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Cracking 101 - 1990 edition: Lesson 4
CRACKING 101 - 1990 Edition
Lesson 4
revision 1
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ REMOVING THE DOC CHECK FOR STAR CONTROL ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
<
Added for revision 1 -
First, let me tell you about a major fuckup I made.
When I first wrote this file, I left out a major part of the
patch. For all of the user who got that version, I'm sorry
but even I make mistakes at 3:00 in the morning. Anyway,
just replace the original with this updated version
- Buckaroo Banzai
>
Hey, Buckaroo Banzai .. Cracking Guru back once again to
help you lesser crackist learn. This time, we will be going
over Star Control. This is the last lesson in the original
4. From here on out, I will simply release lessons as I
write them.
I want to say a few things about some of the groups out
there right now. Speed isn't everything. I really wish that
for example when you remove a doc check, most of us want it
REMOVED. We don't want to have to enter your group name or
even typing 1 letter is to much. We shouldn't even see the
menu for the doc check. Now, I don't direct this to all of
you, but there seems to have been a move from quality to
quickness. Let's go back to the days of SPI (and INC when
they were first getting started) and crack right. If there
is a doc check, remove it, not just fake it.
Nuff said, on with the tutorial.
Star Control (SC for here out) is a preaty good game.
The protection on it wasn't too hard, but if you didn't read
enough in to it, you would just kill the title music also.
So, how do we go about cracking SC. Well for this one I
opted to break out when SC asks for the code from the code
wheel. Originaly I did this just for the hell of it, but it
turned out to be a luck guess and made life a lot easier.
As usual we will be using periscope to crack SC. I used
PSKEY (using int 3 as the trap interrupt not int 2) to pop in
at the input routine. So lets get started. Load up PS and
PSKEY, then execute Star Control. When you get to the doc
check, break out.
Now you should be at the usual IRET insturction that's
part of PSKEY. Now comes the tricky part. Since we are
using a key trap to break out during the input sequence, we
could be anywhere inside the entire input routine. So in
cases like this I suggest finding a reference point.
So how do you pick the reference point. Well, since
this doc check must be entered via the keyboard you can bet
somewhere it will call INT 16h (bios keyboard) (although
there are times when this is not true, it rare). I think we
should go off and find that call to that interrupt.
So we trace (using the 'T' command) through some code
and finally come apon the follow subroutine ....
( NOTE: all comments were added by me )
; This is the actual routine that is used to get a key
2A00:09D4 55 PUSH BP
2A00:09D5 8BEC MOV BP,SP
2A00:09D7 8A6606 MOV AH,[BP+06]
2A00:09DA 8AD4 MOV DL,AH
2A00:09DC 80E20F AND DL,0F
2A00:09DF CD16 INT 16 ; Call to bios. We will
2A00:09E1 7509 JNZ 09EC ; use this as our
2A00:09E3 80FA01 CMP DL,01 ; reference point
2A00:09E6 7504 JNZ 09EC
2A00:09E8 33C0 XOR AX,AX
2A00:09EA EB0A JMP 09F6
2A00:09EC 80FA02 CMP DL,02
2A00:09EF 7405 JZ 09F6
2A00:09F1 0BC0 OR AX,AX
2A00:09F3 7501 JNZ 09F6
2A00:09F5 48 DEC AX
2A00:09F6 5D POP BP
2A00:09F7 CB RETF
So we write down the address of our REFERENCE point and
get ready to procede. Now, It's really kinda boring to keep
trying to trace through the entire input routine while trying
to enter the code string, so what we want to do next, is to
figure out the input routine. A quick look at this last
section of code shows that it only reads in a character but
really does not handle it.
So, we exit via the RETF at 9F7 enter the next level of
the subroutine. Again, if you manual trace through this
routine (as well as the next level up) you see that it simple
exits out rather quickly. This is definitly not the top loop
of the imput routine.
So, we trace through the next level up, and again exit
quickly to a higher level. But this time, as we trace
through, we find that the it loops back on itself. AHA, the
outer input loop. Here is the code to the entire input loop.
I have marked the place where you should enter from the lower
level.
( String input loop -- Outer level )
7C00:0835 FF365220 PUSH [2052]
7C00:0839 FF365020 PUSH [2050]
7C00:083D 9A2802FD41 CALL 41FD:0228 ; Entery here
7C00:0842 888670FE MOV [BP+FE70],AL
7C00:0946 0AC0 OR AL,AL
7C00:0848 7503 JNZ 084D
7C00:084A E99200 JMP 08DF
7C00:084D 2AE4 SUB AH,AH
7C00:084F 2D0800 SUB AX,0008
7C00:0852 745A JZ 08AE
7C00:0854 48 DEC AX
7C00:0855 48 DEC AX
7C00:0856 7503 JNZ 085B
7C00:0858 E90901 JMP 0964
7C00:085B 2D0300 SUB AX,0003
7C00:085E 7503 JNZ 0863
7C00:0860 E90101 JMP 0964
7C00:0863 8A9E70FE MOV BL,[BP+FE70]
7C00:0867 2AFF SUB BH,BH
7C00:0869 F687790B57 TEST BYTE PTR [BX+0B79],57
7C00:086E 746F JZ 08DF
7C00:0870 F687790B03 TEST BYTE PTR [BX+0B79],03
7C00:0875 740C JZ 0883
7C00:0877 F687790B02 TEST BYTE PTR [BX+0B79],02
7C00:087C 7405 JZ 0883
7C00:087E 80AE70FE20 SUB BYTE PTR [BP+FE70],20
7C00:0883 8A8670FE MOV AL,[BP+FE70]
7C00:0887 C49E7EFE LES BX,[BP+FE7E]
7C00:088B 8BB682FE MOV SI,[BP+FE82]
7C00:088F 26 ES:
7C00:0890 8800 MOV [BX+SI],AL
7C00:0892 FF8682FE INC WORD PTR [BP+FE82]
7C00:0896 FFB688FE PUSH [BP+FE88]
7C00:089A 8D8678FE LEA AX,[BP+FE78]
7C00:089E 50 PUSH AX
7C00:089F 9A56049324 CALL 2493:0456
7C00:08A4 83C404 ADD SP,+04
7C00:08A7 0BC0 OR AX,AX
7C00:08A9 7534 JNZ 08DF
7C00:08AB EB27 JMP 08D4
7C00:08AD 90 NOP
7C00:08AE 83BE82FE00 CMP WORD PTR [BP+FE82],+00
7C00:08B3 7404 JZ 08B9
7C00:08B5 FF8E82FE DEC WORD PTR [BP+FE82]
7C00:08B9 B008 MOV AL,08
7C00:08BB 50 PUSH AX
7C00:08BC 9A1003443D CALL 3D44:0310
7C00:08C1 8D8684FE LEA AX,[BP+FE84]
7C00:08C5 16 PUSH SS
7C00:08C6 50 PUSH AX
7C00:08C7 9A6A00843D CALL 3D84:006A
7C00:08CC B047 MOV AL,47
7C00:08CE 50 PUSH AX
7C00:08CF 9A1003443D CALL 3D44:0310
7C00:08D4 8D8678FE LEA AX,[BP+FE78]
7C00:08D8 16 PUSH SS
7C00:08D9 50 PUSH AX
7C00:08DA 9A8202C93C CALL 3CC9:0282
7C00:08DF 83BE8CFE00 CMP WORD PTR [BP+FE8C],+00
7C00:08E4 7503 JNZ 08E9
7C00:08E6 E94CFF JMP 0835 ; <ÄÄÄ¿
³
as you can see, at this point it loops back on itself.
This is what tells use that it's the outer loop. Knowing
that, we can just set a code breakpoint at 8E9 (the next
instruction after the loop) and execute the code.
