b2c1378fd3
Fixes the Microsoft.Contractions/write-good.ThereIs/alex.Condescending/ Microsoft.Auto errors vale flagged in CI (prose-lint-errors, required): contractions throughout, no sentences opening with 'There is', dropped the 'auto-mints' hyphenation and the 'easily' condescension flag, and renamed the credentials table's 'what it is' header to 'kind' (also flagged once styles were resynced). No technical claim or file:line citation changed. Same fix applied to the one new line in docs/README.md's pointer to this page.
137 lines
14 KiB
Markdown
137 lines
14 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's on track to 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 carry over unchanged, because the target doesn't relax them.
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**A secret is a path, never a value.** Every option carrying key material or a
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token takes a file path, because a literal in a nix expression lands in the nix
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store — world-readable and permanent. That rule survives the migration; what
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changes is how many paths there are.
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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 what the swarm is moving toward — not what exists
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today.** Read the current-state table above for that. In particular, the first
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line below is the one most often misread as a statement of fact, so it's
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stated as a target twice.
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**Every host needs a store mTLS certificate. Everything else is done through
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the store.** That's the target. Today only the host running the store itself
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mints its own leaves automatically — for itself, and pre-emptively for a controller and a
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publisher that might be co-located. For every other host, `swarm-bao.nix:529-531`
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says it outright: this is _"the credential an operator places by hand."_ No
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automated issuance path exists for an ordinary hive. The target is one
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out-of-band credential per host and zero out-of-band credentials anywhere else;
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the current state is one out-of-band credential per host **plus** every file in
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the last column of the table above.
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**Agent containers get an mTLS certificate passed in from the hive, and pull
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their secrets themselves.** The hive's job becomes handing the agent an
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identity, not handing it secrets. Today no agent has an identity of any kind
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and every agent secret arrives as a file the host wrote.
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**No store-provided secret is persisted.** A value read from the store lives in
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the memory of the process that needs it and nowhere else — not in a state
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directory, not in a bind-mounted file, not in a systemd credential. Today every
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one of the four is persisted, and one of them twice.
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**Per secret, the docs specify minter, reader, and renewal strategy.** Those
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three columns are the contract. A secret whose renewal strategy is `NONE` is
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allowed to exist only as an honest record of where the swarm is — it's not a
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strategy, and a new secret doesn't get to write it.
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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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