i created an injectable dll and in the "DllEntryPoint" i call SetTimer api to set a timer but somehow it doesn't sets the timer!

here is the code btw:

any ideas why SetTimer api doesn't sets the timer on the "TimerProc" callback function?!
btw,GetLastError returns 0 and SetTimer api returns an integer value so this means there's nothing wrong?!?!?!if nothing's wrong then why it doesn't sets the timer
?

john_25

Who said, it does not? It does. But I assume there's nobody, who's willing to process WM_TIMER for you.

so you mean i can't set another timer via dll injection inside another process?

john_25
I mean, you can, and the timer will post WM_TIMER messages to the thread's message queue. But this other process must be kind enough to take the messages from the message queue of the thread, that called LoadLibrary on your dll, and call the default handling procedure for these messages, so that the handling procedure calls your TimerProc. Otherwise the callback just won't be called.

In some cases of dll injection (such as the one with CreateRemoteThread) the thread exits right after calling LoadLibrary. If this is your case, it doesn't make any sense to hope, that your callback will ever be called.

SetTimer requires a message loop to be active somewhere within the process.

It might be easier to create a thread and use Sleep but there is a risk that the process might use ret instead of ExitProcess and leave you with a zombie process.

revolution
I would not take such little hackers products into account. Nearly every legitimate program terminates by calling ExitProcess. ret is a bad practice anyway just because some API calls may allow themselves to create additional threads (such as GetOpenFileName).

But periodical checking for presence of other threads in a process is also trivial.

Adding and testing the code is not a big problem the main thing here is just to be aware of such possibilities.