Cracking Projects For Newbies

Task 2 - Conclusion...Task Three Start. Saturday, 06-Feb-99 11:04:32 195.182.164.31 writes: Greetings Reverser's, Task 2 - Conclusion... ---------------------- Task 2 was an interesting exercise in using our Dead Listing to follow the in's and out's of our target program. As many of you are aware, there are many different ways to patch this program. Some good but buggy, and some, that while requiring a little more thought and consideration, work with no side-effects.. With Task Two I gently directed everyone to the location where the 'obvious' newbie patch could be seen, where the program branches out to display either 'Good Cracker' or the 'Beggar off Cracker' message. The obvious patch is not always the right one, as can be seen in some of the postings on this forum. Sometimes we have to dig a little deeper than we had originally planned and test our patches a few times before we can be sure of our work. No one is perfect, I've made these same mistakes too and will no doubt continue to make them..:) The CRC checks within this program are, to all intentional purposes, yet more left-over code from the win 3.1 version of the same program (very likely), or perhaps even left in the code to help scare off any 'newbies' peeking at the code (unlikely). Task 3 - Introduction Of all the possible ways we can crack a serial protected program, the best method has to be via entering a valid registration code into the program itself. From our point of view, as crackers, understanding 'how' the serial code is generated is far more enlightening to us then the actual serial code, because we can learn and apply this knowledge to our future cracks. If we are going to spend any time on a target program then it makes sense to learn as much as you can about it, for even the most simple of protection systems have something to offer us. It's now time to fire up Softice and let it loose on our target program. Because we've done our homework and mapped out this program carefully (see your notes!), we should have no problem knowing where to place our breakpoints and just as importantly, know what we are looking for. I am assuming here that everyone has taken the time to learn how to use and configure softice for themselves, because this project is primarily geared towards exploring different reversing techniques, rather than teaching you in any great depth on how to use Softice. If you are struggling with using/configuring Softice then I recommend that you follow the Softice link found at the top of this forum and download the tutorials found on this web page. Task 3 - Understanding The Serial Routine.. If you've read a number of tutorials on cracking then you should by now, be aware of certain patterns of code that seems to get repeated with increasing regularity. Going back to my Task 2 I directed everyone to the area of code where a conditional jump decides on which of the following 'Good Cracker', 'Bad Cracker' messages are displayed to the User when they enter their serial code. Lets take another look at this section of code: :0040B73A call 0040CCC0 :0040B73F add esp, 00000008 :0040B742 test eax, eax :0040B744 jne 0040B9BC Question 1. Explain as best you can, what the above code fragment does. Comment all four lines. I'm looking for your comments that:- a. Show what values of importance are returned in the PC's internal registers after the CALL 0040CCC0 has been executed. b. What is the reason for the ADD ESP, 00000008 instruction? BTW, register ESP is a STACK Register. c. The instruction TEST EAX,EAX is checking the eax register for two possible values, what are they and what do they signify? d. Where does the instruction JNE 0040B9BC take us to? Question 2. Explain how this program compares our *fake* serial number against the *real* one. (hint, check the code between :0040CCC0 to :0040CCF9 ) Question 3. Explain how our User Name: Pirate Copy is converted into a 16 character hex code. Good luck, The Sandman The Sandman

Message thread:

The Sandman: Task 2 - Conclusion...Task Three Start. (06-Feb-99 11:04:32)

Joseph: Re: Task 2 - Conclusion...Task Three Start. (08-Feb-99 03:55:57)

The Sandman: No Problem Joseph..:) (n/t) (08-Feb-99 18:06:42)

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