Adapt plugin to running AvNav ssl

[mhomeijer69]

We are running AvNav behind a reverse proxy to support https. The avnav-update plugin isn't working in AvNav https, probably because the plugin.py has the http protocol hardcoded.

[wellenvogel]

Currently AvNav is not really prepared to run behind a proxy.
The update plugin for sure is only one of the candidates that will fail.
There are a couple of problems to be solved:

1. The proxy must be configured for each of the plugins that use an own webserver (at least update, ocharts, signalk)
2. AvNav and the plugins must get an idea on how to reach the system from outside the proxy. https is only one of the aspects - could be other ports, other hostnames/ips.
   To a certain degree x-forwarded headers could be used (if your proxy sets them). But still a mapping would be necessary for the different ports (e.g. the proxy port you would like to set for accessing the signalk web ui would differ from the internal port on the host).
   Unfortunately this would require some effort in all plugins that need this feature.
   Finally:
   What is the use case of running AvNav behind a proxy (with https)?
   Just keep in mind that AvNav (and all the plugins) are not hardened at all - i.e. there is no protection against any kind of malicious actions.
   So in any case you should only run AvNav in a trusted network (and why would you need https in this case?).
   The problem with the proxy on the other hand are certificates - either you would use some freely available trusted ones (like let's encrypt) - but this requires internet access to your server (as said: would not recommend this for AvNav).
   Or if using self signed certs - all the clients will complain until you install some CA cert on them.

[mhomeijer69]

There are a number of reasons to run avnav behind hhtps
Browsers will be blocking http more in the future.
We're building a docker based platform where the apps on the boat are available through a portal. Its easier to use (and to integrate) if all applications support https.
Third reason is that we make the applications available at home through tunnels which is also best if all traffic is https.

For the certificates, we use let's encrypt. We are testing with certificates that are renewed when there's an internet connection and the certificate is a minimum number of days old and what happens when there's no internet connection at all.

[wellenvogel]

What about the other aspect:
How should applications know about the proxy config:
I.e. How should the plugin code know about the external ip and port of your proxy?
Do you already have a concept for that part?
And for the use case:
Still my remark is valid:
You should never expose AvNav directly to the internet.
For tunneling:
I guess for the tunnel itself httos makes a lot of sense - but for the traffic inside???

Anyway - will cost reasonable effort.
Solution ideas are welcome...