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- # 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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