SSRF in file upload file URL

The problem

It was possible to store the response of a request to a service within the private network to a file. This could be done by providing a private URL in the upload user file by private file.

The fix

Resolve the IP address of the provided URL and check if it is a private IP address. If so, an error will be raised.

How to test

• Try to fetch a URL from a public internet exposed file which should work.
• Try to fetch the a URL of an internal network, for example http://localhost:8000/test.txt which should fail.

CVE: gitlab-org/cves#221 (closed)