linux-kernel - Re: [AppArmor 01/41] Pass struct vfsmount to the inode

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Message-ID: <20070529233041.GC24200@elf.ucw.cz>
Date:	Wed, 30 May 2007 01:30:41 +0200
From:	Pavel Machek <pavel@....cz>
To:	david@...g.hm
Cc:	Crispin Cowan <crispin@...ell.com>, Cliffe <cliffe@...et.net.au>,
	casey@...aufler-ca.com, Kyle Moffett <mrmacman_g4@....com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [AppArmor 01/41] Pass struct vfsmount to the inode_create LSM hook

Hi!

> >>>If we want "/etc/shadow" to be the only way to access the shadow file
> >>>we could label the data with "/etc/shadow". Any attempts to access
> >>>this data using a renamed file or link would be denied (attempts to
> >>>link or rename could also be denied).
> >>Eloquently put.
> >>
> >>AppArmor actually does something similar to this, by mediating all of
> >>the ways that you can make an alias to a file. These are:
> >...
> >>    * Hard links: AppArmor explicitly mediates permission to make a hard
> >
> >Unfortunately, aparmor is by design limited to subset of distro
> >(network daemons). Unfortunately, some other programs (passwd, vi)
> >routinely make hardlinks. So AA mediating hardlink is not enough, as
> >vi will happily hardlink /etc/shadow into /etc/.vi-shadow-1234.
> 
> but with the AA design of default deny this isn't a big problem unless you 
> specificly allow some network daemon to access /etc/.vi-shadow-1234

...or unless vi decides to hardlink into /tmp or something.

> no, this won't help you much against local users, but there are a _lot_ of 
> boxes out there with few, if any, local users who don't also have the root 
> password. AA helps the admin be safer when configuring netwrok daemons.

Hmm, I guess I'd love "it is useless on multiuser boxes" to become
standard part of AA advertising.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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