tdlight/td/mtproto/TcpTransport.h

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//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2024
//
// 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)
//
#pragma once
#include "td/mtproto/IStreamTransport.h"
#include "td/mtproto/ProxySecret.h"
#include "td/mtproto/TlsReaderByteFlow.h"
#include "td/mtproto/TransportType.h"
#include "td/utils/AesCtrByteFlow.h"
#include "td/utils/buffer.h"
#include "td/utils/ByteFlow.h"
#include "td/utils/common.h"
#include "td/utils/crypto.h"
#include "td/utils/port/detail/PollableFd.h"
#include "td/utils/Status.h"
#include "td/utils/UInt.h"
namespace td {
namespace mtproto {
namespace tcp {
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class IntermediateTransport {
public:
explicit IntermediateTransport(bool with_padding) : with_padding_(with_padding) {
}
// Writes a packet into message.
// Returns 0 if everything is ok, and [expected_size] otherwise.
// There is no sense to call this function when [stream->size > expected_size]
//
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// (TCP is a stream-oriented protocol, so the input message is a stream, not a slice)
size_t read_from_stream(ChainBufferReader *stream, BufferSlice *message, uint32 *quick_ack);
// Writes header inplace.
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void write_prepare_inplace(BufferWriter *message, bool quick_ack);
// Writes first several bytes into output stream.
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void init_output_stream(ChainBufferWriter *stream);
bool with_padding() const {
return with_padding_;
}
private:
bool with_padding_;
};
class OldTransport final : public IStreamTransport {
public:
OldTransport() = default;
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Result<size_t> read_next(BufferSlice *message, uint32 *quick_ack) final TD_WARN_UNUSED_RESULT {
return impl_.read_from_stream(input_, message, quick_ack);
}
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bool support_quick_ack() const final {
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return true;
}
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void write(BufferWriter &&message, bool quick_ack) final {
impl_.write_prepare_inplace(&message, quick_ack);
output_->append(message.as_buffer_slice());
}
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void init(ChainBufferReader *input, ChainBufferWriter *output) final {
input_ = input;
output_ = output;
impl_.init_output_stream(output_);
}
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bool can_read() const final {
return true;
}
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bool can_write() const final {
return true;
}
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size_t max_prepend_size() const final {
return 4;
}
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size_t max_append_size() const final {
return 15;
}
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TransportType get_type() const final {
return TransportType{TransportType::Tcp, 0, ProxySecret()};
}
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bool use_random_padding() const final {
return false;
}
private:
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IntermediateTransport impl_{false};
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ChainBufferReader *input_{nullptr};
ChainBufferWriter *output_{nullptr};
};
class ObfuscatedTransport final : public IStreamTransport {
public:
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ObfuscatedTransport(int16 dc_id, ProxySecret secret)
: dc_id_(dc_id), secret_(std::move(secret)), impl_(secret_.use_random_padding()) {
}
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Result<size_t> read_next(BufferSlice *message, uint32 *quick_ack) final TD_WARN_UNUSED_RESULT;
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bool support_quick_ack() const final {
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return true;
}
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void write(BufferWriter &&message, bool quick_ack) final;
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void init(ChainBufferReader *input, ChainBufferWriter *output) final;
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bool can_read() const final {
return true;
}
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bool can_write() const final {
return true;
}
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size_t max_prepend_size() const final {
size_t res = 4;
if (secret_.emulate_tls()) {
res += 5;
if (is_first_tls_packet_) {
res += 6;
}
}
res += header_.size();
if (res & 3) {
res += 4 - (res & 3);
}
return res;
}
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size_t max_append_size() const final {
return 15;
}
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TransportType get_type() const final {
return TransportType{TransportType::ObfuscatedTcp, dc_id_, secret_};
}
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bool use_random_padding() const final {
return secret_.use_random_padding();
}
private:
int16 dc_id_;
bool is_first_tls_packet_{true};
ProxySecret secret_;
std::string header_;
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IntermediateTransport impl_;
TlsReaderByteFlow tls_reader_byte_flow_;
AesCtrByteFlow aes_ctr_byte_flow_;
ByteFlowSink byte_flow_sink_;
ChainBufferReader *input_ = nullptr;
static constexpr int32 MAX_TLS_PACKET_LENGTH = 2878;
// TODO: use ByteFlow?
// One problem is that BufferedFd owns output_buffer_
// The other problem is that first 56 bytes must be sent unencrypted.
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UInt256 output_key_;
AesCtrState output_state_;
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ChainBufferWriter *output_ = nullptr;
void do_write_tls(BufferWriter &&message);
void do_write_tls(BufferBuilder &&builder);
void do_write_main(BufferWriter &&message);
void do_write(BufferSlice &&message);
};
using Transport = ObfuscatedTransport;
} // namespace tcp
} // namespace mtproto
} // namespace td