Tulisan Dasar Cracking
Selamat Datang.................Cracker..........     CO.CC:Free Domain
Tutorial Cracking :

Aeria Leech v1.00

Aeria Leech v1.00. You can download it from : http://www.aeria.com/leech

Let's get going ;-)

Step 1: Run the program:
Run it. In the help menu you have the option to register.
Enter any number and press ok.
You get an error message : The key is not a valid license key for this product.
Ok. Let's go on to the next step :)

Step 2: Disassemble the program:
Disassemble, and look for the string you see above.
Found.
This string reference brings us to the next step.

Step 3: Analyzing the protection routine.... / Understanding the jumping Mechanism...
Let's analyze the protection routine.

////////////////////// Code snip ///////////////////////////
ADDRESS MACHINE CODE ASSEMBLER INSTRUCTIONS

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:00405E11(C)
|
:00405F28 E86F8C0300 call 0043EB9C
:00405F2D 8B4004 mov eax, dword ptr [eax+04]
:00405F30 6A10 push 00000010

* Possible StringData Ref from Data Obj ->"Invalid License Key"
|
:00405F32 6808844500 push 00458408

* Possible StringData Ref from Data Obj ->"The key is not a valid license "
                                                               ->"key for this product."
|
:00405F37 68D0834500 push 004583D0
////////////////////// Code snip ///////////////////////////


Well ... This piece of code sure looks familiar :-)
This code is reached after a jump at address : 405E11. The reference shows that.
Let's go back to address 405E11.


////////////////////// Code snip ///////////////////////////
ADDRESS MACHINE CODE ASSEMBLER INSTRUCTIONS

:00405E04 83C408 add esp, 00000008
:00405E07 E864380000 call 00409670
:00405E0C 83C404 add esp, 00000004
:00405E0F 84C0 test al, al
:00405E11 0F8411010000 je 00405F28
////////////////////// Code snip ///////////////////////////


This jump at address 405E11 jumps over all the piece of code that tells us that we are
registered. So nopping this jump away would make us display the nice registered dialog box :-)
But luckily we worked through the previous tutorial. and we first try to analyze this code.


////////////////////// Code snip ///////////////////////////
call 409670 ; isregistered ?
test al, al ; result of the call is in eax :-)
; ( al is the lower part of eax, not important now)
je ; if eax = 0 then jump ! if eax is 1 don't jump !
////////////////////// Code snip ///////////////////////////

Well ... this code is clear not ?
The call checks the entered serial. And if the serial is ok, it returns 1 in eax, else it returns a zero
in eax.
Let's trace into the call at address 409670.


////////////////////// Code snip ///////////////////////////
ADDRESS MACHINE CODE ASSEMBLER INSTRUCTIONS

* Referenced by a CALL at Addresses:
|:004014BF , :00405E07
|

* Possible Reference to Dialog: DialogID_00CB, CONTROL_ID:00FF, ""
|
:00409670 6AFF push FFFFFFFF
:00409672 68F8424400 push 004442F8
:00409677 64A100000000 mov eax, dword ptr fs:[00000000]
////////////////////// Code snip ///////////////////////////

And yes ... We were right :-)
This call is referenced twice. Once at startup and once while entering the serial :-)


Step 4: Changing the original program...

Since we analyzed the jumping mechanism carefully, we can change the original program.
Open the program in hiew after making a backup copy of it.
Get to the beginning of the call at address 409670.

Change the beginning of the call into the following :
////////////////////// Code snip ///////////////////////////

mov eax, 1 ; 1 means serial is ok
ret ; return to the caller.
////////////////////// Code snip ///////////////////////////

It will look like the following:

////////////////////// Code snip ///////////////////////////
ADDRESS MACHINE CODE ASSEMBLER INSTRUCTIONS
00009670: B801000000 mov eax,000000001
00009675: C3 retn
00009676: 0064A100 add [ecx][00000],ah
////////////////////// Code snip ///////////////////////////


Save your patched program and exit hiew.

Step 5: Testing your cracked program...
Run Leech. It will still tell you that you are unregistered in the about box.
Register it with any number, and it will happily accept your serial :-)

Do not forget to close the program and restart it. You will see that it is still happy with the
provided serial :-)

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