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57 lines
2.0 KiB
Python
57 lines
2.0 KiB
Python
# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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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 (
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AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
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)
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from cryptography.hazmat.backends.interfaces import PBKDF2HMACBackend
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from cryptography.hazmat.primitives import constant_time
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from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
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@utils.register_interface(KeyDerivationFunction)
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class PBKDF2HMAC(object):
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def __init__(self, algorithm, length, salt, iterations, backend):
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if not isinstance(backend, PBKDF2HMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement PBKDF2HMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE
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)
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if not backend.pbkdf2_hmac_supported(algorithm):
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raise UnsupportedAlgorithm(
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"{} is not supported for PBKDF2 by 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._used = False
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self._algorithm = algorithm
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self._length = length
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utils._check_bytes("salt", salt)
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self._salt = salt
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self._iterations = iterations
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self._backend = backend
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def derive(self, key_material):
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if self._used:
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raise AlreadyFinalized("PBKDF2 instances can only be used once.")
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self._used = True
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utils._check_byteslike("key_material", key_material)
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return self._backend.derive_pbkdf2_hmac(
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self._algorithm,
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self._length,
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self._salt,
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self._iterations,
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key_material
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)
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def verify(self, key_material, expected_key):
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derived_key = self.derive(key_material)
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if not constant_time.bytes_eq(derived_key, expected_key):
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raise InvalidKey("Keys do not match.")
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