linux-kernel - Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]

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Date:	Wed, 12 Dec 2007 11:44:41 -0800 (PST)
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	David Howells <dhowells@...hat.com>, casey@...aufler-ca.com
Cc:	dhowells@...hat.com, Stephen Smalley <sds@...ho.nsa.gov>,
	Karl MacMillan <kmacmill@...hat.com>, viro@....linux.org.uk,
	hch@...radead.org, Trond.Myklebust@...app.com,
	linux-kernel@...r.kernel.org, selinux@...ho.nsa.gov,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]


--- David Howells <dhowells@...hat.com> wrote:

> Casey Schaufler <casey@...aufler-ca.com> wrote:
> 
> > What sort of authorization are you thinking of? I would expect
> > that to have been done by cachefileselinuxcontext (or
> > cachefilesspiffylsmcontext) up in userspace. If you're going to
> > rely on userspace applications for policy enforcement they need
> > to be good enough to count on after all.
> 
> It can't be done in userspace, otherwise someone using the cachefilesd
> interface can pass an arbitrary context up.

Yes, but I would expect that interface to be protected (owned by root,
mode 0400). If /dev/cachefiles has to be publicly accessable make it
a privileged ioctl.

> The security context has to be
> passed across the file descriptor attached to /dev/cachefiles along with the
> other configuration parameters as a text string.

I got that.

> This fd selects the
> particular cache context that a particular instance of a running daemon is
> using.

Yes, but forgive me being slow, I don't see the problem.


Casey Schaufler
casey@...aufler-ca.com
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