linux-kernel - Re: [PATCH v14 3/6] LSM: Explicit individual LSM associations

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Date:	Thu, 01 Aug 2013 14:35:08 -0400
From:	Paul Moore <paul@...l-moore.com>
To:	Casey Schaufler <casey@...aufler-ca.com>
Cc:	LKLM <linux-kernel@...r.kernel.org>,
	LSM <linux-security-module@...r.kernel.org>,
	SE Linux <selinux@...ho.nsa.gov>,
	James Morris <jmorris@...ei.org>,
	John Johansen <john.johansen@...onical.com>,
	Eric Paris <eparis@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v14 3/6] LSM: Explicit individual LSM associations

On Wednesday, July 31, 2013 02:21:54 PM Casey Schaufler wrote:
> On 7/31/2013 12:39 PM, Paul Moore wrote:
> > On Wednesday, July 31, 2013 09:22:23 AM Casey Schaufler wrote:
> >> On 7/30/2013 3:08 PM, Paul Moore wrote:
> >>> On Thursday, July 25, 2013 11:32:11 AM Casey Schaufler wrote:
> >>>> Subject: [PATCH v14 3/6] LSM: Explicit individual LSM associations
> >>>> 
> >>>> Expand the /proc/.../attr interface set to help include
> >>>> LSM specific entries as well as the traditional shared
> >>>> "current", "prev" and "exec" entries. Each LSM that uses
> >>>> one of the traditional interfaces gets it's own interface
> >>>> prefixed with the LSM name for the ones it cares about.
> >>>> Thus, we have "smack.current", "selinux.current" and
> >>>> "apparmor.current" in addition to "current".
> >>>> 
> >>>> Add two new interfaces under /sys/kernel/security.
> >>>> The lsm interface displays the comma seperated list of
> >>>> active LSMs. The present interface displays the name
> >>>> of the LSM providing the traditional /proc/.../attr
> >>>> interfaces. User space code should no longer have to
> >>>> grub around in odd places to determine what LSM is
> >>>> being used and thus what data is available to it.
> >>>> 
> >>>> Introduce feature specific security operation vectors
> >>>> for NetLabel, XFRM, secmark and presentation in the
> >>>> traditional /proc/.../attr interfaces. This allows
> >>>> proper handling of secids.
> >>> 
> >>> Maybe I missed something, can you elaborate on this, perhaps even
> >>> provide an example for us simple minded folk?
> >> 
> >> There are a set of facilities that (currently, at least)
> >> can't be shared by multiple LSMs ...
> > 
> > I should have been more specific.
> > 
> > Thanks for the explanation, but that I understand the problems of stacking
> > LSM/secids, we've had that conversation a few times now.  The explanation
> > I was hoping for had to do with this sentence:
> >
> >  "Introduce feature specific security operation vectors for
> >   NetLabel, XFRM, secmark and presentation in the traditional
> >   /proc/.../attr interfaces."
> > 
> > Can you explain this a bit more?  When I looked at the patch - and maybe
> > I'm missing something - I didn't see anything in /proc that dealt with
> > NetLabel, XFRM, and/or Secmark.
> 
> Just so. I have failed to communicate clearly.
> 
>   "Each feature that requires support by a single, selected LSM
>    is identified by a global pointer to that LSM's security_operations
>    structure."
> 
> NetLabel, XFRM and secmark are networking interfaces that can
> send the security information from a single LSM along with the
> packets of data.
> 
> /proc/.../attr/current and SO_PEERSEC are interfaces that could
> send information from multiple LSMs, but in most cases you have
> to choose one LSM to placate your user space tools.
> 
> In all of these cases it is necessary to identify the LSM to use.
> Even though the end use is quite different the mechanism to support
> the identification is the same.

Okay, so if I understand everything correctly, there are no new entries in 
/proc relating specifically to NetLabel, XFRM, or Secmark; although there are 
new LSM specific entries for the general /proc entries that exist now.  Yes?

-- 
paul moore
www.paul-moore.com

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