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by mike_hearn 424 days ago
It exists, that's called MPKs.
1 comments
twoodfin 423 days ago
I don’t think MPK’s will fit the need I have. Simply: Run some arbitrary, untrusted, non-sandboxed code in the same thread with assurance it can’t read page X. When that code completes and I’m back in code I trust, X is readable again.

Is that something MPK makes possible? The doc I’ve read suggests either your process can flip permission bits or it can’t. Great for avoiding out-of-sandbox reads. But if there’s arbitrary execution happening, why can’t that code flip the access to secrets back on?

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mike_hearn 423 days ago
Oracle Labs has tech that does that:

https://youtu.be/T05FI93MBI8?si=EieFgujaGiW2gbO8&t=958

The trick is to do a cascading disassembly of all untrusted code you'll execute to prove it can't change the MPK register.

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twoodfin 423 days ago
Wow. Neat trick and exactly the kind of thing I was looking for.

Thanks!

EDIT: Looks like this is the relevant paper from the Graal team: https://www.graalvm.org/resources/articles/binsweep.pdf

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