QSslPreSharedKeyAuthenticator Class

Detailed Description

The QSslPreSharedKeyAuthenticator class is used by an SSL socket to provide the required authentication data in a pre shared key (PSK) ciphersuite.

In a PSK handshake, the client must derive a key, which must match the key set on the server. The exact algorithm of deriving the key depends on the application; however, for this purpose, the server may send an identity hint to the client. This hint, combined with other information (for instance a passphrase), is then used by the client to construct the shared key.

The QSslPreSharedKeyAuthenticator provides means to client applications for completing the PSK handshake. The client application needs to connect a slot to the QSslSocket::preSharedKeyAuthenticationRequired() signal:

     connect(socket, &QSslSocket::preSharedKeyAuthenticationRequired,
             this, &AuthManager::handlePreSharedKeyAuthentication);

The signal carries a QSslPreSharedKeyAuthenticator object containing the identity hint the server sent to the client, and which must be filled with the corresponding client identity and the derived key:

     void AuthManager::handlePreSharedKeyAuthentication(QSslPreSharedKeyAuthenticator *authenticator)
     {
         authenticator->setIdentity("My Qt App");

         const QByteArray key = deriveKey(authenticator->identityHint(), passphrase);
         authenticator->setPreSharedKey(key);
     }