No need to implement portmap's SET (#2524)

* no need to implement set, I think

* need to bring this back for setup, but not as an api method

* fix test

* add documentation

Author: djeebus

packages/orchestrator/pkg/portmap/main.go

@@ -22,9 +22,7 @@ func newHandlers(ctx context.Context) *handlers {
 
 var _ portmap.PMAP_PROG_PMAP_VERS_handler = (*handlers)(nil)
 
-func (h *handlers) PMAPPROC_NULL() {}
-
-func (h *handlers) PMAPPROC_SET(mapping portmap.Mapping) portmap.Xbool {
+func (h *handlers) registerPort(mapping portmap.Mapping) {
 	h.lock.Lock()
 	defer h.lock.Unlock()
 
@@ -33,10 +31,18 @@ func (h *handlers) PMAPPROC_SET(mapping portmap.Mapping) portmap.Xbool {
 		Vers: mapping.Vers,
 		Prot: mapping.Prot,
 	}] = portmap.Uint32(mapping.Port)
+}
 
-	return true
+func (h *handlers) PMAPPROC_NULL() {}
+
+// PMAPPROC_SET is not implemented, so we return false. It needs to remain unimplemented, as
+// implementing it allows attackers to register and possibly redirect NFS traffic.
+func (h *handlers) PMAPPROC_SET(_ portmap.Mapping) portmap.Xbool {
+	return false
 }
 
+// PMAPPROC_UNSET is not implemented, so we return false. It serves no purpose, and implementing it
+// would allow attackers to remove port mappings, potentially disrupting services.
 func (h *handlers) PMAPPROC_UNSET(_ portmap.Mapping) portmap.Xbool {
 	return false
 }

packages/orchestrator/pkg/portmap/main_test.go

@@ -11,7 +11,7 @@ func TestPortmapRetrieval(t *testing.T) {
 	t.Parallel()
 
 	h := newHandlers(t.Context())
-	h.PMAPPROC_SET(portmap.Mapping{
+	h.registerPort(portmap.Mapping{
 		Prog: 100003,
 		Vers: 2,
 		Prot: 1,

packages/orchestrator/pkg/portmap/server.go

@@ -46,14 +46,14 @@ func NewPortMap(ctx context.Context) *Server {
 func (pm *Server) RegisterPort(ctx context.Context, port uint32) {
 	logger.L().Info(ctx, "registering port", zap.Uint32("port", port))
 
-	pm.h.PMAPPROC_SET(rfc1057.Mapping{
+	pm.h.registerPort(rfc1057.Mapping{
 		Prog: nfs.Nfs3Prog,
 		Vers: nfs.Nfs3Vers,
 		Prot: rfc1057.IPPROTO_TCP,
 		Port: port,
 	})
 
-	pm.h.PMAPPROC_SET(rfc1057.Mapping{
+	pm.h.registerPort(rfc1057.Mapping{
 		Prog: 100005, // mountd
 		Vers: nfs.Nfs3Vers,
 		Prot: rfc1057.IPPROTO_TCP,