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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.
import typing
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
from cryptography.hazmat.primitives.twofactor import InvalidToken
from cryptography.hazmat.primitives.twofactor.hotp import (
HOTP,
_ALLOWED_HASH_TYPES,
)
from cryptography.hazmat.primitives.twofactor.utils import _generate_uri
class TOTP(object):
def __init__(
self,
key: bytes,
length: int,
algorithm: _ALLOWED_HASH_TYPES,
time_step: int,
backend=None,
enforce_key_length: bool = True,
):
backend = _get_backend(backend)
if not isinstance(backend, HMACBackend):
raise UnsupportedAlgorithm(
"Backend object does not implement HMACBackend.",
_Reasons.BACKEND_MISSING_INTERFACE,
)
self._time_step = time_step
self._hotp = HOTP(key, length, algorithm, backend, enforce_key_length)
def generate(self, time: typing.Union[int, float]) -> bytes:
counter = int(time / self._time_step)
return self._hotp.generate(counter)
def verify(self, totp: bytes, time: int) -> None:
if not constant_time.bytes_eq(self.generate(time), totp):
raise InvalidToken("Supplied TOTP value does not match.")
def get_provisioning_uri(
self, account_name: str, issuer: typing.Optional[str]
) -> str:
return _generate_uri(
self._hotp,
"totp",
account_name,
issuer,
[("period", int(self._time_step))],
)
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