How NOT To Install Self-Signed Certs On Our Plex Server

I have just installed a Plex server, on the host-machine I have on my LAN, that host-machine being named ‘Phoenix’. The purpose of this server is to allow me to access Media Files – i.e. Movies and Photos – Not Just from anyplace within my LAN, but from any place outside my LAN as well, which only I will have access to – as we don’t share our Plex passwords with friends.

Some people might wonder why this is useful to me, especially since Plex is a paid-for service, and since I already have a VPN. And the reason is simply the fact, that to access certain resources on my LAN by way of the VPN, can be slow and cumbersome. It might work for a Samba share, just to fetch a file, but if the objective was to watch a movie which I own, and the original format of which I did pay for, then to leave my tablet with a modified network configuration, and logged in to my VPN, for the duration of the entire movie, would become quite impractical. So Plex was my chosen answer.

One problem which some Plex users could run in to, is the idea that when outside their LAN, they first contact a Web-server, which then redirects them to their private IP address. This idea can lead to another idea, which would be that the following connection from their client-program to their Home LAN is not secure, for which reason some Plex users might want to set up an SSL / TLS certificate to secure that second, redirected connection.

The problem with that last part is, that if our Plex server version is reasonably up-to-date, then we don’t need to do this, because Plex has already done so. There exist several tutorials on the Web, one of which explains to us how to set up a self-signed cert, and another which explains to us how Plex on the Web has already got us covered.

My misfortune last night was the fact that I stumbled on these tutorials, roughly in the order in which they occur above: First, to try to install a self-signed cert, then to learn that Plex already has a system in place with “DigiCert”.

The way in which Plex is intended to work with basic users like me, we all have URLs with the Plex site, that run roughly like so:

*.625d406a00ac415b978ddb368c0d1289.plex.direct

  1. The user first connects to the Web-server-URL, for which Plex inc. has a certificate, which in turn encrypts communication from that point on.
  2. The URL is then not just redirected, but actually rebound, with the IP address of our Home LAN, so that the same cert encrypts the media-flow to our personal server.

What this means is that for most small-scale uses, we don’t need to acquire our own certificate, to secure a direct connection to our LAN. We can just configure our server like so:

plex_2

If we feel that we need greater security, we can change the settings to “Required”, meaning that all connections to our Plex server, except from the same computer (from ‘localhost’), and except from within our LAN, will need to be secure in order to proceed. And then most of us still won’t have to fill in any of the fields below, to set up a custom cert.

But there is a disadvantage to settings ‘Secure Connection’ to ‘Required’. The simple usage-scenarios can be given, that we want to connect to our media-server using an app that doesn’t support TLS, or through the ‘Plex Web’ site, but from within our own LAN. What Plex Web will try to do, is to rebind the IP-address to the IP-address  which our server has on the WAN, and to give us a secure connection that way – even though we’re connecting to a place on our own LAN!

This can easily fail, because It can go against router policy, to rebind IP addresses to our own LAN. It can also go against browser policies, in the form of ‘Application Boundary Security’, where an external site is not supposed to gain access to resources on our LAN…

But as it stands, each of my Android clients was already set up by default, to ‘Allow Insecure Connections: Never’, my Roku works, and there is no need to use Plex Web from home.

I suppose the reader might wonder, what would happen if indeed, he was to set up a Custom Certificate for his Plex server at home…

Essentially, that certificate would still need to be signed in such a way, that it proves the ownership of a custom domain-name, which by default, browsers and clients would need to connect to, in order to obtain the service.

Because this can be frustrating for any user whose clients connect by way of the Web-site, the server-operator would additionally need to tell this Web-site, to associate his personal URL with his Plex account.

And at that point, the situation can turn into a failure again, for users who wish to connect to their server, from within the same LAN, but for a different reason than before. Because, the Web-site would try to carry out a hand-off, by which the client / browser communicates directly with the server.

From within our own LAN, this would mean that a LAN-IP-Address wants a direct connection to a WAN-Port. If our router does not support loop-back, the effort will next fail for that reason. And such an effort may have had as reason, to close the security gap that exists, when we merely tell the server to Prefer a secure connection / Allow an insecure connection, from within our own LAN.

My own router does not support loop-back. My ability to run a Web-site depends strongly on my grasp of the required logic, and on tests which I perform on occasion, while outside my home, while connecting to the WAN from elsewhere.

Another phenomenon which takes place, is that my local Plex server is logged-in to the remote, Web-based Plex server, which in turn receives telemetry from the local server. Hence, their server won’t make naive mistakes, such as to assume that I can obtain a connection, without first verifying that I can.

Dirk

 

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