Messages in this thread | | | Date | Thu, 1 Nov 2012 14:49:12 +0000 | From | Matthew Garrett <> | Subject | Re: [RFC] Second attempt at kernel secure boot support |
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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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