR}" ]] || die "can't find delta_generator"

case "$COMMAND" in
  generate) validate_generate
            cmd_generate
            ;;
  hash) validate_hash
        cmd_hash
        ;;
  sign) validate_sign
        cmd_sign
        ;;
  properties) validate_properties
              cmd_properties
              ;;
  verify) validate_verify
          cmd_verify
          ;;
esac