mirror of https://git.matrix.org/git/olm.git
402 lines
10 KiB
C++
402 lines
10 KiB
C++
/* Copyright 2015-2016 OpenMarket Ltd
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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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*/
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#include "olm/message.hh"
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#include "olm/memory.hh"
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namespace {
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template<typename T>
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static std::size_t varint_length(
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T value
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) {
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std::size_t result = 1;
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while (value >= 128U) {
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++result;
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value >>= 7;
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}
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return result;
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}
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template<typename T>
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static std::uint8_t * varint_encode(
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std::uint8_t * output,
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T value
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) {
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while (value >= 128U) {
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*(output++) = (0x7F & value) | 0x80;
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value >>= 7;
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}
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(*output++) = value;
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return output;
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}
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template<typename T>
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static T varint_decode(
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std::uint8_t const * varint_start,
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std::uint8_t const * varint_end
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) {
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T value = 0;
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if (varint_end == varint_start) {
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return 0;
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}
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do {
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value <<= 7;
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value |= 0x7F & *(--varint_end);
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} while (varint_end != varint_start);
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return value;
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}
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static std::uint8_t const * varint_skip(
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std::uint8_t const * input,
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std::uint8_t const * input_end
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) {
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while (input != input_end) {
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std::uint8_t tmp = *(input++);
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if ((tmp & 0x80) == 0) {
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return input;
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}
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}
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return input;
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}
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static std::size_t varstring_length(
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std::size_t string_length
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) {
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return varint_length(string_length) + string_length;
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}
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static std::size_t const VERSION_LENGTH = 1;
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static std::uint8_t const RATCHET_KEY_TAG = 012;
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static std::uint8_t const COUNTER_TAG = 020;
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static std::uint8_t const CIPHERTEXT_TAG = 042;
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static std::uint8_t * encode(
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std::uint8_t * pos,
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std::uint8_t tag,
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std::uint32_t value
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) {
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*(pos++) = tag;
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return varint_encode(pos, value);
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}
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static std::uint8_t * encode(
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std::uint8_t * pos,
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std::uint8_t tag,
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std::uint8_t * & value, std::size_t value_length
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) {
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*(pos++) = tag;
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pos = varint_encode(pos, value_length);
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value = pos;
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return pos + value_length;
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}
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static std::uint8_t const * decode(
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std::uint8_t const * pos, std::uint8_t const * end,
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std::uint8_t tag,
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std::uint32_t & value, bool & has_value
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) {
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if (pos != end && *pos == tag) {
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++pos;
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std::uint8_t const * value_start = pos;
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pos = varint_skip(pos, end);
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value = varint_decode<std::uint32_t>(value_start, pos);
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has_value = true;
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}
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return pos;
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}
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static std::uint8_t const * decode(
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std::uint8_t const * pos, std::uint8_t const * end,
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std::uint8_t tag,
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std::uint8_t const * & value, std::size_t & value_length
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) {
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if (pos != end && *pos == tag) {
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++pos;
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std::uint8_t const * len_start = pos;
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pos = varint_skip(pos, end);
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std::size_t len = varint_decode<std::size_t>(len_start, pos);
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if (len > std::size_t(end - pos)) return end;
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value = pos;
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value_length = len;
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pos += len;
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}
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return pos;
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}
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static std::uint8_t const * skip_unknown(
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std::uint8_t const * pos, std::uint8_t const * end
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) {
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if (pos != end) {
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uint8_t tag = *pos;
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if ((tag & 0x7) == 0) {
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pos = varint_skip(pos, end);
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pos = varint_skip(pos, end);
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} else if ((tag & 0x7) == 2) {
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pos = varint_skip(pos, end);
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std::uint8_t const * len_start = pos;
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pos = varint_skip(pos, end);
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std::size_t len = varint_decode<std::size_t>(len_start, pos);
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if (len > std::size_t(end - pos)) return end;
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pos += len;
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} else {
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return end;
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}
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}
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return pos;
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}
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} // namespace
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std::size_t olm::encode_message_length(
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std::uint32_t counter,
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std::size_t ratchet_key_length,
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std::size_t ciphertext_length,
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std::size_t mac_length
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) {
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std::size_t length = VERSION_LENGTH;
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length += 1 + varstring_length(ratchet_key_length);
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length += 1 + varint_length(counter);
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length += 1 + varstring_length(ciphertext_length);
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length += mac_length;
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return length;
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}
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void olm::encode_message(
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olm::MessageWriter & writer,
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std::uint8_t version,
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std::uint32_t counter,
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std::size_t ratchet_key_length,
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std::size_t ciphertext_length,
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std::uint8_t * output
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) {
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std::uint8_t * pos = output;
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*(pos++) = version;
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pos = encode(pos, RATCHET_KEY_TAG, writer.ratchet_key, ratchet_key_length);
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pos = encode(pos, COUNTER_TAG, counter);
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pos = encode(pos, CIPHERTEXT_TAG, writer.ciphertext, ciphertext_length);
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}
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void olm::decode_message(
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olm::MessageReader & reader,
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std::uint8_t const * input, std::size_t input_length,
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std::size_t mac_length
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) {
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std::uint8_t const * pos = input;
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std::uint8_t const * end = input + input_length - mac_length;
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std::uint8_t const * unknown = nullptr;
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reader.input = input;
