REVERSE CODING
Welcome to my Reverse Coding tutorial! In this paper, you willlearn how to crack and modify your own software. I'll try to getinto as much detail as possible, yet also dumb it down a bit.
* All information is purely for educational purposes only! The authorcannot be held responsible for any (ab)use of this information.USE AT YOUR OWN RISK
To begin, I'm going to teach you about hexadecimal, so if you alreadyknow it, then move on. Even if you do already know it, I suggeststicking around for a refreshment of your memory.=)
Hexadecimal, or hex as it's more commonly known, is a base 16 numbering system. Base 16 meaning that it consists of 16 numbers:0-9 and A-F. Each of these numbers (A-F=10-16) have a value of 4 bitsand are also called nibbles. In representing a hexadecimal number, onewould write an "0x" before the actual bit set. 0x is simply a tag putbefore a hex number to let programmers know that it is in fact, hex.When writing hex, you will not need to use this prefix.
If you haven't already noticed, the 0x prefix looks similar to that of exponentialnotation. Actually this is where 0x has been derived, seeing as howhex is simply a number that has been raised to a power of 16.This means 10 in hexadecimal represents the value 16+0, or 16. So checkout this example:
0xB3 (hex)= 2*16(squared)+11*16(to the 1st power)+3*16(to the power of 0 )
=2*256+11*16+3=691 (decimal)
Yeah, you could do all of that, or you could be lazy and use an automatedprogram that does it all for you. Why do you need to know hex? Becauseit's used by every piece of software and hardware. How? Memory based addressallocation. Here's an example:
When you clicked on your browsers icon to launch it, the click triggered a "call"(an asm function that will be discussed more in depth in later chapters.) whichwent back to the programs memory with the "click in it'shand." It finds theaddress where the code is that makes the program launch and executes it. The
address is written in, you guessed it, hex. An example of an address would besomething like this:
101c5018
5108 would be the actual specific address and 101c would be the sectorof RAM were the address is located. Those are the basics of HexadecimalYou should probley read this chapter againbecause getting a firm grasp on hexis essential to cracking and moding programs.
***RAM and ROM***
In this section we are gonna learn about RAM and ROM. Many people kno aboutthe hardware part of RAM and ROM and that's gonna be very useful to you......just not in this tutorial. =) We are about to learn about the "software" side. I use theterm software loosly in that software tends to have a GUI (Graphical User Interface)and this does not. BUT, there are ways to access and modify the behavior of it thatI will talk about in this chapter, as well as in the next. To start off, I'll answer somecommon questions:
What is RAM?
RAM (Random Access Memory) is basically memory and the process of accessing it.The term "Random Access Memory" was approprietly given to this memory unit becausewhen executing a command, the CPU doesn't have to scroll through all the memory onyour PC until it finds the right address. It "randomly" whips out the addy from it's backpocket and serves it up.This process is both quick and efficient. Learning this processwill help you understand the ASM functions in the next chapter.
How does RAM work?
When a command is issued and the memory is pulled from file, it must first go throughwhat is called a "vector". A vector is a "gateway" or a "sector" of RAM where the addressof the function is stored with others of it's own kind. An example of a vector would besomething like this:
8c0000b4-8c00ffff
This means that all "addressii" (hehe) that are between those values are stored in thatsector of RAM. A vector acts as a gateway in that, first, pass through a vector to get toaddress. Your average program probley has about 30 to 40 main vectors, sectioningoff from boot until exit. Knowing the vector of an addy or a function will greatly reduceyour headache when you start searching for it.
ROM. ROM is a part of memory that doesn't change. (Although we can change it.=) )Boot ROM for instance, follows the same plan of action it is called upon. ROM also hasvectors, just like RAM. ROM is not that important when it comes to cracking to we will leave it alone for now.
Back to RAM. Believe it or not, but addressi actually follow certain formats or syntax's for certain functions. Take hot keys for example: In the under ground, we call them "Joker commands". By pressing a certain combonation of keys, a program will run, close, be stupid, whatever. The syntax for a Joker command is as follows:
0d-aaaaaf
000zvvvv
Let's examine this format a little closer.
