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Apple makes a hash of password security (again)

Shadow boxing

Apple has dropped a couple of monumental password security clangers with the release on OS X Lion, according to security blogger Patrick Dunstan.

Dunstan, who posted an important piece on cracking Mac OS X passwords a couple of years ago, decided to revisit the subject with the release of OS X Lion (version 10.7).

He discovered Apple's developers had made user security worse in two important ways: firstly, it's possible to change the password of the current user without needing to know the original password, as Dunstan explains.

"It appears Directory Services in Lion no longer requires authentication when requesting a password change for the current user," he writes. "So, in order to change the password of the currently logged in user, simply use: $ dscl localhost -passwd /Search/Users/bob."

And that isn't the only backward step. Previously only a user with root (admin) privileges to a machine was able to get at the password hashes for other users, which are held in so-called "shadow files". With OS X Lion this restriction is easily circumvented.

"It appears in the redesign of OS X Lion's authentication scheme a critical step has been overlooked," Dunstan explains. "Whilst non-root users are unable to access the shadow files directly, Lion actually provides non-root users the ability to still view password hash data. This is accomplished by extracting the data straight from Directory Services."

"All users on the system, regardless of privilege, have the ability to access the ShadowHashData attribute from any other user's profile," he adds.

None of the major brute force crackers support OS X Lion hashes because the OS was only released in late July. Dunstan has created a python script to do the job, which is intended for password auditing. The password security foibles discovered by Dunstan raise further questions about the overall security of Mac OS X Lion, already highlighted by earlier LDAP password security weaknesses.

Dunstan's latest research is explained in greater depth in a post on his Defence in Depth blog here. ®

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