# 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 sys
import typing
from cryptography import utils
from cryptography.exceptions import (
AlreadyFinalized,
InvalidKey,
UnsupportedAlgorithm,
)
from cryptography.hazmat.bindings._rust import openssl as rust_openssl
from cryptography.hazmat.primitives import constant_time
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
# This is used by the scrypt tests to skip tests that require more memory
# than the MEM_LIMIT
_MEM_LIMIT = sys.maxsize // 2
class Scrypt(KeyDerivationFunction):
def __init__(
self,
salt: bytes,
length: int,
n: int,
r: int,
p: int,
backend: typing.Any = None,
):
from cryptography.hazmat.backends.openssl.backend import (
backend as ossl,
)
if not ossl.scrypt_supported():
raise UnsupportedAlgorithm(
"This version of OpenSSL does not support scrypt"
)
self._length = length
utils._check_bytes("salt", salt)
if n < 2 or (n & (n - 1)) != 0:
raise ValueError("n must be greater than 1 and be a power of 2.")
if r < 1:
raise ValueError("r must be greater than or equal to 1.")
if p < 1:
raise ValueError("p must be greater than or equal to 1.")
self._used = False
self._salt = salt
self._n = n
self._r = r
self._p = p
def derive(self, key_material: bytes) -> bytes:
if self._used:
raise AlreadyFinalized("Scrypt instances can only be used once.")
self._used = True
utils._check_byteslike("key_material", key_material)
return rust_openssl.kdf.derive_scrypt(
key_material,
self._salt,
self._n,
self._r,
self._p,
_MEM_LIMIT,
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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