; page 66,132 ; ;KYLOCK.ASM for the IBM PC/XT & PCJR - 1987 by Ocean ; ;This is part 2 of a 2 part utilities set consisting of ----------------------- ;SCRNOFF3.ASM & KYLOCK.ASM. -----------------------THEY MUST BE USED TOGETHER! ; ----------------------- ; kb_data equ 60h ;keyboard data port kb_ctrl equ 61h ;keyboard control port k_key equ 37 ;scan code of k key o_key equ 24 ;scan code of o key del_key equ 83 ;scan code of Del key ins_key equ 82 ;scan code of Ins key alt_key equ 8 ;shift code for Alt key ctrl_key equ 4 ;shift code for Ctrl key eoi equ 20h ;end-of-interrupt signal int_ctrl_port equ 20h ;8259 interrupt controller port ; code segment para public 'code' assume cs:code org 0 seg_org equ $ ; bios_data segment at 40h ;bios data area org 063h addr_6845 dw ? ;define location that holds ;word address of active display org 065h crt_mode_set db ? ;define location that holds ;byte loaded into pc active ;display port or pcjr's vga bios_data ends ; org 0100h begin: jmp initialize ;goto initialization routine ; adapter db 0 ;0 = EGA, 1 = CGA or MDA, and ;2 = PCJR pcjr_mode db ? ;current setting of PCJR video pc_mode db ? ;current setting of 6845 mode ;control register of the pc kylock_status db 0 ;interrupt routine status flag char_count dw ? ;length of password hotky_val db 00h,44h,2fh,2eh,2dh ;hotkey make scan code table - db 20h,1eh,16h,11h ;filler,F10,v,c,x,d,a,u, and w msr_address dw ? ;address of mode select register pcjr_signature db 0fdh ;PCJR BIOS signature ibm_signature db 'IBM' ;EGA BIOS signature errmsg db 13,10,'KYLOCK ALREADY LOADED!',13,10,'$' ; old_int_9h label dword ;holding area for INT 9h vector int_9h_ptr dw 2 dup (?) old_int_16h label dword ;holding area for INT 16h vector int_16h_ptr dw 2 dup (?) old_int_5h label dword ;holding area, INT 5h vector int_5h_ptr dw 2 dup (?) ; ;------------------------------------------------------------------------------ ;All calls to INT 5 will henceforth be routed thru here. On the PCJR, the ;Print Screen Function is processed by INT 48h (This interrupt translates the ;PCJR 62 key keyboard scan codes to be compatible with the 83 key keyboard of ;the PC and then INT 9 occurs.) which activates INT 5 before INT 9 is called. ;To insure that a copy of the screen cannot be printed out on the PCJR while ;the keyboard is supposedly locked, therefore, requires that the bios print ;screen service be intercepted and nulled while KYLOCK is active. ;------------------------------------------------------------------------------ ; new_int_5h proc near test kylock_status,01 ;kylock routine active? jnz print_not ;yes, block PRTSCR function jmp old_int_5h ;no, goto normal INT 5h handler print_not: iret ;exit, nulling INT 5h new_int_5h endp ; ;------------------------------------------------------------------------------ ;All calls to INT 16h will henceforth be routed thru here. If ah = 255 on ;entry, bh is set to 255 to signal the caller that this routine was indeed ;invoked. ;------------------------------------------------------------------------------ new_int_16h proc near cmp ah,255 ;ah = 255? jne newint1 ;no, then jump mov bh,ah ;yes, set bh to 255 and exit iret newint1: jmp old_int_16h ;goto normal 16h handler new_int_16h endp ; ;------------------------------------------------------------------------------ ;Execution comes here every time an interrupt 9 is generated from the keyboard. ;------------------------------------------------------------------------------ ; kylock proc near sti ;restore interrupts push ax ;save registers push bx push cx push dx push si push