web/jwt-1

About

"I just made a website. Since cookies seem to be a thing of the old days, I updated my authentication! With these modern web technologies, I will never have to deal with sessions again. Come try it out at http://litctf.org:31781/ ."

Home Page:

You can sign up to the website.

However, when you click "GET FLAG", the webpage gives you "Unauthorized".

Recon

As described in the introduction of the challenge, there is a JWT cookie after signing in.

After doing some research, I came across the tool called JWT_Tool. If I put my cookie in, it gives me all the info.

Exploitation

It seems like I need to change that admin value to True. You can do that with the -T flag:

python3 jwt_tool.py eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoidGVzdDMzMyIsImFkbWluIjpmYWxzZX0.pexv7afakRnfXaUonh0o0Y96xPDz%2BSOsM453Mn%2F0YD -T

Then, put the new cookie in the browser and hit "GET FLAG".