Aussie Researcher Cracks OS X Lion Passwords

daria42 writes "Thought your Mac was secure running Apple's latest operating system? Think again. Turns out that in some respects Lion is actually less secure than previous version of Mac OS X, due to some permission-tweaking by Apple that has opened up a way for an attacker to crack your password on your Lion box. The flaw was discovered by an Australian researcher who has previously published a guide to cracking Mac OS X passwords. Sounds like Apple had better get a patch out for this."

Extremely Serious

[Manip]

I was expecting to read one of the normal fear-mongering stories that we often see on /. (e.g. "Drop Box sends passwords in plain text!!") but actually this is one of the most serious OS level holes I've seen in years. Not only can you retrieve the password for any user on the system but you can also reset their password without having to know what it was.

People have posted "they're still hashes so you still have to break them" which is of course true, but if you keep reading down he shows you how to reset the other user's password without ever having to know them.

Re:So not serious

[boristhespider]

You can change the root password on a Mac box without ANY credentials, provided you have physical access, Seems we have forgotten this while everyone is fear-mongering about what someone can do over the 'net.

Sorry for the sarcasm, but basically once someone has physical access to your computer you're basically boned unless you've encrypted your drive. It's Macs I know best, and it's trivial: boot to single user mode (command+S at start), mount in the file system as read/write (it even gives onscreen instructions for doing this) and then change the root password. I imagine something very similar can be done in Linux if there's an easy way to get it into single-user mode. Besides, on any machine to which you have physical access you can always boot a live distro and at the very least access the hashes if not easily take full control of the system.

Re:Not good, but not a panic situation

[jamesh]

The SAM file on Windows is impossible to retrieve while the Windows kernel is running. The kernel has an exclusive read/write lock on the file and any attempt to access it will be denied. It is possible to read an NTFS file-system outside of the OS even while the OS is running but we're talking about deep-file system inspection.

You meant any attempt by a user without admin privileges of course. VSS solved the backup-open-files problems a long time ago.

Interesting contrast I notice here

[metalgamer84]

Its interesting how when OSX has a security hole, everyone downplays it as "not that serious, no big deal". In contrast, if this same issue happened with XP/Vista/7, then the entire /. crowd would be jumping on the bandwagon of Microsoft bashing, "OMG another MS security hole! See people, Windows is crap!". Its funny how people will defend their preference and bash their competitors, even though the root issue can be the same for both. Anyhoo, just an observation.

Linux and Windows are just as bad.

[CapuchinSeven]

It's trivial to break the password on a Windows machine, in fact a hell of a lot easier on a Windows machine, if you have physical access. I'll happily do it, and have done it, in about 10 seconds with a boot USB or CD if the machine so too old for USB. A friend assures me a Linux box isn't that much harder. I use Linux, OSX and Windows in one form or another for my given needs but I feel that the REAL issue here shouldn't be "it's easier to do this on Windows, it's all anti-Apple FUD", but rather "we shouldn't be fanboys to any company/brand/make/type, there is no excuse for bad QA and security auditing in any OS". Ultimately though, physical access is the death of any OS.

Re:Linux and Windows are just as bad.

[Anonymous Coward]

I quote you.
It is interesting, though, that not all of us succeed in changing current user's password with dscl localhost -passwd /Search/Users/. I tested it on two Lion installs, and it did not work (well it actually asked for current password, as it should do). At the same time, dscl localhost -read /Search/Users/ | grep ShadowHashData returns 0 bytes, on build 11C62.
This somehow makes the anti-Apple FUD theory a lil bit stronger, IMHO. Before blindly quoting what people writes on their blog, sometime doing some first-person (easy) test can be a good idea.

Re:Not really cracking the passwords.

[slackergod]

Actually, the fact that OSX uses SHA512 makes it easy to crack the password (compared to the alternatives).

OSX uses SHA512(salt+password) to generate it's hashes. SHA2 was specifically designed to be highly parallelizable and fast on modern processors, which means brute force attacks are going to proceed very quickly. And as time goes on, and average processor speed increases, that amount of time per cpu (and per $) keeps dropping.

There are four modern password hashing schemes worthy of note: SHA512-Crypt (this is NOT simply SHA512), BCrypt, PBKDF2, and SCrypt.
All of these schemes use a variable number of rounds of their underlying cryptographic operation. This allows the algorithm to stay the same, but the cpu-cost to be increased per hash as computers get faster, or if a user is particularly paranoid and wants to make it take longer to crack.

Many of them (such as PBKDF2) even have properties that make them resistant to preimage attacks on the underlying hash function.

Finally, SCrypt has the unique property of being "memory hard"... it's rounds don't just require a certain amount of time, but a certain amount of memory*time. This makes parallelizing the attack much more costly, as each CPU has to get it's own dedicated amount of memory for the attack.

All of the above are so much tougher to brute force, that the cost of OSX's hash scheme is barely worth notice by comparison. I'm not sure why OSX is using what it is... Linux uses SHA512-Crypt, BSD uses BCrypt, WPA2 and many other things use PBKDF2... all would have been better choices.