Re: [RFC] Virtualization steps

[Serge E. Hallyn]

Quoting Stephen Smalley (sds@xxxxxxxxxxxxx):
> 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.

Yes, my first response (which I cancelled) mentioned this as a possible
solution.

The global admin could assign certain max privileges to 'container_b'.
The admin in container_b could create container_b.root_t,
container_b.user_t, etc, which would be limited by the container_b
max perms.

Presumably the policy daemon, running in container 0, could accept input
from a socket from container 2, labeled appropriately automatically
ensuring that all types created by the policy in container 2 are
prefixed with container_b, and doing the obvious restrictions.

Or something like that :)

-serge
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