linux-kernel - Re: Trusted kernel patchset for Secure Boot lockdown

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Date:	Thu, 13 Mar 2014 21:31:55 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	"gnomes@...rguk.ukuu.org.uk" <gnomes@...rguk.ukuu.org.uk>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"jwboyer@...oraproject.org" <jwboyer@...oraproject.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: Re: Trusted kernel patchset for Secure Boot lockdown

On Thu, 2014-03-13 at 21:26 +0000, One Thousand Gnomes wrote:
> > On the other hand, disabling CAP_SYS_RAWIO *definitely* breaks expected
> > functionality - firmware loading and the fibmap ioctl are probably the
> > most obvious. And changing the use of CAP_SYS_RAWIO potentially breaks
> > userspace expectations, so we're kind of stuck there.
> 
> Actually I know how to describe the problem better.
> 
> Whitelist v Blacklist.
> 
> Going around adding extra cases for CAP_SYS_RAWIO is a fails insecure
> model. Going around adding CAP_SYS_RAWIO || CAP_SYS_RAWIO_SEC is a 'fails
> secure' case.

We've already been through this. We can't add new capabilities. It
breaks existing userspace.

-- 
Matthew Garrett <matthew.garrett@...ula.com>