Assembler keygen tutorial
== ASM KEYGEN TUTORIAL - WRITTEN BY TERAPHY [PC97]
===================================================This is the tools i use in this tutorial:
- Soft-Ice 3.01
- W32Dasm 8.9 *Regged*
- Tasm/Tlink
Getting Started:
What we should do is to get the registration code, find where the code is being calculated and rip it out. I will use two easy programs as examples, Command Line 97 1.0, and Flywheel V1.02b.
Command Line 97 1.0:
(http://www.odyssey.net/subscribers/js01/index.html)
This program has a real simple code calculation. I will guide you step by step how to get the serial, how to rip it and how to make a working keygen.
1. Start the Program
2. Select Register
3. Go into Soft-Ice by pressing Ctrl-D, and set a breakpoint on GetDlgItemTextA. Type 'bpx getdlgitemtexta'. Now Press Ctrl-D again to get out from Soft-Ice.
4. Enter your name and a serial... I used 'TERAPHY' and '12345'
5. Press OK Button.. Soft-Ice will now show up inside the call to GetDlgItemTextA. Press F11 to get out of that call.
Scroll up a bit and u will see this
:0040254B 6A1E push 0000001E
:0040254D 68300B4100 push 00410B30
:00402552 68F0030000 push 000003F0
:00402557 56 push esi
:00402558 FF1550234100 Call [USER32!GetDlgItemTextA]The memory location being pushed at 40254D is where your name is stored. Type 'd 410B30', and you should see your name.
Below this you'll see
:0040255E 6A00 push 00000000
:00402560 BF300B4100 mov edi, 00410B30
:00402565 6A00 push 00000000
:00402567 68FC030000 push 000003FC
:0040256C 56 push esi
:0040256D FF1518234100 Call [USER32!GetDlgItemInt]Step until you reach 40256D. The call to Getdlgitemint returns what you typed in as serial in eax. Type '? eax' and you will see this '00003039 0000012345 "09"'. 3039 is 12345 in hex. Also notice :00402560. This command moves the offset of your name into edi.
Below this, you will see
:00402573 B9FFFFFFFF mov ecx, FFFFFFFF
:00402578 A354A54000 mov dword ptr [0040A554], eax
:0040257D 2BC0 sub eax, eax
:0040257F F2 repnz
:00402580 AE scasb
:00402581 F7D1 not ecx
:00402583 49 dec ecx:00402578 saves your code for later use.
The rest of the code is used to calculate the string length of your name... After this has been executed ecx contains the length of your name. In my case '7'.
Below this, you'll see
:00402584 0FBE05300B4100 movsx eax, byte ptr [00410B30]
:0040258B 0FAFC8 imul ecx, eax
:0040258E C1E10A shl ecx, 0A
:00402591 81C1CCF80200 add ecx, 0002F8CC
:00402597 890D50A54000 mov dword ptr [0040A550], ecx
:0040259D 390D54A54000 cmp dword ptr [0040A554], ecx:00402584 moves the byte of the first letter to eax. In my case 54('T'). The next line multiplys eax (54), with ecx (7). shl ecx, 0A means multiply ecx with 2^10.
And finnaly we add 02F8CC to ecx.
At :0040259D the registration code is compared with what we typed in, remember it moved our code to [0040A554].
Type '? ecx' and you can see your real code.
But we don't just want the code, do we?
Leave SoftIce and exit Command Line 97.
6. Start W32Dasm, and dissasemble cline97.exe Save dissasembly to file and exit.
7. Now we are going to build the keygen itself. Start your favorite texteditor and enter this code.
Code Segment Byte Public
Assume Ds:Code,Cs:Code
Org 100h
P386 ; this enables 386 instructions
and 32bit registers
Start:
mov ah,09
mov dx,offset Intro
int 21h ; Show intro msg
mov ah,0Ah
mov dx,offset Namesto
int 21h ; Get nameNow load the dissasembly (cline97.alf) into your texteditor.
Goto :00402573. Copy all code from here down to :00402591, and paste it into your asm source.
