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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2023
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include "td/mtproto/AuthData.h"
#include "td/utils/format.h"
#include "td/utils/logging.h"
#include "td/utils/Random.h"
#include "td/utils/SliceBuilder.h"
#include "td/utils/Time.h"
#include <algorithm>
namespace td {
namespace mtproto {
Status check_message_id_duplicates(int64 *saved_message_ids, size_t max_size, size_t &end_pos, int64 message_id) {
// In addition, the identifiers (msg_id) of the last N messages received from the other side must be stored, and if
// a message comes in with msg_id lower than all or equal to any of the stored values, that message is to be
// ignored. Otherwise, the new message msg_id is added to the set, and, if the number of stored msg_id values is
// greater than N, the oldest (i.e. the lowest) is forgotten.
if (end_pos == 2 * max_size) {
std::copy_n(&saved_message_ids[max_size], max_size, &saved_message_ids[0]);
end_pos = max_size;
}
if (end_pos == 0 || message_id > saved_message_ids[end_pos - 1]) {
// fast path
saved_message_ids[end_pos++] = message_id;
return Status::OK();
}
if (end_pos >= max_size && message_id < saved_message_ids[0]) {
return Status::Error(2, PSLICE() << "Ignore very old message " << message_id
<< " older than the oldest known message " << saved_message_ids[0]);
}
auto it = std::lower_bound(&saved_message_ids[0], &saved_message_ids[end_pos], message_id);
if (*it == message_id) {
return Status::Error(1, PSLICE() << "Ignore already processed message " << message_id);
}
std::copy_backward(it, &saved_message_ids[end_pos], &saved_message_ids[end_pos + 1]);
*it = message_id;
++end_pos;
return Status::OK();
}
AuthData::AuthData() {
server_salt_.salt = Random::secure_int64();
server_salt_.valid_since = -1e10;
server_salt_.valid_until = -1e10;
}
bool AuthData::is_ready(double now) {
if (!has_main_auth_key()) {
LOG(INFO) << "Need main auth key";
return false;
}
if (use_pfs() && !has_tmp_auth_key(now)) {
LOG(INFO) << "Need tmp auth key";
return false;
}
if (!has_salt(now)) {
LOG(INFO) << "Need salt";
return false;
}
return true;
}
bool AuthData::update_server_time_difference(double diff) {
if (!server_time_difference_was_updated_) {
server_time_difference_was_updated_ = true;
LOG(DEBUG) << "UPDATE_SERVER_TIME_DIFFERENCE: " << server_time_difference_ << " -> " << diff;
server_time_difference_ = diff;
} else if (server_time_difference_ + 1e-4 < diff) {
LOG(DEBUG) << "UPDATE_SERVER_TIME_DIFFERENCE: " << server_time_difference_ << " -> " << diff;
server_time_difference_ = diff;
} else {
return false;
}
LOG(DEBUG) << "SERVER_TIME: " << format::as_hex(static_cast<int32>(get_server_time(Time::now_cached())));
return true;
}
void AuthData::set_future_salts(const std::vector<ServerSalt> &salts, double now) {
if (salts.empty()) {
return;
}
future_salts_ = salts;
std::sort(future_salts_.begin(), future_salts_.end(),
[](const ServerSalt &a, const ServerSalt &b) { return a.valid_since > b.valid_since; });
update_salt(now);
}
std::vector<ServerSalt> AuthData::get_future_salts() const {
auto res = future_salts_;
res.push_back(server_salt_);
return res;
}
int64 AuthData::next_message_id(double now) {
double server_time = get_server_time(now);
auto t = static_cast<int64>(server_time * (static_cast<int64>(1) << 32));
// randomize lower bits for clocks with low precision
// TODO(perf) do not do this for systems with good precision?..
auto rx = Random::secure_int32();
auto to_xor = rx & ((1 << 22) - 1);
auto to_mul = ((rx >> 22) & 1023) + 1;
t ^= to_xor;
auto result = t & -4;
if (last_message_id_ >= result) {
result = last_message_id_ + 8 * to_mul;
}
last_message_id_ = result;
return result;
}
bool AuthData::is_valid_outbound_msg_id(int64 id, double now) const {
double server_time = get_server_time(now);
auto id_time = static_cast<double>(id) / static_cast<double>(static_cast<int64>(1) << 32);
return server_time - 150 < id_time && id_time < server_time + 30;
}
bool AuthData::is_valid_inbound_msg_id(int64 id, double now) const {
double server_time = get_server_time(now);
auto id_time = static_cast<double>(id) / static_cast<double>(static_cast<int64>(1) << 32);
return server_time - 300 < id_time && id_time < server_time + 30;
}
Status AuthData::check_packet(int64 session_id, int64 message_id, double now, bool &time_difference_was_updated) {
// Client is to check that the session_id field in the decrypted message indeed equals to that of an active session
// created by the client.
if (get_session_id() != static_cast<uint64>(session_id)) {
return Status::Error(PSLICE() << "Receive packet from different session " << session_id << " in session "
<< get_session_id());
}
// Client must check that msg_id has even parity for messages from client to server, and odd parity for messages
// from server to client.
if ((message_id & 1) == 0) {
return Status::Error(PSLICE() << "Receive invalid message identifier " << message_id);
}
TRY_STATUS(duplicate_checker_.check(message_id));
time_difference_was_updated = update_server_time_difference(static_cast<uint32>(message_id >> 32) - now);
// In addition, msg_id values that belong over 30 seconds in the future or over 300 seconds in the past are to be
// ignored (recall that msg_id approximately equals unixtime * 2^32). This is especially important for the server.
// The client would also find this useful (to protect from a replay attack), but only if it is certain of its time
// (for example, if its time has been synchronized with that of the server).
if (server_time_difference_was_updated_ && !is_valid_inbound_msg_id(message_id, now)) {
return Status::Error(PSLICE() << "Ignore too old or too new message " << message_id);
}
return Status::OK();
}
void AuthData::update_salt(double now) {
double server_time = get_server_time(now);
while (!future_salts_.empty() && (future_salts_.back().valid_since < server_time)) {
server_salt_ = future_salts_.back();
future_salts_.pop_back();
}
}
} // namespace mtproto
} // namespace td
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