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proc
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self
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root
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lib64
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python3.6
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site-packages
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cryptography
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hazmat
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primitives
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twofactor
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Filename :
hotp.py
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# 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 import struct import six from cryptography.exceptions import UnsupportedAlgorithm, _Reasons from cryptography.hazmat.backends import _get_backend from cryptography.hazmat.backends.interfaces import HMACBackend from cryptography.hazmat.primitives import constant_time, hmac from cryptography.hazmat.primitives.hashes import SHA1, SHA256, SHA512 from cryptography.hazmat.primitives.twofactor import InvalidToken from cryptography.hazmat.primitives.twofactor.utils import _generate_uri class HOTP(object): def __init__( self, key, length, algorithm, backend=None, enforce_key_length=True ): backend = _get_backend(backend) if not isinstance(backend, HMACBackend): raise UnsupportedAlgorithm( "Backend object does not implement HMACBackend.", _Reasons.BACKEND_MISSING_INTERFACE, ) if len(key) < 16 and enforce_key_length is True: raise ValueError("Key length has to be at least 128 bits.") if not isinstance(length, six.integer_types): raise TypeError("Length parameter must be an integer type.") if length < 6 or length > 8: raise ValueError("Length of HOTP has to be between 6 to 8.") if not isinstance(algorithm, (SHA1, SHA256, SHA512)): raise TypeError("Algorithm must be SHA1, SHA256 or SHA512.") self._key = key self._length = length self._algorithm = algorithm self._backend = backend def generate(self, counter): truncated_value = self._dynamic_truncate(counter) hotp = truncated_value % (10 ** self._length) return "{0:0{1}}".format(hotp, self._length).encode() def verify(self, hotp, counter): if not constant_time.bytes_eq(self.generate(counter), hotp): raise InvalidToken("Supplied HOTP value does not match.") def _dynamic_truncate(self, counter): ctx = hmac.HMAC(self._key, self._algorithm, self._backend) ctx.update(struct.pack(">Q", counter)) hmac_value = ctx.finalize() offset = six.indexbytes(hmac_value, len(hmac_value) - 1) & 0b1111 p = hmac_value[offset : offset + 4] return struct.unpack(">I", p)[0] & 0x7FFFFFFF def get_provisioning_uri(self, account_name, counter, issuer): return _generate_uri( self, "hotp", account_name, issuer, [("counter", int(counter))] )