ObfuscatedTransport: support of emulated_tls flag

GitOrigin-RevId: f0ae7ddb21455d4e8d8c3f486744b1b9643bf2d5

CMakeLists.txt

@@ -348,6 +348,7 @@ set(TDLIB_SOURCE
   td/mtproto/RawConnection.cpp
   td/mtproto/SessionConnection.cpp
   td/mtproto/TcpTransport.cpp
+  td/mtproto/TlsReaderByteFlow.cpp
   td/mtproto/Transport.cpp
   td/mtproto/utils.cpp
 
@@ -478,6 +479,7 @@ set(TDLIB_SOURCE
   td/mtproto/RawConnection.h
   td/mtproto/SessionConnection.h
   td/mtproto/TcpTransport.h
+  td/mtproto/TlsReaderByteFlow.h
   td/mtproto/Transport.h
   td/mtproto/TransportType.h
   td/mtproto/utils.h

td/mtproto/IStreamTransport.cpp

@@ -15,7 +15,7 @@ namespace mtproto {
 unique_ptr<IStreamTransport> create_transport(TransportType type) {
   switch (type.type) {
     case TransportType::ObfuscatedTcp:
-      return td::make_unique<tcp::ObfuscatedTransport>(type.dc_id, std::move(type.secret));
+      return td::make_unique<tcp::ObfuscatedTransport>(type.dc_id, std::move(type.secret), type.emulate_tls);
     case TransportType::Tcp:
       return td::make_unique<tcp::OldTransport>();
     case TransportType::Http:

td/mtproto/TcpTransport.cpp

@@ -184,7 +184,12 @@ void ObfuscatedTransport::init(ChainBufferReader *input, ChainBufferWriter *outp
   };
   fix_key(key);
   aes_ctr_byte_flow_.init(key, as<UInt128>(rheader.data() + 8 + 32));
-  aes_ctr_byte_flow_.set_input(input_);
+  if (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);
@@ -195,6 +200,67 @@ void ObfuscatedTransport::init(ChainBufferReader *input, ChainBufferWriter *outp
   output_->append(header_slice.substr(56, 8));
 }
 
+Result<size_t> ObfuscatedTransport::read_next(BufferSlice *message, uint32 *quick_ack) {
+  if (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 (emulate_tls_) {
+    do_write_tls(std::move(message));
+  } else {
+    do_write(message.as_buffer_slice());
+  }
+}
+
+void ObfuscatedTransport::do_write_tls(BufferWriter &&message) {
+  size_t size = message.size();
+
+  if (size > (1 << 14)) {
+    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, 1 << 14));
+      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) {
+  size_t size = builder.size();
+  CHECK(size <= (1 << 14));
+
+  char buf[] = "\x17\x03\x03\x00\x00";
+  buf[3] = (size >> 8) & 0xff;
+  buf[4] = 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

td/mtproto/TcpTransport.h

@@ -8,6 +8,7 @@
 
 #include "td/mtproto/IStreamTransport.h"
 #include "td/mtproto/TransportType.h"
+#include "td/mtproto/TlsReaderByteFlow.h"
 
 #include "td/utils/AesCtrByteFlow.h"
 #include "td/utils/buffer.h"
@@ -122,24 +123,17 @@ class OldTransport : public IStreamTransport {
 
 class ObfuscatedTransport : public IStreamTransport {
  public:
-  ObfuscatedTransport(int16 dc_id, std::string secret)
-      : dc_id_(dc_id), secret_(std::move(secret)), impl_(secret_.size() >= 17) {
-  }
-  Result<size_t> read_next(BufferSlice *message, uint32 *quick_ack) override TD_WARN_UNUSED_RESULT {
-    aes_ctr_byte_flow_.wakeup();
-    return impl_.read_from_stream(byte_flow_sink_.get_output(), message, quick_ack);
+  ObfuscatedTransport(int16 dc_id, std::string secret, bool emulate_tls)
+      : dc_id_(dc_id), secret_(std::move(secret)), emulate_tls_(emulate_tls), impl_(secret_.size() >= 17) {
   }
 
+  Result<size_t> read_next(BufferSlice *message, uint32 *quick_ack) override TD_WARN_UNUSED_RESULT;
+
   bool support_quick_ack() const override {
     return impl_.support_quick_ack();
   }
 
-  void write(BufferWriter &&message, bool quick_ack) override {
-    impl_.write_prepare_inplace(&message, quick_ack);
-    auto slice = message.as_buffer_slice();
-    output_state_.encrypt(slice.as_slice(), slice.as_slice());
-    output_->append(std::move(slice));
-  }
+  void write(BufferWriter &&message, bool quick_ack) override;
 
   void init(ChainBufferReader *input, ChainBufferWriter *output) override;
 