di push ds push es in al,kb_data ;read keypress (or break) cmp kylock_status,0 ;kylock routine active? je kylock0 ;no, then check for Alt-O/Alt-K ; ;The kylock routine is already in progress. Check for a press of one of the ;POPUP DESKSET "hot-keys" and block it out if it just occured. (This routine ; may be omitted if this program is not used with POPUP DESKSET.) ; and al,7fh ;strip the break bit mov dl,al ;load keypress make scan code mov cx,8 ;number of hotkeys to check lea bx,hotky_val ;address of table of hotkeys next1: mov ax,cx ;sequential pointer to hotkey xlat hotky_val ;load value of hotkey to al cmp dl,al ;keypress match this "hotkey"? jne loop ;no, how about next one? mov ah,2 ;yes, get shift status int 16h ; cmp al,alt_key ;alt pressed? jne exit1 ;no, goto old int 9 routine call kb_reset ;alt-"hotkey" pressed; reset kb jmp unlck1 ;exit loop: loop next1 ;get next value from table mov al,dl ;no match - continue ; ;The kylock routine is already in progress. Check for a press of Ctrl-Alt-Del ;or Ctrl-Alt-Ins (On the PCJR, this combination invokes diagnostic routines ;from which a Ctrl-Alt-Del can reset the machine.) and block it out if it just ;occurred. ; cmp al,ins_key ;was Ins Key pressed? je sh_stat ;get shift status cmp al,del_key ;was the Del key pressed? jne exit1 ;no, goto old INT 9 routine sh_stat: mov ah,2 ;Int 16h - get shift status int 16h ;get status of shift keys and al,alt_key+ctrl_key ;ctrl-alt pressed? cmp al,alt_key+ctrl_key jne exit1 ;no, goto old int 9 routine call kb_reset ;ctrl-alt-del press - reset kb jmp unlck1 ;exit ; ;The kylock routine is not already active. If Alt-O was pressed, toggle timer ;on/off, then block it out. ; kylock0: cmp al,o_key ;o key pressed? jne strp_brk ;no, jump mov ah,2 ;yes, get shift status int 16h test al,alt_key ;Alt pressed when o key press? jnz toggle ;Alt-o key press --- toggle jmp strp_brk ;Alt-o key not pressed --- jump ; ;Int 16h is called here with ah set to 158. Int 16h is a chained interrupt ;hooked into by SCRNOFF3. When it is SCRNOFF3's turn in the chain, it tests ;the value of the register AH. If it has been set to 158, then it toggles its ;timer on/off. ; toggle: mov ah,158 ;Place 158 into AH int 16h ;Call INT with AH set to 158 call kb_reset ;reset kybrd, throw away alt-o jmp unlck1 ;exit, skip normal kybrd route strp_brk: and al,7fh ;strip the break bit ; ;The kylock routine is not already active. See if Alt-K was pressed. ; cmp al,k_key ;is it the k key? jne exit ;no, goto old int 9 routine mov ah,2 ;int 16h - get shift status int 16h test al,alt_key ;is the alt key pressed? jne kylock2 ;yes, goto kylock routine ; ;Exit routine restores registers and, if screen is blanked, enables the video ;& resets count before exiting thru normal keyboard interrupt handler. ; exit: pop es ;pop registers off stack pop ds pop di pop si pop dx pop cx pop bx pop ax ; ;Call user interrupt 4dh (created by scrnoff3.com) to unblank screen if the ;timer within scrnoff3.com is 0. ; int 4dh ;user interrupt 4dh jmp old_int_9h ;exit to normal interrupt ;handler ; ;Exit1 routine restores registers before exiting thru normal keyboard interrupt ;handler and bypasses video enable and count reset routines since kylock is in ;progress. ; exit1: pop es ;pop registers off stack pop ds pop di pop si pop dx pop cx pop bx pop ax jmp old_int_9h ;exit to normal interrupt ;handler ; ;Trigger keys are pressed. Reset the keyboard, send an EOI signal to the 8259, ;and execute our kylock routine. ; kylock2: call kb_reset ;reset keyboard and issue EOI mov kylock_status,1 ;set