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66 lines
2.1 KiB
Python
66 lines
2.1 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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from __future__ import absolute_import, division, print_function
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from cryptography import utils
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from cryptography.exceptions import (
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AlreadyFinalized, UnsupportedAlgorithm, _Reasons
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)
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from cryptography.hazmat.backends.interfaces import CMACBackend
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from cryptography.hazmat.primitives import ciphers, mac
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@utils.register_interface(mac.MACContext)
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class CMAC(object):
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def __init__(self, algorithm, backend, ctx=None):
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if not isinstance(backend, CMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement CMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE
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)
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if not isinstance(algorithm, ciphers.BlockCipherAlgorithm):
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raise TypeError(
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"Expected instance of BlockCipherAlgorithm."
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)
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self._algorithm = algorithm
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self._backend = backend
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if ctx is None:
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self._ctx = self._backend.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):
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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):
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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):
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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):
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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(
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self._algorithm,
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backend=self._backend,
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ctx=self._ctx.copy()
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)
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