At this point, the SC will pause waiting for you to
enter the code key. Use the code wheel and enter the correct
key (after all, it's kinda hard to crack a game without
having the proper codes right...)
So, we have now exited the input loop with everything
intact (ie: the proper code was entered). Next step is to
figure out what happens when the proper code is entered.
Well, since you have entered the proper code, just follow
this routine out. Remember back to lesson 2. What we want
to do is find the call the to routine that does the doc check
and remove it somehow (a PROPER crack). So since everything
is in the right place, if we just keep jumping over the code
we should find our way out.
So after jumping over many instructions, we come the the
follow piece of code
7C00:0B74 8BE5 MOV SP,BP
7C00:0B76 5D POP BP
7C00:0B77 CB RETF
By now, you should know that what you are looking at is
the exit routine for a higher level language's (C or pascal)
code. So we have found the end of the doc check. After
tracing through the RETF you find yourself looking down a cmp
and a conditional jump. Here is the code (NOTE! I have
included the actual call to the doc check just for reference)
45E2:0235 9A46010F4A CALL 7C00:146 ; Call to Doc Check
45E2:023A 83C404 ADD SP,+04
45E2:023D 0BC0 OR AX,AX
45E2:023F 7465 JZ 02A6
Notice the value of the AX register. Since right after
the doc check, it is acted upon, then it has some importance.
So, now that we know where the doc check takes place, how do
we remove it.
Well, We could patch it with the code
45E2:0235 B40100 MOV AX,0001
45E2:0238 90 NOP
45E2:0239 90 NOP
This patch will work (I know, it's how I first patched
the program). But there is one small problem. If you run
the program after adding this patch, you will find that the
title music doesn't play. So, this is now a good place to
put the patch.
So where then. Well, make note of the address of the
call to the doc check. Now, restart the process but this
time right after SC switches in to graphics mode, break out.
Now, set a breakpoint at the address from above (in my
case 45E2:0235). Let SC run in to the intro. You will find
that although the title screen comes up, the music doesn't
kick in before the breakpoint is reached.
No, they couldn't...they wouldn't.. well they did. The
music routines for the intro are stored in the routine for
the doc check. Here is the entire doc check. I have
commented on some of the code
; these first few calls seem to load something from disk
7C00:0146 55 PUSH BP
7C00:0147 8BEC MOV BP,SP
7C00:0149 81EC9001 SUB SP,0190
7C00:014D 57 PUSH DI
7C00:014E 56 PUSH SI
7C00:014F 8B4608 MOV AX,[BP+08]
7C00:0152 0B4606 OR AX,[BP+06]
7C00:0155 740E JZ 0165
7C00:0157 FF7608 PUSH [BP+08]
7C00:015A FF7606 PUSH [BP+06]
7C00:015D 9A65341E2D CALL 2D1E:3465
7C00:0162 83C404 ADD SP,+04
7C00:0165 FF365220 PUSH [2052]
7C00:0169 FF365020 PUSH [2050]
7C00:016D 9A2802FD41 CALL 41FD:0228
7C00:0172 0AC0 OR AL,AL
7C00:0174 75EF JNZ 0165
7C00:0176 B80200 MOV AX,0002
7C00:0179 898664FF MOV [BP+FF64],AX
7C00:017D 898672FF MOV [BP+FF72],AX
7C00:0181 2BC0 SUB AX,AX
7C00:0183 898662FF MOV [BP+FF62],AX
7C00:0187 89866AFF MOV [BP+FF6A],AX
7C00:018B 898674FF MOV [BP+FF74],AX
7C00:018F B80100 MOV AX,0001
7C00:0192 898666FF MOV [BP+FF66],AX
7C00:0196 89866CFF MOV [BP+FF6C],AX
7C00:019A 898670FF MOV [BP+FF70],AX
7C00:019E 898676FF MOV [BP+FF76],AX
7C00:01A2 B80300 MOV AX,0003
7C00:01A5 898668FF MOV [BP+FF68],AX
7C00:01A9 89866EFF MOV [BP+FF6E],AX
7C00:01AD 898678FF MOV [BP+FF78],AX
; Although I have NO IDEA what the hell is being setup
; here I suspect that it is the must
7C00:01B1 C746860400 MOV WORD PTR [BP-7A],0004
7C00:01B6 C746880100 MOV WORD PTR [BP-78],0001
7C00:01BB C7468A0200 MOV WORD PTR [BP-76],0002
7C00:01C0 C7468C0000 MOV WORD PTR [BP-74],0000
7C00:01C5 C7468E0000 MOV WORD PTR [BP-72],0000
7C00:01CA C746900500 MOV WORD PTR [BP-70],0005
7C00:01CF C746920600 MOV WORD PTR [BP-6E],0006
7C00:01D4 C746940700 MOV WORD PTR [BP-6C],0007
7C00:01D9 C746960C00 MOV WORD PTR [BP-6A],000C
7C00:01DE 894698 MOV [BP-68],AX
7C00:01E1 C7469A0500 MOV WORD PTR [BP-66],0005
7C00:01E6 C7469C0D00 MOV WORD PTR [BP-64],000D
7C00:01EB C7469E0000 MOV WORD PTR [BP-62],0000
7C00:01F0 C746A00100 MOV WORD PTR [BP-60],0001
7C00:01F5 C746A20200 MOV WORD PTR [BP-5E],0002
7C00:01FA C746A40800 MOV WORD PTR [BP-5C],0008
7C00:01FF B80400 MOV AX,0004
7C00:0202 8946A6 MOV [BP-5A],AX
7C00:0205 8946A8 MOV [BP-58],AX
7C00:0208 C746AA0600 MOV WORD PTR [BP-56],0006
