[thayne]

My frustration is because using a private CA is more difficult than it should be.

You can't just add the CA to system trust stores on each device, because some applications, notably browsers and java, use their own trust stores, you have to add it to.

You also can't scope the CA to just .internal, which means in a BYOD environment, you have to require your employees to trust you not to sign certs for other domains.

And then there is running the CA itself. Which is more difficult than using let's encrypt.

[fleminra]

The Name Constraints extension can limit the applicability of a CA cert to certain subdomains or IP addresses.

[thayne]

How well supported is that?

[8organicbits]

It's hard to say, but I'm super interested if anyone has statistics. Netflix built https://bettertls.com/ to answer these sorts of questions, but somehow forgot to validate constraints set at the root: https://github.com/Netflix/bettertls/issues/19

Anecdotally, I've seen name constraints kick in for both Firefox and Chrome on a Linux distro, but I can't comment more broadly.

[layer8]

It's required by RFC 5280 (and predecessor), so it’s fairly well supported.

[8organicbits]

Do you have any references for that? There are lots of RFCs that are weakly adopted or even ignored. When I tested Chrome they didn't support name constraints, but have since added support. I suspect other software is still lagging.

[thayne]

From the issue for support on chrome, it sounds like RFC 5280 requires it for intermediate CAs, but is ambiguous on whether it is required for root CAs (which in this case, is where you want it). So chrome didn't support it on root CAs until recently, at least on Linux.

Although, ideally, it would be possible to limit the scope of a CA when adding it to the trust store, and not have to rely on the creator of the CA setting the right parameters.