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by tialaramex 2178 days ago
> And if all the CAs band together and say, sorry losers, we're gonna keep doing things our way, what are the browsers gonna do?

For one thing you should consider that several of the companies that make browsers also operate a Certificate Authority. For example Google's GTS is represented in that m.d.s.policy thread by Ryan Hurst (whereas Ryan Sleevi is there mostly choosing not to put on his Chromium Web PKI hat). Microsoft likewise controls trusted roots. Apple does operate its own PKI but is not presently broadly trusted, though if it felt the need I'm sure they have people.

Also the most popular (for this purpose) Certificate Authority is ISRG's Let's Encrypt and they've got no reason not to co-operate. The Web PKI is all they do anyway.

This is often portrayed as though browsers are obliged to either distrust everything instantly or allow CAs to do whatever they like, but neither of those is realistic. The major trust stores all already have imposed constraints short of distrust.

You bring up Apple as an example. Unless I've missed it somewhere Apple never announced their 398 day limit as a matter of issuance policy it's simply a fact that Safari and the Mac operating system won't trust new certificates with longer lifespans after a set date. So if one or more CAs decided not to co-operate, nothing happens at first. Nothing whatsoever.

Then, gradually, a few subscribers buy (or renew) 2 year certificates, and these new certificates don't work in Safari. Some of these subscribers will call customer services at the CA where they purchased the certificate. Why doesn't it work in Safari? How can they fix this?

What does the CA say? "We intentionally sold you a product that won't work. Ha ha ha, it's a funny joke, we have your money and you've got useless garbage" ? Maybe they instead try to blame Apple. Apple will point out that the CA knew this wouldn't work and suggest the subscriber seek a refund.

The subscriber demands a refund. The CA is now losing money and it is seeing negative reputational impact. Somebody threatens to sue. It is not a good day to be the CA.

At the subscriber's offices, an IT person has a brainwave and switches to a provider that isn't deliberately disobeying. The web site is back working. Champagne all round.

To achieve the desired robustness/ reliability the Web PKI is structured in a way that makes any individual Certificate Authority expendable. As a subscriber this means you should plan for your CA going away with at most a few days notice. Most people won't do that. Too bad, individually you're expendable too.

2 comments

Apple did actually make the limit a matter of their policy. Start date is September 1, technical enforcement comes 'later', but the requirement is going to be part of their policy. https://lists.cabforum.org/pipermail/public/2020-April/01494... Plus, it's not just Safari - it's the TLS stack in macOS/iOS etc. - Apple's KB article mentions nothing of Safari, but just like their enforcement of CT, it's basically OS-wide.
I don't think this is how it would (could?) play out. The CA would say, "Your Apple software is buggy, because nothing else has this weird limit. You can buy a 1 year cert from us to fix your issue. But because you already bought a 2 year cert, and Apple is being a jerk to you, here's an additional 1 year cert. Tell Apple they suck for making you jump through this hoop." And Apple would drone on about security or privacy or whatever being worth the customer now having to do more work. If nobody else played ball, it really would be just Apple annoying everybody. For reasons I can't yet fathom, the rest of the CAs and browsers seemed to chicken out instead of calling their bluff.