Help with Google Sign-In

franco.amato

I have to implement the Google Sign-In in my desktop application (I am using Qt 6.7.2).
I added a googleLoginButton button with the following slot:

void Login::on_googleLoginButton_clicked()
{
    m_googleOAuth2->grant();
}

In the ctor of my class I setup the Google Auth

Login::Login(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Login)
{
    ui->setupUi(this);
    setupGoogleAuth();
}

Here the google auth setup

void Login::setupGoogleAuth()
{
    m_googleOAuth2 = new QOAuth2AuthorizationCodeFlow(this);

    // Set client credentials
    m_googleOAuth2->setClientIdentifier("947359679464-jq8q0nscv9nioa3ig4lobrcsoc2tlpos.apps.googleusercontent.com");
    m_googleOAuth2->setClientIdentifierSharedKey("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");

    // Set authorization and token URLs
    m_googleOAuth2->setAuthorizationUrl(QUrl("https://accounts.google.com/o/oauth2/auth"));
    m_googleOAuth2->setAccessTokenUrl(QUrl("https://accounts.google.com/o/auth2/token"));
    
    // Set the scopes
    m_googleOAuth2->setScope("openid email profile");

    // Set the reply handler
    m_replyHandler = new QOAuthHttpServerReplyHandler(1337, this);
    m_googleOAuth2->setReplyHandler(m_replyHandler);

    // Connect signals and slots
    connect(m_googleOAuth2, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser,
            &QDesktopServices::openUrl);
    connect(m_googleOAuth2, &QOAuth2AuthorizationCodeFlow::granted, this, &Login::onGoogleLoginSuccess);
    connect(m_googleOAuth2, &QOAuth2AuthorizationCodeFlow::error, this,
            [this](const QString &error, const QString &errorDescription, const QUrl &uri) {
        onGoogleLoginError(error, errorDescription, uri);
    });
}

In case of success

void Login::onGoogleLoginSuccess()
{
    qDebug() << "AMATO: Google login successful";
    QString accessToken = m_googleOAuth2->token();

    // Save the access token securely
    saveAccessToken(accessToken);

    // Fetch user profile
    fetchGoogleUserProfile();

    QJsonObject requestData;
    requestData["access_token"] = accessToken;

    auto mgr = new QNetworkAccessManager(this);
    QNetworkReply *reply = BBHelper::HttpRequest(POST,
                                                 mgr,
                                                 "/api/google/login",
                                                 &requestData);

    connect(reply, &QNetworkReply::finished, this, [this, reply]() {
        handleBackendResponse(reply);
    });
}

In case of error:

void Login::onGoogleLoginError(const QString &error, const QString &errorDescription, const QUrl &uri)
{
    qWarning() << "AMATO: Google login error:" << error << errorDescription << uri.toString();
    QMessageBox::warning(this, "Login Error", "Failed to log in with Google " + errorDescription);
}

Unfortunately neither onGoogleLoginSuccess nor onGoogleLoginError is called and I cannot understand why. The cliend_id and client_secret are correct.
I would like to understand what I am doing wrong

Christian Ehrlicher

Don't see where you start the whole thing: https://doc.qt.io/qt-6/qoauth2authorizationcodeflow.html#grant

franco.amato

@Christian-Ehrlicher here:
void Login::on_googleLoginButton_clicked()
{
m_googleOAuth2->grant();
}

Christian Ehrlicher

And do you get there?

franco.amato

When I press the button, a web page opens so that i can choose the google account but after that nothing happens

SGaist

You should connect the error signal to see if something wrong is going on.

franco.amato

@SGaist The connection is already there. Now I could solve some problems but I noticed that I cannot get the token if I set the scope in this way:

m_oauth->setScope("email");
or
m_oauth->setScope("https://www.googleapis.com/auth/userinfo.email");

My only purpose is to get the user email. To get it working I have to set the scope in this way:

m_oauth->setScope("email https://www.googleapis.com/auth/drive.readonly");

I added to enable the drive api for that. For the first case I enabled People API and nothing. I cannot understand the problem

SGaist

Did you set the required scopes in your Google OAuth application ?