swarm-logs-auth: check agent tokens on the log store's query route

A new `auth_request` responder on the log store's host. nginx sends it
every `/select/logsql/` request whose `Authorization` is
`Bearer swarm-agent.<agent>.<secret>`; it answers 200 when the secret is
the one stored at `swarm/agents/<agent>/queue` (`swarm-agent-verify`),
401 otherwise. Every other bearer still goes to authelia, so agents
still presenting the hive's shared OIDC client keep working.

`auth_request` takes a fixed URI, so the split is a `map` on
`$http_authorization` plus an internal location that rewrites to the
map's pick. Checked against nginx 1.30.5 with stub upstreams: an agent
token only the stub validator accepts gets 200, a token only the stub
authelia accepts gets 200, every wrong one 401, and the internal
locations 404 from outside.

The responder serves a unix socket in its own traverse-only runtime
directory and reads the store under its own leaf
(`swarm-logs-auth`), whose policy is `swarm/agents/+/queue`, read-only.
glue-bao-tls mints the leaf where the store runs; elsewhere the
operator places it, and eval refuses a log store host without one.

Part of #4459.

CLAUDE.md

@@ -193,6 +193,15 @@ hand-maintained per-file tree drifts out of sync with the code.
   `claude --print` per classification (no tools, no session) and replies
   with the rows and the overall verdict. Holds no forge credential. Design:
   [`docs/swarm/review-classifier.md`](docs/swarm/review-classifier.md).
+- **`swarm-agent-verify/`** — the check that a presented
+  `swarm-agent.<agent>.<secret>` token holds the secret stored at
+  `swarm/agents/<agent>/queue`, read under the verifier's own certificate.
+  Shared by `swarm-nats-auth` (the queue's auth callout) and
+  `swarm-logs-auth`.
+- **`swarm-logs-auth/`** — the log store gateway's `auth_request` responder
+  for agents: nginx sends it `/select/logsql/` requests carrying an agent
+  token, it answers 200 or 401 via `swarm-agent-verify`. Runs on the log
+  store's host (`swarm-victorialogs.nix`).
 - **`swarmctl/`** — swarm-level operator CLI, installed by the
   swarm-controller module on the host that runs the daemon. Runs as
   **root and acts directly** — it serves no socket, publishes no HTTP

Cargo.lock

@@ -4884,6 +4884,21 @@ dependencies = [
  "swarm-queue-client",
 ]
 
+[[package]]
+name = "swarm-logs-auth"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "axum",
+ "clap",
+ "swarm-agent-verify",
+ "swarm-queue-client",
+ "swarm-secret-client",
+ "tokio",
+ "tracing",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "swarm-matrix-client"
 version = "0.1.0"

Cargo.toml

@@ -35,6 +35,7 @@ members = [
   "swarm-queue-client",
   "swarm-review-classifier",
   "swarm-logs",
+  "swarm-logs-auth",
   "swarm-secret-client",
   "swarmctl",
 ]

docs/trust-boundary/security.md

@@ -82,6 +82,13 @@ A hive reads no **swarm service's** OIDC client secret. Every reader of
 collector and the store forwarder each fetch theirs with a leaf of their own,
 and the store's granter fetches the bao UI's.
 
+Two services read **every agent's queue secret**
+(`swarm/agents/<agent>/queue`), each under a leaf of its own whose policy
+reaches that one leaf per agent and nothing else: the queue's auth callout
+(`swarm-nats-auth`) and the log store's agent check (`swarm-logs-auth`, on the
+log store's host). Either one compromised can present any agent's queue
+secret, at the queue and at the log store's query route alike.
+
 ### Per-hive credentials live under the hive kind
 
