File Upload Error Through WAF

Our web app uses a file uploader function. It saves the file to a backend server that is seperate from the web app. When the WAF is in proxy mode, the file uploader gives an error, “Unable to find the uploaded file in the directory.”

The file upload function works fine when the WAF is not in proxy mode.

A few details about our environment: HTTPs sessions come in through a load balancer to a pooled web app environment consisting of 5 web servers. There are two backend file servers were the user uploads “land” when the file upload function is evoked.

Thanks in advance for any insight.

You should look at your WAF events to find an even which correlates to a blocked upload. You will be able to find the rule that is blocking the uploads and disable it.

Thank you for taking the time to provide feedback.

The WAF is not blocking the POST; i.e. there’s no default CF “You have been blocked” page and there’s no security event being logged. I’m only getting the “Unable to find the uploaded file in the directory.” error message in the browser.

This seems like an issue with the backend service. You should check the logs of your origin to see why this could be happening.

Thanks. I checked the logs on the backend server but nothing immediately jumped out at me. I may need to put the webserver and backend server in debug mode.

The upload works just fine when the WAF isn’t proxying the traffic.

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