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Assembly Source File | 1993-03-02 | 24.0 KB | 893 lines

page 66,132 ;==================================================================== ; ; BOOTPW - A program to password protect a disk ; ; Copyright (c) 1993 Douglas Boling ; ;==================================================================== code segment assume cs:code org 100h ;==================================================================== ;BOOTPW Boot record ; ; Entry: ; CS:IP - 0:7C00h ; DL - boot drive ; ES:SI - Ptr to partition table boot entry (if hard disk.) ; All other registers undefined ;==================================================================== root_offset equ 500h boot_buffer equ offset end_of_code + 512 pw_nonres equ offset password_size - offset entry data_startl equ word ptr [bp] data_starth equ word ptr [bp+2] boot_disk equ byte ptr [bp+4] bytes_per_sec equ word ptr [bp+0bh] sec_per_cluster equ byte ptr [bp+0dh] reserved_sec equ word ptr [bp+0eh] number_of_fats equ byte ptr [bp+10h] root_size equ word ptr [bp+11h] total_sec equ word ptr [bp+13h] media_des_byte equ byte ptr [bp+15h] sec_per_fat equ word ptr [bp+16h] sec_per_track equ word ptr [bp+18h] number_of_heads equ word ptr [bp+1ah] num_hidden_sec equ word ptr [bp+1ch] boot_flag equ word ptr [bp+3feh] oldboot_name equ 7c00h + offset oldboot_nameo - offset entry boot_initmsg equ 7c00h + offset program - offset entry boot_pwmsg equ 7c00h + offset pw_msg - offset entry boot_perrmsg equ 7c00h + offset pwerror_msg - offset entry boot_rerrmsg equ 7c00h + offset readerr_msg - offset entry boot_ferrmsg equ 7c00h + offset finderr_msg - offset entry boot_pw equ 7c00h + offset password - offset entry boot_pwsize equ 7c00h + offset password_size - offset entry ;-------------------------------------------------------------------- ;Boot sector code ;-------------------------------------------------------------------- entry: jmp initialize oem_field db "BootPW10" bpb_data db 24 dup (0) ;Leave room for rest of BPB bpb_dataend = $ boot_1: cli ;Disable interrupts cld ;Set direction UP. mov ax,7c00h xor bx,bx mov ss,bx ;SS:SP = 790:0 mov sp,ax sti ;Interrupts OK mov ds,bx mov es,bx push si ;Save Part table ptr push bp mov bp,ax mov boot_disk,dl mov al,number_of_fats ;Compute the sector of the cbw ; roor directory. mul sec_per_fat mov cx,reserved_sec add cx,num_hidden_sec adc dx,num_hidden_sec[2] add cx,ax adc dx,bx ;BX = 0 push cx ;Save root sector low push dx ;Save root sector high mov data_startl,cx mov data_starth,dx mov ax,32 ;Get length of dir entry mul root_size ;Compute the size -in sectors- mov si,bytes_per_sec ; of the Root Directory. add ax,si dec ax div si add data_startl,ax adc data_starth,bx push ax pop cx pop dx ;Get root directory pop ax ; starting sector mov bx,root_offset ;Read the root dir push bx ;Save ptr to Root dir boot_3: push cx push ax push dx call boot_read_disk ;Loop on read_disk to pop dx ; read in all sectors pop ax ; of the root dir pop cx jc boot_error add bx,bytes_per_sec add ax,1 adc dx,0 loop boot_3 mov si,boot_initmsg ;Identify ourselves call bootprint_msg mov si,boot_pwmsg ;Prompt for PW call bootprint_msg mov di,7c00h call read_line ;Get password mov si,boot_pwsize lodsb cmp cl,al jne boot_badpw rep cmpsb jne boot_badpw pop si ;Get back Root ptr mov bx,root_size boot_4: mov di,oldboot_name ;Find old boot record mov cx,8 ; in root directory push si repe cmpsb pop si je boot_5 add si,32 dec