Reverse Code Engineering RCE CD +sandman 2000/ReverseCodeEngineeringRceCdsandman2000.iso/RCE/+Sandman/lsoth2.asm

Assembly Source File | 2000-05-25 | 6KB | 256 lines

; Serial Number generator by Lord Soth. Version 1.0
; for ID crackme number 3.
; Any comments are welcome, but will be ignored :)
;-----------------------------------------------------------------
model compact
.data


querystr db 'Enter your soon to be registered name: $'
headline db 'Immortal Descendants CrackMe 3 serial number generator!$'
sernumstr db 'Your serial number is: $'
creditstr db 'Cracked and brought to you by Lord Soth!!$'
zerostr db 'ERROR: Zero length string.$'
username db 256 DUP (0)        ; max length of string that can be brought by a dialog box

str_out db 12 DUP (0)        ; length of final serial
ser_len dw 0000

.code
.startup
.386C

MOV AH,0
MOV AL,3
INT 10h                    ; set normal text video mode.
MOV AX,0625h            ; set 25 lines to scroll up
MOV BH,1Fh                ; set color attribute for blank chars
MOV CX,0000                ; set upper-left corner of window
MOV DX,184Fh            ; set lower-right corner of window
INT 10h                    ; fill screen with blue death :)

push ds
pop es
mov ah,13h
mov al,1
mov bh,0
mov bl,0eh
mov cx,37h
mov dx,0
mov ebp,offset es:headline        ; this will print the headline string..
int 10h

MOV Ah,3
MOV BH,0
INT 10h                            ; get cursor position

ADD DH,2                        ; go down 2 lines
MOV AH,2
MOV DL,0
PUSH DX
MOV BH,0
INT 10h                            ; set cursor on new position

POP DX
MOV AH,13h
MOV AL,1
MOV BX,1Fh
MOV CX,27h                        ; 39 chars to print
MOV EBP,offset ES:querystr        ; load offset of string
INT 10h                            ; print the damn string :)

; get the user name from the user, of course.. who did u think? :)

MOV CX,0FFh                        ; counter from 255 to 0 (bytes read)
mov bx,0                        ; pointer for memory
LEA DI,username

KBread:    MOV AH,0
    INT 16h                        ; get char from keyboard
    MOV BX,CX
    OR BX,0FF00h
    NOT BX                        ; BX will be used to point to the memory where char is stored
    CMP AH,1Ch                    ; check for Enter pressed
    JZ  CreateUserName             ; Bug outa here
    CMP AH,0Eh                    ; check for backspace
    JNZ store
    CALL delchar
    JMP Kbread

store:    MOV [DI+BX],AL             ; store ASCII byte in username buffer
        MOV AH,0Ah
        MOV BX,0
        PUSH CX                    ; store counter on stack
        MOV CX,1
        INT 10h                    ; print the char on screen
        MOV AH,3
        INT 10h                    ; get cursor position
        INC DL                     ; increase X pos by 1
        MOV AH,2
        MOV BH,0
        INT 10h                    ; set on new pos
        POP CX
        LOOP KBread                ; get another char (CX decreases)

; Create the REAL username the program has to calculate the serial from

CreateUserName :

NOT CL                            ; reversing CX makes it the string length
CMP CL,0                        ; if no chars, get outa here :)
JNZ contuser                    ;
JMP out_of_prog                    ; this is a fixed JMP, if your calculation routine is long
                                ; this might be needed

contuser:

MOV AX,0                        ; initailize to 0
LEA SI,username                    ; pointer to the username we entered
MOV CX,5                        ; 5 chars to process
MOV BX,0                        ; set BX to 0
LEA DI,str_out                  ; load target string offset into EDI :)

;Calculation of the serial number , those 4 little lines :)
calc:

MOV AL,[SI+BX]            ; get char
CALL num2str            ; turn it into an ASCII digit
INC BX                    ; next char
LOOP calc                ; all over again..