It will look like this
:00402573 B9FFFFFFFF mov ecx, FFFFFFFF
:00402578 A354A54000 mov dword ptr [0040A554], eax
:0040257D 2BC0 sub eax, eax
:0040257F F2 repnz
:00402580 AE scasb
:00402581 F7D1 not ecx
:00402583 49 dec ecx
:00402584 0FBE05300B4100 movsx eax, byte ptr [00410B30]
:0040258B 0FAFC8 imul ecx, eax
:0040258E C1E10A shl ecx, 0A
:00402591 81C1CCF80200 add ecx, 0002F8CCNow you can start ripping. You should remove everything except the command itself. The line :00402578 is obviously not needed, because it saves the inputed regcode for later use, and our keygen does not prompt for regcode, it calculates =)
The source in your program should look like this.
mov ecx, FFFFFFFF
sub eax, eax
repnz
scasb
not ecx
dec ecx
movsx eax, byte ptr [00410B30]
imul ecx, eax
shl ecx, 0A
add ecx, 0002F8CCIf you remember, it moved the offset of Name into edi earlier.
So we need to add this before mov ecx, FFFFFFFF
xor edi,edi
mov di, offset Namesto+2 ; this must be +2, becaue that's there
; the actuall name begins.The command mov ecx, FFFFFFFF can't be compiled this way, so we have to change it to mov ecx, 0FFFFFFFFh.
movsx eax, byte ptr [00410B30] is not valid either, because our name isn't on [00410B30]. This could be changed to
xor edi,edi
mov di, offset Namesto+2
movsx eax, byte ptr [edi]Both 'shl ecx, 0A' and 'add ecx, 0002F8CC' needs to be changed to valid hex format: 'shl ecx, 0Ah' and 'add ecx 2F8CCh'
We now have a source that should look like this
xor edi,edi
mov di,offset Namesto+2
mov ecx, 0FFFFFFFFh
sub eax, eax
repnz
scasb
not ecx
dec ecx
xor edi,edi
mov di,offset Namesto+2
movsx eax, byte ptr [edi]
imul ecx, eax
shl ecx, 0Ah
add ecx, 2F8CChafter the dec ecx, we need to add another dec ecx, because when we enter our name, the last char will not be, in my case, 'y', it will be 0Dh, the enter key. This function, as it is, will return, in my case, ecx=8, not ecx=7 as it should be.
movsx eax, byte ptr [edi] moves the ascii code of the first letter to eax. But, what if the user enters a name with a small letter? The input box in Command Line 97 automaticly makes it capital letters. This could be fixed by adding this code below movsx eax, byte ptr [edi].
cmp eax, 061h ; compare eax with 61h (a)
jb capital ; jump if below
cmp eax, 07Ah ; compare eax with 7Ah (z)
ja capital ; jump if above
sub eax,20h ; convert char to capital
capital:Our code now looks like
Code Segment Byte Public
Assume Ds:Code,Cs:Code
Org 100h
P386 ; this enables 386 instructions
and 32bit registers
Start:
mov ah,09
mov dx,offset Intro
int 21h ; Show intro msg
mov ah,0Ah
mov dx,offset Namesto
int 21h ; Get name
xor edi,edi
mov di,offset Namesto+2
mov ecx, 0FFFFFFFFh
sub eax, eax
repnz
scasb
not ecx
dec ecx
dec ecx
xor edi,edi
mov di,offset Namesto+2
movsx eax, byte ptr [edi]
cmp eax, 061h
jb capital
cmp eax, 07Ah
ja capital
sub eax,20h
capital:
imul ecx, eax
shl ecx, 0Ah
add ecx, 2F8CChWhat we need now is a routine to show the serial.
We know that the serial is the decimal value of ecx.
xor esi,esi
mov si,offset Serial+9 ; esi is the offset there the
; regnumber will be stored
mov eax,ecx ; eax should be reg number
mov ecx,0Ah
KeepGoing:
xor edx,edx
div ecx
add dl,30h
cmp dl,3Ah
jl printnow
add dl,7
printnow:
dec esi
mov [esi],dl
or eax,eax
jnz keepgoingAfter this serial contains the registration code.
