FOR REFERENCE ONLY: MLSXFRM: Add support to serefpolicy

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

This patch adds a polmatch avperm to arbitrate flow/state's access 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). Pending reconciliation of the netlabel, ipsec and iptables contexts, 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).

@@ -671,4 +671,19 @@

# these access vectors have no MLS restrictions
# association *

+mlsconstrain association { recvfrom }
+ ((( l1 dom l2 ) and ( l1 domby h2 )) or

+         (( t1 == mlsnetreadtoclr ) and ( h1 dom l2 )) or
+         ( t1 == mlsnetread ) or
+         ( t2 == unlabeled_t ));

+
+mlsconstrain association { sendto }
+ ((( l1 dom l2 ) and ( l1 domby h2 )) or
+ ( t2 == unlabeled_t ));
+
+mlsconstrain association { polmatch }
+ ((( l1 dom l2 ) and ( h1 domby h2 )) or
+ ( t2 == unlabeled_t ));
+
+
') dnl end enable_mls

@@ -602,6 +602,7 @@
       sendto
       recvfrom
       setcontext
+       polmatch

}

# Updated Netlink class for KOBJECT_UEVENT family.

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