CRYPTOHACK

JWT Secrets

Help

This page offers a convenient way for you to interact with the "JWT Secrets" challenge functions. You can also use GET requests to send and receive data directly from the listed routes/endpoints if you wish. For more information see the FAQ.

Your aim is to recover the FLAG value. Once you have have it, submit it on the Crypto On The Web challenge page.

Source

import jwt # note this is the PyJWT module (version 1.5.0), not python-jwt


SECRET_KEY = ? # TODO: PyJWT readme key, change later
FLAG = ?


@chal.route('/jwt-secrets/authorise/<token>/')
def authorise(token):
    try:
        decoded = jwt.decode(token, SECRET_KEY, algorithms=['HS256'])
    except Exception as e:
        return {"error": str(e)}

    if "admin" in decoded and decoded["admin"]:
        return {"response": f"Welcome admin, here is your flag: {FLAG}"}
    elif "username" in decoded:
        return {"response": f"Welcome {decoded['username']}"}
    else:
        return {"error": "There is something wrong with your session, goodbye"}


@chal.route('/jwt-secrets/create_session/<username>/')
def create_session(username):
    encoded = jwt.encode({'username': username, 'admin': False}, SECRET_KEY, algorithm='HS256')
    return {"session": encoded.decode()}


Interact

authorise(token)
String Input Only
create_session(username)
String Input Only
Output