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hyperhive/swarm-secret-client
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Filename Latest commit message Latest commit date
atlas 6170e74a31 swarm-bao: agent certificates issued by a store-generated agent CA
An agent's store identity was signed in swarm-controller's memory by a CA
a controller-host unit generated on disk, and the listener never trusted
that CA. Agent leaves now come from the store itself: a `pki-agents` PKI
mount whose root openbao generates internally, so the agent CA's key
never exists outside the store.

- swarm-bao-agent-pki (new, store host, as the bao granter): enables and
  tunes the mount, generates the root once (guarded on an empty issuer
  list, no replace branch), upserts the `swarm-agent` role (client
  certificates named `hive-agent-*` only, 90 days), caches the CA at
  /var/lib/swarm-bao-tls/agent-ca.pem and composes the listener bundle.
- The listener's tls_client_ca_file is a new listener-client-ca.pem
  (client-ca.pem, then the agent CA). Host cert-auth roles still pin
  client-ca.pem, so an agent leaf satisfies no host role. swarm-bao-certs
  composes the same bundle before openbao starts.
- openbao reads tls_client_ca_file only at start, so when the bundle
  changed after openbao started, swarm-bao-agent-pki restarts
  openbao.service in the container; under `seal = "shamir"` it prints
  the step instead. Once swarm-bao-certs has a cached CA, later boots
  start openbao with it and do not restart.
- The controller policy gains exactly `update` on
  pki-agents/issue/swarm-agent. mint_and_verify now asks that role for
  the leaf (the store generates the key), writes the agent's cert-auth
  role pinning the issuing CA bao returned, and writes the agent's
  policy as render_agent alone: the hive-shared queue credential stanza
  is gone.
- deploy.bao.agentPkiRoleName (must start `swarm-`, asserted with the
  other pki role names); swarm-controller gets
  SWARM_CONTROLLER_AGENT_PKI_MOUNT/_ROLE from the deploy.bao options.

Deleted: swarm-controller-agent-ca and its options (agentCaFile,
agentCaKeyFile), env, LoadCredential entries and assertion;
agent_identity's Authority, rcgen signing and validity window; the
rcgen and time dependencies of swarm-controller (rcgen leaves the
workspace); policy::render_agent_with_queue and its tests. The CN-prefix
assertion policy.rs said was owed is not: agent and host roles pin
different CAs.

Migration is re-creating each agent after deploy; that overwrites the
stale role and policy.

Closes #4756
2026-09-27 22:59:27 +02:00
..
src swarm-bao: agent certificates issued by a store-generated agent CA 2026-09-27 22:59:27 +02:00
Cargo.toml swarm-secret-client: derive Kind's segment strings via strum instead of a hand-written match 2026-09-12 00:06:31 +02:00
README.md swarm-secret-client: one module per kind of secret, not one struct 2026-09-08 15:53:50 +02:00

swarm-secret-client

Reading and writing a swarm credential in the secret store, over vaultrs. The HTTP is that crate's job. What this one owns is the agreements both ends of the store have to state identically: where a credential lives, which field its bytes are in, and how this deployment's environment becomes a logged-in client.

The surrounding picture — which secret is minted where, and why delivery is a copy rather than a bind mount — is docs/swarm/secrets.md.

Why a crate and not a module per binary

The store has two Rust ends and they are peers: the swarm controller writes a credential, a hive reads it. Neither is senior to the other, so a path formatted at each call site is an agreement with no owner — it holds right up until one side is edited alone, and then it fails as a missing key rather than as a mismatch.

The third end is what settles it. nix/host-modules/glue-matrix-bao-token.nix reads the store with bao kv get -field=value. That reader is a shell line in a nix module: it cannot be renamed by the same refactor as a Rust struct, and no Rust test reaches it. So the field name is pinned by a test against the serialised literal rather than left to the struct definition.

The identity is a certificate, and the role is the hive's name

Authentication is the store's cert auth method. nix/host-modules/glue-bao-tls.nix mints the client certificate with its CN set to the hive's name, because a cert-auth role matches on the CN. So cert_role is not a free choice for the caller: a hive passes its own name, and the policy attached to that role is what scopes what it may read.

The listener's tls_require_and_verify_client_cert is a different thing and not a substitute. It decides who may open a connection; it says nothing about who the connection belongs to, and a store with the option set and no cert mount configured refuses every login made here. That refusal is what Error::Vault out of connect means.

Configuration

Settings::from_env reads BAO_ADDR, BAO_CLIENT_CERT, BAO_CLIENT_KEY, and the optional BAO_CACERT.

The BAO_ spellings are read explicitly rather than left to vaultrs. Its own defaults look for VAULT_ADDR / VAULT_CLIENT_CERT / VAULT_CLIENT_KEY, which no unit in this tree sets. Falling through to them builds a client with no identity at all, and that surfaces as a TLS handshake failure — a place that names neither the variable nor the reason.

Empty is as absent as unset. systemd renders an unset nix option as Environment=BAO_CACERT=, so empty is the shape a missing value arrives in.

The certificate and key are paths, not values, and are read at connect time — same rule as every other credential in this tree, for the same reason: a value in a nix expression is rendered into the world-readable store.

Reading the environment is separate from connecting (Settings::from_lookup) because every one of those failures is a misconfiguration an operator has to read an error about, and none of them needs a reachable store to happen.

Names that arrive from elsewhere

matrix::account_path is fallible, which for a string formatter needs saying: its segments are an agent name from the topology and an account name from that agent's own config. A / turns one agent's segment into another agent's directory and .. walks out of the prefix entirely, so the charset it accepts is deliberately narrower than what the store would.

One module per kind of secret

client moves whatever type a caller names; it decodes nothing itself. What a stored object holds is stated in the module that also builds its path — matrix today, and a second kind of swarm secret gets a module beside it.

The split is deliberate. A single shared struct that grows one field per consumer ends up carrying, on every path, a field only one path's reader has ever heard of; and the two things a kind of secret must pin — where it lives and what is in it — are one agreement that reads worse split across modules.

What this crate does not do

It has no opinion on what a caller may read. That is the policy attached to the cert role, and it lives in the store.

It holds the token minted at login and renews nothing. A handle is built per credential, so the login is the cheap part of a rare operation — a caller that wanted to keep one alive across a token's lifetime would need more than this.