diff --git a/scripts/image_signing/sign_official_cos_build.sh b/scripts/image_signing/sign_official_cos_build.sh
new file mode 100755
index 0000000..1e859c9
--- /dev/null
+++ b/scripts/image_signing/sign_official_cos_build.sh
@@ -0,0 +1,731 @@
+#!/bin/bash
+
+# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Sign the final build image using the "official" keys.
+#
+# Prerequisite tools needed in the system path:
+#
+#  futility (from src/platform/vboot_reference)
+#  vbutil_kernel (from src/platform/vboot_reference)
+#  vbutil_key (from src/platform/vboot_reference)
+#  cgpt (from src/platform/vboot_reference)
+#  dump_kernel_config (from src/platform/vboot_reference)
+#  verity (from src/platform/verity)
+#  load_kernel_test (from src/platform/vboot_reference)
+#  dumpe2fs
+#  sha1sum
+#  kms_signer, if KEY_ORIGIN == kms.
+
+# Load common constants and variables.
+. "$(dirname "$0")/common.sh"
+
+# Print usage string
+usage() {
+  cat <<EOF
+Usage: $PROG <type> <key_origin> input_image /path/to/keys/dir [output_image] [version_file]
+where <type> is one of:
+             base (sign a base image, similar to an SSD image)
+             update_payload (sign a delta update hash)
+key_origin: "local" for local keys, or "kms" for Cloud KMS keys.
+output_image: File name of the signed output image
+version_file: File name of where to read the kernel and firmware versions.
+
+If you are signing an image, you must specify an [output_image] and
+optionally, a [version_file].
+
+EOF
+  if [[ $# -gt 0 ]]; then
+    error "$*"
+    exit 1
+  fi
+  exit 0
+}
+
+# Verify we have as many arguments as we expect, else show usage & quit.
+# Usage:
+#  check_argc <number args> <exact number>
+#  check_argc <number args> <lower bound> <upper bound>
+check_argc() {
+  case $# in
+  2)
+    if [[ $1 -ne $2 ]]; then
+      usage "command takes exactly $2 args"
+    fi
+    ;;
+  3)
+    if [[ $1 -lt $2 || $1 -gt $3 ]]; then
+      usage "command takes $2 to $3 args"
+    fi
+    ;;
+  *)
+    die "check_argc: incorrect number of arguments"
+  esac
+}
+
+# Abort on errors.
+set -e
+
+# Add to the path since some tools reside here and may not be in the non-root
+# system path.
+PATH=$PATH:/usr/sbin:/sbin
+
+TYPE=$1
+KEY_ORIGIN=$2
+INPUT_IMAGE=$3
+KEY_DIR=$4
+OUTPUT_IMAGE=$5
+VERSION_FILE=$6
+
+FIRMWARE_VERSION=1
+KERNEL_VERSION=1
+
+# Make sure the tools we need are available.
+prereqs=("${FUTILITY}" vbutil_kernel cgpt dump_kernel_config verity)
+prereqs+=(load_kernel_test dumpe2fs sha1sum e2fsck)
+if [[ "${KEY_ORIGIN}" == "kms" ]]; then
+  prereqs+=(kms_signer)
+fi
+for prereq in ${prereqs[@]}; do
+  type -P "${prereq}" &>/dev/null || \
+    die "${prereq} tool not found."
+done
+
+# TODO(gauravsh): These are duplicated from chromeos-setimage. We need
+# to move all signing and rootfs code to one single place where it can be
+# reused. crosbug.com/19543
+
+# get_verity_arg <commandline> <key> -> <value>
+get_verity_arg() {
+  echo "$1" | sed -n "s/.*\b$2=\([^ \"]*\).*/\1/p"
+}
+
+# Get the dmparams parameters from a kernel config.
+get_dmparams_from_config() {
+  local kernel_config=$1
+  echo ${kernel_config} | sed -nre 's/.*dm="([^"]*)".*/\1/p'
+}
+# Get the verity root digest hash from a kernel config command line.
