[Diggsey]

> Imagine a programming language runtime whose runtime state (i.e. lexical scope) is partially broadcast over network as it happens, kind of like a remote debugger.

This sounds absolutely terrifying from a security perspective...

What's to stop a malicious client from broadcasting code that deletes my entire database?

[outworlder]

> runtime state

> code

Some overlap, but these are essentially two different things.

> What's to stop a malicious client from broadcasting code that deletes my entire database?

Your backend.

[Diggsey]

Deleting a database is probably a bad example, but my point still stands: even if you are not trasferring code back and forth, runtime state is enough to be a problem.

What if your runtime state includes an `is_authorized` flag or similar? How do you guarantee that this state remains server-side when the entire language conflates server/client side code?

For this to work, there needs to be language-level support for distinguishing untrusted inputs from trusted ones, or else it's a recipe for disaster.

[weavejester]

If the compiler is separating server-side code from client-side code, then it's also separating out symbol bindings as well. So it knows where symbols are bound, and where they are referenced, and it can use this to limit information flow.

For example:

    (client
      (let [token (get-client-token)]
        (server
          (let [username (get-username db token)]
            (client
              (dom/p "Hello " username))))))

The compiler can infer that token is defined on the client, then sent to the server, which in turn defines username and sends that back to the client.

It's the same system you'd use in normal server/client architecture, just inlined.

[chitowneats]

Compile-time macros do indeed seem to be what provides the necessary client/server separation for sensitive data.

That does mean you are trusting the library to implement these macros correctly. In that sense, data security for these symbol bindings is a responsibility of the library, and therefore a risk, as is called out lower on the page.

Once the library is complete however, and a larger part of the community has been able to inspect it, this type of bug should not be an issue. It's one of the most fundamental concerns of the library.

[BillyTheKing]

any sort of networking sounds terrifying from a security perspective...

Unfortunately (or fortunately) it's also a corner-stone of computing in general