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The target section described the target as a shorter list of secret files — the intro promised "what changes is how many paths there are", and the per-secret contract pointed at the current-state table's file-shaped columns. That is today's shape with fewer rows, not the target. Rewrite it around the invariant: no secret the store holds is ever written to disk. The mTLS client certificate is the sole credential on disk, and the section now says why — it authenticates the puller to the store, so it is the one credential that cannot be fetched from it. Per secret the target still states minter, reader and renewal, but the reader is now a process pulling a store path at runtime under its own certificate, not a path being read off disk. The current-state section and all of its citations are untouched: the current state genuinely is files, and that contrast is what the page is for.
159 lines
17 KiB
Markdown
159 lines
17 KiB
Markdown
# Credentials: current state, target state, and the rule between the two
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Where [`secrets.md`](secrets.md) is a map of every file a swarm holds, this
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page is the **direction of travel**: what the credential shape is today, what
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it should become, and the test a change has to pass to count as movement
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toward it rather than away.
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It's the thing a discussion should point at. **When the migration
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below is complete, this page supersedes the old credential docs** — `secrets.md`
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gets deleted and this file moves into its place. Until then the two coexist and
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neither is wrong: that one says where a file is, this one says whether it should
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be a file at all.
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Two conventions frame everything below.
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**Where a nix option does carry a secret, it takes a path, never a value.** A
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literal in a nix expression lands in the nix store — world-readable and
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permanent. The target doesn't relax that rule; it removes almost every option
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the rule applies to, because in the target shape there is almost nothing on
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disk for an option to point at.
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**Public material is a value.** A certificate or a public nkey is handed to
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every client that connects, so the store is a fine place for it. Nothing below
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is about those.
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## Current state
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Four credential families live in the swarm's secret store, plus the mTLS
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identity that opens it. That fifth row isn't a stored secret — it's the
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credential that can't be, being what authenticates the reader to the store.
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| store path | kind | minter | writer | reader | renewal | persisted outside the store |
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| -------------------------------------------- | ----------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `swarm/agents/<agent>/matrix/<account>` | one agent's matrix account credential | `swarm-controller`, via a caller-supplied bearer token or its own `m.login.password` (`swarm-controller/src/matrix_account.rs:14-21`) | same unit, `put_matrix_account`'s `store.write` call (`swarm-controller/src/matrix_account.rs:189-197`) | `hive-c0re`'s credential worker, under the **hive's** identity (`hive-c0re/src/workers/credential.rs:33-64`) | `NONE` | **yes** — `hive-priv` writes `<agent-state>/matrix-token`, `0600`, chowned to the agent (`hive-priv/src/main.rs:535-556`) |
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| `swarm/hives/<hive>/matrix/appservice-token` | the appservice token authenticating one hive's homeserver | `swarm-secret-publisher.nix` itself, `head -c 32 /dev/urandom` on the authelia host (`nix/host-modules/swarm-secret-publisher.nix:271-278`) | same unit (`nix/host-modules/swarm-secret-publisher.nix:288-289`) | `swarm-bao-matrix-token.service` on the hive (`nix/host-modules/glue-matrix-bao-token.nix:159-167`) | `NONE` | **yes, twice** — the publisher's own state copy (`nix/host-modules/swarm-secret-publisher.nix:185`) and the hive's token file, `0600` (`nix/host-modules/glue-matrix-bao-token.nix:180-181`) |
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| `swarm/hives/<hive>/queue/agent` | the OIDC client id + secret agent containers present to the swarm queue | authelia, on first boot, into its own client-secret dir | `swarm-secret-publish.service` (`nix/host-modules/swarm-secret-publisher.nix:222-225`) | `swarm-bao-queue-agent.service` on the hive (`nix/host-modules/glue-queue-agent-credential.nix:187-197`) | `NONE` | **yes** — `secret` `0600` and `client_id` `0644` under the hive's agent-credential dir (`nix/host-modules/glue-queue-agent-credential.nix:218-224`) |