+get_hash_from_config() {
+  local kernel_config=$1
+  local dm_config=$(get_dmparams_from_config "${kernel_config}")
+  local vroot_dev=$(get_dm_slave "${dm_config}" vroot)
+  echo $(get_verity_arg "${vroot_dev}" root_hexdigest)
+}
+
+# Get the slave device and its args
+# get_dm_ags $dm_config [vboot|vroot]
+# Assumes we have only one slave device per device
+get_dm_slave() {
+  local dm=$1
+  local device=$2
+  echo $(echo "${dm}" | sed -nre "s/.*${device}[^,]*,([^,]*).*/\1/p")
+}
+
+# Set the slave device and its args for a device
+# get_dm_ags $dm_config [vboot|vroot] args
+# Assumes we have only one slave device per device
+set_dm_slave() {
+  local dm=$1
+  local device=$2
+  local slave=$3
+  echo $(echo "${dm}" |
+    sed -nre "s#(.*${device}[^,]*,)([^,]*)(.*)#\1${slave}\3#p")
+}
+
+CALCULATED_KERNEL_CONFIG=
+CALCULATED_DM_ARGS=
+# Calculate rootfs hash of an image
+# Args: ROOTFS_IMAGE KERNEL_CONFIG HASH_IMAGE
+#
+# rootfs calculation parameters are grabbed from KERNEL_CONFIG
+#
+# Updated dm-verity arguments (to be replaced in kernel config command line)
+# with the new hash is stored in $CALCULATED_DM_ARGS and the new hash image is
+# written to the file HASH_IMAGE.
+calculate_rootfs_hash() {
+  local rootfs_image=$1
+  local kernel_config=$2
+  local hash_image=$3
+  local dm_config=$(get_dmparams_from_config "${kernel_config}")
+
+  if [ -z "${dm_config}" ]; then
+    warn "Couldn't grab dm_config. Aborting rootfs hash calculation."
+    return 1
+  fi
+  local vroot_dev=$(get_dm_slave "${dm_config}" vroot)
+
+  # Extract the key-value parameters from the kernel command line.
+  local rootfs_sectors=$(get_verity_arg "${vroot_dev}" hashstart)
+  local verity_algorithm=$(get_verity_arg "${vroot_dev}" alg)
+  local root_dev=$(get_verity_arg "${vroot_dev}" payload)
+  local hash_dev=$(get_verity_arg "${vroot_dev}" hashtree)
+  local salt=$(get_verity_arg "${vroot_dev}" salt)
+
+  local salt_arg
+  if [ -n "$salt" ]; then
+    salt_arg="salt=$salt"
+  fi
+
+  # Run the verity tool on the rootfs partition.
+  local slave=$(sudo verity mode=create \
+    alg=${verity_algorithm} \
+    payload="${rootfs_image}" \
+    payload_blocks=$((rootfs_sectors / 8)) \
+    hashtree="${hash_image}" ${salt_arg})
+  # Reconstruct new kernel config command line and replace placeholders.
+  slave="$(echo "${slave}" |
+    sed -s "s|ROOT_DEV|${root_dev}|g;s|HASH_DEV|${hash_dev}|")"
+  CALCULATED_DM_ARGS="$(set_dm_slave "${dm_config}" vroot "${slave}")"
+  CALCULATED_KERNEL_CONFIG="$(echo "${kernel_config}" |
+    sed -e 's#\(.*dm="\)\([^"]*\)\(".*\)'"#\1${CALCULATED_DM_ARGS}\3#g")"
+}
+
+# Re-calculate rootfs hash, update rootfs and kernel command line(s).
+# Args: LOOPDEV KERNEL KERN_A_KEYBLOCK KERN_A_PRIVKEY KERN_B_KEYBLOCK \
+#       KERN_B_PRIVKEY
+#
+# The rootfs is hashed by tool 'verity', and the hash data is stored after the
+# rootfs. A hash of those hash data (also known as final verity hash) may be
+# contained in kernel 2 or kernel 4 command line.
