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!
Adi
===
> 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
> longname
> password
> <user's password here>
> /bin/zsh
> username
> ---
> ... various other occurrences follow
>
>
> Grepping for context around "password" also shows up results, and grepping
> 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 swapped,
> though loginwindow seems likely to get swapped early since it is seldom
> 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 encryption
> fairly useless. It appears that the swapfiles are removed on shutdown or
> startup, though not wiped - pulling the power from a sleeping machine,
> 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 if
> they at least said "we're taking a look if it's an issue".
>
> Matt
Received on Jul 15 2004
Intro
