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The table still described the raft data as living at /var/lib/swarm-bao on the host, bind-mounted in -- the design the previous commit removes. An operator following that row would back up a directory that no longer holds the store, and would not know that a container destroy now takes the data with it. States what is still host-level, since that is the part the row was actually useful for: the TLS material and the PKCS11 token, both of which a host unit writes and the container only reads.
182 lines
12 KiB
Markdown
182 lines
12 KiB
Markdown
# Swarm secrets: what exists, and where each one lives
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A swarm's credentials are generated in three different places and read in a
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fourth, so "where does this file go" has a different answer per deployment.
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This page is that answer, one row per secret.
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Two rules run through all of it.
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**Private key material and access tokens are paths, never values.** Every option
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carrying one takes a file path (`*File`), because a literal written into a nix
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expression is rendered into the nix store — world-readable and permanent. No
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option in this tree accepts one inline, and adding one would be a leak rather
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than a convenience.
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The rule is about what must stay secret, not about credentials generally.
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**Public material is a value**: a certificate, or a public nkey like
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`swarm.nats.calloutUserPublicKey`, is published to every client that connects,
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so the store is a perfectly good place for it.
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**The generator and the reader are usually in different containers.** They share
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the host's network namespace, which makes them feel co-located, but their
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filesystem roots are separate. That is why delivery is a **host-side copy rather
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than a bind mount**: `nixos-container` refuses to start when a bind source is
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missing, and a secret minted on another container's first boot does not exist
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yet. Binding it would make one container wait on a file that waits on a
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container that starts after it.
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## Topologies, by who places secrets
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Every row below is read against one of these. This is a different cut
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from the [deployment shapes](services.md#deployment-shapes) --- those
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say *where services run*, these say *who is responsible for a secret
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file being there* --- so the two lists do not line up one-to-one, and
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neither is a renaming of the other.
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| topology | what it means | who places secrets |
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| **all-local** | one host runs the swarm's shared services and its own hive | nobody — each secret is generated where it is read, or copied by a host unit |
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| **swarm-managed** | the swarm's services run on a host with `swarmctl` | `swarmctl` writes what it owns; the rest is still generated in place |
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| **hive elsewhere** | a hive that federates with a swarm it does not host | the operator provides the file and names it in config |
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## Swarm-level — one of each per swarm
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| secret | generated by | lives at | hive elsewhere |
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| swarm root CA cert | `swarm-ca.nix` first-boot unit, when `autoConfigure` is set | `/var/lib/swarm-ca/root.pem` | operator copies the **cert** in; it is public |
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| swarm root CA key | same unit | `/var/lib/swarm-ca/root-key.pem`, `0600` | stays on whichever host holds it — see the constraint below |
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| swarm-services sub-CA (cert + key) | `swarm-ca.nix`, signed by the root | `/var/lib/swarm-ca/services-ca{,-key}.pem` | issued where the root lives |
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| authelia session, JWT and storage-encryption keys | authelia's first-boot unit, in-container | `/var/lib/authelia-swarm/{session,jwt,storage-encryption}.key` | generated in place; nothing outside that container reads them |
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| authelia OIDC HMAC key | same unit | `/var/lib/authelia-swarm/oidc-hmac.key` | same |
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| authelia OIDC issuer key (RSA) | same unit | `/var/lib/authelia-swarm/oidc-issuer.key` | same — relying parties verify against the **public** half at `/jwks.json` |
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| OIDC client secret, plaintext half | `authelia crypto hash generate --random` | `/var/lib/authelia-swarm/oidc-clients/<id>.secret` | operator provides the file and names it in whichever option reads it — `sso.clientSecretFile` for a service, `otel.clientSecretFile` for the hive's telemetry collector |
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| OIDC client secret, digest half | the same mint | `oidc-clients/<id>.digest` | authelia's own half; merged at runtime via `settingsFiles` |
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| the swarm collector's copy of its OIDC secret | `swarm-otel-oidc-secret.service` copies it from authelia's tree | `/var/lib/swarm-otel-oidc/<id>.secret` inside the `swarm-otel` container | n/a — this collector runs on the swarm's service host, beside authelia |
