tests/wycheproof/test_cmac.py

# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.

from __future__ import absolute_import, division, print_function

import binascii

import pytest

from cryptography.exceptions import InvalidSignature
from cryptography.hazmat.backends.interfaces import CMACBackend
from cryptography.hazmat.primitives.ciphers.algorithms import AES
from cryptography.hazmat.primitives.cmac import CMAC


@pytest.mark.requires_backend_interface(interface=CMACBackend)
@pytest.mark.wycheproof_tests("aes_cmac_test.json")
def test_aes_cmac(backend, wycheproof):
    key = binascii.unhexlify(wycheproof.testcase["key"])
    msg = binascii.unhexlify(wycheproof.testcase["msg"])
    tag = binascii.unhexlify(wycheproof.testcase["tag"])

    # skip truncated tags, which we don't support in the API
    if wycheproof.valid and len(tag) == 16:
        ctx = CMAC(AES(key), backend)
        ctx.update(msg)
        ctx.verify(tag)
    elif len(key) not in [16, 24, 32]:
        with pytest.raises(ValueError):
            CMAC(AES(key), backend)
    else:
        ctx = CMAC(AES(key), backend)
        ctx.update(msg)
        with pytest.raises(InvalidSignature):
            ctx.verify(tag)