java-deobfuscator / Retroindy

Retroindy

Some All decompilers have some trouble with Java 8 features, like invokedynamic and ldc-ing MethodType and MethodHandle. It's makes it a huge pain when trying to decompile something because you have to go through the disassembly and whatever. Instead, run it through this Retroindy first and see if the program is actually as hard to read as you thought it was.

Note that the resulting program is not semantically equivalent to the original code. For one, the call stack during bootstrapping will be different. Do not attempt to use the resulting program in production!

Download

Builds can be downloaded from the CI

Usage

java -jar retroindy.jar [input.jar]

Saves to input-retro.jar

Example

Before

    public class Test {
        private static final MethodHandle[] a = new MethodHandle[4];
        
        static {
            a[0] = /* methodhandle */ null;    
            a[1] = /* methodhandle */ null;    
            a[2] = /* methodhandle */ null;    
            a[3] = /* methodhandle */ null;    
        }
        
        public static void main(String[] args) {
            System.out.<invokedynamic>a(1750247380, "Hello world");
        }
    }

After

   public class Test { 
       private static final MethodHandle[] a = new MethodHandle[4];
       private static AtomicReferenceArray CALLSITE_CACHE = new AtomicReferenceArray(new Object[1]);
    
       static {
          a[0] = MethodHandles.lookup().findVirtual(Thread.class, "getStackTrace", asMethodType("()[Ljava/lang/StackTraceElement;"));
          a[1] = MethodHandles.lookup().findVirtual(String.class, "getBytes", asMethodType("()[B"));
          a[2] = MethodHandles.lookup().findStaticGetter(System.class, "out", PrintStream.class);
          a[3] = MethodHandles.lookup().findStaticGetter(System.class, "out", PrintStream.class);
       }
       
       public static void INDY_0(PrintStream stream, String message) {
          if(CALLSITE_CACHE.get(0) == null) {
             CALLSITE_CACHE.compareAndSet(0, (Object)null, bootstrapMethod(MethodHandles.lookup(), "a", asMethodType("(Ljava/lang/String;)V"), 1750247380));
          }
    
          return (PrintStream)((CallSite)CALLSITE_CACHE.get(0)).getTarget().invokeExact(stream, message);
       }
       
       public static void main(String[] args) {
           INDY_0(System.out, "Hello world");
       }
   }