70 lines
2.3 KiB
Python
70 lines
2.3 KiB
Python
# 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 HMACBackend
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from cryptography.hazmat.primitives import hashes, interfaces
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@utils.register_interface(interfaces.MACContext)
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@utils.register_interface(hashes.HashContext)
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class HMAC(object):
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def __init__(self, key, algorithm, backend, ctx=None):
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if not isinstance(backend, HMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE
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)
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if not isinstance(algorithm, hashes.HashAlgorithm):
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raise TypeError("Expected instance of hashes.HashAlgorithm.")
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self._algorithm = algorithm
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self._backend = backend
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self._key = key
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if ctx is None:
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self._ctx = self._backend.create_hmac_ctx(key, self.algorithm)
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else:
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self._ctx = ctx
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algorithm = utils.read_only_property("_algorithm")
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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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if not isinstance(data, bytes):
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raise TypeError("data must be bytes.")
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self._ctx.update(data)
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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 HMAC(
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self._key,
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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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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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if not isinstance(signature, bytes):
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raise TypeError("signature must be bytes.")
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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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