scripts/image_signing/make_dev_ssd.sh

#!/bin/sh
#
# Copyright (c) 2012 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.
#
# This script can change key (usually developer keys) and kernel config
# of kernels on an disk image (usually for SSD but also works for USB).

SCRIPT_BASE="$(dirname "$0")"
. "$SCRIPT_BASE/common_minimal.sh"
load_shflags || exit 1

# Constants used by DEFINE_*
VBOOT_BASE='/usr/share/vboot'
DEFAULT_KEYS_FOLDER="$VBOOT_BASE/devkeys"
DEFAULT_BACKUP_FOLDER='/mnt/stateful_partition/backups'
DEFAULT_PARTITIONS='2 4'

# TODO(hungte) The default image selection is no longer a SSD, so the script
# works more like "make_dev_image".  We may change the file name in future.
ROOTDEV="$(rootdev -s 2>/dev/null)"
ROOTDEV_PARTITION="$(echo $ROOTDEV | sed -n 's/.*\([0-9][0-9]*\)$/\1/p')"
ROOTDEV_DISK="$(rootdev -s -d 2>/dev/null)"
ROOTDEV_KERNEL="$((ROOTDEV_PARTITION - 1))"

# DEFINE_string name default_value description flag
DEFINE_string image "$ROOTDEV_DISK" "Path to device or image file" "i"
DEFINE_string keys "$DEFAULT_KEYS_FOLDER" "Path to folder of dev keys" "k"
DEFINE_boolean remove_rootfs_verification \
  $FLAGS_FALSE "Modify kernel boot config to disable rootfs verification" ""
DEFINE_string backup_dir \
  "$DEFAULT_BACKUP_FOLDER" "Path of directory to store kernel backups" ""
DEFINE_string save_config "" \
  "Base filename to store kernel configs to, instead of resigning." ""
DEFINE_string set_config "" \
  "Base filename to load kernel configs from" ""
DEFINE_string partitions "" \
  "List of partitions to examine (default: $DEFAULT_PARTITIONS)" ""
DEFINE_boolean recovery_key "$FLAGS_FALSE" \
 "Use recovery key to sign image (to boot from USB" ""
DEFINE_boolean force "$FLAGS_FALSE" "Skip sanity checks and make the change" "f"

# Parse command line
FLAGS "$@" || exit 1
ORIGINAL_PARAMS="$@"
eval set -- "$FLAGS_ARGV"
ORIGINAL_PARTITIONS="$FLAGS_partitions"
: ${FLAGS_partitions:=$DEFAULT_PARTITIONS}

# Globals
# ----------------------------------------------------------------------------
set -e

# a log file to keep the output results of executed command
EXEC_LOG="$(make_temp_file)"

# Functions
# ----------------------------------------------------------------------------

# Removes rootfs verification from kernel boot parameter
remove_rootfs_verification() {
  local new_root="PARTUUID=%U/PARTNROFF=1"
  echo "$*" | sed '
    s| root=/dev/dm-[0-9] | root='"$new_root"' |
    s| dm_verity[^=]*=[-0-9]*||g
    s| dm="[^"]*"||
    s| ro | rw |'
}

remove_legacy_boot_rootfs_verification() {
  # See src/scripts/create_legacy_bootloader_templates
  local image="$1"
  local mount_point="$(make_temp_dir)"
  local config_file
  debug_msg "Removing rootfs verification for legacy boot configuration."
  mount_image_partition "$image" 12 "$mount_point" || return $FLAGS_FALSE
  config_file="$mount_point/efi/boot/grub.cfg"
  [ ! -f "$config_file" ] ||
    sudo sed -i 's/^ *set default=2 *$/set default=0/g' "$config_file"
  config_file="$mount_point/syslinux/default.cfg"
  [ ! -f "$config_file" ] ||
    sudo sed -i 's/-vusb/-usb/g; s/-vhd/-hd/g' "$config_file"
  sudo umount "$mount_point"
}

# Wrapped version of dd
mydd() {
  # oflag=sync is safer, but since we need bs=512, syncing every block would be
  # very slow.
  dd "$@" >"$EXEC_LOG" 2>&1 ||
    err_die "Failed in [dd $@], Message: $(cat "$EXEC_LOG")"
}