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| authelia subject store | `swarmctl` and `swarm-authelia-bridge` | `users.yml` — one file, read and written by both | `swarmctl`, on the host that runs authelia |
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| wireguard private key | **the operator** — `wg genkey` | whatever `swarm.wireguard.privateKeyFile` names | always operator-provided; nothing generates this for you |
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| queue auth-callout nkeys (user seed + account seed) | `swarm-nats-callout-keys` first-boot unit, when `nats.autoGenerateCallout` is set | `/var/lib/swarm-nats-callout/{callout-user,issuer}.seed`, `0600` | operator mints both with `nk` and names them in `nats.calloutUserSeedFile` / `nats.calloutIssuerSeedFile` |
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| the secret store's own contents | openbao, on first `bao operator init` — **an operator action, not a unit** | inside the `swarm-bao` container, at its own `/var/lib/openbao`, kept across rebuilds by `ephemeral = false`. ⚠️ **Not a host path**: `nixos-container destroy swarm-bao` takes the raft data with it, so back up the container's tree, not `/var/lib/`. Only the store's TLS material (`/var/lib/swarm-bao-tls`) and its PKCS11 token (`/var/lib/swarm-bao-token`) are host-level | n/a — there is one store; a hive elsewhere is a *client* of it and holds none of this |
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| the secret store's unseal material | the HSM/TPM under `deploy.bao.seal = "pkcs11"`; openbao itself under `"shamir"` | in the token; or held by whoever ran `bao operator init`, which is what `"shamir"` means and why it is stated rather than inferred | n/a — only the host running the store seals anything |
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The three keys authelia mints for itself are generated in-container precisely
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because nothing outside that container ever reads them. **That is the test worth
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applying to any secret added here** — and the client secret's plaintext half is
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the one row that fails it, which is the entire reason a delivery step exists.
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There are two telemetry collectors and they land on opposite sides of that test.
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The **hive's** collector needs no delivery step. It authenticates to the swarm's
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collector as its own hive, and it is a host unit rather than a container, so on
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an all-local swarm it reads authelia's file where it lies and no second copy is
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made. On any other topology it is an ordinary "operator provides the file"
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case — see `services.hyperhive.otel.clientSecretFile`.
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The **swarm's** collector does need one. It runs in a container, so its copy is
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placed by `swarm-otel-oidc-secret.service` and lands at
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`/var/lib/swarm-otel-oidc/<client-id>.secret` — the same shape as the forge and
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homeserver rows below, and for the same reason: the container that mints the
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secret is not the container that reads it.
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There is no operator-provided variant of that one, and that is a property of
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where it runs rather than an omission: the swarm's collector lives on the host
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that runs the swarm's services, which is the host that runs authelia. The copy
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is only made when authelia is enabled here and something published is being
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scraped; otherwise no secret is needed and none is placed.
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### Minting the queue's callout nkeys
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`nats.autoGenerateCallout` mints both keypairs on the host before the queue
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starts. It is on by default only under `singleHostSwarm` — the one
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topology where the queue, its responder and the operator are the same person. On
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every other topology, mint them yourself:
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```
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nk -gen user > callout-user.seed # the responder's own identity
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nk -gen account > issuer.seed # signs the user JWTs it hands out
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nk -inkey callout-user.seed -pubout # → calloutUserPublicKey
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nk -inkey issuer.seed -pubout # → calloutIssuerPublicKey
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```
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Keep both seeds at `0600` and name them in `calloutUserSeedFile` /
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`calloutIssuerSeedFile`. Possession of the **issuer** seed is the authority to
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admit anyone to the queue, so it belongs wherever the responder runs and nowhere
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else.
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A hive that sets neither the public keys nor `autoGenerateCallout` fails at
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eval, naming the option it wants. That is deliberate: a queue that started
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without them would accept `CONNECT {"user":"auth"}` from anyone sharing the
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host's network namespace, and nothing would look wrong until somebody connected.
