Why am I getting bad request from google? - c++

Question

My objective
To exchange refresh token for access token from google using OAuth 2.
My code
bool Google_Account::Refresh_Access_Token_Using_Refresh_Token()
{
// Prepare Url
QUrl url(tr("https://www.googleapis.com/oauth2/v4/token"));
// Create request
QNetworkRequest request(url);
request.setRawHeader("Host:","www.googleapis.com");
request.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");
// Create request body ClientID, ClientSecret, RefreshTokenString are class data members
QString RequestBody = tr("client_secret=%1&").arg(ClientSecret) +
tr("grant_type=refresh_token&")+
tr("refresh_token=%1&").arg(RefreshTokenString)+
tr("client_id=%1").arg(ClientID);
QByteArray array = RequestBody.toUtf8();
// Get reply
QNetworkReply *reply = mQNAM.post(request, array); // mQNAM is QNetworkAccessManager
// Set timeout to reply while waiting for reply finished
bool stop = false;
QTimer timer;
timer.setSingleShot(true);
QObject::connect(&timer, &QTimer::timeout, [&](){
qDebug()<<"Time out";
stop = true;
});
timer.start(5000);
// Wait till the response is completed
while(!reply->isFinished()){
QCoreApplication::processEvents();
if(stop){
qDebug()<<"Going to abort";
reply->abort();
}
}
// Check for reply
if(reply->isFinished()){
if(reply->error() != QNetworkReply::NoError){
qDebug()<<reply->readAll();
emit setMessage("Error: "+reply->errorString());
delete reply;
return false;
}
else{
QByteArray array = reply->readAll();
QJsonDocument document = QJsonDocument::fromJson(array);
QJsonObject obj = document.object();
access_token = obj.value("access_token").toString(); //access_token is class data variable
delete reply;
return true;
}
}
else{
delete reply;
return false;
}
}
The problem is that if I run this code in my windows 7 pc(Qt 5.11.1) everything is fine I get the access token but if i run in my raspberry pi(raspbian Qt 5.7) I get Error 400, Bad request from google. I tried using the access_token got from my windows pc and made other request such as to get the file list from google drive, they are working fine in raspberry, but only this I am having problem. What am I doing wrong?
P.S the code is refactored to the specific details only, in reality I am getting the client id and other keys from QSettings

Answer 1

This smells like you're getting a 400 code when Qt is requesting a token, because the login code you get when the flow returns to your app is URL-encoded. We wrote about How To Authenticate with Google SSO in Qt with some code samples including this bit that injects a parameter modifier in the flow:
google->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);
}
});
Do that before the initial request, but as suggested by #Giancarlo above, I'd rewrite your code to work asynchronously. It's simpler, and more reliable.