linux-kernel - Re: [PATCH 00/12] One more attempt at useful kernel lockdown

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Date:	Mon, 9 Sep 2013 15:52:48 -0400
From:	Josh Boyer <jwboyer@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	David Lang <david@...g.hm>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 00/12] One more attempt at useful kernel lockdown

On Mon, Sep 9, 2013 at 3:41 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 09/09/2013 12:01 PM, Valdis.Kletnieks@...edu wrote:
>> On Mon, 09 Sep 2013 11:25:38 -0700, David Lang said:
>>
>>> Given that we know that people want signed binaries without
>>> blocking kexec, you should have '1' just enforce module signing
>>> and '2' (or higher) implement a full lockdown including kexec.
>>
>>> Or, eliminate the -1  permanently insecure option and make this a
>>> bitmask, if someone wants to enable every possible lockdown, have
>>> them set it to "all 1's", define the bits only as you need them.
>>
>> This strikes me as much more workable than one big sledgehammer.
>>
>
> I.e. capabilities ;)

Circles.  All I see here are circles.

Having lived an entire release with a capabilities based mechanism for
this in Fedora, please no.

And if you are talking about non-POSIX capabilities as you mentioned
earlier, that seems to be no different than having securelevel being a
bitmask of, well, levels.  I don't have much opinion on securelevel
being a big hammer or a bitmask of finer grained things, but I do
think it's a more manageable way forward.  Calling the implementation
"capabilities" seems to just be unnecessarily confusing.

josh
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