Ensuring classloader is isolated

Common/loader-utils/src/main/java/dev/brighten/antivpn/loader/JarInJarClassLoader.java

@@ -27,6 +27,10 @@ import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.nio.file.StandardCopyOption;
 import java.util.Arrays;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.LinkedHashSet;
+import java.util.Set;
 
 /**
  * Classloader that can load a jar from within another jar file.
@@ -38,6 +42,26 @@ import java.util.Arrays;
  * by the loading code & this classloader.</p>
  */
 public class JarInJarClassLoader extends URLClassLoader {
+    private static final String[] PARENT_FIRST_PACKAGES = {
+            "java.",
+            "javax.",
+            "jdk.",
+            "sun.",
+            "com.sun.",
+            "org.w3c.",
+            "org.xml.",
+            "org.slf4j.",
+            "com.google.inject.",
+            "javax.inject.",
+            "com.velocitypowered.",
+            "org.bukkit.",
+            "net.md_5.bungee.",
+            "org.spongepowered.",
+            "org.bstats.",
+            "dev.brighten.antivpn.velocity.org.bstats.",
+            "dev.brighten.antivpn.loader."
+    };
+
     static {
         ClassLoader.registerAsParallelCapable();
     }
@@ -59,6 +83,74 @@ public class JarInJarClassLoader extends URLClassLoader {
         addURL(url);
     }
 
+    @Override
+    protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
+        synchronized (getClassLoadingLock(name)) {
+            Class<?> loadedClass = findLoadedClass(name);
+            if (loadedClass == null) {
+                loadedClass = shouldLoadParentFirst(name) ? loadParentThenChild(name) : loadChildThenParent(name);
+            }
+
+            if (resolve) {
+                resolveClass(loadedClass);
+            }
+
+            return loadedClass;
+        }
+    }
+
+    @Override
+    public URL getResource(String name) {
+        URL resource = findResource(name);
+        if (resource != null) {
+            return resource;
+        }
+        return super.getResource(name);
+    }
+
+    @Override
+    public Enumeration<URL> getResources(String name) throws IOException {
+        Set<URL> resources = new LinkedHashSet<>();
+        Enumeration<URL> childResources = findResources(name);
+        while (childResources.hasMoreElements()) {
+            resources.add(childResources.nextElement());
+        }
+
+        Enumeration<URL> parentResources = getParent() == null
+                ? ClassLoader.getSystemResources(name)
+                : getParent().getResources(name);
+        while (parentResources.hasMoreElements()) {
+            resources.add(parentResources.nextElement());
+        }
+
+        return Collections.enumeration(resources);
+    }
+
+    private Class<?> loadChildThenParent(String name) throws ClassNotFoundException {
+        try {
+            return findClass(name);
+        } catch (ClassNotFoundException ignored) {
+            return super.loadClass(name, false);
+        }
+    }
+
+    private Class<?> loadParentThenChild(String name) throws ClassNotFoundException {
+        try {
+            return super.loadClass(name, false);
+        } catch (ClassNotFoundException ignored) {
+            return findClass(name);
+        }
+    }
+
+    private static boolean shouldLoadParentFirst(String className) {
+        for (String prefix : PARENT_FIRST_PACKAGES) {
+            if (className.startsWith(prefix)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     public void deleteJarResource() {
         URL[] urls = getURLs();
         if (urls.length == 0) {

Velocity/VelocityLoader/src/main/java/dev/brighten/antivpn/velocity/VelocityPluginLoader.java

@@ -40,6 +40,7 @@ public class VelocityPluginLoader {
     private static final String BOOTSTRAP_CLASS = "dev.brighten.antivpn.velocity.VelocityPlugin";
 
     private final LoaderBootstrap plugin;
+    private final ClassLoader pluginClassLoader;
 
     @Inject
     public VelocityPluginLoader(ProxyServer server, Logger logger, @DataDirectory Path path, Metrics.Factory metricsFactory) {
@@ -50,18 +51,30 @@ public class VelocityPluginLoader {
         instances.put(String.class, metricsFactory);
         instances.put(LoaderBootstrap.class, this);
         JarInJarClassLoader loader = new JarInJarClassLoader(getClass().getClassLoader(), JAR_NAME, SOURCE_NAME);
+        this.pluginClassLoader = loader;
         this.plugin = loader.instantiatePlugin(BOOTSTRAP_CLASS, Map.class, instances);
-        plugin.onLoad(path.toFile());
+        runWithPluginClassLoader(() -> plugin.onLoad(path.toFile()));
     }
 
     @Subscribe
     public void onInit(ProxyInitializeEvent event) {
-        plugin.onEnable();
+        runWithPluginClassLoader(plugin::onEnable);
     }
 
     @Subscribe
     public void onDisable(ProxyShutdownEvent event) {
-        plugin.onDisable();
+        runWithPluginClassLoader(plugin::onDisable);
+    }
+
+    private void runWithPluginClassLoader(Runnable action) {
+        Thread thread = Thread.currentThread();
+        ClassLoader previousClassLoader = thread.getContextClassLoader();
+        thread.setContextClassLoader(pluginClassLoader);
+        try {
+            action.run();
+        } finally {
+            thread.setContextClassLoader(previousClassLoader);
+        }
     }
 
 }