linux-kernel - Re: [PATCH] x86: Lock down MSR writing in secure boot

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Message-ID: <1360781490.18083.45.camel@x230.lan>
Date:	Wed, 13 Feb 2013 18:51:30 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Casey Schaufler <casey@...aufler-ca.com>,
	Borislav Petkov <bp@...en8.de>,
	Kees Cook <keescook@...omium.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot

On Wed, 2013-02-13 at 10:44 -0800, H. Peter Anvin wrote:

> So people have piggybacked complete inappropriate junk onto 
> CAP_SYS_RAWIO.  Great.  What the hell do we do now?  We can't break 
> apart CAP_SYS_RAWIO because we don't have hierarchical capabilities.

Yeah. Like I said, it's approximately useless.

> We thus have a bunch of unpalatable choices, **all of which are wrong**.
> 
> This, incidentally, is *exactly* the reason I object to 
> CAP_COMPROMISE_KERNEL as well... it describes a usage model, not a resource.

Like I said, I'm not wed to a capability-based model. However, it does
seem marginally more attractive than sprinkling if (!secure_boot) all
over the place. If anyone has alternatives, this would be a great time
to raise them.

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