JezK
Edit File: 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. import typing from cryptography import utils from cryptography.exceptions import ( AlreadyFinalized, ) from cryptography.hazmat.primitives import ciphers if typing.TYPE_CHECKING: from cryptography.hazmat.backends.openssl.cmac import _CMACContext class CMAC: _ctx: typing.Optional["_CMACContext"] _algorithm: ciphers.BlockCipherAlgorithm def __init__( self, algorithm: ciphers.BlockCipherAlgorithm, backend: typing.Any = None, ctx: typing.Optional["_CMACContext"] = None, ): if not isinstance(algorithm, ciphers.BlockCipherAlgorithm): raise TypeError("Expected instance of BlockCipherAlgorithm.") self._algorithm = algorithm if ctx is None: from cryptography.hazmat.backends.openssl.backend import ( backend as ossl, ) self._ctx = ossl.create_cmac_ctx(self._algorithm) else: self._ctx = ctx def update(self, data: bytes) -> None: if self._ctx is None: raise AlreadyFinalized("Context was already finalized.") utils._check_bytes("data", data) self._ctx.update(data) def finalize(self) -> bytes: if self._ctx is None: raise AlreadyFinalized("Context was already finalized.") digest = self._ctx.finalize() self._ctx = None return digest def verify(self, signature: bytes) -> None: 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) -> "CMAC": if self._ctx is None: raise AlreadyFinalized("Context was already finalized.") return CMAC(self._algorithm, ctx=self._ctx.copy())