This ever-so-slightly frivolous Java Extension processes web pages dynamically, reordering and replacing text to give the effect of turning the web upside down. Java Extensions are very powerful application delivery tools, but I'm not sure that this is the most productive way to use them...

How does it work?

This example was inspired by the tricks to turn text upside down using JavaScript. It replaces common ascii characters with obscure unicode characters that look roughly similar to the original ones, only upside down:

Replacing characters is the easy part; the challenge is writing an adequate HTML parser to identify strings of inline text, re-order them and apply the JavaScript code:

The parser is far from perfect, but you can have a bit of fun with it. Go ahead and get the FlipText.java source code, or the precompiled FlipText.java class.

To use, upload the class to the ZXTM Admin Server, then configure the victim's virtual server to call the FlipText response rule that is generated.

The extension does not cater for compressed responses from the webserver (and you wouldn't want it to, as decompressing would be an unnecessary overhead), so you may want to avoid this eventuality by adding a request rule that removes the 'Accept-Encoding' header from client requests.

Where to next?

It's not very fast and it's not very useful, so you may prefer to read the other Java Extension and Java Optimization articles on KnowledgeHub. Alternatively, stretch a bad joke a little too far by modifying the Image Watermarking example to flip the images as well!

Enjoy!

Owen Garrett [Zeus Dev Team] 19 June 2008