Decoding CopyLock for Freescape game releases for Amiga/AtariST

[neuromancer]

Hi, I'm a ScummVM developer implementing the freescape engine. Some of these games have releases that included several layers of copy protection, including copylock for some Amiga/AtariST releases of Dark Side, Total Eclipse and Castle Master. We want to offer instructions for owners of these games to dump their disks and extract the executables. ScummVM will take care of the rest of the protections, since we already reimplemented them. I recently found that disk-utilities allow to read/convert the copylock track from disk images, and you even include a copylock utility to emulate/disassembly the protection, however, it seems it does not save the decrypted executable. I'm wondering how much effort will be to do it, and if there is any way to help.

[keirf]

Are we talking about a Copylock-protected Amiga exe which gets decrypted at load time? It should be pretty easy. I've not looked at such a Copylock before but it may be as simple as remembering where segments were loaded in this loop https://github.com/keirf/disk-utilities/blob/master/m68k/copylock.c#L117 and then saving out those segments at the end of the Copylock emulation.

Tell me IPF(s) or whatever to take a look at, and I can see what I can do.

[neuromancer]

Hi,

Are we talking about a Copylock-protected Amiga exe which gets decrypted at load time?

Yes.

Tell me IPF(s) or whatever to take a look at, and I can see what I can do.

There is a copylocked ipf in archive.org here. The executable file that is copylocked is called 0.drk (you can check it in the header). It will decrypt itself using copylock and then load the other file 1.drk and decrypt it using some code that we already reimplemented, so we only need to get a clean version 0.drk.

Thanks in advance!

[keirf]

Here is the linked Dark Side disk, converted to ADF, and with the cracked 0.drk file inserted. If what you want is a process by which users can create their own cracked 0.drk file, then that is more involved.

darkside_cracked.zip

[neuromancer]

Coming back to this, the specific files needed for Castle Master / The Crypt are cmstr.com and crypt.com. They are supposed to be Amiga executables. Additionally, there is Space Station Oblivion, which was the alternative name for Driller in the US. The ipf seems to be protected somehow, but I'm not sure if it is CopyLock or something else. Can you take a look? (if it is necessary to open another discussion for that, let me know and I will do it).

[keirf]

I don't think cmstr.com and crypt.com are straightforward executables. Actually I suspect they are stripped and encrypted. Again, you just need data tables out of these, actually?

Space Station Oblivion has looks like a straightforward long track. I doubt it's Rob Northen. Probably something simpler. It may not even involve encryption.

Someone pointed me at the following tool for Atari ST Copylocks and other protections: https://github.com/orionfuzion/dec0de
It may help!

[neuromancer]

Regarding cmstr.com and crypt.com: I need the full binaries, since the data is actually mixed with the code. However, the code is actually not needed. If it is there, that's fine. But there is no need to have a functional executable. If you check the decrypted binaries, you should be able to see the full list of strings used in the games (as well as other things). For example:

***************
 PRESS ANY KEY 
  OVERPOWERED  
 YOU COLLAPSE  
    CRUSHED    
  FATAL FALL   
 YOU DID IT !  

Regarding:

Space Station Oblivion has looks like a straightforward long track. I doubt it's Rob Northen. Probably something simpler. It may not even involve encryption.

Do you know how is the long track used? (at least, a hint?)

Oh, btw, dec0de works great for AtariST CopyLock protections, at least for Dark Side and Total Eclipse. I haven't tested with Castle Master for AtariST yet. I have documented all the steps for for the Freescape games here: https://wiki.scummvm.org/index.php?title=Freescape/DRM

[neuromancer]

I just found that this suggests that Castle Master for AtariST is using some kind of Copylock. 🤔

[neuromancer]

Quick update: got a message in the ScummVM FB and confirmed that dec0de works correctly on Castle Master for AtariST using M.PRG (however, there is another layer of compression/decryption so I need to keep digging in order to recover the original data..)