Re: NFS4 authentification / fsuid

Kyle Moffett
2007-09-06T23:37:51Z

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