CTFs | CTF_INSA_2024 | Web | Attention_au_swap

Attention au swap

In this challenge, we are asked to demonstrate some kind of vulnerability regarding the text editor vim. The name of the challenge gives us a hint on where to look for (swap). First I searched swap vim and I found this link https://www.baeldung.com/linux/vim-swap-files. It explains what is a swap file and that if a file called {filename_whit_extention} is created then its swap file name will be .{filename_whit_extention}.swp. Now lets have a look at the website:

As we can see, we have the index.php file. We can try to recover its swap file by searching the following URL:

http://ctf.insa-cvl.fr:1004/.index.php.swp

When the file is downloaded, we can open it with Vim recovery mode:

vim -r .index.php.swp

When Vim is opened, we see the following:

We can now save the file as index.php by running th following command in Vim:

:q! index.php

And we can print in our terminal the flag by running the following command:

head index.php