Aura.PRG source code unprotected needs recompiling

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rcamp48
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Aura.PRG source code unprotected needs recompiling

Postby rcamp48 » Tue Mar 26, 2019 1:18 am

Here is the fixed Aura.prg file code that I have tried to unprotect, is there someone who would like to re-assemble the program and test it? I get errors when re-assembling even the original program with devpac and turboc. Ayways what I did was I found the instruction lea T13488,a4 for checking the disk, and lea T13463,a0 for starting the program after the copy protection checking was finished, I simply replaced all occurances of lea T13488,a4 with lea H13463,a0. Will that do it or is there more to be done in the program? Russ

AURA.ZIP
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Zippy
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Re: Aura.PRG source code unprotected needs recompiling

Postby Zippy » Tue Mar 26, 2019 7:43 pm

That will definitely not work as whoever did the protection on this knew what they were doing.

There's some bizarre stuff in this like creating the copyright message with a load of random byte moves. It has an encrypted disk protection check, self modifying code + it hides the reference to the protection result by calculating the address rather than accessing it directly. It does seem to be calculating stuff based on the disk reads so I'm not even sure if it's possible to make a 100% crack from this non-working copy.

As well as the initial checks on startup there's some other check that seems to run either on a timer or after a certain thing has been done so many times and would result in the program freezing, I don't know exactly when this is called but I think I've removed it. There's also another call to the encrypted disk protection check sometime later, again I don't know when it's called but I think it's removed now as well.

I've attached a modified Aura.prg for testing... might be 100% cracked OK but considering the effort in the checks I found there could easily be other stuff like checksums or hidden protection that appears later. This version now starts up OK but will need some thorough testing to be sure it's fully working, or not...

Maybe this was already 100% cracked "back in the day" , I didn't collect this Midi stuff so I don't even remember seeing it at all.

AURA.rar
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mlynn1974
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Re: Aura.PRG source code unprotected needs recompiling

Postby mlynn1974 » Tue Mar 26, 2019 11:42 pm

Hi rcamp,
First of all the disassembler you used has written double line spacing so the source code is about 140k bigger than it needs to be. This would have been a problem reassembling it on a real ST back in the day unless you had 2Mb or more installed.

My first attempt:
1. Disassemble with Easy Rider 4,
2. Remove the "This is an unprotected disk" check:

Original:

Code: Select all

      TST.W     L0F76
      BEQ.S     L003D
      LEA       L0BE2,A0
      BSR       L0305
      BRA       L0042
L003D:CLR.W     L0CD1


Modified:

Code: Select all

      BRA       L003D
      NOP
      NOP
      LEA       L0BE2,A0
      BSR       L0305
      BRA       L0042
L003D:CLR.W     L0CD1


I put the NOPs in to keep the code aligned with the original so I can diff it later.

2. Reassemble with Devpac 2.09.
There are some warnings: moveq #$ff,d0 sign extended etc. but it will assemble.

3. Diffing the PRG with the original using Beyond Compare however shows the generated code is different, even before the bit we changed.
The code must be encrypted and Easy Rider 4 gets it wrong.

4. AURAUP.PRG will run but I don't know how to test if the application runs correctly.
As Zippy says there is some bizarre stuff in this program.
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Still got, still working: Atari 4Mb STe, 520STFM, 2.5Mb STF.
Hardware: Cumana CSA 354, Ultimate Ripper, Blitz Turbo, Synchro Express II (US and UK Versions).

rcamp48
Obsessive compulsive Atari behavior
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Re: Aura.PRG source code unprotected needs recompiling

Postby rcamp48 » Wed Mar 27, 2019 4:41 am

Thanks I have more disasembler code if you want it , I have a lot of originals that I have just put onto STX files, also I have a completely cracked Aura disk to compare to the original to see what the MCA did in the day , I will send it to you


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