mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-24 07:58:36 +00:00
152 lines
6.3 KiB
NASM
152 lines
6.3 KiB
NASM
title DOORS.ASM - Switch Color/Mono Screens On Keyboard Request
|
||
;
|
||
VECTORS segment at 0h ; 8088 / 80286 Interrupt Vector Area
|
||
org 9h*4 ; IBM PC Keyboard is Int 9H
|
||
KB_INT_VECTOR label dword ; Double word label
|
||
;
|
||
VECTORS ends
|
||
;
|
||
ROM_BIOS_DATA segment at 40h ; Low Memory "BIOS" Parameters
|
||
;
|
||
org 10h ; Location of EQUIP_FLAG
|
||
EQUIP_FLAG dw ? ; Contains video settings
|
||
; in bits 4 and 5
|
||
;
|
||
org 17h ; Location of KB_FLAG
|
||
KB_FLAG db ? ; Contains Alt (bit 3) &
|
||
; Right Shift (bit 0) States
|
||
ROM_BIOS_DATA ends
|
||
;
|
||
; Initialization Routine
|
||
;
|
||
CODE_SEG segment
|
||
assume cs:CODE_SEG
|
||
org 100h ; COM program format
|
||
BEGIN: jmp SWAP_VECTORS ; Initialize vectors and attach to DOS
|
||
;
|
||
ROM_KB_INT dd 0 ; Double word to save address of
|
||
; ROM-BIOS keyboard interrupt
|
||
; DOORS_INT intercepts the keyboard interrupt and switches
|
||
; screens if [Alt]-[Right Shift] combination is pressed
|
||
;
|
||
DOORS_INT proc near
|
||
assume ds:nothing
|
||
push ds ; Push all affected registers
|
||
push es
|
||
push ax
|
||
push bx
|
||
push cx
|
||
push dx
|
||
push si
|
||
push di
|
||
;
|
||
pushf ; Push Flags for fake interrupt call
|
||
call ROM_KB_INT ; to BIOS program to read keyboard
|
||
;
|
||
assume ds:ROM_BIOS_DATA ; Define data segment to read
|
||
mov ax,ROM_BIOS_DATA ; keyboard flag & equipment flag
|
||
mov ds,ax
|
||
mov al,KB_FLAG ; Get keyboard flag
|
||
and al,09h ; Isolate [Alt] + [Right Shift]
|
||
cmp al,09h ; Are they pressed?
|
||
jne RETURN ; No, quit
|
||
;
|
||
; [Alt] + [Right Shift] are pressed -- Continue processing
|
||
; Check on video mode - quit if not monochrome, color 80x25 or BW 80x25
|
||
;
|
||
mov ah,15 ; Call Func 15 of Int 10h to
|
||
int 10h ; get video state of the PC
|
||
cmp al,7 ; Is screen monochrome?
|
||
je SCREEN_OKAY ; Yes, go switch screens
|
||
cmp al,3 ; Is screen color text?
|
||
jbe CHECK_40_OR_80 ; Yes, go check for 80 or 40 char
|
||
jmp RETURN ; Screen is in graphics mode, quit
|
||
CHECK_40_or_80:
|
||
cmp al,1 ; Is screen 40-character?
|
||
jbe RETURN ; Yes, quit
|
||
;
|
||
SCREEN_OKAY:
|
||
;
|
||
; Save the current cursor position
|
||
;
|
||
mov ah,3 ; Call Func 3 of Int 10H
|
||
mov bh,0 ; to read cursor position
|
||
int 10h ; (page zero for color screen)
|
||
;
|
||
; Screen switch routine - Establish calling argument (AL) for Int 10h
|
||
;
|
||
mov bx,EQUIP_FLAG ; Current equipment flag to BX
|
||
mov cx,bx ; Make a copy of it in CX
|
||
and cx,30h ; Extract screen information
|
||
xor bx,cx ; Erase current screen information in BX
|
||
or bx,20h ; Set BX to color 80x25
|
||
mov al,3 ; Set AL for color 80x25 in Int 10h
|
||
cmp cx,30h ; Is current mono?
|
||
je SET_MODE ; Yes, switch to color
|
||
or bx,30h ; No, set BX for monochrome
|
||
mov al,7 ; Set AL for monochrome in Int 10h
|
||
SET_MODE:
|
||
mov EQUIP_FLAG,bx ; Write BX to equipment flag
|
||
xor ah,ah ; Use Func 0 of Int 10h to
|
||
int 10h ; change screen parameters
|
||
;
|
||
; Restore Cursor
|
||
;
|
||
mov ah,2 ; Use Func 2 of Int 10h to restore
|
||
mov bh,0 ; cursor on new screen (position in DX)
|
||
int 10h
|
||
;
|
||
; After screens are switched, set DS and ES registers to move screen data
|
||
;
|
||
mov ax,0b000h ; Load ES with Mono Segment
|
||
mov es,ax
|
||
mov ax,0b800h ; Load DS with Color Segment
|
||
mov ds,ax
|
||
cmp cx,30h ; Did we switch from mono?
|
||
jne COPY_THE_SCREEN ; Yes, move data from mono to color
|
||
push ds ; No, swap ES and DS to move data
|
||
push es ; from color to mono
|
||
pop ds
|
||
pop es
|
||
COPY_THE_SCREEN:
|
||
xor di,di ; Start at zero offsets
|
||
xor si,si
|
||
mov cx,2000 ; 2000 chars + attrs per screen
|
||
cld ; Make sure move is 'forward'
|
||
rep movsw ; Move Words with string instruction
|
||
;
|
||
RETURN:
|
||
pop di ; Restore saved registers
|
||
pop si
|
||
pop dx
|
||
pop cx
|
||
pop bx
|
||
pop ax
|
||
pop es
|
||
pop ds
|
||
iret ; Return to system
|
||
|
||
DOORS_INT endp
|
||
;
|
||
; This procedure initializes the new keyboard interupt vectors
|
||
;
|
||
SWAP_VECTORS proc near
|
||
assume ds:VECTORS
|
||
mov ax,VECTORS ; Set up the data
|
||
mov ds,ax ; segment for vectors
|
||
cli ; Disable interrupts
|
||
mov ax,word ptr KB_INT_VECTOR ; Store addresses
|
||
mov word ptr ROM_KB_INT,ax ; of BIOS program
|
||
mov ax,word ptr KB_INT_VECTOR[2]
|
||
mov word ptr ROM_KB_INT[2],ax
|
||
mov word ptr KB_INT_VECTOR, offset DOORS_INT ; Substitute Our
|
||
mov word ptr KB_INT_VECTOR[2],cs ; Program
|
||
sti ; Enable interrupts
|
||
mov dx,offset SWAP_VECTORS ; End of new resident
|
||
; program
|
||
int 27h ; Terminate resident
|
||
SWAP_VECTORS endp
|
||
CODE_SEG ends
|
||
end BEGIN
|
||
;
|
||
|