I'm using Nginx with reversy proxy instead of NAT.
What will the "Original URL Pattern (Regex)" and "New URL Pattern" be if I want to access a website externally with url "https://my.externaldomain.eu" going to an internal server that can be accessed by "https://externaldomain.localdomain.local".
You don't need any. Just use the new hostname in the http server and the internal one in the upstream server.
Yes, it sounds very strait forward. But than I think there's some other problem. let me explain a little bit further.
"https://my.externaldomain.eu" has a let's encrypt certificate on opnsense and "https://externaldomain.localdomain.local" is running with a self signed certificate.
First thing I tried and which worked was to create an internal website accessible from the lan also with "https://my.externaldomain.eu". The internal certificate was a random selfsigned certificate. With the necessary configuration on Nginx I was able to access the website from an external source.
I copied the configuration and changed the upstream server with "https://externaldomain.localdomain.local".
And at that point i'm kind of lost what to change to make it work.
Does it actually make sense to use TLS between the upstream server and nginx?
If no, go via HTTP. If yes, use a certificate, OPNsense is trusting or disable certificate validation (advanced option; easy but not recommend) in the upstream.
I saw the same kind of question on https://forum.opnsense.org/index.php?topic=15343.0.
but there was no answer given on scenario's:
https://sited.com proxies in to https://192.168.xxx.bbb:443
https://sitee.com proxies in to https://192.168.xxx.ccc:443
They where supposed to work the same, have the same configuration, as the previous examples. Are they?
I'm looking for those configurations.