caddy-opnsense-blocker/module.nix

{ config, lib, pkgs, ... }:

let
  cfg = config.services.caddy-opnsense-blocker;
  yamlFormat = pkgs.formats.yaml { };
  credentialsDirectory = "/run/credentials/caddy-opnsense-blocker.service";

  credentialSettings = {
    opnsense =
      lib.optionalAttrs (cfg.credentials.opnsenseApiKeyFile != null) {
        api_key_file = "${credentialsDirectory}/opnsense_api_key";
      }
      // lib.optionalAttrs (cfg.credentials.opnsenseApiSecretFile != null) {
        api_secret_file = "${credentialsDirectory}/opnsense_api_secret";
      };
  };

  defaultSettings = {
    server = {
      listen_address = "127.0.0.1:9080";
      read_timeout = "5s";
      write_timeout = "10s";
      shutdown_timeout = "15s";
    };

    storage.path = "/var/lib/${cfg.stateDirectoryName}/caddy-opnsense-blocker.db";
  };

  mergedSettings = lib.recursiveUpdate defaultSettings (lib.recursiveUpdate credentialSettings cfg.settings);
  configFile = yamlFormat.generate "caddy-opnsense-blocker.yaml" mergedSettings;

  loadCredential =
    lib.optional (cfg.credentials.opnsenseApiKeyFile != null)
      "opnsense_api_key:${toString cfg.credentials.opnsenseApiKeyFile}"
    ++ lib.optional (cfg.credentials.opnsenseApiSecretFile != null)
      "opnsense_api_secret:${toString cfg.credentials.opnsenseApiSecretFile}";

  opnsenseEnabled = lib.attrByPath [ "opnsense" "enabled" ] false mergedSettings;
  hasOPNsenseAPIKey =
    cfg.credentials.opnsenseApiKeyFile != null
    || lib.hasAttrByPath [ "opnsense" "api_key" ] cfg.settings
    || lib.hasAttrByPath [ "opnsense" "api_key_file" ] cfg.settings;
  hasOPNsenseAPISecret =
    cfg.credentials.opnsenseApiSecretFile != null
    || lib.hasAttrByPath [ "opnsense" "api_secret" ] cfg.settings
    || lib.hasAttrByPath [ "opnsense" "api_secret_file" ] cfg.settings;
in {
  options.services.caddy-opnsense-blocker = {
    enable = lib.mkEnableOption "caddy-opnsense-blocker";

    package = lib.mkOption {
      type = lib.types.package;
      default = pkgs.callPackage ./package.nix { };
      defaultText = lib.literalExpression "pkgs.callPackage ./package.nix { }";
      description = "Package used to run caddy-opnsense-blocker.";
    };

    user = lib.mkOption {
      type = lib.types.str;
      default = "caddy";
      description = "User account used by the service.";
    };

    group = lib.mkOption {
      type = lib.types.str;
      default = "caddy";
      description = "Primary group used by the service.";
    };

    stateDirectoryName = lib.mkOption {
      type = lib.types.str;
      default = "caddy-opnsense-blocker";
      description = "Systemd state directory name for the service.";
    };

    credentials = {
      opnsenseApiKeyFile = lib.mkOption {
        type = lib.types.nullOr lib.types.path;
        default = null;
        description = "Path to the OPNsense API key loaded through systemd credentials.";
      };

      opnsenseApiSecretFile = lib.mkOption {
        type = lib.types.nullOr lib.types.path;
        default = null;
        description = "Path to the OPNsense API secret loaded through systemd credentials.";
      };
    };

    settings = lib.mkOption {
      type = yamlFormat.type;
      default = { };
      example = {
        opnsense = {
          enabled = true;
          base_url = "https://router.example.test";
          ensure_alias = true;
          alias.name = "blocked-ips";
        };

        profiles.public-web = {
          auto_block = true;
          block_unexpected_posts = true;
          suspicious_path_prefixes = [ "/wp-admin" "/wp-login.php" "/.env" ];
        };

        sources = [
          {
            name = "public-web";
            path = "/var/log/caddy/public-web.json";
            profile = "public-web";
          }
        ];
      };
      description = "YAML-equivalent application settings written to a generated runtime configuration file.";
    };
  };

  config = lib.mkIf cfg.enable {
    assertions = [
      {
        assertion = (cfg.credentials.opnsenseApiKeyFile == null) == (cfg.credentials.opnsenseApiSecretFile == null);
        message = "services.caddy-opnsense-blocker.credentials.opnsenseApiKeyFile and opnsenseApiSecretFile must either both be set or both be null.";
      }
      {
        assertion = !opnsenseEnabled || (hasOPNsenseAPIKey && hasOPNsenseAPISecret);
        message = "services.caddy-opnsense-blocker requires OPNsense credentials when settings.opnsense.enabled = true.";
      }
    ];

    systemd.services.caddy-opnsense-blocker = {
      description = "Caddy OPNsense blocker";
      wantedBy = [ "multi-user.target" ];
      wants = [ "network-online.target" ];
      after = [ "network-online.target" ];

      serviceConfig = {
        Type = "simple";
        User = cfg.user;
        Group = cfg.group;
        StateDirectory = cfg.stateDirectoryName;
        WorkingDirectory = "/var/lib/${cfg.stateDirectoryName}";
        ExecStart = "${cfg.package}/bin/caddy-opnsense-blocker -config ${configFile}";
        LoadCredential = loadCredential;
        Restart = "always";
        RestartSec = "5s";
        NoNewPrivileges = true;
        PrivateTmp = true;
        ProtectSystem = "strict";
        ProtectHome = true;
        ProtectKernelTunables = true;
        ProtectKernelModules = true;
        ProtectControlGroups = true;
        RestrictSUIDSGID = true;
        RestrictAddressFamilies = [ "AF_UNIX" "AF_INET" "AF_INET6" ];
        LockPersonality = true;
        MemoryDenyWriteExecute = true;
        SystemCallArchitectures = "native";
      };
    };
  };
}