+#
+# This function reads dm-verity configuration from KERNEL, rebuilds the rootfs
+# hash, and then resigns kernel A & B by their keyblock and private key files.
+update_rootfs_hash() {
+  local loopdev="$1"  # Input image.
+  local loop_kern="$2"  # Kernel that contains verity args.
+  local kern_a_keyblock="$3"  # Keyblock file for kernel A.
+  local kern_a_privkey="$4"  # Private key file for kernel A.
+  local kern_b_keyblock="$5"  # Keyblock file for kernel B.
+  local kern_b_privkey="$6"  # Private key file for kernel A.
+  local loop_rootfs="${loopdev}p3"
+
+  # Note even though there are two kernels, there is one place (after rootfs)
+  # for hash data, so we must assume both kernel use same hash algorithm (i.e.,
+  # DM config).
+  info "Updating rootfs hash and updating config for Kernel partitions"
+
+  # If we can't find dm parameters in the kernel config, bail out now.
+  local kernel_config=$(sudo dump_kernel_config "${loop_kern}")
+  local dm_config=$(get_dmparams_from_config "${kernel_config}")
+  if [ -z "${dm_config}" ]; then
+    error "Couldn't grab dm_config from kernel ${loop_kern}"
+    error " (config: ${kernel_config})"
+    return 1
+  fi
+
+  # check and clear need_to_resign tag
+  local rootfs_dir=$(make_temp_dir)
+  sudo mount -o ro "${loop_rootfs}" "${rootfs_dir}"
+  if has_needs_to_be_resigned_tag "${rootfs_dir}"; then
+    # remount as RW
+    sudo mount -o remount,rw "${rootfs_dir}"
+    sudo rm -f "${rootfs_dir}/${TAG_NEEDS_TO_BE_SIGNED}"
+  fi
+  sudo umount "${rootfs_dir}"
+
+  local hash_image=$(make_temp_file)
+
+  # Disable rw mount support prior to hashing.
+  disable_rw_mount "${loop_rootfs}"
+
+  if ! calculate_rootfs_hash "${loop_rootfs}"  "${kernel_config}" \
+    "${hash_image}"; then
+    error "calculate_rootfs_hash failed!"
+    error "Aborting rootfs hash update!"
+    return 1
+  fi
+
+  local rootfs_blocks=$(sudo dumpe2fs "${loop_rootfs}" 2> /dev/null |
+    grep "Block count" |
+    tr -d ' ' |
+    cut -f2 -d:)
+  local rootfs_sectors=$((rootfs_blocks * 8))
+
+  # Overwrite the appended hashes in the rootfs
+  sudo dd if="${hash_image}" of="${loop_rootfs}" bs=512 \
+    seek=${rootfs_sectors} conv=notrunc 2>/dev/null
+
+  # Update kernel command lines
+  local dm_args="${CALCULATED_DM_ARGS}"
+  local temp_config=$(make_temp_file)
+  local kernelpart=
+  local keyblock=
+  local priv_key=
+  local new_kernel_config=
+
+  for kernelpart in 2 4; do
+    loop_kern="${loopdev}p${kernelpart}"
+    if ! new_kernel_config="$(
+         sudo dump_kernel_config "${loop_kern}" 2>/dev/null)" &&
+       [[ "${kernelpart}" == 4 ]]; then
+      # Legacy images don't have partition 4.
+      info "Skipping empty kernel partition 4 (legacy images)."
+      continue
+    fi
+    new_kernel_config="$(echo "${new_kernel_config}" |
+      sed -e 's#\(.*dm="\)\([^"]*\)\(".*\)'"#\1${dm_args}\3#g")"
+    info "New config for kernel partition ${kernelpart} is:"
+    echo "${new_kernel_config}" | tee "${temp_config}"
+    # Re-calculate kernel partition signature and command line.
