Docker Container/Service with Same Port: Best Practices?
I am very new to using docker. I have been used to using dedicated VM's and hosting the applications within the servers OS.
When hosting multiple applications/services that require the same port, is it best practice to spin up a whole new docker server or how should I go about the conflicts?
Ie. Hosting multiple web applications that utilize 443.
Thank you!
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Thanks a ton! I did not realize you could have a different listing port vs internally used port.
I have done what you mentioned and used a random port internally and kept 443 as the listening port. I am using Caddy to then direct the traffic reverse proxy it.
Thanks again!
if you’re only going to be using those services through the proxy, it can also be a useful security upgrade to not forward their ports at all, and run caddy inside docker to connect to them directly!
if you forward the ports (without firewalling them), people can connect to them directly which can be a security risk (for example, many services require a proxy to add the x-forwarded-for header to show which IP address originally made the request… if users can access the service directly, they can add this header themselves and make it appear as though they came from anywhere! even 127.0.0.1, which can sometimes bypass things like admin authentication)
Thank you! Just to clarify - I should only forward 443 & 80 for Caddy. Then in the Caddy config define the ports within the reverse proxy. Is that correct?
How safe/secure is it to host a public website or services like a Lemmy instance doing this?
For services I don't care to be available outside of my network, I am not adding to Caddy and accessing them directly via internal IP.
so what you ideally want is people to ONLY be able to access your backend service through caddy, so caddy should be the only one with ports publicly accessible, yes
caddy running in the same docker network as your services can talk to those services on their original ports; they don’t need to even be mapped to the host! in this case, you have 3 containers: caddy, service 1, service 2… caddy is the only one that needs to have ports forwarded and you can just forward caddy:443 and no need to worry! then caddy can talk directly to services:80 or services:443 (docker containers show up to other docker containers by their container name! so if you run eg: docker run … —name lemmy, then caddy in the same docker network would be able to connect to http://lemmy:80!)
.. but if you forward say service 1 and 2 on :8443 and :9443 (without firewall, and even with it makes me uncomfortable - that’s 1 step away from a subtle security problem), someone could be able to access <yourserver>:8443, right? so they don’t have to go through caddy to get to the backend service… for some services, that can be a big deal in ways that it’s difficult to understand, so it’s best to just not allow it if possible
an alternative is to make sure your services are firewalled so that nobody from the internet can hit them, but caddy still can… but i like this less, because it’s less explicit what’s happening so it’s easier to forget about
Thank you for all of this info. 443 is now my only open port and directs to my Caddy server. For extra security, I'm going to look into implementing an authentication portal for each backend service that is not "public" for all.
You are very welcome! Let me know if you need anything else.