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0 pointsnknight14y ago0 comments

It's 128KB of RAM, that's the same as the original Macintosh in 1984. I would be surprised if it ran at more than about 10MHz. And nevermind the constrained resources for implementing any of this hypothetical infrastructure, unless Notch adds an MMU, you can't enforce permissions

You can't think about this in modern terms. It's not a modern computer. It's a 1980s computer, and it's supposed to run a spaceship. Think microcontrollers, not smartphones or set-top boxes.

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coderdude14y ago

Couldn't the permission system exist outside of the constraints of the in-game computer (as just some game mechanism)? If each of the ship's discrete components were accessible at some address, couldn't the game enforce the permissions at a level above the simulated CPU?

A rough static analysis of the code might reveal where those components are accessed, and as long as you enforce permissions while the software runs then you should be able to catch anything that tries to slip past.

DanBC14y ago

Someone could write an out-of-game emulator[1] which people could use to test software.

[1] I have no idea what the correct terminology is here.

nknightOP14y ago

Go back and look at the first post in this very thread. Notch explicitly intends nothing of the kind, and I certainly can't see why it would be done -- it runs counter to the vision thus far articulated.

coderdude14y ago

I know he said that. I'm following the conversation. I'm just describing an idea for a permission system.

javert14y ago

It should be possible to provide programs as "data" that is interpreted by the program "running" on Notch's CPU, thus allowing a fine-grained, whitelisted permissions even without MMU. No?

ricree14y ago

Depends on how it's structured, doesn't it? It's entirely possible that programs and data will share the same memory with no sandboxing between programs. In that case, then without some sort of MMU a virus could just inject code into an otherwise benign program.

Even with finer program access controls, it would still be hard to protect as long as untrusted code was allowed to alter trusted.

javert14y ago

You don't understand what I'm proposing. If you want to put it in terms of sandboxing, what I am proposing is a sandbox.

jiggy201114y ago

You would have to abstract the CPU in some way and then write the permissions management in software as part of the interpreter. Bear in mind that this is already only a 16bit CPU with a restricted address space.

javert14y ago

You would have to abstract the CPU in some way and then write the permissions management in software as part of the interpreter.

Yes, that's what I said. :)

Bear in mind that this is already only a 16bit CPU with a restricted address space.

I suspect the interpreter could be made to fit, with limited space left for the untrusted (to-be-interpreted) code. As has been pointed out elsewhere, though, if there is a backing store (i.e., simulated hard drive), it's probably possible to have effectively unlimited "RAM" in the game in practice, unless Notch implements a slowdown for accessing the backing store.

jiggy201114y ago

True, but your CPU is limited too so having to lex & parse sourcefiles and walk syntax trees to run programs could be a bottleneck there, if you remember old computers there was a significant performance gap between native and interpreted code.

In practice that might not matter for many applications if they do not have to use intensive algorithms etc.

I would still imagine that compilers would be used more than interpreters though which would mean that some security would need to be present at the "hardware" or "firmware" level.

Another interesting thing to think about regards backing stores:

I assume that the programs will be able to take input from the world around them, i.e other ships , objects in space etc.

So what's to stop you from using (perhaps) a tractor beam to re-organise the position of asteroids in space and then "read" that data back using ship instrumentation?

Potentially the entire universe becomes one big DB!

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coderdude14y ago

DanBC14y ago

Someone could write an out-of-game emulator[1] which people could use to test software.

[1] I have no idea what the correct terminology is here.

nknightOP14y ago

coderdude14y ago

I know he said that. I'm following the conversation. I'm just describing an idea for a permission system.

javert14y ago

It should be possible to provide programs as "data" that is interpreted by the program "running" on Notch's CPU, thus allowing a fine-grained, whitelisted permissions even without MMU. No?

ricree14y ago

Even with finer program access controls, it would still be hard to protect as long as untrusted code was allowed to alter trusted.

javert14y ago

You don't understand what I'm proposing. If you want to put it in terms of sandboxing, what I am proposing is a sandbox.

jiggy201114y ago

javert14y ago

You would have to abstract the CPU in some way and then write the permissions management in software as part of the interpreter.

Yes, that's what I said. :)

Bear in mind that this is already only a 16bit CPU with a restricted address space.

jiggy201114y ago

In practice that might not matter for many applications if they do not have to use intensive algorithms etc.

I would still imagine that compilers would be used more than interpreters though which would mean that some security would need to be present at the "hardware" or "firmware" level.

Another interesting thing to think about regards backing stores:

I assume that the programs will be able to take input from the world around them, i.e other ships , objects in space etc.

So what's to stop you from using (perhaps) a tractor beam to re-organise the position of asteroids in space and then "read" that data back using ship instrumentation?

Potentially the entire universe becomes one big DB!

1 more reply

j / k navigate · click thread line to collapse