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Re: Plug-and-wipe and Secure Boot semantics
From: Greg KH <greg () kroah com>
Date: Tue, 18 Dec 2012 21:39:59 -0800

On Tue, Dec 18, 2012 at 03:52:50PM +0100, Florian Weimer wrote:
On 12/18/2012 03:41 PM, Greg KH wrote:
On Tue, Dec 18, 2012 at 01:46:47PM +0100, Florian Weimer wrote:
Some UEFI machines seem to boot from USB by default, without any
prompting, probably assuming that a signed boot loader cannot cause
any damage.

Specific model name(s) please?

Lenovo M72e 0896A9G

Thanks for that, I'll try to track one down, that's a very odd behavior,
but, in reading the spec, I can't see how it violates it at all.

This is a business-class Windows 8 machine which comes with a
Windows 8 logo sticker, so Secure Boot was enabled in the factory
(and my testing reflected that).  I'm not sure if the type number
encodes that—Lenovo surely offers essentially the same hardware with
Secure Boot disabled by default, so that customers can install
Windows 7 more easily.

Most signed Linux boot loaders only verify the kernel (and,
indirectly, code that's loaded into the kernel), but not the
initrd contents.

Given that there is only one public signed Linux boot loader, saying
"most" is a bit odd here :)

Uhm, aren't there a couple of them in circulation?

Not that I know of, all of the "public" ones are based on Matthew
Gerritt's code, do you know of another one that has made it through the
Microsoft signing process?

The Fedora 18 TC3 installer boots on the machine mentioned above, in
the factory default configuration.  Previous installer versions
showed a Secure Boot error message.  I've run into an installer bug,
though:
<https://bugzilla.redhat.com/show_bug.cgi?id=888232>

Previous versions of Fedora 18 betas didn't have a valid signed
bootloader to allow anything to be installed, are you sure it's all
properly built now?

Also, there is a bug in Matthew's signed shim code that fails on some
machines (like the one I have), so you might want to work on getting the
bugfix into your build/sign/distro creation process.

But, more on-topic, how does UEFI secure boot have anything to do with
this mailing list?

thanks,

greg k-h


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