dynaemu

Hi, I was just wondering how with some programs there's a limited amount you can run (like only one at a time, or something) - can this be bypassed through ollydbg? If so, what kind of calls should I be looking for, or how do I find them? Thanks in advance.

Dameon

On windows at least a single-instance restriction is usually done by trying to obtain a system-wide mutex. The first app gets the lock, the others exit.

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Jabo

I don't know if this is what you are looking for, but it could be. This is on the project properties page in VB 2005

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dynaemu

That's kind of what I'm talking about, but I'm looking for a way to -bypass- this

Dameon

Investigate what I said. Poke around for API calls relating to mutexes. The mutex will likely be created with a name that contains the name of the application (makes sense) and execution will branch based on the return code -- one branch causes the program to exit. I made this modification to the Ventrilo client once. I can't remember the specifics but it was easy and obvious when knowing what to look for.

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Irwin

Set a breakpoint on CreateMutexA/W and see if that yields any results.