59 lines
2.2 KiB
Python
59 lines
2.2 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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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 UnsupportedAlgorithm, _Reasons
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from cryptography.hazmat.primitives import interfaces
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@utils.register_interface(interfaces.HashContext)
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class _HMACContext(object):
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def __init__(self, backend, key, algorithm, ctx=None):
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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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ctx = self._backend._ffi.new("CCHmacContext *")
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try:
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alg = self._backend._supported_hmac_algorithms[algorithm.name]
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except KeyError:
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raise UnsupportedAlgorithm(
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"{0} is not a supported HMAC hash on this backend.".format(
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algorithm.name),
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_Reasons.UNSUPPORTED_HASH
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)
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self._backend._lib.CCHmacInit(ctx, alg, key, len(key))
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self._ctx = ctx
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self._key = key
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def copy(self):
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copied_ctx = self._backend._ffi.new("CCHmacContext *")
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# CommonCrypto has no APIs for copying HMACs, so we have to copy the
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# underlying struct.
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copied_ctx[0] = self._ctx[0]
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return _HMACContext(
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self._backend, self._key, self.algorithm, ctx=copied_ctx
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)
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def update(self, data):
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self._backend._lib.CCHmacUpdate(self._ctx, data, len(data))
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def finalize(self):
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buf = self._backend._ffi.new("unsigned char[]",
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self.algorithm.digest_size)
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self._backend._lib.CCHmacFinal(self._ctx, buf)
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return self._backend._ffi.buffer(buf)[:]
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