TlsObfuscation: TlsInit actor draft

GitOrigin-RevId: 71f79ac151ee71d825c94733345d442a68e57496

test/mtproto.cpp

@@ -29,12 +29,15 @@
 #include "td/telegram/net/Session.h"
 #include "td/telegram/NotificationManager.h"
 
+#include "td/utils/as.h"
 #include "td/utils/base64.h"
 #include "td/utils/common.h"
+#include "td/utils/crypto.h"
 #include "td/utils/logging.h"
 #include "td/utils/port/IPAddress.h"
 #include "td/utils/port/SocketFd.h"
 #include "td/utils/Random.h"
+#include "td/utils/Span.h"
 #include "td/utils/Status.h"
 #include "td/utils/Time.h"
 
@@ -586,3 +589,445 @@ class Mtproto_FastPing : public Test {
   Status result_;
 };
 RegisterTest<Mtproto_FastPing> mtproto_fastping("Mtproto_FastPing");
+
+class Grease {
+ public:
+  static void init(MutableSlice res) {
+    Random::secure_bytes(res);
+    for (auto &c : res) {
+      c = (c & 0xF0) + 0x0A;
+    }
+    for (size_t i = 1; i < res.size(); i += 2) {
+      if (res[i] == res[i - 1]) {
+        res[i] ^= 0x10;
+      }
+    }
+  }
+};
+
+class TlsHello {
+ public:
+  struct Op {
+    enum class Type { String, Random, Zero, Domain, Grease, BeginScope, EndScope };
+    Type type;
+    int length;
+    int seed;
+    std::string data;
+
+    static Op string(Slice str) {
+      Op res;
+      res.type = Type::String;
+      res.data = str.str();
+      return res;
+    }
+    static Op random(int length) {
+      Op res;
+      res.type = Type::Random;
+      res.length = length;
+      return res;
+    }
+    static Op zero(int length) {
+      Op res;
+      res.type = Type::Zero;
+      res.length = length;
+      return res;
+    }
+    static Op domain() {
+      Op res;
+      res.type = Type::Domain;
+      return res;
+    }
+    static Op grease(int seed) {
+      Op res;
+      res.type = Type::Grease;
+      res.seed = seed;
+      return res;
+    }
+    static Op begin_scope() {
+      Op res;
+      res.type = Type::BeginScope;
+      return res;
+    }
+    static Op end_scope() {
+      Op res;
+      res.type = Type::EndScope;
+      return res;
+    }
+  };
+
+  static const TlsHello &get_default() {
+    static TlsHello res = [] {
+      TlsHello res;
+      res.ops_ = {
+          Op::string("\x16\x03\x01\x02\x00\x01\x00\x01\xfc\x03\x03"),
+          Op::zero(32),
+          Op::string("\x20"),
+          Op::random(32),
+          Op::string("\x00\x22"),
+          Op::grease(0),
+          Op::string("\x13\x01\x13\x02\x13\x03\xc0\x2b\xc0\x2f\xc0\x2c\xc0\x30\xcc\xa9\xcc\xa8\xc0\x13\xc0\x14\x00\x9c"
+                     "\x00\x9d\x00\x2f\x00\x35\x00\x0a\x01\x00\x01\x91"),
+          Op::grease(2),
+          Op::string("\x00\x00\x00\x00"),
+          Op::begin_scope(),
+          Op::begin_scope(),
+          Op::string("\x00"),
+          Op::begin_scope(),
+          Op::domain(),
+          Op::end_scope(),
+          Op::end_scope(),
+          Op::end_scope(),
+          Op::string("\x00\x17\x00\x00\xff\x01\x00\x01\x00\x00\x0a\x00\x0a\x00\x08"),
+          Op::grease(4),
+          Op::string(
+              "\x00\x1d\x00\x17\x00\x18\x00\x0b\x00\x02\x01\x00\x00\x23\x00\x00\x00\x10\x00\x0e\x00\x0c\x02\x68\x32\x08"
+              "\x68\x74\x74\x70\x2f\x31\x2e\x31\x00\x05\x00\x05\x01\x00\x00\x00\x00\x00\x0d\x00\x14\x00\x12\x04\x03\x08"
