hashlink VS seL4

What's missing is a way to pin web apps so that you always get the previous version (and can opt in to subsequent versions after checking their hash from a trusted source).

There is a clever way of doing this, using a bookmarklet, a dataURI, and SRI, but the UX isn't great.[0] If something like Hashlinks[1] were supported by browsers, though, this could work quite nicely.

[0] https://news.ycombinator.com/item?id=17776456

[1] https://w3c-ccg.github.io/hashlink/

> What about websites though?

It is possible for a web page to specify the expected hash of a script file, which the browser will enforce. This is called SRI (Subresource Integrity).[0]

Of course that still leaves the bootstrapping problem of how the page itself can be guaranteed to have a specific hash, but fortunately there is a clever hack that can be done with bookmarklets[1], or the page can just be saved and loaded/served locally.

While that works technically, the UX isn't great because the address bar won't show the domain of the remote server (although browsers seem to be hiding the address bar from the user more and more). A better solution would be for browsers to support Hashlinks[2], which would allow a bookmark to point to a remote page with fixed contents.

[0] https://developer.mozilla.org/en-US/docs/Web/Security/Subres...

[1] https://news.ycombinator.com/item?id=17776456

[2] https://github.com/w3c-ccg/hashlink

> People like to snob Unix but the fact is: the world runs on Unix.

The world you are aware of runs on it.

> Can we really do that much better or is it just hubris?

Yes. Have a look at seL4[1] and Barrelfish too[2], even though that's no longer active. seL4 in particular is powering a lot of highly secure computing systems. There is a surprisingly large sphere outside of Unix/POSIX.

[1] https://sel4.systems/

[2] https://barrelfish.org/

There are also RTOS-capable microkernels such as seL4[0], with few but extremely fast syscalls[1]. Note times are in cycles, not usec.

0. https://sel4.systems/

1. https://sel4.systems/About/Performance/

https://sel4.systems

Working on a number of platforms, verified on some. Multicore support is an ongoing effort afaict.

On OS built on this kernel is still subject to some assumptions (like, hardware working correctly, bootloader doing its job, etc). But mostly those assumptions are less of a problem / easier to prove than the properties of a complex software system.

As I understand it, guarantees that seL4 does provide, go well beyond anything else currently out there.

Take a look at this: https://sel4.systems/

It's probably have to be seL4 (https://sel4.systems), running on some fully OSS hardware.

There are question marks over much of available RISC-V chips due to chinese producers, so maybe OpenPower based hardware?

Plus, the entire system (motherboard, etc) would need to be manufactured using a good supply chain.

Hmmm, this has probably all been thought through in depth before by others. :)

You can use it to (mostly) validate small snippets are the same. See Alive2 for the application of Z3/formalization of programs as SMT for that [1]. As far as I'm aware there are some problems scaling up to arbitrarily sized programs due to a lack of formalization in higher level languages in addition to computational constraints. With a lot of time and effort it can be done though [2].

1. https://github.com/AliveToolkit/alive2

2. https://sel4.systems/

Formal methods. This is not in most general-purpose programming languages and probably never will be (maybe we'll see formal methods to verify unsafe code in Rust...) because it's a ton of boilerplate (you have to help the compiler type-check your code) and also extremely complicated. However, formal methods is very important for proving code secure, such as sel4 (microkernel formally verified to not have bugs or be exploitable) which has just received the ACM Software Systems Award 3 days ago.

Today we'd look at seL4.