status byte push cs ;set ds and es to the code ;segment pop ds push cs pop es assume ds:code ; ;Begin kylock routine by disabling video and getting a password from the user. ; call video_disable ;disable video display xor di,di ;point DI to start of PSP call get_password ;get the password or cx,cx ;any characters input? je unlock ;no, exit this interrupt cmp al,27 ;was input terminated with ESC je unlock ;yes, then exit mov char_count,cx ;save length of password ; ;The password is now entered and the keyboard 'locked', awaiting input of a ;matching password. Accept input from the keyboard but continue to loop until ;the password is correctly re-entered. ; kylock3: mov di,80h ;point DI to upper storage call get_password ;get password cmp cx,char_count ;same number of characters? jne kylock3 ;no, then paswords don't match cmp al,27 ;was input ended with ESC key? je kylock3 ;yes, start input loop over xor si,si ;point SI to first password mov di,80h ;point DI to second password cld ;clear DF for string operations repe cmpsw ;compare the two passwords jne kylock3 ;not equal, continue looping ; ;Exit kylock routine by clearing the status flag, enabling the video display, ;and executing an IRET instruction. ; unlock: mov kylock_status,0 ;reset status byte push ax ;save ax & dx push dx call video_enable ;re-enable video display pop dx ;restore dx & ax pop ax unlck1: pop es ;restore register values pop ds pop di pop si pop dx pop cx pop bx pop ax iret ;exit kylock routine kylock endp ; ;------------------------------------------------------------------------------ ;VIDEO ENABLE and VIDEO DISABLE enable and disable the VIDEO output to the ;screen of the PCJR ;------------------------------------------------------------------------------ ; video_disable proc near ;disable the video display cmp adapter,0 ;is video adapter an EGA? je ega_disable ;yes, then jump test adapter,2 ;is computer a PCJR? jnz jr_disable ;yes, then jump ; ;Disable video of PC with CGA or MDA adapter. ; push ds ;save ds mov ax,bios_data ;set es to bios data area mov ds,ax assume ds:bios_data mov al,crt_mode_set ;get current value (dynamic) of ;6845 mode control register mov pc_mode,al ;save it mov ax,addr_6845 ;get active display address add ax,4 ;add 4 to get MSR address mov msr_address,ax ;save address mov al,0ah ;out 6845 index register... mov dx,03b4h ;points to 6845 data reg. 10 out dx,al mov al,2bh ;value to turn off cursor mov dx,03b5h ;6845 data registers port out dx,al ;disable cursor mov dx,msr_address ;6845 mode control register mov al,pc_mode ;get current value of 6845 mode and al,37h ;strip enable bit out dx,al ;disable video display pop ds ;restore ds ret ; ;Disable video of PC with an EGA card. ; ega_disable: xor al,al ;zero al (clear bit 5) call set_ega ;disable EGA ret ; ;Disable video of PCJR. ; jr_disable: push ds ;save ds register mov ax,bios_data ;set es to bios data area mov ds,ax ; assume ds:bios_data ; mov al,crt_mode_set ;get current value (dynamic) of ;PCJR VGA mode control register mov pcjr_mode,al ;store current value, VGA mode mov dx,03dah ;PCJR VGA I/O port in al,dx ;addr/data f/f to proper state mov al,02h ;VGA border color register out dx,al ;set VGA to border color cont. mov al,00h ;color black out dx,al ;set border color black mov al,00 ;VGA mode control 1 register out dx,al ;set VGA to mode control 1 mov al,pcjr_mode ;get current value of VGA mode and al,0f7h ;toggle enable/disable bit out dx,al ;disable video display pop ds ;restore ds register ret video_disable endp ; video_enable proc near ;enable the video