 `swarm_secret_client::policy` scopes the **hive** stanza narrowly (unlike the

flake.nix

@@ -154,6 +154,9 @@
               services.hyperhive.deploy.swarm-ui.package =
                 lib.mkDefault
                   self.packages.${pkgs.stdenv.hostPlatform.system}.swarm-ui;
+              services.hyperhive.deploy.victorialogs.authPackage =
+                lib.mkDefault
+                  self.packages.${pkgs.stdenv.hostPlatform.system}.swarm-logs-auth;
               services.hyperhive.deploy.nats.authPackage =
                 lib.mkDefault
                   self.packages.${pkgs.stdenv.hostPlatform.system}.swarm-nats-auth;

nix/host-modules/default.nix

@@ -33,6 +33,7 @@
     ./glue-forge-oidc-client.nix
     ./glue-grafana-oidc-client.nix
     ./glue-hive-tls-bao-identity.nix
+    ./glue-logs-auth-bao-identity.nix
     ./glue-matrix-ctl-bao-identity.nix
     ./glue-matrix-oidc-client.nix
     ./glue-nats-auth-bao-identity.nix

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

@@ -270,6 +270,13 @@ in
         [ -s ${pkiDir}/nats-auth.pem ] || ${signLeaf} ${pkiDir} nats-auth \
           ${lib.escapeShellArg deployCfg.bao.natsAuthCommonName} "" clientAuth
 
+        # The log store's agent auth responder, which reads agent queue
+        # credentials. Minted here for the matrix-ctl leaf's reason: the log
+        # store is a swarm singleton, so elsewhere this is the file an operator
+        # copies.
+        [ -s ${pkiDir}/logs-auth.pem ] || ${signLeaf} ${pkiDir} logs-auth \
+          ${lib.escapeShellArg deployCfg.bao.logsAuthCommonName} "" clientAuth
+
         # The CI runner's token fetch. Minted here for the matrix-ctl leaf's
         # reason: the runner is a swarm singleton, so on a runner host without
         # the store this is the file an operator copies.

nix/host-modules/glue-logs-auth-bao-identity.nix

@@ -0,0 +1,31 @@
+# Glue: point the log store's agent auth responder at the bao leaf minted for it.
+#
+# ONE PAIRING PER FILE — the swarm-logs-auth principal ← bao, and nothing else.
+# Deleting this leaves a log store with no responder identity unless the
+# operator names one, which ./swarm-victorialogs.nix refuses at eval.
+#
+# ⚠️ The minting is NOT here. ./glue-bao-tls.nix holds the CA and signs the
+# leaf. What belongs here is the pairing: which paths the responder presents.
+#
+# ⚠️ Gated on the store running on this host, the only place the leaf is
+# minted. A log-store host without the store gets no default here; the
+# operator places the responder's leaf and names it.
+#
+# Everything is `mkDefault`. An operator naming their own paths wins.
+{
+  lib,
+  config,
+  ...
+}:
+let
+  deployCfg = config.services.hyperhive.deploy;
+  pkiDir = import ./lib/bao-pki-dir.nix;
+in
+{
+  config = lib.mkIf (deployCfg.victorialogs.enable && deployCfg.bao.enable) {
+    services.hyperhive.deploy.victorialogs = {
+      authBaoClientCertFile = lib.mkDefault "${pkiDir}/logs-auth.pem";
+      authBaoClientKeyFile = lib.mkDefault "${pkiDir}/logs-auth-key.pem";
+    };
+  };
+}

nix/host-modules/swarm-bao.nix

@@ -964,6 +964,17 @@ let
     }
   '';
 
+  # The log store's agent auth responder, which checks the secret an agent
+  # presents against the one stored for it: the same `+` leaf as the queue
+  # responder's, and nothing else.
+  logsAuthReaders = [
+    {
+      name = "swarm-logs-auth";
+      cn = baoDeploy.logsAuthCommonName;
+      policyText = readStanza "${credentialMountPath}/data/swarm/agents/+/queue";
+    }
+  ];
+
   # The CI runner's token fetch. The one reader of the path, which the
   # controller writes and cannot read back.
   ciRunnerReaders = [
@@ -1797,6 +1808,19 @@ in
       '';
     };
 
