It’s not as simple as described below, I’m afraid… It appears that it’s not that easy to obtain new/correct certs from LetsEncrypt that are not cross-signed by DST Root X3 CA. Additionally older OpenSSL version (1.0.x) seems to have problems. So even when you think that your system is now ok, the remote server might refuse to accept your SSL cert. The same is valid for the SSL check on xmpp.net, which seems to be very outdated and beyond repair.
Honestly, I think the solution needs to be provided by LetsEncrypt…
I was having some strange issues on my ejabberd XMPP server the other day: some users complained that they couldn’t connect anymore to the MUC rooms on my server and in the logfiles I discovered some weird warnings about LetsEncrypt certificates being expired – although they were just new and valid until end of December.
It looks like this:
[warning] <0.368.0>@ejabberd_pkix:log_warnings/1:393 Invalid certificate in /etc/letsencrypt.sh/certs/buildd.net/fullchain.pem: at line 37: certificate is no longer valid as its expiration date has passed
[warning] <0.18328.2>@ejabberd_s2s_out:process_closed/2:157 Failed to establish outbound s2s connection nerdica.net -> forum.friendi.ca: Stream closed by peer: Your server's certificate is invalid, expired, or not trusted by forum.friendi.ca (not-authorized); bouncing for 237 seconds
When checking out with some online tools like SSLlabs or XMPP.net the result was strange, because SSLlabs reported everything was ok while XMPP.net was showing the chain with X3 and D3 certs as having a short term validity of a few days:
After some days of fiddling around with the issue, trying to find a solution, it appears that there is a problem in Ejabberd when there are some old SSL certifcates being found by Ejabberd that are using the old CA chain. Ejabberd has a really nice feature where you can just configure a SSL cert directory (or a path containing wildcars. Ejabberd then reads all of the SSL certs and compare them to the list of configured domains to see which it will need and which not.
What helped (for me at least) was to delete all expired SSL certs from my directory, downloading the current CA file pems from LetsEncrypt (see their blog post from September 2020), run
ejabberdctl restart (instead of just
ejabberdctl reload-config). UPDATE: be sure to use dpkg-reconfigure ca-certificates to uncheck the DST Root X3 cert (and others if necessary) before renewing the certs or running update-ca-certificates. Otherwise the update will bring in the expired cert again.
Currently I see at least two other XMPP domains in my server logs having certicate issues and in some MUCs there are reports of other domains as well.
Disclaimer: Again: this helped me in my case. I don’t know if this is a bug in Ejabberd or if this procedure will help you in your case nor if this is the proper solution. But maybe my story will help you solving your issue if you experience SSL certs issues in the last few days, especially now that the R3 cert has already expired and the X3 cert following in a few hours.