+    if [[ "$kernelpart" == 2 ]]; then
+      keyblock="${kern_a_keyblock}"
+      priv_key="${kern_a_privkey}"
+    else
+      keyblock="${kern_b_keyblock}"
+      priv_key="${kern_b_privkey}"
+    fi
+    sudo vbutil_kernel --repack "${loop_kern}" \
+      --keyblock ${keyblock} \
+      --signprivate ${priv_key} \
+      --version "${KERNEL_VERSION}" \
+      --oldblob "${loop_kern}" \
+      --config ${temp_config}
+  done
+}
+
+# Update the SSD install-able vblock file on stateful partition.
+# ARGS: Loopdev
+# This is deprecated because all new images should have a SSD boot-able kernel
+# in partition 4. However, the signer needs to be able to sign new & old images
+# (crbug.com/449450#c13) so we will probably never remove this.
+update_stateful_partition_vblock() {
+  local loopdev="$1"
+  local temp_out_vb="$(make_temp_file)"
+
+  local loop_kern="${loopdev}p4"
+  if [[ -z "$(sudo dump_kernel_config "${loop_kern}" 2>/dev/null)" ]]; then
+    info "Building vmlinuz_hd.vblock from legacy image partition 2."
+    loop_kern="${loopdev}p2"
+  fi
+
+  # vblock should always use kernel keyblock.
+  sudo vbutil_kernel --repack "${temp_out_vb}" \
+    --keyblock "${KEY_DIR}/kernel.keyblock" \
+    --signprivate "${KEY_DIR}/kernel_data_key.vbprivk" \
+    --oldblob "${loop_kern}" \
+    --vblockonly
+
+  # Copy the installer vblock to the stateful partition.
+  local stateful_dir=$(make_temp_dir)
+  sudo mount "${loopdev}p1" "${stateful_dir}"
+  sudo cp ${temp_out_vb} ${stateful_dir}/vmlinuz_hd.vblock
+  sudo umount "${stateful_dir}"
+}
+
+# Do a sanity check on the image's rootfs
+# ARGS: Image
+verify_image_rootfs() {
+  local rootfs=$1
+  # This flips the read-only compatibility flag, so that e2fsck does not
+  # complain about unknown file system capabilities.
+  enable_rw_mount "${rootfs}"
+  info "Running e2fsck to check root file system for errors"
+  sudo e2fsck -fn "${rootfs}" ||
+    die "Root file system has errors!"
+  # Flip the bit back so we don't break hashes.
+  disable_rw_mount "${rootfs}"
+}
+
+# Extracts a firmware updater bundle (for firmware image binaries) file
+# (generated by src/platform/firmware/pack_firmware.sh).
+# Args: INPUT_FILE OUTPUT_DIR
+extract_firmware_bundle() {
+  local input="$(readlink -f "$1")"
+  local output_dir="$2"
+  if [ ! -s "${input}" ]; then
+    return 1
+  elif grep -q '^##CUTHERE##' "${input}"; then
+    # Bundle supports self-extraction.
+    "$input" --sb_extract "${output_dir}" ||
+      die "Extracting firmware autoupdate (--sb_extract) failed."
+  else
+    # Legacy bundle - try uudecode.
+    uudecode -o - ${input} | tar -C ${output_dir} -zxf - 2>/dev/null ||
+      die "Extracting firmware autoupdate failed."
+  fi
+}
+
+# Repacks firmware updater bundle content from given folder.
+# Args: INPUT_DIR TARGET_SCRIPT
+repack_firmware_bundle() {
+  local input_dir="$1"
+  local target="$(readlink -f "$2")"
+
+  if [ ! -s "${target}" ]; then
+    return 1
+  elif grep -q '^##CUTHERE##' "${target}"; then
+    # Bundle supports repacking.
+    # Workaround issue crosbug.com/p/33719
+    sed -i \
+      's/shar -Q -q -x -m -w/shar -Q -q -x -m --no-character-count/' \
+      "${target}"
+    "$target" --sb_repack "${input_dir}" ||
+      die "Updating firmware autoupdate (--sb_repack) failed."
+  else
+    # Legacy bundle using uuencode + tar.gz.
+    # Replace MD5 checksum in the firmware update payload.
