| # 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 |
| |
| from cryptography import utils |
| from cryptography.exceptions import ( |
| AlreadyFinalized, |
| UnsupportedAlgorithm, |
| _Reasons, |
| ) |
| from cryptography.hazmat.backends import _get_backend |
| from cryptography.hazmat.backends.interfaces import CMACBackend |
| from cryptography.hazmat.primitives import ciphers |
| |
| |
| class CMAC(object): |
| def __init__(self, algorithm, backend=None, ctx=None): |
| backend = _get_backend(backend) |
| if not isinstance(backend, CMACBackend): |
| raise UnsupportedAlgorithm( |
| "Backend object does not implement CMACBackend.", |
| _Reasons.BACKEND_MISSING_INTERFACE, |
| ) |
| |
| if not isinstance(algorithm, ciphers.BlockCipherAlgorithm): |
| raise TypeError("Expected instance of BlockCipherAlgorithm.") |
| self._algorithm = algorithm |
| |
| self._backend = backend |
| if ctx is None: |
| self._ctx = self._backend.create_cmac_ctx(self._algorithm) |
| else: |
| self._ctx = ctx |
| |
| def update(self, data): |
| if self._ctx is None: |
| raise AlreadyFinalized("Context was already finalized.") |
| |
| utils._check_bytes("data", data) |
| self._ctx.update(data) |
| |
| def finalize(self): |
| if self._ctx is None: |
| raise AlreadyFinalized("Context was already finalized.") |
| digest = self._ctx.finalize() |
| self._ctx = None |
| return digest |
| |
| def verify(self, signature): |
| utils._check_bytes("signature", signature) |
| if self._ctx is None: |
| raise AlreadyFinalized("Context was already finalized.") |
| |
| ctx, self._ctx = self._ctx, None |
| ctx.verify(signature) |
| |
| def copy(self): |
| if self._ctx is None: |
| raise AlreadyFinalized("Context was already finalized.") |
| return CMAC( |
| self._algorithm, backend=self._backend, ctx=self._ctx.copy() |
| ) |