Re: [RFC] Virtualization steps

[Stephen Smalley <sds@tycho.nsa.gov>]

On Thu, 2006-03-30 at 08:32 -0600, Serge E. Hallyn wrote:
> Frankly I thought, and am still not unconvinced, that containers owned
> by someone other than the system owner would/should never want to load
> their own LSMs, so that this wasn't a problem.  Isolation, as Chris has
> mentioned, would be taken care of by the very nature of namespaces.
> 
> There are of course two alternatives...  First, we might want to allow the
> machine admin to insert per-container/per-namespace LSMs.    To support
> this case, we would need a way for the admin to tag a container some way
> identifying it as being subject to a particular set of security_ops.  
> 
> Second, we might want container admins to insert LSMs.  In addition to
> a straightforward way of tagging subjects/objects with their container,
> we'd need to implement at least permissions for "may insert global LSM",
> "may insert container LSM", and "may not insert any LSM."  This might be
> sufficient if we trust userspace to always create full containers.
> Otherwise we might want to support meta-policy along the lines of "may
> authorize ptrace and mount hooks only", or even "not subject to the
> global inode_permission hook, and may create its own."  (yuck)
> 
> But so much of this depends on how the namespaces/containers end up
> being implemented...

FWIW, SELinux now has a notion of a type hierarchy in its policy, so the
root admin can carve out a portion of the policy space and allow less
privileged admins to then define sub-types that are strictly constrained
by what was allowed to the parent type by the root admin.  This is
handled in userspace, with the policy mediation performed by a userspace
agent (daemon, policy management server), which then becomes the focal
point for all policy loading.

-- 
Stephen Smalley
National Security Agency

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