21 - Get the Tank

You are trapped at a military base, you got zombies coming from the right, left and front. Of course, you are running out of ammo and there is no much hope left, but there is a huge door behind you. You got reason to believe that there is a tank behind it, but it is secured with a secret masterkey. There is also a terminal on the left side with a binary on it to authenticate and open the door called "tank". You are lucky and the developer was really exhausted when creating the application, so there might be some bugs you can use to get the masterkey, but watch out for the zombies! SSH: ctf.fluxfingers.net PORT: 1235 USER: ctf PASS: ttkas77s81nnxla
 

credits: 400 +3 (1st), +2 (2nd), +1 (3rd)