f892dc6a19
The hive's bao policy grants read on swarm/agents/* and swarm/hives/<hive>/* only. Five comments across four modules still listed swarm/services/* among its reads, or said a shared leaf would let a unit fetch another service's OIDC client secret, or that the hive's leaf reads every secret in the store. Comment and option-description text only.
280 lines
14 KiB
Nix
280 lines
14 KiB
Nix
# Glue: this hive's agent queue credential comes out of the secret store.
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#
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# A cert login that fails LOUDLY because every state it fails on is one a
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# retry fixes, then a read that degrades QUIETLY because no retry turns "no
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# value there" into a value.
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#
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# ⚠️ Two files, not one, and that is the consumer's shape rather than a
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# preference. `swarm-logs` inside the agent reads the secret and the client id
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# each from its own file (`<prefix>_OIDC_CLIENT_SECRET_FILE`,
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# `<prefix>_OIDC_CLIENT_ID_FILE`), so splitting them here is what lets
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# hive-c0re hand both to an agent without parsing anything.
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#
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# ⚠️ An ABSENT file means this hive's agents do not connect to the queue, and
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# that is correct rather than degraded. The publisher runs on the authelia
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# host and authelia mints on its first boot, so "nothing at that path yet" is
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# the ordinary early state of a swarm. Nothing here writes a local stand-in:
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# there is no such thing as a locally valid OIDC client secret, so a placeholder would turn a hive that cannot connect
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# into one that is refused, which reaches the agent as a timeout.
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#
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# 📌 This runs wherever a client identity is configured, NOT only where the
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# store is. `deploy.bao.enable` would have been the co-location assumption
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# itself; the reader needs a certificate, not a neighbour. On the store's own
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# host ./glue-bao-tls.nix supplies one as a `mkDefault`; elsewhere an operator
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# places the leaf and names it, and the same unit works. It also needs this
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# host to run a hive (`deploy.hive-controller.enable`): the credential is for
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# the agents hive-c0re creates here at runtime, and the unit writes under
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# hive-c0re's own state directory.
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{
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pkgs,
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lib,
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config,
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...
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}:
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let
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hyperhiveCfg = config.services.hyperhive;
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deployCfg = hyperhiveCfg.deploy;
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baoCfg = hyperhiveCfg.swarm.bao;
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baoDeploy = deployCfg.bao;
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# What decides whether this unit exists at all. A reader is defined by holding
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# a certificate the store accepts, and that is true on the store's own host
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# and on a hive three networks away for exactly the same reason.
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#
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# 🩸 This principal's OWN leaf, not `clientCertFile` — the hive's. Bao
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# matches a cert-auth role on the CN, so one leaf shared by four readers
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# would be ONE principal holding the union of four grants: read on
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# `swarm/agents/*` AND `swarm/hives/<hive>/*`, when this unit reads one
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# queue credential and nothing else. Its own leaf carries
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# `<queueAgentCommonNamePrefix>-<hive>` and its role grants the single path
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# below — still this hive's own, so the narrowing costs no reach.
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haveClientIdentity =
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baoDeploy.queueAgentClientCertFile != null && baoDeploy.queueAgentClientKeyFile != null;
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# Does this host read the store at all — the hive's own leaf, which is the
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# one thing a remote-store deployment has to place by hand. Only used to
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# decide whether a missing per-principal leaf is a mistake or a deployment
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# that has no store: a host holding neither is the supported no-store
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# shape, and one holding this pair but not the pair above reads the store
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# without a reader identity of its own.
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hiveReaderIdentity = baoDeploy.clientCertFile != null && baoDeploy.clientKeyFile != null;
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credentialDir = toString deployCfg.hive-controller.queue.agentCredentialDir;
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secretFile = "${credentialDir}/secret";
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clientIdFile = "${credentialDir}/client_id";
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# Where the credential lives in the store, spelled from the same pieces the
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# writer uses. Whoever writes it and whoever reads it must agree, and the
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# agreement belongs in one visible place.
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#
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# ⚠️ The `hives/<name>` segment is not decoration — it is what the reader's
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# own grant covers, so a path outside it is a 403 rather than a miss, however
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# correct it looks. `swarm-secret-client`'s `queue::agent_client_path` builds
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# the same string from the same pieces; this literal is the nix half of that
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# one agreement.
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#
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# `hiveName` has no fallback here for the reason ./glue-bao-tls.nix gives at
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# its own use of it: it is asserted set wherever
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# `deploy.hive-controller.enable` is.
