Poking a hole in that pesky firewall.
There are more than a few ways to access a firewall. I will be giving a brief tutorial for one of the more common methods. Called “poking a hole”, or professionally called an SSH back door. Please, please be careful with this, any script kiddy with 30 lines of code can exploit an SSH server.
This is a great post by IBM detailing it pretty well. If you have any question feel free to leave a comment and I will assist you.
- SSH from ginger to blackbox.example.com with the
-Rflag. I’ll assume that you’re the root user on ginger and that tech will need the root user ID to help you with the system. With the
-Rflag, you’ll forward instructions of port 2222 on blackbox to port 22 on ginger. This is how you set up an SSH tunnel. Note that only SSH traffic can come into ginger: You’re not putting ginger out on the Internet naked.You can do this with the following syntax:
~# ssh -R 2222:localhost:22 firstname.lastname@example.org
Once you are into blackbox, you just need to stay logged in. I usually enter a command like:
thedude@blackbox:~$ while [ 1 ]; do date; sleep 300; done
to keep the machine busy. And minimize the window.
- Now instruct your friends at tech to SSH as thedude into blackbox without using any special SSH flags. You’ll have to give them your password:
root@tech:~# ssh email@example.com.
- Once tech is on the blackbox, they can SSH to ginger using the following command:
thedude@blackbox:~$: ssh -p 2222 root@localhost
- Tech will then be prompted for a password. They should enter the root password of ginger.