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reader.input_length = input_length;
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reader.has_counter = false;
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reader.ratchet_key = nullptr;
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reader.ratchet_key_length = 0;
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reader.ciphertext = nullptr;
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reader.ciphertext_length = 0;
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if (input_length < mac_length) return;
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if (pos == end) return;
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reader.version = *(pos++);
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while (pos != end) {
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unknown = pos;
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pos = decode(
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pos, end, RATCHET_KEY_TAG,
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reader.ratchet_key, reader.ratchet_key_length
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);
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pos = decode(
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pos, end, COUNTER_TAG,
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reader.counter, reader.has_counter
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);
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pos = decode(
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pos, end, CIPHERTEXT_TAG,
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reader.ciphertext, reader.ciphertext_length
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);
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if (unknown == pos) {
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pos = skip_unknown(pos, end);
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}
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}
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}
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namespace {
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static std::uint8_t const ONE_TIME_KEY_ID_TAG = 012;
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static std::uint8_t const BASE_KEY_TAG = 022;
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static std::uint8_t const IDENTITY_KEY_TAG = 032;
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static std::uint8_t const MESSAGE_TAG = 042;
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} // namespace
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std::size_t olm::encode_one_time_key_message_length(
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std::size_t one_time_key_length,
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std::size_t identity_key_length,
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std::size_t base_key_length,
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std::size_t message_length
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) {
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std::size_t length = VERSION_LENGTH;
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length += 1 + varstring_length(one_time_key_length);
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length += 1 + varstring_length(identity_key_length);
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length += 1 + varstring_length(base_key_length);
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length += 1 + varstring_length(message_length);
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return length;
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}
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void olm::encode_one_time_key_message(
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olm::PreKeyMessageWriter & writer,
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std::uint8_t version,
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std::size_t identity_key_length,
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std::size_t base_key_length,
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std::size_t one_time_key_length,
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std::size_t message_length,
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std::uint8_t * output
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) {
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std::uint8_t * pos = output;
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*(pos++) = version;
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pos = encode(pos, ONE_TIME_KEY_ID_TAG, writer.one_time_key, one_time_key_length);
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pos = encode(pos, BASE_KEY_TAG, writer.base_key, base_key_length);
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pos = encode(pos, IDENTITY_KEY_TAG, writer.identity_key, identity_key_length);
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pos = encode(pos, MESSAGE_TAG, writer.message, message_length);
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}
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void olm::decode_one_time_key_message(
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PreKeyMessageReader & reader,
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std::uint8_t const * input, std::size_t input_length
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) {
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std::uint8_t const * pos = input;
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std::uint8_t const * end = input + input_length;
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std::uint8_t const * unknown = nullptr;
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reader.one_time_key = nullptr;
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reader.one_time_key_length = 0;
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reader.identity_key = nullptr;
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reader.identity_key_length = 0;
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reader.base_key = nullptr;
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reader.base_key_length = 0;
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reader.message = nullptr;
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reader.message_length = 0;
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if (pos == end) return;
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reader.version = *(pos++);
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while (pos != end) {
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unknown = pos;
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pos = decode(
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pos, end, ONE_TIME_KEY_ID_TAG,
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reader.one_time_key, reader.one_time_key_length
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);
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pos = decode(
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pos, end, BASE_KEY_TAG,
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reader.base_key, reader.base_key_length
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);
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pos = decode(
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pos, end, IDENTITY_KEY_TAG,
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reader.identity_key, reader.identity_key_length
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);
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pos = decode(
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pos, end, MESSAGE_TAG,
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reader.message, reader.message_length
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);
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if (unknown == pos) {
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pos = skip_unknown(pos, end);
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}
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}
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}
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static const std::uint8_t GROUP_MESSAGE_INDEX_TAG = 010;
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static const std::uint8_t GROUP_CIPHERTEXT_TAG = 022;
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size_t _olm_encode_group_message_length(
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uint32_t message_index,
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size_t ciphertext_length,
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size_t mac_length,
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size_t signature_length
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) {
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size_t length = VERSION_LENGTH;
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length += 1 + varint_length(message_index);
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length += 1 + varstring_length(ciphertext_length);
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length += mac_length;
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length += signature_length;
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return length;
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}
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size_t _olm_encode_group_message(
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uint8_t version,
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uint32_t message_index,
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size_t ciphertext_length,
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uint8_t *output,
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uint8_t **ciphertext_ptr
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) {
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std::uint8_t * pos = output;
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*(pos++) = version;
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pos = encode(pos, GROUP_MESSAGE_INDEX_TAG, message_index);
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pos = encode(pos, GROUP_CIPHERTEXT_TAG, *ciphertext_ptr, ciphertext_length);
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return pos-output;
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}
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void _olm_decode_group_message(
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const uint8_t *input, size_t input_length,
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size_t mac_length, size_t signature_length,
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struct _OlmDecodeGroupMessageResults *results
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) {
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std::uint8_t const * pos = input;
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std::size_t trailer_length = mac_length + signature_length;
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std::uint8_t const * end = input + input_length - trailer_length;
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std::uint8_t const * unknown = nullptr;
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bool has_message_index = false;
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results->message_index = 0;
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results->ciphertext = nullptr;
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results->ciphertext_length = 0;
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if (input_length < trailer_length) return;
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if (pos == end) return;
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results->version = *(pos++);
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while (pos != end) {
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unknown = pos;
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pos = decode(
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pos, end, GROUP_MESSAGE_INDEX_TAG,
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results->message_index, has_message_index
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);
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pos = decode(
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pos, end, GROUP_CIPHERTEXT_TAG,
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results->ciphertext, results->ciphertext_length
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);
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if (unknown == pos) {
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pos = skip_unknown(pos, end);
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}
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}
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results->has_message_index = (int)has_message_index;
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}
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