How to establish CA Chain for firefox using new virtualmin letsencrypt SSL feature?

Virtualmin
1

Centos 6 with Webmin/Virtualmin and Apache:

I tried out the new letsencrypt feature for my virtualhost and initially it failed. After some searching I found that I needed to install python-argparse, after that the lets encrypt tab on the SSL management page for my virtual host worked and setup my vhost with a cert from Lets Encrypt! Great… works fine in Chrome. But… Firefox doesn’t like it and the tester at ssllabs.com that analyzes certs gave me a grade C.

Virtualmin SSL setup vulnerable to poodle, no perfect forward secrecy… I was able to fix all that by tinkering with the directives…

But I cannot for the life of me figure out why firefox still doesn’t like the cert and I get "This server’s certificate chain is incomplete. Grade capped to B. " at SSL labs. - Everything appears to have worked correctly getting the Let’s Encrypt cert installed. My CA tab shows “Let’s Encrypt Authority X1…”

Any ideas on how to fix this chain issue?

2

Found my own answer… I went to: https://whatsmychaincert.com

and it generated the chain cert I needed to which I simply added to an SSlCerticicateChainFile directive in my virtualhosts config manually… I think doing this automatically would be a nice improvement though for the feature so that sites can get an Instant A rating from SSL Labs.

3

The solution proposed here fixed the issue for me.