+              "\x04\x04\x01\x05\x03\x08\x05\x05\x01\x08\x06\x06\x01\x02\x01\x00\x12\x00\x00\x00\x33\x00\x2b\x00\x29"),
+          Op::grease(4),
+          Op::string("\x00\x01\x00\x00\x1d\x00\x20"),
+          Op::random(32),
+          Op::string("\x00\x2d\x00\x02\x01\x01\x00\x2b\x00\x0b\x0a"),
+          Op::grease(6),
+          Op::string("\x03\x04\x03\x03\x03\x02\x03\x01\x00\x1b\x00\x03\x02\x00\x02"),
+          Op::grease(3),
+          Op::string("\x00\x01\x00\x00\x15")};
+      return res;
+    }();
+    return res;
+  }
+  Span<Op> get_ops() const {
+    return ops_;
+  }
+
+ private:
+  std::vector<Op> ops_;
+};
+
+class TlsHelloContext {
+ public:
+  explicit TlsHelloContext(std::string domain) {
+    Grease::init(MutableSlice(grease_.data(), grease_.size()));
+    domain_ = std::move(domain);
+  }
+  char get_grease(size_t i) const {
+    CHECK(i < grease_.size());
+    return grease_[i];
+  }
+  size_t grease_size() const {
+    return grease_.size();
+  }
+  Slice get_domain() const {
+    return domain_;
+  }
+
+ private:
+  constexpr static size_t MAX_GREASE = 8;
+  std::array<char, MAX_GREASE> grease_;
+  std::string domain_;
+};
+
+class TlsHelloCalcLength {
+ public:
+  void do_op(const TlsHello::Op &op, const TlsHelloContext *context) {
+    using Type = TlsHello::Op::Type;
+    switch (op.type) {
+      case Type::String:
+        size_ += op.data.size();
+        break;
+      case Type::Random:
+        if (op.length <= 0 || op.length > 1024) {
+          on_error(Status::Error("Invalid random length"));
+        }
+        size_ += op.length;
+        break;
+      case Type::Zero:
+        if (op.length < 0 || op.length > 1024) {
+          on_error(Status::Error("Invalid zero length"));
+        }
+        size_ += op.length;
+        break;
+      case Type::Domain:
+        CHECK(context);
+        size_ += context->get_domain().size();
+        break;
+      case Type::Grease:
+        CHECK(context);
+        if (op.seed < 0 || static_cast<size_t>(op.seed) > context->grease_size()) {
+          on_error(Status::Error("Invalid grease seed"));
+        }
+        size_ += 2;
+        break;
+      case Type::BeginScope:
+        size_ += 2;
+        scope_offset_.push_back(size_);
+        break;
+      case Type::EndScope:
+        if (scope_offset_.empty()) {
+          on_error(Status::Error("Unbalanced scopes"));
+        }
+        auto begin_offset = scope_offset_.back();
+        scope_offset_.pop_back();
+        auto end_offset = size_;
+        auto size = end_offset - begin_offset;
+        if (size >= (1 << 14)) {
+          on_error(Status::Error("Scope is too big"));
+        }
+        break;
+    }
+  }
+
+  Result<int64> finish() {
+    if (size_ > 515) {
+      on_error(Status::Error("Too long for zero padding"));
+    }
+    if (size_ < 11 + 32) {
+      on_error(Status::Error("Too small for hash"));
+    }
+    int zero_pad = 515 - static_cast<int>(size_);
+    using Op = TlsHello::Op;
+    do_op(Op::begin_scope(), nullptr);
+    do_op(Op::zero(zero_pad), nullptr);
+    do_op(Op::end_scope(), nullptr);
+    if (!scope_offset_.empty()) {
+      on_error(Status::Error("Unbalanced scopes"));
+    }
