[SOLVED] [1.6.4] ASM transformer for skins

[sttwolf]

Hi, I'm currently modding my 1.6.4 client with forge to set-up custom skins on my server. I searched how to manage this mod, and I found the ASM patching way. I used the code that I will paste, and everything worked out fine but only while running my mod in eclipse's environnement (so only in an un-obfuscated minecraft) . Otherwise when I test with the official launcher, I get a crash with lots of errors. And I don't understand why or how to fix it. Help me !  :'(

 

Here is the code + the stacktrace of the error :

 

 SkinTransformer.java

package pkg;

import static org.objectweb.asm.Opcodes.ARETURN;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.INVOKESTATIC;
import java.util.Iterator;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.InsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.VarInsnNode;


public class SkinClassTransformer implements net.minecraft.launchwrapper.IClassTransformer {

    @Override
    public byte[] transform(String arg0, String arg1, byte[] arg2) {
        
        if (arg0.equals("beu")) {
            return patchClassASM(arg0, arg2, true);
        }
        
        if (arg0.equals("net.minecraft.client.entity.AbstractClientPlayer")) {
            return patchClassASM(arg0, arg2, false);
        }
        return arg2;
    }

     public byte[] patchClassASM(String name, byte[] bytes, boolean obfuscated) {
     
             String targetMethod1Name = "", targetMethod2Name = "";
             boolean ok1 = false, ok2 = false;
            
            if(obfuscated == true) {
                targetMethod1Name ="d";
                 targetMethod2Name = "e";
            }
            else {
                targetMethod1Name ="getSkinUrl";
                 targetMethod2Name = "getCapeUrl";
            }
            

            ClassNode classNode = new ClassNode();
            ClassReader classReader = new ClassReader(bytes);
            classReader.accept(classNode, 0);
     
            Iterator<MethodNode> methods = classNode.methods.iterator();
            while(methods.hasNext())
            {
                MethodNode m = methods.next();
                
                if ((m.name.equals(targetMethod1Name) && m.desc.equals("(Ljava/lang/String;)Ljava/lang/String;")))
                {
                       InsnList toInject = new InsnList();
                         
                       toInject.add(new VarInsnNode(ALOAD, 0));
                       toInject.add(new MethodInsnNode(INVOKESTATIC, "pkg/SkinPlayer", "getURLSkinCustom", "(Ljava/lang/String;)Ljava/lang/String;"));
                       toInject.add(new InsnNode(ARETURN));
                    
                       m.instructions = toInject;
                       ok1 = true;
                }
                else if ((m.name.equals(targetMethod2Name) && m.desc.equals("(Ljava/lang/String;)Ljava/lang/String;")))
                {
                       InsnList toInject = new InsnList();
                         
                       toInject.add(new VarInsnNode(ALOAD, 0));
                       toInject.add(new MethodInsnNode(INVOKESTATIC, "pkg/SkinPlayer", "getURLCapeCustom", "(Ljava/lang/String;)Ljava/lang/String;"));
                       toInject.add(new InsnNode(ARETURN));
                    
                       m.instructions = toInject;
                       ok2 = true;
                }
                
                if(ok1 && ok2)
                    break;
            }
            
            ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
            classNode.accept(writer);
            return writer.toByteArray();
      }
}

 

 SkinPlayer.java

package pkg;

import java.net.HttpURLConnection;
import java.net.URL;

import net.minecraft.util.StringUtils;

public class SkinPlayer {
    
    private static String connexion (String adress, String par0Str){
        int code = 404;
        try {
            URL u = new URL (adress);
            HttpURLConnection huc =  ( HttpURLConnection )  u.openConnection (); 
            huc.setRequestMethod ("GET"); 
            huc.connect () ; 
            code = huc.getResponseCode() ;

            if (code == HttpURLConnection.HTTP_OK) 
                return adress;

            else if (code == HttpURLConnection.HTTP_MOVED_TEMP
                    || code == HttpURLConnection.HTTP_MOVED_PERM
                        || code == HttpURLConnection.HTTP_SEE_OTHER) {
                String newUrl = huc.getHeaderField("Location");
    
                huc = (HttpURLConnection) new URL(newUrl).openConnection();
                huc.setRequestMethod ("GET"); 
                huc.connect (); 
                code = huc.getResponseCode();
                if (code == HttpURLConnection.HTTP_OK) 
                    return newUrl;
            }
        }
        catch(Exception e){
        }
        return String.format("official minecraft.net skins url", new Object[] {StringUtils.stripControlCodes(par0Str)});
    }
    

    public static String getURLSkinCustom(String par0Str)
    {
        String adress=String.format("http://www.somesite.com/skin/%s", new Object[] {StringUtils.stripControlCodes(par0Str)});
        return connexion(adress, par0Str);
    }
    
    public static String getURLCapeCustom(String par0Str)
    {
        String adress=String.format("http://www.somesite.com/cape/%s", new Object[] {StringUtils.stripControlCodes(par0Str)});
        return connexion(adress, par0Str);
    }
    
