Zdziarski’s “Kill Switch” Discovery Not What It Seems

by Eric March on August 8, 2008 at 4:00 pm

You may have been following some rumours the last day or so about a supposed “back door” or “kill switch” through which Apple could disable apps via a list of blacklisted applications. It all started when inveterate hacker Johnathan Zdziarski, in his forensic combing through the iPhone 2.x firmware, discovered a file containing a link that pointed to “https://iphone-services.apple.com/clbl/unauthorizedApps” in the Location Services area, which Jon reasoned may be something the iPhone uses to “call home” periodically to retrieve the blacklisted apps in order to check its installed list to see if any are on it. Further experimentation revealed that he could provide his own list and could effectively prevent applications from gaining access to Location Services.

It was surmised by Jonathan, and thus picked up by the rest of the blogosphere and some newspapers, that Apple could gain access to one’s iPhone and summarily disable any application that it didn’t want you running by supplying the iPhone with a new blacklist containing the offending app.

Chilling stuff. As it turns out though, John Gruber of Daring Fireball seems to believe that this is actually for something more inoccuous. Specifically, Gruber has learned from “an informed source at Apple” that the “clbl” part of the URL stands for “Core Location Blacklist,” and it simply contains a list of applications that are to be explicitly denied access to the iPhone’s Core Location Services — not, as has been previously elevated to FUD status, to kill any app at all.

Gruber suggests that this makes sense, since Apple saddled the Core Location API with some fairly strict rules in the SDK, thus they would need a way to prevent applications that somehow both broke the rules and made it past Apple’s vetting process from continuing to gain access to it. It doesn’t seem that the blacklist is any more nefarious than that, so don’t go worrying that the black hats at Apple will be able to get all up in your iPhone and start nixing your stuff.

(Daring Fireball, via Engadget)

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