On Thu, 2012-11-01 at 10:29 -0400, Eric Paris wrote:

On Thu, Nov 1, 2012 at 5:59 AM, James Bottomley
[off-list ref] wrote:

quoted

But that doesn't really help me: untrusted root is an oxymoron.

Imagine you run windows and you've never heard of Linux.  You like
that only windows kernels can boot on your box and not those mean
nasty hacked up malware kernels.  Now some attacker manages to take
over your box because you clicked on that executable for young models
in skimpy bathing suits.  That executable rewrote your bootloader to
launch a very small carefully crafted Linux environment.  This
environment does nothing but launch a perfectly valid signed Linux
kernel, which gets a Windows environment all ready to launch after
resume and goes to sleep.  Now you have to hit the power button twice
every time you turn on your computer, weird, but Windows comes up, and
secureboot is still on, so you must be safe!

So you're going back to the root exploit problem?  I thought that was
debunked a few emails ago in the thread?

Your attack vector isn't plausible because for the suspend attack to
work, the box actually has to be running Linux by default ... I think
the admin of that box might notice if it suddenly started running
windows ...

In this case we have a completely 'untrusted' root inside Linux.  From
the user PoV root and Linux are both malware.  Notice the EXACT same
attack would work launching rootkit'd Linux from Linux.  So don't
pretend not to care about Windows.  It's just that launching malware
Linux seems like a reason to get your key revoked.  We don't want
signed code which can be used as an attack vector on ourselves or on
others.

That make sense?

Not really, no.  A windows attack vector is a pointless abstraction
because we're talking about securing Linux and your vector requires a
Linux attack for the windows compromise ... let's try to keep on point
to how we're using this feature to secure Linux.

James