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# -*- coding: utf-8 -*-
# libolm python bindings
# Copyright © 2015-2017 OpenMarket Ltd
# Copyright © 2018 Damir Jelić <poljar@termina.org.uk>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""libolm Utility module.
This module contains utilities for olm.
It only contains the ed25519_verify function for signature verification.
Examples:
>>> alice = Account()
>>> message = "Test"
>>> signature = alice.sign(message)
>>> signing_key = alice.identity_keys["ed25519"]
>>> ed25519_verify(signing_key, message, signature)
"""
# pylint: disable=redefined-builtin,unused-import
from typing import AnyStr, Type
# pylint: disable=no-name-in-module
from _libolm import ffi, lib # type: ignore
from ._compat import to_bytearray, to_bytes
from ._finalize import track_for_finalization
def _clear_utility(utility): # pragma: no cover
# type: (ffi.cdata) -> None
lib.olm_clear_utility(utility)
class OlmVerifyError(Exception):
"""libolm signature verification exception."""
class _Utility(object):
# pylint: disable=too-few-public-methods
"""libolm Utility class."""
_buf = None
_utility = None
@classmethod
def _allocate(cls):
# type: (Type[_Utility]) -> None
cls._buf = ffi.new("char[]", lib.olm_utility_size())
cls._utility = lib.olm_utility(cls._buf)
track_for_finalization(cls, cls._utility, _clear_utility)
@classmethod
def _check_error(cls, ret):
# type: (int) -> None
if ret != lib.olm_error():
return
raise OlmVerifyError("{}".format(
ffi.string(lib.olm_utility_last_error(
cls._utility)).decode("utf-8")))
@classmethod
def _ed25519_verify(cls, key, message, signature):
# type: (Type[_Utility], AnyStr, AnyStr, AnyStr) -> None
if not cls._utility:
cls._allocate()
byte_key = to_bytes(key)
byte_message = to_bytearray(message)
byte_signature = to_bytes(signature)
try:
cls._check_error(
lib.olm_ed25519_verify(cls._utility, byte_key, len(byte_key),
ffi.from_buffer(byte_message),
len(byte_message),
byte_signature, len(byte_signature)))
finally:
# clear out copies of the message, which may be a plaintext
if byte_message is not message:
for i in range(0, len(byte_message)):
byte_message[i] = 0
def ed25519_verify(key, message, signature):
# type: (AnyStr, AnyStr, AnyStr) -> None
"""Verify an ed25519 signature.
Raises an OlmVerifyError if verification fails.
Args:
key(str): The ed25519 public key used for signing.
message(str): The signed message.
signature(bytes): The message signature.
"""
return _Utility._ed25519_verify(key, message, signature)
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