You don't really need to understand this code. It can be used by any keygen there the code is the decimal value of a register.
The only thing left to do is to add the command that's writes this to screen.
mov ah, 9
mov dx, offset RegPrompt
int 21hAnd finally quit.
int 20hThe full source should look like this
; COMMAND LINE 97 *KEYGEN*
; CODED BY TERAPHY [PC97]
Code Segment Byte Public
Assume Ds:Code,Cs:Code
Org 100h
P386 ; this enables 386 instructions
; and 32bit registers
Start:
mov ah,09
mov dx,offset Intro
int 21h ; Show intro msg
mov ah,0Ah
mov dx,offset Namesto
int 21h ; Get name
xor edi,edi
mov di,offset Namesto+2
mov ecx, 0FFFFFFFFh
sub eax, eax
repnz
scasb
not ecx
dec ecx
xor edi,edi
mov di,offset Namesto+2
movsx eax, byte ptr [edi]
cmp eax, 061h
jb capital
cmp eax, 07Ah
ja capital
sub eax,20h
capital:
imul ecx, eax
shl ecx, 0Ah
add ecx, 2F8CCh
xor esi,esi
mov si,offset Serial+9
mov eax,ecx
mov ecx,0Ah
KeepGoing:
xor edx,edx
div ecx
add dl,30h
cmp dl,3Ah
jl printnow
add dl,7
printnow:
dec esi
mov [esi],dl
or eax,eax
jnz keepgoing
mov ah, 9
mov dx, offset RegPrompt
int 21h
int 20h
Intro db 13,10,'COMMAND LINE 97 *KEYGEN*'
db 13,10,'CODED BY TERAPHY [PC97]',13,10
db 13,10,'Enter your name: $'
RegPrompt db 13,10,'Your registration key is: '
Serial db 0,0,0,0,0,0,0,0,0,0,13,10,24h
Namesto db 18h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
Code Ends
End Start8. Compile the code with tasm.
tasm keygen.asm
tlink /t keygen.asmYou must link with the /t option for the keygen to run, it makes it a com file.
9. Congratulations! You have just made your first(?) keygen!
Flywheel V1.02b
1. Start the Program
2. Select Register
3. Go into Soft-Ice by pressing Ctrl-D, and set a breakpoint on GetDlgItemTextA. Type 'bpx getdlgitemtexta'. Now Press Ctrl-D again to get out from Soft-Ice.
4. Enter your name ('TERAPHY') and any serial ('12345'). Press OK button, and Soft-Ice will show up.
Scroll up a little bit and you'll see this
:00402ACD 8D4C242C lea ecx, [esp+2C]
:00402AD1 66AB stosw
:00402AD3 6800010000 push 00000100
:00402AD8 51 push ecx
:00402AD9 6A65 push 00000065
:00402ADB 56 push esi
:00402ADC AA stosb
:00402ADD FF151C154100 Call [USER32!GetDlgItemTextA]The important adress is there your name is being pushed, and that is push ecx. ecx got is value from 'lea ecx,[esp+2C]'. Type 'd esp+2c', and you should see your name.
Below is a call to GetDlgItemInt, and as you remember it returns the inputed value to eax. Type '? eax' to see the serial you wrote.
Below this, you'll see this
:00402AF3 8D54242C lea edx, [esp+2C]
:00402AF7 50 push eax
:00402AF8 52 push edx
:00402AF9 E8D2F9FFFF call 004024D0
:00402AFE 83C408 add esp, 00000008
:00402B01 85C0 test eax, eax'lea edx,[esp+2C]' moves the offset of your name into edx, and then it pushes to stack. And eax contains our serial. And after the call it tests if eax is true or false. This call is there the registration code is being calculated.
We trace into it. Step past the first instructions until you reach
:004024EF B81F85EB51 mov eax, 51EB851F
:004024F4 F7E7 mul edi
:004024F6 C1EA05 shr edx, 05
:004024F9 52 push edx
:004024FA 56 push esi
:004024FB E8B0000000 call 004025B0004024EF - 004024F6 makes edx all digits except the two last of what we typed in as serial. If you wrote '12345' edx will be '123', and if you wrote '072597' edx will be '0725'.