+    logsAuthCommonName = lib.mkOption {
+      type = lib.types.str;
+      default = "swarm-logs-auth";
+      description = ''
+        Subject the store's `swarm-logs-auth` cert-auth role accepts: the
+        identity the log store's agent auth responder presents to read agent
+        queue credentials, `swarm/agents/<agent>/queue` and nothing else under
+        an agent.
+
+        ⚠️ Reserved as a hive name by ./swarm.nix, like its siblings.
+      '';
+    };
+
     ciRunnerCommonName = lib.mkOption {
       type = lib.types.str;
       default = "swarm-ci-runner";
@@ -3171,6 +3195,8 @@ in
 
       systemd.services.swarm-bao-nats-auth-policy = readerPolicyUnit "write the queue responder's agent-credential-reader bao policy and cert-auth role" natsAuthReaders;
 
+      systemd.services.swarm-bao-logs-auth-policy = readerPolicyUnit "write the log store responder's agent-credential-reader bao policy and cert-auth role" logsAuthReaders;
+
       systemd.services.swarm-bao-ci-runner-policy = readerPolicyUnit "write the CI runner's registration-token-reader bao policy and cert-auth role" ciRunnerReaders;
 
       systemd.services.swarm-bao-review-classifier-policy = readerPolicyUnit "write the review classifier's API-key-reader bao policy and cert-auth role" reviewClassifierReaders;
@@ -3302,6 +3328,7 @@ in
           "swarm-bao-nats-tls-policy.service"
           "swarm-bao-hive-leaf-policy.service"
           "swarm-bao-ci-runner-policy.service"
+          "swarm-bao-logs-auth-policy.service"
           "swarm-bao-forge-publisher-policy.service"
         ]
         ++ granterAfter;

nix/host-modules/swarm-victorialogs.nix

@@ -52,6 +52,22 @@ let
     error_page 401 =302 https://${hyperhiveCfg.swarm.authelia.domain}/?rd=$target_url;
   '';
 
+  # The agents' `auth_request` responder (`swarm-logs-auth`). Its socket's
+  # directory holds that socket alone and is traverse-only for others, the
+  # shape `swarm-controller.nix` gives its own.
+  logsAuthUnit = "swarm-logs-auth";
+  logsAuthSocket = "/run/${logsAuthUnit}/auth.sock";
+  logsAuthCredential = id: "/run/credentials/${logsAuthUnit}.service/${id}";
+  # Credential id → host path of the responder's store identity.
+  logsAuthStoreFiles = {
+    "bao-client.pem" = deployCfg.victorialogs.authBaoClientCertFile;
+    "bao-client-key.pem" = deployCfg.victorialogs.authBaoClientKeyFile;
+  }
+  // lib.optionalAttrs (deployCfg.bao.serverCaFile != null) {
+    "bao-ca.pem" = deployCfg.bao.serverCaFile;
+  };
+  baoCfg = hyperhiveCfg.swarm.bao;
+
   # Shared host netns, like every sibling swarm container: the collector
   # and Grafana reach this at 127.0.0.1:<port>.
   privateNetwork = false;
@@ -88,7 +104,74 @@ in
     '';
   };
 
