Current File : //lib/python3/dist-packages/cryptography/hazmat/primitives/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 annotations
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,
) -> 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())
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