bx jne boot_4 mov si,boot_ferrmsg jmp short boot_error boot_5: mov cx,word ptr [si+1ah] ;Get start clust dec cx ;Compensate for 1st to FAT dec cx ; entries not being used. mov al,sec_per_cluster ;Get sectors per cluster cbw mul cx add ax,data_startl adc dx,data_starth mov bx,7e00h ;To address 0:7E00 call boot_read_disk jc boot_error xor ax,ax cwd call boot_write_disk pop bp pop si int 19h ;Reboot boot_badpw: mov si,boot_perrmsg boot_error: call bootprint_msg boot_halt: jmp boot_halt ;----------------------------------------------------------------------- ; Write/Read disk - Writes or reads one sector from the disk ; Entry: DX,AX - Absolute sector to write/read ; BX - address of buffer. ; Exit: CF - Clear if read successful. ;----------------------------------------------------------------------- boot_write_disk proc near mov cx,0301h jmp short read_1 boot_read_disk proc near mov cx,0201h read_1: push cx push bx div sec_per_track ;Get sectors per track inc dx read_2: mov bx,dx ;Save sector cwd div number_of_heads ;Compute head and cylinder xchg ah,al ;Swap cyl low and high bytes mov cl,6 shl al,cl ;Shift high cyl bits xchg cx,ax ;Copy cyl into CX or cl,bl ;Combine cyl with sector mov dh,dl ;Move head number mov si,5 ;Try to read 5 times. pop bx ;Get dest buff offset pop ax ;Get Read/Write cmd read_3: mov dl,boot_disk ;Get disk to read push ax int 13h ;Read/Write disk. pop ax jnc read_exit ;No error, exit xor ax,ax ;Reset disk before reading int 13h dec si jnz read_3 mov si,boot_rerrmsg stc read_exit: ret boot_read_disk endp boot_write_disk endp ;-------------------------------------------------------------------- ; Print Msg - Prints a message to the screen ; Entry: DS:SI - Points to ASCIIZ message ;-------------------------------------------------------------------- bootprint_msg proc near push bx push bp bprint_msg1: lodsb or al,al je bprint_exit mov ah,0eh mov bx,7h push si int 10h pop si jmp short bprint_msg1 bprint_exit: mov ax,0e0dh ;Append CR - LF int 10h mov ax,0e0ah int 10h pop bp pop bx ret bootprint_msg endp password_size db 0 password db 4eh,75h,0f0h,0beh,7dh,0b4h,0f9h,0c3h ;-------------------------------------------------------------------- ; Read Line - Reads upto 8 charagers from the keyboard - No echo ; Entry: DS:DI - Points to buffer ; Exit: CX - Number of characters in buffer ;-------------------------------------------------------------------- read_line proc near push di mov cx,8 readl_1: xor ax,ax ;Get key int 16h cmp al,13 je readl_exit cmp al,8 je readl_2 not al stosb loop readl_1 readl_exit: sub cx,8 neg cx pop di ret readl_2: cmp cx,8 je readl_1 dec di inc cx jmp short readl_1 read_line endp program db 13,10,"BOOTPW 1.0 " db "Copyright 1993 Douglas Boling",0 pw_msg db 13,10,10,"Enter Password",0 pwerror_msg db "Wrong password",0 readerr_msg db "Read Error",0 finderr_msg db "Can",39,"t find " oldboot_nameo db "OLDBOOT BIN",0 bootcode_end = $ org 2feh dw 0AA55h ;Boot signature boot_end = $ ;==================================================================== ;Start of nonresident install code ;==================================================================== program1 db "First published in PC Magazine, " db "March 30, 1993",13,10,10,0 infomsg1 db "USAGE: BOOTPW d:",13,10 db "d: is the target diskette to " db "password protect",0 infomsg3 db "Please enter password, up to 8 characters",0 infomsg4 db "Please reenter password for verification",0 infomsg5 db 13,10,"Disk " infomsg5_dsk