tdlight/td/mtproto/Handshake.cpp

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//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2021
//
// 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/Handshake.h"
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#include "td/mtproto/DhCallback.h"
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#include "td/mtproto/DhHandshake.h"
#include "td/mtproto/KDF.h"
#include "td/mtproto/mtproto_api.h"
#include "td/mtproto/utils.h"
#include "td/utils/as.h"
#include "td/utils/buffer.h"
#include "td/utils/common.h"
#include "td/utils/crypto.h"
#include "td/utils/format.h"
#include "td/utils/logging.h"
#include "td/utils/Random.h"
#include "td/utils/SliceBuilder.h"
#include "td/utils/Status.h"
#include "td/utils/Time.h"
#include "td/utils/tl_parsers.h"
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#include <algorithm>
namespace td {
namespace mtproto {
template <class T>
static Result<typename T::ReturnType> fetch_result(Slice message, bool check_end = true) {
TlParser parser(message);
auto result = T::fetch_result(parser);
if (check_end) {
parser.fetch_end();
}
const char *error = parser.get_error();
if (error != nullptr) {
LOG(ERROR) << "Can't parse: " << format::as_hex_dump<4>(message);
return Status::Error(500, Slice(error));
}
return std::move(result);
}
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AuthKeyHandshake::AuthKeyHandshake(int32 dc_id, int32 expires_in)
: mode_(expires_in == 0 ? Mode::Main : Mode::Temp)
, dc_id_(dc_id)
, expires_in_(expires_in)
, timeout_at_(Time::now() + 1e9) {
}
void AuthKeyHandshake::set_timeout_in(double timeout_in) {
timeout_at_ = Time::now() + timeout_in;
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}
void AuthKeyHandshake::clear() {
last_query_ = BufferSlice();
state_ = Start;
timeout_at_ = Time::now() + 1e9;
}
bool AuthKeyHandshake::is_ready_for_finish() const {
return state_ == Finish;
}
void AuthKeyHandshake::on_finish() {
clear();
}
string AuthKeyHandshake::store_object(const mtproto_api::Object &object) {
auto storer = create_storer(object);
size_t size = storer.size();
string result(size, '\0');
auto real_size = storer.store(MutableSlice(result).ubegin());
CHECK(real_size == size);
return result;
}
Status AuthKeyHandshake::on_res_pq(Slice message, Callback *connection, PublicRsaKeyInterface *public_rsa_key) {
TRY_RESULT(res_pq, fetch_result<mtproto_api::req_pq_multi>(message, false));
if (res_pq->nonce_ != nonce_) {
return Status::Error("Nonce mismatch");
}
server_nonce_ = res_pq->server_nonce_;
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auto r_rsa_key = public_rsa_key->get_rsa_key(res_pq->server_public_key_fingerprints_);
if (r_rsa_key.is_error()) {
public_rsa_key->drop_keys();
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return r_rsa_key.move_as_error();
}
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auto rsa_key = r_rsa_key.move_as_ok();
string p, q;
if (pq_factorize(res_pq->pq_, &p, &q) == -1) {
return Status::Error("Failed to factorize");
}
Random::secure_bytes(new_nonce_.raw, sizeof(new_nonce_));
string data;
switch (mode_) {
case Mode::Main:
data = store_object(mtproto_api::p_q_inner_data_dc(res_pq->pq_, p, q, nonce_, server_nonce_, new_nonce_, dc_id_));
break;
case Mode::Temp:
data = store_object(mtproto_api::p_q_inner_data_temp_dc(res_pq->pq_, p, q, nonce_, server_nonce_, new_nonce_,
dc_id_, expires_in_));
expires_at_ = Time::now() + expires_in_;
break;
default:
UNREACHABLE();
}
