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Re: selinux breaks revisor

On Thu, 2008-01-24 at 17:11 +0100, Till Maas wrote:
> On Thu January 24 2008, Daniel J Walsh wrote:
> > machine.  For example if you are building a Fedora 7 livecd on a Fedora
> > 8 host machine, when the new selinux-policy package gets installed the
> > Fedora 7 policy will load and replace the Fedora 8 policy.  This will
> > invalidate any contexts that existed in Fedora 8 and not in Fedora 7
> > causing them to become unlabeled_t.  If this happens to a process, the
> > process usually goes wild.  We (SELinux engineering) is working on some
> > solutions, but don't have a good one now.
> >
> > Virtual machines?  Getting the chroot to run with a different kernel.
> > Faking out /selinux in chroot to do nothing on policy load?
> > Trying to stop Transitions?
> Imho it would be nice if it was possible to mark (label) a directory from the 
> outside to be the root of the chroot. Then everything within the chroot 
> directory should have a label for the outside selinux and a label for the 
> inside selinux. The selinus from the outside should allow everything within 
> the chroot to to whatever it wants within the chroot (this could be configure 
> within the policy), but should restrict access to everything outside the 
> chroot. The selinux within the chroot then should act like there is only the 
> inside policy and enforce it like it was the only one.

I think it would be a property of the chroot'd process and its
descendants, not of the directory, as processes operating non-chroot'd
may still access the contents of that directory and should still be
handled by the host policy.  So a per-task policy attribute that would
usually always refer to the host/global policy, but could be unshared
and then have a private policy loaded for it and its descendants.

The main problem is detecting and handling accesses that cross the
policy boundary (non-chroot'd process attempts to access file within the
directory, chroot'd process manages to break out of the chroot and
attempts to access file outside of chroot).

Stephen Smalley
National Security Agency

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