nixpkgs/nixos/modules/services/home-automation/zwave-js.nix

{config, pkgs, lib, ...}:
let
  cfg = config.services.zwave-js;
  mergedConfigFile = "/run/zwave-js/config.json";
  settingsFormat = pkgs.formats.json {};
in {
  options.services.zwave-js = {
    enable = lib.mkEnableOption "the zwave-js server on boot";

    package = lib.mkPackageOption pkgs "zwave-js-server" { };

    port = lib.mkOption {
      type = lib.types.port;
      default = 3000;
      description = ''
        Port for the server to listen on.
      '';
    };

    serialPort = lib.mkOption {
      type = lib.types.path;
      description = ''
        Serial port device path for Z-Wave controller.
      '';
      example = "/dev/ttyUSB0";
    };

    secretsConfigFile = lib.mkOption {
      type = lib.types.path;
      description = ''
        JSON file containing secret keys. A dummy example:

        ```
        {
          "securityKeys": {
            "S0_Legacy": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
            "S2_Unauthenticated": "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
            "S2_Authenticated": "CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC",
            "S2_AccessControl": "DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD"
          }
        }
        ```

        See
        <https://zwave-js.github.io/node-zwave-js/#/getting-started/security-s2>
        for details. This file will be merged with the module-generated config
        file (taking precedence).

        Z-Wave keys can be generated with:

          {command}`< /dev/urandom tr -dc A-F0-9 | head -c32 ;echo`


        ::: {.warning}
        A file in the nix store should not be used since it will be readable to
        all users.
        :::
      '';
      example = "/secrets/zwave-js-keys.json";
    };

    settings = lib.mkOption {
      type = lib.types.submodule {
        freeformType = settingsFormat.type;

        options = {
          storage = {
            cacheDir = lib.mkOption {
              type = lib.types.path;
              default = "/var/cache/zwave-js";
              readOnly = true;
              description = "Cache directory";
            };
          };
        };
      };
      default = {};
      description = ''
        Configuration settings for the generated config
        file.
      '';
    };

    extraFlags = lib.mkOption {
      type = with lib.types; listOf str;
      default = [ ];
      example = [ "--mock-driver" ];
      description = ''
        Extra flags to pass to command
      '';
    };
  };

  config = lib.mkIf cfg.enable {
    systemd.services.zwave-js = let
      configFile = settingsFormat.generate "zwave-js-config.json" cfg.settings;
    in {
      wantedBy = [ "multi-user.target" ];
      after = [ "network.target" ];
      description = "Z-Wave JS Server";
      serviceConfig = {
        ExecStartPre = ''
          /bin/sh -c "${pkgs.jq}/bin/jq -s '.[0] * .[1]' ${configFile} ${cfg.secretsConfigFile} > ${mergedConfigFile}"
        '';
        ExecStart = lib.concatStringsSep " " [
          "${cfg.package}/bin/zwave-server"
          "--config ${mergedConfigFile}"
          "--port ${toString cfg.port}"
          cfg.serialPort
          (lib.escapeShellArgs cfg.extraFlags)
        ];
        Restart = "on-failure";
        User = "zwave-js";
        SupplementaryGroups = [ "dialout" ];
        CacheDirectory = "zwave-js";
        RuntimeDirectory = "zwave-js";

        # Hardening
        CapabilityBoundingSet = "";
        DeviceAllow = [cfg.serialPort];
        DevicePolicy = "closed";
        DynamicUser = true;
        LockPersonality = true;
        MemoryDenyWriteExecute = false;
        NoNewPrivileges = true;
        PrivateUsers = true;
        PrivateTmp = true;
        ProtectClock = true;
        ProtectControlGroups = true;
        ProtectHome = true;
        ProtectHostname = true;
        ProtectKernelLogs = true;
        ProtectKernelModules = true;
        RemoveIPC = true;
        RestrictNamespaces = true;
        RestrictRealtime = true;
        RestrictSUIDSGID = true;
        SystemCallArchitectures = "native";
        SystemCallFilter = [
          "@system-service @pkey"
          "~@privileged @resources"
        ];
        UMask = "0077";
      };
    };
  };

  meta.maintainers = with lib.maintainers; [ graham33 ];
}