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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import, division, print_function
import six
from cryptography.hazmat.primitives import interfaces
@interfaces.register(interfaces.HashContext)
class HMAC(object):
def __init__(self, key, algorithm, ctx=None, backend=None):
super(HMAC, self).__init__()
if not isinstance(algorithm, interfaces.HashAlgorithm):
raise TypeError("Expected instance of interfaces.HashAlgorithm.")
self.algorithm = algorithm
if backend is None:
from cryptography.hazmat.bindings import _default_backend
backend = _default_backend
self._backend = backend
self._key = key
if ctx is None:
self._ctx = self._backend.hmacs.create_ctx(key, self.algorithm)
else:
self._ctx = ctx
def update(self, msg):
if isinstance(msg, six.text_type):
raise TypeError("Unicode-objects must be encoded before hashing")
self._backend.hmacs.update_ctx(self._ctx, msg)
def copy(self):
return self.__class__(self._key, self.algorithm, backend=self._backend,
ctx=self._backend.hmacs.copy_ctx(self._ctx))
def finalize(self):
return self._backend.hmacs.finalize_ctx(self._ctx,
self.algorithm.digest_size)
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