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**All four or none** — the seed paths are required too, not just the public
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keys. They are two halves of the same pair: the server verifies with the public
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half, the responder signs with the private one. Supplying only the public keys
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used to pass eval and leave the queue with an auth-callout nobody answers, which
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refuses every client rather than degrading — and a refusal reaches the client as
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a timeout, so the symptom is every consumer hanging with nothing logged.
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One consequence of the generated path worth knowing before you debug it: with
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`autoGenerateCallout` set, the queue's config is assembled at boot rather than at
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build time, so a malformed one surfaces when the container starts instead of
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when the system builds. The server names the offending file and refuses to run.
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## Hive-level — one of each per hive
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| secret | generated by | lives at |
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| hive CA cert + key | `hive-tls.nix` first-boot unit | `<deploy.hive-controller.tls.stateDir>/ca.pem`, `ca-key.pem` (`0600`) |
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| hive leaf certs | `hive-tls.nix`, signed by the hive CA | `<deploy.hive-controller.tls.stateDir>/<name>.pem` |
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| matrix registration token | a host activation script, on first boot | `/var/lib/hyperhive/matrix-register-token` (`0600`) |
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| the forge's copy of its OIDC secret | `hive-forge-oidc-secret.service` copies it from authelia's tree | `/var/lib/forgejo-oidc/<id>.secret` inside the forge container |
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| the homeserver's copy of its OIDC secret | `hive-matrix-oidc-secret.service`, same shape | `/var/lib/tuwunel-oidc/<id>.secret`, handed to tuwunel through `LoadCredential` |
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Both delivery units wait for authelia's first boot to mint the secret — a
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bounded wait, 120s — and then **fail loudly** rather than skipping. A silent skip
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produces a service whose login button always fails, which is a symptom several
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layers from its cause.
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The store's **first reader** is the matrix registration token, and it is worth
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saying why that one: it is an opaque 32-byte value with no second file and no
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format. Authelia's OIDC secret needs a `.secret` *and* a matching `.digest`, so
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starting there would have meant debugging "can a reader authenticate and get
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bytes back" and "did we write authelia's file format right" at once, with an
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SSO outage as the failure mode.
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`glue-matrix-bao-token.nix` fetches it and writes the file `hive-matrix.nix`
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already reads, so the homeserver never learns the store exists. Every failure
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path — no such key, sealed store, unreachable store, empty value — leaves the
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locally minted token in place, so a hive with no store behaves exactly as it
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did before.
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⚠️ **Service↔store mTLS is its own trust domain.** A credential you must
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already hold to authenticate cannot be fetched from the thing it authenticates
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you to, so the store's identity cannot come from an authority the store
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distributes — which excludes the hive CA and the swarm CA both, and has nothing
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to do with the gateway's HTTPS certificates either way. `glue-bao-tls.nix`
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mints a CA that signs exactly two things, the store's server certificate and a
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reader's client certificate, and distributes nothing. A deployment with a real
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internal CA deletes that file and names its own paths in
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`deploy.bao.serverCertFile` / `clientCaFile`; the store itself has no opinion.
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## The constraint that decides where the root lives
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A hive CA carries `nameConstraints=permitted;DNS:<hive domain>`, and **a swarm
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service name is a sibling of the hive domain rather than a child** — `forge.<swarm>`
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next to `<hive>.<swarm>`. So a hive CA cannot issue a certificate for a swarm
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service. Not by policy: by construction, and openssl enforces it.
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Whatever holds the swarm root is therefore what makes swarm-service certificates
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possible at all. Two things follow:
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- **The root's private key is a runtime file and must never enter the nix
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store**, so nothing build-time can name it — `security.pki.certificateFiles` is
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read when the system is built, and is the wrong tool here. Trust reaches
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containers through a bind-mounted bundle assembled at boot instead.
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- **On any topology other than all-local, placing that key is an operations
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decision**, not something this module tree makes for you. A hive that hosts no
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swarm services needs only the root's *cert*, to trust what others issue.
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## Adding a secret
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State three things, in the row you add above: **who mints it**, **which
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container reads it**, and **what happens when they differ**. If they differ, it
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needs a delivery unit, and the unit copies — it does not bind.
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