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This does not detract from this post being a good, fun, and interesting read, but for anyone that is puzzled why “Turing complete” should imply “insecure”: It doesn’t.
So Turing completeness implies recursive Turing completeness. It is the theoretical threshold at which a device is capable of reproduction, a sort Schwarzschild radius for complex, heritable behavior, aka life.
Stuck in an appendix is a fascinating mini-essay, "How many computers are in your computer?" https://www.gwern.net/Turing-complete#how-many-computers-are...
My research/tinkering so far is https://github.com/moreati/pickle-fuzz
> This matters because, if one is clever, it provides an escape hatch from system which is small, predictable, controllable, and secure, to one which could do anything . It’s hard enough to make a program do what it’s supposed to do without giving anyone in the world the ability to insert another program into your program, which can then interfere with or take over its host I take issue with the statement that TC mea…
In many cases it is the final step.
If you're trying to secure something that lacks any good reason to access the internet, it shouldn't be able to. And yet so many things like that still have internet access.
This creates a problem when you have a program which is only supposed to process some sensitive data and not export it off to the attacker, because as soon as the attacker can execute their own code, the process already had access to the sensitive data and to the internet. Or there is no sensitive data but the process already had access to the internet, so now the attacker is using your hardware to mine cryptocurrency or route their network traffic through your IP address.
We could stop giving network access to processes that otherwise shouldn't need it, but that requires overcoming the incumbent economic forces that use network access for telemetry and advertising. So there are a lot of people hoping that making things that aren't Turing-complete is easy. But it turns out to be pretty hard. So we may have to start pushing back against those economic forces.
Basically, if I wanted to provide someone with a Turing complete language, what’s the simplest/easiest thing I could provide, that would still be useful?
"...mov, which copies data between the CPU & RAM, can be used to implement a transport-triggered-architecture one instruction set computer, allowing for playing Doom..."
Click on "Doom" link and read:
"The mov-only DOOM renders approximately one frame every 7 hours, so playing this version requires somewhat increased patience."
A related idea that I’m interested in but find a bit hard to articulate is to describe “simple” Turing complete languages, where simplicity is defined more by ease of reasoning for a human than by any objective metric. Basically, if I wanted to provide someone with a Turing complete language, what’s the simplest/easiest thing I could provide, that would still be useful?
Simplifying, to have a TC programming language you need two things: RAM and the ability to decide your next state based on the memory contents.
Earlier quoted context omitted.
I do research in this space professionally. The answer is not always, but sometimes: discovering unintended states or transitions in the execution contract of a program is a common building block for exploits. However, proving that the execution contract of a program can be coerced into representing computations in a TC language doesn't necessarily prove that you can do anything interesting. Complex formats like PDF…
Just a heads up: I think the second post has a typo; the code has named "new_item" but is referred to as "item" throughout. (I'm also not sure I understand the safety added by dynamic_cast.)