+    local newfd_checksum="$(md5sum ${input_dir}/bios.bin | cut -f 1 -d ' ')"
+    local temp_version="$(make_temp_file)"
+    cat ${input_dir}/VERSION |
+    sed -e "s#\(.*\)\ \(.*bios.bin.*\)#${newfd_checksum}\ \2#" > ${temp_version}
+    mv ${temp_version} ${input_dir}/VERSION
+
+    # Re-generate firmware_update.tgz and copy over encoded archive in
+    # the original shell ball.
+    sed -ine '/^begin .*firmware_package/,/end/D' "$target"
+    tar zcf - -C "${input_dir}" . |
+      uuencode firmware_package.tgz >>"${target}"
+  fi
+}
+
+# Sign an update payload (usually created by paygen).
+# Args: HASH KEY_DIR OUTPUT
+# Depends on global variable KEY_ORIGIN.
+# <HASH> is supposed to be a SHA256 hash, unencoded, 32 bytes long.
+sign_update_payload() {
+  if [[ "${KEY_ORIGIN}" == "local" ]]; then
+    sign_update_payload_local "$@"
+  elif [[ "${KEY_ORIGIN}" == "kms" ]]; then
+    sign_update_payload_kms "$@"
+  else
+    die "Unsupported KEY_ORIGIN: ${KEY_ORIGIN}"
+  fi
+}
+
+sign_update_payload_local() {
+  local hash=$1
+  local key_dir=$2
+  local output=$3
+  local key_output key_size key_file="${key_dir}/update_key.pem"
+  # Maps key size to verified boot's algorithm id (for pad_digest_utility).
+  # Hashing algorithm is always SHA-256.
+  local algo algos=(
+    [1024]=1
+    [2048]=4
+    [4096]=7
+    [8192]=10
+  )
+
+  key_output=$(futility show "${key_file}")
+  key_size=$(echo "${key_output}" | sed -n '/Key length/s/[^0-9]*//p')
+  algo=${algos[${key_size}]}
+  if [[ -z ${algo} ]]; then
+    die "Unknown algorithm: futility output=${key_output}"
+  fi
+
+  pad_digest_utility ${algo} "${hash}" | \
+    openssl rsautl -sign -pkcs -inkey "${key_file}" -out "${output}"
+}
+
+# Signs a payload with a key stored in Cloud KMS.
+# $key_dir/kms.key must exist and must be a file with content in the
+# following format:
+#   KMS_PROJECT=<project>
+#   KMS_LOCATION=<location>
+#   KMS_KEYRING=<keyring>
+#   KMS_KEY=<key>
+#   KMS_KEYVERSION=<key version>
+sign_update_payload_kms() {
+  local -r hash="$1" key_dir="$2" output="$3"
+  local -r key_file="${key_dir}/kms.key"
+
+  source "${key_file}"
+
+  info "Signing update payload hash ${hash} with key ${key_file}"
+  kms_signer \
+    --project "${KMS_PROJECT}" \
+    --location "${KMS_LOCATION}" \
+    --keyring "${KMS_KEYRING}" \
+    --key "${KMS_KEY}" \
+    --key-version "${KMS_KEYVERSION}" \
+    digest \
+    --input "${hash}" \
+    --output "${output}"
+}
+
+# Sign UEFI binaries, if possible.
+# Args: LOOPDEV
+sign_uefi_binaries() {
+  local loopdev="$1"
+  local kms_option="--nokms"
+  if [[ "${KEY_ORIGIN}" == "kms" ]]; then
+    kms_option="--kms"
+  fi
+
+  local esp_dir
+  if ! esp_dir="$(mount_image_esp "${loopdev}")"; then
+    error "Could not mount EFI partition for signing UEFI binaries"
+    return 1
+  elif [[ -z "${esp_dir}" ]]; then
+    return 0
+  fi
+  "${SCRIPT_DIR}/sign_uefi.sh" -t "${esp_dir}"  -k "${KEY_DIR}" "${kms_option}"
+  sudo umount "${esp_dir}"
+
+  local rootfs_dir="$(make_temp_dir)"
+  mount_loop_image_partition "${loopdev}" 3 "${rootfs_dir}"
+  "${SCRIPT_DIR}/sign_uefi.sh" -t "${rootfs_dir}/boot" -k "${KEY_DIR}" "${kms_option}"
+  sudo umount "${rootfs_dir}"
+
+  info "Signed UEFI binaries"
+  return 0
+}
+
+# Verify the signatures of UEFI binaries.
