XXE FTP Server - A {web,ftp}-server for XXE

XXE - FTP OoB basics XXE offers a great attack avenue for reading files from a vulnerable web-app. One of my favourite XXE attacks involves protocol handler abuse, where you use FTP to do an out of band read. This is useful in those cases where you have XXE but it is blind. Unlike the normal OoB retreival through HTTP, FTP works with newer versions of Java (>1.7) and there are fewer characters which break the retrieval....

December 11, 2016 · 3 min · 567 words · Etienne Stalmans

tcpprox - An intercepting TCP proxy

On numerous occasions I’ve run into custom binary network protocols that I’ve wanted to reverse. The usual goto here is to fireup wireshark/tcpdump and view the traffic as it goes accross the wire. This works really well in most cases, but how about traffic that uses TLS to encrypt the traffic? Unless you have the private key for the server, you are stuck with viewing encrypted traffic in wireshark. Not ideal for reverse engineering....

December 11, 2016 · 7 min · 1329 words · Etienne Stalmans

Powershell Shells

It’s been a while… I figured it’s about time I post something here again. A while back I was required to see how much damage can be done by a malicious staff member. The one caveat here was that I had to test directly from the Windows box and had extremely limited outbound comms. For various reasons the usual tool-suites were out and I took this as a challenge to see how much damage I could do by coding tools on the “employee machine”....

October 3, 2016 · 2 min · 333 words · Etienne Stalmans

Viewing, modifying and replaying websockets

A few assessments back I ran into a web app that made libral use of websockets. Now it’s been a while since encountering an app that makes use of websockets for such a large portion of it’s content and I’d forgotten what a PITA it can be trying to intercept and replay websocket requests. Seeing as it was a web app assessment I naturally turned to trusty Burp Suite Pro. Burp has supported websockets for a long while now, but far as I could find, this support only allowed you to intercept websocket requests and view/modify them....

September 10, 2015 · 2 min · 320 words · Etienne Stalmans

Abusing File Converters

Every now and then you run into a new file format and you find that you may not have a tool to parse that file. Or you are looking for an easy to use solution for you mom to access the photo’s you sent her in a .tar archive. This is where file conversion services come in, a quick Google for “online file converter” will yield multiple results. One thing to keep in mind when converting files, is that different file formats may support different features....

August 22, 2015 · 3 min · 588 words · Etienne Stalmans