I've been wanting to reverse engineer this clients launcher in an effort to understand how the game was launching as a Java application despite it only having a PE32 executable alongside it.

The launching of the client goes as follows:

java -Xmx384M -Dfile.encoding="UTF-8" -cp TargetBinary.exe com.java.client.Client

Now I was curious what TargetBinary.exe actually was, as this was being ran on a *NIX system. Running file I observed this output.

TargetBinary.exe: PE32 executable (GUI) Intel 80386 (stripped to external PDB), for MS Windows

The second part is the com.java.client.Client after the TargetBinary.exe, this stands out as a Java pathing which Client is my target.

Here are my questions:

1. How can Java add the TargetBinary.exe to its classpath?
2. As a followup, are there any recommendations to decompile it to the point where I can observe Client and more so understand how it was all packed together?

Being a Portable Executable (PE) the libs, code, etc should all be there inside the TargetBinary.exe and somehow Java knows what to do with it?

Thank you very much!

CodePudding user response：

Zip files are read from the back, so it's easy to put a zip (jar) file at the end of an executable file, and have it work as both.

See https://en.wikipedia.org/wiki/ZIP_(file_format)#Structure

Try running jar -tvf TargetBinary.exe to see the names of the classes and resources in the jar. If you make the file a dependency of a project in your IDE you can see decompiled code and navigate around the project, and run it and set breakpoints.