+# Args: LOOPDEV
+verify_uefi_signatures() {
+  local loopdev="$1"
+  local succeeded=1
+
+  if [[ ! -d "${KEY_DIR}/uefi" ]]; then
+    return 0
+  fi
+
+  local esp_dir
+  if ! esp_dir="$(mount_image_esp "${loopdev}")"; then
+    error "Could not mount EFI partition for verifying UEFI signatures"
+    return 1
+  elif [[ -z "${esp_dir}" ]]; then
+    return 0
+  fi
+  "${SCRIPT_DIR}/verify_uefi.sh" "${esp_dir}" "${esp_dir}" \
+      "${KEY_DIR}/uefi" || succeeded=0
+
+  local rootfs_dir="$(make_temp_dir)"
+  mount_loop_image_partition_ro "${loopdev}" 3 "${rootfs_dir}"
+  "${SCRIPT_DIR}/verify_uefi.sh" "${rootfs_dir}/boot" "${esp_dir}" \
+      "${KEY_DIR}/uefi" || succeeded=0
+  sudo umount "${rootfs_dir}"
+
+  sudo umount "${esp_dir}"
+
+  if [[ "${succeeded}" == "0" ]]; then
+    die "UEFI signature verification failed"
+  fi
+}
+
+# Verify an image including rootfs hash using the specified keys.
+verify_image() {
+  local loopdev=$(loopback_partscan "${INPUT_IMAGE}")
+  local loop_rootfs="${loopdev}p3"
+
+  info "Verifying RootFS hash..."
+  # What we get from image.
+  local kernel_config
+  # What we calculate from the rootfs.
+  local new_kernel_config
+  # Depending on the type of image, the verity parameters may
+  # exist in either kernel partition 2 or kernel partition 4
+  local partnum
+  for partnum in 2 4; do
+    info "Considering Kernel partition ${partnum}"
+    kernel_config=$(sudo dump_kernel_config "${loopdev}p${partnum}")
+    local hash_image=$(make_temp_file)
+    if ! calculate_rootfs_hash "${loop_rootfs}" "${kernel_config}" \
+      "${hash_image}"; then
+      info "Trying next kernel partition."
+      continue
+    fi
+    new_kernel_config="$CALCULATED_KERNEL_CONFIG"
+    break
+  done
+
+  # Note: If calculate_rootfs_hash succeeded above, these should
+  # be non-empty.
+  expected_hash=$(get_hash_from_config "${new_kernel_config}")
+  got_hash=$(get_hash_from_config "${kernel_config}")
+
+  if [ -z "${expected_hash}" ] || [ -z "${got_hash}" ]; then
+    die "Couldn't verify RootFS hash on the image."
+  fi
+
+  if [ ! "${got_hash}" = "${expected_hash}" ]; then
+    cat <<EOF
+FAILED: RootFS hash is incorrect.
+Expected: ${expected_hash}
+Got: ${got_hash}
+EOF
+    exit 1
+  else
+    info "PASS: RootFS hash is correct (${expected_hash})"
+  fi
+
+  # Now try and verify kernel partition signature.
+  set +e
+  local try_key=${KEY_DIR}/recovery_key.vbpubk
+  info "Testing key verification..."
+  # The recovery key is only used in the recovery mode.
