How can I do custom JWT validation with Flask and flask_jwt_extended?

Question

I want to add additional verification to the token when @jwt_required is called. I want to verify one of the claims. Is there away I can do this with JWTManager?

Currently my code just calls:

jwt = JWTManager(app)

And I decorate the functions with: @jwt_required

Answer 1

Off the top of my head, my inclination would be to create a custom decorator that wraps jwt_required.

Here's a rough idea of how it might look, via the functools.wraps documentation:

from functools import wraps
from flask_jwt_extended import jwt_required
from flask_jwt_extended.view_decorators import _decode_jwt_from_request
from flask_jwt_extended.exceptions import NoAuthorizationError

def custom_validator(view_function):
    @wraps(view_function)
    def wrapper(*args, **kwargs):
        jwt_data = _decode_jwt_from_request(request_type='access')

        # Do your custom validation here.
        if (...):
            authorized = True
        else:
            authorized = False

        if not authorized:
            raise NoAuthorizationError("Explanation goes here")

        return view_function(*args, **kwargs)

    return jwt_required(wrapper)

@app.route('/')
@custom_validator
def index():
    return render_template('index.html')

Here is where you can find the source code for jwt_required.