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string encrypted_data(256, '\0');
auto data_size = data.size();
if (data_size > 144) {
return Status::Error("Too big data");
}
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data.resize(192);
Random::secure_bytes(MutableSlice(data).substr(data_size));
while (true) {
string aes_key(32, '\0');
Random::secure_bytes(MutableSlice(aes_key));
string data_with_hash = data + sha256(aes_key + data);
std::reverse(data_with_hash.begin(), data_with_hash.begin() + data.size());
string decrypted_data(256, '\0');
string aes_iv(32, '\0');
aes_ige_encrypt(aes_key, aes_iv, data_with_hash, MutableSlice(decrypted_data).substr(32));
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auto hash = sha256(MutableSlice(decrypted_data).substr(32));
for (size_t i = 0; i < 32; i++) {
decrypted_data[i] = static_cast<char>(aes_key[i] ^ hash[i]);
}
if (rsa_key.rsa.encrypt(decrypted_data, encrypted_data)) {
break;
}
}
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mtproto_api::req_DH_params req_dh_params(nonce_, server_nonce_, p, q, rsa_key.fingerprint, encrypted_data);
send(connection, create_storer(req_dh_params));
state_ = ServerDHParams;
return Status::OK();
}
Status AuthKeyHandshake::on_server_dh_params(Slice message, Callback *connection, DhCallback *dh_callback) {
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TRY_RESULT(dh_params, fetch_result<mtproto_api::req_DH_params>(message, false));
// server_DH_params_ok#d0e8075c nonce:int128 server_nonce:int128 encrypted_answer:string = Server_DH_Params;
if (dh_params->nonce_ != nonce_) {
return Status::Error("Nonce mismatch");
}
if (dh_params->server_nonce_ != server_nonce_) {
return Status::Error("Server nonce mismatch");
}
if (dh_params->encrypted_answer_.size() & 15) {
return Status::Error("Bad padding for encrypted part");
}
UInt256 tmp_aes_key;
UInt256 tmp_aes_iv;
tmp_KDF(server_nonce_, new_nonce_, &tmp_aes_key, &tmp_aes_iv);
auto save_tmp_aes_iv = tmp_aes_iv;
// encrypted_answer := AES256_ige_encrypt (answer_with_hash, tmp_aes_key, tmp_aes_iv);
MutableSlice answer(const_cast<char *>(dh_params->encrypted_answer_.begin()), dh_params->encrypted_answer_.size());
aes_ige_decrypt(as_slice(tmp_aes_key), as_slice(tmp_aes_iv), answer, answer);
tmp_aes_iv = save_tmp_aes_iv;
// answer_with_hash := SHA1(answer) + answer + (0-15 random bytes)
TlParser answer_parser(answer);
UInt<160> answer_sha1 = answer_parser.fetch_binary<UInt<160>>();
int32 id = answer_parser.fetch_int();
if (id != mtproto_api::server_DH_inner_data::ID) {
return Status::Error("Failed to fetch server_DH_inner_data");
}
mtproto_api::server_DH_inner_data dh_inner_data(answer_parser);
if (answer_parser.get_error() != nullptr) {
return Status::Error("Failed to fetch server_DH_inner_data");
}
size_t pad = answer_parser.get_left_len();
if (pad >= 16) {
return Status::Error("Too much pad");
}
size_t dh_inner_data_size = answer.size() - pad - 20;
UInt<160> answer_real_sha1;
sha1(answer.substr(20, dh_inner_data_size), answer_real_sha1.raw);
if (answer_sha1 != answer_real_sha1) {
return Status::Error("SHA1 mismatch");
}
if (dh_inner_data.nonce_ != nonce_) {
return Status::Error("Nonce mismatch");
}
if (dh_inner_data.server_nonce_ != server_nonce_) {
return Status::Error("Server nonce mismatch");
}
server_time_diff_ = dh_inner_data.server_time_ - Time::now();
DhHandshake handshake;
handshake.set_config(dh_inner_data.g_, dh_inner_data.dh_prime_);
handshake.set_g_a(dh_inner_data.g_a_);
TRY_STATUS(handshake.run_checks(false, dh_callback));
string g_b = handshake.get_g_b();
