[picoCTF] Secret of the Polyglot

Description

The Network Operations Center (NOC) of your local institution picked up a suspicious file, they’re getting conflicting information on what type of file it is. They’ve brought you in as an external expert to examine the file. Can you extract all the information from this strange file? Download the suspicious file.

First, I downloaded the provided file on my Kali Linux VM by the follwing command: wget https://artifacts.picoctf.net/c_titan/9/flag2of2-final.pdf

The name of the file is flag2of2-final.pdf

I opened the file and it didn’t have much information except some random strings, 1n_pn9_&_pdf_7f9bccd1}

I tried opening the file using the nano command in the terminal, hoping to see more information. When opened with nano, the top of the file stated PNG and included some non-human readable text. This made me suspect that the file is not a PDF but a PNG file.

The suspicion turned out to be true. The file command is used to determine the type of a file and the file was indeed a .png file.

1┌──(kali㉿kali)-[~/Desktop]
2└─$ file flag2of2-final.pdf
3flag2of2-final.pdf: PNG image data, 50 x 50, 8-bit/color RGBA, non-interlaced

So I created a new file by running the following command: cp flag2of2-final.pdf flag2.png

And check out the newly created file! We’re really close to the capturing the flag.

We’re missing the rest of the file but notice the name of the original file, flag2of2-final.pdf. The name implies that it is the second part of the flag.

flag: picoCTF{f1u3n7*1n_pn9*&\_pdf_7f9bccd1}