;Get string length and check against 10, which is max
LEA SI,str_out
MOV DI,SI
not_end:
INC SI
CMP BYTE PTR [SI],0                ; check for end of string
JNZ not_end
SUB SI,DI                        ; substract will give the length
CMP SI,0Ah                        ; compare to 10
JLE good_num                    ; if 10 or less, continue, this is a good number
MOV SI,0Ah                        ; if more than 10, set to 10, coz 10 is the max the prog uses..
good_num:
MOV WORD PTR [ser_len],SI            ; store length of serial number


    MOV AH,3
    MOV BX,0
    INT 10h                ; get cursor position
    ADD DH,2
    MOV DL,0
    MOV AX,1301h
    MOV BX,1Fh
    MOV CX,17h            ; 23 chars to print - "Your serial number...."
    MOV EBP,offset sernumstr
    INT 10h
    MOV AH,3
    MOV BX,0
    INT 10h                ; get cursor position
    MOV CX,WORD PTR [ser_len] ; get serial length
    MOV AX,1301h
    MOV BX,1Fh
    MOV EBP,offset str_out
    INC EBP
    INT 10h                ; print serial number
    MOV AH,3
    MOV BX,0
    INT 10h                ; get cursor position
    ADD DH,3            ; increase Y pos by 3
    MOV DL,0            ; X pos = 0, start of line
    MOV AX,1301h
    MOV BX,1Fh
    MOV CX,29h
    MOV EBP,offset creditstr
    INT 10h                ; print my name
    POP BP
    MOV AX,4C00h
    INT 21h                ; get da fuck outa here :)

out_of_prog :
    MOV AH,3
    MOV BX,0
    INT 10h                ; get cursor position
    MOV AX,1301h
    MOV DL,0
    ADD DH,3
    MOV BX,1Fh
    MOV CX,1Ah            ; 26 chars to print, "ERROR: Zero length..."
    MOV EBP,offset ES:zerostr
    INT 10h
    POP BP
    MOV AX,4C00h
    INT 21h                ; get outa here, no chars in username

delchar PROC near
    PUSH CX
    PUSH AX
    CMP BX,0
    JZ nochars
    MOV BYTE PTR [DI+BX],0        ; store null char on the buffer
    DEC BX                        ; reduce memory pointer by 1
    PUSH BX
    MOV BH,0
    MOV AH,3
    INT 10h                ; get cursor position
    DEC DL
    MOV AH,2
    MOV BH,0
    INT 10h                ; set it on X-1 pos
    MOV AX,0A20h        ; store "space" on screen pos
    MOV BX,0
    MOV CX,1
    INT 10H                ; write space on screen
    POP BX
    POP AX
    POP CX
    INC CX                ; increase CX, coz it normally decreases
                        ; and we want to go back 1 char
    RET                    ; return to caller

nochars:MOV BX,0        ; zero out BX, no chars to del
        POP AX
        POP CX            ; free stack
        MOV CX,0FFh        ; zero out counter, intial value is FFh
        RET
delchar    ENDP

num2str PROC near
        ; AX assumed to hold the 3 digit number
        ; BX used in indirection to put the ASCII in memory
        ; CX used to divide by 100, 10 etc.....

        PUSH CX
        MOV CX,64h            ; to divide by 100, find hundreds-digit
        CWD
        IDIV CX
        CMP AX,0
        JZ  zero_dig
        ADD AX,30h            ; add 30h to make it ASCII
        MOV [EDI],AL
        SUB AX,30h            ; return me to normal numbers
        INC EDI
zero_dig:MOV CX,0Ah
        MOV AX,DX
        CWD
        IDIV CX
         ADD AX,30h
        ADD DX,30h
        MOV [EDI],AL
        INC EDI
        MOV [EDI],DL
        INC EDI
        POP CX
        RET
num2str    ENDP

.exit
END