CFF explorer has some built-in functionalities to calculate the MD5 and SHA-1 hashes of our sample. Sort the calls by Destination. This routine is called before our original break. Now it is time to do some modification in the binary code. Hit the “Copy all” button in the resulting dialog box as shown in Figure 24 and Figure 25. You should now be at the following lines: Looking at the code we see a test eax,eax followed by a jne 0041B54C. Smithsonian National Air and Space Museum. It is shareware and it is available here. Right click the 0x00401055 instruction inside the CPU window and select binary where click over. Now let’s remove our hardware breakpoint “Debug” -> “Hardware breakpoints” and delete it, and let’s place another hardware breakpoint at address 9ADBF4 so that we can break before this routine has run: Now you may wonder why I didn’t just put a regular breakpoint on this. Dependency Walker lists the DLL’s this sample relies on, and we can see that the sample was compiled with Visual Studio C++ 8, which is Visual Studio 2013. There are several hotkeys that you will find useful during your debugging session. This routine checks if we are registered or not and puts a zero in the memory address pointed to by [EAX+15B8] if it is not, and a 01 (or any non-zero) if it is. By attempting to defeat the copy protection of your application, we can learn a great deal about how roust the protection mechanism. We will need to rely on OllyDbg. So here’s what we do- highlight the two compare and jump instructions: Then right-click and choose “Binary” -> “Fill with NOPs”: This step isn’t required, but it makes it a lot easier to see what you’re doing. You can right-click on this window to disable or delete the breakpoints that have been set. With our tour of Olly behind us, we are now ready to start doing some real work: reversing and cracking a “trial” piece of software. This means that before the program even completely loads it is checking for the existence of a good serial. If it doesn’t fail, it leaves it alone. Note that many of the view menu items have hot-key commands. ( Log Out /  All we get is an error message when we attempt to execute it. The vendor stipulates a time restrictions condition over the beta software in order to be license misuse and permitting the product to run only in a reduced-functionality mode until the user registers. Click the plus sign in front of Software. The Windows window displays the Handle, Title, Parent Window, Window ID, Window Style, and Window Class Information for each window owned by the process. Note the yellow “Paused” message in the debuggee status. Instead, we are going to find a real serial. During this phase, we are looking for keywords, recognizable method calls, stuff like that. You can right-click on almost anything in OllyDbg to get a context menu to examine your many debugging options. After registering with a bogus serial it is unregistered the next time you start it up. We will learn many of Olly’s features while attempting to unlock a “trial” software whose trial time has expired. While in the Names window, you can right-click on any of these functions names to toggle a break point (Right-click -> “Toggle breakpoint” or press the F2 key). A familiar type of restriction built into software is copy protection which is normally forced by software vendor in order to test the robustness of software copy protection sachem. Figure 11: Debugging Options to Show Loops. We break again on the Recordings registry key so press Run again. There are also specialized tools for dealing with Delphi programs, but fortunately we do not need to use them in this tutorial (we will get to them though ). But Olly would not break on it. For example, if you see functions opening an internet connection and downloading files from an URL, the sample may be a downloader. Make sure “Case sensitive” is un-clicked and “Entire scope” IS clicked and hit OK: The first hit we get doesn’t seem to promising, so hit ctrl-L to go to the next occurrence: Notice that this occurrence is just the actual data of the first hit we had. Make sure the Hex option is checked and the Beginning of File option is checked. What we need to do is find where this is being set and make sure it doesn’t happen. We could scroll through this sample’s opcodes and look for the error message we encountered but that could be tedious if there are thousands of lines of code. The MSDN API documentation site ( is a useful resource in looking up these functions to learn what they do, the parameter’s these functions take in, and what these functions return. Clicking on the Log (Alt+L) option will bring up the Log Window. Finally, save the modified or patched binary with new name. If you need to do some trouble-shooting during your debugging session, the Log Window may be useful in tracking down unusual or unexpected behaviors while stepping through mal-code. Now load the modified program, you can that no expiration error message is shown. So if we make sure a 1 is put into that memory location every time this routine is run, then any other routines will check that memory location and see that it is a 1 and think that we’re registered.

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