7C00:020D C746AC0800 MOV WORD PTR [BP-54],0008
7C00:0212 C746AE0700 MOV WORD PTR [BP-52],0007
7C00:0217 C746B00900 MOV WORD PTR [BP-50],0009
7C00:021C C746B20A00 MOV WORD PTR [BP-4E],000A
7C00:0221 8946B4 MOV [BP-4C],AX
7C00:0224 C746B60C00 MOV WORD PTR [BP-4A],000C
7C00:0229 C746B80300 MOV WORD PTR [BP-48],0003
7C00:022E C746BA0B00 MOV WORD PTR [BP-46],000B
7C00:0233 C746BC0D00 MOV WORD PTR [BP-44],000D
7C00:0238 C746BE0B00 MOV WORD PTR [BP-42],000B
7C00:023D C746C00500 MOV WORD PTR [BP-40],0005
7C00:0242 C746C20100 MOV WORD PTR [BP-3E],0001
7C00:0247 C746C40700 MOV WORD PTR [BP-3C],0007
7C00:024C C746C60000 MOV WORD PTR [BP-3A],0000
7C00:0251 C746C80600 MOV WORD PTR [BP-38],0006
7C00:0256 C746CA0200 MOV WORD PTR [BP-36],0002
7C00:025B C746CC0300 MOV WORD PTR [BP-34],0003
7C00:0260 C746CE0800 MOV WORD PTR [BP-32],0008
7C00:0265 C746D00900 MOV WORD PTR [BP-30],0009
7C00:026A C746D20A00 MOV WORD PTR [BP-2E],000A
7C00:026F C746D40B00 MOV WORD PTR [BP-2C],000B
7C00:0274 C746D60C00 MOV WORD PTR [BP-2A],000C
7C00:0279 C746D80A00 MOV WORD PTR [BP-28],000A
7C00:027E C746DA0500 MOV WORD PTR [BP-26],0005
7C00:0283 C746DC0D00 MOV WORD PTR [BP-24],000D
7C00:0288 C746DE0800 MOV WORD PTR [BP-22],0008
7C00:028D C746E00900 MOV WORD PTR [BP-20],0009
7C00:0292 C746E20300 MOV WORD PTR [BP-1E],0003
7C00:0297 C746E40B00 MOV WORD PTR [BP-1C],000B
7C00:029C C78692FE0000 MOV WORD PTR [BP+FE92],0000
7C00:02A2 C78694FE2B00 MOV WORD PTR [BP+FE94],002B
7C00:02A8 C78696FE0200 MOV WORD PTR [BP+FE96],0002
7C00:02AE C78698FE0300 MOV WORD PTR [BP+FE98],0003
7C00:02B4 89869AFE MOV [BP+FE9A],AX
7C00:02B8 C7869CFE0500 MOV WORD PTR [BP+FE9C],0005
7C00:02BE C7869EFE0600 MOV WORD PTR [BP+FE9E],0006
7C00:02C4 C786A0FE0E00 MOV WORD PTR [BP+FEA0],000E
7C00:02CA C786A2FE2B00 MOV WORD PTR [BP+FEA2],002B
7C00:02D0 C786A4FE0900 MOV WORD PTR [BP+FEA4],0009
7C00:02D6 C786A6FE0A00 MOV WORD PTR [BP+FEA6],000A
7C00:02DC C786A8FE0B00 MOV WORD PTR [BP+FEA8],000B
7C00:02E2 C786AAFE0C00 MOV WORD PTR [BP+FEAA],000C
7C00:02E8 C786ACFE2B00 MOV WORD PTR [BP+FEAC],002B
7C00:02EE C786AEFE0F00 MOV WORD PTR [BP+FEAE],000F
7C00:02F4 C786B0FE0D00 MOV WORD PTR [BP+FEB0],000D
7C00:02FA C786B2FE1000 MOV WORD PTR [BP+FEB2],0010
7C00:0300 C786B4FE1100 MOV WORD PTR [BP+FEB4],0011
7C00:0306 C786B6FE1200 MOV WORD PTR [BP+FEB6],0012
7C00:030C C786B8FE1300 MOV WORD PTR [BP+FEB8],0013
7C00:0312 C786BAFE1400 MOV WORD PTR [BP+FEBA],0014
7C00:0318 C786BCFE1500 MOV WORD PTR [BP+FEBC],0015
7C00:031E C786BEFE1600 MOV WORD PTR [BP+FEBE],0016
7C00:0324 C786C0FE1700 MOV WORD PTR [BP+FEC0],0017
7C00:032A C786C2FE0800 MOV WORD PTR [BP+FEC2],0008
7C00:0330 C786C4FE1800 MOV WORD PTR [BP+FEC4],0018
7C00:0336 C786C6FE2B00 MOV WORD PTR [BP+FEC6],002B
7C00:033C C786C8FE1900 MOV WORD PTR [BP+FEC8],0019
7C00:0342 C786CAFE2B00 MOV WORD PTR [BP+FECA],002B
7C00:0348 C786CCFE1A00 MOV WORD PTR [BP+FECC],001A
7C00:034E C786CEFE1B00 MOV WORD PTR [BP+FECE],001B
7C00:0354 C786D0FE1C00 MOV WORD PTR [BP+FED0],001C
7C00:035A C786D2FE1D00 MOV WORD PTR [BP+FED2],001D
7C00:0360 C786D4FE1E00 MOV WORD PTR [BP+FED4],001E
7C00:0366 C786D6FE1F00 MOV WORD PTR [BP+FED6],001F
7C00:036C C786D8FE2000 MOV WORD PTR [BP+FED8],0020
7C00:0372 C786DAFE2100 MOV WORD PTR [BP+FEDA],0021
7C00:0378 C786DCFE0700 MOV WORD PTR [BP+FEDC],0007
7C00:037E C786DEFE2200 MOV WORD PTR [BP+FEDE],0022
7C00:0384 C786E0FE2300 MOV WORD PTR [BP+FEE0],0023
7C00:038A C786E2FE2400 MOV WORD PTR [BP+FEE2],0024
7C00:0390 C786E4FE2500 MOV WORD PTR [BP+FEE4],0025
7C00:0396 C786E6FE2600 MOV WORD PTR [BP+FEE6],0026
7C00:039C C786E8FE2B00 MOV WORD PTR [BP+FEE8],002B
7C00:03A2 C786EAFE2700 MOV WORD PTR [BP+FEEA],0027
7C00:03A8 C786ECFE2800 MOV WORD PTR [BP+FEEC],0028
7C00:03AE C786EEFE2900 MOV WORD PTR [BP+FEEE],0029
7C00:03B4 C786F0FE2A00 MOV WORD PTR [BP+FEF0],002A
7C00:03BA 8D46F4 LEA AX,[BP-0C]
7C00:03BD 50 PUSH AX
7C00:03BE 8D867AFF LEA AX,[BP+FF7A]
7C00:03C2 50 PUSH AX
7C00:03C3 8D862CFF LEA AX,[BP+FF2C]
7C00:03C7 50 PUSH AX
7C00:03C8 8D8628FF LEA AX,[BP+FF28]
7C00:03CC 50 PUSH AX
7C00:03CD E832FC CALL 0002 ; Music Plays
7C00:03D0 0BC0 OR AX,AX
7C00:03D2 7503 JNZ 03D7
7C00:03D4 E99B07 JMP 0B72
7C00:03D7 FF36AA1E PUSH [1EAA]
7C00:03DB 9A0200443D CALL 3D44:0002
7C00:03E0 FF36AE1E PUSH [1EAE]
7C00:03E4 FF36AC1E PUSH [1EAC]
7C00:03E8 9A0C008D3D CALL 3D8D:000C
7C00:03ED B80201 MOV AX,0102
7C00:03F0 50 PUSH AX
7C00:03F1 9ADE02443D CALL 3D44:02DE
7C00:03F6 B80400 MOV AX,0004
7C00:03F9 BA4000 MOV DX,0040
7C00:03FC 52 PUSH DX
