In this write-up I will discuss how I managed to solve the challenge "babystack" from 0ctf with a technique called return to dl-resolve. I did not know this kind of return-to attack before the contest. In the following sections a detailed explanation of the entire exploit will be presented.
I downloaded the provided binary babystack and quickly fired up binaryninja alongside with gdb to analyze it. I quickly realized a buffer overflow vulnerability is present within sub_804843b.
My first approach was to solve this challenge using a return-to-libc attack by leaking the base address of the library and call system in order to get a shell.
This technique is contingent on:
- Leaking libc base address
- Knowing the version of libc to get the offset of
system.
However, the version of libc on the remote server was unknown and the ELF did not provide any function that can be us