+  echo -n "With Recovery Key (Recovery Mode ON, Dev Mode OFF): " && \
+  { load_kernel_test "${INPUT_IMAGE}" "${try_key}" -b 2 >/dev/null 2>&1 && \
+    echo "YES"; } || echo "NO"
+  echo -n "With Recovery Key (Recovery Mode ON, Dev Mode ON): " && \
+  { load_kernel_test "${INPUT_IMAGE}" "${try_key}" -b 3 >/dev/null 2>&1 && \
+    echo "YES"; } || echo "NO"
+
+  try_key=${KEY_DIR}/kernel_subkey.vbpubk
+  # The SSD key is only used in non-recovery mode.
+  echo -n "With SSD Key (Recovery Mode OFF, Dev Mode OFF): " && \
+  { load_kernel_test "${INPUT_IMAGE}" "${try_key}" -b 0 >/dev/null 2>&1  && \
+    echo "YES"; } || echo "NO"
+  echo -n "With SSD Key (Recovery Mode OFF, Dev Mode ON): " && \
+  { load_kernel_test "${INPUT_IMAGE}" "${try_key}" -b 1 >/dev/null 2>&1 && \
+    echo "YES"; } || echo "NO"
+  set -e
+
+  verify_image_rootfs "${loop_rootfs}"
+
+  verify_uefi_signatures "${INPUT_IMAGE}"
+}
+
+# Update the legacy bootloader templates in EFI partition if available.
+# Args: LOOPDEV KERNEL
+update_legacy_bootloader() {
+  local loopdev="$1"
+  local loop_kern="$2"
+
+  local esp_dir
+  if ! esp_dir="$(mount_image_esp "${loopdev}")"; then
+    error "Could not mount EFI partition for updating legacy bootloader cfg."
+    return 1
+  elif [[ -z "${esp_dir}" ]]; then
+    info "Not updating legacy bootloader configs: ${loopdev}"
+    return 0
+  fi
+
+  # If we can't find the dm parameter in the kernel config, bail out now.
+  local kernel_config=$(sudo dump_kernel_config "${loop_kern}")
+  local root_hexdigest="$(get_hash_from_config "${kernel_config}")"
+  if [[ -z "${root_hexdigest}" ]]; then
+    error "Couldn't grab root_digest from kernel partition ${loop_kern}"
+    error " (config: ${kernel_config})"
+    return 1
+  fi
+  # Update syslinux configs for legacy BIOS systems.
+  if [[ -d "${esp_dir}/syslinux" ]]; then
+    local cfg=("${esp_dir}"/syslinux/*.cfg)
+    if ! sudo sed -i -r \
+      "s/\broot_hexdigest=[a-z0-9]+/root_hexdigest=${root_hexdigest}/g" \
+      "${cfg[@]}"; then
+        error "Updating syslinux configs failed: '${cfg[*]}'"
+        return 1
+    fi
+  fi
+  # Update grub configs for EFI systems.
+  local grub_cfg="${esp_dir}/efi/boot/grub.cfg"
+  if [[ -f "${grub_cfg}" ]]; then
+    if ! sudo sed -i -r \
+      "s/\broot_hexdigest=[a-z0-9]+/root_hexdigest=${root_hexdigest}/g" \
+      "${grub_cfg}"; then
+        error "Updating grub config failed: '${grub_cfg}'"
+        return 1
+    fi
+  fi
+}
+
+# Sign an image file with proper keys.
+# Args: IMAGE_TYPE INPUT OUTPUT DM_PARTNO KERN_A_KEYBLOCK KERN_A_PRIVKEY \
+#       KERN_B_KEYBLOCK KERN_B_PRIVKEY
+#
+# A ChromiumOS image file (INPUT) always contains 2 partitions (kernel A & B).
+# This function will rebuild hash data by DM_PARTNO, resign kernel partitions by
+# their KEYBLOCK and PRIVKEY files, and then write to OUTPUT file. Note some
+# special images (specified by IMAGE_TYPE, like 'recovery' or 'factory_install')
+# may have additional steps (ex, tweaking verity hash or not stripping files)
+# when generating output file.
+sign_image_file() {
+  local image_type="$1"
+  local input="$2"
+  local output="$3"
+  local dm_partno="$4"
+  local kernA_keyblock="$5"
+  local kernA_privkey="$6"
+  local kernB_keyblock="$7"
+  local kernB_privkey="$8"
+
+  info "Preparing ${image_type} image..."
