bao: mint the controller's leaf, and point the controller at it

glue-bao-tls.nix signs a third leaf. It is minted whether or not a
controller runs here, because the case it serves is the one where it
does not: a controller elsewhere needs a leaf from this CA and cannot
sign one, so issuing it here turns "obtain a certificate out of band"
into "copy this file".

glue-controller-bao-identity.nix holds the pairing and nothing else --
which paths this host's controller reads. Gated on the leaf existing
rather than on deploy.bao.enable, so a controller on the store's host
and one three networks away with an out-of-band leaf get the same
wiring; gating on the store would have made the co-located case the
only supported shape. The directory comes from deploy.bao.clientCertFile
rather than repeating glue-bao-tls.nix's literal, so moving the PKI
moves both.

module-eval gains three cases and two fixtures, because nothing asserted
the PKI script before: an earlier commit added a leaf to that rendered
unit and left the derivation unchanged. The fixture's CN is deliberately
a value no default could supply, so "the role and the leaf both carry
it" says they read one option rather than that both happen to say
swarm-controller.

Gates: 62 module properties hold (59 before, plus these three), on a
derivation hash that actually moved -- this suite is a cache hit when
only fixtures change, so an unchanged hash would have meant the cases
never ran. nix fmt clean, all three scripts/check-*.sh exit 0.

nix/host-modules/default.nix

@@ -24,6 +24,7 @@
     ./hive-tls.nix
     ./otel.nix
     ./glue-bao-tls.nix
+    ./glue-controller-bao-identity.nix
     ./glue-matrix-bao-token.nix
     ./swarm-authelia.nix
     ./swarm-bao.nix

nix/host-modules/glue-bao-tls.nix

@@ -16,8 +16,8 @@
 # ⚠️ Not the hive CA and not the swarm CA. The store will eventually
 # distribute both, and an authority you must already hold a certificate from
 # cannot be one the store hands out — reach the store to get the CA material,
-# need a cert from that CA to reach the store. This CA signs exactly two
-# things and distributes nothing, so it cannot enter that cycle.
+# need a cert from that CA to reach the store. This CA signs a fixed, short
+# list of leaves and distributes nothing, so it cannot enter that cycle.
 #
 # ⚠️ Files like this are the only place a `deploy.<foo>` value may derive from
 # a `deploy.<bar>.enable`. Everywhere else that is forbidden. The exception
@@ -126,6 +126,17 @@ in
           ${lib.escapeShellArg cfg.domain} ${lib.escapeShellArg "DNS:${cfg.domain}"} serverAuth
         [ -s ${pkiDir}/client.pem ] || ${signLeaf} ${pkiDir} client \
           ${lib.escapeShellArg clientCn} "" clientAuth
+
+        # Minted whether or not a controller runs here, because the case it
+        # serves is the one where it does not: a controller elsewhere needs a
+        # leaf from this CA and has no way to sign one. Issuing it here turns
+        # "obtain a certificate out of band" into "copy this file".
+        #
+        # Its own CN rather than the reader's above: the controller's policy
+        # lets it create roles for every hive, and the reader's leaf carries
+        # this hive's name.
+        [ -s ${pkiDir}/controller.pem ] || ${signLeaf} ${pkiDir} controller \
+          ${lib.escapeShellArg deployCfg.bao.controllerCommonName} "" clientAuth
       '';
     };
   };