+    TRY_STATUS(std::move(status_));
+    return size_;
+  }
+
+ private:
+  int64 size_{0};
+  Status status_;
+  std::vector<size_t> scope_offset_;
+
+  void on_error(Status error) {
+    if (status_.is_ok()) {
+      status_ = std::move(error);
+    }
+  }
+};
+
+class TlsHelloStore {
+ public:
+  TlsHelloStore(MutableSlice dest) : data_(dest), dest_(dest) {
+  }
+  void do_op(const TlsHello::Op &op, TlsHelloContext *context) {
+    using Type = TlsHello::Op::Type;
+    switch (op.type) {
+      case Type::String:
+        dest_.copy_from(op.data);
+        dest_.remove_prefix(op.data.size());
+        break;
+      case Type::Random:
+        Random::secure_bytes(dest_.substr(0, op.length));
+        dest_.remove_prefix(op.length);
+        break;
+      case Type::Zero:
+        std::memset(dest_.begin(), 0, op.length);
+        dest_.remove_prefix(op.length);
+        break;
+      case Type::Domain: {
+        CHECK(context);
+        auto domain = context->get_domain();
+        dest_.copy_from(domain);
+        dest_.remove_prefix(domain.size());
+        break;
+      }
+      case Type::Grease: {
+        CHECK(context)
+        auto grease = context->get_grease(op.seed);
+        dest_[0] = grease;
+        dest_[1] = grease;
+        dest_.remove_prefix(2);
+        break;
+      }
+      case Type::BeginScope:
+        scope_offset_.push_back(get_offset());
+        dest_.remove_prefix(2);
+        break;
+      case Type::EndScope: {
+        CHECK(!scope_offset_.empty());
+        auto begin_offset = scope_offset_.back();
+        scope_offset_.pop_back();
+        auto end_offset = get_offset();
+        size_t size = end_offset - begin_offset - 2;
+        CHECK(size < (1 << 14));
+        data_[begin_offset] = static_cast<char>((size >> 8) & 0xff);
+        data_[begin_offset + 1] = static_cast<char>(size & 0xff);
+        break;
+      }
+    }
+  }
+  void finish(int32 unix_time) {
+    int zero_pad = 515 - static_cast<int>(get_offset());
+    using Op = TlsHello::Op;
+    do_op(Op::begin_scope(), nullptr);
+    do_op(Op::zero(zero_pad), nullptr);
+    do_op(Op::end_scope(), nullptr);
+
+    auto tmp = sha256(data_);
+    auto hash_dest = data_.substr(11);
+    hash_dest.copy_from(tmp);
+    int32 old = as<int32>(hash_dest.substr(28).data());
+    as<int32>(hash_dest.substr(28).data()) = old ^ unix_time;
+    CHECK(dest_.empty());
+  }
+
+ private:
+  MutableSlice data_;
+  MutableSlice dest_;
+  std::vector<size_t> scope_offset_;
+  size_t get_offset() {
+    return data_.size() - dest_.size();
+  }
+};
+
+class TlsObfusaction {
+ public:
+  static std::string generate_header(std::string domain, int32 unix_time) {
+    auto &hello = TlsHello::get_default();
+    TlsHelloContext context(domain);
+    TlsHelloCalcLength calc_length;
+    for (auto &op : hello.get_ops()) {
+      calc_length.do_op(op, &context);
+    }
+    auto length = calc_length.finish().move_as_ok();
+    std::string data(length, 0);
+    TlsHelloStore storer(data);
+    for (auto &op : hello.get_ops()) {
+      storer.do_op(op, &context);
+    }
+    storer.finish(0);
+    return data;
+  }
+};
+
+class TlsInit : public TransparentProxy {
+ public:
+  using TransparentProxy::TransparentProxy;