@@ -152,7 +146,14 @@ class ObfuscatedTransport : public IStreamTransport {
   }
 
   size_t max_prepend_size() const override {
-    return 4;
+    size_t res = 4;
+    if (emulate_tls_) {
+      res += 5;
+      if (is_first_tls_packet_) {
+        res += 6;
+      }
+    }
+    return res;
   }
 
   size_t max_append_size() const override {
@@ -166,7 +167,10 @@ class ObfuscatedTransport : public IStreamTransport {
  private:
   int16 dc_id_;
   std::string secret_;
+  bool emulate_tls_;
+  bool is_first_tls_packet_{true};
   TransportImpl impl_;
+  TlsReaderByteFlow tls_reader_byte_flow_;
   AesCtrByteFlow aes_ctr_byte_flow_;
   ByteFlowSink byte_flow_sink_;
   ChainBufferReader *input_;
@@ -177,6 +181,10 @@ class ObfuscatedTransport : public IStreamTransport {
   UInt256 output_key_;
   AesCtrState output_state_;
   ChainBufferWriter *output_;
+
+  void do_write_tls(BufferWriter &&message);
+  void do_write_tls(BufferBuilder &&builder);
+  void do_write(BufferSlice &&message);
 };
 
 using Transport = ObfuscatedTransport;

td/mtproto/TlsReaderByteFlow.cpp

@@ -0,0 +1,43 @@
+//
+// 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/TlsReaderByteFlow.h"
+
+#include "td/utils/Status.h"
+
+namespace td {
+
+void TlsReaderByteFlow::loop() {
+  while (true) {
+    if (input_->size() < 5) {
+      set_need_size(5);
+      return;
+    }
+
+    auto it = input_->clone();
+    uint8 buf[5];
+    it.advance(5, MutableSlice(buf, 5));
+    if (Slice(buf, 3) != Slice("\x17\x03\x03")) {
+      close_input(td::Status::Error("Invalid bytes at the beginning of a packet (emulated tls)"));
+      return;
+    }
+    size_t len = (buf[3] << 8) | buf[4];
+    if (len > (1 << 14)) {
+      close_input(td::Status::Error("Packet lenght is too big (emulated tls)"));
+      return;
+    }
+
+    if (it.size() < len) {
+      set_need_size(5 + len);
+      return;
+    }
+
+    output_.append(it.cut_head(len));
+    *input_ = std::move(it);
+  }
+}
+
+}  // namespace td

td/mtproto/TlsReaderByteFlow.h

@@ -0,0 +1,19 @@
+//
+// 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)
+//
+#pragma once
+
+#include "td/utils/ByteFlow.h"
+
+namespace td {
+
+class TlsReaderByteFlow final : public ByteFlowBase {
+ public:
+  TlsReaderByteFlow() = default;
+  void loop() override;
+};
+
+}  // namespace td

td/mtproto/TransportType.h

@@ -12,13 +12,14 @@ namespace td {
 namespace mtproto {
 
 struct TransportType {
-  enum Type { Tcp, ObfuscatedTcp, Http } type;
-  int16 dc_id;
+  enum Type { Tcp, ObfuscatedTcp, Http } type = Tcp;
+  int16 dc_id{0};
   string secret;
+  bool emulate_tls{false};
 
-  TransportType() : type(Tcp), dc_id(0), secret() {
-  }
-  TransportType(Type type, int16 dc_id, string secret) : type(type), dc_id(dc_id), secret(std::move(secret)) {
+  TransportType() = default;
+  TransportType(Type type, int16 dc_id, string secret, bool emulate_tls = false)
+      : type(type), dc_id(dc_id), secret(std::move(secret)), emulate_tls(emulate_tls) {
   }
 };
 

tdutils/td/utils/buffer.cpp

@@ -133,10 +133,9 @@ BufferSlice BufferBuilder::extract() {
   if (to_append_.empty() && to_prepend_.empty()) {
     return buffer_writer_.as_buffer_slice();
   }
-  size_t total_size = 0;
-  for_each([&](auto &&slice) { total_size += slice.size(); });
+  size_t total_size = size();
   BufferWriter writer(0, 0, total_size);
-  for_each([&](auto &&slice) {
+  std::move(*this).for_each([&](auto &&slice) {
     writer.prepare_append().truncate(slice.size()).copy_from(slice.as_slice());
     writer.confirm_append(slice.size());
   });
@@ -144,6 +143,12 @@ BufferSlice BufferBuilder::extract() {
   return writer.as_buffer_slice();
 }
 
+size_t BufferBuilder::size() const {
+  size_t total_size = 0;
+  for_each([&](auto &&slice) { total_size += slice.size(); });
+  return total_size;
+}
+
 bool BufferBuilder::append_inplace(Slice slice) {
   if (!to_append_.empty()) {
     return false;

tdutils/td/utils/buffer.h

@@ -731,6 +731,8 @@ class BufferBuilder {
   BufferBuilder(Slice slice, size_t prepend_size, size_t append_size)
       : buffer_writer_(slice, prepend_size, append_size) {
   }
+  explicit BufferBuilder(BufferWriter &&buffer_writer) : buffer_writer_(std::move(buffer_writer)) {
+  }
 
   void append(BufferSlice slice);
   void append(Slice slice);
@@ -739,7 +741,7 @@ class BufferBuilder {
   void prepend(Slice slice);
 
   template <class F>
-  void for_each(F &&f) {
+  void for_each(F &&f) const & {
     for (auto &slice : reversed(to_prepend_)) {
       f(slice);
     }
@@ -750,6 +752,19 @@ class BufferBuilder {
       f(slice);
     }
   }
+  template <class F>
+  void for_each(F &&f) && {
+    for (auto &slice : reversed(to_prepend_)) {
+      f(std::move(slice));
+    }
+    if (!buffer_writer_.empty()) {
+      f(buffer_writer_.as_buffer_slice());
+    }
+    for (auto &slice : to_append_) {
+      f(std::move(slice));
+    }
+  }
+  size_t size() const;
 
   BufferSlice extract();