}

 

 SkinFMLLoadingPlugin.java

package pkg;

import java.io.File;
import java.util.Map;

import cpw.mods.fml.relauncher.IFMLLoadingPlugin.MCVersion;

@MCVersion(value = "1.6.4")

public class SkinFMLLoadingPlugin implements cpw.mods.fml.relauncher.IFMLLoadingPlugin {
        
    @Override
    public String[] getLibraryRequestClass() {
        return null;
    }

    @Override
    public String[] getASMTransformerClass() {
        return new String[]{SkinClassTransformer.class.getName()};
    }

    @Override
    public String getModContainerClass() {
        return SkinDummyContainer.class.getName();
    }

    @Override
    public String getSetupClass() {
        return null;
    }

    @Override
    public void injectData(Map<String, Object> data) {

    }

}

 

SkinDummyContainer.java 

package pkg;

import java.util.Arrays;

import net.minecraftforge.common.Configuration;
import net.minecraftforge.event.ForgeSubscribe;

import com.google.common.eventbus.EventBus;

import cpw.mods.fml.common.DummyModContainer;
import cpw.mods.fml.common.LoadController;
import cpw.mods.fml.common.Mod.EventHandler;
import cpw.mods.fml.common.ModMetadata;
import cpw.mods.fml.common.event.FMLConstructionEvent;
import cpw.mods.fml.common.event.FMLInitializationEvent;
import cpw.mods.fml.common.event.FMLPostInitializationEvent;
import cpw.mods.fml.common.event.FMLPreInitializationEvent;

public class SkinDummyContainer extends DummyModContainer {

    
    public SkinDummyContainer() {
        super(new ModMetadata());
        ModMetadata meta = getMetadata();
        meta.modId = "something";
        meta.name = "something";
        meta.version = "1.0";
        meta.credits = "something";
        meta.authorList = Arrays.asList("something");
        meta.description = "something";
        meta.url = "something";
        meta.updateUrl = "";
        meta.screenshots = new String[0];
        meta.logoFile = "";
    }

    @ForgeSubscribe
    public boolean registerBus(EventBus bus, LoadController controller) {
        bus.register(this);
        return true;
    }

    @EventHandler
    public void modConstruction(FMLConstructionEvent event){

    }

    @EventHandler
    public void init(FMLInitializationEvent evt) {

    }
    
    @EventHandler
    public void preInit(FMLPreInitializationEvent event) {

    }

    @EventHandler
    public void postInit(FMLPostInitializationEvent evt) {

    }

}

 

The MANIFEST file inside mod's jarfile :

 

MANIFEST.MF 

Manifest-Version: 1.0
FMLCorePlugin: pkg.SkinFMLLoadingPlugin
-Dfml.coreMods.load=pkg.SkinFMLLoadingPlugin

 

And now the stacktrace, and I repeat that it happen ONLY WHEN TESTING OUTSIDE ECLIPSE :

 