display cmp adapter,0 ;is video adapter an EGA? je ega_enable ;yes,then jump test adapter,2 ;is the computer a PCJR? jnz jr_enable ;yes, then jump ; ;Enable video of PC with CGA or MDA adapter card. ; mov al,0ah ;out to 6845 index register... mov dx,03b4h ;points to 6845 data reg. 10 out dx,al mov al,0bh ;value to turn cursor on mov dx,03b5h ;6845 data registers port out dx,al ;enable cursor mov dx,msr_address ;6845 mode control register mov al,pc_mode ;get stored value 6845 mode out dx,al ;enable pc display ret ; ;Enable video of PC with an EGA adapter card. ; ega_enable: mov al,20h ;set bit 5 of al call set_ega ;enable EGA video ret ; ;Enable video of PCJR. ; jr_enable: mov dx,03dah ;set PCJR VGA address in al,dx ;addr/data f/f to proper state mov al,00h ;VGA mode control 1 register out dx,al ;set VGA to mode control 1 mov al,pcjr_mode ;get stored value VGA mode out dx,al ;enable PCJR video display ... ;border remains black ret video_enable endp ; ;----------------------------------------------------------------------------- ;SET_EGA is called by VIDEO_ENABLE and VIDEO_DISABLE routines to selectively ;set or clear bit 5 of the EGA Attribute Address Register. ;Entry: AL - value to OUT to Attribute Address Register ;----------------------------------------------------------------------------- ; set_ega proc near push ax ;save AL mov dx,3bah ;reset monochrome flip-flop... in al,dx ;for write to Address Register mov dx,3dah ;reset color flip-flop in al,dx mov dx,3c0h ;set DX to Attr Addr Register pop ax ;retrieve entry value of AL out dx,al ;write value to register ret set_ega endp ; ;------------------------------------------------------------------------------ ;KB RESET subroutine resets the keyboard and issues an EOI to the 8259 PIC. ;------------------------------------------------------------------------------ ; kb_reset proc near test adapter,2 ;Is this computer a PCJR? jnz jr_kbd ;yes,then jump ; ;Reset standard PC keyboard. ; std_kbd: in al,kb_ctrl ;get current control port value mov ah,al ;save it or al,80h ;set the keyboard clear bit out kb_ctrl,al ;send reset value to port mov al,ah ;get the original value out kb_ctrl,al ;enable the keyboard jmp kbd1 ;jump to disable interrupts ;and send EOI signal to 8259 ; ;Reset PCJR keyboard. ; jr_kbd: in al,0a0h ;yes, then read NMI mask ;register to clear PCJR ;keyboard NMI latch kbd1: cli ;disable interrupts mov al,eoi ;get eoi value out int_ctrl_port,al ;send eoi signal to the 8259 sti ;enable interrupts ret ;return to caller kb_reset endp ; ;------------------------------------------------------------------------------ ;GET PASSWORD subroutine reads up to 50 characters entered from the keyboard ;and stores them in the designated buffer. Backspace key is active as an ;editing key. ;Entry: ES:DI - buffer address | EXIT: CX - character count ;------------------------------------------------------------------------------ ; get_password proc near cld ;clear DF for string operations xor cx,cx ;zero CX - initial char count getpas1: mov ah,0 ;INT 16h funct. - get keypress int 16h ;get character from keyboard cmp al,13 ;ENTER key? je done ;yes, then exit cmp al,27 ;ESC key? je done ;yes, then exit cmp al,8 ;BACKSPACE key? je backspace ;yes,goto backspace routine cmp cx,40h ;is the buffer full? je buffer_full ;yes, then don't accept entry inc cx ;char entered - increment count stosw ;deposit character in buffer jmp getpas1 ;return for more input backspace: or cx,cx ;any characters to delete? je getpas1 ;no,then goto input loop sub di,2 ;decrement buffer pointer dec cx ;decrement character count jmp getpas1 ;return to input loop buffer_full: mov ah,14 ;INT 10h function - Write TTY mov al,7 ;ASCII code for beep int 10h ;sound the beep jmp getpas1 ;and return for more input done: ret ;return to calling routine get_password endp ; ;------------------------------------------------------------------------------ ;INITIALIZE routine checks to see if KYLOCK has already been loaded. If so, ;execution aborts with an error message. If it hasn't, then the value of ;ADAPTER is set according to the type of display adapter present in the system ;and the vectors in low memory pointing to the INT 9h and 16h routines are set ;to point to our own newly installed code. ;------------------------------------------------------------------------------ ; initialize proc near ; ;See if KYLOCK has been previously loaded by calling INT 16h with AH set to ;255 and BH set to 0. If BH comes back unchanged, then KYLOCK is NOT ;currently resident in memory; if BH = 255, then KYLOCK has been loaded. ; mov ah,255 ;set AH and BH xor bh,bh int 16h ;call interrupt routine or bh,bh ;is BH = 0? je init1 ;yes, then continue lea dx,errmsg ;no, print error message & exit mov ah,09h int 21h ret ; ;Check the computer's ID to see if its a PC or PCJR. ; init1: mov ax,0f000h ;es to BIOS segment holding mov es,ax ;computer ID value mov al,byte ptr es:[0fffeh] ;offset address and load to al sub al,0fch ; or al,al ;al = 0? jz pc ;AT, try the pc routine... dec al ;al = 1? jz pcjr ;yes, then computer is a PCJR dec al ;al = 2? jz pc ;XT, try the pc routine... dec al ;al = 3? jz pc ;PC jnz pc ;unidentified computer, try PC ret ; ;The computer is a PCJR. ; pcjr: mov adapter,2 ;set adapter to PCJR jmp init2 ;jump to install program ; ;The computer is a PC. Check for the presence of an Enhanced Graphics Adapter ;by looking for an 'IBM'signature in the EGA Bios area. ; pc: mov ax,0c000h ;set ES to EGA BIOS segment mov es,ax mov di,1eh ;starting address of signature lea si,ibm_signature ;point si to 'IBM' text mov cx,3 ;three characters to check cld ;clear df repe cmpsb ;compare the three bytes je init2 ;signature found - EGA present ; ;The computer is a PC, but the display adapter is not an EGA. It must be ;either a CGA or an MDA. ; mov adapter,1 ;set ADAPTER for CGA or MDA ; ;Save the current interrupt 16h vector and replace it with our own. ; init2: mov ah,35h ;DOS function - get vector mov al,16h ;interrupt 16h int 21h ;get the vector mov int_16h_ptr,bx ;save offset of vector mov int_16h_ptr[2],es ;save segment of vector mov ah,25h ;DOS function - set vector mov al,16h ;interrupt 16h lea dx,new_int_16h ;pointer to new routine int 21h ;set vector ; ;Now save the old interrupt 9 vector, replace it with the new one, and exit. ; mov ah,35h ;DOS function - get vector mov al,9h ;interrupt 9 int 21h ;get vector mov int_9h_ptr,bx ;save offset mov int_9h_ptr[2],es ;save segment mov ah,25h ;DOS function - set vector mov al,9h ;interrupt 9 lea dx,kylock ;point to our freeze routine int 21h ;set vector ; ;Save the current interrupt 5h vector and replace it with a new routine. ; mov ah,35h ;DOS function - get vector mov al,5h ;interrupt 5h int 21h ;get the vector mov int_5h_ptr,bx ;save offset of vector mov int_5h_ptr[2],es ;save segment of vector mov ah,25h ;DOS function - set vector mov al,5h ;interrupt 5h lea dx,new_int_5h ;pointer to new routine int 21h ;set vector mov dx,(offset initialize - seg_org + 15) shr 4 ;... ;prepare DX for exit mov ah,31h ;terminate-but-stay-resident int 21h ;dos function call initialize endp ; code ends end begin