db " : Password protected.",0 infomsg6 db 13,10,"Password removed",0 infomsg7 db "Disk password protected",0 infomsg8 db 13,10,"Please remove the disk from the drive " db "and press <Enter>",13,10 db "or if the disk is a hard drive, turn off the system.",0 errmsg0 db "This program requires DOS 2.0 or greater",0 errmsg1 db "Target drive letter not specified",0 errmsg2 db "Target diskette not a DOS formatted " db "disk",0 errmsg3 db "Unable to fit BOOTPW code on " db "target disk",0 errmsg4 db "Passwords do not match",0 errmsg5 db "No password entered, disk not modified",0 errmsg6 db "The password doesn't match the disk " db "password",0 errmsg7 db "Unable to find old DOS boot record",0 dos_version dw 0 crit_vec dd 0 ;Critical err vector targ_disk db 0 ;Disk to modify oldboot_fname db "C:\OLDBOOT.BIN",0 doserr_tbl dw offset doserr_00 dw offset doserr_01 dw offset doserr_02 dw offset doserr_03 dw offset doserr_04 dw offset doserr_05 dw offset doserr_06 dw offset doserr_07 dw offset doserr_08 dw offset doserr_09 dw offset doserr_10 dw offset doserr_11 dw offset doserr_12 dw offset doserr_unk doserr_tblend = $ doserr_00 db "Disk Write Protected",0 doserr_01 db "Unknown Unit",0 doserr_02 db "Drive not ready",0 doserr_03 db "Unknown Command",0 doserr_04 db "CRC Data Error",0 doserr_05 db "Bad request structure",0 doserr_06 db "Disk Seek error",0 doserr_07 db "Not a DOS disk",0 doserr_08 db "Sector not found",0 doserr_09 db "Printer out of paper",0 doserr_10 db "Disk Write fault",0 doserr_11 db "Disk Read fault",0 doserr_12 db "General failure",0 doserr_unk db "Unknown DOS error",0 ;-------------------------------------------------------------------- ; INITIALIZE - Entry point of nonresident code ;-------------------------------------------------------------------- initialize: cld ;String ops UP mov ah,30h ;Get DOS version int 21h xchg al,ah mov si,offset errmsg0 cmp ax,200h jb init_jmperror mov dos_version,ax mov si,offset program ;Print copyright msg call print_msg mov si,offset program1 call print_msg call set_crit_vec ;Set crit vec to int routine mov si,offset infomsg1 ;Syntax msg text cmp byte ptr ds:[80h],0 je init_jmperror mov si,offset 81h call get_drive ;Get target disk jc init_jmperror mov targ_disk,al ;Save drive number mov oldboot_fname,ah ;Save drive letter mov bx,boot_buffer call read_boot ;Read current boot record jc init_jmperror call check4bpw ;See if BOOTPW protected jnz init_3 mov si,offset infomsg7 ;Tell user disk protected call print_msg mov si,offset infomsg3 ;Password prompt call print_msg mov di,offset end_of_code call read_line mov si,boot_buffer add si,pw_nonres lodsb cmp al,cl jne init_1 ;PW lengths don't match rep cmpsb jne init_1 ;PWs don't match call uninstall jc init_error jmp short init_exit init_1: mov si,offset errmsg6 ;Bad password init_jmperror: jmp short init_error init_3: mov si,offset infomsg3 ;Password prompt call print_msg mov di,offset end_of_code call read_line mov si,offset errmsg5 ;Password not entered jcxz init_error push cx mov si,offset infomsg4 ;Password verify prompt call print_msg mov di,offset end_of_code+16 call read_line mov si,offset errmsg4 ;Passwords don't match pop bx cmp cx,bx jne init_error mov si,offset end_of_code mov di,offset end_of_code+16 push cx rep cmpsb pop cx mov si,offset errmsg4 ;Passwords don't match jne init_error mov si,offset end_of_code mov di,offset password mov password_size,cl rep movsb ;Copy password call install init_4: