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.)
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...
Another option: Use ACME together with ARI (RFC 9773). The client checks ARI data every hour. If the cert needs to be replaced – for example like in this scenario – the CA will inform the client, which in turn would then request a new cert.
I know it’s not convenient to automate for every kind of device though. I guess in some of those cases it might be better to have a load balancer in front of the device. Or use an alternative PKI.
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.
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.
I mean, they're the TLS certs are baked into the stdlib 'tls' package, not the compiler itself.
It's just an unfortunate unforced error that the go TLS package is bundled along with the compiler, in the same way Safari being bundled with iOS updates is an unforced error meaning a safari security bug requires a full OS update.
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.
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.
https://bugzilla.mozilla.org/show_bug.cgi?id=2083709
https://bugzilla.mozilla.org/show_bug.cgi?id=2018979
(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.)
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...
Another option: Use ACME together with ARI (RFC 9773). The client checks ARI data every hour. If the cert needs to be replaced – for example like in this scenario – the CA will inform the client, which in turn would then request a new cert.
I know it’s not convenient to automate for every kind of device though. I guess in some of those cases it might be better to have a load balancer in front of the device. Or use an alternative PKI.
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.
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.
It's just an unfortunate unforced error that the go TLS package is bundled along with the compiler, in the same way Safari being bundled with iOS updates is an unforced error meaning a safari security bug requires a full OS update.
data from https://www.ccadb.org/resources
I wonder what's so annoying about OS certs.