Over The Wire - Bandit - Level 09#

Level Goal#

The password for the next level is stored in the file data.txt and is the only line of text that occurs only once

Commands you may need to solve this level#

grep, sort, uniq, strings, base64, tr, tar, gzip, bzip2, xxd

Steps#

We need to find an unique line in the data.txt file that does not repeat, because this file is filled with possibilities for a password. The first instinct is to use the uniq command, because, in it’s description:

uniq - report or omit repeated lines

And it’s correct to use the uniq command, that only shows lines that are unique and not repeated. But, in the end of the uniq manual page, we have:

'uniq' does not detect repeated lines unless they are adjacent.
       You may want to sort the input first, or use 'sort -u' without
       'uniq'.

So, before we use the uniq command to filter the repeated lines, we need to sort the lines alphabetically, and then use the uniq command. So the command will be something like:

sort data.txt | uniq -u

Where:

sort : sort the lines alphabetically
data.txt : file to be sorted and processed
| : pipe special character, to send the sorted content to the uniq command
uniq : command to report or omit repeated lines
-u : option of uniq to only print unique lines

With that, only the password to the next level will be printed.