| # 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 |
| |
| |
| from cryptography import utils |
| from cryptography.exceptions import ( |
| AlreadyFinalized, |
| UnsupportedAlgorithm, |
| _Reasons, |
| ) |
| |
| |
| class Poly1305(object): |
| def __init__(self, key): |
| from cryptography.hazmat.backends.openssl.backend import backend |
| |
| if not backend.poly1305_supported(): |
| raise UnsupportedAlgorithm( |
| "poly1305 is not supported by this version of OpenSSL.", |
| _Reasons.UNSUPPORTED_MAC, |
| ) |
| self._ctx = backend.create_poly1305_ctx(key) |
| |
| def update(self, data): |
| if self._ctx is None: |
| raise AlreadyFinalized("Context was already finalized.") |
| utils._check_byteslike("data", data) |
| self._ctx.update(data) |
| |
| def finalize(self): |
| if self._ctx is None: |
| raise AlreadyFinalized("Context was already finalized.") |
| mac = self._ctx.finalize() |
| self._ctx = None |
| return mac |
| |
| def verify(self, tag): |
| utils._check_bytes("tag", tag) |
| if self._ctx is None: |
| raise AlreadyFinalized("Context was already finalized.") |
| |
| ctx, self._ctx = self._ctx, None |
| ctx.verify(tag) |
| |
| @classmethod |
| def generate_tag(cls, key, data): |
| p = Poly1305(key) |
| p.update(data) |
| return p.finalize() |
| |
| @classmethod |
| def verify_tag(cls, key, data, tag): |
| p = Poly1305(key) |
| p.update(data) |
| p.verify(tag) |