security: require delete permission for HTTP rename overwrite

chfs-ng/internal/api/server.go

@@ -263,6 +263,30 @@ func (s *Server) newdir(w http.ResponseWriter, r *http.Request) {
 	s.logOp(r, fmt.Sprintf("created directory '%s'", p))
 	writeCreated(w)
 }
+func checkDeleteTree(store storage.Storage, a *auth.Account, root string) error {
+	info, err := store.Stat(root)
+	if err != nil {
+		return err
+	}
+	if !a.MaskFor(root).HasDelete() {
+		return fmt.Errorf("delete permission denied")
+	}
+	if !info.IsDir() {
+		return nil
+	}
+	items, err := store.List(root)
+	if err != nil {
+		return err
+	}
+	for _, item := range items {
+		p := path.Join(root, item.Name())
+		if err := checkDeleteTree(store, a, p); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (s *Server) rename(w http.ResponseWriter, r *http.Request) {
 	a := account(r, s)
 	rawOld, rawNew := r.FormValue("old"), r.FormValue("new")
@@ -276,6 +300,17 @@ func (s *Server) rename(w http.ResponseWriter, r *http.Request) {
 		writeJSONError(w, http.StatusForbidden, "has no privilege")
 		return
 	}
+	if old != neu {
+		if _, e := s.Store.Stat(neu); e == nil {
+			if e := checkDeleteTree(s.Store, a, neu); e != nil {
+				writeJSONError(w, http.StatusForbidden, "has no privilege")
+				return
+			}
+		} else if !os.IsNotExist(e) {
+			http.Error(w, e.Error(), 500)
+			return
+		}
+	}
 	if e := s.Store.Rename(old, neu); e != nil {
 		http.Error(w, e.Error(), 500)
 		return