Add a customize_image script.

scripts/image_signing/customize_image

+#!/bin/bash
+
+# Copyright (c) 2010 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.
+
+# Customize a Chrome OS release image. The cgpt utility must be on the
+# sudo path.
+#
+# The following changes are applied:
+# - Set the root password.
+
+# Usage: ./customize_image <image.bin> <root_password>
+
+readonly ROOTFS_DIR=$(mktemp -d)
+readonly GPT=cgpt
+
+cleanup() {
+  set +e
+  echo Cleaning up...
+  sudo umount -d "$ROOTFS_DIR"
+  rm -rf "$ROOTFS_DIR"
+}
+
+failure() {
+  cleanup
+  exit 1
+}
+
+# Read GPT table to find the starting location of a specific partition.
+# Args: DEVICE PARTNUM
+# Returns: offset (in sectors) of partition PARTNUM
+partoffset() {
+  sudo $GPT show -b -i $2 $1
+}
+
+mount_image() {
+  local image=$1
+  echo "Mounting image '$image'..."
+  local offset=$(partoffset "$image" 3)
+  sudo mount -o loop,offset=$((offset * 512)) "$image" "$ROOTFS_DIR"
+}
+
+change_root_password() {
+  local password=$1
+  echo "Changing root password to '$password'..."
+  local crypted_password="$(echo $password | openssl passwd -1 -stdin)"
+  local temp_shadow="$ROOTFS_DIR/etc/tempshadow"
+  echo "root:$crypted_password:14500:0:::::" \
+    | sudo tee "$temp_shadow" > /dev/null
+  grep -Ev ^root: "$ROOTFS_DIR/etc/shadow" \
+    | sudo tee -a "$temp_shadow" > /dev/null
+  sudo mv -f "$temp_shadow" "$ROOTFS_DIR/etc/shadow"
+}
+
+main() {
+  local image=$1
+  local root_password=$2
+  if [ $# -ne 2 ]; then
+    echo "Usage: $0 <image.bin> <root_password>"
+    exit 1
+  fi
+
+  set -e
+  trap failure EXIT
+  mount_image "$image"
+  change_root_password "$root_password"
+  cleanup
+  echo "Done."
+  trap - EXIT
+}
+
+main $@