Re: NFS4 authentification / fsuid

Trond Myklebust
2007-09-06T23:35:36Z

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