<update 03:30pm> I’ve had some feedback that this post describes a concept that is too basic to put into blog form. I can see where this confusion may occur. Most literature that describes pivoting through Meterpreter, shows how to setup a payload connection that goes through Meterpreter (e.g., a bind payload). What isn’t well known or documented, is the Metasploit Framework’s ability to setup a connection that calls home to you through a Meterpreter pivot (e.g., a reverse payload bounced through a pivot host). This nuance is important.
Let’s say I have admin user credentials for a server that can’t egress out of the network and connect to me. This server has a host-based firewall as well. Only port 445 is allowed in. If I try to deliver a bind payload, my attempt to connect to the host to establish the session will get stopped. If I try to setup a reverse connection, directly to my host on the internet, this will fail too–because the host can’t egress and connect to me. What else do I do? I could try to schedule a task to drop the firewall on the server (with psexec_command). I’ve done this. In some cases though, this might generate an alert that draws unwanted attention to my activity. The desirable solution is to compromise the server (172.16.48.3) and send the reverse connection through an already compromised host (172.16.48.81), before it reaches me. This is what I describe how to do in this blog post.</update>
Here’s how to do it:
First, you need to compromise a system and get Windows Meterpreter onto the system. However you do it is fine with me.
Next, you need to setup a pivot into the target network. Here’s how to do it:
Notice that 172.16.48.81 is my initial compromise and pivot host.
Last, you need to exploit another system and setup the reverse connect back accordingly. Ask yourself: how would I do this? Do you have an answer? Let’s see if you’ve arrived at the correct one.
Setup the exploit as you would normally. Next, set LHOST to the IP address of the compromised system that is also your pivot point. Change LPORT as well. Now, fire the exploit.
Notice that the Metasploit Framework recognizes the situation and sets up a reverse port forward for you. This is indicated by the string “Started reverse handler on [compromised host] via the meterpreter on session [pivot session]”. If your exploit fired correctly, you will have a session reverse connected through your compromised system.
Here’s the output of netstat on the compromised system:
Pretty neat.