testing/cross_language/mac_test.py

# Copyright 2020 Google LLC
#
# 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.
"""Cross-language tests for the MAC primitive."""

from typing import Iterable, Tuple

from absl.testing import absltest
from absl.testing import parameterized

import tink
from tink import mac

from tink.proto import tink_pb2
from tink.testing import keyset_builder
from util import supported_key_types
from util import testing_servers

SUPPORTED_LANGUAGES = testing_servers.SUPPORTED_LANGUAGES_BY_PRIMITIVE['mac']


def setUpModule():
  mac.register()
  testing_servers.start('mac')


def tearDownModule():
  testing_servers.stop()


# maps from key_template_name to (key_template, key_type)
_ADDITIONAL_KEY_TEMPLATES = {
    # We additionally test a RAW and a LEGACY template, because LEGACY keys
    # require tags with a special format, and RAW don't.
    # We test one key template for each, because this is handled by the
    # primitive wrapper which is independent of the particular key template
    # used.
    'HMAC_SHA256_128BITTAG_RAW': (keyset_builder.raw_template(
        mac.mac_key_templates.HMAC_SHA256_128BITTAG), 'HmacKey'),
    'HMAC_SHA256_128BITTAG_LEGACY': (keyset_builder.legacy_template(
        mac.mac_key_templates.HMAC_SHA256_128BITTAG), 'HmacKey')
}


def mac_key_template_names() -> Iterable[str]:
  for key_type in supported_key_types.MAC_KEY_TYPES:
    for key_template_name in supported_key_types.KEY_TEMPLATE_NAMES[key_type]:
      yield key_template_name
  for key_template_name in _ADDITIONAL_KEY_TEMPLATES:
    yield key_template_name


class MacTest(parameterized.TestCase):

  @parameterized.parameters(mac_key_template_names())
  def test_compute_verify_mac(self, key_template_name):
    if key_template_name in _ADDITIONAL_KEY_TEMPLATES:
      key_template, key_type = _ADDITIONAL_KEY_TEMPLATES[
          key_template_name]
      supported_langs = supported_key_types.SUPPORTED_LANGUAGES[key_type]
    else:
      key_template = supported_key_types.KEY_TEMPLATE[key_template_name]
      supported_langs = (
          supported_key_types
          .SUPPORTED_LANGUAGES_BY_TEMPLATE_NAME[key_template_name])
    self.assertNotEmpty(supported_langs)
    # Take the first supported language to generate the keyset.
    keyset = testing_servers.new_keyset(supported_langs[0], key_template)
    supported_macs = [
        testing_servers.mac(lang, keyset) for lang in supported_langs
    ]
    unsupported_macs = [
        testing_servers.mac(lang, keyset)
        for lang in SUPPORTED_LANGUAGES
        if lang not in supported_langs
    ]
    for p in supported_macs:
      data = (
          b'This is some data to be authenticated using key_template '
          b'%s in %s.' % (key_template_name.encode('utf8'),
                          p.lang.encode('utf8')))
      mac_value = p.compute_mac(data)
      for p2 in supported_macs:
        self.assertIsNone(p2.verify_mac(mac_value, data))
      for p2 in unsupported_macs:
        with self.assertRaises(
            tink.TinkError,
            msg='Language %s supports verify_mac with %s unexpectedly' %
            (p2.lang, key_template_name)):
          p2.verify_mac(mac_value, data)
    for p in unsupported_macs:
      with self.assertRaises(
          tink.TinkError,
          msg='Language %s supports compute_mac with %s unexpectedly' %
          (p.lang, key_template_name)):
        p.compute_mac(data)


