[josephcsible]

There's actually a third certificate for "USERTrust RSA Certification Authority", also using the same key pair, signed by a different root called "AAA Certificate Services". It looks like the intended replacement for the expiring one is this one, rather than the one where it's the root itself.

[dylz]

It is explicitly not a replacement, but some kind of legacy fallback that they don't want you to use, but exists for enterprise customers that absolutely can't get trust.

[josephcsible]

Are you sure? That's the path that InCommon has been providing me for new certificates since they switched away from the expiring one.

[dylz]

On anything with a modern TLS stack, I see this trust chain:

- Leaf cert (your cert)

- InCommon RSA Server CA

- USERTrust RSA Certification Authority (this is/should be the final point)

[josephcsible]

That's what my browser shows me too, but it's just because it's ignoring the cross-signed one that chains to AAA. The server is sending it, per InCommon's setup instructions.

[tialaramex]

That's correct

The old TLS (versions 1.0, 1.1, 1.2) specifications said that the certificates supplied are to form a chain, starting from a leaf and leading back towards a root.

Pretty much all clients assume that once they can see a way to a root they trust they'll give up following the provided chain and trust that - but sadly not all of them, so "over-specifying" the chain can cause problems.

Modern clients tend to go further, they still assume the first certificate is a leaf, but all other certificates are just potential hints that might be helpful in working out an acceptable trust path. TLS 1.3 actually specifies that clients must tolerate certificates supplied on this basis rather than a strict "chain".

I'm actually surprised at the number of claimed clients which don't have vaguely modern trust stores but do understand SHA256.

[toast0]

> I'm actually surprised at the number of claimed clients which don't have vaguely modern trust stores but do understand SHA256.

All the clients were limited to SHA-1 have already been forced off https; CAs in the CA/Browser forum weren't permitted to issue SHA-1 certs valid past Jan 1 2017, and you had to have gotten those issued before Jan 1 2016. Browsers were showing warnings on SHA-1 certs depending on expiration throughout 2015, so you had to either put up with a warning (and the customer service burden thereof), ditch your old clients and go sha-2 only, segregate traffic, or build custom software to send sha-1 certs to some people and sha-2 certs to others.

Microsoft added support for sha-2 certs in the OS system stack with XP Service Pack 3, released in 2008, and Microsoft was always pretty slow with support on things, other platforms may have supported this earlier. A CA bundle from like 2005-2008 is going to be fairly limiting today. A lot of CAs back then had a 20 year validity period, which may have started 5-10 years before the bundle date. Of course, a lot of bundles today end in 2038, so we'll be screwed then.