Client> 2014-06-05 00:13:39 [GRAVE] [ForgeModLoader] Unable to launch
Client> java.lang.reflect.InvocationTargetException
Client>     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
Client>     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
Client>     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
Client>     at java.lang.reflect.Method.invoke(Unknown Source)
Client>     at net.minecraft.launchwrapper.Launch.launch(Launch.java:131)
Client>     at net.minecraft.launchwrapper.Launch.main(Launch.java:27)
Client> Caused by: java.lang.NoClassDefFoundError: net/minecraft/client/entity/EntityClientPlayerMP
Client>     at net.minecraft.client.main.Main.main(SourceFile:37)
Client>     ... 6 more
Client> Caused by: java.lang.ClassNotFoundException: net.minecraft.client.entity.EntityClientPlayerMP
Client>     at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:186)
Client>     at java.lang.ClassLoader.loadClass(Unknown Source)
Client>     at java.lang.ClassLoader.loadClass(Unknown Source)
Client>     ... 7 more
Client> Caused by: java.lang.NoClassDefFoundError: net/minecraft/client/entity/EntityPlayerSP
Client>     at java.lang.ClassLoader.defineClass1(Native Method)
Client>     at java.lang.ClassLoader.defineClass(Unknown Source)
Client>     at java.security.SecureClassLoader.defineClass(Unknown Source)
Client>     at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:178)
Client>     ... 9 more
Client> Caused by: java.lang.ClassNotFoundException: net.minecraft.client.entity.EntityPlayerSP
Client>     at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:186)
Client>     at java.lang.ClassLoader.loadClass(Unknown Source)
Client>     at java.lang.ClassLoader.loadClass(Unknown Source)
Client>     ... 13 more
Client> Caused by: java.lang.NoClassDefFoundError: net/minecraft/client/entity/AbstractClientPlayer
Client>     at java.lang.ClassLoader.defineClass1(Native Method)
Client>     at java.lang.ClassLoader.defineClass(Unknown Source)
Client>     at java.security.SecureClassLoader.defineClass(Unknown Source)
Client>     at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:178)
Client>     ... 15 more
Client> Caused by: java.lang.ClassNotFoundException: net.minecraft.client.entity.AbstractClientPlayer
Client>     at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:186)
Client>     at java.lang.ClassLoader.loadClass(Unknown Source)
Client>     at java.lang.ClassLoader.loadClass(Unknown Source)
Client>     ... 19 more
Client> Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: bic
Client>     at org.objectweb.asm.ClassWriter.getCommonSuperClass(Unknown Source)
Client>     at org.objectweb.asm.ClassWriter.a(Unknown Source)
Client>     at org.objectweb.asm.Frame.a(Unknown Source)
Client>     at org.objectweb.asm.Frame.a(Unknown Source)
Client>     at org.objectweb.asm.MethodWriter.visitMaxs(Unknown Source)
Client>     at org.objectweb.asm.tree.MethodNode.accept(Unknown Source)
Client>     at org.objectweb.asm.tree.MethodNode.accept(Unknown Source)
Client>     at org.objectweb.asm.tree.ClassNode.accept(Unknown Source)
Client>     at vertebro.SkinClassTransformer.patchClassASM(SkinClassTransformer.java:86)
Client>     at vertebro.SkinClassTransformer.transform(SkinClassTransformer.java:23)
Client>     at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:274)
Client>     at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:172)
Client>     ... 21 more

 

Thanks ! 

[coolboy4531]

Use byte[] trasnform's arg1 (String).

Here you can return a path to that class.

 

Example:

//Let's suppose e = net.minecraft.entity.Entity.
if (arg0.equals("e"))

can be replaced by:

if (arg1.equals("net.minecraft.entity.Entity"))

[sttwolf]

Should I do this ? : if (arg1.equals("beu")) {

return patchClassASM(arg1, arg2, true);

        }

 

if (arg1.equals("net.minecraft.client.entity.AbstractClientPlayer")) {

return patchClassASM(arg1, arg2, false);

        }

 

instead of         if (arg0.equals("beu")) {

            return patchClassASM(arg0, arg2, true);

        }

       

        if (arg0.equals("net.minecraft.client.entity.AbstractClientPlayer")) {

            return patchClassASM(arg0, arg2, false);

        }  ?

[coolboy4531]

arg1.

You can use the path of the imported class.

(net.minecraft.entity.Entity) is an example.

 

Even if it is obfuscated (in the Minecraft database, originally) - Forge edits that path, and puts it in the code without reobfuscation.

This means that you can use that path even in the real game (not Eclipse environment).

[sttwolf]

I did replace the path, but it still isn't working, what's wrong ?

If I understood it good, I must return the full path, not the obfuscated one ?

[coolboy4531]

Show me what you have as of now.

