Quick and Easy SSH MITM

A quick intro to using mitmproxy to man-in-the-middle an SSH connection.

So you want to sniff an SSH connection (that you have access to) but wireshark is giving you junk? Luckily someone has written a tool for that. The mitmproxy by Maximilian Hils allows you to plop a fake server in between your SSH client and the SSH server you're connecting to.

I wanted to have a nose at the data sent from git to github over SSH. This is what I did.

# Download mitmproxy
git clone https://github.com/mitmproxy/mitmproxy.git

#Generate mitm keys (these go to ~/.mitmkeys)
./mitmkeys

Now you want to install the SSH key you just generated to the server you want to mitm.

#Install SSH key
ssh-copy-id -i ~/.mitmkeys/id_rsa.pub user@victimserver

Then run the proxy, pointing it at the victimserver.

#Run proxy
./mitmproxy_ssh -H victimserver

This runs the proxy on localhost:2222

Now simply connect to the local proxy:

ssh localhost -p 2222

And ta-da! You should see the raw data sent between client and server in the window you ran mitmproxy_ssh.