Overthewire Bandit Level 10 -> 11

Solution for the Overthewire.org Bandit level 10 -> 11

Level Goal

The password for the next level is stored in the file data.txt, which contains base64 encoded data.

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Walkthrough

Login to the server using the password obtained from the previous level Bandit level 9 -> 10.

username: bandit10

ssh bandit10@bandit.labs.overthewire.org -p 2220

After logging in we can find the data.txt file located in the current directory.

bandit10@bandit:~$ ls
data.txt

Running the file command tells us it is a text file.

bandit10@bandit:~$ file data.txt
data.txt: ASCII text

But when trying to read the contents of the file it is unreadable to humans.

bandit10@bandit:~$ cat data.txt
VGhlIHBhc3N3b3JkIGlzIElGdWt3S0dzRlc4TU9xM0lSRnFyeEUxaHhUTkViVVBSCg==

As the level goal said the contents of data.txt has been encoded using base64. Linux has a command line tool for encoding and decoding base64.

base64 is the command. Checking the manual page for base64 we can see how to decode data.txt.

BASE64(1)                                           User Commands                                           BASE64(1)

NAME
       base64 - base64 encode/decode data and print to standard output

SYNOPSIS
       base64 [OPTION]... [FILE]

DESCRIPTION
       Base64 encode or decode FILE, or standard input, to standard output.

       With no FILE, or when FILE is -, read standard input.

       Mandatory arguments to long options are mandatory for short options too.

       -d, --decode
              decode data

The -d option will allow us to decode base64 back into its original format which in this case is ASCII text.

Running the following command will give the password for the next level.

bandit10@bandit:~$ cat data.txt | base64 -d
The password is IFukwK##########################