Re: Mac OS X stores login/Keychain/FileVault passwords on disk Jul 16 2004 02:51PM
johnny ihackstuff com

The issue of getting into AES128 encrypted disk images is easy to

unravel with this swapfile problem.

We'll start by grabbing the volume name of an AES128 encrypted disk

image file. Assuming the image name is test1.dmg, try:

root# strings -8 /var/vm/swapfile* | grep -B1 test1.dmg | grep



Armed with the volume name, we can grab the file listing of that

(supposedly protected) AES128 encrypted disk image.  Since our

volume name is 'SECRET'. Try:

root# strings -8 /var/vm/swapfile* | grep "<string>/Volumes/SECRET"







To REALLY get at those (supposedly protected) files, we could use the

password. It's easy to grab it even if it's not in the keychain:

root# strings -8 /var/vm/swapfile* | grep -B1 "/System/Library/


[... snip ... ]




[... snip ... ]

The only chore may be figuring out which password goes with which

disk image. And that's not nearly the chore of popping AES128




johnny (at) ihackstuff (dot) com [email concealed]


From: Adi Kriegisch <adi (at) cg.tuwien.ac (dot) at [email concealed]>

To: bugtraq (at) securityfocus (dot) com [email concealed]

Subject: Re: Mac OS X stores login/Keychain/FileVault passwords on


Sent: Monday, July 12, 2004 9:05 AM

The swapfiles are deleted on startup -- this means even a clean

shutdown by

user leaves the passwords on disk.

So if you loose your powerbook someone might boot it in "target disk

mode" and

will be able to get your password!





It seems that Mac OS X (10.3.4 tested) doesn't bother clearing memory

containing sensitive data, or using mlock() to avoid swapping.

A quick grep of the swapfiles will show up various morsels:

rez:~> sudo strings -8 /var/vm/swapfile0 |grep -A 4 -i longname



<user's password here>




... various other occurrences follow

Grepping for context around "password" also shows up results, and


for portions of a Keychain password (differing from the login password)

will also get results. It appears that loginwindow is one of the apps

involved, I haven't investigated what else is involved. The amount of

memory and usage patterns of the machine will affect what gets


though loginwindow seems likely to get swapped early since it is


used after login.

Obviously this is only of interest if an attacker has root (or physical)

access to a machine, however it does make FileVault or Keychain


fairly useless. It appears that the swapfiles are removed on shutdown


startup, though not wiped - pulling the power from a sleeping


and/or booting from CD, would quite easily retrieve the password(s).

Reported to Apple on 21 June, I haven't had any response. It'd be nice


they at least said "we're taking a look if it's an issue".


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