+  options.services.hyperhive.deploy.victorialogs.authPackage = lib.mkOption {
+    type = lib.types.package;
+    defaultText = lib.literalExpression "hyperhive.packages.\${system}.swarm-logs-auth";
+    description = ''
+      The `swarm-logs-auth` package: the gateway's `auth_request` responder
+      that checks an agent's `swarm-agent.<agent>.<secret>` bearer on
+      `/select/logsql/` against the secret store.
+    '';
+  };
+
+  options.services.hyperhive.deploy.victorialogs.authBaoClientCertFile = lib.mkOption {
+    type = lib.types.nullOr lib.types.str;
+    default = null;
+    example = "/var/lib/swarm-bao-pki/logs-auth.pem";
+    description = ''
+      Client certificate `swarm-logs-auth` presents to the swarm's secret store
+      to read agents' queue secrets. Its subject must be
+      {option}`services.hyperhive.deploy.bao.logsAuthCommonName`.
+
+      Required when `deploy.victorialogs.enable` is set; unset fails at eval.
+      ./glue-logs-auth-bao-identity.nix points it at the leaf
+      ./glue-bao-tls.nix mints on a host that runs the store; on any other
+      log-store host it is a file the operator places.
+
+      A path, never a value.
+    '';
+  };
+
+  options.services.hyperhive.deploy.victorialogs.authBaoClientKeyFile = lib.mkOption {
+    type = lib.types.nullOr lib.types.str;
+    default = null;
+    example = "/var/lib/swarm-bao-pki/logs-auth-key.pem";
+    description = ''
+      Private key for {option}`services.hyperhive.deploy.victorialogs.authBaoClientCertFile`.
+      A path, never a value.
+    '';
+  };
+
   config = lib.mkIf deployCfg.victorialogs.enable {
+    assertions = [
+      {
+        assertion =
+          deployCfg.victorialogs.authBaoClientCertFile != null
+          && deployCfg.victorialogs.authBaoClientKeyFile != null;
+        message = ''
+          services.hyperhive.deploy.victorialogs.authBaoClientCertFile and
+          authBaoClientKeyFile must both be set.
+
+          swarm-logs-auth reads agents' queue secrets from the swarm's secret
+          store with this certificate. They default to the leaf the store
+          mints where services.hyperhive.deploy.bao.enable is set on this
+          host; elsewhere, issue a leaf whose CN is
+          services.hyperhive.deploy.bao.logsAuthCommonName and name it in
+          both options.
+        '';
+      }
+    ];
+
+    # Which check a `/select/logsql/` request gets. `auth_request` takes a
+    # fixed URI, so it names `/__swarm_logs_auth`, which rewrites to the
+    # target this map picks from the caller's `Authorization`.
+    services.nginx.appendHttpConfig = ''
+      map $http_authorization $swarm_logs_auth_target {
+        "~^Bearer swarm-agent\." /__swarm_logs_agent_auth;
+        default /__hive_authelia;
+      }
+    '';
+
     # This store publishes its own health as prometheus metrics on the same
     # listener it serves queries on, so the swarm's collector scrapes it with
     # no exporter and no extra port — same arrangement as the metrics store.
@@ -174,12 +257,35 @@ in
           # logs. That is the rule in force, not an omission: read
           # permissions are a later thing, and this location is where one
           # attaches when it exists.
+          #
+          # Two checks: an agent's own `swarm-agent.` bearer goes to
+          # `swarm-logs-auth`, anything else to authelia (`appendHttpConfig`
+          # above picks).
           "^~ /select/logsql/" = {
             # No URI part, so the request path and its query string reach
             # the store as the caller sent them.
             proxyPass = "http://127.0.0.1:${toString cfg.port}";
             extraConfig = ''
-              auth_request /__hive_authelia;
+              auth_request /__swarm_logs_auth;
+            '';
+          };
+
+          # `rewrite … last` re-matches locations, so the subrequest lands in
+          # one of the two internal locations named by the map.
+          "= /__swarm_logs_auth" = {
+            extraConfig = ''
+              internal;
+              rewrite ^ $swarm_logs_auth_target last;
+            '';
+          };
+
+          # The `Authorization` header rides the subrequest unchanged.
+          "= /__swarm_logs_agent_auth" = {
+            proxyPass = "http://unix:${logsAuthSocket}:/";
+            extraConfig = ''
+              internal;
+              proxy_pass_request_body off;
+              proxy_set_header Content-Length "";
             '';
           };
 
@@ -207,6 +313,53 @@ in
         };
       };
 