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credentialPath = "secret/swarm/hives/${hyperhiveCfg.hiveName}/queue/agent";
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atomicWriteSecret = import ./lib/atomic-write-secret.nix { };
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storeRetry = import ./lib/store-retry.nix { };
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in
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{
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options.services.hyperhive.deploy.hive-controller.queue = {
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agentCredentialDir = lib.mkOption {
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type = lib.types.path;
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default = "/var/lib/hyperhive/queue-agent";
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description = ''
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Host directory holding this hive's agent queue credential: `secret`
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(the OIDC client secret, `0600`) and `client_id` (the client that
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secret authenticates, `0644` — it is sent to the token endpoint on
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every connection and is not itself a secret).
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Both files are written by `swarm-bao-queue-agent.service`, which also
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creates this directory. Named here because nothing else creates it:
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the parent `/var/lib/hyperhive` belongs to `hive-c0re.service`'s
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`StateDirectory=`, which re-applies its own mode on every start, and a
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second declaration of *that* path is the two-mechanisms-one-path trap
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./hive-gateway/default.nix records — so this directory is the unit's
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to make and the parent stays c0re's.
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Absent files mean this hive has no queue credential yet, which is what
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a swarm looks like before the publisher on the authelia host has run.
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'';
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};
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};
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config = lib.mkMerge [
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# ⚠️ A SEPARATE arm from the unit below, and that separation is the whole
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# mechanism: the unit's arm is gated on `haveClientIdentity`, so an
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# assertion written inside it could never be reached in the state it
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# exists to report.
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#
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# Shaped after ./swarm-grafana.nix's `haveClientIdentity` assertion — the
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# same refusal, named to this principal's own pair. Where Grafana's gate
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# is `deploy.grafana.enable`, this reader's is the hive's own: every hive
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# runs one for its own agents, so on a hive, reading the store at all is
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# what asks for it. Hence `hiveReaderIdentity` — a host holding no hive
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# leaf has no store to read and nothing is missing.
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(lib.mkIf (deployCfg.hive-controller.enable && hiveReaderIdentity) {
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assertions = [
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{
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assertion = haveClientIdentity;
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message = ''
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This host reads the swarm secret store (services.hyperhive.deploy.bao.clientCertFile
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is set), so it needs the agent queue credential reader's own client
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identity: set both
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services.hyperhive.deploy.bao.queueAgentClientCertFile
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services.hyperhive.deploy.bao.queueAgentClientKeyFile
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swarm-bao-queue-agent.service fetches this hive's agent queue
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credential out of the store, and without these it is not rendered
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at all — leaving hive-c0re with no queue credential and no unit
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that would ever have written one.
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Every hive runs this reader for its own agents, so unlike the other
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three principals there is no per-service toggle that turns it off:
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a hive that reads the store at all is a hive that needs this pair.
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⚠️ This reader's OWN leaf, not deploy.bao.clientCertFile. That one
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is the hive's, and its grant reads every secret in the store; this
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role reads the one queue-credential path. Pointing this option at
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the hive's leaf would evaluate, deploy and log in — and undo the
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split.
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On a hive that runs the store, glue-bao-tls.nix supplies both as
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defaults and there is nothing to do. Elsewhere the leaf is issued
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from that CA out of band and named here — see docs/swarm/secrets.md.
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'';
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}
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];
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})
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(lib.mkIf (deployCfg.hive-controller.enable && haveClientIdentity) {
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systemd.services.swarm-bao-queue-agent = {
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description = "fetch this hive's agent queue credential from the swarm secret store";
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# Every one of these names a unit that exists only where the store runs.
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# `Requires=` on an absent unit fails the job outright, so the ordering is
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# conditional even though the read is not: off-host there is nothing local
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# to wait for, and the timeout below is what bounds the attempt instead.
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after = lib.optionals baoDeploy.enable [
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"swarm-bao-pki.service"
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"container@${baoCfg.machine}.service"
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];
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wants = lib.optionals baoDeploy.enable [ "container@${baoCfg.machine}.service" ];
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requires = lib.optionals baoDeploy.enable [ "swarm-bao-pki.service" ];
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# Ordered before hive-c0re, so no agent container renders ahead of an
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# attempt at its credential. `Wants=`, not `Requires=`: a store this
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# unit can't reach delays hive-c0re's start by one attempt
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# (`TimeoutStartSec` below) rather than failing it — hive-c0re starts
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# after that attempt with whatever credential is on disk, while
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# ./lib/store-retry.nix keeps retrying in the background.
