QAbstractOAuth2 missing access_type and approval_prompt?

TenG

The (horribly convoluted) code I (a novice) have inherited uses the QAbstractOAuth2 class to implement OAuth2 access to Google drive.

The app only succeeds to gain a access token for Google Drive if the app's access is revoked from the Google Drive control panel. But subsequent requests fail with the obscure 'bad request' error.

I set up a test using curl and found that adding the parameters access_type=offline&approval_prompt=force to the URL results in the access working.

So now I want to try and add this in my Qt code.

_oAuth2 = new QOAuth2AuthorizationCodeFlow( this);
    _oAuth2->setScope( "https://www.googleapis.com/auth/drive");
    _oAuth2->setAuthorizationUrl(  "https://accounts.GOOGLE.com/o/oauth2/auth" );
    _oAuth2->setAccessTokenUrl( "https://oauth2.googleapis.com/token");
    _oAuth2->setClientIdentifier( "the_client_id");
    _oAuth2->setClientIdentifierSharedKey( "the secret_key");

    _firstAuth = true;
    _oAuth2->grant();

The resulting URL is:

https://accounts.google.com/o/oauth2/auth?client_id=the_client_id&redirect_uri=http://127.0.0.1:8080/cb&response_type=code&scope=https://www.googleapis.com/auth/drive&state=2hRrr5q1

There I can add the access_type and approval_prompt to the URL but shouldn't these be included in the QAbstractOAuth2 class ?

TenG

I found the answer. From this article :

How To Authenticate with Google SSO in Qt (C++)

I found that the reply must be assumed to return encoded code, so adding call to setModifyParametersFunction as below fixed the issue:

_oAuth2 = new QOAuth2AuthorizationCodeFlow( this);
    _oAuth2->setScope( "https://www.googleapis.com/auth/drive");
    _oAuth2->setAuthorizationUrl(  "https://accounts.GOOGLE.com/o/oauth2/auth" );
    _oAuth2->setAccessTokenUrl( "https://oauth2.googleapis.com/token");
    _oAuth2->setClientIdentifier( "the_client_id");
    _oAuth2->setClientIdentifierSharedKey( "the secret_key");

// Added this:
    _oAuth2->setModifyParametersFunction([](QAbstractOAuth::Stage stage, QVariantMap* parameters) {
        // Percent-decode the "code" parameter so Google can match it
        if (stage == QAbstractOAuth::Stage::RequestingAccessToken) {
            QByteArray code = parameters->value("code").toByteArray();
            (*parameters)["code"] = QUrl::fromPercentEncoding(code);
        }
    });
// End Add

    _firstAuth = true;
    _oAuth2->grant();```

ZOMGDEV

@TenG for QT 6.1.0 this lambda setModifyParametersFunction([](QAbstractOAuth::Stage stage, QVariantMap* parameters) isnt work.
I got error :
no viable conversion from lambda to 'const QAbstractOAuth::ModifyParametersFunction' (aka 'const function<void (QAbstractOAuth::Stage, QMultiMap<QString, QVariant> *)>')

Michaelikus

same thing

franco.amato

Hi how did you fix it? I have the same problem

SGaist

@franco-amato hi,

Which version of Qt are you using ?

The issue of percent encoded value handling has been fixed since then.

franco.amato

@SGaist I am using Qt 6.7.2, I tried everything and nothing

m_googleOAuth2->setModifyParametersFunction(
    [this](QAbstractOAuth::Stage stage, QVariantMap* parameters) {
        modifyOAuthParameters(stage, parameters);
    });

void Login::modifyOAuthParameters(QAbstractOAuth::Stage stage, QVariantMap *parameters)
{
if (stage == QAbstractOAuth::Stage::RequestingAuthorization)
{
parameters->insert("redirect_uri", "http://localhost:8080/");
}
}