# Prints a more friendly name from kernel index number
cros_kernel_name() {
  case $1 in
    2)
      echo "Kernel A"
      ;;
    4)
      echo "Kernel B"
      ;;
    6)
      echo "Kernel C"
      ;;
    *)
      echo "Partition $1"
  esac
}

find_valid_kernel_partitions() {
  local part_id
  local valid_partitions=""
  for part_id in $*; do
    local name="$(cros_kernel_name $part_id)"
    local kernel_part="$(make_partition_dev "$FLAGS_image" "$part_id")"
    if [ -z "$(dump_kernel_config "$kernel_part" 2>"$EXEC_LOG")" ]; then
      echo "INFO: $name: no kernel boot information, ignored." >&2
    else
      [ -z "$valid_partitions" ] &&
        valid_partitions="$part_id" ||
        valid_partitions="$valid_partitions $part_id"
      continue
    fi
  done
  debug_msg "find_valid_kernel_partitions: [$*] -> [$valid_partitions]"
  echo "$valid_partitions"
}

# Resigns a kernel on SSD or image.
resign_ssd_kernel() {
  # bs=512 is the fixed block size for dd and cgpt
  local bs=512
  local ssd_device="$1"

  # reasonable size for current kernel partition
  local min_kernel_size=32000
  local max_kernel_size=65536
  local resigned_kernels=0

  for kernel_index in $FLAGS_partitions; do
    local old_blob="$(make_temp_file)"
    local new_blob="$(make_temp_file)"
    local name="$(cros_kernel_name $kernel_index)"
    local rootfs_index="$(($kernel_index + 1))"

    debug_msg "Probing $name information"
    local offset size
    offset="$(partoffset "$ssd_device" "$kernel_index")" ||
      err_die "Failed to get partition $kernel_index offset from $ssd_device"
    size="$(partsize "$ssd_device" "$kernel_index")" ||
      err_die "Failed to get partition $kernel_index size from $ssd_device"
    if [ ! $size -gt $min_kernel_size ]; then
      echo "INFO: $name seems too small ($size), ignored."
      continue
    fi
    if [ ! $size -le $max_kernel_size ]; then
      echo "INFO: $name seems too large ($size), ignored."
      continue
    fi

    debug_msg "Reading $name from partition $kernel_index"
    mydd if="$ssd_device" of="$old_blob" bs=$bs skip=$offset count=$size

    debug_msg "Checking if $name is valid"
    local kernel_config
    if ! kernel_config="$(dump_kernel_config "$old_blob" 2>"$EXEC_LOG")"; then
      debug_msg "dump_kernel_config error message: $(cat "$EXEC_LOG")"
      echo "INFO: $name: no kernel boot information, ignored."
      continue
    fi

    if [ -n "${FLAGS_save_config}" ]; then
      # Save current kernel config
      local old_config_file
      old_config_file="${FLAGS_save_config}.$kernel_index"
      echo "Saving $name config to $old_config_file"
      echo "$kernel_config" > "$old_config_file"
      # Just save; don't resign
      continue
    fi

    if [ -n "${FLAGS_set_config}" ]; then
      # Set new kernel config from file
      local new_config_file
      new_config_file="${FLAGS_set_config}.$kernel_index"
      kernel_config="$(cat "$new_config_file")" ||
        err_die "Failed to read new kernel config from $new_config_file"
      debug_msg "New kernel config: $kernel_config)"
      echo "$name: Replaced config from $new_config_file"
    fi

    if [ ${FLAGS_remove_rootfs_verification} = $FLAGS_FALSE ]; then
      debug_msg "Bypassing rootfs verification check"
    else
      debug_msg "Changing boot parameter to remove rootfs verification"
      kernel_config="$(remove_rootfs_verification "$kernel_config")"
      debug_msg "New kernel config: $kernel_config"
      echo "$name: Disabled rootfs verification."
      remove_legacy_boot_rootfs_verification "$ssd_device"
    fi

    local new_kernel_config_file="$(make_temp_file)"
    echo -n "$kernel_config"  >"$new_kernel_config_file"

    debug_msg "Re-signing $name from $old_blob to $new_blob"
    debug_msg "Using key: $KERNEL_DATAKEY"
    vbutil_kernel \
      --repack "$new_blob" \
      --keyblock "$KERNEL_KEYBLOCK" \
      --config "$new_kernel_config_file" \
      --signprivate "$KERNEL_DATAKEY" \
      --oldblob "$old_blob" >"$EXEC_LOG" 2>&1 ||
      err_die "Failed to resign $name. Message: $(cat "$EXEC_LOG")"

    debug_msg "Creating new kernel image (vboot+code+config)"
    local new_kern="$(make_temp_file)"
    cp "$old_blob" "$new_kern"
    mydd if="$new_blob" of="$new_kern" conv=notrunc

