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();
 }

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