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@rbrick
Created April 16, 2020 01:01
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@Command
public void patch(@Flag("patch") File file, @Flag("server") String server) throws IOException {
if (file.exists()) {
System.out.println("Found server jar...patching...");
JarFile bungeecordJar = new JarFile(file);
byte[] newClassFile = null;
Enumeration<JarEntry> entries = bungeecordJar.entries();
while (entries.hasMoreElements()) {
JarEntry jarEntry = entries.nextElement();
if (jarEntry.getName().equalsIgnoreCase("net/md_5/bungee/api/ServerPing.class")) {
try {
ClassReader reader = new ClassReader(bungeecordJar.getInputStream(jarEntry));
ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
ClassNode node = new ClassNode();
{
reader.accept(node, 0);
}
for (int i = 0; i < node.fields.size(); i++) {
if (node.fields.get(i).name.equals("lcServer")) {
node.fields.remove(node.fields.get(i--));
}
}
node.fields.add(new FieldNode(ACC_PRIVATE, "lcServer", "Ljava/lang/String;", null, null));
for (MethodNode mn : node.methods) {
if (mn.name.equalsIgnoreCase("<init>")) {
InsnList insnList = new InsnList();
{
// this.lcServer = "Server Name";
insnList.add(new VarInsnNode(ALOAD, 0));
insnList.add(new LdcInsnNode(server));
insnList.add(new FieldInsnNode(PUTFIELD, "net/md_5/bungee/api/ServerPing", "lcServer", "Ljava/lang/String;"));
}
for (int i = 0; i < mn.instructions.size(); i++) {
// insert at the very end
if (mn.instructions.get(i).getOpcode() == INVOKESPECIAL) {
if (mn.instructions.get(i) instanceof MethodInsnNode) {
if (!((MethodInsnNode) mn.instructions.get(i)).desc.equalsIgnoreCase("()V")) {
// likely an constructor similar to this(x, y, z);
// we want to skip these.
break;
}
}
}
if (mn.instructions.get(i).getOpcode() == PUTFIELD) {
if (((FieldInsnNode) mn.instructions.get(i)).name.equalsIgnoreCase("lcServer")) {
for (int j = 0; j < 3; j++) {
mn.instructions.remove(mn.instructions.get(i--));
}
}
}
// Inject right before the RETURN statement
// We don't need to worry about anything like IRETURN. This is a void function
if (mn.instructions.get(i).getOpcode() == RETURN) {
mn.instructions.insertBefore(mn.instructions.get(i), insnList);
break;
}
}
}
}
node.accept(classWriter);
newClassFile = classWriter.toByteArray();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
bungeecordJar.close();
if (newClassFile != null) {
try {
File parent = new File("net/md_5/bungee/api");
parent.mkdirs();
File f = new File(parent, "ServerPing.class");
f.deleteOnExit();
try (FileOutputStream fos = new FileOutputStream(f)) {
fos.write(newClassFile);
}
Process process = new ProcessBuilder("jar", "uvf", file.getPath(), f.getPath()).inheritIO().start();
process.waitFor();
process.destroy();
success.set(true);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
} else {
System.out.println("File not found. Is there a typo?");
System.out.println(file.getPath());
}
}
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