Mac OS X Lion password-changing flaw uncovered

A flaw in Apple's new OS lets those with access to a Mac running Lion change passwords without knowing the user's login details, a researcher has claimed.

In previous versions of the Apple OS, users wanting to change passwords had to enter their login information before making alterations.

Why crack hashes when you can just change the password directly?

Now that step is not needed, thanks to insecure permissions in the Mac OS X Lion's local directory service, researcher Patrick Dunstan said, writing on the Defense in Depth blog.

"Why crack hashes when you can just change the password directly?" Dunstan said. "It appears Directory Services in Lion no longer requires authentication when requesting a password change for the current user."

Dunstan also claimed it was possible to access other users' password hashes and therefore steal their login information.

In previous versions of Mac OS X, only those with root access were allowed to view so-called shadow files, which contain hashes and salts used to encrypt passwords.

Although non-root users cannot access the shadow file directly, they can still gain access to information in it by extracting data from the directory services on the OS. All that needs to be done is type in the right command into Terminal to get that information, the researcher claimed.

"The interesting thing about this? Root privileges are not required," Dunstan added. "All users on the system, regardless of privilege, have the ability to access the ShadowHashData attribute from any other user's profile."

A brute force attack could be used to crack passwords once the hash and salt are acquired.

Comments on the blog showed some claiming to have exploited the flaw successfully, whilst others were unable to do so.

At the time of publication, Apple had not responded to a request for comment on the alleged vulnerability.