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| `swarm/services/<clientId>/oidc/client` | a swarm service's own OIDC client secret, one per service | authelia, on first boot | `swarm-secret-publish.service` (`nix/host-modules/swarm-secret-publisher.nix:245-248`) | whichever host runs that service — `swarm-bao-grafana-oidc.service` (`nix/host-modules/swarm-grafana.nix:565-684`), the collector's twin (`nix/host-modules/swarm-otel.nix:685-767`) | `NONE` | **yes** — Grafana's `0400` host file (`nix/host-modules/swarm-grafana.nix:678-682`), the collector's `0400` file handed in by `LoadCredential` (`nix/host-modules/swarm-otel.nix:764-768`) |
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| _(not stored)_ the store's own mTLS leaves | the certificate a host presents to reach the store at all | `swarm-bao-pki.service`, self-signed, 10-year (`nix/host-modules/glue-bao-tls.nix:114-149`) | n/a | every client reads its own leaf off disk via `BAO_CLIENT_CERT` (`swarm-secret-client/src/client.rs:12-14`) | `NONE` — signed only when absent (`nix/host-modules/glue-bao-tls.nix:128-149`) | **always, by construction** — it has no other form |
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Four things in that table are uncomfortable, and they're the reason this page
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exists rather than a note in the margin of the old one.
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**Every stored secret is persisted as a plaintext file outside the store.** All
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four, without exception. The appservice token is persisted twice: once in the
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publisher's own state directory on the authelia host, and again in the token
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file on the hive that reads it.
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**Nothing rotates.** Every renewal cell reads `NONE`. No rotation path exists
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for any of the four, and none for the mTLS leaves either — those are signed once
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if absent and carry ten years of validity, and deleting the CA to reissue
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invalidates every client certificate already trusting it.
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**No agent container has a store identity at all.** Not one
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`BAO_ADDR` or `BAO_CLIENT_CERT` exists anywhere under `nix/agent-modules/`. An agent
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never talks to the store; the hive host reads on the agent's behalf and writes
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a file into the container. That's the exact inverse of the target below.
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**The appservice token has a second, uncoordinated minter.** `hive-matrix.nix`
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keeps a local first-boot mint as a fallback for an unreachable store. Two
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minters exist for one logical credential, on different hosts, with no agreement
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between them — they can diverge, and the only thing that reconciles them is the
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reader overwriting the local value on its next successful start.
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One half of the target is already real: all four families are minted once and
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read by an identity that logs in with a certificate, with no ambient trust
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anywhere in the path. The cleanest examples are `swarm-bao-queue-agent.service`
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and `swarm-bao-grafana-oidc.service`. What each of them then does is write the
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fetched bytes to disk.
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Two per-agent credential files — the forge token and the github token
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(`hive-priv/src/main.rs`'s `write_forge_token`/`write_github_token`) — are deliberately absent from the table.
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They're operator-supplied and never pass through the store at all, so they're
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not credentials this page governs. Their absence isn't an oversight.
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## Target state
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⚠️ **This section describes the shape the swarm is meant to have — not what
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exists today, and not a claim of movement toward it.** Read the current-state
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table above for what exists. Nothing here is partly done.
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**No secret the store holds is ever written to disk.** That's the invariant,
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and everything else in this section follows from it. A value pulled from the
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store — bao — lives in the memory of the process that asked for it and nowhere
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else: not in a state directory, not in a bind-mounted file, not in a systemd
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credential, not in a rendered config, not for a moment before a unit deletes
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it. The target isn't a shorter list of secret files. It's the store, plus
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exactly one file.
