Changes in iOS 7 Security Make Kernel More Vulnerable to Attack [iOS Blog]

A security researcher claims changes Apple made to tighten its kernel security system in iOS 7 instead weakened the system, making it less secure than its iOS 6 counterpart. (Via CNET and ThreatPost) Azimuth Security researcher Tarjei Mandt discovered the flaw and presented his findings last week at CanSecWest.

The security flaw involves the random number generator Apple uses to secure its kernel. In iOS 6, the number generator that encrypted the kernel derived its values in part from the CPU clock counter. Because it was based on time, the encryption was only marginally secure as the output values were predictable, especially when examining successive numbers.

Apple was aware of the limitations in iOS 6 and attempted to tighten security in iOS 7 by changing the random number generator to a linear congruential generator, which is more susceptible to brute force attacks.

The problem with the new generator in iOS 7 is that it uses a linear recursion algorithm, Mandt said, which has „more correlation“ between the values it generates. That makes them easier to extrapolate and guess, he said.

This flaw potentially allows a malicious hacker to gain kernel-level access to an iOS device via an unpatched vulnerability. The kernel is the base part of the iOS operating system and controls low-level functions such as security and resource allocation.

Apple approached Mandt about his findings and asked for his CanSecWest slide presentation.




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Second Lock Screen Bypass in iOS 6.1 Documented [iOS Blog]

A second iOS 6.1 bug has been discovered that gives access to contacts, photos and more. The vulnerability uses a similar method as the one disclosed previously, though it apparently gives access to more user data when the phone is plugged into a computer.

It was originally posted on the Full Disclosure mailing list. Kaspersky’s Threatpost:

Similar to the iPhone’s passcode vulnerability, the exploit involves manipulating the phone’s screenshot function, its emergency call function and its power button. Users can make an emergency call (911 for example) on the phone and then cancel it while toggling the power on and off to get temporary access to the phone. A video posted by the group shows a user flipping through the phone’s voicemail list and contacts list while holding down the power button. From there an attacker could get the phone’s screen to turn black before it can be connected to a computer via a USB cord. The device’s photos, contacts and more “will be available directly from the device hard drive without the pin to access,” according to the advisory.

Apple was expected to fix the lock screen bug in iOS 6.1.2, but that small release fixed a different bug. Instead, it appears a fix for at least one of the lock screen vulnerabilities will be coming in iOS 6.1.3, currently in the hands of developers.


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