The mesh writes its own user list, and at genesis there is no mesh yet to write it. So
the installer carries the first one — the controller's own account at a well-known
bootstrap password, exactly as the store is reached at `postgres:bootstrap` and the old
bus at `guest:guest`, and rotated with them. From the controller's first composition
onward the file is the controller's.
That left a gap I would not have found by reading: the controller's own account is
created before there is a controller to mint one, so nothing recorded a hash for it, and
its first composition would have left the writer out of the file it was writing — a bus
nothing can connect to, produced by the thing connected to it. It now records a hash of
the credential it is actually using, and only if none is recorded, so a restart cannot
put the bootstrap password back over a rotated one.
The carried list and the derived one are two statements of one fact, so a test compares
them: every subject the controller derives must be in the template, and nothing wider.
It earned itself immediately — the composer was granting both a role's whole event
branch and the one event it actually follows, which is a wider way of saying the same
thing, and the wider one wins. Only the submitting half of a role is granted now; what
comes back is named exactly.
Getting this wrong is the worst kind of silent. A controller whose carried permissions
are narrower than the ones it derives comes up, connects, and is refused on the first
thing it tries, with an authorisation error naming a subject and not the template that
forgot it — and a mesh cannot be raised twice to find out.
Two pieces the composer has been waiting for since it was written.
**The credential has to outlive its own minting.** On the bus the mesh runs on
today an account is a management call: mint a password, hand it over, seal the
plaintext to whoever will use it, keep nothing — which works because the broker
remembers. Here the users are one file, rewritten whenever any of it changes, so
keeping nothing would mean the first person's access change silently blanking
every module's password. So a bus user's bcrypt hash is now recorded, keyed by the
username the file needs, and the plaintext comes back exactly once. Verified
against a real store that the hash verifies the password it was made from, that
the password itself is not in there, that minting again rotates rather than adds,
and that forgetting a node takes its host's and its modules' credentials with it.
**Permissions are not stored, and that is the point.** Only the credential is
kept. Authority is derived from what each module declares, every time the file is
written (ADR 0043) — a stored permission list would be a second account of a
user's authority, able to disagree with the records it came from, and both would
look internally consistent while they did.
`Users` derives the list: the controller always first and always present, one
user per node, one per module per node, one per live token, one per person. Two
users with one name is refused where both can be named, rather than left to be
whichever one the server happened to read. A user the mesh has never minted a
password for is *named* rather than dropped or written as a user anybody is:
that is an ordinary situation with an obvious remedy, and the caller decides
whether a partial file is worth writing.
What remains of 1.7: delivering the file to the node that runs the server, and
minting at enrolment and assignment — which is transport-coupled, because a node
on the old bus must not be handed a credential for the new one.
jschoubben