- The certificate and private key need to be on your home server since that’s where the TLS is decrypted.
- You should be able to tunnel TLS traffic through WireGuard, so no port forwarding is needed.
- You’d probably want to move Nginx Proxy Manager to your home server as an ingress gateway (and you can keep all the config + TLS certificates). Then on your VPS, you would no longer need the complexity and something like HAProxy, vanilla Nginx, or Traefik would suffice. Seems like NPM has an open issue to add support for TLS passthrough, but in my opinion it’s simpler to just have your VPS forward all traffic to one port on your home server.
For added security, you can make sure the proxy on the VPS only routes traffic for the correct domain using SNI. That way if someone hits your IP randomly, it only goes to your home server if the correct domain name was requested as well.
What you’re doing makes sense to me. Good luck!
Adding onto what TheMrDrProf said: basically LetsEncrypt just wants to know you actually control the domain you’re using to get the certificate. With HTTP challenges, your domain has to resolve to a working HTTP server. With DNS challenges, you need API access to your DNS provider so that Certbot can set a temporary record that proves ownership.
If you’re using NPM to manage your certs, then as TheMrDrProf said as long as the HTTP request from LetsEncrypt can make it to your NPM through the VPS proxy, you should be able to pass the challenge and get a certificate. The IP address of the domain doesn’t really matter as long as the request makes it all the way to the challenge HTTP server, which in this case is NPM.
In NPM, you should see “Use a DNS challenge” option. If you use that and your DNS Provider is supported (if not, I recommend Cloudflare), then your VPS proxy does not even need to be working in order to renew certificates. This has a few advantages such as being able to shut off unencrypted traffic on port 80 completely.