The responder loads the issuer and callout-user seeds from the secret
store under its own role, beside the xkey, and no longer takes
--issuer-seed-file / --user-seed-file.
`ensure-xkey` becomes `ensure-callout-keys`: it ensures the xkey as before,
and for each nkey creates the seed create-only when the store holds none,
from --import-{issuer,user}-seed-file when that file is present, so a key
kept on disk keeps its public half. Once a read of the store returns a seed,
the import file is removed; when that seed differs from the file the
store's is kept and a warning names the file. The public halves are
published create-only at swarm/public/swarm-nats/callout-{issuer,user}.
The KeyStore trait and its test double move to `keystore` so both key
modules share them.
Every nats-server this module starts renders `auth_callout.xkey` or does
not start, and the responder serves only that server, in the same
container and generation. A request without `Nats-Server-Xkey` therefore
comes from no supported server, so the plaintext framing is gone: such a
request is logged at warn and gets no reply, and the server that sent it
times out the connect as a denial. A signed denial would have had to go
out unsealed, which is the path this removes.
Also scopes two claims to what is true: the xkey's public half is read by
the swarm-nats-auth policy only, and the metadata-delete gap in the
replace-key procedure is about the two xkey paths, not all of
`secret/metadata/`.
Writing bao's `default` policy needed a new stanza in the granter's own
policy, which only the bootstrap token can upload, so deploying it took
a manual root-token step. Nothing needed it: the one reader of the
callout xkey's public half is `swarm-bao-nats-callout-xkey`, which logs
in as the `swarm-nats-auth` role, and that role's policy already names
the path. `swarm-bao-nats-auth-policy` writes that policy as the granter
on every deploy, under the granter's existing `sys/policies/acl/swarm-*`
grant.
Removed: the `swarm-bao-public-read-policy` unit, its marker block, the
granter's `sys/policies/acl/default` stanza, the granter-role restart of
that unit, the bao.md section and the module-eval cases pinning them.
When nats-server has an auth_callout xkey it seals each request to that
key and names its own public xkey in the Nats-Server-Xkey header. The
responder now loads the callout xkey seed from the secret store before
it connects, opens a sealed request with it, and seals its reply (grant
or deny) back to the header's key. A request with no header is answered
in plaintext, as before.
A new `ensure-xkey` verb creates the pair when the store holds no seed:
the seed at swarm/services/swarm-nats/callout/xkey-seed, the public half
at swarm/public/swarm-nats/callout-xkey. Each write is a create-only
(cas=0) write, and a run whose create fails reads the stored value back,
so two concurrent runs end up with one key. The responder itself only
reads the seed and refuses to start without it.
swarm-secret-client gains SecretStore::create, the cas=0 write.
