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Go will reject certificate chains containing eight distrusted SPKIs

37 points mendym 2 hours ago 16 comments

ericbarrett 1 hour ago | parent

A bit more info (and some discussion linked from these Bugzilla reports):

https://bugzilla.mozilla.org/show_bug.cgi?id=2083709

https://bugzilla.mozilla.org/show_bug.cgi?id=2018979

wnoise 1 hour ago | parent

It is a shame that you cannot have a cert signed by multiple CAs.

(The format seems like it would allow it, but nothing supports it, and in practice CAs demand the ability to actually modify some fields, and then sign that.)

crote 1 hour ago | parent

It is done with intermediate certs, though! It's a common method of establishing trust in new root certs: sign the intermediate with an already-trusted root cert, then wait for the community to adopt the new root cert over the years.

For example, the initial Let's Encrypt Authority X3 was signed by both their own (new, not-yet-universally-trusted) ISRG Root X1, and the universally-trusted third-party IdenTrust DST Root CA X3.

One crucial detail is that it isn't the same certificate. Rather, it is two separate certificates which just so happen to be using the same key pair, so the leaf cert is in essence signed by both intermediate certs at once.

I wonder if it would be possible to do the same thing on your own, actually: can a server present two completely separate cert chains to a connecting client - as long as the leaves use the same key pair? Technically AFAIK the only requirements should be 1) the key pair in use for the connection matches the cert, 2) the domain matches the cert's Subject, and 3) the cert is trusted, so at first glance it might be possible...

wnoise 1 hour ago | parent

That's an interesting wrinkle I was not aware of.

lmz 1 hour ago | parent

X.509v3 just has one issuer Name in the certificate, unless you're talking about something else?

wnoise 57 minutes ago | parent

Yeah, that's one of the complications. It would have to be ignored in processing, or multiple variants be presented at once (preferred).

Certificates are not the same as the public key; multiple certs sharing the same key is essentially the way around this. It's not as elegant as identical signing of the same cert, but it could work.

crote 30 minutes ago | parent

Identical signing of the same cert also runs into issues like "who gets to decide the serial number" and "how to deal with revocation lists: all of, or any of?".

And turning fields like issuer and serial into arrays risks someone accidentally using index 0 for one field and index 1 for another.

Combine that with the insane back-and-forth nightmare that the issuance process would turn into, and I have a very hard time seeing the benefit in it. After all, nobody is stopping you from requesting multiple certs independently, watching the revocation logs, and switching to the backup when required.

jeffbee 56 minutes ago | parent

It's interesting that this sort of policy is baked into a language platform.

fractorial 53 minutes ago | parent

What about it makes it so interesting?

jeffbee 49 minutes ago | parent

Clearly the platform isn't designed to do this. Nobody thought this was going to be a necessary facility. They have just crammed an array of numbers as literal values deep into the standard library. So clearly this is an exceptional event, and not the exercise of a feature that was foreseen.

fractorial 44 minutes ago | parent

Ah, yes that seems to be what URGENT track self-documents as.

stephbook 53 minutes ago | parent

Indeed. But the Java keystore and the Firefox/Chrome/VSCode NSSDB and whatever Python is shipping this week aren't really better.

I wonder what's so annoying about OS certs.

whatevaa 42 minutes ago | parent

It's mostly historical. They used to suck in the past, but the implementations remain. Nowadays you are better off configuring to use OS certificates if possible.

accountrequired 47 minutes ago | parent

"Sir, this is a Wendy's" moment where my compiler thought it was a root certificate authority