#!/bin/sh
#
# Copyright 2021 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.

set -e

# Flag file indicating that a TPM firmware update has been requested.
TPM_FIRMWARE_UPDATE_REQUEST=/mnt/stateful_partition/unencrypted/preserve/tpm_firmware_update_request

# Verifies that the TPM is in good state after updating. When performing an
# owner-authorized TPM firmware update, the previous SRK remains. Since that SRK
# might be weak we can't allow for it to stick around. The updater generally
# requests the TPM to be cleared after updating, but there are edge cases
# (interrupted updates, TPM firmware bugs that prevent the update from
# completing successfully) for which we might reboot in normal mode without the
# TPM having been cleared. As a safety net to handle these cases we check that
# the TPM is cleared and if not request another clear here.
cleanup() {
  if [ "$(tpmc getownership)" != "Owned: no" ]; then
    crossystem clear_tpm_owner_request=1
    reboot
    sleep infinity
  fi

  # Looking good, don't trigger the TPM updater again after reboot.
  rm "${TPM_FIRMWARE_UPDATE_REQUEST}"
}

main() {
  if [ ! -e "${TPM_FIRMWARE_UPDATE_REQUEST}" ]; then
    return 0
  fi

  local mode="$(cat "${TPM_FIRMWARE_UPDATE_REQUEST}")"
  if [ "$mode" = "cleanup" ]; then
    cleanup
  fi
}

main "$@"