    if is_debug_mode; then
      debug_msg "for debug purposes, check *.dbgbin"
      cp "$old_blob" old_blob.dbgbin
      cp "$new_blob" new_blob.dbgbin
      cp "$new_kern" new_kern.dbgbin
    fi

    debug_msg "Verifying new kernel and keys"
    vbutil_kernel \
      --verify "$new_kern" \
      --signpubkey "$KERNEL_PUBKEY" --verbose >"$EXEC_LOG" 2>&1 ||
      err_die "Failed to verify new $name. Message: $(cat "$EXEC_LOG")"

    debug_msg "Backup old kernel blob"
    local backup_date_time="$(date +'%Y%m%d_%H%M%S')"
    local backup_name="$(echo "$name" | sed 's/ /_/g; s/^K/k/')"
    local backup_file_name="${backup_name}_${backup_date_time}.bin"
    local backup_file_path="$FLAGS_backup_dir/$backup_file_name"
    if mkdir -p "$FLAGS_backup_dir" &&
      cp -f "$old_blob" "$backup_file_path"; then
      echo "Backup of $name is stored in: $backup_file_path"
    else
      echo "WARNING: Cannot create file in $FLAGS_backup_dir... Ignore backups."
    fi

    debug_msg "Writing $name to partition $kernel_index"
    mydd \
      if="$new_kern" \
      of="$ssd_device" \
      seek=$offset \
      bs=$bs \
      count=$size \
      conv=notrunc
    resigned_kernels=$(($resigned_kernels + 1))

    debug_msg "Make the root file system writable if needed."
    # TODO(hungte) for safety concern, a more robust way would be to:
    # (1) change kernel config to ro
    # (2) check if we can enable rw mount
    # (3) change kernel config to rw
    if [ ${FLAGS_remove_rootfs_verification} = $FLAGS_TRUE ]; then
      local root_offset_sector=$(partoffset "$ssd_device" $rootfs_index)
      local root_offset_bytes=$((root_offset_sector * 512))
      if ! is_ext2 "$ssd_device" "$root_offset_bytes"; then
        debug_msg "Non-ext2 partition: $ssd_device$rootfs_index, skip."
      elif ! rw_mount_disabled "$ssd_device" "$root_offset_bytes"; then
        debug_msg "Root file system is writable. No need to modify."
      else
        # disable the RO ext2 hack
        debug_msg "Disabling rootfs ext2 RO bit hack"
        enable_rw_mount "$ssd_device" "$root_offset_bytes" >"$EXEC_LOG" 2>&1 ||
          err_die "Failed turning off rootfs RO bit. OS may be corrupted. " \
                  "Message: $(cat "$EXEC_LOG")"
      fi
    fi

    # Sometimes doing "dump_kernel_config" or other I/O now (or after return to
    # shell) will get the data before modification. Not a problem now, but for
    # safety, let's try to sync more.
    sync; sync; sync

    echo "$name: Re-signed with developer keys successfully."
  done

  # If we saved the kernel config, exit now so we don't print an error
  if [ -n "${FLAGS_save_config}" ]; then
    echo "(Kernels have not been resigned.)"
    exit 0
  fi

  return $resigned_kernels
}

sanity_check_live_partitions() {
  debug_msg "Partition sanity check"
  if [ "$FLAGS_partitions" = "$ROOTDEV_KERNEL" ]; then
    debug_msg "only for current active partition - safe."
    return
  fi
  if [ "$ORIGINAL_PARTITIONS" != "" ]; then
    debug_msg "user has assigned partitions - provide more info."
    echo "INFO: Making change to $FLAGS_partitions on $FLAGS_image."
    return
  fi
  echo "
  ERROR: YOU ARE TRYING TO MODIFY THE LIVE SYSTEM IMAGE $FLAGS_image.

  The system may become unusable after that change, especially when you have
  some auto updates in progress. To make it safer, we suggest you to only
  change the partition you have booted with. To do that, re-execute this command
  as:

    sudo ./make_dev_ssd.sh $ORIGINAL_PARAMS --partitions $ROOTDEV_KERNEL

  If you are sure to modify other partition, please invoke the command again and
  explicitly assign only one target partition for each time  (--partitions N )
  "
  return $FLAGS_FALSE
}

