Mohamed Sayed - Blog

 ( بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ ) (إن أحسنت فمن الله، وإن أسأت فمن نفسي والشيطان) It was a nice CTF, I got 2nd place with my guys: Hissien Misbah ( Twitter ) Mohamed Bebo ( Linkedin ) Sameh ( Linkedin ) Osama Zidan ( Linkedin ) A picture during solving this challenge in the last 5m of the CTF (thinking that we got 1st place). Let's walk through the Web Challenge Hot Proxy, note that we did not solve it during the time of the CTF it was a minute way, let's start. Note: there is no source code in the challenge attachment, I requested it from the author ( @serWazito0 ) thanks to him, challenges files ( ASCWG_2024_CTF ). Note: the flag file in the server and called "flag_<RANDOM>.txt", so we have to get RCE. From the title I know that there is an "SSRF" vulnerability in this challenge and from the description, we know that there is an internal application called "app1" with a route called "/secret" so our target is to access

 ( بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ ) (إن أحسنت فمن الله، وإن أسأت فمن نفسي والشيطان) Let's check the "cockatoo" pwn challenge from Blackhat MEA CTF 2024. Reverse the Binary we note that the binary takes the input byte by byte and there is a counter (i hate static analysts) Dynamic analysis  Let's jump to GDB and see what happened. I set a breakpoint on the road to get the stack address in which our input will be stored, and the following screenshots show our input increase and the counter before the RIP address. and the payload to overwrite the counter and control where the next write will be in the following screenshots  and we added to the counter (16) and could overwrite the RIP now we have to find our gadgets and do a simple execve, right?!!! NOOOOOO Exploit we don't have gadgets for "rdx, rdi, rsi" and we need to do "execve(rdi, rsi, rdx)", but we have "syscall" and "pop rax" so its time for our SROP attack. we