dckcandClaude Opus 5.5
2820c015ee
A vat's globalOutbound is now always null. A granted host arrives as env.egress, an Egress the app can hand to whichever of its parts should have it; as globalOutbound it was ambient to every module in the vat. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
47 lines
3.2 KiB
Markdown
47 lines
3.2 KiB
Markdown
# toybox
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Vats whose code is installed at runtime: each vat is a Durable Object whose app runs as a [facet](https://developers.cloudflare.com/dynamic-workers/usage/durable-object-facets/) on code loaded through workerd's Worker Loader. Think `vatAdmin.createVat(bundle)`, with a supervisor per vat.
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- [supervisor.js](supervisor.js): `Vat` stores code by SHA-256 and runs the app on it; `Public` and `Admin` are the two entrypoints; `Egress` is a grant of one host.
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- [switchboard.js](switchboard.js): a separate workerd process, the vats' only way out: a forward proxy for HTTP and WebSockets.
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- [config.capnp](config.capnp): the sockets have no addresses; whoever starts workerd hands them in, so holding a socket is the authority it grants.
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| socket | reaches | what its holder can do |
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|---|---|---|
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| `http` | `Public` | `GET /<vat>/…`: talk to a vat's app |
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| `admin` | `Admin` | `PUT /<vat>` with an ES module body: install it and (re)start the app; its storage carries over. `?egress=<host>` grants the app that one host. |
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An app must export `class App extends DurableObject` (see [apps/](apps/)). Its global `fetch` always throws: nothing in a vat is ambient. A granted host arrives as `env.egress`, an `Egress` with the host in `ctx.props`: its `fetch` forwards matching requests, WebSocket upgrades included, to the switchboard and refuses the rest with a 403. It is an object, so the app can pass it to whichever of its parts should have it.
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toybox reaches the switchboard over a unix socket (`-e switchboard=unix:…`), in HTTP proxy style so the full URL, scheme included, survives the hop.
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## Run it
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```sh
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pnpm install
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pnpm test # real workerds: install, upgrade, isolation, egress grants, fetch and WebSocket out, crash and restart
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pnpm switchboard # systemd-socket-activate on ./switchboard.sock
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pnpm start # likewise on 127.0.0.1:8787 and ./admin.sock; state in ./state
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```
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Then, in a third terminal:
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```sh
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curl -X PUT --unix-socket admin.sock --data-binary @apps/counter-v1.js http://toybox/alice
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curl localhost:8787/alice # v1 count 1
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curl -X PUT --unix-socket admin.sock --data-binary @apps/counter-v2.js http://toybox/alice
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curl localhost:8787/alice # v2 count 2
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curl -X PUT --unix-socket admin.sock --data-binary @apps/egress-probe.js 'http://toybox/erin?egress=example.com'
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curl 'localhost:8787/erin?url=https://example.com/' # got: <!doctype html>…
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curl 'localhost:8787/erin?url=https://example.org/' # got: egress to example.org not granted
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```
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## Under systemd
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[systemd/](systemd/) has socket and service pairs for toybox and its switchboard, assuming this directory is installed at `/opt/toybox`. toybox gets no network of its own (`PrivateNetwork=yes`): only the two sockets it is handed and the switchboard's socket, which only members of the `toybox` group can open. The switchboard has the network, fenced by `IPAddressDeny=`; `switchboard.capnp` allows `local` addresses only so the tests can reach a local echo server.
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Neither unit has been run under the system manager yet.
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`PrivateNetwork=` needs the system manager; as a `systemd-run --user` unit, systemd logs "lack privileges for network namespace, proceeding without".
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