7C00:03FD 50 PUSH AX
7C00:03FE 8D868CFE LEA AX,[BP+FE8C]
7C00:0402 50 PUSH AX
7C00:0403 9A7000963B CALL 3B96:0070 ; Music plays
7C00:0408 89868EFE MOV [BP+FE8E],AX
7C00:040C 899690FE MOV [BP+FE90],DX
7C00:0410 0BD0 OR DX,AX
7C00:0412 7471 JZ 0485
7C00:0414 2BC0 SUB AX,AX
7C00:0416 898686FE MOV [BP+FE86],AX
7C00:041A 898684FE MOV [BP+FE84],AX
7C00:041E FFB690FE PUSH [BP+FE90]
7C00:0422 FFB68EFE PUSH [BP+FE8E]
7C00:0426 9A0A00F93C CALL 3CF9:000A
7C00:042B 898688FE MOV [BP+FE88],AX
7C00:042F 89968AFE MOV [BP+FE8A],DX
7C00:0433 833EB41E00 CMP WORD PTR [1EB4],+00
7C00:0438 7514 JNZ 044E
7C00:043A 8B4608 MOV AX,[BP+08]
7C00:043D 0B4606 OR AX,[BP+06]
7C00:0440 740C JZ 044E
7C00:0442 B80100 MOV AX,0001
7C00:0445 50 PUSH AX
7C00:0446 9AF4019324 CALL 2493:01F4
7C00:044B 83C402 ADD SP,+02
7C00:044E 2AC0 SUB AL,AL
7C00:0450 50 PUSH AX
7C00:0451 9A4803443D CALL 3D44:0348
7C00:0456 9A57331E2D CALL 2D1E:3357
7C00:045B 9A9911A73B CALL 3BA7:1199
7C00:0460 8D8684FE LEA AX,[BP+FE84]
7C00:0464 16 PUSH SS
7C00:0465 50 PUSH AX
7C00:0466 9A04007E3D CALL 3D7E:0004 ; Music plays
7C00:046B FFB68AFE PUSH [BP+FE8A]
7C00:046F FFB688FE PUSH [BP+FE88]
7C00:0473 9AF001F93C CALL 3CF9:01F0
7C00:0478 FFB690FE PUSH [BP+FE90]
7C00:047C FFB68EFE PUSH [BP+FE8E]
7C00:0480 9A78068D3D CALL 3D8D:0678 ; Music plays
7C00:0485 8B4608 MOV AX,[BP+08]
7C00:0488 0B4606 OR AX,[BP+06]
7C00:048B 7429 JZ 04B6
7C00:048D 833EB41E00 CMP WORD PTR [1EB4],+00
7C00:0492 740C JZ 04A0
7C00:0494 B80100 MOV AX,0001
7C00:0497 50 PUSH AX
7C00:0498 9AF4019324 CALL 2493:01F4 ; Music Plays
7C00:049D 83C402 ADD SP,+02
7C00:04A0 9A8C341E2D CALL 2D1E:348C
7C00:04A5 FF7608 PUSH [BP+08]
7C00:04A8 FF7606 PUSH [BP+06]
7C00:04AB 9A2A006342 CALL 4263:002A
7C00:04B0 50 PUSH AX
7C00:04B1 9A54006342 CALL 4263:0054
; this is the start of the actual doc check. OH! As you can
; tell, I wasn't too intrested in the music routines, but
; thought it might be fun to track them down
7C00:04B6 9AD0098D3D CALL 3D8D:09D0 ; Show Doc check
; screen
7C00:04BB B80301 MOV AX,0103
7C00:04BE 50 PUSH AX
7C00:04BF 9ADE02443D CALL 3D44:02DE
7C00:04C4 C746F60B00 MOV WORD PTR [BP-0A],000B
7C00:04C9 C746F87900 MOV WORD PTR [BP-08],0079
7C00:04CE C746FA2801 MOV WORD PTR [BP-06],0128
7C00:04D3 C746FC4500 MOV WORD PTR [BP-04],0045
7C00:04D8 B008 MOV AL,08
7C00:04DA 50 PUSH AX
7C00:04DB 9A1003443D CALL 3D44:0310
7C00:04E0 8D867AFF LEA AX,[BP+FF7A]
7C00:04E4 16 PUSH SS
7C00:04E5 50 PUSH AX
7C00:04E6 9A36007E3D CALL 3D7E:0036 ; Show alien's face
7C00:04EB C746E6A000 MOV WORD PTR [BP-1A],00A0
7C00:04F0 C746EA0100 MOV WORD PTR [BP-16],0001
7C00:04F5 C746840300 MOV WORD PTR [BP-7C],0003
7C00:04FA 2AC0 SUB AL,AL
7C00:04FC 50 PUSH AX
7C00:04FD 9A1003443D CALL 3D44:0310
7C00:0502 8B46F8 MOV AX,[BP-08]
7C00:0505 050700 ADD AX,0007
7C00:0508 8946E8 MOV [BP-18],AX
7C00:050B FFB62EFF PUSH [BP+FF2E]
7C00:050F FFB62CFF PUSH [BP+FF2C]
7C00:0513 FFB62EFF PUSH [BP+FF2E]
7C00:0517 FFB62CFF PUSH [BP+FF2C]
7C00:051B 9AE400FC44 CALL 44FC:00E4
7C00:0520 8BF0 MOV SI,AX
7C00:0522 9A1201E245 CALL 45E2:0112
7C00:0527 B90500 MOV CX,0005
7C00:052A 8BD0 MOV DX,AX
7C00:052C 8BC6 MOV AX,SI
7C00:052E 8BDA MOV BX,DX
7C00:0530 2BD2 SUB DX,DX
7C00:0532 F7F1 DIV CX
7C00:0534 8BD0 MOV DX,AX
7C00:0536 4A DEC DX
7C00:0537 8BC3 MOV AX,BX
7C00:0539 8BDA MOV BX,DX
7C00:053B 2BD2 SUB DX,DX
7C00:053D F7F3 DIV BX
7C00:053F 42 INC DX
7C00:0540 8BC2 MOV AX,DX
7C00:0542 D1E2 SHL DX,1
7C00:0544 D1E2 SHL DX,1
7C00:0546 03D0 ADD DX,AX
7C00:0548 52 PUSH DX
7C00:0549 9A2801FC44 CALL 44FC:0128
7C00:054E 89868EFE MOV [BP+FE8E],AX
7C00:0552 899690FE MOV [BP+FE90],DX
7C00:0556 C78672FE0000 MOV WORD PTR [BP+FE72],0000
; This is the start of the loop the prints out the stupid
; message
7C00:055C 52 PUSH DX
7C00:055D 50 PUSH AX
7C00:055E 9A4602FC44 CALL 44FC:0246
7C00:0563 8946EC MOV [BP-14],AX
7C00:0566 8956EE MOV [BP-12],DX
7C00:0569 FFB690FE PUSH [BP+FE90]
7C00:056D FFB68EFE PUSH [BP+FE8E]
7C00:0571 9AF201FC44 CALL 44FC:01F2
7C00:0576 8946F0 MOV [BP-10],AX
7C00:0579 8D46E6 LEA AX,[BP-1A]
7C00:057C 16 PUSH SS
7C00:057D 50 PUSH AX
7C00:057E 9A8202C93C CALL 3CC9:0282
7C00:0583 8346E80A ADD WORD PTR [BP-18],+0A
7C00:0587 FFB690FE PUSH [BP+FE90]
7C00:058B FFB68EFE PUSH [BP+FE8E]
7C00:058F B80100 MOV AX,0001
7C00:0592 50 PUSH AX
7C00:0593 9A7E01FC44 CALL 44FC:017E
7C00:0598 89868EFE MOV [BP+FE8E],AX
7C00:059C 899690FE MOV [BP+FE90],DX
7C00:05A0 FF8672FE INC WORD PTR [BP+FE72]
7C00:05A4 83BE72FE05 CMP WORD PTR [BP+FE72],+05
7C00:05A9 7CB1 JL 055C
