mirror of
https://github.com/thegeeklab/ansible-later.git
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69 lines
2.2 KiB
Python
69 lines
2.2 KiB
Python
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# 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, InvalidKey, UnsupportedAlgorithm, _Reasons
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)
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from cryptography.hazmat.backends.interfaces import HashBackend
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from cryptography.hazmat.primitives import constant_time, hashes
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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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@utils.register_interface(KeyDerivationFunction)
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class X963KDF(object):
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def __init__(self, algorithm, length, sharedinfo, backend):
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max_len = algorithm.digest_size * (2 ** 32 - 1)
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if length > max_len:
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raise ValueError(
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"Can not derive keys larger than {} bits.".format(max_len))
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if sharedinfo is not None:
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utils._check_bytes("sharedinfo", sharedinfo)
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self._algorithm = algorithm
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self._length = length
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self._sharedinfo = sharedinfo
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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 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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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 self._length > outlen:
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h = hashes.Hash(self._algorithm, self._backend)
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h.update(key_material)
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h.update(_int_to_u32be(counter))
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if self._sharedinfo is not None:
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h.update(self._sharedinfo)
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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)[:self._length]
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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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