nix/host-modules/glue-controller-bao-identity.nix

@@ -0,0 +1,41 @@
+# Glue: point the swarm controller at the bao leaf minted for it.
+#
+# ONE PAIRING PER FILE — controller ← bao, and nothing else. Deleting this
+# leaves a controller that takes operator-provided certificate paths, which is
+# what every deployment that does not mint its own already does.
+#
+# ⚠️ The minting is NOT here. ./glue-bao-tls.nix holds the CA and signs the
+# leaf, because the thing that owns a private key owns issuing from it; a
+# second signer would duplicate that file's `openssl` helper to no benefit.
+# What belongs here is the pairing: which paths this host's controller reads.
+#
+# ⚠️ Gated on the leaf existing, not on the store being enabled. A controller
+# on the store's own host is one deployment; a controller three networks away
+# holding a leaf issued out of band is another, and both want the same wiring.
+# `deploy.bao.enable` would have made the first one the only supported shape.
+#
+# Everything is `mkDefault`. An operator naming their own paths wins.
+{
+  lib,
+  config,
+  ...
+}:
+let
+  hyperhiveCfg = config.services.hyperhive;
+  deployCfg = hyperhiveCfg.deploy;
+  baoDeploy = deployCfg.bao;
+
+  # Where ./glue-bao-tls.nix puts the leaves. Derived from the reader's own
+  # path rather than repeating that file's directory literal: an operator who
+  # moves the PKI moves both, and the two cannot drift apart.
+  haveMintedPki = baoDeploy.clientCertFile != null;
+  pkiDir = if haveMintedPki then builtins.dirOf baoDeploy.clientCertFile else null;
+in
+{
+  config = lib.mkIf (hyperhiveCfg.enable && deployCfg.swarm-controller.enable && haveMintedPki) {
+    services.hyperhive.deploy.swarm-controller = {
+      baoClientCertFile = lib.mkDefault "${pkiDir}/controller.pem";
+      baoClientKeyFile = lib.mkDefault "${pkiDir}/controller-key.pem";
+    };
+  };
+}

nix/host-modules/swarm-bao.nix

@@ -154,10 +154,9 @@ let
   # policy by spelling it the same way, and is itself named after it.
   controllerPolicyName = "swarm-controller";
 
-  # The subject the controller's certificate must carry. Cert auth matches on
-  # the CN, so this is an interface rather than a label: a leaf signed by the
-  # right CA but minted with any other subject cannot authenticate.
-  controllerCn = "swarm-controller";
+  # An option rather than a literal because whatever mints the controller's
+  # leaf has to spell it identically, and that lives in another file.
+  controllerCn = baoDeploy.controllerCommonName;
 
   # Derived with `bao write -output-policy`, which short-circuits the request
   # and needs no server, rather than written from memory.
@@ -478,6 +477,27 @@ in
       '';
     };
 
+    controllerCommonName = lib.mkOption {
+      type = lib.types.str;
+      default = "swarm-controller";
+      example = "swarm-controller.svc";
+      description = ''
+        Subject the store's `swarm-controller` cert-auth role accepts. An
+        interface, not a label: cert auth matches on the CN, so whatever mints
+        the controller's leaf has to spell it the same way.
+
+        Lives here because it is a property of the **role**, which this module
+        writes — not a credential belonging to the controller. Nothing outside
+        the store needs it except whatever issues that leaf.
+
+        ⚠️ The CA this role trusts also signs each hive's reader leaf, whose CN
+        is the hive's own name, so a hive named `swarm-controller` would satisfy
+        the role. Changing this to something outside the hive-name grammar
+        (`[a-z0-9-]`) rules that out — at the cost of a role rename in any store
+        that has already run the granting unit.
+      '';
+    };
+
     serverCaFile = lib.mkOption {
       type = lib.types.nullOr lib.types.str;
       default = null;

nix/host-modules/swarm-controller.nix

@@ -467,6 +467,37 @@ in
       '';
     };
 
+    baoClientCertFile = lib.mkOption {
+      type = lib.types.nullOr lib.types.str;
+      default = null;
+      example = "/var/lib/swarm-controller/bao-client.pem";
+      description = ''
+        Certificate this daemon presents to the swarm's secret store. Its
+        subject has to match
+        {option}`services.hyperhive.deploy.bao.controllerCommonName`, which is
+        what the store's cert-auth role matches on.
+
+        Distinct from {option}`services.hyperhive.deploy.bao.clientCertFile` on
+        purpose, and not an oversight: that one is **this host as a reader** and
+        carries the hive's name, while the controller's policy lets it create
+        roles for every hive. One certificate serving both would hand that power
+        to whatever else reads the store here.
+
+        Defaulted by `glue-controller-bao-identity.nix` where this deployment
+        mints its own; elsewhere the leaf is issued out of band and named here.
+      '';
+    };
+
+    baoClientKeyFile = lib.mkOption {
+      type = lib.types.nullOr lib.types.str;
+      default = null;
+      example = "/var/lib/swarm-controller/bao-client-key.pem";
+      description = ''
+        Private key for {option}`services.hyperhive.deploy.swarm-controller.baoClientCertFile`.
+        Both or neither — a certificate with no key authenticates nothing.
+      '';
+    };
+
     queue = {
       clientSecretFile = lib.mkOption {
         type = lib.types.str;