[sttwolf]

Here it is :

package pkg;

import static org.objectweb.asm.Opcodes.ARETURN;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.INVOKESTATIC;
import java.util.Iterator;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.InsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.VarInsnNode;


public class SkinClassTransformer implements net.minecraft.launchwrapper.IClassTransformer {

    @Override
    public byte[] transform(String arg0, String arg1, byte[] arg2) {
        
        if (arg0.equals("beu")) {
            return patchClassASM(arg1, arg2, true);
        }
        
        if (arg0.equals("net.minecraft.client.entity.AbstractClientPlayer")) {
            return patchClassASM(arg1, arg2, false);
        }
        return arg2;
    }

     public byte[] patchClassASM(String name, byte[] bytes, boolean obfuscated) {
     
             String targetMethod1Name = "", targetMethod2Name = "";
             boolean ok1 = false, ok2 = false;
            
             targetMethod1Name ="getSkinUrl";
             targetMethod2Name = "getCapeUrl";
        
	    ClassNode classNode = new ClassNode();
        ClassReader classReader = new ClassReader(bytes);
        classReader.accept(classNode, 0);

        Iterator<MethodNode> methods = classNode.methods.iterator();
        while(methods.hasNext())
        {
            MethodNode m = methods.next();
            
            if ((m.name.equals(targetMethod1Name) && m.desc.equals("(Ljava/lang/String;)Ljava/lang/String;")))
            {
                   InsnList toInject = new InsnList();
                     
                   toInject.add(new VarInsnNode(ALOAD, 0));
                   toInject.add(new MethodInsnNode(INVOKESTATIC, "pkg/SkinPlayer", "getURLSkinCustom", "(Ljava/lang/String;)Ljava/lang/String;"));
                   toInject.add(new InsnNode(ARETURN));
                
                   m.instructions = toInject;
                   ok1 = true;
                   break;
            }
            else if ((m.name.equals(targetMethod2Name) && m.desc.equals("(Ljava/lang/String;)Ljava/lang/String;")))
            {
                   InsnList toInject = new InsnList();
                     
                   toInject.add(new VarInsnNode(ALOAD, 0));
                   toInject.add(new MethodInsnNode(INVOKESTATIC, "pkg/SkinPlayer", "getURLCapeCustom", "(Ljava/lang/String;)Ljava/lang/String;"));
                   toInject.add(new InsnNode(ARETURN));
                
                   m.instructions = toInject;
                   ok2 = true;
                   break;
            }
            
            if(ok1 && ok2)
            	break;
        }
        
        ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
        classNode.accept(writer);
        return writer.toByteArray();
      }
}

[coolboy4531]

I told you to change "arg0" to "arg1."

 

Do it and I'm somewhat positive it'll work.

[sttwolf]

I told you to change "arg0" to "arg1."

 

Do it and I'm somewhat positive it'll work.

Which part of code ? 

[sttwolf]

I told you to change "arg0" to "arg1."

 

Do it and I'm somewhat positive it'll work.

Which part of code ? 

So I modified but still the same error

 

    public byte[] transform(String arg0, String arg1, byte[] arg2) {
        
        if (arg1.equals("beu")) {
            return patchClassASM(arg1, arg2, true);
        }
        
        if (arg1.equals("net.minecraft.client.entity.AbstractClientPlayer")) {
            return patchClassASM(arg1, arg2, false);
        }
        return arg2;
    }

 

Sorry for double post.

[coolboy4531]

Don't know the issue, but take a look at one of my friend's (I helped him work on it too) core-mods, SuperEnchants.

 

I need to be extremely careful with copyright - this means I will only show byte[] transform

I've trimmed down the code to what's useful for us to know.

 

Transformer Class

private static ArrayList<String> enchantList = new ArrayList(Arrays.asList(new String[] { "net.minecraft.enchantment.EnchantmentArrowDamage", "net.minecraft.enchantment.EnchantmentArrowFire", "net.minecraft.enchantment.EnchantmentArrowInfinite", "net.minecraft.enchantment.EnchantmentArrowKnockback [~]you get the point.[~]" }; 

  public byte[] transform(String classname, String arg1, byte[] bytearray)
  {
    int e_index = 0;

    if (enchantList.contains(arg1))
    {
      e_index = enchantList.indexOf(classname);
      System.out.println("Ready to transform class ->  " + classname);
      return patchClassASM(classname, bytearray, false, e_index);
    }
    return bytearray;
  }

I suggest you create an array-list like this one just in case it requires an index.

[sttwolf]

Thanks, I will try, but that still doesn't tell me why it's working on my eclipse

[GotoLink]

targetMethod1Name ="getSkinUrl";
             targetMethod2Name = "getCapeUrl";

You are targeting unobfuscated methods, so obviously, this isn't going to work in any other environment.

[sequituri]

I'd look to find why the "bic" class is not found.

[sttwolf]

targetMethod1Name ="getSkinUrl";
             targetMethod2Name = "getCapeUrl";

You are targeting unobfuscated methods, so obviously, this isn't going to work in any other environment.

