google quic tls 握手原理（三）

2023-11-03  本文已影响0人  JeffreyLau

一、前言

二、服务端握手报文分析

三、客户端处理服务端的Initial包

bool TlsHandshaker::ProcessInput(absl::string_view input,
                                 EncryptionLevel level) {
  if (parser_error_ != QUIC_NO_ERROR) {
    return false;
  }
  // TODO(nharper): Call SSL_quic_read_level(ssl()) and check whether the
  // encryption level BoringSSL expects matches the encryption level that we
  // just received input at. If they mismatch, should ProcessInput return true
  // or false? If data is for a future encryption level, it should be queued for
  // later?
  if (SSL_provide_quic_data(ssl(), TlsConnection::BoringEncryptionLevel(level),
                            reinterpret_cast<const uint8_t*>(input.data()),
                            input.size()) != 1) {
    // SSL_provide_quic_data can fail for 3 reasons:
    // - API misuse (calling it before SSL_set_custom_quic_method, which we
    //   call in the TlsHandshaker c'tor)
    // - Memory exhaustion when appending data to its buffer
    // - Data provided at the wrong encryption level
    //
    // Of these, the only sensible error to handle is data provided at the wrong
    // encryption level.
    //
    // Note: the error provided below has a good-sounding enum value, although
    // it doesn't match the description as it's a QUIC Crypto specific error.
    parser_error_ = QUIC_INVALID_CRYPTO_MESSAGE_TYPE;
    parser_error_detail_ = "TLS stack failed to receive data";
    return false;
  }
  AdvanceHandshake();
  return true;
}

四、客户端处理服务端的Handshake证书以及证书验证

enum ssl_verify_result_t TlsHandshaker::VerifyCert(uint8_t* out_alert) {
  if (verify_result_ != ssl_verify_retry ||
      expected_ssl_error() == SSL_ERROR_WANT_CERTIFICATE_VERIFY) {
    enum ssl_verify_result_t result = verify_result_;
    verify_result_ = ssl_verify_retry;
    *out_alert = cert_verify_tls_alert_;
    return result;
  }
  const STACK_OF(CRYPTO_BUFFER)* cert_chain = SSL_get0_peer_certificates(ssl());
  if (cert_chain == nullptr) {
    *out_alert = SSL_AD_INTERNAL_ERROR;
    return ssl_verify_invalid;
  }
  // TODO(nharper): Pass the CRYPTO_BUFFERs into the QUIC stack to avoid copies.
  std::vector<std::string> certs;
  for (CRYPTO_BUFFER* cert : cert_chain) {
    certs.push_back(
        std::string(reinterpret_cast<const char*>(CRYPTO_BUFFER_data(cert)),
                    CRYPTO_BUFFER_len(cert)));
  }

  ProofVerifierCallbackImpl* proof_verify_callback =
      new ProofVerifierCallbackImpl(this);

  cert_verify_tls_alert_ = *out_alert;
  QuicAsyncStatus verify_result = VerifyCertChain(
      certs, &cert_verify_error_details_, &verify_details_,
      &cert_verify_tls_alert_,
      std::unique_ptr<ProofVerifierCallback>(proof_verify_callback));
  switch (verify_result) {
    case QUIC_SUCCESS:
      if (verify_details_) {
        OnProofVerifyDetailsAvailable(*verify_details_);
      }
      return ssl_verify_ok;
    case QUIC_PENDING:
      proof_verify_callback_ = proof_verify_callback;
      set_expected_ssl_error(SSL_ERROR_WANT_CERTIFICATE_VERIFY);
      return ssl_verify_retry;
    case QUIC_FAILURE:
    default:
      *out_alert = cert_verify_tls_alert_;
      QUIC_LOG(INFO) << "Cert chain verification failed: "
                     << cert_verify_error_details_;
      return ssl_verify_invalid;
  }
}

QuicAsyncStatus TlsClientHandshaker::VerifyCertChain(
    const std::vector<std::string>& certs, std::string* error_details,
    std::unique_ptr<ProofVerifyDetails>* details, uint8_t* out_alert,
    std::unique_ptr<ProofVerifierCallback> callback) {
  const uint8_t* ocsp_response_raw;
  size_t ocsp_response_len;
  SSL_get0_ocsp_response(ssl(), &ocsp_response_raw, &ocsp_response_len);
  std::string ocsp_response(reinterpret_cast<const char*>(ocsp_response_raw),
                            ocsp_response_len);
  const uint8_t* sct_list_raw;
  size_t sct_list_len;
  SSL_get0_signed_cert_timestamp_list(ssl(), &sct_list_raw, &sct_list_len);
  std::string sct_list(reinterpret_cast<const char*>(sct_list_raw),
                       sct_list_len);

  return proof_verifier_->VerifyCertChain(
      server_id_.host(), server_id_.port(), certs, ocsp_response, sct_list,
      verify_context_.get(), error_details, details, out_alert,
      std::move(callback));
}

class QUIC_EXPORT_PRIVATE TlsClientHandshaker
    : public TlsHandshaker,
      public QuicCryptoClientStream::HandshakerInterface,
      public TlsClientConnection::Delegate {
  ....
 private: 
  ....
  // Objects used for verifying the server's certificate chain.
  // |proof_verifier_| is owned by the caller of TlsHandshaker's constructor.
  ProofVerifier* proof_verifier_;
};

