Re: NFS4 authentification / fsuid

[Kyle Moffett <mrmacman_g4@mac.com>]

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.

Cheers,
Kyle Moffett