“The passcode is entangled with the device’s UID, so brute-force attempts must be performed on the device under attack. A large iteration count is used to make each attempt slower. The iteration count is calibrated so that one attempt takes approximately 80 milliseconds.”
This is still an argument for using a longer length code, however, since a simple 4-digit number would only take 800 seconds to brute force.
Well, actually it isn't surprising at all.
EDIT: It appears I was wrong, this was only in LA county.
They could order Apple to disclose signing keys so that the government can install spyware themselves. See http://en.wikipedia.org/wiki/Lavabit#Suspension_and_gag_orde... for a case where they have done something similar before.
It would have to be an OS update since applications don't have access to that stuff, even if signed with an apple key.
That said, it'd be kind of unsubtle, and they'd probably get caught.
iOS won't let even the most permissively configured, "unreviewed" app do things that apps aren't supposed to be able to do?
It's important to note however that the passcode is just 4 digits long by default, and could be bruteforced by Apple in milliseconds if they wanted to. So to say that "Apple cannot bypass your passcode" is misleading, as guessing it is absurdly easy.
http://www.slideshare.net/alexeytroshichev/icloud-keychain-3...