Defense in depth and the local server

Yesterday I gave a webinar about Database Security in a Hostile World and I got a really interesting question at the end:

If your RavenDB and app are on the same server, would you recommend using certificates?

The premise of the talk was that you should always run in a secured mode, even if you are running on a supposedly secured network. That is still very much relevant if you are running on a single server.

Consider the following deployment model:

(Icons from https://www.flaticon.com/)

As you can see, both the application and the server are running on the same machine. We can usually assume that there is no possibility for an attacker not running on the same machine to eavesdrop on the communication. Can we skip encryption and authentication in this case?

The answer is no, even for this scenario. That may be a viable model if you are running on your development machine, with nothing really valuable in terms of data, but it isn’t a good model everywhere else.

Why is that? The answer is quite simple, there are two issues that you have to deal with:

• At some future time, the firewall rules will be relaxed (by an admin debugging something, not realizing what they are doing) and the “local” server may be publicly exposed.
• Even if you are listening only to port 127.0.0.1, without authentication, you are exposed to anything that is local that can be tricked to contact you. That is a real attack.

In short, for proper security, assume that even if you are running on the local network, with no outside access, you are still in a hostile environment. The key reason for that is that things change. In two years, as the system grows, you’ll want to split the database & application to separate servers. How certain are you that the person doing this split (assume that you are no longer involved) will do the Right Thing versus the minimum configuration changes needed to make it “work”?

Given that the whole design of RavenDB’s security was to make it easy to do the right thing, we should apply it globally.