Viewing file:  pbkdf2.py (2.21 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
# 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 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, hashes
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
class PBKDF2HMAC(KeyDerivationFunction):
def __init__(
self,
algorithm: hashes.HashAlgorithm,
length: int,
salt: bytes,
iterations: int,
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: bytes) -> bytes:
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: 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.")
|