Then it pushes edx and esi. esi is the offset to your name. Trace into the call. Step past a few instructions until you reach
:004025B8 8A06 mov al, byte ptr [esi]esi contains the offset to your name, so this instruction moves the ascii code of the first letter to al, in my case '54'
:004025BA 84C0 test al, al
:004025BC 7426 je 004025E4This instrucions checks if we have inputed any name, if not it jumps.
:004025BE 0FBEC0 movsx eax, alThis instrucion moves al, to eax. If eax = FFFFFF54, after this eax would have been 00000054
:004025C1 50 push eax
:004025C2 E889140000 call 00403A50At a first look this call only moves the eax value to ecx. But it does also check for a space (20h) in eax. It returns false if not a space.
:004025C7 83C404 add esp, 00000004This code changes the stack and should be ignored
:004025CA 85C0 test eax, eax
:004025CC 750E jne 004025DCTest if a space was found. Jump if found.
:004025CE 0FBE0E movsx ecx, byte ptr [esi]This moves the letter into ecx (there it should already be).
:004025D1 51 push ecx
:004025D2 E8E9120000 call 004038C0If you, as in my case, wrote your name with a capital letter, this call will return eax = ascii code for your letter + 20h.
This means it has been converted to a small letter.
:004025D7 83C404 add esp, 00000004Ignore this
:004025DA 03F8 add edi, eaxAdd edi, eax. Eax is the value of our char as small letter.
:004025DC 8A4601 mov al, byte ptr [esi+01]
:004025DF 46 inc esiMoves the value of the next char into al
:004025E0 84C0 test al, al
:004025E2 75DA jne 004025BETest if al is 0. This means the end of our name has been reached.
Jump if al is not 0.
What this code has done, as you probably already figured out, is add the ascii value of all chars into edi. Except spaces (20h). It has also converted all capital chars into small letters.
:004025E4 8B4C2410 mov ecx, [esp+10]This moves what we typed in (except the last two digits) into ecx
:004025E8 8D14BF lea edx, [edi+4*edi]
:004025EB 2BCF sub ecx, edi
:004025ED 8D1457 lea edx, [edi+2*edx]
:004025F0 85D2 test edx, edx
:004025F2 740F je 00402603
:004025F4 B8ABAAAAAA mov eax, AAAAAAAB
:004025F9 F7E2 mul edx
:004025FB D1EA shr edx, 1
:004025FD 81C204060200 add edx, 00020604
:00402603 33C0 xor eax, eax
:00402605 3BCA cmp ecx, edxThis code checks if you typed in the right number. At 402605 the compare is made. But ecx is no longer what we wrote as serial, because of the 'sub ecx,edi' command. We could make a simple equation of this.
Assume X is our registration code (except the two digits).
'X - EDI = EDX'Now type '? edx+edi' and, in my case, I'll get '136182' as decimal value. This is my regcode, except the two last digits. These digits could be anything. Now then we know my registration code is '13618200', we can start on the keygen.
5. Run W32Dasm and dissasemble flywheel.exe (the file is located in 'C:\Program Files\Plannet Crafters\Flywheel') Save the dissasembly to disk and quit.
6. Now it's time to start on the code. We can use the same start as in the last keygen. We go directly to the ripping part.
You can start by copy all code from 4025B8 to 402605 into your program.
That will look like this.
