linux-kernel - Re: [PATCH 3/6] secmark: export binary yes/no rather than kernel internal secid

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Date:	Mon, 27 Sep 2010 14:29:16 -0400
From:	Paul Moore <paul.moore@...com>
To:	Eric Paris <eparis@...hat.com>
Cc:	James Morris <jmorris@...ei.org>, linux-kernel@...r.kernel.org,
	selinux@...ho.nsa.gov, netfilter-devel@...r.kernel.org,
	sds@...ho.nsa.gov, jengelh@...ozas.de, casey@...aufler-ca.com,
	linux-security-module@...r.kernel.org, netfilter@...r.kernel.org,
	mr.dash.four@...glemail.com
Subject: Re: [PATCH 3/6] secmark: export binary yes/no rather than kernel
 internal secid

On Mon, 2010-09-27 at 13:01 -0400, Eric Paris wrote:
> On Mon, 2010-09-27 at 10:50 +1000, James Morris wrote:
> > On Fri, 24 Sep 2010, Eric Paris wrote:
> 
> > For the reasons above, I think the secctx string needs to be exported in 
> > addition to this rather than instead of.
> 
> I won't argue, I don't agree with your reasoning, but I'm not opposed to
> this result.  We have 3 competing suggestions:
> 
> Jan suggested we:
> completely eliminate secmark from procfs+netlink and only export secctx
> in netlink.
> 
> Eric suggested we:
> completely eliminate secmark from procfs+netlink and then export secctx
> in procfs+netlink
> 
> sounds like James suggested we:
> continue to export meaningless and confusing secmark from procfs+netlink
> and then export secctx in procfs+netlink as well.
> 
> I'm going to implement James' idea and resend the patch series.  Any
> strong objections?

I apologize for not getting a chance to look at these patches sooner.
In general they look fine to me and my only real concern was addressed
by Pablo already (breaking userspace due to #define changes).

As far as exporting the 32bit secid/secmark to userspace, I think that
is a mistake.  James correctly points out that it does map to a LSM
specific value, e.g. SELinux and Smack security labels, but I don't
think he makes it clear that in the two LSMs that currently use secids
the mapping between the secid and the secctx is not constant; the secids
are transient values that will change with each boot in a manner that
userspace can not predict.  For this reason, I think exporting the
secids is only going to cause users/admins grief, whereas exporting the
associated secctx should be a much more stable value and is likely what
the user/admin is expecting anyway.

-- 
paul moore
linux @ hp

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