tools/ocaml/xenstored: check privilege for XS_IS_DOMAIN_INTRODUCED

The Xenstore command XS_IS_DOMAIN_INTRODUCED should be possible for privileged
domains only (the only user in the tree is the xenpaging daemon).

This is part of XSA-115.

Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

tools/ocaml/xenstored/process.ml

@@ -166,7 +166,9 @@ let do_setperms con t _domains _cons data =
 let do_error _con _t _domains _cons _data =
 	raise Define.Unknown_operation
 
-let do_isintroduced _con _t domains _cons data =
+let do_isintroduced con _t domains _cons data =
+	if not (Connection.is_dom0 con)
+	then raise Define.Permission_denied;
 	let domid =
 		match (split None '\000' data) with
 		| domid :: _ -> int_of_string domid