Security Experts:

Debug Setting in Mac OS X Lion Exposing Legacy Passwords

On Friday, security researcher David Emery reported the discovery of a problem within Mac OS X 10.7.3, which results in a user’s password being recorded to a log file in plain text.

Emery explained that a debug switch in the current release of Lion was activated sometime before its release, resulting in the user’s legacy Filevault password being written to a log file in plain text. This log will remain on the system for several weeks, and anyone with read access to the admin group can access them.

“This is worse than it seems, since the log in question can also be read by booting the machine into Firewire disk mode and reading it by opening the drive as a disk or by booting the new-with-LION recovery partition and using the available superuser shell to mount the main file system partition and read the file. This would allow someone to break into encrypted partitions on machines they did not have any idea of any login passwords for,” Emery added.

The fix and ultimate solution would be to switch to Filevault 2, but the catch is that users need to first understand what version of Filevault they’re using and make the effort to switch, in addition to resetting their passwords. If the patch rate observed shortly after Apple patched a Java flaw is any indication, the Filevault issue may be around for some time.

On the upside, the problem only applies to Mac users who updated their systems from Snow Leopard and kept the older Filevault setups, who then later upgraded to OS X 10.7.3.

Topher Kessler has written a blog post on CNET with details on how to check to see if you’re really impacted by the issue, and how to fix it.

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Steve Ragan is a security reporter and contributor for SecurityWeek. Prior to joining the journalism world in 2005, he spent 15 years as a freelance IT contractor focused on endpoint security and security training.