mirror of
https://github.com/thegeeklab/ansible-later.git
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146 lines
4.8 KiB
Python
146 lines
4.8 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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from enum import Enum
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from six.moves import range
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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 HMACBackend
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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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class Mode(Enum):
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CounterMode = "ctr"
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class CounterLocation(Enum):
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BeforeFixed = "before_fixed"
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AfterFixed = "after_fixed"
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@utils.register_interface(KeyDerivationFunction)
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class KBKDFHMAC(object):
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def __init__(self, algorithm, mode, length, rlen, llen,
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location, label, context, fixed, backend):
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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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if not isinstance(algorithm, hashes.HashAlgorithm):
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raise UnsupportedAlgorithm(
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"Algorithm supplied is not a supported hash algorithm.",
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_Reasons.UNSUPPORTED_HASH
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)
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if not backend.hmac_supported(algorithm):
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raise UnsupportedAlgorithm(
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"Algorithm supplied is not a supported hmac algorithm.",
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_Reasons.UNSUPPORTED_HASH
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)
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if not isinstance(mode, Mode):
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raise TypeError("mode must be of type Mode")
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if not isinstance(location, CounterLocation):
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raise TypeError("location must be of type CounterLocation")
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if (label or context) and fixed:
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raise ValueError("When supplying fixed data, "
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"label and context are ignored.")
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if rlen is None or not self._valid_byte_length(rlen):
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raise ValueError("rlen must be between 1 and 4")
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if llen is None and fixed is None:
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raise ValueError("Please specify an llen")
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if llen is not None and not isinstance(llen, int):
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raise TypeError("llen must be an integer")
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if label is None:
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label = b''
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if context is None:
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context = b''
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utils._check_bytes("label", label)
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utils._check_bytes("context", context)
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self._algorithm = algorithm
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self._mode = mode
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self._length = length
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self._rlen = rlen
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self._llen = llen
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self._location = location
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self._label = label
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self._context = context
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self._backend = backend
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self._used = False
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self._fixed_data = fixed
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def _valid_byte_length(self, value):
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if not isinstance(value, int):
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raise TypeError('value must be of type int')
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value_bin = utils.int_to_bytes(1, value)
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if not 1 <= len(value_bin) <= 4:
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return False
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return True
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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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utils._check_byteslike("key_material", key_material)
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self._used = True
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# inverse floor division (equivalent to ceiling)
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rounds = -(-self._length // self._algorithm.digest_size)
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output = [b'']
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# For counter mode, the number of iterations shall not be
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# larger than 2^r-1, where r <= 32 is the binary length of the counter
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# This ensures that the counter values used as an input to the
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# PRF will not repeat during a particular call to the KDF function.
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r_bin = utils.int_to_bytes(1, self._rlen)
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if rounds > pow(2, len(r_bin) * 8) - 1:
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raise ValueError('There are too many iterations.')
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for i in range(1, rounds + 1):
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h = hmac.HMAC(key_material, self._algorithm, backend=self._backend)
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counter = utils.int_to_bytes(i, self._rlen)
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if self._location == CounterLocation.BeforeFixed:
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h.update(counter)
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h.update(self._generate_fixed_input())
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if self._location == CounterLocation.AfterFixed:
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h.update(counter)
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output.append(h.finalize())
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return b''.join(output)[:self._length]
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def _generate_fixed_input(self):
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if self._fixed_data and isinstance(self._fixed_data, bytes):
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return self._fixed_data
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l_val = utils.int_to_bytes(self._length * 8, self._llen)
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return b"".join([self._label, b"\x00", self._context, l_val])
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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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