Date: Wed, 23 Feb 2011 08:33:48 +0100 From: Sebastian Krahmer <krahmer@...e.de> To: oss-security@...ts.openwall.com Subject: Re: Physical access vulnerabilities and auto-mounting Hi, Unfortunally I think nobody would care. As nobody cared that you actually do not need physical access. Via udisks DBUS service you can load any LKM via dbus-send --system --print-reply --dest=org.freedesktop.UDisks \ /org/freedesktop/UDisks/devices/sr0 \ org.freedesktop.UDisks.Device.FilesystemMount \ string:'LKM' array:string:'' I reported that several months ago to upstream but it was frozen to more or less a non-issue. Indeed nobody agreed that this is an issue to fix. Sebastian On Tue, Feb 22, 2011 at 11:17:54PM -0500, Dan Rosenberg wrote: > I originally started writing this as a response to the recent CVE > requests for issues in partition handling, but thought it might be a > useful discussion on its own. I was wondering if there are any > clear-cut policies on issues involving physical access, since these > can be very difficult in terms of assigning blame. > > For example, many Linux distributions will auto-mount filesystems on > removable storage, often going so far as to load corresponding kernel > modules for filesystems that aren't compiled in or don't already have > an LKM loaded. Sometimes, this will happen even if the screen is > locked. > > Incidentally, many Linux filesystem implementations don't have > especially robust error handling for failures during attempts to mount > corrupt filesystems. As an example, I have a deliberately corrupted > btrfs filesystem that triggers a BUG() if you attempt to mount it. I > formatted a USB stick with this filesystem, so now I have a USB stick > that will panic the kernels of distributions that support > auto-mounting, in some cases even when the screen is locked. > > Should this be considered a vulnerability? Probably. But what should > be fixed? Should auto-mounting be disabled entirely? Is it no longer > a vulnerability if auto-mounting is disabled only when the screen is > locked? Should all filesystems have graceful error handling for every > possible edge case that can occur when dealing with corruption? > > I'd be interested to hear opinions on this. And depending on how the > discussion goes, I'd be happy to provide more details on specific > cases, such as the btrfs example. > > -Dan -- ~ ~ perl self.pl ~ $_='print"\$_=\47$_\47;eval"';eval ~ krahmer@...e.de - SuSE Security Team ~ SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nuernberg)
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