;ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
;                   Black Wolf's File Protection Utilities 2.1s
;
;PW_COM - Password Code for COM file password protection in PassCOM.
;         If modified, convert to data bytes and re-instate program into
;         PassCOM.ASM, then recompile PassCOM.
;      
;         Basically, this code is attached to a .COM file and, when executed,
;         waits for a password - if it is legit it continues, otherwise it
;         stops execution of the file.
;
;LISCENSE:
;    Released As Freeware - These files may be distributed freely.
;
;Any modifications made to this program should be listed below the solid line,
;along with the name of the programmer and the date the file was changed.
;Also - they should be commented where changed.
;
;NOTE THAT MODIFICATION PRIVILEDGES APPLY ONLY TO THIS VERSION (2.1s)!  
;I'd appreciate notification of any modifications if at all possible, 
;reach me through the address listed in the documentation file (bwfpu21s.doc).
;
;DISCLAIMER:  The author takes ABSOLUTELY NO RESPONSIBILITY for any damages
;resulting from the use/misuse of this program/file.  The user agrees to hold
;the author harmless for any consequences that may occur directly or 
;indirectly from the use of this program by utilizing this program/file
;in any manner.
;ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
;Modifications:
;       None as of 08/05/93 - Initial Release.

.model tiny
.radix 16
.code
        org 100
start:
        call    Get_Offset

Displaced:
        mov     byte ptr cs:[tr1+bp],0ea        ;Kill some debuggers
tr1:
        jmp     short tr2
        db      0
skip_it:
        jmp     skip2
        dw      0deadh
tr2:    
        mov     bx,offset tri3
        add     bx,bp
        push    bx
        mov     byte ptr cs:[tr2+bp],0c3   ;This one isn't a prefetch trick,
        jmp     skip_it                    ;but they might think it is....
skip2:
        jmp     tr2
tri3:
        cli
        push    ax ds
        xor     ax,ax
        mov     ds,ax
        lea     ax,[Print_Prompt+bp]
        xchg    ax,word ptr ds:[00]
        push    ax
        mov     ax,cs
        xchg    ax,word ptr ds:[02]
        push    ax
        push    ds
        push    cs
        pop     ds
        mov     word ptr cs:[Change_Div+bp],9090    ;This is an interesting
        xor     cx,cx                               ;trick - it basically
Change_Div:                                         ;calls Print_Prompt...
        div     cx                                  ;try debugging it....
        pop     ds
        pop     ax
        xchg    ax,word ptr ds:[02]
        pop     ax
        xchg    ax,word ptr ds:[00]
        pop     ds ax
        sti

        call    GetPass
        add     byte ptr cs:[tri4+1+bp],10   ;mod jump to mess up debuggers
tri4:
        jmp     Do_Encr_Pass    
        db      0ea
        db      9a
Do_Encr_Pass:
        call    Encrypt_Password
        call    Check_Passwords
        jc      BadPass
        
        xor     ax,ax
        mov     cx,0c
        lea     si,[Entered_Pass+bp]

GetValue:                               ;Get value to use to decrypt with..
        lodsb
        add     ah,al
        ror     ah,1
        loop    GetValue
                                                ;I need an improved algorithm
        lea     si,[Goodpass+bp]                ;here.......
        mov     cx,EndGoodPass-GoodPass         
        
Decrypt_Restore:        
        mov     al,[si]
        xor     al,ah
        mov     [si],al
        inc     si
        loop    Decrypt_Restore
        call    RenewPrefetch
        jmp     short GoodPass
        db      0ff
GoodPass:        
        mov     di,100
        push    di
        lea     si,bp+Storage_Bytes      ;Restore control to COM.
        movsw
        movsw
        xor     ax,ax
        mov     si,ax
        mov     di,ax
        ret
EndGoodPass:
        db      0ff

BadPass:        
        mov     ah,09
        lea     dx,[BadBad+bp]
        int     21
        mov     ax,4c01
        int     21
BadBad  db      0a,0dh,'Password Incorrect.',07,24

RenewPrefetch:
        nop
        jmp     loc1
        db      0ea
loc2:        
        clc
        ret
        db      9a
loc1:
        cld
        jmp     loc2
;------------------------------------------------------------------------
Check_Passwords:
        lea     si,[bp+Entered_Pass]
        lea     di,[Password+bp]
        mov     cx,0c
        repz    cmpsb
        jcxz    Password_Good   ;This spot needs to be more deeply imbedded
        stc                     ;to avoid simple hacking....
        ret
        db      0e9
Password_Good:
        clc
        ret
;------------------------------------------------------------------------
        db      0
Encrypt_Password:                       ;Here's another place I could use
        mov     bx,word ptr [Key1+bp]   ;a decent encryption algorithm....
        mov     dx,word ptr [Key2+bp]
        lea     si,[Entered_Pass+bp]
        mov     di,si
        mov     cx,6
  EncryptIt:      
        lodsw
        xor     ax,bx
        add     bx,dx
        stosw
        loop    EncryptIt
        ret
;------------------------------------------------------------------------
        db      0ea
GetPass:
        mov     cx,0c
        lea     di,[Entered_Pass+bp]
  KeyHit_Loop:
        push    cx
        sub     ax,ax
        int     16
        cmp     al,0dh
        je      HitReturn
        stosb
        pop     cx
        loop    KeyHit_Loop
        ret
  
  HitReturn:
        pop     cx
        xor     al,al
        repnz   stosb
        ret        
;------------------------------------------------------------------------
Print_Prompt:
        mov     ah,09
        lea     dx,[Info+bp]
        int     21
        iret
Info    db      'Password->',24
;------------------------------------------------------------------------
Get_Offset:
        pop     bp
        jmp     short confuzzled
        db      0ea                     ;confuse disassemblers....
confuzzled:
        push    bp
        sub     bp,offset Displaced
        ret
;------------------------------------------------------------------------
Key1            dw      0
Key2            dw      0
;------------------------------------------------------------------------
Storage_Bytes   db      90,90,0cdh,20
;------------------------------------------------------------------------
Password        db      'Passwordtest'
Entered_Pass    db      '            '
;------------------------------------------------------------------------
end_prog:
end start