How to create a login page using Qt oauth?

Question

I\'ve been looking around on the web on how to create an authentication page when my Qt desktop app opens. I already built the app; that is pretty small and only composed of

Answer 1

So, the article from Qt blog is almost complete. You just need to connect granted signal and make needed requests after that.

Note about /cb path in redirect_uri in Qt blog is not valid anymore(article came about a year ago).

NOTE: The path “/cb” is mandatory in the current QOAuthHttpServerReplyHandler implementation.

So if you see access error from google after running your code, just copy-paste redirect_uri from there into GoogleConsole Authorized redirect URIs of your configured client. http://localhost:8080/ <- don't forget slash at the end

P.S.: Don't forget to dowload json file with credentials from console again.

Also if you want to call any Google APIs after authorization, you need to enable them in GoogleConsole for your project. To test the code just enable Google+ API

That's it. Here is the complete and working code. (Tested on Linux and Qt 5.10, Don't have Windows at the moment, can't test it there)

googlegateway.h

#ifndef GOOGLEGATEWAY_H
#define GOOGLEGATEWAY_H

#include <QObject>
#include <QOAuth2AuthorizationCodeFlow>
#include <QNetworkReply>

class GoogleGateway : public QObject
{
    Q_OBJECT
public:
    explicit GoogleGateway(QObject *parent = nullptr);

private:
    QOAuth2AuthorizationCodeFlow * google;
};

#endif // GOOGLEGATEWAY_H

googlegateway.cpp

#include "googlegateway.h"
#include <QObject>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QString>
#include <QFile>
#include <QDir>
#include <QUrl>
#include <QOAuthHttpServerReplyHandler>
#include <QDesktopServices>


GoogleGateway::GoogleGateway(QObject *parent) : QObject(parent)
{
    this->google = new QOAuth2AuthorizationCodeFlow(this);
    this->google->setScope("email");

    connect(this->google, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser, &QDesktopServices::openUrl);

    QByteArray val;
    QFile file;
    file.setFileName(QDir::toNativeSeparators("/full/path/client_secret_XXXXXXX.apps.googleusercontent.com.json"));
    if(file.open(QIODevice::ReadOnly | QIODevice::Text))
    {
        val = file.readAll();
        file.close();
    }


    QJsonDocument document = QJsonDocument::fromJson(val);
    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);
    this->google->setReplyHandler(replyHandler);
    this->google->grant();

    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();
        });
    });
}

Answer 2

Please remember to set Redirect URI in google console to http://127.0.0.1:port_no/ instead of http://localhost:port_no/ for all localhost.

Remember to put the trailing '/' in the Redirect URI.

Rest of the code

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

        connect(this->google, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser, &QDesktopServices::openUrl);

        this->google->setAuthorizationUrl(QUrl("https://accounts.google.com/o/oauth2/auth"));
        this->google->setClientIdentifier(MY_CLIENT_ID);
        this->google->setAccessTokenUrl(QUrl("https://oauth2.googleapis.com/token"));
        this->google->setClientIdentifierSharedKey(MYTOKEN);

// In my case, I have hardcoded 8080 to test
        auto replyHandler = new QOAuthHttpServerReplyHandler(8080, this);
        this->google->setReplyHandler(replyHandler);
        this->google->grant();

        qDebug() << "Access";

        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();
            });
        });