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SubjectRe: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]
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On Mon, 2008-01-14 at 14:01 +0000, David Howells wrote:
> Stephen Smalley <sds@tycho.nsa.gov> wrote:
>
> > > avc_has_perm(daemon_tsec->sid, nominated_sid,
> > > SECCLASS_CACHE, CACHE__USE_AS_OVERRIDE, NULL);
> > >
> > > And I assume this doesn't care if one, the other or both of the two SIDs
> > > mentioned are of SECCLASS_PROCESS rather than of SECCLASS_CACHE.
> >
> > Right, the latter is reasonable.
>
> Okay... It looks like I want four security operations/hooks for cachefiles:
>
> (1) Check that a daemon can nominate a secid for use by the kernel to override
> the process subjective secid.
>
> (2) Set the secid mentioned in (1).
>
> (3) Check that the kernel may create files as a particular secid (this could
> be specified indirectly by specifying an inode, which would hide the secid
> inside the LSM).

I don't think this check is on the kernel per se but rather the ability
of the daemon to nominate a secid for use on files created later by the
kernel module.

> (4) Set the fscreate secid mentioned in (3).
>
> Now, it's possible to condense (1) and (2) into a single op, and condense (3)
> and (4) into a single op. That, however, might make the ops unusable by nfsd,
> which may well want to bypass the checks or do them elsewhere.
>
> Any thoughts?

I think it is fine to combine them.

--
Stephen Smalley
National Security Agency



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