; Reads in the code to check (I think. Oh hell it really
; doesn't matter)
7C00:05AB 9A1201E245 CALL 45E2:0112
7C00:05B0 B90C00 MOV CX,000C
7C00:05B3 99 CWD
7C00:05B4 F7F9 IDIV CX
7C00:05B6 895682 MOV [BP-7E],DX
7C00:05B9 9A1201E245 CALL 45E2:0112
7C00:05BE B90C00 MOV CX,000C
7C00:05C1 99 CWD
7C00:05C2 F7F9 IDIV CX
7C00:05C4 8956F2 MOV [BP-0E],DX
7C00:05C7 9A1201E245 CALL 45E2:0112
7C00:05CC B90C00 MOV CX,000C
7C00:05CF 99 CWD
7C00:05D0 F7F9 IDIV CX
7C00:05D2 8956FE MOV [BP-02],DX
7C00:05D5 9A1201E245 CALL 45E2:0112
7C00:05DA B90C00 MOV CX,000C
7C00:05DD 99 CWD
7C00:05DE F7F9 IDIV CX
7C00:05E0 8996F4FE MOV [BP+FEF4],DX
7C00:05E4 FFB62AFF PUSH [BP+FF2A]
7C00:05E8 FFB628FF PUSH [BP+FF28]
7C00:05EC FF7682 PUSH [BP-7E]
7C00:05EF 9A2801FC44 CALL 44FC:0128
7C00:05F4 89868EFE MOV [BP+FE8E],AX
7C00:05F8 899690FE MOV [BP+FE90],DX
7C00:05FC 52 PUSH DX
7C00:05FD 50 PUSH AX
7C00:05FE 8D86F6FE LEA AX,[BP+FEF6]
7C00:0602 16 PUSH SS
7C00:0603 50 PUSH AX
7C00:0604 9A9A02FC44 CALL 44FC:029A
7C00:0609 FFB62AFF PUSH [BP+FF2A]
7C00:060D FFB628FF PUSH [BP+FF28]
7C00:0611 8B46FE MOV AX,[BP-02]
7C00:0614 050C00 ADD AX,000C
7C00:0617 50 PUSH AX
7C00:0618 9A2801FC44 CALL 44FC:0128
7C00:061D 89868EFE MOV [BP+FE8E],AX
7C00:0621 899690FE MOV [BP+FE90],DX
7C00:0625 52 PUSH DX
7C00:0626 50 PUSH AX
7C00:0627 8DBEF6FE LEA DI,[BP+FEF6]
7C00:062B 16 PUSH SS
7C00:062C 07 POP ES
7C00:062D B9FFFF MOV CX,FFFF
7C00:0630 33C0 XOR AX,AX
7C00:0632 F2 REPNZ
7C00:0633 AE SCASB
7C00:0634 F7D1 NOT CX
7C00:0636 49 DEC CX
7C00:0637 8BF1 MOV SI,CX
7C00:0639 8D82F6FE LEA AX,[BP+SI+FEF6]
7C00:063D 16 PUSH SS
7C00:063E 50 PUSH AX
7C00:063F 9A9A02FC44 CALL 44FC:029A
7C00:0644 FFB62AFF PUSH [BP+FF2A]
7C00:0648 FFB628FF PUSH [BP+FF28]
7C00:064C 8B46F2 MOV AX,[BP-0E]
7C00:064F 051800 ADD AX,0018
7C00:0652 50 PUSH AX
7C00:0653 9A2801FC44 CALL 44FC:0128
7C00:0658 89868EFE MOV [BP+FE8E],AX
7C00:065C 899690FE MOV [BP+FE90],DX
7C00:0660 52 PUSH DX
7C00:0661 50 PUSH AX
7C00:0662 8DBEF6FE LEA DI,[BP+FEF6]
7C00:0666 16 PUSH SS
7C00:0667 07 POP ES
7C00:0668 B9FFFF MOV CX,FFFF
7C00:066B 33C0 XOR AX,AX
7C00:066D F2 REPNZ
7C00:066E AE SCASB
7C00:066F F7D1 NOT CX
7C00:0671 49 DEC CX
7C00:0672 8BF1 MOV SI,CX
7C00:0674 8D82F6FE LEA AX,[BP+SI+FEF6]
7C00:0678 16 PUSH SS
7C00:0679 50 PUSH AX
7C00:067A 9A9A02FC44 CALL 44FC:029A
7C00:067F FFB62AFF PUSH [BP+FF2A]
7C00:0683 FFB628FF PUSH [BP+FF28]
7C00:0687 8B86F4FE MOV AX,[BP+FEF4]
7C00:068B 052400 ADD AX,0024
7C00:068E 50 PUSH AX
7C00:068F 9A2801FC44 CALL 44FC:0128
7C00:0694 89868EFE MOV [BP+FE8E],AX
7C00:0698 899690FE MOV [BP+FE90],DX
7C00:069C 52 PUSH DX
7C00:069D 50 PUSH AX
7C00:069E 8DBEF6FE LEA DI,[BP+FEF6]
7C00:06A2 16 PUSH SS
7C00:06A3 07 POP ES
7C00:06A4 B9FFFF MOV CX,FFFF
7C00:06A7 33C0 XOR AX,AX
7C00:06A9 F2 REPNZ
7C00:06AA AE SCASB
7C00:06AB F7D1 NOT CX
7C00:06AD 49 DEC CX
7C00:06AE 8BF1 MOV SI,CX
7C00:06B0 8D82F6FE LEA AX,[BP+SI+FEF6]
7C00:06B4 16 PUSH SS
7C00:06B5 50 PUSH AX
7C00:06B6 9A9A02FC44 CALL 44FC:029A
7C00:06BB C746E8B200 MOV WORD PTR [BP-18],00B2
7C00:06C0 8D86F6FE LEA AX,[BP+FEF6]
7C00:06C4 8946EC MOV [BP-14],AX
7C00:06C7 8C56EE MOV [BP-12],SS
7C00:06CA 8DBEF6FE LEA DI,[BP+FEF6]
7C00:06CE 16 PUSH SS
7C00:06CF 07 POP ES
7C00:06D0 B9FFFF MOV CX,FFFF
7C00:06D3 33C0 XOR AX,AX
7C00:06D5 F2 REPNZ
7C00:06D6 AE SCASB
7C00:06D7 F7D1 NOT CX
7C00:06D9 49 DEC CX
7C00:06DA 894EF0 MOV [BP-10],CX
7C00:06DD B084 MOV AL,84
7C00:06DF 50 PUSH AX
7C00:06E0 9A1003443D CALL 3D44:0310
7C00:06E5 8D46E6 LEA AX,[BP-1A]
7C00:06E8 16 PUSH SS
7C00:06E9 50 PUSH AX
7C00:06EA 9A8202C93C CALL 3CC9:0282 ; Displays the code
; to check
7C00:06EF 8346E80A ADD WORD PTR [BP-18],+0A
7C00:06F3 FFB62AFF PUSH [BP+FF2A]
7C00:06F7 FFB628FF PUSH [BP+FF28]
7C00:06FB B85B00 MOV AX,005B
7C00:06FE 50 PUSH AX
7C00:06FF 9A2801FC44 CALL 44FC:0128
7C00:0704 89868EFE MOV [BP+FE8E],AX
7C00:0708 899690FE MOV [BP+FE90],DX
7C00:070C 52 PUSH DX
7C00:070D 50 PUSH AX
7C00:070E 9A4602FC44 CALL 44FC:0246
7C00:0713 8946EC MOV [BP-14],AX
7C00:0716 8956EE MOV [BP-12],DX
7C00:0719 FFB690FE PUSH [BP+FE90]
7C00:071D FFB68EFE PUSH [BP+FE8E]
7C00:0721 9AF201FC44 CALL 44FC:01F2
7C00:0726 8946F0 MOV [BP-10],AX
7C00:0729 2AC0 SUB AL,AL
7C00:072B 50 PUSH AX
7C00:072C 9A1003443D CALL 3D44:0310
7C00:0731 8D46E6 LEA AX,[BP-1A]
7C00:0734 16 PUSH SS
7C00:0735 50 PUSH AX
7C00:0736 9A8202C93C CALL 3CC9:0282 ; Displays "PROPER
; response" msg
7C00:073B 8B86F4FE MOV AX,[BP+FEF4]
7C00:073F 2B46F2 SUB AX,[BP-0E]
7C00:0742 898672FE MOV [BP+FE72],AX
7C00:0746 0346FE ADD AX,[BP-02]
