Qt 5.7 QNetworkProxy does not take into account cookies

Question

I am working on a Qt cloud client application that uses QWebEngineView and QNetworkAccessManager. The problem that I encountered is described bellow:

The application has a custom login form. Based on the users credentials, I perform a series of manual requests (a "post" and a "get") to obtain the relevant session cookies.

    ...
    //get session cookie
    QNetworkAccessManager accessManager;
    connect(&accessManager, &QNetworkAccessManager::proxyAuthenticationRequired, [=] (const QNetworkProxy &proxy, QAuthenticator *authenticator){
        //perform proxy auth in case a proxy is set
    });

    QNetworkReply * reply = Q_NULLPTR;

    QNetworkRequest request(QUrl(/*url*/));
    request.setRawHeader("Content-Type", "application/x-www-form-urlencoded");
    request.setRawHeader("Cache-Control", "no-cache");

    QByteArray data(/*data for auth*/);
    reply = accessManager.post(request,data); //ajax login

    QEventLoop waitReplyHandler;
    QObject::connect(reply, SIGNAL(finished()), &waitReplyHandler, SLOT(quit()));

    //wait for reply from url
    waitReplyHandler.exec();
    QVariant sessionCookie = reply->header(QNetworkRequest::SetCookieHeader); //this cookie is used to retrieve second "session cookie"
    ...

    //Different function - get user session cookie
    QNetworkRequest request(QUrl(/*url*/));

    request.setHeader(QNetworkRequest::CookieHeader, sessionCookie);
    QNetworkReply * reply = accessManager.get(request);

    QEventLoop waitReplyHandler;
    QObject::connect(reply, SIGNAL(finished()), &waitReplyHandler, SLOT(quit()));

    //wait for reply from url
    waitReplyHandler.exec();
    QString redirect = reply->header(QNetworkRequest::LocationHeader).toString();
    QVariant userSessionCookie = reply->header(QNetworkRequest::SetCookieHeader);

After this I set up a request interceptor for QWebEngineView:

    interceptor = new CWebEngineUrlRequestInterceptor(sessionCookie.value<QList<QNetworkCookie>>().first(),
                                                          userSessionCookie.value<QList<QNetworkCookie>>().first(),
                                                          this);
    m_tabWebview->webEngineView()->page()->profile()->setRequestInterceptor(interceptor);
    m_tabWebview->webEngineView()->load(redirectUrl); //Obtained from "redirect" string variable from second manual request 

The idea is to use these manual obtained cookies for every load call to web engine view:

    void CWebEngineUrlRequestInterceptor::interceptRequest(QWebEngineUrlRequestInfo &info)
    {
        QByteArray sessionCookie = QByteArray(m_sessionCookie.name() + "=" + m_sessionCookie.value());
        QByteArray userSessionCookie = QByteArray(m_userSessionCookie.name() + "=" + m_userSessionCookie.value());

        QByteArray requestCookies = sessionCookie + "; " + userSessionCookie;

        info.setHttpHeader(QByteArray("Cookie"), requestCookies);
    }

This work perfectly ok, after the load to redirectUrl, the web view will display the home page of the cloud with user already logged in. However, if I set a QNetworkProxy to application:

    QNetworkProxy proxy;
    proxy.setType(QNetworkProxy::HttpProxy);
    proxy.setHostName(proxyUrl);
    proxy.setPort(proxyPort.toInt());

    QNetworkProxy::setApplicationProxy(proxy);

The above sequence will display in the web view the login page of my target url. I believe the application level proxy setting should be agnostic to QWebEngineView. The manual requests are working, I am able to obtain the cookies, the interceptRequest is also called, but cookies are not retained after the proxy relay. I also tried setting manually the header to proxy itself:

    QByteArray requestCookies = m_cookies.first().name() + "=" + m_cookies.first().value() + "; " +
                            m_cookies.last().name() + "=" + m_cookies.last().value();

    QNetworkProxy proxy(QNetworkProxy::applicationProxy());
    proxy.setRawHeader(QByteArray("Cookie"), requestCookies);
    QNetworkProxy::setApplicationProxy(proxy);
    //...
    //check headers are set to proxy
    QByteArray cookieVar = QNetworkProxy::applicationProxy().rawHeader(QByteArray("Cookie"));
    if(cookieVar.isEmpty()){
        std::cout<<"empty cookies to proxy ";
    }
    else{
        std::cout<<cookieVar.toStdString()<<std::endl;
    }

The logs are ok, I can see that the cookies are attached to proxy.

This custom login mechanism is implemented to handle automatic login in case there is no internet connection for a longer period of time than the expiration time of the session cookie. How can I set the application level proxy to use the manual obtained session cookies?

Thank you in advance.

Answer 1

It seems to be a bug in web engine framework related to proxy authentication mechanism. However I found a workaround: When QWebEnginePage::proxyAuthenticationRequired is called, after the data to authenticator object is set, I just call load again to requestUrl parameter.

connect(app->webview()->page(), &QWebEnginePage::proxyAuthenticationRequired, [=] (const QUrl &requestUrl, QAuthenticator *authenticator, const QString &proxyHost){
    proxyAuthSequence(authenticator, proxyHost);
    app->webview()->load(requestUrl);
});

The ideea is to treat the initial load as a dummy load only to set the authentication data and then load again the url. Subsequent load calls will not trigger this signal anymore. So, basically the problem is with the authentication mechanism.

The bug was also submitted to Qt: https://bugreports.qt.io/browse/QTBUG-58121