mov si,offset infomsg8 ;Make user remove the disk call print_msg mov ah,7 ;DOS read key int 21h or al,al jne init_5 mov ah,7 int 21h init_5: cmp al,27 je init_6 mov ah,1ch ;Get allocation info mov dl,targ_disk inc dl int 21h jnc init_4 init_6: xor ax,ax ;Clear return code init_exit: push ax call reset_crit_vec ;Restore critical error vec pop ax mov ah,4ch int 21h init_error: call print_msg mov al,1 jmp short init_exit ;-------------------------------------------------------------------- ;GET DRIVE - Returns a disk number for a letter on the command line ; Entry: SI - Ptr to command line ; Exit: AL - Drive number ; AH - Drvie letter ; SI - Points to character after : ; CF - Set if error ; DX - Offset of error message if CF set ;-------------------------------------------------------------------- get_drive proc near lodsb cmp al,13 ;See if end of line je getdisk_err cmp al,20h ;If space, keep looking jbe get_drive mov ah,al ;Save letter in AH and ah,0dfh ;Convert to upper case or al,20h ;Convert to lower case sub al,'a' ;See if between a - z jb getdisk_err cmp al,25 ja getdisk_err mov bl,al lodsb ;See if trailing : cmp al,":" ; present. jne getdisk_err mov al,bl ;Get back drv letter cmp al,2 jb getdisk_1 mov al,80h getdisk_1: clc getdisk_exit: ret getdisk_err: mov si,offset errmsg1 stc jmp short getdisk_exit get_drive endp ;-------------------------------------------------------------------- ;INSTALL - Installs the BOOTPW boot record on the target diskette ; Exit: CF - Set if error ; DX - Offset of error message if CF set ;-------------------------------------------------------------------- install proc near mov di,offset entry mov ax,0eb90h ;NOP + JMP short opcode stosw mov ax,offset boot_1 - offset bpb_data stosb mov si,boot_buffer ;Get ptr to boot rec lodsb mov bl,al ;Get opcode lodsw cmp bl,0ebh ;See if short JMP opcode jne install_1 xor ah,ah ;If short JMP, clear jmp install_2 ; high byte install_1: mov si,offset errmsg2 cmp bl,0e9h ;Check for long JMP jne install_error install_2: mov si,boot_buffer+11 mov di,offset bpb_data ;Copy BIOS Param Blk mov cx,offset bpb_dataend - offset bpb_data - 8 rep movsb mov ah,3ch ;Create file mov cx,2 ;Make hidden mov dx,offset oldboot_fname push ds int 21h pop ds mov si,offset errmsg3 jc install_exit mov bx,ax ;Copy file handle mov ah,40h mov cx,512 ;Write 512 bytes mov dx,boot_buffer int 21h mov si,offset errmsg3 jc install_exit mov ah,3eh ;Close file int 21h mov si,offset errmsg3 jc install_exit mov al,targ_disk ;Get target disk mov bx,offset entry ;Point to BootPW rec call write_boot ;Write new boot rec jc install_exit mov al,oldboot_fname mov infomsg5_dsk,al mov si,offset infomsg5 ;Indicate installed call print_msg clc install_exit: ret install_error: stc jmp short install_exit install endp ;-------------------------------------------------------------------- ;UNINSTALL - Uninstalls BOOTPW from the target disk ; Exit: CF - Set if error ; DX - Offset of error message if CF set ;-------------------------------------------------------------------- uninstall proc near mov di,boot_buffer mov al,0ebh ;JMP short opcode stosb mov al,offset boot_1 - offset bpb_data + 1 stosb mov al,90h stosb mov al,targ_disk ;Get target disk mov bx,boot_buffer ;Point to BootPW rec call write_boot ;Write new boot rec jc uninstall_error mov ah,0dh ;Reset disks int 21h mov ax,3d00h ;Open file mov dx,offset oldboot_fname ;Open file that has int 21h ; old boot rec mov si,offset errmsg7 jc