OverTheWire: Bandit Level 20 to Level 21

Level goal: There is a setuid binary in the homedirectory that does the following: it makes a connection to localhost on the port you specify as a commandline argument. It then reads a line of text from the connection and compares it to the password in the previous level (bandit20). If the password is correct, it will transmit the password for the next level (bandit21).

NOTE: To beat this level, you need to login twice: once to run the setuid command, and once to start a network daemon to which the setuid will connect.

NOTE 2: Try connecting to your own network daemon to see if it works as you think

In this level, basically we need to setup a listener service to listen on any port, and then use the binary submit this level’s password to it. If It is correct, it will provide the password to the next level.

First, let’s check what are the ports opened.

Now you setup your own listener which echo the current level password when any clients connected.

Now you setup another terminal and try to check if the service is there (of course it will be there) and perform testing by trying to connect,

Notice that nmap port scan has detected the service at port 60000 which you have set up in the other terminal? Now, use the suconnect binary to establish connectivity to port 60000

Password matches, now the next password is sent to the server listener.

The password to gain access to the next level is gE269g2h3mw3pwgrj0Ha9Uoqen1c9DGr.