nixos/nats: init

nixos/modules/module-list.nix

@@ -767,6 +767,7 @@
   ./services/networking/namecoind.nix
   ./services/networking/nar-serve.nix
   ./services/networking/nat.nix
+  ./services/networking/nats.nix
   ./services/networking/ndppd.nix
   ./services/networking/nebula.nix
   ./services/networking/networkmanager.nix

nixos/modules/services/networking/nats.nix

@@ -0,0 +1,159 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.nats;
+
+  format = pkgs.formats.json { };
+
+  configFile = format.generate "nats.conf" cfg.settings;
+
+in {
+
+  ### Interface
+
+  options = {
+    services.nats = {
+      enable = mkEnableOption "NATS messaging system";
+
+      user = mkOption {
+        type = types.str;
+        default = "nats";
+        description = "User account under which NATS runs.";
+      };
+
+      group = mkOption {
+        type = types.str;
+        default = "nats";
+        description = "Group under which NATS runs.";
+      };
+
+      serverName = mkOption {
+        default = "nats";
+        example = "n1-c3";
+        type = types.str;
+        description = ''
+          Name of the NATS server, must be unique if clustered.
+        '';
+      };
+
+      jetstream = mkEnableOption "JetStream";
+
+      port = mkOption {
+        default = 4222;
+        example = 4222;
+        type = types.port;
+        description = ''
+          Port on which to listen.
+        '';
+      };
+
+      dataDir = mkOption {
+        default = "/var/lib/nats";
+        type = types.path;
+        description = ''
+          The NATS data directory. Only used if JetStream is enabled, for
+          storing stream metadata and messages.
+
+          If left as the default value this directory will automatically be
+          created before the NATS server starts, otherwise the sysadmin is
+          responsible for ensuring the directory exists with appropriate
+          ownership and permissions.
+        '';
+      };
+
+      settings = mkOption {
+        default = { };
+        type = format.type;
+        example = literalExample ''
+          {
+            jetstream = {
+              max_mem = "1G";
+              max_file = "10G";
+            };
+          };
+        '';
+        description = ''
+          Declarative NATS configuration. See the
+          <link xlink:href="https://docs.nats.io/nats-server/configuration">
+          NATS documentation</link> for a list of options.
+        '';
+      };
+    };
+  };
+
+  ### Implementation
+
+  config = mkIf cfg.enable {
+    services.nats.settings = {
+      server_name = cfg.serverName;
+      port = cfg.port;
+      jetstream = optionalAttrs cfg.jetstream { store_dir = cfg.dataDir; };
+    };
+
+    systemd.services.nats = {
+      description = "NATS messaging system";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+
+      serviceConfig = mkMerge [
+        (mkIf (cfg.dataDir == "/var/lib/nats") {
+          StateDirectory = "nats";
+          StateDirectoryMode = "0750";
+        })
+        {
+          Type = "simple";
+          ExecStart = "${pkgs.nats-server}/bin/nats-server -c ${configFile}";
+          ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
+          ExecStop = "${pkgs.coreutils}/bin/kill -SIGINT $MAINPID";
+          Restart = "on-failure";
+
+          User = cfg.user;
+          Group = cfg.group;
+
+          # Hardening
+          CapabilityBoundingSet = "";
+          LimitNOFILE = 800000; # JetStream requires 2 FDs open per stream.
+          LockPersonality = true;
+          MemoryDenyWriteExecute = true;
+          NoNewPrivileges = true;
+          PrivateDevices = true;
+          PrivateTmp = true;
+          PrivateUsers = true;
+          ProcSubset = "pid";
+          ProtectClock = true;
+          ProtectControlGroups = true;
+          ProtectHome = true;
+          ProtectHostname = true;
+          ProtectKernelLogs = true;
+          ProtectKernelModules = true;
+          ProtectKernelTunables = true;
+          ProtectProc = "invisible";
+          ProtectSystem = "strict";
+          ReadOnlyPaths = [ ];
+          ReadWritePaths = [ cfg.dataDir ];
+          RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+          RestrictNamespaces = true;
+          RestrictRealtime = true;
+          RestrictSUIDSGID = true;
+          SystemCallFilter = [ "@system-service" "~@privileged" "~@resources" ];
+          UMask = "0077";
+        }
+      ];
+    };
+
+    users.users = mkIf (cfg.user == "nats") {
+      nats = {
+        description = "NATS daemon user";
+        isSystemUser = true;
+        group = cfg.group;
+        home = cfg.dataDir;
+      };
+    };
+
+    users.groups = mkIf (cfg.group == "nats") { nats = { }; };
+  };
+
+}

nixos/tests/all-tests.nix

@@ -283,6 +283,7 @@ in
   nat.firewall = handleTest ./nat.nix { withFirewall = true; };
   nat.firewall-conntrack = handleTest ./nat.nix { withFirewall = true; withConntrackHelpers = true; };
   nat.standalone = handleTest ./nat.nix { withFirewall = false; };
+  nats = handleTest ./nats.nix {};
   navidrome = handleTest ./navidrome.nix {};
   ncdns = handleTest ./ncdns.nix {};
   ndppd = handleTest ./ndppd.nix {};

nixos/tests/nats.nix

@@ -0,0 +1,65 @@
+let
+
+  port = 4222;
+  username = "client";
+  password = "password";
+  topic = "foo.bar";
+
+in import ./make-test-python.nix ({ pkgs, lib, ... }: {
+  name = "nats";
+  meta = with pkgs.lib; { maintainers = with maintainers; [ c0deaddict ]; };
+
+  nodes = let
+    client = { pkgs, ... }: {
+      environment.systemPackages = with pkgs; [ natscli ];
+    };
+  in {
+    server = { pkgs, ... }: {
+      networking.firewall.allowedTCPPorts = [ port ];
+      services.nats = {
+        inherit port;
+        enable = true;
+        settings = {
+          authorization = {
+            users = [{
+              user = username;
+              inherit password;
+            }];
+          };
+        };
+      };
+    };
+
+    client1 = client;
+    client2 = client;
+  };
+
+  testScript = let file = "/tmp/msg";
+  in ''
+    def nats_cmd(*args):
+        return (
+            "nats "
+            "--server=nats://server:${toString port} "
+            "--user=${username} "
+            "--password=${password} "
+            "{}"
+        ).format(" ".join(args))
+
+    start_all()
+    server.wait_for_unit("nats.service")
+
+    client1.fail("test -f ${file}")
+
+    # Subscribe on topic on client1 and echo messages to file.
+    client1.execute("({} | tee ${file} &)".format(nats_cmd("sub", "--raw", "${topic}")))
+
+    # Give client1 some time to subscribe.
+    client1.execute("sleep 2")
+
+    # Publish message on client2.
+    client2.execute(nats_cmd("pub", "${topic}", "hello"))
+
+    # Check if message has been received.
+    client1.succeed("grep -q hello ${file}")
+  '';
+})