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Fix Agent and WideningTransformer and ClassPatcher

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This commit is contained in:
YoyoNow
2026-06-11 13:19:04 +02:00
parent 786257ad0e
commit 961331f029
6 changed files with 105 additions and 279 deletions
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AccessWidener/src/main/java/de/steamwar/AccessWidenerScanner.java
-145
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@@ -1,145 +0,0 @@
/*
* 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.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.instrument.Instrumentation;
import java.lang.reflect.Field;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.file.Path;
import java.util.*;
import java.util.logging.Logger;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
/**
* Scans all plugin ClassLoaders for "plugin.accesswidener" resources
* and returns the parsed entries.
*/
public final class AccessWidenerScanner {
private static final Logger LOG = Logger.getLogger("AccessWidenerScanner");
private AccessWidenerScanner() {
}
/**
* Scans every ClassLoader visible from the already-loaded classes for
*/
public static List<AccessWidenerEntry> scanAll(Instrumentation inst) {
List<AccessWidenerEntry> allEntries = new ArrayList<>();
Set<ClassLoader> seen = Collections.newSetFromMap(new IdentityHashMap<>());
for (Class<?> clazz : inst.getAllLoadedClasses()) {
ClassLoader cl = clazz.getClassLoader();
if (cl == null) continue; // bootstrap — skip
if (!seen.add(cl)) continue; // already processed
if (!isPluginClassLoader(cl)) continue;
allEntries.addAll(scanClassLoader(cl));
}
return allEntries;
}
/**
* Uses getResources() so it finds ALL matching files on the loader's classpath.
*/
public static List<AccessWidenerEntry> scanClassLoader(ClassLoader cl) {
List<AccessWidenerEntry> entries = new ArrayList<>();
try {
for (URL url : findAccessWideners(cl)) {
try (InputStream in = url.openStream()) {
List<AccessWidenerEntry> parsed = AccessWidenerParser.parse(in);
LOG.info("[AccessWidener] Loaded " + parsed.size() + " entries from " + url);
entries.addAll(parsed);
} catch (IOException e) {
LOG.warning("[AccessWidener] Failed to read " + url + ": " + e.getMessage());
}
}
} catch (IOException e) {
LOG.warning("[AccessWidener] Failed to scan " + cl + ": " + e.getMessage());
}
return entries;
}
public static List<URL> findAccessWideners(ClassLoader cl) throws IOException {
List<URL> results = new ArrayList<>();
// Standard path — works on most Paper versions
if (cl instanceof URLClassLoader urlCl) {
return scanUrls(urlCl.getURLs());
}
// Newer Paper — PluginClassLoader stores the jar as a field
try {
// Try common field names used across Paper versions
for (String fieldName : List.of("file", "jarFile", "pluginJar", "source")) {
try {
Field f = cl.getClass().getDeclaredField(fieldName);
f.setAccessible(true);
Object value = f.get(cl);
if (value instanceof File file) {
return scanUrls(new URL[]{ file.toURI().toURL() });
}
if (value instanceof Path path) {
return scanUrls(new URL[]{ path.toUri().toURL() });
}
} catch (NoSuchFieldException ignored) {}
}
} catch (Exception e) {
LOG.warning("[AccessWidener] Could not extract JAR path from " + cl + ": " + e.getMessage());
}
return results;
}
private static List<URL> scanUrls(URL[] urls) throws IOException {
List<URL> results = new ArrayList<>();
for (URL url : urls) {
if (!url.getPath().endsWith(".jar")) continue;
try (ZipInputStream zip = new ZipInputStream(url.openStream())) {
ZipEntry entry;
while ((entry = zip.getNextEntry()) != null) {
if (entry.getName().endsWith(".accesswidener")) {
results.add(new URL("jar:" + url + "!/" + entry.getName()));
}
}
}
}
return results;
}
/**
* Returns true if the classloader looks like a Paper plugin classloader.
* Checks by name so we don't need a direct dependency on Paper internals.
