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@levlam @arseny30
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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
//
// 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/TcpTransport.h"
#include "td/utils/as.h"
#include "td/utils/common.h"
#include "td/utils/Random.h"
#include "td/utils/Slice.h"
#include <algorithm>
namespace td {
namespace mtproto {
namespace tcp {
size_t IntermediateTransport::read_from_stream(ChainBufferReader *stream, BufferSlice *message, uint32 *quick_ack) {
CHECK(message);
size_t stream_size = stream->size();
size_t header_size = 4;
if (stream->size() < header_size) {
return header_size;
}
uint32 data_size;
auto it = stream->clone();
it.advance(header_size, MutableSlice(reinterpret_cast<uint8 *>(&data_size), sizeof(data_size)));
if (data_size & (1u << 31)) {
if (quick_ack) {
*quick_ack = data_size;
}
stream->advance(header_size);
return 0;
}
size_t total_size = data_size + header_size;
if (stream_size < total_size) {
// optimization
// stream->make_solid(total_size);
return total_size;
}
stream->advance(header_size);
*message = stream->cut_head(data_size).move_as_buffer_slice();
return 0;
}
void IntermediateTransport::write_prepare_inplace(BufferWriter *message, bool quick_ack) {
size_t size = message->size();
CHECK(size % 4 == 0);
CHECK(size < (1 << 24));
if (quick_ack) {
size |= static_cast<size_t>(1) << 31;
}
size_t prepend_size = 4;
MutableSlice prepend = message->prepare_prepend();
CHECK(prepend.size() >= prepend_size);
message->confirm_prepend(prepend_size);
size_t append_size = 0;
if (with_padding()) {
append_size = Random::secure_uint32() % 16;
MutableSlice append = message->prepare_append().truncate(append_size);
CHECK(append.size() == append_size);
Random::secure_bytes(append);
message->confirm_append(append.size());
}
as<uint32>(message->as_slice().begin()) = static_cast<uint32>(size + append_size);
}
void IntermediateTransport::init_output_stream(ChainBufferWriter *stream) {
const uint32 magic = with_padding() ? 0xdddddddd : 0xeeeeeeee;
stream->append(Slice(reinterpret_cast<const char *>(&magic), 4));
}
size_t AbridgedTransport::read_from_stream(ChainBufferReader *stream, BufferSlice *message, uint32 *quick_ack) {
if (stream->empty()) {
return 1;
}
uint8 byte = 0;
stream->clone().advance(1, MutableSlice(&byte, 1));
size_t header_size;
uint32 data_size;
if (byte < 0x7f) {
header_size = 1;
data_size = byte * 4u;
} else {
if (stream->size() < 4) {
return 4;
}
header_size = 4;
stream->clone().advance(4, MutableSlice(reinterpret_cast<char *>(&data_size), sizeof(data_size)));
data_size >>= 8;
data_size = data_size * 4;
}
size_t total_size = header_size + data_size;
if (stream->size() < total_size) {
// optimization
// stream->make_solid(total_size);
return total_size;
}
stream->advance(header_size);
*message = stream->cut_head(data_size).move_as_buffer_slice();
return 0;
}
void AbridgedTransport::write_prepare_inplace(BufferWriter *message, bool quick_ack) {
CHECK(!quick_ack);
size_t size = message->size() / 4;
CHECK(size % 4 == 0);
CHECK(size < 1 << 24);
size_t prepend_size = size >= 0x7f ? 4 : 1;
MutableSlice prepend = message->prepare_prepend();
CHECK(prepend.size() >= prepend_size);
message->confirm_prepend(prepend_size);
MutableSlice data = message->as_slice();
if (size >= 0x7f) {
uint32 size_encoded = 0x7f + (static_cast<uint32>(size) << 8);
as<uint32>(data.begin()) = size_encoded;
} else {
as<uint8>(data.begin()) = static_cast<uint8>(size);
}
}
void AbridgedTransport::init_output_stream(ChainBufferWriter *stream) {
stream->append("\xef");
}
void ObfuscatedTransport::init(ChainBufferReader *input, ChainBufferWriter *output) {
input_ = input;
output_ = output;
const size_t header_size = 64;
string header(header_size, '\0');
MutableSlice header_slice = header;
int32 try_cnt = 0;
while (true) {
