Jailbreak your iPhone? iBookstore purchases may be unreadable
As hackers push to crack Apple's iOS security checks, Apple appears to be pushing back. One user recently discovered that, after applying the latest greenpois0n jailbreak code on an iPhone running iOS 4.2.1, Apple has built checks into the system that prevent iBooks from opening DRM-protected e-books on a jailbroken device. While this user described the checks as a "screw you" to jailbreakers, they are likely a concession to publishers concerned about piracy.
After jailbreaking an iOS device and attempting to open content purchased from the iBookstore, the blog Social Apples noted that users now receive the following error message: "There is a problem with the configuration of your iPhone. Please restore with iTunes and reinstall iBooks."
The process that handles verifying and decrypting FairPlay-protected content, fairplayd, is performing a number of checks before decrypting protected e-books. It tries to execute several small, specially crafted binaries—each one made to fail on a standard iOS install but likely to run on jailbroken devices. If these binaries can run—one is unsigned, for instance, while another is improperly signed—then fairplayd can assume the device is jailbroken and refuse to decrypt the content. That triggers iBooks to display its error message.