+    # The agents' check on `/select/logsql/`. On the host rather than in the
+    # store's container: it needs nothing of the store, only nginx's reach to
+    # its socket and its own store identity.
+    systemd.services.${logsAuthUnit} = {
+      description = "swarm log store auth_request responder for agent credentials";
+      wantedBy = [ "multi-user.target" ];
+      # Where the store's PKI is minted on this host, the leaf is one of its
+      # files. Ordering only: elsewhere the unit does not exist.
+      after = [
+        "network.target"
+        "swarm-bao-pki.service"
+      ];
+      serviceConfig = {
+        ExecStart = lib.concatStringsSep " " [
+          "${deployCfg.victorialogs.authPackage}/bin/swarm-logs-auth"
+          "--socket ${logsAuthSocket}"
+          # The role ./swarm-bao.nix writes on the store's `cert` mount.
+          "--store-cert-role swarm-logs-auth"
+        ];
+        # Paths only: `argv` is world-readable via /proc/<pid>/cmdline.
+        LoadCredential = lib.mapAttrsToList (id: path: "${id}:${path}") logsAuthStoreFiles;
+        DynamicUser = true;
+        RuntimeDirectory = logsAuthUnit;
+        # Traverse-only for others, so nginx reaches the socket path.
+        RuntimeDirectoryMode = "0751";
+        # The path never vanishes from under a running nginx; the responder
+        # unlinks a stale socket as it starts.
+        RuntimeDirectoryPreserve = "yes";
+        Restart = "on-failure";
+        RestartSec = "5s";
+        SyslogIdentifier = logsAuthUnit;
+        ProtectSystem = "strict";
+        ProtectHome = true;
+        PrivateTmp = true;
+        PrivateDevices = true;
+        NoNewPrivileges = true;
+      };
+      environment = {
+        BAO_ADDR = "https://${baoCfg.domain}:${toString baoCfg.port}";
+        BAO_CLIENT_CERT = logsAuthCredential "bao-client.pem";
+        BAO_CLIENT_KEY = logsAuthCredential "bao-client-key.pem";
+      }
+      // lib.optionalAttrs (logsAuthStoreFiles ? "bao-ca.pem") {
+        BAO_CACERT = logsAuthCredential "bao-ca.pem";
+      };
+    };
+
     containers.${cfg.machine} = {
       autoStart = true;
       ephemeral = false;

nix/host-modules/swarm.nix

@@ -55,6 +55,7 @@ let
     deployCfg.bao.granterCommonName
     deployCfg.bao.natsAuthCommonName
     deployCfg.bao.ciRunnerCommonName
+    deployCfg.bao.logsAuthCommonName
     deployCfg.bao.reviewClassifierCommonName
     deployCfg.bao.forgePublisherCommonName
   ]

nix/module-eval/bao-grants.nix

@@ -169,7 +169,7 @@ let
     _: u: (u.environment.BAO_CLIENT_CERT or null) == granterCertFile
   ) baoGrantWithConsumers.systemd.services;
 
