Third party library (JAR) does not work in debug mode (Java)

Question

In my java project I use a third party library (jar) and call a function of that library at start.

public static void main(String args[]) {
   long handle = Library.method(params);
   if (0 == handle) {
      // error
   }
}

Use eclipse for the development. The question is, when I run the project (call the main) in RUN mode, I get the handle. But when I call with DEBUG mode (without any breakpoints attached), I do not get the handle. (The run/debug settings are the same, no additional VM or program parameters)

Question:

How can the library detect that it is called in the debug mode and prevent returning the handle?
How can I debug this project (I need some debug)

Its a commercial library for license protection and software based dongle, I do not think it is a good idea to name it here. Sorry. — benchpresser, Apr 10 '18 at 06:15
I found the answer here https://stackoverflow.com/questions/3776204/how-to-find-out-if-debug-mode-is-enabled?noredirect=1&lq=1 — benchpresser, Apr 10 '18 at 06:17
sorry, i did not see that. ok, marked as useful and accepted answer. — benchpresser, Apr 10 '18 at 10:36

score 3 · Accepted Answer · answered Apr 08 '18 at 09:29

How can the library detect that it is called in the debug mode and prevent returning the handle?

There are ways, for instance:

How to find out if "debug mode" is enabled

But it is surely not possible to assemble the complete list of possibilities.

How can I debug this project (I need some debug)

You'll either need to find a debuggable version (maybe available from the developer of the library for additional fees?) or overcome the protection.

One-guy-I-know-who-isn't-me would for instance first try to disassemble the library to find out how is it actually protected. If disassembly succeeds then it might be even possible to remove the protection.

Third party library (JAR) does not work in debug mode (Java)

1 Answers1