Zwiebel was a pretty interesting reversing task in Tum CTF 2016. I spent around 6 hours solving it. Used Z3, IDA pro, GDB, LD_PRELOAD and Capstone.

Original writeup (https://medium.com/aneesh-dogras-blog/writeup-for-zwiebel-tum-ctf-2016-e312fc129037#.m9fjqf1xy).