-  # The sixteen units that write a `swarm-*` grant, by name, for the discovery
+  # The seventeen units that write a `swarm-*` grant, by name, for the discovery
   # control below.
   grantingUnitNames = [
     "swarm-bao-controller-policy"
@@ -186,6 +186,7 @@ let
     "swarm-bao-operator-viewer-policy"
     "swarm-bao-hive-leaf-policy"
     "swarm-bao-ci-runner-policy"
+    "swarm-bao-logs-auth-policy"
     "swarm-bao-forge-publisher-policy"
     "swarm-bao-review-classifier-policy"
   ];
@@ -704,6 +705,31 @@ let
         in
         lib.hasInfix "/nats-auth.pem ]" s && lib.hasInfix "swarm-nats-auth \"\" clientAuth" s;
     }
+    {
+      # The same `+` leaf as the queue responder, read-only, and nothing else:
+      # this principal checks a presented secret and does nothing with it.
+      name = "the log store responder's grant is every agent's queue secret, read-only, and nothing else";
+      ok =
+        let
+          s = baoGrantHere.systemd.services.swarm-bao-logs-auth-policy.script;
+        in
+        lib.hasInfix "path \"secret/data/swarm/agents/+/queue\" {\n  capabilities = [\"read\"]\n}" s
+        && lib.length (lib.filter lib.isList (builtins.split "path \"" s)) == 1
+        && !(lib.hasInfix "secret/data/swarm/agents/*" s)
+        && !(lib.hasInfix "secret/data/swarm/hives" s)
+        && !(lib.hasInfix "secret/data/swarm/services" s)
+        && lib.hasInfix "auth/cert/certs/swarm-logs-auth" s
+        && lib.hasInfix "allowed_common_names=swarm-logs-auth" s
+        && lib.hasInfix "token_policies=swarm-logs-auth" s;
+    }
+    {
+      name = "the PKI unit signs the log store responder's leaf under its own subject";
+      ok =
+        let
+          s = baoGrantHere.systemd.services.swarm-bao-pki.script;
+        in
+        lib.hasInfix "/logs-auth.pem ]" s && lib.hasInfix "swarm-logs-auth \"\" clientAuth" s;
+    }
     {
       # 🩸 The half that makes the policies above bind: a policy grants only
       # through a token that carries it, and a token is minted by a cert-auth
@@ -915,24 +941,24 @@ let
     }
     {
       # A store host without the granter's pair writes its grants some other
-      # way, so none of the sixteen units may exist. Without this arm
+      # way, so none of the seventeen units may exist. Without this arm
       # `lib.mkIf haveGranter` could be dropped from any of them and every other
       # case here would still pass.
-      name = "without the granter's pair none of the sixteen granting units render";
+      name = "without the granter's pair none of the seventeen granting units render";
       ok =
         let
           s = baoGranterOptOut.systemd.services;
         in
         lib.all (unit: !(s ? ${unit})) (grantingUnitNames ++ [ "swarm-bao-granter-role" ])
-        # The control: the same store with the pair renders all sixteen.
+        # The control: the same store with the pair renders all seventeen.
         && lib.all (unit: baoGrantHere.systemd.services ? ${unit}) grantingUnitNames;
     }
     {
-      # 🩸 What replaced the silent skip. With no bootstrap token the sixteen still
+      # 🩸 What replaced the silent skip. With no bootstrap token the seventeen still
       # render, and a refused granter fails them with the step that fixes it.
       # A store host that never named a token is told to name one, since the
       # unit that sets the granter up renders only where it has.
-      name = "a store host without a bootstrap token renders the sixteen, each failing loudly with the one-time step";
+      name = "a store host without a bootstrap token renders the seventeen, each failing loudly with the one-time step";
       ok =
         let
           s = baoGranterNoToken.systemd.services;
@@ -1695,8 +1721,8 @@ let
     }
     {
       # What makes the case above mean something: discovery by the granter's
-      # certificate reaches all sixteen units, and each yields calls.
+      # certificate reaches all seventeen units, and each yields calls.
-      name = "the granter-policy check sees all sixteen granting units, and parses calls from each";
+      name = "the granter-policy check sees all seventeen granting units, and parses calls from each";
       ok =
         lib.sort lib.lessThan (lib.attrNames granterUnits) == lib.sort lib.lessThan grantingUnitNames
         && lib.all (u: baoCalls u.script != [ ]) (lib.attrValues granterUnits)

nix/module-eval/core-toggle.nix

@@ -504,6 +504,44 @@ let
         && !(lib.hasInfix "$args" q.extraConfig)
         && !(lib.hasInfix "?" q.proxyPass);
     }
+    {
+      # `auth_request` takes a fixed URI, so the split between the agents'
+      # responder and authelia is a map plus a rewrite in an internal
+      # location. Every link of that chain is pinned: the map keys on the
+      # agent-token prefix and falls back to authelia, the query location
+      # names the switch, the switch rewrites to the map's pick, and the
+      # agent target reaches the responder's socket, which the unit binds.
+      name = "the machine query location sends agent bearers to swarm-logs-auth and the rest to authelia";
+      ok =
+        let
+          l = allLocal.services.nginx.virtualHosts."logs.t.local".locations;
+          http = allLocal.services.nginx.appendHttpConfig;
+          unit = allLocal.systemd.services.swarm-logs-auth;
+        in
+        lib.hasInfix "map \$http_authorization \$swarm_logs_auth_target" http
+        && lib.hasInfix "\"~^Bearer swarm-agent\\.\" /__swarm_logs_agent_auth;" http
+        && lib.hasInfix "default /__hive_authelia;" http
+        && lib.hasInfix "auth_request /__swarm_logs_auth;" l."^~ /select/logsql/".extraConfig
+        && lib.hasInfix "rewrite ^ \$swarm_logs_auth_target last;" l."= /__swarm_logs_auth".extraConfig
+        && lib.hasInfix "internal;" l."= /__swarm_logs_agent_auth".extraConfig
+        && l."= /__swarm_logs_agent_auth".proxyPass == "http://unix:/run/swarm-logs-auth/auth.sock:/"
+        && lib.hasInfix "--socket /run/swarm-logs-auth/auth.sock" unit.serviceConfig.ExecStart
+        && l ? "= /__hive_authelia";
+    }
+    {
+      # The responder reads the store as itself, with the leaf the store's
+      # host mints for it.
+      name = "swarm-logs-auth presents its own store leaf";
+      ok =
+        let
+          v = allLocal.services.hyperhive.deploy.victorialogs;
+          lc = allLocal.systemd.services.swarm-logs-auth.serviceConfig.LoadCredential;
+        in
+        lib.hasSuffix "/logs-auth.pem" v.authBaoClientCertFile
+        && lib.hasSuffix "/logs-auth-key.pem" v.authBaoClientKeyFile
+        && builtins.elem "bao-client.pem:${v.authBaoClientCertFile}" lc
+        && builtins.elem "bao-client-key.pem:${v.authBaoClientKeyFile}" lc;
+    }
     {
       # The absence arm for the case above, and the option's own rule — a
       # service declares its entry under its own `enable` — made checkable.