7C00:0749 898676FE MOV [BP+FE76],AX
7C00:074D 0BC0 OR AX,AX
7C00:074F 7D09 JGE 075A
7C00:0751 050C00 ADD AX,000C
7C00:0754 898676FE MOV [BP+FE76],AX
7C00:0758 EB0A JMP 0764
7C00:075A 3D0C00 CMP AX,000C
7C00:075D 7C05 JL 0764
7C00:075F 83AE76FE0C SUB WORD PTR [BP+FE76],+0C
7C00:0764 8B4682 MOV AX,[BP-7E]
7C00:0767 038672FE ADD AX,[BP+FE72]
7C00:076B 898674FE MOV [BP+FE74],AX
7C00:076F 0BC0 OR AX,AX
7C00:0771 7D09 JGE 077C
7C00:0773 050C00 ADD AX,000C
7C00:0776 898674FE MOV [BP+FE74],AX
7C00:077A EB0A JMP 0786
7C00:077C 3D0C00 CMP AX,000C
7C00:077F 7C05 JL 0786
7C00:0781 83AE74FE0C SUB WORD PTR [BP+FE74],+0C
7C00:0786 8BB6F4FE MOV SI,[BP+FEF4]
7C00:078A D1E6 SHL SI,1
7C00:078C 8BB262FF MOV SI,[BP+SI+FF62]
7C00:0790 89B672FE MOV [BP+FE72],SI
7C00:0794 8B8676FE MOV AX,[BP+FE76]
7C00:0798 D1E0 SHL AX,1
7C00:079A D1E0 SHL AX,1
7C00:079C 03F0 ADD SI,AX
7C00:079E D1E6 SHL SI,1
7C00:07A0 8B8292FE MOV AX,[BP+SI+FE92]
7C00:07A4 8986F4FE MOV [BP+FEF4],AX
7C00:07A8 3D2B00 CMP AX,002B
7C00:07AB 7515 JNZ 07C2
7C00:07AD 8BB674FE MOV SI,[BP+FE74]
7C00:07B1 D1E6 SHL SI,1
7C00:07B3 D1E6 SHL SI,1
7C00:07B5 03B672FE ADD SI,[BP+FE72]
7C00:07B9 D1E6 SHL SI,1
7C00:07BB 8B4286 MOV AX,[BP+SI-7A]
7C00:07BE 8986F4FE MOV [BP+FEF4],AX
7C00:07C2 C78684FE7800 MOV WORD PTR [BP+FE84],0078
7C00:07C8 B85100 MOV AX,0051
7C00:07CB 898686FE MOV [BP+FE86],AX
7C00:07CF 898688FE MOV [BP+FE88],AX
7C00:07D3 C7868AFE0900 MOV WORD PTR [BP+FE8A],0009
7C00:07D9 C78678FE7900 MOV WORD PTR [BP+FE78],0079
7C00:07DF C7867AFE5900 MOV WORD PTR [BP+FE7A],0059
7C00:07E5 C7867CFE0000 MOV WORD PTR [BP+FE7C],0000
7C00:07EB 8D86F6FE LEA AX,[BP+FEF6]
7C00:07EF 89867EFE MOV [BP+FE7E],AX
7C00:07F3 8C9680FE MOV [BP+FE80],SS
7C00:07F7 C78682FE0000 MOV WORD PTR [BP+FE82],0000
7C00:07FD FFB62AFF PUSH [BP+FF2A]
7C00:0801 FFB628FF PUSH [BP+FF28]
7C00:0805 8B86F4FE MOV AX,[BP+FEF4]
7C00:0809 053000 ADD AX,0030
7C00:080C 50 PUSH AX
7C00:080D 9A2801FC44 CALL 44FC:0128
7C00:0812 89868EFE MOV [BP+FE8E],AX
7C00:0816 899690FE MOV [BP+FE90],DX
7C00:081A 52 PUSH DX
7C00:081B 50 PUSH AX
7C00:081C 8D8630FF LEA AX,[BP+FF30]
7C00:0820 16 PUSH SS
7C00:0821 50 PUSH AX
7C00:0822 9A9A02FC44 CALL 44FC:029A
7C00:0827 B047 MOV AL,47
7C00:0829 50 PUSH AX
7C00:082A 9A1003443D CALL 3D44:0310
7C00:082F C7868CFE0000 MOV WORD PTR [BP+FE8C],0000
; All the code you just saw. I have no clue what it does
; (hey at least I'm honest) but it wasn't important.
; Here is the imput outer loop
7C00:0835 FF365220 PUSH [2052]
7C00:0839 FF365020 PUSH [2050]
7C00:083D 9A2802FD41 CALL 41FD:0228
7C00:0842 888670FE MOV [BP+FE70],AL
7C00:0846 0AC0 OR AL,AL
7C00:0848 7503 JNZ 084D
7C00:084A E99200 JMP 08DF
7C00:084D 2AE4 SUB AH,AH
7C00:084F 2D0800 SUB AX,0008
7C00:0852 745A JZ 08AE
7C00:0854 48 DEC AX
7C00:0855 48 DEC AX
7C00:0856 7503 JNZ 085B
7C00:0858 E90901 JMP 0964
7C00:085B 2D0300 SUB AX,0003
7C00:085E 7503 JNZ 0863
7C00:0860 E90101 JMP 0964
7C00:0863 8A9E70FE MOV BL,[BP+FE70]
7C00:0867 2AFF SUB BH,BH
7C00:0869 F687790B57 TEST BYTE PTR [BX+0B79],57
7C00:086E 746F JZ 08DF
7C00:0870 F687790B03 TEST BYTE PTR [BX+0B79],03
7C00:0875 740C JZ 0883
7C00:0877 F687790B02 TEST BYTE PTR [BX+0B79],02
7C00:087C 7405 JZ 0883
7C00:087E 80AE70FE20 SUB BYTE PTR [BP+FE70],20
7C00:0883 8A8670FE MOV AL,[BP+FE70]
7C00:0887 C49E7EFE LES BX,[BP+FE7E]
7C00:088B 8BB682FE MOV SI,[BP+FE82]
7C00:088F 26 ES:
7C00:0890 8800 MOV [BX+SI],AL
7C00:0892 FF8682FE INC WORD PTR [BP+FE82]
7C00:0896 FFB688FE PUSH [BP+FE88]
7C00:089A 8D8678FE LEA AX,[BP+FE78]
7C00:089E 50 PUSH AX
7C00:089F 9A56049324 CALL 2493:0456
7C00:08A4 83C404 ADD SP,+04
7C00:08A7 0BC0 OR AX,AX
7C00:08A9 7534 JNZ 08DF
7C00:08AB EB27 JMP 08D4
7C00:08AD 90 NOP
7C00:08AE 83BE82FE00 CMP WORD PTR [BP+FE82],+00
7C00:08B3 7404 JZ 08B9
7C00:08B5 FF8E82FE DEC WORD PTR [BP+FE82]
7C00:08B9 B008 MOV AL,08
7C00:08BB 50 PUSH AX
7C00:08BC 9A1003443D CALL 3D44:0310
7C00:08C1 8D8684FE LEA AX,[BP+FE84]
7C00:08C5 16 PUSH SS
7C00:08C6 50 PUSH AX
7C00:08C7 9A6A00843D CALL 3D84:006A
7C00:08CC B047 MOV AL,47
7C00:08CE 50 PUSH AX
7C00:08CF 9A1003443D CALL 3D44:0310
7C00:08D4 8D8678FE LEA AX,[BP+FE78]
7C00:08D8 16 PUSH SS
7C00:08D9 50 PUSH AX
7C00:08DA 9A8202C93C CALL 3CC9:0282
7C00:08DF 83BE8CFE00 CMP WORD PTR [BP+FE8C],+00
7C00:08E4 7503 JNZ 08E9
7C00:08E6 E94CFF JMP 0835
; Next comes the code that checks your entry. If you follow
; it through you will see it handles not only clearing the
; screen and printing the "GOOD GOING" message but it also
; handles bad entries, etc.