*/
public static boolean isPluginClassLoader(ClassLoader cl) {
String name = cl.getClass().getName();
return name.contains("PluginClassLoader") // legacy Paper / Spigot
|| name.contains("PaperPluginLoader") // Paper 1.20.5+
|| name.contains("PaperSimplePluginManager"); // just in case
}
}
AccessWidener/src/main/java/de/steamwar/Agent.java
+20 -10
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@@ -19,7 +19,11 @@
package de.steamwar;
import java.io.File;
import java.io.IOException;
import java.lang.instrument.Instrumentation;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Logger;
/**
@@ -38,14 +42,11 @@ import java.util.logging.Logger;
*/
public class Agent {
private Agent() {
/* This utility class should not be instantiated */
throw new IllegalStateException("Utility class");
}
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);
@@ -54,13 +55,22 @@ public class Agent {
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);
List<AccessWidenerEntry> entries = new ArrayList<>();
File file = new File(new File(".").getAbsoluteFile(), "plugins/");
File[] files = file.listFiles();
if (files == null) files = new File[0];
for (File jarFile : files) {
if (!jarFile.isFile()) continue;
if (!jarFile.getName().endsWith(".jar")) continue;
try {
entries.addAll(Utils.findAndParseAccessWideners(jarFile.toPath()));
} catch (IOException e) {
LOG.warning("Failed to parse access wideners from " + jarFile.getAbsolutePath());
}
}
LOG.info("[AccessWidener] Loaded " + entries.size() + " access wideners.");
inst.addTransformer(new WideningTransformer(entries), false);
LOG.info("[AccessWidener] Agent ready.");
}
}
AccessWidener/src/main/java/de/steamwar/ClassPatcher.java
+14 -6
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@@ -19,10 +19,12 @@
package de.steamwar;
import org.objectweb.asm.*;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import java.util.List;
import java.util.Set;
import java.util.logging.Logger;
import java.util.stream.Collectors;
/**
@@ -33,6 +35,8 @@ import java.util.stream.Collectors;
*/
public class ClassPatcher {
private static final Logger LOG = Logger.getLogger("ClassPatcher");
private final List<AccessWidenerEntry> entries;
/** Pre-computed set of targeted internal names for fast filtering. */
@@ -46,18 +50,22 @@ public class ClassPatcher {
}
/**
* Patches {@code classBytes} if {@code internalName} is targeted.
* Patches {@code classBytes} if {@code className} is targeted.
*
* @return patched bytes, or {@code null} if no changes were needed
*/
public byte[] patch(String internalName, byte[] classBytes) {
if (!targets.contains(internalName)) return null;
public byte[] patch(String className, byte[] classBytes) {
if (!targets.contains(className)) return null;
try {
ClassReader cr = new ClassReader(classBytes);
// COMPUTE_FRAMES would require the full classpath; we only touch flags so 0 is fine
ClassWriter cw = new ClassWriter(cr, 0);
cr.accept(new ClassTransformer(cw, internalName, entries), 0);
cr.accept(new ClassTransformer(cw, className, entries), ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES);
return cw.toByteArray();
} catch (Exception e) {
LOG.warning("[AccessWidener] Failed to transform " + className + ": " + e.getMessage());
return null;
}
}
}
AccessWidener/src/main/java/de/steamwar/Utils.java
+60
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@@ -0,0 +1,60 @@
/*
* 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.io.IOException;
import java.io.InputStream;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.logging.Logger;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
public class Utils {
private static final Logger LOG = Logger.getLogger("AccessWidenerAgent");
private Utils() {
throw new IllegalStateException("Utility class");
}
public static List<AccessWidenerEntry> findAndParseAccessWideners(Path jarPath) throws IOException {
List<AccessWidenerEntry> results = new ArrayList<>();
try (ZipFile zip = new ZipFile(jarPath.toFile())) {
Enumeration<? extends ZipEntry> entries = zip.entries();
while (entries.hasMoreElements()) {
ZipEntry entry = entries.nextElement();
if (entry.isDirectory() || !entry.getName().endsWith(".accesswidener")) continue;
try (InputStream in = zip.getInputStream(entry)) {
results.addAll(AccessWidenerParser.parse(in));
} catch (IOException e) {
LOG.warning("[AccessWidener] Failed to parse " + entry.getName()
+ " in " + jarPath.getFileName() + ": " + e.getMessage());
}
}
}
return results;
}
}
AccessWidener/src/main/java/de/steamwar/WideningTransformer.java
+8 -108
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@@ -19,17 +19,9 @@
package de.steamwar;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;
import java.security.ProtectionDomain;
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.logging.Logger;
import java.util.stream.Collectors;
import java.util.List;
/**
* Transforms class bytecode to apply access widening rules.
@@ -39,111 +31,19 @@ import java.util.stream.Collectors;
*/
public class WideningTransformer implements ClassFileTransformer {
private static final Logger LOG = Logger.getLogger("WidenerTransformer");
private final ClassPatcher patcher;
private final Instrumentation instrumentation;
/**
* All entries collected across all plugins. Thread-safe for concurrent plugin loads.
