| # Copyright 2019 Google Inc. All Rights Reserved. |
| # |
| # Licensed under the Apache License, Version 2.0 (the "License"); |
| # you may not use this file except in compliance with the License. |
| # You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, software |
| # distributed under the License is distributed on an "AS-IS" BASIS, |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| # See the License for the specific language governing permissions and |
| # limitations under the License. |
| """A command-line utility for checking file integrity with a MAC. |
| |
| It loads cleartext keys from disk - this is not recommended! |
| |
| It requires 2 or 3 arguments: |
| keyset-file: name of the file with the keyset to be used for the MAC |
| data-file: name of the file with the input data to be checked |
| [optional] expected-code-file: name of the file containing a hexadecimal MAC |
| with which to compare the MAC of the input data |
| If expected-code-file is supplied, the program will print whether the MACs |
| matched or not. If not, it will just print the hexadecimal MAC of the data file. |
| """ |
| |
| from __future__ import absolute_import |
| from __future__ import division |
| from __future__ import google_type_annotations |
| from __future__ import print_function |
| |
| import binascii |
| |
| # Special imports |
| from absl import app |
| from absl import flags |
| from absl import logging |
| import tink |
| |
| FLAGS = flags.FLAGS |
| |
| |
| def main(argv): |
| if len(argv) not in (3, 4): |
| raise app.UsageError( |
| 'Expected 2 or 3 arguments, got %d.\n' |
| 'Usage: %s keyset-file data-file [expected-code-file]' % |
| (len(argv) - 1, argv[0])) |
| |
| keyset_filename = argv[1] |
| data_filename = argv[2] |
| expected_code_filename = argv[3] if len(argv) == 4 else None |
| |
| if expected_code_filename is not None: |
| with open(expected_code_filename, 'rb') as expected_code_file: |
| expected_code_hex = expected_code_file.read().strip() |
| |
| logging.info( |
| 'Using keyset from file %s to verify file %s against expected code %s', |
| keyset_filename, data_filename, expected_code_hex.decode('utf-8')) |
| else: |
| expected_code_hex = None |
| logging.info('Using keyset from file %s to verify file %s', keyset_filename, |
| data_filename) |
| |
| # Initialise Tink. |
| try: |
| tink.tink_config.register() |
| except tink.TinkError as e: |
| logging.error('Error initialising Tink: %s', e) |
| return 1 |
| |
| # Read the keyset. |
| with open(keyset_filename, 'rb') as keyset_file: |
| try: |
| text = keyset_file.read() |
| keyset = tink.KeysetHandle(tink.JsonKeysetReader(text).read()) |
| except tink.TinkError as e: |
| logging.error('Error reading key: %s', e) |
| return 1 |
| |
| # Get the primitive. |
| try: |
| cipher = keyset.primitive(tink.Mac) |
| except tink.TinkError as e: |
| logging.error('Error creating primitive: %s', e) |
| return 1 |
| |
| # Compute the MAC. |
| with open(data_filename, 'rb') as data_file: |
| data = data_file.read() |
| |
| if expected_code_hex is None: |
| code = cipher.compute_mac(data) |
| logging.info('MAC output is %s', binascii.hexlify(code).decode('utf-8')) |
| return 0 |
| |
| try: |
| expected_code = binascii.unhexlify(expected_code_hex) |
| except binascii.Error as e: |
| logging.error('Error reading expected code: %s', e) |
| return 1 |
| |
| try: |
| cipher.verify_mac(expected_code, data) |
| logging.info('MAC outputs matched. Success!') |
| return 0 |
| except tink.TinkError as e: |
| logging.info('MAC outputs did not match!') |
| code = binascii.hexlify(cipher.compute_mac(data)).decode('utf-8') |
| logging.info('Actual MAC output is %s', code) |
| return 1 |
| |
| |
| if __name__ == '__main__': |
| app.run(main) |