Newbie question about middleware and controllers

[jhoddevik]

I'm just trying to wrap my head around these concepts. What I want to do is this:
I want to receive headers that contain authorisation information. And then I have a class that connects to an external source using different authorisation information based on what my Leaf app receives.

So what I imagine would be best to do is:

1. Have a middleware that checks authorisation and somehow holds that info
2. Initialise a controller that gets the autorisation info from my middleware.

Sounds easy.

What I find difficult is:
How can the middelware save variables and pass them to the controller?