Measured against a running server built from this module's own rendered
config, not a hand-written one -- which is the fix to the method as much
as to the file. Two shapes died in a row: a bare name authenticates
anyone who sends it, and a name plus an nkey refuses to start at all
(nkey users do not take usernames or passwords).
A malformed key is fail-closed too, so the only way to a live server
here is a real key whose seed nobody but the responder holds.
argus caught it and reproduced it: a users entry carrying only a name
has no credential, so CONNECT {"user":"auth"} is accepted with no
password. The name is a literal in this module, so on the shared netns
that identity was walk-in-able from every agent container -- the same
hole the module exists to close, moved rather than closed.
An nkey rather than a password: only the public half appears in config,
the seed reaches the responder alone, so a hive with no responder has
nobody who can authenticate as it. Asserted at eval, because the
rendered config is valid and the server starts either way.
A swarm has one message queue; this is the container that runs it, in
the same shape as every other swarm service. Off by default, and off
means absent.
The auth_callout block is the interim state and the final one at once.
Measured on the pinned nats-server rather than reasoned about: an empty
authorization block, and one with an empty users list, both accept an
anonymous client and answer PONG. auth_callout sets auth_required and
refuses everyone until a responder approves them, so a config whose
responder does not exist yet denies by default -- and the responder
lands beside it without any of this being swapped out.
That matters more here than it would elsewhere because the container
shares the host netns, so an unauthenticated interim state would be
reachable from every agent container on the hive.
No package option, deliberately: nixpkgs' nats module resolves
pkgs.nats-server itself and exposes none, so one here would name
something it cannot control.
No gateway vhost either: NATS speaks its own TCP protocol, nginx cannot
front it, and cross-hive reach is the wireguard mesh.
