/usr/lib/python3/dist-packages/cryptography/hazmat/primitives/kdf/kbkdf.py is in python3-cryptography 2.1.4-1ubuntu1.1.
This file is owned by root:root, with mode 0o644.
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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 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 | # 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 enum import Enum
from six.moves import range
from cryptography import utils
from cryptography.exceptions import (
AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
)
from cryptography.hazmat.backends.interfaces import HMACBackend
from cryptography.hazmat.primitives import constant_time, hashes, hmac
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
class Mode(Enum):
CounterMode = "ctr"
class CounterLocation(Enum):
BeforeFixed = "before_fixed"
AfterFixed = "after_fixed"
@utils.register_interface(KeyDerivationFunction)
class KBKDFHMAC(object):
def __init__(self, algorithm, mode, length, rlen, llen,
location, label, context, fixed, backend):
if not isinstance(backend, HMACBackend):
raise UnsupportedAlgorithm(
"Backend object does not implement HMACBackend.",
_Reasons.BACKEND_MISSING_INTERFACE
)
if not isinstance(algorithm, hashes.HashAlgorithm):
raise UnsupportedAlgorithm(
"Algorithm supplied is not a supported hash algorithm.",
_Reasons.UNSUPPORTED_HASH
)
if not backend.hmac_supported(algorithm):
raise UnsupportedAlgorithm(
"Algorithm supplied is not a supported hmac algorithm.",
_Reasons.UNSUPPORTED_HASH
)
if not isinstance(mode, Mode):
raise TypeError("mode must be of type Mode")
if not isinstance(location, CounterLocation):
raise TypeError("location must be of type CounterLocation")
if (label or context) and fixed:
raise ValueError("When supplying fixed data, "
"label and context are ignored.")
if rlen is None or not self._valid_byte_length(rlen):
raise ValueError("rlen must be between 1 and 4")
if llen is None and fixed is None:
raise ValueError("Please specify an llen")
if llen is not None and not isinstance(llen, int):
raise TypeError("llen must be an integer")
if label is None:
label = b''
if context is None:
context = b''
if (not isinstance(label, bytes) or
not isinstance(context, bytes)):
raise TypeError('label and context must be of type bytes')
self._algorithm = algorithm
self._mode = mode
self._length = length
self._rlen = rlen
self._llen = llen
self._location = location
self._label = label
self._context = context
self._backend = backend
self._used = False
self._fixed_data = fixed
def _valid_byte_length(self, value):
if not isinstance(value, int):
raise TypeError('value must be of type int')
value_bin = utils.int_to_bytes(1, value)
if not 1 <= len(value_bin) <= 4:
return False
return True
def derive(self, key_material):
if self._used:
raise AlreadyFinalized
if not isinstance(key_material, bytes):
raise TypeError('key_material must be bytes')
self._used = True
# inverse floor division (equivalent to ceiling)
rounds = -(-self._length // self._algorithm.digest_size)
output = [b'']
# For counter mode, the number of iterations shall not be
# larger than 2^r-1, where r <= 32 is the binary length of the counter
# This ensures that the counter values used as an input to the
# PRF will not repeat during a particular call to the KDF function.
r_bin = utils.int_to_bytes(1, self._rlen)
if rounds > pow(2, len(r_bin) * 8) - 1:
raise ValueError('There are too many iterations.')
for i in range(1, rounds + 1):
h = hmac.HMAC(key_material, self._algorithm, backend=self._backend)
counter = utils.int_to_bytes(i, self._rlen)
if self._location == CounterLocation.BeforeFixed:
h.update(counter)
h.update(self._generate_fixed_input())
if self._location == CounterLocation.AfterFixed:
h.update(counter)
output.append(h.finalize())
return b''.join(output)[:self._length]
def _generate_fixed_input(self):
if self._fixed_data and isinstance(self._fixed_data, bytes):
return self._fixed_data
l_val = utils.int_to_bytes(self._length * 8, self._llen)
return b"".join([self._label, b"\x00", self._context, l_val])
def verify(self, key_material, expected_key):
if not constant_time.bytes_eq(self.derive(key_material), expected_key):
raise InvalidKey
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