Over The Wire - Bandit - Level 13#

Level Goal#

The password for the next level is stored in the file data.txt, which is a hexdump of a file that has been repeatedly compressed. For this level it may be useful to create a directory under /tmp in which you can work. Use mkdir with a hard to guess directory name. Or better, use the command “mktemp -d”. Then copy the datafile using cp, and rename it using mv (read the manpages!)

Commands you may need to solve this level#

grep, sort, uniq, strings, base64, tr, tar, gzip, bzip2, xxd, mkdir, cp, mv, file

Steps#

This challenge is kinda weird for me, I don’t know if I missed something to make it easier, but it was kinda of a struggle to finish it.

The first thing to do is to read the file data.txt with the cat command. It’s a bunch of text of a hexdump. A hexdump is a datadump of a binary file to text showing more information about the file, probably made with the xxd command.

The good thing is that the file can be reversed to the original binary using the xxd command with the -r option:

-r | -revert
    reverse operation: convert (or patch) hexdump into binary.

But we are not doing this inside the home folder, we are doing many file management, so we are going to create a temp folder and play inside it. So we are going to use the command mktemp -d to create a temporary folder, and enter it with cd.

Then, we copy the file from home to our temporary directory. We’ll use the cp command to copy the file from folder to the new directory:

cp ~/data.txt /tmp/temporary-folder/

And then, we can revert the hexdump to a binary file with xxd -r:

xxd -r data.txt data.bin

Sisyphus Decompression#

From now we will have a checklist to repeat until we have our password:

1. file : to identify the type of compression the file is
   • If the file type is gzip, rename the file to end with .gz with the command mv data.bin data.gz
2. extract the file with the correct file type:
   • gzip : use the gunzip command to extract the gzip file
   • tar : use the tar -xvf command to extract the tar file
   • bzip2 : use the bzip2 -d command to extract the bzip2 file
3. repeat

Repeating for some time, you will find a file that is an ASCII with the password for the next level.