0d= The proclemation of a specifyed format
aaaaa= The address of the function
f= The float or remainder; "Floating point number" ; decimal
000= "NOP" No operation
z= The "Booleon" as we the C++ programmers call it. A booleon is an "IF, THEN" statement. "IF this is true, THEN do this." Value 0= equal; 1= different; 2=less than; 3=greater than.
vvvv= The combonation of hex values (The values of the keys pressed) used to execute the "CALL"
Say the "A" key had a vlaue of fffb and the "B" key has a vlaue of fffd. You would then add both values using a hex calculator and get fff9 as the sum. The output on you calculator would show 1fff8. Add the first value and the last value to find the fourth byte segment. So say we've found the address of the Joker function (usually in the boot ROM sector) commonly called the "Maple address" and we are ready to program in some hex code. Our code may look like this:
0d7ae671
0000fff9
This means that IF the value of fff9 (A and B) is equal (0) to the address (aaaaf) of the function, THEN execute it. See? Easy isn't it? You'll need to know things like this when modding programs as a use of executing of your arbitrary code in certain parts of your program at a certain time. Joker commands are also reversable in that if you enter the same code except with a 1,2, or 3, in the z slot and by changing the button combonations. Reversable meaning terminating the function or other functions that were started. A good use for this is for firewalls and babysitting programs. Are you on a college machine and can't download stuff because of that pesky firewall? Crack it open and program in some Joker commands so you can turn it on and off at will WITHOUT the administrator's password!
***ASM***
To start off with our small and to the point ASM section, I'll warn you in advance, after reading this,
you'll need to go take a shower cause this is disgusting! Here we go!
To begin, I'm gonna define for you some functions that you'll be seeing alot of, and be using. Here they are:
.:Hex:. .:ASM:. .:MEANING:.
75,0f85 jne jump if not equal
74,0f84 je jump is equal
eb jmp jump directly to
90 nop no operation
77,0f87 ja jump if above
0f86 jna jump if not above
0f83 jae jump if above or equal to
0f82 jnae jump if not above or equal
0f82 jb jump if below
0f83 jnb jump is not below
of86 jbe jump if below or equal
0f87 jnbe jump if not below or equal
0f8f jg jump if greater
0f8e jng jump if not greater
0f8d jge jump if greater or equal
0f8c jnge jump if not greater or equal
0f8c jl jump if less
0f8d jnl jump if not less
0f8e jle jump if less or equal
0f8f jnle jump if not less or equal
The easy thing about most of the functions in ASM are that they sound like what they mean.
Jump, means of coarse, to Jump from one thing to another. Example:
"jmp 00401744" would mean to jump directly to the address 00401744 once the code
hits the function.
Let's look at "CALL". Call is a function that is used to "call" a certain task, string, address, whatever.
Take a look at this example:
"Call 0040ccc2" this would of coarse call the address 0040ccc2 and use it. Those are the functions
you'll be using.
you'll need to go take a shower cause this is disgusting! Here we go!
To begin, I'm gonna define for you some functions that you'll be seeing alot of, and be using. Here they are:
.:Hex:. .:ASM:. .:MEANING:.
75,0f85 jne jump if not equal
74,0f84 je jump is equal
eb jmp jump directly to
90 nop no operation
77,0f87 ja jump if above
0f86 jna jump if not above
0f83 jae jump if above or equal to
0f82 jnae jump if not above or equal
0f82 jb jump if below
0f83 jnb jump is not below
of86 jbe jump if below or equal
0f87 jnbe jump if not below or equal
0f8f jg jump if greater
0f8e jng jump if not greater
0f8d jge jump if greater or equal
0f8c jnge jump if not greater or equal
0f8c jl jump if less
0f8d jnl jump if not less
0f8e jle jump if less or equal
0f8f jnle jump if not less or equal
The easy thing about most of the functions in ASM are that they sound like what they mean.
Jump, means of coarse, to Jump from one thing to another. Example:
"jmp 00401744" would mean to jump directly to the address 00401744 once the code
hits the function.
Let's look at "CALL". Call is a function that is used to "call" a certain task, string, address, whatever.
