Subject: Re: NFS4 authentification / fsuid
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Kyle Moffett <mrmacman_g4@mac.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
       Satyam Sharma <satyam@infradead.org>,
       Jan Engelhardt <jengelh@computergmbh.de>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
In-Reply-To: <0D66E86D-8D97-45D7-9C2A-7AB5F42845B5@mac.com>
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	 <1188486240.6755.51.camel@heimdal.trondhjem.org>
	 <20070830214431.GF10808@fieldses.org>
	 <alpine.LFD.0.999.0709061333410.3781@enigma.security.iitk.ac.in>
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Date: Fri, 07 Sep 2007 01:35:14 +0200
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On Thu, 2007-09-06 at 19:30 -0400, Kyle Moffett wrote:
> On Sep 06, 2007, at 11:06:16, J. Bruce Fields wrote:
> > On Thu, Sep 06, 2007 at 01:44:05PM +0530, Satyam Sharma wrote:
> >> Like Trond said, there are very high number of ways in which  
> >> privileged userspace can compromise a running kernel if it really  
> >> wants to do that, root-is-God has always been *the* major problem  
> >> with Unix :-)
> >>
> >> The only _real_ way a kernel can lock itself completely against  
> >> malicious userspace involves trusted tamperproof hardware,
> >
> > The question of how to protect against someone with *physical*  
> > access certainly is more difficult, but surely that's a separate  
> > problem.
> 
> Actually, that's a fairly simple problem (barring disassembling the  
> system and attaching a hardware debugger).  You encrypt the root  
> filesystem and require a password to boot (See: LUKS).  Debian has  
> built-in support for installing onto fs-on-LVM-on-crypt-on-RAID, and  
> it works quite well on all the laptops I use regularly.  It's not  
> even much of a speed penalty; once you take the overhead of hitting a  
> 5400RPM laptop drive you can chew thousands of cycles of CPU without  
> anybody noticing (much).  Then all you have to do is burn a copy of  
> your /boot with bootloader onto some read-only media (like a  
> finalized CDROM/DVDROM) and you're set to go.

Disconnect battery, and watch boot password go 'poof!'.

Trond

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