CP/M/CPM_CDROM.iso/cpm/utils/filutl/passwd30.asm

Assembly Source File | 1994-07-13 | 9.5 KB | 360 lines

;    title    'PASSWORD.ASM'
;    page    60
;
;
;        PASSWORD.ASM
;        Version 3.0
;     By Bo McCormick       8/6/81
;
; This is a program that adds password protection
; to programs. Format:
;
; PASSWORD name_of_file
;
; Then answer the prompt with the password to be
; applied to the program:
;
; Password?  enter password here
;
; If everything goes well, the program will be saved to disk.
; If not, a message is printed and control is passed
; to the CCP.
;
; The good part of this is, when you type in the program
; program name next time, instead of running the program
; right away, the program asks you for the password. If you
; reply with something other than the original password, the
; program doesn't run, and it returns to the ccp.
;
; 2/10/82: Set DMA before open because 1.4 CP/M uses buffer at 80H
; Removed "$" from labels so other assemblers can be used. Fixed
; "offset" to use tpa instead of 100H so it would work with
; modified CP/M.  Added encryption of password so dumping .COM
; file will not reveal it.  (Thanks to author of XYZZY.COM)
; Fixed test of supplied password to check all characters.
; Ted Shapin
;
; 12/10/81: changed ot$pw routine to input password one character
; at a time invisibly from BIOS rather than using BDOS's string input
; function.  This allows password to be typed in without anyone
; seeing what it was that was typed.  Jim Mills
;
;EQUATES
rdchar: equ    1
mesout: equ    9        ;BDOS functions
incon:    equ    10
open:    equ    15
close:    equ    16
delete: equ    19
read:    equ    20
write:    equ    21
setdma: equ    26
;
cr    equ    0dh        ;ascii values
lf    equ    0ah
eos    equ    '$'
;
boot    equ    0;4200H     ;0 for standard CP/M
                ;4200H for ALT. CP/M;
bdos    equ    boot+5
fcb    equ    boot+5ch
defbuf    equ    boot+80h
tpa    equ    boot+100h
stack    equ    tpa        ;out of way of tpa
;
    org    tpa

