CTF Challenge: Information

Challenge Overview:

• This was the description for the challenge:

Approach:

1. Importing the file:I always prefer to have open PicoCTF website on my local machine and then use the virtual machine to solve problems, as you can see i use the wget command to get the file.
2. Viewing what we dealing with:
   • To open the picture you use the following command:

      eog cat.jpg
     

   • When viewed this picture, i thought of many approaches, such as image steganography- which involves hidden information inside the image.
   • But even before going there the standard approach always stays the same, that is to check the file type and the metadata.
3. Further Analysis: We need to verify and know what we are solving.
   • informaion about file:

      file cat.jpg
     

   • Meta-data of the image:

      exiftool cat.jpg
     

   • So now, we see strange things. This is when you know that it could be you the vulnerability or in this case, our hidden flag. Normally, the meta-data should should the data in clear text. But in this case we some gibberish, what’s that. A closer look:
     
   • This looks like some text, encoded to hide information.
   • The encoding method, that always comes in my mind is base64, and it is common in ctf challenges.
4. Decoding: Let’s see what happens when decode the encoded text using base64. Normally you see a base64 with an equal sign at the end of the decoded text. But in this, we do not see that.
   • the flag😆:

      echo "cGljb0NURnt0aGVfbTN0YWRhdGFfMXNfbW9kaWZpZWR9" | base64 -d
     

   • Alternatively, if you do not like the terminal. You could use the following to Cyberchef. Great tool!, that has almost all the encryption/encoding/hashing methods, and allows to decode as well.