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Looking for a reverse engineer

Junior Spellweaver
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Nov 21, 2006
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Hello. I am trying to fix a GunBound Game Server. I have it working 99% except by a problem with 1 specific packet of the game.

I was able to fix it 50% (it works most of times) but sometimes its still give me a Access Violation when copying the packet data to memory.

More information about the game:
http://forum.ragezone.com/f493/gunbound-season-2-v6-72-a-1193005/

Contact me if you want yo know more about this.

Thank you
 
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My guess what item id and shop packet information you are sending isnt get valided. The client only crashes when your checksum from server to client is incorrect. Could be bad header to bad info. Check the total size and use ida pro to back track to the violation. You will see where the buffer overflow is. Inside the case will be the checksum and opcode break point on it and keep filtering it out on that packet header.
 
Junior Spellweaver
Joined
Nov 21, 2006
Messages
137
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38
Simply keep the 50% that is working and just delete the 50% that is not working. Multiply your result by the remaining 1% that is not working. This will bring it up to 100% working guaranteed. This is an easy fix. Not rocket science.

As I said, I think I have 99% working. Hows the math for that? xD



My guess what item id and shop packet information you are sending isnt get valided. The client only crashes when your checksum from server to client is incorrect. Could be bad header to bad info. Check the total size and use ida pro to back track to the violation. You will see where the buffer overflow is. Inside the case will be the checksum and opcode break point on it and keep filtering it out on that packet header.

I appreciate your reply but I think I dont have enought knowledgement to accomplish that process. But I will totally keep in mind your guess. Also: What you mean by "item id" and "shop packet" if the problem occurs on SVC_ROOM_JOOIN (0x2111)? Do you mean that the items and avatar information of users inside of room are validated? I first found out that the packet lacked 5 bytes. Then I added them and now I have a checksum validation error. I tried to recalculate de packet checksum using the same formula the game server uses but no sucess.

There is another problem: The crash is not happening every time since I added that 5 bytes ON MY PC. But its happening 100% times on other computers. On my computer it is not crashing often.

I currently use IDA to read, but I dont really understand much. I was able to hook and simulate some useful game functions. But about the checksum, things are really confusing for me..
 
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