Subj : Re: Doorgame cracking
To   : esc
From : Bugz
Date : Tue Jan 31 2023 11:57 am

-=> esc wrote to All <=-

 es> Hey friends, has anyone cracked a 16bit DOS doorgame?

You mean there exists people that haven't? Those POOR SOULS. :P

 es> I'd like to begin learning how to do this to crack old games and IGMs
 es> and things of that nature, but haven't done this type of work before. I
 es> have a linux computer and am using dosemu2 for my doors. I seemingly
 es> have the 'sourcer' program working but haven't actually done any
 es> cracking before so I would love to find someone to show me the ropes,
 es> if that person exists :)

It really depends on the door. Some doors are packed (upx/pklite), but
can be unpacked with utilities. Some won't run when unpacked (they check.) 
Other doors are distributed as unregistered, you only get a registered 
version if the author recompiles it and sends it to you. (There's nothing 
there to crack.) Some use overlays, so the program can be larger and
tricker to debug.

There's some written in qbasic that I haven't been able to figure out. 
(Because of the way it interfaces to the qbasic runtime via int calls.)
It's tokenized and interpreted...

Sourcer is ok, but gets lost too easily. (No, this really is code. No, this
really is data.) IDA (Interactive DisAssembler) is fantastic (for cold 
disassembly).

My goto tool is TD (Turbo Debugger) in dosbox.

There's nothing like viewing the live code running right there, right now.
(Ah, my old friends AX, BX, and etc...)

As my time permits, I'll see what I can come up with.

Take care,
bugz

.... It really WAS my evil twin.
=== MultiMail/Linux v0.52
--- SBBSecho 3.14-Linux
 * Origin: Red-Green BBS - bbs.red-green.com (0:0/0)

.