150 lines
4.4 KiB
Python
150 lines
4.4 KiB
Python
# -*- coding: utf-8 -*-
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# libolm python bindings
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# Copyright © 2015-2017 OpenMarket Ltd
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# Copyright © 2018 Damir Jelić <poljar@termina.org.uk>
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""libolm Utility module.
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This module contains utilities for olm.
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It only contains the ed25519_verify function for signature verification.
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Examples:
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>>> alice = Account()
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>>> message = "Test"
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>>> signature = alice.sign(message)
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>>> signing_key = alice.identity_keys["ed25519"]
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>>> ed25519_verify(signing_key, message, signature)
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"""
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# pylint: disable=redefined-builtin,unused-import
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from typing import AnyStr, Type
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from future.utils import bytes_to_native_str
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# pylint: disable=no-name-in-module
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from _libolm import ffi, lib # type: ignore
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from ._compat import to_bytearray, to_bytes
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from ._finalize import track_for_finalization
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def _clear_utility(utility): # pragma: no cover
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# type: (ffi.cdata) -> None
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lib.olm_clear_utility(utility)
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class OlmVerifyError(Exception):
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"""libolm signature verification exception."""
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class OlmHashError(Exception):
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"""libolm hash calculation exception."""
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class _Utility(object):
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# pylint: disable=too-few-public-methods
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"""libolm Utility class."""
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_buf = None
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_utility = None
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@classmethod
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def _allocate(cls):
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# type: (Type[_Utility]) -> None
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cls._buf = ffi.new("char[]", lib.olm_utility_size())
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cls._utility = lib.olm_utility(cls._buf)
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track_for_finalization(cls, cls._utility, _clear_utility)
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@classmethod
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def _check_error(cls, ret, error_class):
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# type: (int, Type) -> None
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if ret != lib.olm_error():
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return
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raise error_class("{}".format(
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ffi.string(lib.olm_utility_last_error(
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cls._utility)).decode("utf-8")))
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@classmethod
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def _ed25519_verify(cls, key, message, signature):
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# type: (Type[_Utility], AnyStr, AnyStr, AnyStr) -> None
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if not cls._utility:
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cls._allocate()
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byte_key = to_bytes(key)
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byte_message = to_bytearray(message)
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byte_signature = to_bytearray(signature)
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try:
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ret = lib.olm_ed25519_verify(
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cls._utility,
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byte_key,
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len(byte_key),
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ffi.from_buffer(byte_message),
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len(byte_message),
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ffi.from_buffer(byte_signature),
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len(byte_signature)
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)
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cls._check_error(ret, OlmVerifyError)
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finally:
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# clear out copies of the message, which may be a plaintext
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if byte_message is not message:
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for i in range(0, len(byte_message)):
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byte_message[i] = 0
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@classmethod
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def _sha256(cls, input):
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# type: (Type[_Utility], AnyStr) -> str
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if not cls._utility:
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cls._allocate()
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byte_input = to_bytes(input)
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hash_length = lib.olm_sha256_length(cls._utility)
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hash = ffi.new("char[]", hash_length)
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ret = lib.olm_sha256(cls._utility, byte_input, len(byte_input),
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hash, hash_length)
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cls._check_error(ret, OlmHashError)
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return bytes_to_native_str(ffi.unpack(hash, hash_length))
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def ed25519_verify(key, message, signature):
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# type: (AnyStr, AnyStr, AnyStr) -> None
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"""Verify an ed25519 signature.
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Raises an OlmVerifyError if verification fails.
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Args:
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key(str): The ed25519 public key used for signing.
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message(str): The signed message.
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signature(bytes): The message signature.
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"""
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return _Utility._ed25519_verify(key, message, signature)
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def sha256(input_string):
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# type: (AnyStr) -> str
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"""Calculate the SHA-256 hash of the input and encodes it as base64.
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Args:
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input_string(str): The input for which the hash will be calculated.
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"""
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return _Utility._sha256(input_string)
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