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Quote:
Original post by WitchLord

Maybe it is possible to have the VM analyze the bytecode when loading it to see what operations it is doing and then decide if it is trying to access anything it shouldn't. It should be possible to verify if any absolute addresses are being read from or written to. And the instructions that pushes the address of a stack location on the stack (for future manipulation) can be checked so that the location is within the stack frame of the function. In this pass I can also verify that all function ids are valid, and global variable indices as well.


I think this is what I've been trying to suggest. :)

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I suppose you did [wink] I just didn't see a viable solution until now.

It's still not an easy task but at least I believe I will be able to do it so that it has the same security as script code. I will also have to change how object properties are accessed as the byte code ADDOFF (add offset) alters a pointer in a way that can't be controlled. I've already come up with a solution for it so it's not a show stopper, though it will affect performance slightly.

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So I have read all the posts and this is my point of view :

- You want to send byte code over IP
- You cannot trust client side because some bad guys wants to do what they have to do, bad work, neither you can trust server because bad guys wants to also do their bad work.

The question is :
Why all of those bad guys wants to crash your application ?

If your a client, you don't have really interest in crashing your computer, don't you ?

If your a server you can have interest in crashing your server ? no I don't think so too, but, you can have interest in crash the clients connecting to you ! To do this, your server must be knowed by client ...

So, my point of view wont be to secure scripts, but rather secure your application outside the script part.

Both client and server must trust each other, so, they have to aknowledge each other :
Client : Hello server, my program is version X, with a checksum of Y and I run with ScriptVersion Z. What is your versionS ?
Server : Hello client, you are connecting server version X, with checksum of Y and I run ScriptVersion Z.

Now that client and server knows their versions, checksum, or whatever they want to check (graphic card abilities, processor, memory, etc...) they can trust each other.

Also, timestamping and versionning the messages between client and server can lead to disconnection when timeout comes (bad guy debbuging !).

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Well, if you must send a script over the line to a client, the smartest option would be to sign the script with a DSA. This will allow the client to verify that the script hasn't been tampered with (on the trip from the server to the client). This isn't foolproof however, and using a CA will help to increase the security of the DSA, but none the less, it is one option.

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Quote:
Original post by Washu
Well, if you must send a script over the line to a client, the smartest option would be to sign the script with a DSA. This will allow the client to verify that the script hasn't been tampered with (on the trip from the server to the client). This isn't foolproof however, and using a CA will help to increase the security of the DSA, but none the less, it is one option.


That still doesn't help if the server actually sends bad stuff.

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