passwordmanager.asm

.MODEL SMALL
.STACK 100H

.DATA
; -----------------------
; Messages
; -----------------------
welcome_msg DB 0Dh,0Ah,'--- PASSWORD MANAGER ---',0Dh,0Ah,'$'
ask_master  DB 0Dh,0Ah,'Enter Master Password: $'
wrong_pass  DB 0Dh,0Ah,'Wrong Password! Exiting...$'
login_ok    DB 0Dh,0Ah,'Login Successful!$'

menu_msg DB 0Dh,0Ah,'1. Add Account',0Dh,0Ah
         DB '2. View Accounts',0Dh,0Ah
         DB '3. Delete All',0Dh,0Ah
         DB '4. Exit',0Dh,0Ah
         DB 'Enter choice: $'

ask_user   DB 0Dh,0Ah,'Enter Username: $'
ask_pass   DB 0Dh,0Ah,'Enter Password: $'
acc_added  DB 0Dh,0Ah,'Account added.$'
no_acc_msg DB 0Dh,0Ah,'No accounts found.$'
all_del    DB 0Dh,0Ah,'All accounts deleted.$'

colon_sp   DB ': $'

; -----------------------
; Data storage
; -----------------------
master_pass DB 'admin',0

MAX_ACC   EQU 5
MAX_LEN   EQU 20

usernames DB MAX_ACC*MAX_LEN DUP('$')
passwords DB MAX_ACC*MAX_LEN DUP('$')

plain_pw  DB MAX_LEN DUP('$')   ; buffer for decrypted password
account_cnt DB 0

choice DB ?

; input buffer (for int 21h AH=0Ah)
inbuf DB 21,0,21 DUP('$')

; -----------------------
; Code
; -----------------------
.CODE
MAIN PROC
    MOV AX,@DATA
    MOV DS,AX

    ; Welcome + login
    MOV DX,OFFSET welcome_msg
    MOV AH,09h
    INT 21h

    CALL LOGIN
    CMP AL,0
    JE EXIT_PROG

MAIN_LOOP:
    MOV DX,OFFSET menu_msg
    MOV AH,09h
    INT 21h

    ; read choice (1 char)
    MOV AH,01h
    INT 21h
    MOV choice,AL

    CMP AL,'1'
    JE DO_ADD
    CMP AL,'2'
    JE DO_VIEW
    CMP AL,'3'
    JE DO_DELETE
    CMP AL,'4'
    JE EXIT_PROG

    JMP MAIN_LOOP

DO_ADD:
    CALL ADD_ACCOUNT
    JMP MAIN_LOOP

DO_VIEW:
    CALL VIEW_ACCOUNTS
    JMP MAIN_LOOP

DO_DELETE:
    CALL DELETE_ALL
    JMP MAIN_LOOP

EXIT_PROG:
    MOV AX,4C00h
    INT 21h
MAIN ENDP

; -----------------------
; Procedures
; -----------------------

; -------- LOGIN --------
LOGIN PROC
    MOV DX,OFFSET ask_master
    MOV AH,09h
    INT 21h

    CALL READ_STRING

    ; compare length first
    MOV CL,[inbuf+1]       ; typed length
    CMP CL,5               ; "admin" length = 5
    JNE bad_pass

    ; compare characters
    LEA SI,inbuf+2         ; typed chars
    LEA DI,master_pass     ; "admin"
check_loop:
    LODSB
    CMP AL,[DI]
    JNE bad_pass
    INC DI
    DEC CL
    JNZ check_loop

    ; all matched
    MOV DX,OFFSET login_ok
    MOV AH,09h
    INT 21h
    MOV AL,1
    RET

bad_pass:
    MOV DX,OFFSET wrong_pass
    MOV AH,09h
    INT 21h
    MOV AL,0
    RET
LOGIN ENDP


; -------- ADD_ACCOUNT --------
ADD_ACCOUNT PROC
    CMP account_cnt,MAX_ACC
    JAE add_full

