flask/policy: xenstore stubdom policy

This adds the xenstore_t type to the example policy for use by a
xenstore stub domain; see the init-xenstore-domain tool for how this
type needs to be used.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>

tools/flask/policy/modules/modules.conf

@@ -33,6 +33,9 @@ nomigrate = on
 # Example device policy.  Also see policy/device_contexts.
 nic_dev = on
 
+# Xenstore stub domain (see init-xenstore-domain).
+xenstore = on
+
 # This allows any domain type to be created using the system_r role.  When it is
 # disabled, domains not using the default types (dom0_t, domU_t, dm_dom_t) must
 # use another role (such as vm_r from the vm_role module below).

tools/flask/policy/modules/xenstore.te

@@ -0,0 +1,24 @@
+################################################################################
+#
+# Xenstore stubdomain
+#
+################################################################################
+declare_singleton_domain(xenstore_t)
+create_domain(dom0_t, xenstore_t)
+manage_domain(dom0_t, xenstore_t)
+
+# Xenstore requires the global VIRQ for domain destroy operations
+allow dom0_t xenstore_t:domain set_virq_handler;
+# Current xenstore stubdom uses the hypervisor console, not "xl console"
+allow xenstore_t xen_t:xen writeconsole;
+# Xenstore queries domaininfo on all domains
+allow xenstore_t domain_type:domain getdomaininfo;
+
+# As a shortcut, the following 3 rules are used instead of adding a domain_comms
+# rule between xenstore_t and every domain type that talks to xenstore
+create_channel(xenstore_t, domain_type, xenstore_t_channel)
+allow event_type xenstore_t: event bind;
+allow xenstore_t domain_type:grant { map_read map_write unmap };
+
+# Xenstore is a utility domain, so it should use the system role
+role system_r types xenstore_t;