server.cpp Example File

secureudpserver/server.cpp

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  #include "server.h"

  #include <algorithm>

  namespace {

  QString peer_info(const QHostAddress &address, quint16 port)
  {
      const static QString info = QStringLiteral("(%1:%2)");
      return info.arg(address.toString()).arg(port);
  }

  QString connection_info(QSharedPointer<QDtls> connection)
  {
      QString info(DtlsServer::tr("Session cipher: "));
      info += connection->sessionCipher().name();

      info += DtlsServer::tr("; session protocol: ");
      switch (connection->sessionProtocol()) {
      case QSsl::DtlsV1_0:
          info += DtlsServer::tr("DTLS 1.0.");
          break;
      case QSsl::DtlsV1_2:
          info += DtlsServer::tr("DTLS 1.2.");
          break;
      case QSsl::DtlsV1_2OrLater:
          info += DtlsServer::tr("DTLS 1.2 or later.");
          break;
      default:
          info += DtlsServer::tr("Unknown protocol.");
      }

      return info;
  }

  } // unnamed namespace

  DtlsServer::DtlsServer()
  {
      connect(&serverSocket, &QAbstractSocket::readyRead, this, &DtlsServer::readyRead);

      serverConfiguration = QSslConfiguration::defaultDtlsConfiguration();
      serverConfiguration.setPreSharedKeyIdentityHint("Qt DTLS example server");
      serverConfiguration.setPeerVerifyMode(QSslSocket::VerifyNone);
  }

  DtlsServer::~DtlsServer()
  {
      shutdown();
  }

  bool DtlsServer::listen(const QHostAddress &address, quint16 port)
  {
      if (address != serverSocket.localAddress() || port != serverSocket.localPort()) {
          shutdown();
          listening = serverSocket.bind(address, port);
          if (!listening)
              emit errorMessage(serverSocket.errorString());
      } else {
          listening = true;
      }

      return listening;
  }

  bool DtlsServer::isListening() const
  {
      return listening;
  }

  void DtlsServer::close()
  {
      listening = false;
  }

  void DtlsServer::readyRead()
  {
      const qint64 bytesToRead = serverSocket.pendingDatagramSize();
      if (bytesToRead <= 0) {
          emit warningMessage(tr("A spurious read notification"));
          return;
      }

      QByteArray dgram(bytesToRead, Qt::Uninitialized);
      QHostAddress peerAddress;
      quint16 peerPort = 0;
      const qint64 bytesRead = serverSocket.readDatagram(dgram.data(), dgram.size(),
                                                         &peerAddress, &peerPort);
      if (bytesRead <= 0) {
          emit warningMessage(tr("Failed to read a datagram: ") + serverSocket.errorString());
          return;
      }

      dgram.resize(bytesRead);
      if (peerAddress.isNull() || !peerPort) {
          emit warningMessage(tr("Failed to extract peer info (address, port)"));
          return;
      }

      const auto client = std::find_if(knownClients.begin(), knownClients.end(),
                                       [&](const DtlsConnection &connection){
          return connection->peerAddress() == peerAddress
                 && connection->peerPort() == peerPort;
      });

      if (client == knownClients.end())
          return handleNewConnection(peerAddress, peerPort, dgram);

      if ((*client)->isConnectionEncrypted()) {
          decryptDatagram(*client, dgram);
          if ((*client)->dtlsError() == QDtlsError::RemoteClosedConnectionError)
              knownClients.erase(client);
          return;
      }

      doHandshake(*client, dgram);
  }

  void DtlsServer::pskRequired(QSslPreSharedKeyAuthenticator *auth)
  {
      Q_ASSERT(auth);

      emit infoMessage(tr("PSK callback, received a client's identity: '%1'")
                       .arg(QString::fromLatin1(auth->identity())));
      auth->setPreSharedKey(QByteArrayLiteral("\x1a\x2b\x3c\x4d\x5e\x6f"));
  }

  void DtlsServer::handleNewConnection(const QHostAddress &peerAddress,
                                       quint16 peerPort, const QByteArray &clientHello)
  {
      if (!listening)
          return;

      const QString peerInfo = peer_info(peerAddress, peerPort);
      if (cookieSender.verifyClient(&serverSocket, clientHello, peerAddress, peerPort)) {
          emit infoMessage(peerInfo + tr(": verified, starting a handshake"));
          DtlsConnection newConnection(new QDtls(QSslSocket::SslServerMode));
          newConnection->setDtlsConfiguration(serverConfiguration);
          newConnection->setPeer(peerAddress, peerPort);
          newConnection->connect(newConnection.data(), &QDtls::pskRequired,
                                 this, &DtlsServer::pskRequired);
          knownClients.push_back(newConnection);
          doHandshake(newConnection, clientHello);
      } else if (cookieSender.dtlsError() != QDtlsError::NoError) {
          emit errorMessage(tr("DTLS error: ") + cookieSender.dtlsErrorString());
      } else {
          emit infoMessage(peerInfo + tr(": not verified yet"));
      }
  }

  void DtlsServer::doHandshake(DtlsConnection newConnection, const QByteArray &clientHello)
  {
      const bool result = newConnection->doHandshake(&serverSocket, clientHello);
      if (!result) {
          emit errorMessage(newConnection->dtlsErrorString());
          return;
      }

      const QString peerInfo = peer_info(newConnection->peerAddress(),
                                         newConnection->peerPort());
      switch (newConnection->handshakeState()) {
      case QDtls::HandshakeInProgress:
          emit infoMessage(peerInfo + tr(": handshake is in progress ..."));
          break;
      case QDtls::HandshakeComplete:
          emit infoMessage(tr("Connection with %1 encrypted. %2")
                           .arg(peerInfo, connection_info(newConnection)));
          break;
      default:
          Q_UNREACHABLE();
      }
  }

  void DtlsServer::decryptDatagram(DtlsConnection connection, const QByteArray &clientMessage)
  {
      Q_ASSERT(connection->isConnectionEncrypted());

      const QString peerInfo = peer_info(connection->peerAddress(), connection->peerPort());
      const QByteArray dgram = connection->decryptDatagram(&serverSocket, clientMessage);
      if (dgram.size()) {
          emit datagramReceived(peerInfo, clientMessage, dgram);
          connection->writeDatagramEncrypted(&serverSocket, tr("to %1: ACK").arg(peerInfo).toLatin1());
      } else if (connection->dtlsError() == QDtlsError::NoError) {
          emit warningMessage(peerInfo + ": " + tr("0 byte dgram, could be a re-connect attempt?"));
      } else {
          emit errorMessage(peerInfo + ": " + connection->dtlsErrorString());
      }
  }

  void DtlsServer::shutdown()
  {
      for (DtlsConnection &connection : knownClients)
          connection->shutdown(&serverSocket);

      knownClients.clear();
      serverSocket.close();
  }