association.cpp Example File

secureudpclient/association.cpp

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  #include "association.h"

  DtlsAssociation::DtlsAssociation(const QHostAddress &address, quint16 port,
                                   const QString &connectionName)
      : name(connectionName),
        crypto(QSslSocket::SslClientMode)
  {
      auto configuration = QSslConfiguration::defaultDtlsConfiguration();
      configuration.setPeerVerifyMode(QSslSocket::VerifyNone);
      crypto.setPeer(address, port);
      crypto.setDtlsConfiguration(configuration);

      connect(&crypto, &QDtls::handshakeTimeout, this, &DtlsAssociation::handshakeTimeout);
      connect(&crypto, &QDtls::pskRequired, this, &DtlsAssociation::pskRequired);
      socket.connectToHost(address.toString(), port);
      connect(&socket, &QUdpSocket::readyRead, this, &DtlsAssociation::readyRead);
      pingTimer.setInterval(5000);
      connect(&pingTimer, &QTimer::timeout, this, &DtlsAssociation::pingTimeout);
  }

  DtlsAssociation::~DtlsAssociation()
  {
      if (crypto.isConnectionEncrypted())
          crypto.shutdown(&socket);
  }

  void DtlsAssociation::startHandshake()
  {
      if (socket.state() != QAbstractSocket::ConnectedState) {
          emit infoMessage(tr("%1: connecting UDP socket first ...").arg(name));
          connect(&socket, &QAbstractSocket::connected, this, &DtlsAssociation::udpSocketConnected);
          return;
      }

      if (!crypto.doHandshake(&socket))
          emit errorMessage(tr("%1: failed to start a handshake - %2").arg(name, crypto.dtlsErrorString()));
      else
          emit infoMessage(tr("%1: starting a handshake").arg(name));
  }

  void DtlsAssociation::udpSocketConnected()
  {
      emit infoMessage(tr("%1: UDP socket is now in ConnectedState, continue with handshake ...").arg(name));
      startHandshake();
  }

  void DtlsAssociation::readyRead()
  {
      QByteArray dgram(socket.pendingDatagramSize(), Qt::Uninitialized);
      const qint64 bytesRead = socket.readDatagram(dgram.data(), dgram.size());
      if (bytesRead <= 0) {
          emit warningMessage(tr("%1: spurious read notification?").arg(name));
          return;
      }

      dgram.resize(bytesRead);
      if (crypto.isConnectionEncrypted()) {
          const QByteArray plainText = crypto.decryptDatagram(&socket, dgram);
          if (plainText.size()) {
              emit serverResponse(name, dgram, plainText);
              return;
          }

          if (crypto.dtlsError() == QDtlsError::RemoteClosedConnectionError) {
              emit errorMessage(tr("%1: shutdown alert received").arg(name));
              socket.close();
              pingTimer.stop();
              return;
          }

          emit warningMessage(tr("%1: zero-length datagram received?").arg(name));
      } else {
          if (!crypto.doHandshake(&socket, dgram)) {
              emit errorMessage(tr("%1: handshake error - %2").arg(name, crypto.dtlsErrorString()));
              return;
          }

          if (crypto.isConnectionEncrypted()) {
              emit infoMessage(tr("%1: encrypted connection established!").arg(name));
              pingTimer.start();
              pingTimeout();
          } else {
              emit infoMessage(tr("%1: continuing with handshake ...").arg(name));
          }
      }
  }

  void DtlsAssociation::handshakeTimeout()
  {
      emit warningMessage(tr("%1: handshake timeout, trying to re-transmit").arg(name));
      if (!crypto.handleTimeout(&socket))
          emit errorMessage(tr("%1: failed to re-transmit - %2").arg(name, crypto.dtlsErrorString()));
  }

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

      emit infoMessage(tr("%1: providing pre-shared key ...").arg(name));
      auth->setIdentity(name.toLatin1());
      auth->setPreSharedKey(QByteArrayLiteral("\x1a\x2b\x3c\x4d\x5e\x6f"));
  }

  void DtlsAssociation::pingTimeout()
  {
      static const QString message = QStringLiteral("I am %1, please, accept our ping %2");
      const qint64 written = crypto.writeDatagramEncrypted(&socket, message.arg(name).arg(ping).toLatin1());
      if (written <= 0) {
          emit errorMessage(tr("%1: failed to send a ping - %2").arg(name, crypto.dtlsErrorString()));
          pingTimer.stop();
          return;
      }

      ++ping;
  }