Nope. That's why I did this :

            if(obfuscated == true) {
                targetMethod1Name ="d";
                 targetMethod2Name = "e";
            }
            else {
                targetMethod1Name ="getSkinUrl";
                 targetMethod2Name = "getCapeUrl";
            }

 

I'd look to find why the "bic" class is not found.

Yeah it's really really weird

[sttwolf]

Don't use ASM for stuff like this. Don't make a coremod if you don't know what on earth you are doing (which this thread shows you are not), you are only gonna screw things up. And if a coremod screws up, all other mods screw up potentially.

Use RenderPlayerEvent.

What a really nice contribution, if only you wrote that much in order to help my problem, you would have been useful, which your post shows you are not. Anyway, thanks the tip, I will check that.

[sttwolf]

Well then. Your error is the following:

You tell ASM to compute the Stack Map frames. In order to do that, ASM loads classes, because it needs to compute the "common superclass" (e.g.: Common Superclass of String and List is Object, Common Superclass of ArrayList and LinkedList is AbstractList). The problem is: Sometimes this can lead to ASM trying to load a class while this class is being transformed. (Hint: That is not good).

Solution: Don't compute the frames, you should be able to do that yourself for those two simple methods.

 

Also: Replacing entire methods is a bad idea.

Thanks, it's more clear to me now. You see, I'm new to minecraft modding, especially in forge. I know Java, but I never used the ASM thingy. I followed a tutorial that told me it could work. So now I will look at RenderPlayerEvent, I'm just wondering, do I have to do the entire code for modeling the player or I can just modify the skin straight away ?

[sttwolf]

You have to replace rendering anyways so you could just replace the entire RenderPlayer instance which is possible without ASM or base edits.

Sorry to bother you again, but, does this code would work ?

 

public class PlayerRenderEvent
{
@ForgeSubscribe
public void onPlayerRender(RenderPlayerEvent.Specials.Pre event)
{
AbstractClientPlayer player = (AbstractClientPlayer)event.entityPlayer;
if(player.username != null && !player.username.isEmpty())
{
ObfuscationReflectionHelper.setPrivateValue(AbstractClientPlayer.class, player, this.getDownloadImageSkin(this.getLocationSkin(player.username), player.username), "field_110315_c", "downloadImageSkin", "c");
ObfuscationReflectionHelper.setPrivateValue(AbstractClientPlayer.class, player, this.getLocationCape(player.username), "field_110313_e", "locationCape", "e");
}
}

public static ThreadDownloadImageData getDownloadImageSkin(ResourceLocation resourceLocation, String playerName)
{
return getDownloadImage(resourceLocation, getSkinUrl(playerName), (ResourceLocation)null, (IImageBuffer)null);
}

private static ThreadDownloadImageData getDownloadImage(ResourceLocation res, String link, ResourceLocation defRes, IImageBuffer image)
{
TextureManager texturemanager = Minecraft.getMinecraft().getTextureManager();
Object object = texturemanager.getTexture(res);

if(object == null)
{
object = new ThreadDownloadImageData(link, defRes, image);
texturemanager.loadTexture(res, (TextureObject)object);
}

return (ThreadDownloadImageData)object;
}

public static String getSkinUrl(String playerName)
{
return String.format("somesite/%s.png", new Object[] {StringUtils.stripControlCodes(playerName)});
}

public static ResourceLocation getLocationSkin(String playerName)
{
return new ResourceLocation("modid", "skins/" + StringUtils.stripControlCodes(playerName));
}
}

}

[sttwolf]

It should work, but there is no reason to do this every single frame.

Then how to make it happen just one time ? Changing the event ?

 

[sttwolf]

It works, but, only down, the skin gets displayed only when opening inventory, got an idea on that ?

[sttwolf]

Don't have my IDE open anymore, if I remember I'll look into it tomorrow.

Thanks for everything ! 

[DarkOfNight]

Can we show your final code please?

[hypercross]

Your code is actually perfectly fine except for your ClassWriter's parameter. You want COMPUTE_MAXS, not COMPUTE_FRAMES + COMPUTE_MAXS.

 

COMPUTE_FRAMES + COMPUTE_MAXS basically means the class is reassembled from scratch and ASM looks for class references present in the transformed class. But as transformation happens during class loading, some of the referenced classes are not present at that time. As a result you get a bunch of class not found exceptions.