7C00:08E9 8BB682FE MOV SI,[BP+FE82]
7C00:08ED C682F6FE00 MOV BYTE PTR [BP+SI+FEF6],00
7C00:08F2 8DBE30FF LEA DI,[BP+FF30]
7C00:08F6 8DB6F6FE LEA SI,[BP+FEF6]
7C00:08FA 16 PUSH SS
7C00:08FB 07 POP ES
7C00:08FC B9FFFF MOV CX,FFFF
7C00:08FF 33C0 XOR AX,AX
7C00:0901 F2 REPNZ
7C00:0902 AE SCASB
7C00:0903 F7D1 NOT CX
7C00:0905 2BF9 SUB DI,CX
7C00:0907 F3 REPZ
7C00:0908 A6 CMPSB
7C00:0909 7405 JZ 0910
7C00:090B 1BC0 SBB AX,AX
7C00:090D 1DFFFF SBB AX,FFFF
7C00:0910 3D0100 CMP AX,0001
7C00:0913 1BC0 SBB AX,AX
7C00:0915 F7D8 NEG AX
7C00:0917 8986F2FE MOV [BP+FEF2],AX
7C00:091B 0BC0 OR AX,AX
7C00:091D 7509 JNZ 0928
7C00:091F 837E8401 CMP WORD PTR [BP-7C],+01
7C00:0923 7703 JA 0928
7C00:0925 E91C02 JMP 0B44
7C00:0928 0BC0 OR AX,AX
7C00:092A 7506 JNZ 0932
7C00:092C 837E8403 CMP WORD PTR [BP-7C],+03
7C00:0930 740A JZ 093C
7C00:0932 0BC0 OR AX,AX
7C00:0934 745E JZ 0994
7C00:0936 837E8403 CMP WORD PTR [BP-7C],+03
7C00:093A 7358 JNB 0994
7C00:093C B047 MOV AL,47
7C00:093E 50 PUSH AX
7C00:093F 9A1003443D CALL 3D44:0310
7C00:0944 8D867AFF LEA AX,[BP+FF7A]
7C00:0948 16 PUSH SS
7C00:0949 50 PUSH AX
7C00:094A 9A36007E3D CALL 3D7E:0036
7C00:094F 83BEF2FE00 CMP WORD PTR [BP+FEF2],+00
7C00:0954 7518 JNZ 096E
7C00:0956 FF7680 PUSH [BP-80]
7C00:0959 FFB67EFF PUSH [BP+FF7E]
7C00:095D 9A1C04F93C CALL 3CF9:041C
7C00:0962 EB16 JMP 097A
7C00:0964 C7868CFE0100 MOV WORD PTR [BP+FE8C],0001
7C00:096A E972FF JMP 08DF
7C00:096D 90 NOP
7C00:096E FF7680 PUSH [BP-80]
7C00:0971 FFB67EFF PUSH [BP+FF7E]
7C00:0975 9A7204F93C CALL 3CF9:0472
7C00:097A 89867EFF MOV [BP+FF7E],AX
7C00:097E 895680 MOV [BP-80],DX
7C00:0981 B008 MOV AL,08
7C00:0983 50 PUSH AX
7C00:0984 9A1003443D CALL 3D44:0310
7C00:0989 8D867AFF LEA AX,[BP+FF7A]
7C00:098D 16 PUSH SS
7C00:098E 50 PUSH AX
7C00:098F 9A36007E3D CALL 3D7E:0036
7C00:0994 B047 MOV AL,47
7C00:0996 50 PUSH AX
7C00:0997 9A1003443D CALL 3D44:0310
7C00:099C 8D46F6 LEA AX,[BP-0A]
7C00:099F 16 PUSH SS
7C00:09A0 50 PUSH AX
7C00:09A1 9A6A00843D CALL 3D84:006A
7C00:09A6 B008 MOV AL,08
7C00:09A8 50 PUSH AX
7C00:09A9 9A1003443D CALL 3D44:0310
7C00:09AE 8D8684FE LEA AX,[BP+FE84]
7C00:09B2 16 PUSH SS
7C00:09B3 50 PUSH AX
7C00:09B4 9A6A00843D CALL 3D84:006A
7C00:09B9 83BEF2FE00 CMP WORD PTR [BP+FEF2],+00
7C00:09BE 7503 JNZ 09C3
7C00:09C0 E98500 JMP 0A48
7C00:09C3 2AC0 SUB AL,AL
7C00:09C5 50 PUSH AX
7C00:09C6 9A1003443D CALL 3D44:0310
7C00:09CB 8B46F8 MOV AX,[BP-08]
7C00:09CE 050700 ADD AX,0007
7C00:09D1 8946E8 MOV [BP-18],AX
7C00:09D4 FFB62EFF PUSH [BP+FF2E]
7C00:09D8 FFB62CFF PUSH [BP+FF2C]
7C00:09DC 2BC0 SUB AX,AX
7C00:09DE 50 PUSH AX
7C00:09DF 9A2801FC44 CALL 44FC:0128
7C00:09E4 89868EFE MOV [BP+FE8E],AX
7C00:09E8 899690FE MOV [BP+FE90],DX
7C00:09EC C78672FE0000 MOV WORD PTR [BP+FE72],0000
7C00:09F2 EB04 JMP 09F8
7C00:09F4 FF8672FE INC WORD PTR [BP+FE72]
7C00:09F8 83BE72FE05 CMP WORD PTR [BP+FE72],+05
7C00:09FD 7C03 JL 0A02
7C00:09FF E94201 JMP 0B44
7C00:0A02 52 PUSH DX
7C00:0A03 50 PUSH AX
7C00:0A04 9A4602FC44 CALL 44FC:0246
7C00:0A09 8946EC MOV [BP-14],AX
7C00:0A0C 8956EE MOV [BP-12],DX
7C00:0A0F FFB690FE PUSH [BP+FE90]
7C00:0A13 FFB68EFE PUSH [BP+FE8E]
7C00:0A17 9AF201FC44 CALL 44FC:01F2
7C00:0A1C 8946F0 MOV [BP-10],AX
7C00:0A1F 8D46E6 LEA AX,[BP-1A]
7C00:0A22 16 PUSH SS
7C00:0A23 50 PUSH AX
7C00:0A24 9A8202C93C CALL 3CC9:0282
7C00:0A29 8346E80A ADD WORD PTR [BP-18],+0A
7C00:0A2D FFB690FE PUSH [BP+FE90]
7C00:0A31 FFB68EFE PUSH [BP+FE8E]
7C00:0A35 B80100 MOV AX,0001
7C00:0A38 50 PUSH AX
7C00:0A39 9A7E01FC44 CALL 44FC:017E
7C00:0A3E 89868EFE MOV [BP+FE8E],AX
7C00:0A42 899690FE MOV [BP+FE90],DX
7C00:0A46 EBAC JMP 09F4
7C00:0A48 B084 MOV AL,84
7C00:0A4A 50 PUSH AX
7C00:0A4B 9A1003443D CALL 3D44:0310
7C00:0A50 C746E88C00 MOV WORD PTR [BP-18],008C
7C00:0A55 FFB62AFF PUSH [BP+FF2A]
7C00:0A59 FFB628FF PUSH [BP+FF28]
7C00:0A5D B85C00 MOV AX,005C
7C00:0A60 50 PUSH AX
7C00:0A61 9A2801FC44 CALL 44FC:0128
7C00:0A66 89868EFE MOV [BP+FE8E],AX
7C00:0A6A 899690FE MOV [BP+FE90],DX
7C00:0A6E 52 PUSH DX
7C00:0A6F 50 PUSH AX
7C00:0A70 9A4602FC44 CALL 44FC:0246
7C00:0A75 8946EC MOV [BP-14],AX
7C00:0A78 8956EE MOV [BP-12],DX
7C00:0A7B FFB690FE PUSH [BP+FE90]
7C00:0A7F FFB68EFE PUSH [BP+FE8E]
7C00:0A83 9AF201FC44 CALL 44FC:01F2
7C00:0A88 8946F0 MOV [BP-10],AX
7C00:0A8B 8D46E6 LEA AX,[BP-1A]
7C00:0A8E 16 PUSH SS
7C00:0A8F 50 PUSH AX
7C00:0A90 9A8202C93C CALL 3CC9:0282
7C00:0A95 2AC0 SUB AL,AL
7C00:0A97 50 PUSH AX
7C00:0A98 9A1003443D CALL 3D44:0310
7C00:0A9D 8346E80B ADD WORD PTR [BP-18],+0B
7C00:0AA1 FFB690FE PUSH [BP+FE90]
7C00:0AA5 FFB68EFE PUSH [BP+FE8E]
7C00:0AA9 B80100 MOV AX,0001
7C00:0AAC 50 PUSH AX
7C00:0AAD 9A7E01FC44 CALL 44FC:017E
7C00:0AB2 89868EFE MOV [BP+FE8E],AX
7C00:0AB6 899690FE MOV [BP+FE90],DX
7C00:0ABA 52 PUSH DX
7C00:0ABB 50 PUSH AX
7C00:0ABC 9A4602FC44 CALL 44FC:0246
7C00:0AC1 8946EC MOV [BP-14],AX
7C00:0AC4 8956EE MOV [BP-12],DX
7C00:0AC7 FFB690FE PUSH [BP+FE90]
7C00:0ACB FFB68EFE PUSH [BP+FE8E]
7C00:0ACF 9AF201FC44 CALL 44FC:01F2
7C00:0AD4 8946F0 MOV [BP-10],AX
7C00:0AD7 8D46E6 LEA AX,[BP-1A]
7C00:0ADA 16 PUSH SS
7C00:0ADB 50 PUSH AX
; Lot's of code Huh?