# If the implementations work fine for keysets with single keys, then key
# rotation should work if the primitive wrapper is implemented correctly.
# These wrappers do not depend on the key type, so it should be fine to always
# test with the same key type. The wrapper needs to treat keys with output
# prefix RAW and LEGACY differently, so we also test templates with these
# prefixes.
KEY_ROTATION_TEMPLATES = [
    mac.mac_key_templates.HMAC_SHA512_512BITTAG,
    keyset_builder.raw_template(mac.mac_key_templates.HMAC_SHA512_512BITTAG),
    keyset_builder.legacy_template(mac.mac_key_templates.HMAC_SHA512_512BITTAG)
]


def key_rotation_test_cases(
) -> Iterable[Tuple[str, str, tink_pb2.KeyTemplate, tink_pb2.KeyTemplate]]:
  for compute_lang in SUPPORTED_LANGUAGES:
    for verify_lang in SUPPORTED_LANGUAGES:
      for old_key_tmpl in KEY_ROTATION_TEMPLATES:
        for new_key_tmpl in KEY_ROTATION_TEMPLATES:
          yield (compute_lang, verify_lang, old_key_tmpl, new_key_tmpl)


class MacKeyRotationTest(parameterized.TestCase):

  @parameterized.parameters(key_rotation_test_cases())
  def test_key_rotation(
      self, compute_lang, verify_lang, old_key_tmpl, new_key_tmpl):
    # Do a key rotation from an old key generated from old_key_tmpl to a new
    # key generated from new_key_tmpl. MAC computation and verification are done
    # in languages compute_lang and verify_lang.
    builder = keyset_builder.new_keyset_builder()
    older_key_id = builder.add_new_key(old_key_tmpl)
    builder.set_primary_key(older_key_id)
    compute_mac1 = testing_servers.mac(compute_lang, builder.keyset())
    verify_mac1 = testing_servers.mac(verify_lang, builder.keyset())
    newer_key_id = builder.add_new_key(new_key_tmpl)
    compute_mac2 = testing_servers.mac(compute_lang, builder.keyset())
    verify_mac2 = testing_servers.mac(verify_lang, builder.keyset())

    builder.set_primary_key(newer_key_id)
    compute_mac3 = testing_servers.mac(compute_lang, builder.keyset())
    verify_mac3 = testing_servers.mac(verify_lang, builder.keyset())

    builder.disable_key(older_key_id)
    compute_mac4 = testing_servers.mac(compute_lang, builder.keyset())
    verify_mac4 = testing_servers.mac(verify_lang, builder.keyset())

    self.assertNotEqual(older_key_id, newer_key_id)
    # 1 uses the older key. So 1, 2 and 3 can verify the mac, but not 4.
    mac_value1 = compute_mac1.compute_mac(b'plaintext')
    verify_mac1.verify_mac(mac_value1, b'plaintext')
    verify_mac2.verify_mac(mac_value1, b'plaintext')
    verify_mac3.verify_mac(mac_value1, b'plaintext')
    with self.assertRaises(tink.TinkError):
      verify_mac4.verify_mac(mac_value1, b'plaintext')

    # 2 uses the older key. So 1, 2 and 3 can verify the mac, but not 4.
    mac_value2 = compute_mac2.compute_mac(b'plaintext')
    verify_mac1.verify_mac(mac_value2, b'plaintext')
    verify_mac2.verify_mac(mac_value2, b'plaintext')
    verify_mac3.verify_mac(mac_value2, b'plaintext')
    with self.assertRaises(tink.TinkError):
      verify_mac4.verify_mac(mac_value2, b'plaintext')

    # 3 uses the newer key. So 2, 3 and 4 can verify the mac, but not 1.
    mac_value3 = compute_mac3.compute_mac(b'plaintext')
    with self.assertRaises(tink.TinkError):
      verify_mac1.verify_mac(mac_value3, b'plaintext')
    verify_mac2.verify_mac(mac_value3, b'plaintext')
    verify_mac3.verify_mac(mac_value3, b'plaintext')
    verify_mac4.verify_mac(mac_value3, b'plaintext')

    # 4 uses the newer key. So 2, 3 and 4 can verify the mac, but not 1.
    mac_value4 = compute_mac4.compute_mac(b'plaintext')
    with self.assertRaises(tink.TinkError):
      verify_mac1.verify_mac(mac_value4, b'plaintext')
    verify_mac2.verify_mac(mac_value4, b'plaintext')
    verify_mac3.verify_mac(mac_value4, b'plaintext')
    verify_mac4.verify_mac(mac_value4, b'plaintext')

if __name__ == '__main__':
  absltest.main()