Qt 5.14.2 Oauth2 Google login

kyura4k

Hi all,

For a personal project, I need to interface with Google APIs (given most work I do is google cloud based, also for personal projects. I normally work with Go, but have a big cpp interest).

To facilitate logging in, such that I can actually use these Google APIs, Qt provides QtNetworkAuth which should help setting things up.

The problem:
Following the answer in this article, I am supposedly able to login. I have my credentials set up, I have tried both desktop and webapp oauth2 credentials, both end in the same result. Note that I did also look at this supposedly outdated article.

When I start the application (I just run the auth code on startup of fresh Qt Widget application in mainwindow.cpp constructor for testing) the browser pops up and I can select my google account. I click it, and at some point the callback is supposed to happen.

I then get redirected to: http://127.0.0.1:8080/?state=NZrN2q96&code=4%2F0AG-yIbm-BjJSNDgVNhEf14zudhtH9a2tKO2SVgeCG8bnIiWExjmZ12Jjwj7YOTqEW8HisrG7VL_EelbvCIvE1o&scope=email+https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fuserinfo.email+openid&authuser=0&prompt=consent#

which basically results in This site can’t be reached127.0.0.1 refused to connect.
Now what I assumed is that the QOAuthHttpServerReplyHandler will fetch the response when a callback is made, but that seems to fail (?)

So am I correct in understanding that QOAuthHttpServerReplyHandler is supposed to handle the callback?
The configured url (in gcp secrets) is http://127.0.0.1:8080/

I just don't really understand what I need to do on Qt side to handle the part where I select which google account I want to authorize in the browser opened by the Qt application.

Here is my code (its basically a copy paste of aformentioned stackoverflow). It never ends up in the granted or status changed lambdas.

    this->google = new QOAuth2AuthorizationCodeFlow(this);
    this->google->setScope("email");

    connect(this->google, &QOAuth2AuthorizationCodeFlow::statusChanged, [=](
            QAbstractOAuth::Status status) {
        qDebug() << "status changed";
    });
    connect(this->google, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser, &QDesktopServices::openUrl);
    connect(this->google, &QOAuth2AuthorizationCodeFlow::granted, [=](){
        qDebug() << __FUNCTION__ << __LINE__ << "Access Granted!";
        auto reply = this->google->get(QUrl("https://www.googleapis.com/plus/v1/people/me"));
        connect(reply, &QNetworkReply::finished, [reply](){
            qDebug() << "REQUEST FINISHED. Error? " << (reply->error() != QNetworkReply::NoError);
            qDebug() << reply->readAll();
        });
    });

    QString saJson = readJsonFromInternalResource();
    QJsonDocument document = QJsonDocument::fromJson(saJson.toUtf8());
    QJsonObject object = document.object();
    const auto settingsObject = object["web"].toObject();
    const QUrl authUri(settingsObject["auth_uri"].toString());
    const auto clientId = settingsObject["client_id"].toString();
    const QUrl tokenUri(settingsObject["token_uri"].toString());
    const auto clientSecret(settingsObject["client_secret"].toString());

    const auto redirectUris = settingsObject["redirect_uris"].toArray();
    const QUrl redirectUri(redirectUris[0].toString());
    const auto port = static_cast<quint16>(redirectUri.port());

    this->google->setAuthorizationUrl(authUri);
    this->google->setClientIdentifier(clientId);
    this->google->setAccessTokenUrl(tokenUri);
    this->google->setClientIdentifierSharedKey(clientSecret);


    auto replyHandler = new QOAuthHttpServerReplyHandler(port, this);
    qDebug() << replyHandler->isListening();
    this->google->setReplyHandler(replyHandler);
    this->google->grant();

Tried doing this on both MacOS and Windows 10 using Qt 5.14.2 installed with the online installer.

kyura4k

An update:

I actually managed to fix this. It was a really dumb mistake and it had to do with the object being out of scope before the we got a reply from the callback.

So In my MainWindows constructor I did:

GoogleGateway gateway(this);

constructor goes out of scope, gateway gets deleted from the stack. Move this to the heap and all is fine and dandy.

So this was just a noob memory management problem and not an oauth2 problem.

ihaveajob

In case someone is still running into this or similar errors, we have prepared an extensive document on how to authenticate a Qt app with Google SSO. The most common problem is to use the Google-provided redirect URI instead of just using http://127.0.0.1:1234/ which is more dependable.