NOTE: Six hours after starting, I'm abandoning this as Facebook doesn't allow anyone to use the "user_groups" scope. I'll be forking it and trying to rig something similar up via Twitter Lists instead.
This is FBRP: "FaceBook Reverse Proxy".
This started out with the idea of making a generic reverse proxy protected by Facebook auth.
For now, it's more of a simple file server (powered by net/http's FileServer) and protected by membership in a secret Facebook group.
It expects users to login via Facebook and only allows users who are members of a specific, secret group.
There's a systemd unit file for this as well.