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Currently I'm trying to get past Enigma's loader, which asks you for a name & key, as an excercise.

I have very little progress, as I haven't worked too much with packers.

What I did was breakpoint on CreateWindowExA, and then I put random data at key / name, and then click Register, which effectively breaks at CreateWindowExA.

From there, I'm able to check the stack and go back a few calls, but I'm really lost as there's a lot of bloat code (short functions with x87 instructions), and I don't know where to continue.

I also know that the routine that checks the serial is virtualized, so I should patch the places which check the return of the function that checks the serial instead of the function itself, but then again, I get lost when looking at the stack.

Here's my progress so far:

The breakpoint on CreateWindowExA, which gets called when you input an invalid serial enter image description here

The function that calls it: http://screenshotuploader.com/i/1502/t_q0c.png

And that function, before and after calling CreateWindowExA, calls these two weird x87 functions:

enter image description here

the function that is marked in the previous screenshot

enter image description here

this one gets called a few instructions after CreateWindowExA

After going one more function back, I see:

enter image description here

The problem with that function is that it's using some tricks to change the return address (I guess), like this:

enter image description here

Which then leads to weird code which expects a function pointer in edx returned by a funtion that is dereferencing a pointer to a word (2 bytes)!

Here's the code that calls the function that returns a pointer to a function: enter image description here

And here's the function that returns a pointer in edx: enter image description here

It is really weird, as it 1) derefs a word (2 bytes, not enough for a function pointer!), and 2) FLDCW loads a x87 FPU control word... what's happening here?!

Also, that's the last return I can see in the stack, as the rest of the values are zeroed, and there's no branch which checks the serial at this depth, so I don't know where to continue looking at.


And if not enough, the program closes each time I input an invalid serial, which makes it harder, because the next time the offsets are totally different and I can't find the code so I breakpoint a bit before, so I'm really lost!

Dumping the executable at runtime does absolutely nothing, as it's still packed as it was before, it just makes it 4x bigger (50MB -> 200MB), and doesn't help at all.

Any help would be great, even a simple idea, like a hint on what to do next, where to breakpoint, where to look at, or whatever you can think of, would help a lot.

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