| # 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 import _get_backend |
| 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=None): |
| backend = _get_backend(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( |
| "{} is not supported for PBKDF2 by this backend.".format( |
| algorithm.name |
| ), |
| _Reasons.UNSUPPORTED_HASH, |
| ) |
| self._used = False |
| self._algorithm = algorithm |
| self._length = length |
| utils._check_bytes("salt", salt) |
| 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 |
| |
| utils._check_byteslike("key_material", 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.") |