7C00:0ADC 9A8202C93C CALL 3CC9:0282
7C00:0AE1 C746E8BC00 MOV WORD PTR [BP-18],00BC
7C00:0AE6 FFB690FE PUSH [BP+FE90]
7C00:0AEA FFB68EFE PUSH [BP+FE8E]
7C00:0AEE B80100 MOV AX,0001
7C00:0AF1 50 PUSH AX
7C00:0AF2 9A7E01FC44 CALL 44FC:017E
7C00:0AF7 89868EFE MOV [BP+FE8E],AX
7C00:0AFB 899690FE MOV [BP+FE90],DX
7C00:0AFF 52 PUSH DX
7C00:0B00 50 PUSH AX
7C00:0B01 9A4602FC44 CALL 44FC:0246
7C00:0B06 8946EC MOV [BP-14],AX
7C00:0B09 8956EE MOV [BP-12],DX
7C00:0B0C FFB690FE PUSH [BP+FE90]
7C00:0B10 FFB68EFE PUSH [BP+FE8E]
7C00:0B14 9AF201FC44 CALL 44FC:01F2
7C00:0B19 8946F0 MOV [BP-10],AX
7C00:0B1C 8D46E6 LEA AX,[BP-1A]
7C00:0B1F 16 PUSH SS
7C00:0B20 50 PUSH AX
7C00:0B21 9A8202C93C CALL 3CC9:0282
7C00:0B26 B80100 MOV AX,0001
7C00:0B29 50 PUSH AX
7C00:0B2A 9AF4019324 CALL 2493:01F4
7C00:0B2F 83C402 ADD SP,+02
7C00:0B32 B047 MOV AL,47
7C00:0B34 50 PUSH AX
7C00:0B35 9A1003443D CALL 3D44:0310
7C00:0B3A 8D46F6 LEA AX,[BP-0A]
7C00:0B3D 16 PUSH SS
7C00:0B3E 50 PUSH AX
7C00:0B3F 9A6A00843D CALL 3D84:006A
7C00:0B44 83BEF2FE00 CMP WORD PTR [BP+FEF2],+00
7C00:0B49 7508 JNZ 0B53
7C00:0B4B FF4E84 DEC WORD PTR [BP-7C]
7C00:0B4E 7403 JZ 0B53
7C00:0B50 E9A7F9 JMP 04FA
7C00:0B53 FF76F4 PUSH [BP-0C]
7C00:0B56 8D867AFF LEA AX,[BP+FF7A]
7C00:0B5A 50 PUSH AX
7C00:0B5B FFB62EFF PUSH [BP+FF2E]
7C00:0B5F FFB62CFF PUSH [BP+FF2C]
7C00:0B63 FFB62AFF PUSH [BP+FF2A]
7C00:0B67 FFB628FF PUSH [BP+FF28]
7C00:0B6B E88EF5 CALL 00FC
7C00:0B6E 8B86F2FE MOV AX,[BP+FEF2]
7C00:0B72 5E POP SI
7C00:0B73 5F POP DI
; Here is the exit code I was talking about
7C00:0B74 8BE5 MOV SP,BP
7C00:0B76 5D POP BP
7C00:0B77 CB RETF
7C00:0B78 B85A06 MOV AX,065A
7C00:0B7B CB RETF
7C00:0B7C B89006 MOV AX,0690
7C00:0B7F CB RETF
Ok, after looking through all of that, can you tell me
where to put the patch. Simple. How about right at the
begining of the doc check right after the music routines (ie
address 7C00:04B6). Hey yeah ... good idea. But how do we
want to patch it. Well, since this is a higher level
language, we just can't use RETF. We must reset the stack.
Since I hate large patches, a simply decided on the
follow patch
7C00:04B6 E9BB06 JMP B74
Ok, by jumping to 0B74, we still get the music but the
actual doc check is not executed. But there is still a
problem. Remember how I said that AX was tested after the
doc check. Well, we still have to fake the check. The
easiest way, is to simply NOP the condition jmp. Here is the
section of code again
45E2:0235 9A46010F4A CALL 7C00:146 ; Call to Doc Check
45E2:023A 83C404 ADD SP,+04
45E2:023D 0BC0 OR AX,AX
45E2:023F 7465 JZ 02A6
If you remember, when you enter the right code, AX will
be set to 0001 when we exit to 45E2:023A. If we OR 0001 and
0001 we get 0001. Here is the binary ...
0000 0000 0000 0001 ( remember OR means
if either is bit
or 0000 0000 0000 0001 is 1 )
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
0000 0000 0000 0001
Clearly we don't want to branch at the JZ at 45E2:023F.
So, to finish the patch we simply NOP that jmp.
Oh boy.. that was hard. So let's test it out. But
first, a little forsight. We will need a unique string of
bytes to search for when making the patch. I say we use the
code from 7C00:04C4 to 7C00:04CE and from 45E2:0235 to
45E2:023F. Yea, write down the hex equivelent and then
restart. Again break in right after the switch to graphics.
Now add the patch (ie A 7C00:04B6 <ENTER>, etc.). Now
execute the program.
SHIT! It worked, we are fucking amazing. Ok, now
adding the patch permenatly. Using PCTOOLS (or whatever)
search the file STARCON.EXE for the bytes mention above
(ie: C746F60B00C746F87900C746FA2801) But wait, now
matches...Hmmm strange. It was there just a minute ago...but
wait there... another file STARCON.OVL (as we all know .OVL
mean OVERLAY). Let's try searching this one.
There we go, that's better (it should should up on the
13 sector read in). Now to add the patch. Simply find the
search bytes and the go backwards until the first occurance
of the hex byte 9A. Add the patch here. Save it.
Next, add the patch to 45E2:023F. Search for the bytes
83C4040BC07465. The should appear on sector 3 (give or take
a few sectors). Now simply change the 2 bytes 74 65 to 90 90
and save the sector. Now, you are good to go.
Well shit, this has been some hell of a textfile. 1113
lines in all. But what detail. Ok I hope you learned
something from all of this. And this end the first part of
CRACKING 101 - the 1990 edition. From here out all lessons (
lesson 5 and up) will be released on their own.
I would like the thank Phantom Phlegm for pushing me to
finish this shit.
Till lesson 5 this is Buckaroo Banzai, signing off.
OH... I can be reached for personal help via E-MAIL on LORD
WOLFEN's CASTLE or TOS...
