Issue 6821: script to verify rootfs integrity against value stored in kernel

Change-Id: I09b851e5b9e971c281305802f287fe93e9309fe8

BUG=chromium-os:6821
TEST=manually ran script inside chroot for both a USB device and a dev build
of Chrome OS image. USB image has corrupted rootfs and dev build does not. The
script was able to detect both scenarios correctly.

Review URL: http://codereview.chromium.org/3452013

verify_rootfs_chksum.sh

@@ -0,0 +1,100 @@
+#!/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.
+
+# Script to verify integrity of root file system for a GPT-based image
+
+# Load functions and constants
+. "$(dirname "$0")/common.sh" || exit 1
+. "$(dirname "$0")/chromeos-common.sh" || exit 1
+
+# Needed for partoffset and partsize calls
+locate_gpt
+
+# Script must be run inside the chroot.
+restart_in_chroot_if_needed $*
+
+DEFINE_string image "" "Device or an image path. Default: (empty)."
+
+# Parse command line.
+FLAGS "$@" || exit 1
+eval set -- "${FLAGS_ARGV}"
+
+if [ -z $FLAGS_image ] ; then
+  die "Use --from to specify a device or an image file."
+fi
+
+# Turn path into an absolute path.
+FLAGS_image=$(eval readlink -f ${FLAGS_image})
+
+# Abort early if we can't find the image
+if [ ! -b ${FLAGS_image} ] && [ ! -f $FLAGS_image ] ; then
+  die "No image found at $FLAGS_image"
+fi
+
+set -e
+
+function get_partitions() {
+  if [ -b ${FLAGS_image} ] ; then
+    KERNEL_IMG=$(make_partition_dev "${FLAGS_image}" 2)
+    ROOTFS_IMG=$(make_partition_dev "${FLAGS_image}" 3)
+    return
+  fi
+
+  KERNEL_IMG=$(mktemp)
+  ROOTFS_IMG=$(mktemp)
+  local kernel_offset=$(partoffset "${FLAGS_image}" 2)
+  local kernel_count=$(partsize "${FLAGS_image}" 2)
+  local rootfs_offset=$(partoffset "${FLAGS_image}" 3)
+  local rootfs_count=$(partsize "${FLAGS_image}" 3)
+
+  # TODO(tgao): use loop device to save 1GB in temp space
+  dd if="${FLAGS_image}" of=${KERNEL_IMG} bs=512 skip=${kernel_offset} \
+      count=${kernel_count} &>/dev/null
+  dd if="${FLAGS_image}" of=${ROOTFS_IMG} bs=512 skip=${rootfs_offset} \
+      count=${rootfs_count} &>/dev/null
+}
+
+function cleanup() {
+  for i in ${KERNEL_IMG} ${ROOTFS_IMG}
+  do
+    if [ ! -b ${i} ]; then
+      rm -f ${i}
+    fi
+  done
+}
+
+get_partitions
+
+# Logic below extracted from src/platform/installer/chromeos-setimage
+DUMP_KERNEL_CONFIG=/usr/bin/dump_kernel_config
+KERNEL_CONFIG=$(sudo "${DUMP_KERNEL_CONFIG}" "${KERNEL_IMG}")
+kernel_cfg="$(echo "${KERNEL_CONFIG}" | sed -e 's/.*dm="\([^"]*\)".*/\1/g' |
+              cut -f2- -d,)"
+rootfs_sectors=$(echo ${kernel_cfg} | cut -f2 -d' ')
+verity_depth=$(echo ${kernel_cfg} | cut -f7 -d' ')
+verity_algorithm=$(echo ${kernel_cfg} | cut -f8 -d' ')
+
+# Compute the rootfs hash tree
+VERITY=/bin/verity
+table="vroot none ro,"$(sudo "${VERITY}" create \
+        ${verity_depth} \
+        "${verity_algorithm}" \
+        "${ROOTFS_IMG}" \
+        $((rootfs_sectors / 8)) \
+        /dev/null)
+
+expected_hash=$(echo ${kernel_cfg} | cut -f9 -d' ')
+generated_hash=$(echo ${table} | cut -f2- -d, | cut -f9 -d' ')
+
+cleanup
+
+if [ "${expected_hash}" != "${generated_hash}" ]; then
+  warn "expected hash = ${expected_hash}"
+  warn "actual hash = ${generated_hash}"
+  die "Root filesystem has been modified unexpectedly!"
+else
+  info "Root filesystem checksum match!"
+fi