+
+ private:
+  enum class State {
+    SendHello,
+    WaitHelloResponse,
+  } state_ = State::SendHello;
+
+  void send_hello() {
+    auto hello = TlsObfusaction::generate_header(username_, 0);
+    fd_.output_buffer().append(hello);
+    state_ = State::WaitHelloResponse;
+  }
+
+  Status wait_hello_response() {
+    //[
+    auto it = fd_.input_buffer().clone();
+    //S "\x16\x03\x03"
+    {
+      Slice first = "\x16\x03\x03";
+      std::string got_first(first.size(), 0);
+      if (it.size() < first.size()) {
+        return td::Status::OK();
+      }
+      it.advance(first.size(), got_first);
+      if (first != got_first) {
+        return Status::Error("First part of response to hello is invalid");
+      }
+    }
+
+    //[
+    {
+      if (it.size() < 2) {
+        return td::Status::OK();
+      }
+      uint8 tmp[2];
+      it.advance(2, MutableSlice(tmp, 2));
+      size_t skip_size = (tmp[0] << 8) + tmp[1];
+      if (it.size() < skip_size) {
+        return td::Status::OK();
+      }
+      it.advance(skip_size);
+    }
+
+    //S "\x14\x03\x03\x00\x01\x01\x17\x03\x03"
+    {
+      Slice first = "\x14\x03\x03\x00\x01\x01\x17\x03\x03";
+      std::string got_first(first.size(), 0);
+      if (it.size() < first.size()) {
+        return td::Status::OK();
+      }
+      it.advance(first.size(), got_first);
+      if (first != got_first) {
+        return Status::Error("Second part of response to hello is invalid");
+      }
+    }
+
+    //[
+    {
+      if (it.size() < 2) {
+        return td::Status::OK();
+      }
+      uint8 tmp[2];
+      it.advance(2, MutableSlice(tmp, 2));
+      size_t skip_size = (tmp[0] << 8) + tmp[1];
+      if (it.size() < skip_size) {
+        return td::Status::OK();
+      }
+      it.advance(skip_size);
+    }
+    fd_.input_buffer() = std::move(it);
+
+    stop();
+    return td::Status::OK();
+  }
+
+  Status loop_impl() override {
+    switch (state_) {
+      case State::SendHello:
+        send_hello();
+        break;
+      case State::WaitHelloResponse:
+        TRY_STATUS(wait_hello_response());
+        break;
+    }
+    return Status::OK();
+  }
+};
+
+TEST(Mtproto, TlsObfusaction) {
+  std::string s(10000, 'a');
+  Grease::init(s);
+  for (auto c : s) {
+    CHECK((c & 0xf) == 0xa);
+  }
+  for (size_t i = 1; i < s.size(); i += 2) {
+    CHECK(s[i] != s[i - 1]);
+  }
+  std::string domain = "www.google.com";
+  SET_VERBOSITY_LEVEL(VERBOSITY_NAME(ERROR));
+  ConcurrentScheduler sched;
+  int threads_n = 1;
+  sched.init(threads_n);
+  {
+    auto guard = sched.get_main_guard();
+    class Callback : public TransparentProxy::Callback {
+     public:
+      void set_result(Result<SocketFd> result) override {
+        result.ensure();
+        Scheduler::instance()->finish();
+      }
+      void on_connected() override {
+      }
+    };
+    IPAddress ip_address;
+    ip_address.init_host_port(domain, 443).ensure();
+    SocketFd fd = SocketFd::open(ip_address).move_as_ok();
+    create_actor<TlsInit>("TlsInit", std::move(fd), IPAddress(), domain, "", make_unique<Callback>(), ActorShared<>())
+        .release();
+  }
+
+  sched.start();
+  while (sched.run_main(10)) {
+    // empty
+  }
+  sched.finish();
+}