sanity_check_live_firmware() {
  debug_msg "Firmware compatibility sanity check"
  if [ "$(crossystem mainfw_type)" = "developer" ]; then
    debug_msg "developer type firmware in active."
    return
  fi
  debug_msg "Loading firmware to check root key..."
  local bios_image="$(make_temp_file)"
  local rootkey_file="$(make_temp_file)"
  echo "INFO: checking system firmware..."
  sudo flashrom -p host -i GBB -r "$bios_image" >/dev/null 2>&1
  gbb_utility -g --rootkey="$rootkey_file" "$bios_image" >/dev/null 2>&1
  if [ ! -s "$rootkey_file" ]; then
    debug_msg "failed to read root key from system firmware..."
  else
    # The magic 130 is counted by "od dev-rootkey" for the lines until the body
    # of key is reached. Trailing bytes (0x00 or 0xFF - both may appear, and
    # that's why we need to skip them) are started at line 131.
    # TODO(hungte) compare with rootkey in $VBOOT_BASE directly.
    local rootkey_hash="$(od "$rootkey_file" |
                          head -130 | md5sum |
                          sed 's/ .*$//' )"
    if [ "$rootkey_hash" = "a13642246ef93daaf75bd791446fec9b" ]; then
      debug_msg "detected DEV root key in firmware."
      return
    else
      debug_msg "non-devkey hash: $rootkey_hash"
    fi
  fi

  echo "
  ERROR: YOU ARE NOT USING DEVELOPER FIRMWARE, AND RUNNING THIS COMMAND MAY
  THROW YOUR CHROMEOS DEVICE INTO UN-BOOTABLE STATE.

  You need to either install developer firmware, or change system root key.

   - To install developer firmware: type command
     sudo chromeos-firmwareupdate --mode=todev

   - To change system rootkey: disable firmware write protection (a hardware
     switch) and then type command:
     sudo ./make_dev_firmware.sh

  If you are sure that you want to make such image without developer
  firmware or you've already changed system root keys, please run this
  command again with --force paramemeter:

     sudo ./make_dev_ssd.sh --force $ORIGINAL_PARAMS
  "
  return $FLAGS_FALSE
}

# Main
# ----------------------------------------------------------------------------
main() {
  local num_signed=0
  local num_given=$(echo "$FLAGS_partitions" | wc -w)
  # Check parameters
  if [ "$FLAGS_recovery_key" = "$FLAGS_TRUE" ]; then
    KERNEL_KEYBLOCK="$FLAGS_keys/recovery_kernel.keyblock"
    KERNEL_DATAKEY="$FLAGS_keys/recovery_kernel_data_key.vbprivk"
    KERNEL_PUBKEY="$FLAGS_keys/recovery_key.vbpubk"
  else
    KERNEL_KEYBLOCK="$FLAGS_keys/kernel.keyblock"
    KERNEL_DATAKEY="$FLAGS_keys/kernel_data_key.vbprivk"
    KERNEL_PUBKEY="$FLAGS_keys/kernel_subkey.vbpubk"
  fi

  debug_msg "Prerequisite check"
  ensure_files_exist \
    "$KERNEL_KEYBLOCK" \
    "$KERNEL_DATAKEY" \
    "$KERNEL_PUBKEY" \
    "$FLAGS_image" ||
    exit 1

  # checks for running on a live system image.
  if [ "$FLAGS_image" = "$ROOTDEV_DISK" ]; then
    debug_msg "check valid kernel partitions for live system"
    local valid_partitions="$(find_valid_kernel_partitions $FLAGS_partitions)"
    [ -n "$valid_partitions" ] ||
      err_die "No valid kernel partitions on $FLAGS_image ($FLAGS_partitions)."
    FLAGS_partitions="$valid_partitions"

    # Sanity checks
    if [ "$FLAGS_force" = "$FLAGS_TRUE" ]; then
      echo "
      !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
      ! INFO: ALL SANITY CHECKS WERE BYPASSED. YOU ARE ON YOUR OWN. !
      !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
      " >&2
      local i
      for i in $(seq 5 -1 1); do
        echo -n "\rStart in $i second(s) (^C to abort)...  " >&2
        sleep 1
      done
      echo ""
    elif ! sanity_check_live_firmware ||
         ! sanity_check_live_partitions; then
      err_die "IMAGE $FLAGS_image IS NOT MODIFIED."
    fi
  fi

  resign_ssd_kernel "$FLAGS_image" || num_signed=$?

  debug_msg "Complete."
  if [ $num_signed -gt 0 -a $num_signed -le $num_given ]; then
    # signed something at least
    echo "Successfully re-signed $num_signed of $num_given kernel(s)" \
      " on device $FLAGS_image".
  else
    err_die "Failed re-signing kernels."
  fi
}

# People using this to process images may forget to add "-i",
# so adding parameter check is safer.
if [ "$#" -gt 0 ]; then
  flags_help
  err_die "Unknown parameters: $@"
fi

main