177 lines
6.6 KiB
C++
177 lines
6.6 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2023
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#include "td/mtproto/AuthData.h"
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#include "td/utils/format.h"
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#include "td/utils/logging.h"
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#include "td/utils/Random.h"
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#include "td/utils/SliceBuilder.h"
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#include "td/utils/Time.h"
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#include <algorithm>
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namespace td {
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namespace mtproto {
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Status check_message_id_duplicates(uint64 *saved_message_ids, size_t max_size, size_t &end_pos, uint64 message_id) {
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// In addition, the identifiers (msg_id) of the last N messages received from the other side must be stored, and if
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// a message comes in with msg_id lower than all or equal to any of the stored values, that message is to be
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// ignored. Otherwise, the new message msg_id is added to the set, and, if the number of stored msg_id values is
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// greater than N, the oldest (i.e. the lowest) is forgotten.
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if (end_pos == 2 * max_size) {
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std::copy_n(&saved_message_ids[max_size], max_size, &saved_message_ids[0]);
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end_pos = max_size;
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}
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if (end_pos == 0 || message_id > saved_message_ids[end_pos - 1]) {
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// fast path
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saved_message_ids[end_pos++] = message_id;
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return Status::OK();
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}
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if (end_pos >= max_size && message_id < saved_message_ids[0]) {
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return Status::Error(2, PSLICE() << "Ignore very old message " << message_id
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<< " older than the oldest known message " << saved_message_ids[0]);
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}
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auto it = std::lower_bound(&saved_message_ids[0], &saved_message_ids[end_pos], message_id);
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if (*it == message_id) {
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return Status::Error(1, PSLICE() << "Ignore already processed message " << message_id);
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}
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std::copy_backward(it, &saved_message_ids[end_pos], &saved_message_ids[end_pos + 1]);
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*it = message_id;
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++end_pos;
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return Status::OK();
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}
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AuthData::AuthData() {
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server_salt_.salt = Random::secure_int64();
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server_salt_.valid_since = -1e10;
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server_salt_.valid_until = -1e10;
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}
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bool AuthData::is_ready(double now) {
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if (!has_main_auth_key()) {
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LOG(INFO) << "Need main auth key";
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return false;
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}
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if (use_pfs() && !has_tmp_auth_key(now)) {
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LOG(INFO) << "Need tmp auth key";
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return false;
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}
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if (!has_salt(now)) {
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LOG(INFO) << "Need salt";
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return false;
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}
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return true;
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}
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bool AuthData::update_server_time_difference(double diff) {
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if (!server_time_difference_was_updated_) {
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LOG(DEBUG) << "Set server time difference: " << server_time_difference_ << " -> " << diff;
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server_time_difference_was_updated_ = true;
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server_time_difference_ = diff;
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} else if (server_time_difference_ + 1e-4 < diff) {
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LOG(DEBUG) << "Update server time difference: " << server_time_difference_ << " -> " << diff;
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server_time_difference_ = diff;
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} else {
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return false;
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}
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LOG(DEBUG) << "New server time: " << get_server_time(Time::now_cached());
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return true;
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}
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void AuthData::reset_server_time_difference(double diff) {
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LOG(DEBUG) << "Reset server time difference: " << server_time_difference_ << " -> " << diff;
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server_time_difference_was_updated_ = false;
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server_time_difference_ = diff;
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}
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void AuthData::set_future_salts(const std::vector<ServerSalt> &salts, double now) {
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if (salts.empty()) {
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return;
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}
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future_salts_ = salts;
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std::sort(future_salts_.begin(), future_salts_.end(),
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[](const ServerSalt &a, const ServerSalt &b) { return a.valid_since > b.valid_since; });
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update_salt(now);
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}
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std::vector<ServerSalt> AuthData::get_future_salts() const {
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auto res = future_salts_;
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res.push_back(server_salt_);
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return res;
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}
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uint64 AuthData::next_message_id(double now) {
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double server_time = get_server_time(now);
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auto t = static_cast<uint64>(server_time * (static_cast<uint64>(1) << 32));
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// randomize lower bits for clocks with low precision
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// TODO(perf) do not do this for systems with good precision?..
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auto rx = Random::secure_int32();
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auto to_xor = rx & ((1 << 22) - 1);
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auto to_mul = ((rx >> 22) & 1023) + 1;
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t ^= to_xor;
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auto result = t & static_cast<uint64>(-4);
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if (last_message_id_ >= result) {
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result = last_message_id_ + 8 * to_mul;
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}
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last_message_id_ = result;
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return result;
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}
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bool AuthData::is_valid_outbound_msg_id(uint64 message_id, double now) const {
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double server_time = get_server_time(now);
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auto id_time = static_cast<double>(message_id) / static_cast<double>(static_cast<uint64>(1) << 32);
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return server_time - 150 < id_time && id_time < server_time + 30;
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}
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bool AuthData::is_valid_inbound_msg_id(uint64 message_id, double now) const {
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double server_time = get_server_time(now);
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auto id_time = static_cast<double>(message_id) / static_cast<double>(static_cast<uint64>(1) << 32);
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return server_time - 300 < id_time && id_time < server_time + 30;
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}
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Status AuthData::check_packet(uint64 session_id, uint64 message_id, double now, bool &time_difference_was_updated) {
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// Client is to check that the session_id field in the decrypted message indeed equals to that of an active session
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// created by the client.
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if (get_session_id() != session_id) {
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return Status::Error(PSLICE() << "Receive packet from different session " << session_id << " in session "
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<< get_session_id());
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}
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// Client must check that msg_id has even parity for messages from client to server, and odd parity for messages
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// from server to client.
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if ((message_id & 1) == 0) {
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return Status::Error(PSLICE() << "Receive invalid message identifier " << message_id);
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}
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TRY_STATUS(duplicate_checker_.check(message_id));
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time_difference_was_updated = update_server_time_difference(static_cast<uint32>(message_id >> 32) - now);
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// In addition, msg_id values that belong over 30 seconds in the future or over 300 seconds in the past are to be
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// ignored (recall that msg_id approximately equals unixtime * 2^32). This is especially important for the server.
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// The client would also find this useful (to protect from a replay attack), but only if it is certain of its time
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// (for example, if its time has been synchronized with that of the server).
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if (server_time_difference_was_updated_ && !is_valid_inbound_msg_id(message_id, now)) {
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return Status::Error(PSLICE() << "Ignore too old or too new message " << message_id);
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}
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return Status::OK();
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}
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void AuthData::update_salt(double now) {
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double server_time = get_server_time(now);
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while (!future_salts_.empty() && (future_salts_.back().valid_since < server_time)) {
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server_salt_ = future_salts_.back();
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future_salts_.pop_back();
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}
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}
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} // namespace mtproto
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} // namespace td
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