linux-kernel - Re: AppArmor Security Goal

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Date:	Sat, 10 Nov 2007 22:24:14 +0000
From:	"Dr. David Alan Gilbert" <linux@...blig.org>
To:	Crispin Cowan <crispin@...spincowan.com>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	LSM ML <linux-security-module@...r.kernel.org>,
	apparmor-dev <apparmor-dev@...ge.novell.com>
Subject: Re: AppArmor Security Goal

* Crispin Cowan (crispin@...spincowan.com) wrote:
> Dr. David Alan Gilbert wrote:
> > * Crispin Cowan (crispin@...spincowan.com) wrote:
> > <snip
> >>     * Manipulating AppArmor policy requires being both root privileged
> >>       and not being confined by AppArmor, thus there is explicitly no
> >>       capability for non-privileged users to change AppArmor policy.
> >>     
> > It's a pity that there is no way to do this; it would be nice to restrict
> > web browsers, document editors etc but allow them
> > to access the places you commonly store documents etc.
> >   
> I don't get the problem: if you want your web browser to be able to
> access where you commonly store your documents, then give it that
> permission. The above rule says that your web browser doesn't get to go
> change AppArmor policy on its own.

But can I as a non-privileged user say which directories I want it to
be able to access?

> I have serious doubts about the utility of restricting a text editor.
> You nominally want to be able to edit any file on the system, so
> confining it would be fairly meaningless.

Text editor probably true; but I'm thinking here more of OpenOffice
and the like; there have been plenty of document carried malware in the
past.

> > Similarly I'd like to be able to split applications so that
> > the 'preferences' editing facilities are done by separate
> > envrionments so that there is no way that a fault in parsing
> > external data could edit the config (e.g. change home page or
> > proxy in a browser or default document in an editor).
> >   
> AppArmor will let you do that; most of the work is in splitting the
> application. If you can get e.g. Firefox to use a separate process that
> it exec's for editing your preferences, then AppArmor can confine that
> helper app with a different policy than Firefox itself, including
> granting the helper write permission to the config directory.

Yes, and designing the app so that it's filenames are predictable;
firefox has a fun habit of using randomly named profile directories.

Dave
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    | Running GNU/Linux on Alpha,68K| Happy  \ 
\ gro.gilbert @ treblig.org | MIPS,x86,ARM,SPARC,PPC & HPPA | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/
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