auto auth_key_params = handshake.gen_key();
auto data = store_object(mtproto_api::client_DH_inner_data(nonce_, server_nonce_, 0, g_b));
size_t encrypted_data_size = 20 + data.size();
size_t encrypted_data_size_with_pad = (encrypted_data_size + 15) & -16;
string encrypted_data_str(encrypted_data_size_with_pad, '\0');
MutableSlice encrypted_data = encrypted_data_str;
sha1(data, encrypted_data.ubegin());
encrypted_data.substr(20, data.size()).copy_from(data);
Random::secure_bytes(encrypted_data.ubegin() + encrypted_data_size,
encrypted_data_size_with_pad - encrypted_data_size);
tmp_KDF(server_nonce_, new_nonce_, &tmp_aes_key, &tmp_aes_iv);
aes_ige_encrypt(as_slice(tmp_aes_key), as_slice(tmp_aes_iv), encrypted_data, encrypted_data);
mtproto_api::set_client_DH_params set_client_dh_params(nonce_, server_nonce_, encrypted_data);
send(connection, create_storer(set_client_dh_params));
auth_key_ = AuthKey(auth_key_params.first, std::move(auth_key_params.second));
if (mode_ == Mode::Temp) {
auth_key_.set_expires_at(expires_at_);
}
auth_key_.set_created_at(dh_inner_data.server_time_);
server_salt_ = as<int64>(new_nonce_.raw) ^ as<int64>(server_nonce_.raw);
state_ = DHGenResponse;
return Status::OK();
}
Status AuthKeyHandshake::on_dh_gen_response(Slice message, Callback *connection) {
TRY_RESULT(answer, fetch_result<mtproto_api::set_client_DH_params>(message, false));
switch (answer->get_id()) {
case mtproto_api::dh_gen_ok::ID:
state_ = Finish;
break;
case mtproto_api::dh_gen_fail::ID:
return Status::Error("DhGenFail");
case mtproto_api::dh_gen_retry::ID:
return Status::Error("DhGenRetry");
default:
return Status::Error("Unknown set_client_DH_params response");
}
return Status::OK();
}
void AuthKeyHandshake::send(Callback *connection, const Storer &storer) {
auto size = storer.size();
auto writer = BufferWriter{size, 0, 0};
auto real_size = storer.store(writer.as_slice().ubegin());
CHECK(real_size == size);
last_query_ = writer.as_buffer_slice();
return do_send(connection, create_storer(last_query_.as_slice()));
}
void AuthKeyHandshake::do_send(Callback *connection, const Storer &storer) {
return connection->send_no_crypto(storer);
}
void AuthKeyHandshake::resume(Callback *connection) {
if (state_ == Start) {
return on_start(connection).ignore();
}
if (state_ == Finish) {
LOG(ERROR) << "State is Finish during resume. UNREACHABLE";
return clear();
}
if (last_query_.empty()) {
LOG(ERROR) << "Last query empty! UNREACHABLE " << state_;
return clear();
}
LOG(INFO) << "Resume handshake";
do_send(connection, create_storer(last_query_.as_slice()));
}
Status AuthKeyHandshake::on_start(Callback *connection) {
if (state_ != Start) {
clear();
return Status::Error(PSLICE() << "on_start called after start " << tag("state", state_));
}
Random::secure_bytes(nonce_.raw, sizeof(nonce_));
send(connection, create_storer(mtproto_api::req_pq_multi(nonce_)));
state_ = ResPQ;
return Status::OK();
}
Status AuthKeyHandshake::on_message(Slice message, Callback *connection, AuthKeyHandshakeContext *context) {
Status status = [&] {
if (Time::now() >= timeout_at_) {
return Status::Error("Handshake timeout expired");
}
switch (state_) {
case ResPQ:
return on_res_pq(message, connection, context->get_public_rsa_key_interface());
case ServerDHParams:
return on_server_dh_params(message, connection, context->get_dh_callback());
case DHGenResponse:
return on_dh_gen_response(message, connection);
default:
UNREACHABLE();
}
}();
if (status.is_error()) {
clear();
}
return status;
}
} // namespace mtproto
} // namespace td