;
;
start:    lxi    h,0        ;save stack pointer
    dad    sp        ;put stack in hl
    shld    oldstack-offset ;save it
    lxi    sp,stack    ;get new stack
;
; stack saved so program can return to CCP without
; intervening warm start.
;
    lda    fcb+9        ;get first char of extension
    cpi    ' '        ;if ' ' then change to .COM
    jz    notype
    cpi    'C'        ;If there is an extension,
    jnz    notright    ;make sure it's .COM
    lda    fcb+10        ;check second letter
    cpi    'O'
    jnz    notright
    lda    fcb+11
    cpi    'M'        ;last letter
    jz    iscom        ;if it is a COM, then cont.
notright:
    call    endmes        ;it's not a com file, so tell
;
    db    cr,lf,'Must be a command (.COM) file'
    db    cr,lf,eos
;
endmes:
    pop    d        ;get address of message
    mvi    c,mesout    ;PRINT STRING command
    call    bdos        ;print error message
;
finish: lhld    oldstack-offset ;get old stack
    sphl            ;put it in HL
    ret            ;return to CP/M
;
notype: mvi    a,'C'        ;if there was space, change
    sta    fcb+9        ;to COM
    mvi    a,'O'
    sta    fcb+10
    mvi    a,'M'
    sta    fcb+11
;
iscom:    lxi    d,buffer-offset ;point to where program goes
    mvi    c,setdma    ;SET DMA command
    push    d        ;save it
    call    bdos        ;and tell CP/M
    mvi    a,0        ;zero record count
    sta    fcb+32
    mvi    c,open        ;OPEN file command
    lxi    d,fcb        ;load address of FCB in DE
    call    bdos        ;Open file
    inr    a        ;successful?
    jnz    openok        ;if so, then continue
    call    endmes        ;if not, then tell
;
    db    cr,lf,'Cannot open file',cr,lf,eos
;
openok: pop    d        ;get starting dma back
rloop:    mvi    c,setdma    ;and set it in loop
    push    d        ;save it
    call    bdos
    lxi    d,fcb        ;point to FCB
    mvi    c,read        ;READ sector command
    call    bdos        ;do it
    pop    d        ;get DMA address back
    ana    a        ;EOF?
    jnz    doneread    ;if so, then ask for password
    lxi    h,80h        ;length of sector
    dad    d        ;bump DMA
    xchg            ;put new address in DE
    jmp    rloop        ;and read some more
;
doneread:
    xchg            ;dma ==> hl
    shld    endprog-offset    ;save last address
gpasag    call    getpas        ;print password message
;
pasmes    db    'Password? ',eos
;
getpas    pop    d        ;get address of message
    mvi    c,mesout    ;PRINT STRING function
    call    bdos        ;print it
    lxi    d,defbuf    ;point to default buffer
    mvi    a,8        ;tell CP/M max chars
    stax    d        ;put it there
    mvi    c,incon     ;READ LINE command
    call    bdos        ;do it
    lxi    h,defbuf+1    ;point to length
    lxi    d,password-offset    ;point to storage
    mov    a,m        ;get length
    ana    a        ;set flags
    jz    gpasag        ;if 0 then ask again
    inr    a        ;plus 1 for length byte
    mov    b,a        ;put length in B
    xra    b        ;cancel first xra in loop
    mov    m,a        ;and put it back
mploop    mov    a,m        ;get char
    xra    b        ;encrypt it
    stax    d        ;save it
    inx    h        ;increment pointer
    inx    d        ;  "          "
    dcr    b        ;decrement length
    jnz    mploop        ;if not zero, then next char
    xra    a        ;zero a
    sta    fcb+12        ;zero bytes in FCB
    sta    fcb+14
    sta    fcb+32
    mvi    c,open        ;OPEN file command
    lxi    d,fcb        ;point to FCB
    call    bdos        ;open the file
    lxi    d,nstart    ;point to new program start
;
    push    d
wloop1    pop    d        ;get DMA
    push    d        ;put it back on stack
    mvi    c,setdma    ;SET DMA command
    call    bdos        ;tell CP/M
    lxi    d,fcb        ;point to FCB
    mvi    c,write     ;WRITE SECTOR command
    call    bdos        ;do it
    pop    h        ;get DMA address from stack
    lxi    d,80h        ;length of sector
    dad    d        ;HL has new DMA
    push    h        ;put it on stack
    mov    a,h        ;this is to get 2's complement
    cma            ;of address. We are subtracting
    mov    d,a        ;the current address from the
    mov    a,l        ;high address. If the high byte
    cma            ;<1 , we are done
    mov    e,a        ;
    inx    d        ;Now 2's comp. of address in DE
    lhld    endprog-offset    ;get ending address
    dad    d        ;Subtract (add 2's comp)
    mov    a,h        ;get high byte
    inr    a        ;is it FF (-1)?
    ana    a        ;set flags
    jnz    wloop1        ;if not, write another sector
;
    mvi    c,close     ;That's it. Close the file
    lxi    d,fcb        ;point to FCB
    call    bdos        ;do it
    jmp    finish        ;goto finish
;
;
nstart:
offset    equ    tpa-nstart
;
;    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
;    %% WARNING -                        %%
;    %% From now on, all labels are in            %%
;    %% the form:                        %%
;    %%    LABEL    EQU  $+OFFSET                %%
;    %%  This is to allow the program to run at100H        %%
;    %% when it is saved by the earlier portion.        %%
;    %%  ALL new labels added MUST be in the form        %%
;    %% LABEL   EQU    $+OFFSET for this program to work   %%
;    %% properly.                        %%
;    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
;
;This is portion of the program is placed at the beginning
;of the program to be PASSWORDed. When it is executed, it will
;ask for a password. If the password is incorrect, the program
;warm starts. If the password is correct, the program is moved
;to the TPA and executed.
;
    lxi    h,0        ;save stack pointer
    dad    sp        ;stack is in HL
    shld    oldstack    ;save it
    lxi    sp,stack    ;get new stack
    call    otpw        ;print password message
;
    db    cr,lf,'Password? '
    db    eos
;
otpw    equ    $+offset
    pop    d        ;get address of message
    mvi    c,mesout    ;PRINT STRING command
    call    bdos        ;print it

