[chalst]

But you can know whether a CRL is valid, provided Apple's own CA hasn't been compromised. If Apple were to issue a complete CRL every 6 hours or so, then man-in-the-middle filtering won't work since clients can simply not trust any new signatures until they have seen the current CRL.

So the man-in-the-middle attack can keep the client ignorant of the contents of the CRL, but can't trick the client into believing a revoked certificate has not been revoked.

SSL is a red herring here, since we care about authenticity, not privacy.

[pyre]

Also...

  > provided Apple's own CA hasn't been compromised

We've been seeing this happen a lot lately, so that's a big assumption.

[pyre]

I was mostly commenting on the first paragraph in relation to the web, not specifically about Apple using certificates.