Lena's Tuts: 04. Basic + aesthetic patching

The target will be PixtopianBook.exe, an address book application for managing contact information. The objective is to get rid of all the limitations in this application so that it will act like the registered version.This tutorial starts off with encountering an exception. Personally I did not encounter this so I won't give any explanation further then this. Next we examine the application. Then upon finding the restrictions we locate and patch them to open up the full functionality of the program.

For non-programmers this may be difficult. I recommend reading a little about Windows Architecture. After all we are reversers. It's crucial you know at least the basics about the Operating System since it controls the execution of all code. I also recommend at least the introduction from Windows Internals Fifth Ed.

Basically when Pixtopian displays the message boxes an API is being called. This API is called MessageBox. If you have yet to encounter this API refer to the previous tutorials.

Now when MessageBox is called, it in turn will call a kernel function to display the message.

This is because only the kernel has access to the hardware components of the computer such as the display screen. Therefore when you pause Olly and Hit Alt-F9 your telling Olly to break after you hit Ok on the Message Box. Because you paused Olly once you hit Ok the kernel returns to Pixtopian and breaks just after the call to MessageBox.

For more Shortcuts always refer to the Olly Helpfile.

Okay. I admit it, this summary was rather on the short side, but that's because most of this tutorial is pretty self explanatory, and very little else was covered that was not covered in previous tutorials. The only other things covered in this tutorial were binary searching (already covered) and the Find References command, but since Lena wanted to save that one for later I don't think I should address it either. I think #4 was just to expose reversers to real applications. Don't worry if #4 was to get your feet wet, #5 is to get you knee deep in it, so enjoy this one while you can. and bring your game face for #5. Oh and congratulation on cracking your first real application!