Image upload to service issue with f5 firewall
I recently faced an issue with a firewall called f5, the issue began when I uploaded an image, check the attached image.
The firewall blocks the stream of bytes, so I don't know if the problem is in my code or in the firewall.
To be sure that my code has no problem I made an MVC application to test upload and in fiddler the same symbols appeared.
These are the WAF Errors:
- HTTP protocol compliance failure - the request was having a NULL, which could cause buffer overflow issues.
- Failed to convert character - F5 is not able to understand the data after decoding the HTTP traffic and is blocking it.
fiddler capture for MVC upload
Firewall Error Image
What your seeing is F5's WAF (Web Application Firewall), and its blocking the request because something in the request is not matching up with the defined policy of the application. Can you screen shot just below, the general details section, this will usually include the reason for the block (the violations that occurred).
To answer the second part of your question, the symbols are the F5 reversing the encoding, and trying to show you the real characters being sent, this is to get around possible double, triple, etc encoding attacks.