swarm-bao: the agent-token checkers' cert roles issue batch tokens

docs/swarm/secrets.md

@@ -465,6 +465,13 @@ names the hive's own `clientCertFile` and misses a principal's pair has the
 build refused, by the module of the reader it missed, naming that pair — see
 [what a missing leaf costs](#what-a-missing-leaf-costs) below.
 
+The roles of `swarm-nats-auth`, `swarm-logs-auth` and `swarm-metrics-auth` issue
+batch tokens with a five-minute TTL (`token_type=batch`, `token_ttl=5m`). The
+responders log in on every check, and the store keeps no record of a batch token,
+so unauthenticated requests don't grow its token storage. Nothing can renew
+or revoke a batch token. The other roles keep service tokens, because some of
+their readers hold a handle for longer than five minutes.
+
 ### What a missing leaf costs
 
 Each of the three modules asserts its own pair, on the same condition: **this host

nix/host-modules/swarm-bao.nix

@@ -1001,6 +1001,7 @@ let
     {
       name = "swarm-nats-auth";
       cn = baoDeploy.natsAuthCommonName;
+      batchToken = true;
       policyText =
         readStanza "${credentialMountPath}/data/swarm/agents/+/queue"
         + readStanza "${credentialMountPath}/data/swarm/services/${hyperhiveCfg.swarm.nats.clientId}/oidc/client"
@@ -1052,6 +1053,7 @@ let
     {
       name = "swarm-logs-auth";
       cn = baoDeploy.logsAuthCommonName;
+      batchToken = true;
       policyText =
         readStanza "${credentialMountPath}/data/swarm/agents/+/queue"
         + readStanza "${credentialMountPath}/data/${grafanaMetricsBearerLeaf}"
@@ -1069,6 +1071,7 @@ let
     {
       name = "swarm-metrics-auth";
       cn = baoDeploy.metricsAuthCommonName;
+      batchToken = true;
       policyText =
         readStanza "${credentialMountPath}/data/swarm/agents/+/queue"
         + readStanza "${credentialMountPath}/data/${grafanaMetricsBearerLeaf}"
@@ -1182,12 +1185,24 @@ let
   # `swarm` in one — and ./swarm.nix reserves the concrete per-hive spellings
   # anyway, because the prefixes are operator-settable and an operator may spell
   # one without that substring.
-  readerRoleWrite = obj: ''
+  #
+  # `batchToken = true` on an object makes its logins batch tokens, which the
+  # store does not persist and cannot renew or revoke. Only for a principal
+  # that logs in, reads and drops the token within one call: the five
+  # minutes outlast that read, and a leaked token dies as fast. A principal
+  # that holds a handle longer must not set it.
+  readerRoleWrite =
+    obj:
+    let
+      batchArgs = lib.optionalString (obj.batchToken or false
+      ) " \\\n  token_type=batch \\\n  token_ttl=5m";
+    in
+    ''
       bao write auth/cert/certs/${lib.escapeShellArg obj.name} \
         certificate=@${tlsDir}/client-ca.pem \
         allowed_common_names=${lib.escapeShellArg obj.cn} \
         token_policies=${lib.escapeShellArg obj.name} \
-      display_name=${lib.escapeShellArg obj.cn}
+        display_name=${lib.escapeShellArg obj.cn}${batchArgs}
     '';
 
   # A unit that logs in as the granter and runs `body`, ordered after the

nix/module-eval/bao-grants.nix

@@ -815,6 +815,33 @@ let
         && lib.hasInfix "allowed_common_names=swarm-metrics-auth" s
         && lib.hasInfix "token_policies=swarm-metrics-auth" s;
     }
+    {
+      # The three agent-token checkers log in once per check; a batch token
+      # leaves nothing stored per request. The CI runner's role, written by the
+      # same helper, keeps service tokens, and still carries its policy, so a
+      # misspelled script name cannot make the absence pass.
+      name = "the agent-token checkers' roles issue batch tokens and a holder's role does not";
+      ok =
+        let
+          script = unit: baoGrantHere.systemd.services.${unit}.script;
+          batch =
+            unit: role:
+            let
+              s = script unit;
+            in
+            lib.hasInfix "auth/cert/certs/${role} " s
+            && lib.hasInfix "token_type=batch" s
+            && lib.hasInfix "token_ttl=5m" s
+            && !(lib.hasInfix "token_max_ttl" s);
+          ci = script "swarm-bao-ci-runner-policy";
+        in
+        batch "swarm-bao-nats-auth-policy" "swarm-nats-auth"
+        && batch "swarm-bao-logs-auth-policy" "swarm-logs-auth"
+        && batch "swarm-bao-metrics-auth-policy" "swarm-metrics-auth"
+        && lib.hasInfix "token_policies=swarm-ci-runner" ci
+        && !(lib.hasInfix "token_type" ci)
+        && !(lib.hasInfix "token_ttl" ci);
+    }
     {
       name = "the PKI unit signs the metrics store responder's leaf under its own subject";
       ok =