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!).

Login

ssh bandit12@bandit.labs.overthewire.org -p 2220
7x16WNeHIi5YkIhWsfFIqoognUTyj9Q4

Doc

file (1)             - determine file type
tar (1)              - an archiving utility
gzip (1)             - compress or expand files
bzip2 (1)            - a block-sorting file compressor, v1.0.8
xxd (1)              - make a hex dump or do the reverse.

Solution

The solution for this level is pretty long and tedious. It`s all about understanding how files are compressed, how to see what a random file in memory actually is and how to get the data behind it.

Step 1.

Using mktemp -d you can create a temporary directory in the /tmp path in order to process certain files or create stuff where you otherwise wouldn`t have permissions to do so. We will move the initial data.txt to our new directory and use xxd since we know from the start it is a hexdump. 

bandit12@bandit:~$ ls
data.txt
bandit12@bandit:~$ mktemp -d
/tmp/tmp.esFHBLf5iQ
bandit12@bandit:~$ cp data.txt /tmp/tmp.esFHBLf5iQ/data.txt
bandit12@bandit:~$ cd /tmp/tmp.esFHBLf5iQ
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ cat data.txt | xxd -r > data

Step 2.

After every decompression, it is important to check what type of data we have on our hands using file and apply the appropriate tools until we get to something human readable.

bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data
data: gzip compressed data, was "data2.bin", last modified: Wed Jul 17 15:57:06 2024, max compression, from Unix, original size modulo 2^32 577
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data data.gz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data.gz  data.txt
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ rm data.txt
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ gzip -d data.gz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data
data: bzip2 compressed data, block size = 900k
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data data.bz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ bzip2 -d data.bz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data
data: gzip compressed data, was "data4.bin", last modified: Wed Jul 17 15:57:06 2024, max compression, from Unix, original size modulo 2^32 20480
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data data.gz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ gzip -d data.gz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data
data: POSIX tar archive (GNU)
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ tar -xf data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data5.bin  data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data5.bin
data5.bin: POSIX tar archive (GNU)
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ rm data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data5.bin data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ tar -xf data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data6.bin  data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ rm data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data6.bin
data6.bin: bzip2 compressed data, block size = 900k
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data6.bin data.bz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ bzip2 -d data.bz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data
data: POSIX tar archive (GNU)
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ tar -xf data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data8.bin  data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ rm data.tar
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data8.bin
data8.bin: gzip compressed data, was "data9.bin", last modified: Wed Jul 17 15:57:06 2024, max compression, from Unix, original size modulo 2^32 49
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ mv data8.bin data.gz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data.gz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ gzip -d data.gz
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ ls
data
bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ file data
data: ASCII text

Step 3. Wrapping up

We can see that we`ve hit an ASCII file. Now using cat, the output of the file should be the flag. 

bandit12@bandit:/tmp/tmp.esFHBLf5iQ$ cat data
The password is FO5dwFsc0cbaIiH0h8J2eUks2vdTDwAn