Viewing file:  pbkdf2.py (2.13 KB) -rw-r--r--
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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import absolute_import, division, print_function
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
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
@utils.register_interface(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 not isinstance(salt, bytes):
raise TypeError("salt must be bytes.")
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 not isinstance(key_material, bytes):
raise TypeError("key_material must be bytes.")
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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