mirror of
https://github.com/PiBrewing/craftbeerpi4.git
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131 lines
4 KiB
Python
131 lines
4 KiB
Python
# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import absolute_import, division, print_function
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import struct
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from cryptography import utils
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from cryptography.exceptions import (
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AlreadyFinalized,
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InvalidKey,
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UnsupportedAlgorithm,
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_Reasons,
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)
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from cryptography.hazmat.backends import _get_backend
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from cryptography.hazmat.backends.interfaces import HMACBackend
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from cryptography.hazmat.backends.interfaces import HashBackend
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from cryptography.hazmat.primitives import constant_time, hashes, hmac
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from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
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def _int_to_u32be(n):
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return struct.pack(">I", n)
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def _common_args_checks(algorithm, length, otherinfo):
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max_length = algorithm.digest_size * (2 ** 32 - 1)
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if length > max_length:
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raise ValueError(
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"Can not derive keys larger than {} bits.".format(max_length)
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)
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if otherinfo is not None:
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utils._check_bytes("otherinfo", otherinfo)
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def _concatkdf_derive(key_material, length, auxfn, otherinfo):
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utils._check_byteslike("key_material", key_material)
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output = [b""]
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outlen = 0
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counter = 1
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while length > outlen:
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h = auxfn()
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h.update(_int_to_u32be(counter))
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h.update(key_material)
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h.update(otherinfo)
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output.append(h.finalize())
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outlen += len(output[-1])
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counter += 1
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return b"".join(output)[:length]
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@utils.register_interface(KeyDerivationFunction)
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class ConcatKDFHash(object):
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def __init__(self, algorithm, length, otherinfo, backend=None):
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backend = _get_backend(backend)
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_common_args_checks(algorithm, length, otherinfo)
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self._algorithm = algorithm
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self._length = length
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self._otherinfo = otherinfo
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if self._otherinfo is None:
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self._otherinfo = b""
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if not isinstance(backend, HashBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HashBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE,
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)
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self._backend = backend
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self._used = False
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def _hash(self):
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return hashes.Hash(self._algorithm, self._backend)
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def derive(self, key_material):
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if self._used:
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raise AlreadyFinalized
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self._used = True
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return _concatkdf_derive(
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key_material, self._length, self._hash, self._otherinfo
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)
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def verify(self, key_material, expected_key):
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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@utils.register_interface(KeyDerivationFunction)
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class ConcatKDFHMAC(object):
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def __init__(self, algorithm, length, salt, otherinfo, backend=None):
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backend = _get_backend(backend)
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_common_args_checks(algorithm, length, otherinfo)
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self._algorithm = algorithm
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self._length = length
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self._otherinfo = otherinfo
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if self._otherinfo is None:
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self._otherinfo = b""
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if salt is None:
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salt = b"\x00" * algorithm.block_size
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else:
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utils._check_bytes("salt", salt)
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self._salt = salt
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if not isinstance(backend, HMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE,
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)
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self._backend = backend
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self._used = False
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def _hmac(self):
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return hmac.HMAC(self._salt, self._algorithm, self._backend)
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def derive(self, key_material):
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if self._used:
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raise AlreadyFinalized
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self._used = True
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return _concatkdf_derive(
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key_material, self._length, self._hmac, self._otherinfo
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)
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def verify(self, key_material, expected_key):
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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