Comment your amount - SMP CTF 2024 - Selection Round

Posted on by rahisec

In attachment password.zip is provided

password.zip contains following files:

  1. password.bmp : a bmp image but it doesn’t open.
  2. flag.zip : it’s password protected

so it seems like we need to find password in password.bmp and use it to unzip the flag.zip

image.png

I tried to open the bmp file but it shows file is corrupted.

I open password.bmp in hex editor. I’m using HxD.

image.png

It seems like the file is corrupted because something is missing in the file’s header signature.

so i downloaded a sample.bmp file and compared with password.bmp file.

image.png

So, there indeed a header signature is missing. here we can see the actual bmp file starts with BM which hex value is 42 4D.

so I edited my password.bmp files header and replace these two hex value and create a new modified password1.bmp

image.png

when I open it , it shows the picture below.

image.png

now I tried to open flag.zip and provided the password found in that image.

image.png

and we got the flag!!