+  cp --sparse=always "${input}" "${output}"
+
+  local loopdev=$(loopback_partscan "${output}")
+  local loop_kern="${loopdev}p${dm_partno}"
+  local loop_rootfs="${loopdev}p3"
+
+  sign_uefi_binaries "${loopdev}"
+  # We do NOT strip /boot for factory installer, since some devices need it to
+  # boot EFI. crbug.com/260512 would obsolete this requirement.
+  #
+  # We also do NOT strip /boot for legacy BIOS or EFI devices.  This is because
+  # "cros_installer postinst" on BIOS or EFI systems relies on presence of
+  # /boot in rootfs to update kernel.  We infer the BIOS type from the kernel
+  # config.
+  local loop_kerna="${loopdev}p2"
+  local kerna_config="$(sudo dump_kernel_config "${loop_kerna}")"
+  if [[ "${image_type}" != "factory_install" &&
+        " ${kerna_config} " != *" cros_legacy "* &&
+        " ${kerna_config} " != *" cros_efi "* ]]; then
+    "${SCRIPT_DIR}/strip_boot_from_image.sh" --image "${loop_rootfs}"
+  fi
+  update_rootfs_hash "${loopdev}" "${loop_kern}" \
+    "${kernA_keyblock}" "${kernA_privkey}" \
+    "${kernB_keyblock}" "${kernB_privkey}"
+  update_stateful_partition_vblock "${loopdev}"
+  if ! update_legacy_bootloader "${loopdev}" "${loop_kern}"; then
+    # Error is already logged.
+    return 1
+  fi
+  # Let non-root users read it. It's okay.
+  sudo chmod 0644 "${output}"
+  info "Signed ${image_type} image output to ${output}"
+}
+
+# Verification
+case ${TYPE} in
+dump_config)
+  check_argc $# 2
+  loopdev=$(loopback_partscan "${INPUT_IMAGE}")
+  for partnum in 2 4; do
+    info "kernel config in partition number ${partnum}:"
+    sudo dump_kernel_config "${loopdev}p${partnum}"
+    echo
+  done
+  exit 0
+  ;;
+verify)
+  check_argc $# 2
+  verify_image
+  exit 0
+  ;;
+*)
+  # All other signing commands take 4 to 5 args.
+  if [ -z "${OUTPUT_IMAGE}" ]; then
+    # Friendlier message.
+    usage "Missing output image name"
+  fi
+  check_argc $# 4 5
+  ;;
+esac
+
+# If a version file was specified, read the firmware and kernel
+# versions from there.
+if [ -n "${VERSION_FILE}" ]; then
+  FIRMWARE_VERSION=$(sed -n 's#^firmware_version=\(.*\)#\1#pg' ${VERSION_FILE})
+  KERNEL_VERSION=$(sed -n 's#^kernel_version=\(.*\)#\1#pg' ${VERSION_FILE})
+fi
+info "Using firmware version: ${FIRMWARE_VERSION}"
+info "Using kernel version: ${KERNEL_VERSION}"
+
+# Make all modifications on output copy.
+if [[ "${TYPE}" == "base" ]]; then
+  sign_image_file "SSD" "${INPUT_IMAGE}" "${OUTPUT_IMAGE}" 2 \
+    "${KEY_DIR}/kernel.keyblock" "${KEY_DIR}/kernel_data_key.vbprivk" \
+    "${KEY_DIR}/kernel.keyblock" "${KEY_DIR}/kernel_data_key.vbprivk"
+elif [[ "${TYPE}" == "update_payload" ]]; then
+  # The argument names here are a little awkard because sign_update_payload
+  # doesn't sign "image" but only signs hashes, but we want to use the same
+  # interface as sign_image_file, so ...
+  sign_update_payload ${INPUT_IMAGE} ${KEY_DIR} ${OUTPUT_IMAGE}
+else
+  die "Invalid type ${TYPE}"
+fi