Take a look at this example:
"Call 0040ccc2" this would of coarse call the address 0040ccc2 and use it. Those are the functions
you'll be using.
***Needed Programs***
DOWNLOAD
W32DASM 8.94
* Hiew 6.1
* Softice for v3.24
* SubmitWolf(demo)v4.01 http://www.trellian.com/swolf/
* Programming Language (C,C++,Pascal,ASM whatever you would like) Prefably C for this tutorial!
And a brain (no seriously)
***Cracking***
Ok, here we go! The first thing you need to do is to open up SoftIce and then swolf32.exe which is the name given to our
target program. Go to the help menu and select register. Here's where your brain will come in, start to look
for how the protection is running by entering some random crap into the blank space. Don't press the OK button yet though.
Instead, press CTRL-D to bring up SoftIce. What we are gonna try to do is define a breakpoint, using BPX hmemcpy.
Hit CTRL-D again and it will bring you back to the program. Click OK on the box and SoftIce will again pop up. Now press F12
and it will bring you to the target program code. Scroll down a few lines and find:
:004167D9 8D4C2410 lea ecx, dword ptr {esp+10}--;ecx=the random crap you typed in.
:004167DD 8D94290000000 lea edx, dword ptr {esp+00000090}-;edx=name
:004167E4 51 push ecx
:004167E5 52 push edx
:004167E6 E8B5450100 call 0042ADA0----;this is the call which calculates the serial
:004167EB 83C410 add esp, 00000010--;
:004167EE 85C0 test eax, eax----;and return eax=1 if true (booleon =) )
:004167F0 0F8596000000 jne 0041688C----;jump to registered
:004167F6 8D442408 lea eax, dword ptr {esp+08}
:004167FA 8D8C2488000000 lea ecx, dword ptr {esp+00000088}
:00416801 50 push eax
:00416802 51 push ecx
:00416803 E868470100 call 0042AF70----;this call tests our serial
:00416808 83C408 add esp, 00000008---;
:0041680B 85C0 test eax, eax----;for v3.XX one.
:0041680D 7433 je 00416842;jump is equal
The call that we want to focas on is at 004167E6. This call tests wether our serial is for the correct version or not.
Let's trace the call 004ADA0:
*Referenced by a CALL at address:
:0042ABFC
:0042ADA 83EC30 sub esp, 00000030
:0042ADA3 55 push ebp
:0042ASA4 56 push esi
:004ADA5 57 push edi
:0042ADA6 8B7C24444 mov edi, dword ptr {esp+44}--;edi=our fake serial
:004ADAA 85FF test edi, edi
:004ADAC 0F4A7010000 je 0042AF59----;die if empty
:004ADB2 8B6C2440 mov ebp, dword ptr {esp+40}--ebp=our name
:0042ADB6 85ED test ebp, ebp
:004ADB8 0F849B010000 je 0042AF59---;die if empty
:004ADBE 8A07 mov al, byte ptr {edi}--;compare 1st byte of serial with 'p', die
:0042ADC0 3C50 cmp al, 50----;
:0042ADC2 0F8587010000 jne 0042AF4F----;if not equal
:0042ADC8 807F0134 cmp byte ptr {edi+01}, 34--:compare byte of serial with '4'
:004ADCC 750C jne 0042ADDA----;
:0042ADCE C70500C8430000000000 mov dword ptr {0043C800}, 00000000
:0042ADD8 EB1C jmp 0042ADF6
As we can see by the above, the code tells us that the first value of our serial will
be 'p' and a cycle of a four byte algorythm. I could go on and on about all of the internals
of all this stuff but that would be going beyond the scope of this tutorial. The idea was to show
how to crack this pro, and thats what I'm going to do. Based on the information I've given you, and the
information that you can deduce from reading the code, I've written a small key generator in C.
If you know C, then you'll be able to tell where i got the algorythms to write it. So here it is:
Ok! So! An overall conclusion of this code is:
1.First two characters of the serial must be either 'PE' or 'P4'.
2.Multiply every first four characters or our name with every byte of our serial before '-'
3.XOR every four byte with every byte of our name.
4.Convert to positive number if<0.
5.Convert to number between 10000 and 1000000.
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