association.cpp Example File

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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;
 }