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SubjectRe: [RFC] Second attempt at kernel secure boot support
On Thu, Nov 01, 2012 at 02:42:15PM +0000, James Bottomley wrote:
> On Thu, 2012-11-01 at 10:29 -0400, Eric Paris wrote:
> > 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?

The entire point of this feature is that it's no longer possible to turn
a privileged user exploit into a full system exploit. Gaining admin
access on Windows 8 doesn't permit you to install a persistent backdoor,
unless there's some way to circumvent that. Which there is, if you can
drop a small Linux distribution onto the ESP and use a signed, trusted
bootloader to boot a signed, trusted kernel that then resumes from an
unsigned, untrusted hibernate image. So we have to ensure that that's
impossible.

--
Matthew Garrett | mjg59@srcf.ucam.org


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