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**That one file is the mTLS client certificate, and it's the only credential on
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disk.** It has to be a file, and the reason is the whole asymmetry: the
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certificate is what authenticates a principal to the store, so it's the one
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credential that can't be fetched from the store. Something has to exist on disk
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before the first request, or there's nothing to make the request with. Every
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host has one, and its only power is to ask the store for the rest. Today only
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the host running the store mints its own leaves automatically — for itself, and
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pre-emptively for a controller and a publisher that might be co-located. For
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every other host, `swarm-bao.nix:529-531` says it outright: this is _"the
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credential an operator places by hand."_
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**The hive hands an agent an identity, never a secret.** An agent container is
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passed an mTLS certificate from its hive and from then on authenticates to the
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store under its own name, pulling what it needs when it needs it. No process
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reads a secret on another principal's behalf: the principal that needs a value
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is the principal that authenticates for it.
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**Per secret, the target specifies minter, reader, and renewal strategy.**
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Those three are the contract, and in this shape the **reader is a process
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pulling a store path at runtime** — not a path on disk, and not a unit whose
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job is to turn a store value into a file.
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| store path | minter | reader — pulls at runtime, holds in memory | renewal |
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| -------------------------------------------- | ------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------ |
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| `swarm/agents/<agent>/matrix/<account>` | `swarm-controller` | the agent container itself, under the certificate its hive passed in | **must be stated** — no strategy is chosen for this credential, and `NONE` isn't one |
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| `swarm/hives/<hive>/matrix/appservice-token` | one minter, on the authelia host | the hive process that presents the token to its homeserver, under the hive's own certificate | **must be stated** — as above |
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| `swarm/hives/<hive>/queue/agent` | authelia | the agent container presenting the OIDC client to the swarm queue, under its own certificate | **must be stated** — as above |
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| `swarm/services/<clientId>/oidc/client` | authelia | the service process that presents the client secret, under the certificate of the host it runs on | **must be stated** — as above |
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| _(not in the store)_ the mTLS client leaf | the store's own PKI, or an operator placing it by hand | its own client, off disk — **the sole exception above**, because it's what makes every other row's pull possible | **must be stated** — as above |
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A renewal cell reading `NONE` is allowed only in the current-state table above,
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as an honest record of where the swarm is. It isn't a strategy, and a new
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secret doesn't get to write it.
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The appservice token's second, uncoordinated minter isn't a row here for a
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reason: in the target each credential has exactly one minter, so a fallback
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mint on the reading host is a thing the target deletes, not a thing it
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describes.
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## Progressive enhancement
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The rule has two halves, and the second is the one that makes the first
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survivable.
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**New functionality matches the target shape immediately.** No legacy clause
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covers code that doesn't exist yet.
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**Existing functionality moves step by step** — each individual step moving
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toward the target shape, never sideways and never away. A step doesn't have to
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finish the migration. It has to not undo it.
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That's checkable, so check it. Apply these to a pull request that touches a
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credential:
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| question | a `yes` means |
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| ----------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |
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| Does it add a minter outside the swarm's existing mint path? | **block** for new functionality. For existing functionality, only if it removes one too. |
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| Does it persist a store-provided secret to disk — a state directory, a bind mount, a rendered config? | **block** for new functionality. For existing functionality, only if the change removes a persisted copy elsewhere and nets out fewer. |
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| Does it add a credential whose renewal strategy is `NONE`? | **block** for new functionality. State the strategy, even if it's "operator reissues and restarts the reader." |
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| Does it read a secret on another principal's behalf and hand it over? | **block** for new functionality. The principal that needs the value authenticates for it. |
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| Does it give a host or container an out-of-band credential that's not the store mTLS leaf? | **block**, both. One out-of-band credential per principal is the whole point of the store. |
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| Does it change the minter, reader, or renewal of an existing credential? | The current-state table above is **stale until updated in the same change.** |
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For existing functionality the questions aren't pass/fail — they're a
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direction check. A change that persists one fewer copy, or moves one reader from
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a host-written file to its own store read, is a step and lands. A change that
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leaves the count the same while moving the file somewhere tidier isn't a step;
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it's churn with a migration story attached.
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When the last `yes` in the current-state table's final column becomes a `no`,
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this page replaces `secrets.md` and the current-state section goes with it.
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