:004025B8 8A06 mov al, byte ptr [esi]
:004025BA 84C0 test al, al
:004025BC 7426 je 004025E4
:004025BE 0FBEC0 movsx eax, al
:004025C1 50 push eax
:004025C2 E889140000 call 00403A50
:004025C7 83C404 add esp, 00000004
:004025CA 85C0 test eax, eax
:004025CC 750E jne 004025DC
:004025CE 0FBE0E movsx ecx, byte ptr [esi]
:004025D1 51 push ecx
:004025D2 E8E9120000 call 004038C0
:004025D7 83C404 add esp, 00000004
:004025DA 03F8 add edi, eax
:004025DC 8A4601 mov al, byte ptr [esi+01]
:004025DF 46 inc esi
:004025E0 84C0 test al, al
:004025E2 75DA jne 004025BE
:004025E4 8B4C2410 mov ecx, dword ptr [esp+10]
:004025E8 8D14BF lea edx, dword ptr [edi+4*edi]
:004025EB 2BCF sub ecx, edi
:004025ED 8D1457 lea edx, dword ptr [edi+2*edx]
:004025F0 85D2 test edx, edx
:004025F2 740F je 00402603
:004025F4 B8ABAAAAAA mov eax, AAAAAAAB
:004025F9 F7E2 mul edx
:004025FB D1EA shr edx, 1
:004025FD 81C204060200 add edx, 00020604
:00402603 33C0 xor eax, eax
:00402605 3BCA cmp ecx, edxHere is how I would have ripped this into the program, with comments.
; THIS REPLACES 4025BE - 4025E2
xor ecx,ecx
xor edi,edi
mov di, offset NameSto+2 ; Mov the offset of your name
; into edi
anotherchar:
movsx eax, byte ptr [di] ; Get char from [di]
cmp eax, 20h ; Compare your letter with 20h
je space ; Jump if equal
cmp eax, 041h ; Compare your letter to see
jb capital ; if it's already is a
cmp eax, 05Ah ; small lettter
ja capital
add eax,20h ; If capital char, add 20h to make
; it a small letter.
capital:
add ecx, eax ; add eax to ecx, if not space
space:
inc di ; inc di to make it point to the
; next char.
cmp byte ptr [di], 0dh ; Compare next char with 0Dh (return)
; Remember then we get our name, it
; ends with a 0Dh
jne anotherchar ; Jump if not 0Dh
mov edi, ecx
; CODE BELOW REPLACES 4025E2 - 402603
; All commands with ecx (our inputed code) is not needed
; because we do not input any code.
xor edx,edx
lea edx, [edi + 4*edi]
lea edx, [edi + 2*edx]
mov eax, 0AAAAAAABh
mul edx
shr edx, 1
add edx, 20604h
xor ecx, ecx ; Here we do our equation
add ecx, edx ;
add ecx, edi ; ecx = edx + ediAfter this, ecx contains the regcode.
The complete source could look like this.
Code Segment Byte Public
Assume Ds:Code,Cs:Code
Org 100h
P386
Start:
mov ah,09
mov dx,offset Intro
int 21h ; Show intro msg
mov ah,0Ah
mov dx,offset Namesto
int 21h ; Get name
xor ecx,ecx
xor edi,edi
mov di, offset NameSto+2
anotherchar:
movsx eax, byte ptr [di]
cmp eax, 20h
je space
cmp eax, 041h
jb capital
cmp eax, 05Ah
ja capital
add eax,20h
capital:
add ecx, eax
space:
inc di
cmp byte ptr [di], 0dh
jne anotherchar
mov edi, ecx
xor edx,edx
lea edx, [edi + 4*edi]
lea edx, [edi + 2*edx]
mov eax, 0AAAAAAABh
mul edx
shr edx, 1
add edx, 20604h
xor ecx, ecx
add ecx, edx
add ecx, edi
xor esi,esi
mov si,offset Serial+9
mov eax,ecx
mov ecx,0Ah
KeepGoing:
xor edx,edx
div ecx
add dl,30h
cmp dl,3Ah
jl printnow
add dl,7
printnow:
dec esi
mov [esi],dl
or eax,eax
jnz keepgoing
mov ah, 9
mov dx, offset RegPrompt
int 21h
int 20h
Intro db 13,10,'FLYWHEEL 1.2 *KEYGEN*'
db 13,10,'CODED BY TERAPHY [PC97]',13,10
db 13,10,'Enter your name: $'
RegPrompt db 13,10,'Your registration key is: '
Serial db 0,0,0,0,0,0,0,0,0,'0','0',13,10,24h
Namesto db 18h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
Code Ends
End StartNow compile, run and enjoy! :)
==================
= TERAPHY [PC97] =
= 07/25/1997 =
==================
