Over at Social Apples, a recent 4.2.1 jailbreaker noticed something disconcerting after firing up iBooks on his newly-liberated device. Many of his ebooks didn't work.
Since using the greenpois0n jailbreak, I have been unable to open some of my iBooks that I rightfully purchased from the iBook Store. I thought it was a problem with the downloaded books, so I re-downloaded them. That didn't work so I removed the iBooks from my iPhone and re-sync'd them from my computer… still no luck. Then I stumbled on a tweet from @comex tonight that really blew my mind.
"It seems that before opening a DRMed book, iBooks drops an improperly signed binary, tries to execute it, and if it works concludes that the device is jailbroken and refuses to open the book."
Seriously? I verified the issue by opening the broken books on my iPad. I haven't had a need to jailbreak the iPad so I've left it alone. Without much surprise and with no merriment, I was able to open the books just fine on the iPad.
Josh goes onto note that these types of "jailbreak checks" have been around in some form since iOS 4.0, though they don't end up crippling all jailbroken devices alike, and it's not clear even if everyone using the new greenpois0n jailbreak can expect the same crippled library. Let us know if you've found your own ebooks broken after jailbreaking 4.2.1. [Social Apples]