nix/packages/default.nix

@@ -163,6 +163,10 @@ in
   # rather than every hive's.
   swarm-nats-auth = mkBinPackage "swarm-nats-auth" "hyperhive swarm queue auth-callout responder";
 
+  # The log store gateway's `auth_request` responder for agents. Out of
+  # `daemonBins` like the responder above: it runs on the log store's host only.
+  swarm-logs-auth = mkBinPackage "swarm-logs-auth" "hyperhive swarm log store agent auth responder";
+
   # The matrix container's control binary; `mint` publishes the sender token. Out of `daemonBins` for
   # "runs *inside* a container, not on the host" reason as the responder
   # above, and with a second one: putting it in the core bundle would place

swarm-logs-auth/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "swarm-logs-auth"
+version.workspace = true
+edition.workspace = true
+
+[[bin]]
+name = "swarm-logs-auth"
+path = "src/main.rs"
+
+[dependencies]
+anyhow.workspace = true
+axum.workspace = true
+clap.workspace = true
+swarm-agent-verify.workspace = true
+# The agent-token spelling, and the rustls provider the store client needs.
+swarm-queue-client.workspace = true
+swarm-secret-client.workspace = true
+tokio.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+
+[lints]
+workspace = true

swarm-logs-auth/src/main.rs

@@ -0,0 +1,160 @@
+//! The log store gateway's `auth_request` responder for agents.
+//!
+//! nginx sends it every `/select/logsql/` request whose `Authorization` is
+//! `Bearer swarm-agent.<agent>.<secret>` (`swarm-victorialogs.nix`). It answers
+//! 200 when the secret is the one stored at `swarm/agents/<agent>/queue`, and
+//! 401 otherwise, store failures included: `auth_request` turns any other
+//! status into a 500 for the caller.
+//!
+//! It reads the store under its own certificate, whose policy reaches every
+//! agent's `queue` secret and nothing else. It serves a unix socket whose
+//! directory only the gateway's nginx may enter.
+
+use std::os::unix::fs::PermissionsExt as _;
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::time::Duration;
+
+use anyhow::Context as _;
+use axum::extract::State;
+use axum::http::{HeaderMap, StatusCode, header};
+use clap::Parser;
+use swarm_agent_verify::CredentialSource;
+use swarm_queue_client::agent_token::parse_agent_token;
+
+/// How long one store lookup may take before the request is denied. Well
+/// under nginx's 60s `proxy_read_timeout`, so a slow store reads as a 401
+/// rather than a gateway timeout.
+const LOOKUP_TIMEOUT: Duration = Duration::from_secs(5);
+
+#[derive(Parser)]
+#[command(about = "auth_request responder: checks an agent's queue secret against the store")]
+struct Args {
+    /// Unix socket to serve on.
+    #[arg(long)]
+    socket: PathBuf,
+    /// Cert-auth role this responder logs in to the store as.
+    #[arg(long, default_value = "swarm-logs-auth")]
+    store_cert_role: String,
+}
+
+/// The answer for one subrequest's `Authorization` header.
+async fn decide(source: &impl CredentialSource, authorization: Option<&str>) -> StatusCode {
+    let Some(token) = authorization.and_then(|v| v.strip_prefix("Bearer ")) else {
+        tracing::warn!("no bearer token; denying");
+        return StatusCode::UNAUTHORIZED;
+    };
+    let token = match parse_agent_token(token) {
+        Some(Ok(token)) => token,
+        Some(Err(e)) => {
+            tracing::warn!(error = %e, "malformed agent token; denying");
+            return StatusCode::UNAUTHORIZED;
+        }
+        None => {
+            tracing::warn!("not an agent token; denying");
