I once wrote an ELF by hand for a CTF challenge. The challenge was to have an shared library such that when it is passed to LD_PRELOAD it spawns a shell by execve

LD_PRELOAD=<ELF> /bin/true

The constraint being the ELF needed to be less than 196 bytes so obviously it could not be created by gcc. In the end I could not believe it ran, considering the amount of hacks that I had to do to trim it to 193 bytes.

https://github.com/TeamGreyFang/CTF-Writeups/tree/master/Pla...