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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 import utils
from cryptography.exceptions import (
AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
)
from cryptography.hazmat.backends.interfaces import PBKDF2HMACBackend
from cryptography.hazmat.primitives import constant_time, interfaces
@utils.register_interface(interfaces.KeyDerivationFunction)
class PBKDF2HMAC(object):
def __init__(self, algorithm, length, salt, iterations, backend):
if not isinstance(backend, PBKDF2HMACBackend):
raise UnsupportedAlgorithm(
"Backend object does not implement PBKDF2HMACBackend",
_Reasons.BACKEND_MISSING_INTERFACE
)
if not backend.pbkdf2_hmac_supported(algorithm):
raise UnsupportedAlgorithm(
"{0} is not supported for PBKDF2 by this backend".format(
algorithm.name),
_Reasons.UNSUPPORTED_HASH
)
self._used = False
self._algorithm = algorithm
self._length = length
if isinstance(salt, six.text_type):
raise TypeError(
"Unicode-objects must be encoded before using them as key "
"material."
)
self._salt = salt
self._iterations = iterations
self._backend = backend
def derive(self, key_material):
if self._used:
raise AlreadyFinalized("PBKDF2 instances can only be used once")
self._used = True
if isinstance(key_material, six.text_type):
raise TypeError(
"Unicode-objects must be encoded before using them as key "
"material."
)
return self._backend.derive_pbkdf2_hmac(
self._algorithm,
self._length,
self._salt,
self._iterations,
key_material
)
def verify(self, key_material, expected_key):
derived_key = self.derive(key_material)
if not constant_time.bytes_eq(derived_key, expected_key):
raise InvalidKey("Keys do not match.")
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