    ; username
    MOV DX,OFFSET ask_user
    MOV AH,09h
    INT 21h
    CALL READ_STRING
    LEA SI,inbuf+2
    MOV CL,[inbuf+1]
    MOV DI,OFFSET usernames
    CALL GET_REC_PTR
    CALL COPY_TO_RECORD

    ; password
    MOV DX,OFFSET ask_pass
    MOV AH,09h
    INT 21h
    CALL READ_STRING
    LEA SI,inbuf+2
    MOV CL,[inbuf+1]
    MOV DI,OFFSET passwords
    CALL GET_REC_PTR
    CALL ENCRYPT_TO_RECORD

    INC account_cnt

    MOV DX,OFFSET acc_added
    MOV AH,09h
    INT 21h
    RET

add_full:
    MOV DX,OFFSET no_acc_msg
    MOV AH,09h
    INT 21h
    RET
ADD_ACCOUNT ENDP

; -------- VIEW_ACCOUNTS --------
VIEW_ACCOUNTS PROC
    CMP account_cnt,0
    JE va_none

    XOR BX,BX      ; index=0
va_next:
    CMP BL,account_cnt
    JAE va_done

    ; print username
    MOV DX,OFFSET usernames
    CALL GET_REC_PTR
    MOV DX,DI
    MOV AH,09h
    INT 21h

    ; print ": "
    MOV DX,OFFSET colon_sp
    MOV AH,09h
    INT 21h

    ; decrypt password
    MOV DX,OFFSET passwords
    CALL GET_REC_PTR
    MOV SI,DI
    LEA DI,plain_pw
    CALL DECRYPT_FROM_RECORD

    MOV DX,OFFSET plain_pw
    MOV AH,09h
    INT 21h

    ; newline
    MOV DL,0Dh
    MOV AH,02h
    INT 21h
    MOV DL,0Ah
    INT 21h

    INC BL
    JMP va_next

va_done:
    RET

va_none:
    MOV DX,OFFSET no_acc_msg
    MOV AH,09h
    INT 21h
    RET
VIEW_ACCOUNTS ENDP

; -------- DELETE_ALL --------
DELETE_ALL PROC
    MOV account_cnt,0
    MOV DX,OFFSET all_del
    MOV AH,09h
    INT 21h
    RET
DELETE_ALL ENDP

; -------- Utilities --------

; READ_STRING -> reads into inbuf
READ_STRING PROC
    MOV DX,OFFSET inbuf
    MOV AH,0Ah
    INT 21h
    RET
READ_STRING ENDP

; get record pointer (DI = base, BX=index)
GET_REC_PTR PROC
    MOV AX,BX
    MOV CL,MAX_LEN
    MUL CL
    ADD DI,AX
    RET
GET_REC_PTR ENDP

; copy CL bytes from SI->DI, add '$'
COPY_TO_RECORD PROC
cpr_loop:
    CMP CL,0
    JE cpr_end
    LODSB
    STOSB
    DEC CL
    JMP cpr_loop
cpr_end:
    MOV AL,'$'
    STOSB
    RET
COPY_TO_RECORD ENDP

; encrypt copy with +3
ENCRYPT_TO_RECORD PROC
etr_loop:
    CMP CL,0
    JE etr_end
    LODSB
    ADD AL,3
    STOSB
    DEC CL
    JMP etr_loop
etr_end:
    MOV AL,'$'
    STOSB
    RET
ENCRYPT_TO_RECORD ENDP

; decrypt from SI -> DI until '$'
DECRYPT_FROM_RECORD PROC
dfr_loop:
    LODSB
    CMP AL,'$'
    JE dfr_done
    SUB AL,3
    STOSB
    JMP dfr_loop
dfr_done:
    MOV AL,'$'
    STOSB
    RET
DECRYPT_FROM_RECORD ENDP

END MAIN