Found while reasoning about issue 127's replay question, in code committed earlier
today. The controller's permissions granted no inbox at all, so the answer to
every enrolment on the mesh would have been refused — "Permissions Violation for
Publish to _INBOX.enrol.anchor…" — while the controller logged that it had
enrolled the node.
**`allow_responses` does not cover it, and that is the trap.** It permits one reply
to the reply subject of a message the user received, and a message a JetStream
consumer delivers has had that field claimed for the consumer's own ack address
(design 25 §2). The address the controller actually answers is the one the request
carried in its *payload*, which the server does not recognise as a reply subject at
all. The two mechanisms look interchangeable and are not.
**My earlier verification could not have caught this.** The live enrolment tests run
against a server with no accounts and no permissions, so they exercise the subjects
and the round trip and nothing about authority. Composing the real configuration and
running a server on it is what found it.
Granted the enrolment inbox space and nothing wider: nothing but an enrolling node
ever subscribes under that prefix, each scoped to its own token's, so the controller
publishing there is the mesh answering enrolments and reaches nothing else. Confirmed
against the permissioned server both ways — the answer arrives, and a node's own
inbox is still refused.
Pinned as a rule that needs no server: whatever an enrolling node subscribes, the
controller must be able to publish to, and a node's, a module's and a person's inbox
must stay out of reach. That check is a subject-pattern match rather than a string
compare, so a grant that widened by a wildcard would not slip past it.
It also bears on 127's open question about who replays a build announcement: an
answer to a *module's* inbox would need `_INBOX.>`, which is exactly the blanket
grant design 25 §4 refuses. So the catch-up cannot become an inbox reply.
Design 25 §6 says an enrolling node subscribes the inbox its own token derives.
It had none: `sub` was empty, so a node would publish its request and wait out
its timeout against a mesh that had answered — the handshake could not have
completed.
And there was one shared `enrolment` user, which cannot carry that inbox at all:
a permission belongs to a user, so an inbox per token means a user per token.
Named after the node, which **is** the token's id — a token is issued for a node
record, the mesh holds one live claim per record, and the node's name is the one
identifier both sides have before anything else is agreed. It is also exactly
what the other transport does, where the account is named after the node and the
secret is its password.
A nameless enrolment user is now refused rather than composed into
`_INBOX.enrol..>`: an empty subject token, and worse, one every nameless
enrolment user would share — which is one machine able to read the credentials
sealed to another.
Still to wire: something that composes one of these per live token. Nothing
composes enrolment users yet, on either bus — on the old one the account is made
imperatively through the broker's management API when a token is issued, and
here there is no management API, so issuing a token has to recompose the server's
configuration. That is the remaining half of enrolment on the new bus.
Design 25 §7. A person is not a module and holds no seat: nothing is
addressed to them, nothing is delivered to them, and they have no durable
consumer. What they have is permission to ask, as a list of tools or `*`
for an administrator.
Four properties the tests hold it to, each of which is a way of being
wrong that would not announce itself: a person reaches nothing but tools,
so one cannot claim a module said something; no ack subject, because
authority over a consumer that does not exist is authority nobody would
audit; no allow_responses, because a person who can answer a request is
impersonating a module on a bus where anyone may serve a tool; and two
people do not share an inbox.
Task 1.4. The foundation set only — a seat's streams come at registration
and a module's consumers at assignment, neither of which has happened at
genesis (ADR 0118).
Asserted rather than created: a stream that was deleted, or a mesh raised
from a backup, must converge rather than run without the guarantee its
messages assume.
Two things the definitions have to get right, both tested:
- CONTROL names its subjects instead of taking mesh.control.>, because
heartbeats live under that prefix and a stream of them competes for
retention with the messages that matter
- EVENTS filters on the event token, which is why that token exists; a
filter over a module's whole namespace would persist every tool call
Overlapping filters are refused where the set is written: NATS accepts two
streams matching one subject and stores the message twice under two
retentions, which nothing reports.
Adds nats.go as a dependency; it pulled golang.org/x/* forward. Full suite
green.
Task 1.3 of novox/hq ADR 0116. On AMQP an account was an HTTP call; on NATS
it is text the controller composes and the server reloads (ADR 0106). Pure,
so the mesh's whole authority model is testable as strings.
NATS closes a gap management.go recorded rather than hid: LavinMQ has no
topic permissions, so an emitter was granted the events exchange whole and
ADR 0042's origin reservation was "stamped by the sdk, not enforced here".
Per-subject permissions make it the server's refusal.
Two things found by composing a real file rather than reading the design:
- a scoped inbox leaves a responder unable to reply, because the answer goes
to the caller's inbox. allow_responses is the answer — one reply to the
subject of a message actually received — and only principals that serve
are granted it. Recorded in design 25 §4.
- composition must be deterministic: the module's entrypoint reloads on the
file's digest, so an order-dependent composer would reload the whole bus
on every controller restart. Covered by a test.
The golden fixture is the exact text `nats-server -t` accepts, so the syntax
is the server's rather than one we invented.
jschoubben