netdev - Re: [RFC PATCH v1 1/2] lsm: Add hooks to the TUN driver

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Date:	Thu, 6 Aug 2009 10:24:54 -0400
From:	Paul Moore <paul.moore@...com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	eparis@...hat.com, netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov
Subject: Re: [RFC PATCH v1 1/2] lsm: Add hooks to the TUN driver

On Wednesday 05 August 2009 10:15:58 pm Serge E. Hallyn wrote:
> Quoting Paul Moore (paul.moore@...com):
> > On Wednesday 05 August 2009 10:13:50 am Serge E. Hallyn wrote:
> > > Quoting Paul Moore (paul.moore@...com):
> >
> > [NOTE: my email has been out all day due to some mysterious FS issue so
> > my apologies for not replying sooner]
> >
> > ...
> >
> > > The checks before and after this patch are not equivalent.  Post-patch,
> > > one must always have CAP_NET_ADMIN to do the attach, whereas pre-patch
> > > you only needed those if current_cred() did not own the tun device.  Is
> > > that intentional?
> >
> > Nope, just a goof on my part; I misread the booleans and haven't fully
> > tested the patch yet so it slipped out, thanks for catching it.  This
> > brings up a good point, would we rather move the TUN owner/group checks
> > into the cap_tun_* functions or move the capable() call back into the TUN
> > driver?  The answer wasn't clear to me when I was looking at the code
> > before and the uniqueness of the TUN driver doesn't help much in this
> > regard.
>
> I see the question being asked as:  Does this device belong to
> the caller and, if not, is the caller privileged to act
> anyway?'  So I think the capable call should be moved back
> into the tun driver, followed by a separate security_tun_dev_attach()
> check, since that is a separate, restrictive question.

Works for me, I'll make the change.

BTW, the main reason for posting the patches in such an early state was to 
solicit feedback on the location and types of hooks added; I've read lots of 
good feedback but nothing regarding the fundamental aspects of the hooks ... 
any comments before I push out v2?

-- 
paul moore
linux @ hp

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