uninstall_exit mov bx,ax ;Copy file handle mov ah,3fh mov cx,512 ;Read 512 bytes mov dx,boot_buffer int 21h mov si,offset errmsg7 jc uninstall_exit mov ah,3eh ;Close file int 21h mov si,offset errmsg7 jc uninstall_exit mov al,targ_disk ;Get target disk mov bx,boot_buffer ;Point to DOS rec call write_boot ;Write DOS boot rec jc uninstall_exit mov si,offset infomsg6 ;Tell user, disk call print_msg ; unprotected. uninstall_exit: ret uninstall_error: stc jmp short uninstall_exit uninstall endp ;-------------------------------------------------------------------- ; CHECK4BPW - Check boot record to see if it is a BootPW boot rec ; Exit: ZF - Set if BootPW record ;-------------------------------------------------------------------- check4bpw proc near mov si,boot_buffer add si,3 mov di,offset oem_field mov cx,8 rep cmpsb ret check4bpw endp ;-------------------------------------------------------------------- ; READ BOOT - Reads the boot sector of a disk ; Entry: AL - Disk number (0=A, 1=B,...) ; BX - Points to buffer ; Exit: CF - Set if error ; DX - Points to error message ;-------------------------------------------------------------------- read_boot proc near mov al,targ_disk ;Get target disk mov cx,1 ;read 1 sector mov dx,0 ;Sector 0 call read_absolute ;Read current boot rec ret read_boot endp ;-------------------------------------------------------------------- ; WRITE BOOT - Wrotes the boot sector of a disk ; Entry: AL - Disk number (0=A, 1=B,...) ; BX - Points to buffer ; Exit: CF - Set if error ; DX - Points to error message ;-------------------------------------------------------------------- write_boot proc near mov al,targ_disk ;Get target disk mov cx,1 ;read 1 sector mov dx,0 ;Sector 0 call write_absolute ;Read current boot rec ret write_boot endp ;-------------------------------------------------------------------- ; READ ABSOLUTE - Reads sectors from the disk. ; Entry: AL - Letter of drive to read ; CX - Number of sectors to read. ; SI,DX - Sector to start read (SI only used on huge disks) ; DS:BX - Pointer to data buffer. ;-------------------------------------------------------------------- read_abs_hstruc = $ ;Needed for >32M disks read_abs_start dd 0 ;Starting sector read_abs_cnt dw 0 ;Number of sectors to read read_abs_dbp dd 0 ;Data buffer ptr read_absolute proc near push bx push cx push ds call huge_disk_check jc read_abs_2 je read_abs_1 push ds ;Save ptr to data buffer push bx push cs pop ds mov bx,offset read_abs_hstruc mov [bx],dx ;More than 64K sectors mov [bx+2],si ; -> huge disk uses a mov [bx+4],cx ; different format pop [bx+6] ; than std int 25h. pop [bx+8] mov cx,-1 read_abs_1: int 25h ;DOS Absolute Disk Read pop bx ;Clean off old flags call seterrmsg cld read_abs_2: pop ds pop cx pop bx ret read_absolute endp ;-------------------------------------------------------------------- ; WRITE ABSOLUTE - Writes sectors to the disk. ; Entry: AL - Letter of drive to write ; CX - Number of sectors to write ; SI,DX - Sector to start write (SI only used on huge disks) ; DS:BX - Pointer to data buffer. ;-------------------------------------------------------------------- write_absolute proc near push bx push cx push ds call huge_disk_check jc write_abs_2 je write_abs_1 push ds ;Save data buffer pointer push bx push cs pop ds mov bx,offset read_abs_hstruc mov [bx],dx ;More than 64K sectors mov [bx+2],si ; -> huge disk uses a mov [bx+4],cx ; different format pop [bx+6] ; than std int 26h. pop [bx+8] mov cx,-1 write_abs_1: int 26h ;DOS Absolute Disk Write pop bx ;Clean off old flags call seterrmsg cld write_abs_2: pop ds pop cx pop bx ret write_absolute endp ;-------------------------------------------------------------------- ; HUGE DISK CHECK - Checks if disk is greater than 32 Meg ; Entry: AL - Disk to check ; Exit: ZF - Clear if > 32 Meg disk ; CF - Set if error ; DI - Sectors per cluster ;-------------------------------------------------------------------- last_disk_read db -1 last_disk_huge db 0 last_disk_spc dw 0 huge_disk_check proc near push ax push bx push cx push dx cmp al,last_disk_read ;Save last disk checked, if jne huge_disk_check_1 ; same as last disk, just mov di,last_disk_spc ; get saved answer. cmp last_disk_huge,0 jmp short huge_disk_check_3 huge_disk_check_1: mov last_disk_read,al mov last_disk_huge,0 mov dl,al ;Copy disk number inc dl mov ah,36h ;DOS Get Free disk space int 21h cmp ax,-1 jne huge_disk_check_2 mov last_disk_read,-1 jmp short huge_disk_check_4 huge_disk_check_2: mov di,ax ;Save sectors per cluster mov last_disk_spc,di mul dx or dx,dx ;See if more than 64K sectors je huge_disk_check_3 mov last_disk_huge,1 huge_disk_check_3: clc huge_disk_check_4: pop dx pop cx pop bx pop ax ret huge_disk_check endp ;-------------------------------------------------------------------- ; SET CRIT VEC - Sets the critical error vector to an internal routine ; to avoid the abort, retry, ignore message. ;-------------------------------------------------------------------- set_crit_vec proc near push es mov ax,3524h ;Get crititcal error vector int 21h mov word ptr crit_vec,bx ;Save vector mov word ptr crit_vec[2],es mov dx,offset crit_error ;Set to internal routine. mov ax,2524h int 21h pop es ret set_crit_vec endp ;-------------------------------------------------------------------- ; RESET CRIT VEC - Resets the critical error vector to its original ; state. ;-------------------------------------------------------------------- reset_crit_vec proc near push ds lds dx,crit_vec ;Get old vector mov ax,2524h ;Set vector int 21h pop ds ret reset_crit_vec endp ;-------------------------------------------------------------------- ; SETERRMSG - Assigns a DOS error message to the value in AL ; Entry: AL - Error code ; CF - Set if error ; Exit: SI - Points to error message ;-------------------------------------------------------------------- seterrmsg proc near push bx pushf jnc seterrmsg_exit mov bx,ax xor bh,bh shl bx,1 cmp bx,offset doserr_tblend - offset doserr_tbl jbe seterrmsg_1 mov bx,26 seterrmsg_1: mov si,[bx+doserr_tbl] seterrmsg_exit: popf pop bx ret seterrmsg endp ;-------------------------------------------------------------------- ; Print Msg - Prints a message to the screen ; Entry: DS:SI - Points to ASCIIZ message ;-------------------------------------------------------------------- crlf_msg db 13,10,"$" print_msg proc near print_msg1: lodsb or al,al je print_exit mov dl,al mov ah,02 int 21h jmp short print_msg1 print_exit: mov dx,offset crlf_msg mov ah,9 int 21h ret print_msg endp ;----------------------------------------------------------------------------- ; Prevent Abort,Retry,Ignore error msg with this dummy crit. error routine ;----------------------------------------------------------------------------- crit_error proc far mov al,0 ;Ignore critical error. cmp cs:dos_version,300h jb crit_1 mov al,3 crit_1: iret crit_error endp even end_of_code = $ code ends end entry