linux-kernel - Re: NFS4 authentification / fsuid

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Message-Id: <1189121714.6672.38.camel@heimdal.trondhjem.org>
Date:	Fri, 07 Sep 2007 01:35:14 +0200
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Kyle Moffett <mrmacman_g4@....com>
Cc:	"J. Bruce Fields" <bfields@...ldses.org>,
	Satyam Sharma <satyam@...radead.org>,
	Jan Engelhardt <jengelh@...putergmbh.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: NFS4 authentification / fsuid

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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