Add initial AccessWidener

2026-06-11 12:22:44 +02:00
parent e176b3bca8
commit 786257ad0e
15 changed files with 979 additions and 6 deletions
@@ -0,0 +1,67 @@
+/*
+ *   This file is a part of the SteamWar software.
+ *
+ *   Copyright (C) 2026 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;
+
+import java.lang.instrument.Instrumentation;
+import java.util.logging.Logger;
+
+/**
+ * Java agent entry point.
+ *
+ * Can be used two ways:
+ *   1. At JVM startup:  java -javaagent:paper-access-widener-agent.jar -jar server.jar
+ *   2. Late attach:     from inside a Paper plugin via the Attach API
+ *
+ * On attach the agent:
+ *   1. Scans all existing plugin ClassLoaders for "plugin.accesswidener" resources
+ *   2. Registers a ClassFileTransformer that:
+ *        a. Applies widening to every class as it loads
+ *        b. Detects new plugin ClassLoaders and scans them automatically
+ *   3. Retransforms any Minecraft/server classes that are already loaded
+ */
+public class Agent {
+    private Agent() {
+        /* This utility class should not be instantiated */
+    }
+
+    private static final Logger LOG = Logger.getLogger("AccessWidenerAgent");
+
+    // Exposed so tests or other code can inspect the live transformer
+    static volatile WideningTransformer transformer;
+
+    // -javaagent: startup
+    public static void premain(String args, Instrumentation inst) {
+        init(inst);
+    }
+
+    private static void init(Instrumentation inst) {
+        LOG.info("[AccessWidener] Agent initialising.");
+
+        WideningTransformer t = new WideningTransformer(inst);
+        transformer = t;
+
+        // --- Phase 2: register transformer for future class loads ---
+        // canRetransform=true so we can call retransformClasses() later
+        inst.addTransformer(t, true);
+
+        LOG.info("[AccessWidener] Agent ready.");
+    }
+}
+