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before = [ "hive-c0re.service" ];
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wantedBy = [
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"multi-user.target"
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"hive-c0re.service"
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];
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path = [
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baoDeploy.package
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pkgs.coreutils
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];
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# ./lib/store-retry.nix.
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inherit (storeRetry) startLimitBurst startLimitIntervalSec;
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serviceConfig = storeRetry.serviceConfig // {
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Type = "oneshot";
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RemainAfterExit = true;
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# What actually bounds each attempt at the reads below. Stated here
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# rather than left to systemd's default, so the number a boot waits on
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# is in the file that waits.
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TimeoutStartSec = 30;
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};
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environment = {
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BAO_ADDR = "https://${baoCfg.domain}:${toString baoCfg.port}";
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BAO_CLIENT_CERT = baoDeploy.queueAgentClientCertFile;
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BAO_CLIENT_KEY = baoDeploy.queueAgentClientKeyFile;
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}
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# Absent means the system trust store, which is what a deployment with a
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# real CA wants and what a self-signed one must not be left with.
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// lib.optionalAttrs (baoDeploy.serverCaFile != null) {
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BAO_CACERT = baoDeploy.serverCaFile;
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};
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script = ''
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set -euo pipefail
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${atomicWriteSecret}
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# `bao`'s own message is the only thing separating a missing value from
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# a refused identity from an unreachable host. This unit's degraded
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# mode is correct for all three, so it reports which one rather than
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# asserting all three in a sentence of ours.
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err="$(mktemp)"
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trap 'rm -f "$err"' EXIT
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# Cert auth is a login, not a transport setting. The `BAO_CLIENT_*`
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# variables above only decide which certificate the TLS handshake
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# presents; without a token `bao` asks its token helper instead, and
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# that is a `sh` this unit's `path` does not carry. `-token-only`
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# answers on stdout and skips the helper on both sides.
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#
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# Fails LOUDLY, unlike the reads below: the three states a login
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# failure covers — store not up, sealed, role not written yet — are all
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# things a retry fixes, and `Restart=on-failure` above is what retries.
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if ! BAO_TOKEN="$(bao login -method=cert -token-only 2>"$err")"; then
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echo "could not log in to swarm-bao with this host's certificate; leaving the queue credential in ${credentialDir} as it is." >&2
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if [ -s "$err" ]; then
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cat "$err" >&2
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else
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echo "bao failed without writing a diagnostic." >&2
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fi
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exit 1
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fi
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export BAO_TOKEN
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# Two reads of one object rather than one `-format=json` parsed with
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# `jq`: no sibling unit carries `jq` on its `path`, and the pair cannot
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# actually disagree — the client id is derived from this hive's name, so
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# a rotation landing between these two calls changes the secret and
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# rewrites the same id.
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if ! secret="$(bao kv get -field=value ${lib.escapeShellArg credentialPath} 2>"$err")"; then
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echo "swarm-bao did not return ${credentialPath}; this hive's agents have no queue credential yet." >&2
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if [ -s "$err" ]; then
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cat "$err" >&2
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else
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echo "bao failed without writing a diagnostic." >&2
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fi
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exit 0
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fi
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if ! client_id="$(bao kv get -field=client_id ${lib.escapeShellArg credentialPath} 2>"$err")"; then
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echo "${credentialPath} holds no client_id; the secret alone is not a usable credential, so nothing is written." >&2
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if [ -s "$err" ]; then
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cat "$err" >&2
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else
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echo "bao failed without writing a diagnostic." >&2
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fi
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exit 0
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fi
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# Both or neither: a client that finds one of the two comes up "fine"
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# and never connects.
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if [ -z "$secret" ] || [ -z "$client_id" ]; then
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echo "swarm-bao returned an empty field of ${credentialPath}; leaving the files as they are." >&2
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exit 0
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fi
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install -d -m 0755 ${lib.escapeShellArg credentialDir}
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atomic_write_secret 0600 "" ${lib.escapeShellArg secretFile} "$secret"
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# `0644` on purpose: an OIDC client id is presented to the token
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# endpoint on every connection and is public by construction.
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atomic_write_secret 0644 "" ${lib.escapeShellArg clientIdFile} "$client_id"
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'';
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};
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})
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];
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}
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