try_cnt++;
CHECK(try_cnt < 10);
Random::secure_bytes(header_slice.ubegin(), header.size());
if (secret_.emulate_tls()) {
break;
}
if (as<uint8>(header.data()) == 0xef) {
continue;
}
uint32 first_int = as<uint32>(header.data());
if (first_int == 0x44414548 || first_int == 0x54534f50 || first_int == 0x20544547 || first_int == 0x4954504f ||
first_int == 0xdddddddd || first_int == 0xeeeeeeee || first_int == 0x02010316) {
continue;
}
uint32 second_int = as<uint32>(header.data() + sizeof(uint32));
if (second_int == 0) {
continue;
}
break;
}
// TODO: It is actually IntermediateTransport::init_output_stream, so it will work only with
// TransportImpl==IntermediateTransport
as<uint32>(header_slice.begin() + 56) = impl_.with_padding() ? 0xdddddddd : 0xeeeeeeee;
if (dc_id_ != 0) {
as<int16>(header_slice.begin() + 60) = dc_id_;
}
string rheader = header;
std::reverse(rheader.begin(), rheader.end());
UInt256 key = as<UInt256>(rheader.data() + 8);
Slice proxy_secret = secret_.get_proxy_secret();
auto fix_key = [&](UInt256 &key) {
if (!proxy_secret.empty()) {
Sha256State state;
state.init();
state.feed(as_slice(key));
state.feed(proxy_secret);
state.extract(as_slice(key));
}
};
fix_key(key);
aes_ctr_byte_flow_.init(key, as<UInt128>(rheader.data() + 8 + 32));
if (secret_.emulate_tls()) {
tls_reader_byte_flow_.set_input(input_);
tls_reader_byte_flow_ >> aes_ctr_byte_flow_;
} else {
aes_ctr_byte_flow_.set_input(input_);
}
aes_ctr_byte_flow_ >> byte_flow_sink_;
output_key_ = as<UInt256>(header.data() + 8);
fix_key(output_key_);
output_state_.init(as_slice(output_key_), Slice(header.data() + 8 + 32, 16));
header_ = header;
output_state_.encrypt(header_slice, header_slice);
MutableSlice(header_).substr(56).copy_from(header_slice.substr(56));
}
Result<size_t> ObfuscatedTransport::read_next(BufferSlice *message, uint32 *quick_ack) {
if (secret_.emulate_tls()) {
tls_reader_byte_flow_.wakeup();
} else {
aes_ctr_byte_flow_.wakeup();
}
return impl_.read_from_stream(byte_flow_sink_.get_output(), message, quick_ack);
}
void ObfuscatedTransport::write(BufferWriter &&message, bool quick_ack) {
impl_.write_prepare_inplace(&message, quick_ack);
output_state_.encrypt(message.as_slice(), message.as_slice());
if (secret_.emulate_tls()) {
do_write_tls(std::move(message));
} else {
do_write_main(std::move(message));
}
}
void ObfuscatedTransport::do_write_main(BufferWriter &&message) {
BufferBuilder builder(std::move(message));
if (!header_.empty()) {
builder.prepend(header_);
header_ = {};
}
do_write(builder.extract());
}
void ObfuscatedTransport::do_write_tls(BufferWriter &&message) {
CHECK(header_.size() <= MAX_TLS_PACKET_LENGTH);
if (message.size() + header_.size() > MAX_TLS_PACKET_LENGTH) {
auto buffer_slice = message.as_buffer_slice();
auto slice = buffer_slice.as_slice();
while (!slice.empty()) {
auto buf = buffer_slice.from_slice(slice.substr(0, MAX_TLS_PACKET_LENGTH - header_.size()));
slice.remove_prefix(buf.size());
BufferBuilder builder;
builder.append(std::move(buf));
do_write_tls(std::move(builder));
}
return;
}
BufferBuilder builder(std::move(message));
do_write_tls(std::move(builder));
}
void ObfuscatedTransport::do_write_tls(BufferBuilder &&builder) {
if (!header_.empty()) {
builder.prepend(header_);
header_ = {};
}
size_t size = builder.size();
CHECK(size <= MAX_TLS_PACKET_LENGTH);
char buf[] = "\x17\x03\x03\x00\x00";
buf[3] = static_cast<char>((size >> 8) & 0xff);
buf[4] = static_cast<char>(size & 0xff);
builder.prepend(Slice(buf, 5));
if (is_first_tls_packet_) {
is_first_tls_packet_ = false;
Slice first_prefix("\x14\x03\x03\x00\x01\x01");
builder.prepend(first_prefix);
}
do_write(builder.extract());
}
void ObfuscatedTransport::do_write(BufferSlice &&slice) {
output_->append(std::move(slice));
}
} // namespace tcp
} // namespace mtproto
} // namespace td
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