Tuesday, July 17, 2018

iOS Devices Can Be Blocked From Entering USB Restricted Mode

Oleg Afonin (via John Gruber):

On unmanaged devices, the new default behavior is to disable data connectivity of the Lightning connector after one hour since the device was last unlocked, or one hour since the device has been disconnected from a trusted USB accessory.


What we discovered is that iOS will reset the USB Restrictive Mode countdown timer even if one connects the iPhone to an untrusted USB accessory, one that has never been paired to the iPhone before (well, in fact the accessories do not require pairing at all).


Can Apple change it in future versions of iOS? To us, it seems highly unlikely simply because of the humongous amount of MFi devices that aren’t designed to support such a change.

Previously: Cellebrite Can Now Unlock Recent iPhones, GrayKey iPhone Unlocker.

Update (2018-07-24): See also: Bruce Schneier.

Update (2018-08-07): Josh Centers:

If USB Restricted Mode isn’t causing you any trouble, leave it on. Although it doesn’t offer complete protection against an alert attacker who can get access to your device quickly, it’s not worthless. Once your device has been locked for more than 60 minutes, nothing we know of can crack it.

If unlock alerts are nagging you, or if your device fails to charge because you didn’t unlock it, the easiest solution is to turn USB Restricted Mode off. Just go into Settings > Touch/Face ID & Passcode and enable USB Accessories.

2 Comments RSS · Twitter

The atricle on AppleInsider is incorrect. It seems they did not test - in fact, DP4 works exactly the same as previous betas, and any accessory still prevents USB restricted mode from activation.

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