65 lines
2.0 KiB
Python
65 lines
2.0 KiB
Python
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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import typing
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from cryptography import utils
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from cryptography.exceptions import AlreadyFinalized
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from cryptography.hazmat.primitives import ciphers
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if typing.TYPE_CHECKING:
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from cryptography.hazmat.backends.openssl.cmac import _CMACContext
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class CMAC:
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_ctx: typing.Optional["_CMACContext"]
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_algorithm: ciphers.BlockCipherAlgorithm
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def __init__(
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self,
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algorithm: ciphers.BlockCipherAlgorithm,
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backend: typing.Any = None,
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ctx: typing.Optional["_CMACContext"] = None,
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) -> None:
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if not isinstance(algorithm, ciphers.BlockCipherAlgorithm):
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raise TypeError("Expected instance of BlockCipherAlgorithm.")
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self._algorithm = algorithm
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if ctx is None:
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from cryptography.hazmat.backends.openssl.backend import (
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backend as ossl,
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)
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self._ctx = ossl.create_cmac_ctx(self._algorithm)
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else:
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self._ctx = ctx
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def update(self, data: bytes) -> None:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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utils._check_bytes("data", data)
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self._ctx.update(data)
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def finalize(self) -> bytes:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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digest = self._ctx.finalize()
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self._ctx = None
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return digest
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def verify(self, signature: bytes) -> None:
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utils._check_bytes("signature", signature)
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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ctx, self._ctx = self._ctx, None
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ctx.verify(signature)
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def copy(self) -> "CMAC":
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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return CMAC(self._algorithm, ctx=self._ctx.copy())
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