*/
private final List<AccessWidenerEntry> entries = new CopyOnWriteArrayList<>();
/**
* ClassLoaders we have already scanned, to avoid re-scanning.
*/
private final Set<ClassLoader> scannedLoaders = Collections.synchronizedSet(Collections.newSetFromMap(new IdentityHashMap<>()));
public WideningTransformer(Instrumentation instrumentation) {
this.instrumentation = instrumentation;
public WideningTransformer(List<AccessWidenerEntry> entries) {
patcher = new ClassPatcher(entries);
}
/**
* Add entries — used during initial scan before the transformer is registered.
*/
public void addEntries(List<AccessWidenerEntry> newEntries) {
entries.addAll(newEntries);
}
// -------------------------------------------------------------------------
// ClassFileTransformer
// -------------------------------------------------------------------------
@Override
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) {
// Check for new plugin classloaders we haven't seen yet
if (loader != null && AccessWidenerScanner.isPluginClassLoader(loader) && scannedLoaders.add(loader)) {
onNewPluginClassLoader(loader);
}
// No entries for this class — skip transformation entirely
if (className == null) return classfileBuffer;
boolean relevant = entries.stream().anyMatch(e -> e.targets(className));
if (!relevant) return classfileBuffer;
// Apply widening via ASM
try {
ClassReader cr = new ClassReader(classfileBuffer);
ClassWriter cw = new ClassWriter(cr, 0);
cr.accept(new ClassTransformer(cw, className, entries), 0);
return cw.toByteArray();
} catch (Exception e) {
LOG.warning("[AccessWidener] Failed to transform " + className + ": " + e.getMessage());
byte[] result = patcher.patch(className, classfileBuffer);
if (result == null) {
return classfileBuffer;
}
}
// -------------------------------------------------------------------------
// New ClassLoader detection
// -------------------------------------------------------------------------
private void onNewPluginClassLoader(ClassLoader loader) {
List<AccessWidenerEntry> newEntries = AccessWidenerScanner.scanClassLoader(loader);
if (newEntries.isEmpty()) return;
entries.addAll(newEntries);
LOG.info("[AccessWidener] Picked up " + newEntries.size() + " new entr" + (newEntries.size() == 1 ? "y" : "ies") + " from " + loader);
// Retransform already-loaded classes that are now targeted
scheduleRetransform(newEntries);
}
/**
* Retransformation cannot be called from within a transform() call,
* so we dispatch it to a short-lived daemon thread.
*/
private void scheduleRetransform(List<AccessWidenerEntry> newEntries) {
Set<String> targets = newEntries.stream().map(e -> e.target().replace('/', '.')).collect(Collectors.toSet());
Thread t = new Thread(() -> retransform(targets), "access-widener-retransform");
t.setDaemon(true);
t.start();
}
private void retransform(Set<String> dotNames) {
List<Class> toRetransform = Arrays.stream(instrumentation.getAllLoadedClasses())
.filter(c -> dotNames.contains(c.getName()))
.filter(instrumentation::isModifiableClass)
.collect(Collectors.toList());
if (toRetransform.isEmpty()) return;
LOG.info("[AccessWidener] Retransforming " + toRetransform.size() + " class(es).");
List<String> failed = new ArrayList<>();
for (Class<?> clazz : toRetransform) {
try {
instrumentation.retransformClasses(clazz);
} catch (UnmodifiableClassException | UnsupportedOperationException e) {
failed.add(clazz.getName());
}
}
if (!failed.isEmpty()) {
LOG.warning("[AccessWidener] The following classes were already loaded before the agent"
+ " and cannot be retransformed. Add -javaagent: to your start script"
+ " to fix this:");
failed.forEach(name -> LOG.warning(" - " + name));
} else {
return result;
}
}
}
BauSystem/build.gradle.kts
-7
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@@ -20,22 +20,15 @@
plugins {
`java-library`
alias(libs.plugins.shadow)
id("io.papermc.paperweight.userdev") version "1.7.1"
}
tasks.build {
finalizedBy(tasks.shadowJar)
}
repositories {
maven("https://repo.papermc.io/repository/maven-public/")
}
dependencies {
implementation(project(":BauSystem:BauSystem_RegionFixed"))
implementation(project(":BauSystem:BauSystem_Main"))
paperweight.paperDevBundle("1.21.1-R0.1-SNAPSHOT")
}
tasks.register<DevServer>("DevBau21") {