Quoting Michael Grimm trashcan@ellael.org:
On 14 Apr 2016, Viktor Dukhovni ietf-dane@dukhovni.org wrote:
I know, that's an old mail :-) But I have saved it for the time I will be ready to deploy LE certificates. That time has come.
One approach to making sure that DANE TLSA records are less likely to fail that should work well for sites using CA-issued certificates is to publish both "3 1 1" and "2 1 1" TLSA records:
mx.example. IN TLSA 3 1 1 <digest of server public key> mx.example. IN TLSA 2 1 1 <digest of immediate issuer public key>
[…]
#) Would it be possible to get *two* distinct LE certificates, one for the IMAP and one for the webserver .. #) .. and simultaneously *keep* my selfsigned certificate for the the mailserver .. #) .. and forget about the issues mentioned above?
#) Or should I strictly separate my mailserver from the rest by means of distinct domains, instead?
You can get multiple certificates, I have several myself in a single domain, and so this same thing.
I am using an LE certificate for my DANE TLSA records, and I do have the auto-rotation script update the TLSA entry. While this is as simple as it sounds, dnssec makes it more complicated.
You have to remember your dns ttl and and dnssec rrsig ttl and rrsig expiration for the given entry. I have switched to using dns slave servers and in my implementation that means dnssec rrsig values are signed valid for a week, so I don't push out the new certificate from LE, till two weeks after I added the TLSA dns record, to be safe.
The only issue I have had with selfsigned certs is that some mailservers will not send you email if you use one, since the sender has turned on certificate verification, and it will not fail back to non-encrypted to send email. This is mainly a misconfig on their part, but it matters if you want email from them. This has been very minimal impact, but I have seen it a few times.