Prevent ASF from accepting requests from public network if IPCPassword is not set

[ezhevita]

Enhancement

Purpose

User may accidentally forget to set IPCPassword while server being exposed publicly to the web which creates a security breach.

Solution

Implementing this suggestion will reduce risk of attacking from external network. IPC server should not respond to any requests (or respond with 403) from public network if IPCPassword isn't set (unless user decides to override this behaviour with config property or program argument).

Why currently available solutions are not sufficient?

There is no available solution that makes sure that user doesn't accidentally expose their IPC server publicly.

Does your suggestion fall into ASF scope?

Yes.

Is your suggestion abiding to Steam guidelines?

Yes.

Additional info

We do have already KnownNetworks property in IPC.config, which may be used as well, and if it's not defined, use private address spaces defined by RFC1918.

[JustArchi]

This is much less "useful" than you may think, indeed, in ASF standalone IPC server scenario, this can drastically reduce the risk and will be the core reason why I'm all in into this suggestion and I consider it a very good enhancement idea.

In practice however, people set up some kind of reverse-proxy in front of ASF, which depending on the user's stupidity, may or may not present itself as user from 127.0.0.1 regardless.

There is not much we can do in this regard, but I totally agree that if the request really arrives from outside of what we can classify as LAN, we should definitely refuse to honor such request as a security measure.