nix/module-eval.nix

@@ -254,6 +254,20 @@ let
   baoGrantNoStore = hive {
     deploy.bao.bootstrapTokenFile = "/run/secrets/bao-bootstrap.token";
   };
+  # Store and controller on one machine, with a CN no default could supply.
+  # The odd value is what lets the case below tell "both ends read the same
+  # option" from "both ends happen to say swarm-controller".
+  baoControllerHere = hive {
+    deploy.bao.enable = true;
+    deploy.bao.bootstrapTokenFile = "/run/secrets/bao-bootstrap.token";
+    deploy.bao.controllerCommonName = "cn-marker-not-a-default";
+    deploy.swarm-controller.enable = true;
+  };
+  # The controller with no store, which is every spread deployment. Nothing
+  # mints here, so the pairing must leave the paths unset rather than name
+  # files this host will never have.
+  controllerNoStore = hive { deploy.swarm-controller.enable = true; };
+
   # The store and the token, with no CA to trust. `mkForce` because the PKI
   # glue supplies one by default here — this is the deployment that brings its
   # own certificates and has not named the authority yet, and it separates
@@ -527,6 +541,49 @@ let
         && lib.hasInfix "auth/cert/certs/swarm-controller" s
         && lib.hasInfix "/var/lib/swarm-bao-tls/client-ca.pem" s;
     }
+    {
+      # Nothing asserted the PKI script before this, so a third leaf could be
+      # added to it and every case still passed — measured, not assumed: the
+      # commit that added one left `module-eval`'s derivation unchanged.
+      name = "the store mints a leaf for the controller, and the controller is pointed at it";
+      ok =
+        let
+          m = baoControllerHere;
+          pki = m.systemd.services.swarm-bao-pki.script;
+        in
+        lib.hasInfix "controller.pem" pki
+        &&
+          m.services.hyperhive.deploy.swarm-controller.baoClientCertFile
+          == "/var/lib/swarm-bao-pki/controller.pem"
+        &&
+          m.services.hyperhive.deploy.swarm-controller.baoClientKeyFile
+          == "/var/lib/swarm-bao-pki/controller-key.pem";
+    }
+    {
+      # What makes the one above mean something: a controller with no store
+      # has nothing to be pointed at. Naming a path here would be a file this
+      # host never gets, which fails at a TLS handshake rather than at eval.
+      name = "a controller on a host with no store is left without certificate paths";
+      ok =
+        let
+          c = controllerNoStore.services.hyperhive.deploy.swarm-controller;
+        in
+        c.baoClientCertFile == null && c.baoClientKeyFile == null;
+    }
+    {
+      # The CN is an interface between two files: the store writes a role that
+      # matches it, the PKI mints a leaf that carries it. They read one option,
+      # and this is what says so — the fixture's value cannot come from a
+      # default, so matching it in both places is not a coincidence.
+      name = "the cert-auth role and the minted leaf take their subject from one option";
+      ok =
+        let
+          m = baoControllerHere;
+          role = m.containers.swarm-bao.config.systemd.services.swarm-bao-controller-policy.script;
+          pki = m.systemd.services.swarm-bao-pki.script;
+        in
+        lib.hasInfix "cn-marker-not-a-default" role && lib.hasInfix "cn-marker-not-a-default" pki;
+    }
     {
       # The arm that makes the one above mean something. A role's trust anchor
       # is the CA, so with none named there is nothing to write — and the