mirror of
https://github.com/thegeeklab/ansible-later.git
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69 lines
2.5 KiB
Python
69 lines
2.5 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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import six
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from cryptography.exceptions import (
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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, hmac
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from cryptography.hazmat.primitives.hashes import SHA1, SHA256, SHA512
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from cryptography.hazmat.primitives.twofactor import InvalidToken
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from cryptography.hazmat.primitives.twofactor.utils import _generate_uri
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class HOTP(object):
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def __init__(self, key, length, algorithm, backend,
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enforce_key_length=True):
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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 len(key) < 16 and enforce_key_length is True:
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raise ValueError("Key length has to be at least 128 bits.")
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if not isinstance(length, six.integer_types):
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raise TypeError("Length parameter must be an integer type.")
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if length < 6 or length > 8:
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raise ValueError("Length of HOTP has to be between 6 to 8.")
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if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
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raise TypeError("Algorithm must be SHA1, SHA256 or SHA512.")
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self._key = key
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self._length = length
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self._algorithm = algorithm
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self._backend = backend
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def generate(self, counter):
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truncated_value = self._dynamic_truncate(counter)
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hotp = truncated_value % (10 ** self._length)
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return "{0:0{1}}".format(hotp, self._length).encode()
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def verify(self, hotp, counter):
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if not constant_time.bytes_eq(self.generate(counter), hotp):
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raise InvalidToken("Supplied HOTP value does not match.")
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def _dynamic_truncate(self, counter):
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ctx = hmac.HMAC(self._key, self._algorithm, self._backend)
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ctx.update(struct.pack(">Q", counter))
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hmac_value = ctx.finalize()
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offset = six.indexbytes(hmac_value, len(hmac_value) - 1) & 0b1111
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p = hmac_value[offset:offset + 4]
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return struct.unpack(">I", p)[0] & 0x7fffffff
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def get_provisioning_uri(self, account_name, counter, issuer):
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return _generate_uri(self, "hotp", account_name, issuer, [
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("counter", int(counter)),
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])
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