[redhat-lspp] [RFC] [MLSXFRM 04/04] FOR REFERENCE ONLY: Add support to serefpolicy

[Venkat Yekkirala <vyekkirala trustedcs com>]

This patch will be submitted to the serefpolicy list later. It has been
included here just for reference.

This patch adds a polmatch avperm to arbitrate access between a flow/state
to a xfrm policy. It also defines MLS policy for association { sendto,
recvfrom, polmatch }.

NOTE: When an inbound packet is not using an IPSec SA, a check is performed
between the socket label and the unlabeled sid (SYSTEM_HIGH MLS label). For
MLS purposes however, the target of the check should be the MLS label taken
from the node sid (or secmark in the new secmark world). This would present
a severe performance overhead (to make a new sid based on the unlabeled sid
with the MLS taken from the node sid or secmark and then using this sid as
the target). While discussions are ongoing on fine tuning the networking
design in the context of secmark, IPSec, netlabel, etc., I have chosen to
currently make an exception for unlabeled_t SAs if TE policy allowed it. A
similar problem exists for the outbound case and it has been similarly
handled in the policy below (by making an exception for unlabeled_t).