Nextcloud AIO v30: "Webdav interface seems to be broken"

[GDGundy]

Initial Setup of Nextcloud AIO version 30. It’s containerized, behind a Caddy reverse proxy and addressed via a duckdns.org domain.

Getting this error in the Overview - Security & setup warnings:

Your web server is not yet properly set up to allow file synchronization, because the WebDAV interface seems to be broken. To allow this check to run you have to make sure that your Web server can connect to itself. Therefore it must be able to resolve and connect to at least one of its trusted_domains or the overwrite.cli.url. This failure may be the result of a server-side DNS mismatch or outbound firewall rule.

I’ve spent way-too-much-time trying to resolve this. Anyone have a clue? Please.

[GDGundy]

Well… I’ve spent more of the “way-too-much-time”… And, I’ve figured it out! Or, perhaps I’ve figured out a kludge (is that still a techie word or am I identifying myself as some old Unix guy…) that makes things work.
The issue was/is my edge device which is an Aruba IAP 303H (OS v8.12.x) that simply wont get out of the way. It’s either doing NAT reflection or SSL inspection/interception and sticking it’s self signed cert on the reflection. I can not figure out how to turn it off.
So, the kludge is to add the FQDN to the host’s /etc/hosts file such that it resolves to the host’s IP.

Sounds simple… doesn’t it. FML!

If you are having a similar/same issue, you can test it by :

openssl s_client -showcerts -connect :443 </dev/null 2>/dev/null | openssl x509 -noout -text

If the cert doesn’t look like what you are expecting then you may give my kludge a try and see what happens.

Here’s the lines that I was expecting:

Issuer: C = US, O = Let’s Encrypt, CN = E6

Validity

Not Before: Dec 1 03:40:30 2024 GMT

Not After : Mar 1 03:40:29 2025 GMT

Subject: CN = .duckdns.org

And, at some point in the not too distant future, the Aruba is no longer going to be my edge router/firewall…