五、客户端完成握手后处理

void TlsHandshaker::AdvanceHandshake() {
  ...
  int rv = SSL_do_handshake(ssl());
  ....
  if (rv == 1) {
    FinishHandshake();
    return;
  }
 ....
}

void TlsClientHandshaker::FinishHandshake() {
  //1) 填充握手参数
  FillNegotiatedParams();
  //2) 处理传输参数
  std::string error_details;
  if (!ProcessTransportParameters(&error_details)) {
    CloseConnection(QUIC_HANDSHAKE_FAILED, error_details);
    return;
  }
  //3) 从加密扩展中选择应用层协议(第二节中的图1）
  const uint8_t* alpn_data = nullptr;
  unsigned alpn_length = 0;
  SSL_get0_alpn_selected(ssl(), &alpn_data, &alpn_length);

  if (alpn_length == 0) {
    CloseConnection(QUIC_HANDSHAKE_FAILED, "Server did not select ALPN");
    return;
  }
  //4) 和客户端已经选择应用协议进行比较
  std::string received_alpn_string(reinterpret_cast<const char*>(alpn_data),
                                   alpn_length);
  std::vector<std::string> offered_alpns = session()->GetAlpnsToOffer();
  if (std::find(offered_alpns.begin(), offered_alpns.end(),
                received_alpn_string) == offered_alpns.end()) {
    CloseConnection(QUIC_HANDSHAKE_FAILED, "Client received mismatched ALPN");
    return;
  }
  //5) 通知更上层应用层协议已选择
  session()->OnAlpnSelected(received_alpn_string);

  // Parse ALPS extension.
  const uint8_t* alps_data;
  size_t alps_length;
  SSL_get0_peer_application_settings(ssl(), &alps_data, &alps_length);
  if (alps_length > 0) {
    // 6) 通知更上层应用设置参数
    auto error = session()->OnAlpsData(alps_data, alps_length);
    if (error) {
      // Calling CloseConnection() is safe even in case OnAlpsData() has
      // already closed the connection.
      CloseConnection(
          QUIC_HANDSHAKE_FAILED,
          absl::StrCat("Error processing ALPS data: ", error.value()));
      return;
    }
  }

  state_ = HANDSHAKE_COMPLETE;
  // 7）通知QuicSession握手已完成
  handshaker_delegate()->OnTlsHandshakeComplete();
}

六、客户端处理服务端的Handshake New Session Ticket

// static
bssl::UniquePtr<SSL_CTX> TlsClientConnection::CreateSslCtx(
    bool enable_early_data) {
  bssl::UniquePtr<SSL_CTX> ssl_ctx = TlsConnection::CreateSslCtx();
  ....
  // Configure session caching.
  SSL_CTX_set_session_cache_mode(
      ssl_ctx.get(), SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_NO_INTERNAL);
  SSL_CTX_sess_set_new_cb(ssl_ctx.get(), NewSessionCallback);
  ....
  return ssl_ctx;
}

void TlsClientHandshaker::InsertSession(bssl::UniquePtr<SSL_SESSION> session) {
  //1) 第5节已经解析并处理
  if (!received_transport_params_) {
    QUIC_BUG(quic_bug_10576_8) << "Transport parameters isn't received";
    return;
  }
  // 2) 初始化的时候配置是否支持缓存
  if (session_cache_ == nullptr) {
    QUIC_DVLOG(1) << "No session cache, not inserting a session";
    return;
  }
  // 3) has_application_state_是个bool值,在构造TlsClientHandshaker的时候会传入,表示是否有应用状态
  // received_application_state_当收到服务端的SettingFrame后会被初始化,由于本文分析的是RAW DATA流,所以抓包文件中未能体现
  if (has_application_state_ && !received_application_state_) {
    // Application state is not received yet. cache the sessions.
    if (cached_tls_sessions_[0] != nullptr) {
      cached_tls_sessions_[1] = std::move(cached_tls_sessions_[0]);
    }
    cached_tls_sessions_[0] = std::move(session);
    return;
  }
  // 4) 将SSL_SESSION插入到session_cache_集合进行缓存
  session_cache_->Insert(server_id_, std::move(session),
                         *received_transport_params_,
                         received_application_state_.get());
}

七、客户端处理HANDSHAKE_DONE和NEW_TOKEN、NEW_CONNECTION_ID

HANDSHAKE_DONE处理

void QuicSession::OnHandshakeDoneReceived() {
  GetMutableCryptoStream()->OnHandshakeDoneReceived();
}

void QuicCryptoClientStream::OnHandshakeDoneReceived() {
  handshaker_->OnHandshakeDoneReceived();
}

void TlsClientHandshaker::OnHandshakeDoneReceived() {
  if (!one_rtt_keys_available()) {
    CloseConnection(QUIC_HANDSHAKE_FAILED,
                    "Unexpected handshake done received");
    return;
  }
  OnHandshakeConfirmed();
}

void TlsClientHandshaker::OnHandshakeConfirmed() {
  QUICHE_DCHECK(one_rtt_keys_available());
  if (state_ >= HANDSHAKE_CONFIRMED) {
    return;
  }
  state_ = HANDSHAKE_CONFIRMED;
  handshaker_delegate()->DiscardOldEncryptionKey(ENCRYPTION_HANDSHAKE);
  handshaker_delegate()->DiscardOldDecryptionKey(ENCRYPTION_HANDSHAKE);
}

NEW_TOKEN处理

void QuicSession::OnNewTokenReceived(absl::string_view token) {
  GetMutableCryptoStream()->OnNewTokenReceived(token);
}

void QuicCryptoClientStream::OnNewTokenReceived(absl::string_view token) {
  handshaker_->OnNewTokenReceived(token);
}

void TlsClientHandshaker::OnNewTokenReceived(absl::string_view token) {
  if (token.empty()) {
    return;
  }
  if (session_cache_ != nullptr) {
    session_cache_->OnNewTokenReceived(server_id_, token);
  }
}

NEW_CONNECTION_ID处理

总结

参考文献

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