# 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 annotations
import typing
from cryptography import utils
from cryptography.exceptions import (
AlreadyFinalized,
InvalidKey,
UnsupportedAlgorithm,
_Reasons,
)
from cryptography.hazmat.bindings._rust import openssl as rust_openssl
from cryptography.hazmat.primitives import constant_time, hashes
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
class PBKDF2HMAC(KeyDerivationFunction):
def __init__(
self,
algorithm: hashes.HashAlgorithm,
length: int,
salt: bytes,
iterations: int,
backend: typing.Any = None,
):
from cryptography.hazmat.backends.openssl.backend import (
backend as ossl,
)
if not ossl.pbkdf2_hmac_supported(algorithm):
raise UnsupportedAlgorithm(
f"{algorithm.name} is not supported for PBKDF2.",
_Reasons.UNSUPPORTED_HASH,
)
self._used = False
self._algorithm = algorithm
self._length = length
utils._check_bytes("salt", salt)
self._salt = salt
self._iterations = iterations
def derive(self, key_material: bytes) -> bytes:
if self._used:
raise AlreadyFinalized("PBKDF2 instances can only be used once.")
self._used = True
return rust_openssl.kdf.derive_pbkdf2_hmac(
key_material,
self._algorithm,
self._salt,
self._iterations,
self._length,
)
def verify(self, key_material: bytes, expected_key: bytes) -> None:
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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