From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: [RFC] Second attempt at kernel secure boot support Date: Thu, 1 Nov 2012 14:49:12 +0000 Message-ID: <20121101144912.GA10269@srcf.ucam.org> References: <2548314.3caaFsMVg6@linux-lqwf.site> <50919EED.3020601@genband.com> <36538307.gzWq1oO7Kg@linux-lqwf.site> <1351760905.2391.19.camel@dabdike.int.hansenpartnership.com> <1351762703.2391.31.camel@dabdike.int.hansenpartnership.com> <1351763954.2391.37.camel@dabdike.int.hansenpartnership.com> <1351780935.2391.58.camel@dabdike.int.hansenpartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1351780935.2391.58.camel-sFMDBYUN5F8GjUHQrlYNx2Wm91YjaHnnhRte9Li2A+AAvxtiuMwx3w@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: James Bottomley Cc: Eric Paris , Jiri Kosina , Oliver Neukum , Chris Friesen , Alan Cox , Josh Boyer , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-efi@vger.kernel.org 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 | mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org