/usr/lib/python3/dist-packages/cryptography/hazmat/primitives/kdf/scrypt.py is in python3-cryptography 2.1.4-1ubuntu1.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 | # 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
import sys
from cryptography import utils
from cryptography.exceptions import (
AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
)
from cryptography.hazmat.backends.interfaces import ScryptBackend
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
@utils.register_interface(KeyDerivationFunction)
class Scrypt(object):
def __init__(self, salt, length, n, r, p, backend):
if not isinstance(backend, ScryptBackend):
raise UnsupportedAlgorithm(
"Backend object does not implement ScryptBackend.",
_Reasons.BACKEND_MISSING_INTERFACE
)
self._length = length
if not isinstance(salt, bytes):
raise TypeError("salt must be bytes.")
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
self._backend = backend
def derive(self, key_material):
if self._used:
raise AlreadyFinalized("Scrypt instances can only be used once.")
self._used = True
if not isinstance(key_material, bytes):
raise TypeError("key_material must be bytes.")
return self._backend.derive_scrypt(
key_material, self._salt, self._length, self._n, self._r, self._p
)
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.")
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