> The safe execution of any untrusted Turing complete code is a pipe dream.
I don't think that's true. It's not turing completeness that's the real problem here. It's that software usually has access to accurate timing information, whether it's via RDTSC, gettimeofday(), or sharing memory with another thread that does things that take a predictable amount of time. If a program has no notion of current time and cannot measure how long something takes, then a lot of those side channel attacks no longer work. (Note that this precludes using styles of threading that have nondeterministic results, but it doesn't preclude using styles of threading that are deterministic, like Haskell's parMap.)
I do think maybe we should move away from the model of "let's let people run programs comprised of arbitrary instructions on their computers, and build all our security around keeping programs from reading and writing things they shouldn't" to a model of "all programs running on this computer were compiled by a trusted compiler, and our security is based on the compiler disallowing certain unsafe constructs". This is sort of analogous to web browsers running javascript in a sandbox, or running eBPF in the Linux kernel.
I don't think that's true. It's not turing completeness that's the real problem here. It's that software usually has access to accurate timing information, whether it's via RDTSC, gettimeofday(), or sharing memory with another thread that does things that take a predictable amount of time. If a program has no notion of current time and cannot measure how long something takes, then a lot of those side channel attacks no longer work. (Note that this precludes using styles of threading that have nondeterministic results, but it doesn't preclude using styles of threading that are deterministic, like Haskell's parMap.)
I do think maybe we should move away from the model of "let's let people run programs comprised of arbitrary instructions on their computers, and build all our security around keeping programs from reading and writing things they shouldn't" to a model of "all programs running on this computer were compiled by a trusted compiler, and our security is based on the compiler disallowing certain unsafe constructs". This is sort of analogous to web browsers running javascript in a sandbox, or running eBPF in the Linux kernel.