SpigotCore_Main/src/de/steamwar/command/SWCommand.java

@@ -80,7 +80,9 @@ public abstract class SWCommand {
         if (!CommandSender.class.isAssignableFrom(parameters[0].getType())) return false;
         for (int i = 1; i < parameters.length; i++) {
             Parameter parameter = parameters[i];
+            StringConstraint stringConstraint = parameter.getAnnotation(StringConstraint.class);
             Class<?> clazz = parameter.getType();
+            if (stringConstraint != null && clazz != String.class) return false;
             if (parameter.isVarArgs() && i == parameters.length - 1) {
                 clazz = parameter.getType().getComponentType();
             }

SpigotCore_Main/src/de/steamwar/command/SWCommandUtils.java

@@ -26,10 +26,7 @@ import org.bukkit.entity.Player;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Parameter;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.UUID;
+import java.util.*;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 
@@ -91,8 +88,13 @@ class SWCommandUtils {
         arguments[0] = parameters[0].getType().cast(commandSender);
 
         for (int i = 1; i < parameters.length - (varArgs ? 1 : 0); i++) {
+            Parameter parameter = parameters[i];
             Class<?> clazz = parameters[i].getType();
             arguments[i] = mapper(clazz).apply(args[i - 1]);
+            StringConstraint stringConstraint = parameter.getAnnotation(StringConstraint.class);
+            if (stringConstraint != null && !Objects.equals(arguments[i], stringConstraint.constraint())) {
+                throw new SecurityException();
+            }
         }
 
         if (varArgs) {

SpigotCore_Main/src/de/steamwar/command/StringConstraint.java

@@ -0,0 +1,31 @@
+/*
+ * This file is a part of the SteamWar software.
+ *
+ * Copyright (C) 2020  SteamWar.de-Serverteam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.command;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.PARAMETER})
+public @interface StringConstraint {
+    String constraint();
+}