How to stop QNetworkAccessManager from caching NTLM credentials?

[Nerdan]

Qt 5.15.2

Hello, I'm using QNetworkAccessManager for NTLM authentication. After successful authentication, QNAM caches credentials, which I don't want.

Is there any convenient way of clearing the cache or preventing QNAM from caching credentials? Or can I trick Qt into firing the authenticationRequired signal?

I've tried setting the request attributes:

• CacheLoadControlAttribute to AlwaysNetwork - didn't help
• CacheSaveControlAttribute to false - didn't help
• DoNotBufferUploadDataAttribute to true - didn't help
• AutoDeleteReplyOnFinishAttribute to true - crashed the server
• AuthenticationReuseAttribute to Manual - started caching wrong credentials

I tried using clearAccessCache and clearConnectionCache - depending on the call place, calls crashed the server, slowed down the completion of requests, or returned a 401 error or a 5 Operation Cancelled error.

I tried closing, aborting, and disconnecting replies in the authenticationRequired and finished signals:

• abort() - didn't help
• close() - sometimes returned a 5 Operation Cancelled error
• disconnect() - led to an infinite loop

I tried to manually get the cache before, inside, and after authenticationRequired - couldn't get (nullptr):

QNetworkDiskCache *diskCache = qobject_cast<QNetworkDiskCache *>(manager.cache());
QUrl url = request.url();
if (diskCache) {
    QNetworkCacheMetaData metaData = diskCache->metaData(url);
    if (metaData.isValid()) {
        diskCache->remove(url);
    }
}

I tried to save a pointer to QAuthenticator inside a class derived from QNetworkReply and set the user and password to an empty string before and after authenticationRequired - didn't help.

Is there something I'm missing?

[SGaist]

Hi and welcome to devnet,

Please provide a minimal compilable example that shows the issue.

You should also check with the latest Qt 6 to see if there's a difference in the behaviour.

[artwaw]

@Nerdan Disk cache (or AbstractNetworkCache you're casting to disk cache) has nothing to do with auth.

I suppose you're looking for this? https://doc.qt.io/qt-6/qnetworkaccessmanager.html#clearAccessCache

Please note, documentation is from Qt6.7, please check if your implementation is same.

[Nerdan]

@SGaist It's very hard to provide a minimal compilable example because it's part of a big application. Also, I've tried upgrading from Qt 5.15.2 to Qt 6.7.2, but it leads to a crash of the application, unfortunately(I've resolved all compatibility errors and installed the Qt 5 Compatibility module)

@artwaw I've tried using both clearAccessCache and clearConnectionCache without success.

I greatly appreciate your time and attempts to help.

[JonB]

@Nerdan
clearAccessCache() seems to me clearly to be the way you are expected to do it. If you say that "crashes" for you but you can't provide a repro then it's difficult to address.