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javareverse-engineeringobfuscationdecompilerdeobfuscation

Java deobfuscator supporting variable renaming?

I'm trying to reverse engineering a .jar file (basically a group of .class files). However, there are two difficulties:

  1. Some of the variables, methods and classes are named with unicode characters, which cannot be properly displayed. This makes source editing very inconvenient.

  2. Some of the classes are named with Java keywords (such as if). Therefore Java compiler will complain when recompiling the reverse-engineered source files.

Are there any Java deobfuscators that can overcome these difficulties?

Solution

  • There are several tools that can rename Java identifers. For example, you can just run Proguard on it to rename everything.

    That being said, I would suggest reconsidering your approach. Java compilation and decompilation are both lossy processes. Decompilation is useful for reverse engineering, but you generally cannot expect to be able to recompile the decompiled code. If it has previously been obfuscated, you may as well forget it.

    The best way to modify obfuscated code is to use the Krakatau assembler and disassembler. Krakatau assembly can be reversibly transformed to and from bytecode, meaning you can edit arbitrary classes without messing things up, no matter how they have been obfuscated. The only downside is that you have to be familiar with Java bytecode.