Settled in the operator's own words: nodes should not own passwords, only an
identity when communicating to the broker. Recorded that way at the top of the
record, because it is the whole decision in one line and the rest is why.
What this obliges, in order of newness: enrolment is the one mechanism that does
not exist. Per-node broker users, virtual hosts and per-queue permissions are
broker configuration. Mutual authority is certificates on a connection already
open. And the boundary must fail legibly, which is the requirement the debugging
objection earned.
Written first as though the link were a thing to build. It is not. ADR 0001
already has it — every node connects outbound to a single broker, nothing ever
connects to a node, each node declaring an exchange named for itself and
consuming from its own queue. Already outbound-only, already per-node addressed,
already the one channel everything arrives through.
So this record is not proposing a channel. It proposes that the channel carry
per-node identity instead of one shared credential. The same as-is records the
fault it fixes, for the broker rather than the database: the broker's credential
is mesh-wide, rotating it is a mesh-wide operation, and doing it wrong has taken
the broker down.
That reframes the overhead objection, which was fair against what the record
said and not against what it means. Of six properties, four are already true,
one is broker configuration — users, vhosts and per-queue permissions the broker
already implements — and exactly one is new machinery: enrolment. Meanwhile 0037
subtracts, since a node under it holds no database credential at all. Three
hand-carried shared secrets become one identity that grants only identity.
Adds the option that was actually being weighed and was missing: accept the
exposure as the cost of simplicity. Rejected because the simplicity IS the
unfixability — the credential cannot be rotated precisely because everything
holds the same one.
And adds a requirement from the debugging objection, which was the strongest
part of it: it must fail legibly. A boundary that refuses a node without saying
why is worse than the password it replaced, because a wrong password at least
announces itself. That is §5 applied to a security mechanism.
0038 accepted: no two modes. One behaviour, two sources of declaration.
0039 fills the gap 0038 named. Proposed rather than measured — it designs a
boundary that does not exist — but what it replaces IS measured, and that is the
argument.
Today adopt.sh asks the operator to paste in the postgres password and the
object store password, the same ones on every node, and they are not discarded
after adoption: wireguard and traefik open a pg connection on every reconcile.
So every node permanently holds a credential to the control plane's database,
and 00-as-is/06 records that nothing rotates it. Compromise of any node is
compromise of the mesh's store, with no way back.
Four properties make the link a boundary rather than a pipe: it is outbound and
node-initiated, so a node has no listening control surface — which the topology
already requires, since most nodes have no forwarded port. A node holds its own
identity and nothing else, so compromise of a node is compromise of that node.
Authority is mutual, because a host that applies whatever the link delivers must
know the mesh from something impersonating it. And what may be pushed is bounded
by FORM — declarations of known shape, never a command to run.
That last property is stated with its limit rather than oversold: it bounds
form, not impact. A compromised control plane can declare harmful state and the
host will apply it faithfully. What it buys is a describable blast radius.
Joining uses a one-time short-lived enrolment token, useless once used and
useless after a while, in place of hand-carried shared secrets.
Named rather than hidden: the first node's identity is self-issued and becomes
the root of trust, which is the one place 0038's "no special first node" does
not fully hold. Rotation becomes possible and is still not designed. And what
may expire is constrained by 0036 — an identity needing refresh would make a
laptop fail for being a laptop.
jschoubben