/usr/lib/python2.7/dist-packages/cryptography/hazmat/primitives/hmac.py is in python-cryptography 0.6.1-1+deb8u1.
This file is owned by root:root, with mode 0o644.
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# 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
from cryptography import utils
from cryptography.exceptions import (
AlreadyFinalized, InvalidSignature, UnsupportedAlgorithm, _Reasons
)
from cryptography.hazmat.backends.interfaces import HMACBackend
from cryptography.hazmat.primitives import constant_time, interfaces
@utils.register_interface(interfaces.HashContext)
class HMAC(object):
def __init__(self, key, algorithm, backend, ctx=None):
if not isinstance(backend, HMACBackend):
raise UnsupportedAlgorithm(
"Backend object does not implement HMACBackend.",
_Reasons.BACKEND_MISSING_INTERFACE
)
if not isinstance(algorithm, interfaces.HashAlgorithm):
raise TypeError("Expected instance of interfaces.HashAlgorithm.")
self.algorithm = algorithm
self._backend = backend
self._key = key
if ctx is None:
self._ctx = self._backend.create_hmac_ctx(key, self.algorithm)
else:
self._ctx = ctx
def update(self, msg):
if self._ctx is None:
raise AlreadyFinalized("Context was already finalized.")
if not isinstance(msg, bytes):
raise TypeError("msg must be bytes.")
self._ctx.update(msg)
def copy(self):
if self._ctx is None:
raise AlreadyFinalized("Context was already finalized.")
return HMAC(
self._key,
self.algorithm,
backend=self._backend,
ctx=self._ctx.copy()
)
def finalize(self):
if self._ctx is None:
raise AlreadyFinalized("Context was already finalized.")
digest = self._ctx.finalize()
self._ctx = None
return digest
def verify(self, signature):
if not isinstance(signature, bytes):
raise TypeError("signature must be bytes.")
digest = self.finalize()
if not constant_time.bytes_eq(digest, signature):
raise InvalidSignature("Signature did not match digest.")
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