    lxi    d,newbuf+1    ;point to storage area
    xra    a
    mov    b,a        ;init counter
    stax    d        ;# of chars typed (for compare)
    inx    d        ;and point to string
;
; we don't want to allow 'lookers' to see the password, so call
; bios instead of bdos to prevent echo.  also allows control chars.
;
    lhld    boot+1        ;get addr of warm start routine
    push    d
    lxi    d,6        ;+ offset to kbd input routine
    dad    d
    pop    d
    shld    bconin+1    ;now init'd to bios conin

otpw1    equ    $+offset
    push    b        ;save counter..
    push    d        ;..& pointer
bconin    equ    $+offset
    call    $-$        ;to be filled in by above routine
    pop    d        ;restore pointer..
    pop    b        ;..& counter
    stax    d        ;store char
    inx    d        ;bump pointer..
    inr    b        ;..& counter
    cpi    cr
    jnz    otpw1        ;loop until cr typed
; B has the length of password furnished + 1 for count.
    lxi    h,password    ;point to actual password
    lxi    d,newbuf+1    ;point to user's input
    xra    a        ;this 0 xra with length in B
    stax    d        ;should equal count in passwd
;
; first char compared is a count of # of chars in password,
; followed by password itself.
;
clp    equ    $+offset
    ldax    d        ;get char
    xra    b        ;encrypt it
    cmp    m        ;are they the same?
    jnz    boot        ;if not, restart
    inx    h        ;point to next characters
    inx    d        ;  "    "  "        "
    dcr    b        ;decrement length
    jnz    clp        ;if not done, then loop
;
; Now we move a segment of code to a part of the default
; buffer. This segment moves the actual program down to the
; TPA
;
    lxi    h,nmv        ;point to code
    lxi    d,defbuf+20h    ;point to new postion
    mvi    b,nmlen ;length
;
move    equ    $+offset
    mov    a,m        ;get byte
    stax    d        ;save it
    inx    d        ;point to next addresses
    inx    h        ;  "   "    "       "
    dcr    b        ;decrement length
    jnz    move        ;if not done, loop
    jmp    defbuf+20h    ;go to segment
;
nmv    equ    $+offset    ;segment that gets moved
    lhld    oldstack    ;get stack pointer
    push    h        ;save it on stack
    lxi    h,buffer    ;get start of actual program
    mov    a,h        ;We have to compute the length
    cma            ;and because X-Y equals
    mov    d,a        ;X + Two's complent(Y), we have
    mov    a,l        ;to find the 2's comp. of the
    cma            ;first address
    mov    e,a        ;
    inx    d        ;Y is in DE
    lhld    endprog ;get last address
    dad    d        ;subtract (add 2's comp)
    mov    b,h        ;put length in BC
    mov    c,l        ; "    "     "    "
    lxi    d,tpa        ;point to TPA
    lxi    h,buffer    ;point to first address
nmlp    equ    defbuf+20h+$+offset-nmv
    mov    a,m        ;get byte
    stax    d        ;save byte
    inx    h        ;increment address
    inx    d        ;    "          "
    dcx    b        ;decrement length
    mov    a,b        ;check for zero left
    ora    c        ;Are we done?
    jnz    nmlp        ;if not, loop some more
    pop    h        ;get stack from stack
    sphl            ;put stack in SP
    jmp    tpa        ;run program
;
nmlen    equ    $+offset-nmv    ;length of segment
;
;
password    equ    $+offset ;password storage
    db    0,'        '
;
;12/10/81 changed to allow use of tbuf as input area
;
newbuf    equ    $+offset    ;Users input buffer
    db    10H,0,'            '
;
oldstack    equ    $+offset ;place for stack
    ds    2
;
endprog equ    $+offset ;place for address
    ds    2
;
buffer    equ    $+offset    ;where actual program goes
    end