+            return StatusCode::UNAUTHORIZED;
+        }
+    };
+    if swarm_agent_verify::verify(source, &token, LOOKUP_TIMEOUT).await {
+        tracing::info!(agent = token.agent, "verified");
+        StatusCode::OK
+    } else {
+        StatusCode::UNAUTHORIZED
+    }
+}
+
+async fn handle(
+    State(store): State<Arc<swarm_agent_verify::Store>>,
+    headers: HeaderMap,
+) -> StatusCode {
+    let authorization = headers
+        .get(header::AUTHORIZATION)
+        .and_then(|v| v.to_str().ok());
+    decide(store.as_ref(), authorization).await
+}
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    swarm_queue_client::install_crypto_provider();
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("info")),
+        )
+        // stdout is journald, which keeps ANSI escapes as raw bytes.
+        .with_ansi(false)
+        .init();
+    let args = Args::parse();
+
+    let settings = swarm_secret_client::client::Settings::from_env()
+        .context("reading the secret store's address and this responder's identity")?;
+    let store = Arc::new(swarm_agent_verify::Store::new(
+        settings,
+        args.store_cert_role,
+    ));
+
+    // `RuntimeDirectoryPreserve=yes` can leave the previous run's socket; the
+    // directory is this unit's alone, so unlinking it is safe.
+    if let Err(e) = std::fs::remove_file(&args.socket)
+        && e.kind() != std::io::ErrorKind::NotFound
+    {
+        return Err(e)
+            .with_context(|| format!("clearing stale socket at {}", args.socket.display()));
+    }
+    let listener = tokio::net::UnixListener::bind(&args.socket)
+        .with_context(|| format!("binding {}", args.socket.display()))?;
+    // nginx is another user and `connect(2)` needs write. The directory is
+    // the access control, not this mode.
+    std::fs::set_permissions(&args.socket, std::fs::Permissions::from_mode(0o666))
+        .with_context(|| format!("chmod {}", args.socket.display()))?;
+    tracing::info!(socket = %args.socket.display(), "swarm-logs-auth listening");
+
+    let app = axum::Router::new().fallback(handle).with_state(store);
+    axum::serve(listener, app).await.context("serving")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use swarm_secret_client::queue::AgentCredential;
+
+    /// A store holding atlas's credential.
+    struct Atlas;
+
+    impl CredentialSource for Atlas {
+        async fn lookup(&self, agent: &str) -> anyhow::Result<Option<AgentCredential>> {
+            Ok((agent == "atlas").then(|| AgentCredential {
+                value: "Ab9_-zSECRET".to_owned(),
+                agent: "atlas".to_owned(),
+                minted_at: None,
+            }))
+        }
+    }
+
+    #[tokio::test]
+    async fn the_stored_secret_is_200() {
+        assert_eq!(
+            decide(&Atlas, Some("Bearer swarm-agent.atlas.Ab9_-zSECRET")).await,
+            StatusCode::OK
+        );
+    }
+
+    #[tokio::test]
+    async fn everything_else_is_401() {
+        for authorization in [
+            None,
+            Some("swarm-agent.atlas.Ab9_-zSECRET"),
+            Some("Basic swarm-agent.atlas.Ab9_-zSECRET"),
+            Some("Bearer swarm-agent.atlas.Ab9_-zSECREX"),
+            Some("Bearer swarm-agent.argus.Ab9_-zSECRET"),
+            Some("Bearer swarm-agent.atlas"),
+            Some("Bearer authelia_at_abc.def"),
+        ] {
+            assert_eq!(
+                decide(&Atlas, authorization).await,
+                StatusCode::UNAUTHORIZED,
+                "{authorization:?}"
+            );
+        }
+    }
+}