nixos/mjolnir: init

nixos/modules/module-list.nix

@@ -477,6 +477,7 @@
   ./services/mail/roundcube.nix
   ./services/mail/sympa.nix
   ./services/mail/nullmailer.nix
+  ./services/matrix/mjolnir.nix
   ./services/matrix/pantalaimon.nix
   ./services/misc/airsonic.nix
   ./services/misc/ankisyncd.nix

nixos/modules/services/matrix/mjolnir.nix

@@ -0,0 +1,239 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+let
+  cfg = config.services.mjolnir;
+
+  yamlConfig = {
+    inherit (cfg) dataPath managementRoom protectedRooms;
+
+    accessToken = "@ACCESS_TOKEN@"; # will be replaced in "generateConfig"
+    homeserverUrl =
+      if cfg.pantalaimon.enable then
+        "http://${cfg.pantalaimon.options.listenAddress}:${toString cfg.pantalaimon.options.listenPort}"
+      else
+        cfg.homeserverUrl;
+
+    pantalaimon = {
+      inherit (cfg.pantalaimon) username;
+
+      use = cfg.pantalaimon.enable;
+      password = "@PANTALAIMON_PASSWORD@"; # will be replaced in "generateConfig"
+    };
+  };
+
+  moduleConfigFile = pkgs.writeText "module-config.yaml" (
+    generators.toYAML { } (filterAttrs (_: v: v != null)
+      (fold recursiveUpdate { } [ yamlConfig cfg.settings ])));
+
+  # these config files will be merged one after the other to build the final config
+  configFiles = [
+    "${pkgs.mjolnir}/share/mjolnir/config/default.yaml"
+    moduleConfigFile
+  ];
+
+  # this will generate the default.yaml file with all configFiles as inputs and
+  # replace all secret strings using replace-secret
+  generateConfig = pkgs.writeShellScript "mjolnir-generate-config" (
+    let
+      yqEvalStr = concatImapStringsSep " * " (pos: _: "select(fileIndex == ${toString (pos - 1)})") configFiles;
+      yqEvalArgs = concatStringsSep " " configFiles;
+    in
+    ''
+      set -euo pipefail
+
+      umask 077
+
+      # mjolnir will try to load a config from "./config/default.yaml" in the working directory
+      # -> let's place the generated config there
+      mkdir -p ${cfg.dataPath}/config
+
+      # merge all config files into one, overriding settings of the previous one with the next config
+      # e.g. "eval-all 'select(fileIndex == 0) * select(fileIndex == 1)' filea.yaml fileb.yaml" will merge filea.yaml with fileb.yaml
+      ${pkgs.yq-go}/bin/yq eval-all -P '${yqEvalStr}' ${yqEvalArgs} > ${cfg.dataPath}/config/default.yaml
+
+      ${optionalString (cfg.accessTokenFile != null) ''
+        ${pkgs.replace-secret}/bin/replace-secret '@ACCESS_TOKEN@' '${cfg.accessTokenFile}' ${cfg.dataPath}/config/default.yaml
+      ''}
+      ${optionalString (cfg.pantalaimon.passwordFile != null) ''
+        ${pkgs.replace-secret}/bin/replace-secret '@PANTALAIMON_PASSWORD@' '${cfg.pantalaimon.passwordFile}' ${cfg.dataPath}/config/default.yaml
+      ''}
+    ''
+  );
+in
+{
+  options.services.mjolnir = {
+    enable = mkEnableOption "Mjolnir, a moderation tool for Matrix";
+
+    homeserverUrl = mkOption {
+      type = types.str;
+      default = "https://matrix.org";
+      description = ''
+        Where the homeserver is located (client-server URL).
+
+        If <literal>pantalaimon.enable</literal> is <literal>true</literal>, this option will become the homeserver to which <literal>pantalaimon</literal> connects.
+        The listen address of <literal>pantalaimon</literal> will then become the <literal>homeserverUrl</literal> of <literal>mjolnir</literal>.
+      '';
+    };
+
+    accessTokenFile = mkOption {
+      type = with types; nullOr path;
+      default = null;
+      description = ''
+        File containing the matrix access token for the <literal>mjolnir</literal> user.
+      '';
+    };
+
+    pantalaimon = mkOption {
+      description = ''
+        <literal>pantalaimon</literal> options (enables E2E Encryption support).
+
+        This will create a <literal>pantalaimon</literal> instance with the name "mjolnir".
+      '';
+      default = { };
+      type = types.submodule {
+        options = {
+          enable = mkEnableOption ''
+            If true, accessToken is ignored and the username/password below will be
+            used instead. The access token of the bot will be stored in the dataPath.
+          '';
+
+          username = mkOption {
+            type = types.str;
+            description = "The username to login with.";
+          };
+
+          passwordFile = mkOption {
+            type = with types; nullOr path;
+            default = null;
+            description = ''
+              File containing the matrix password for the <literal>mjolnir</literal> user.
+            '';
+          };
+
+          options = mkOption {
+            type = types.submodule (import ./pantalaimon-options.nix);
+            default = { };
+            description = ''
+              passthrough additional options to the <literal>pantalaimon</literal> service.
+            '';
+          };
+        };
+      };
+    };
+
+    dataPath = mkOption {
+      type = types.path;
+      default = "/var/lib/mjolnir";
+      description = ''
+        The directory the bot should store various bits of information in.
+      '';
+    };
+
+    managementRoom = mkOption {
+      type = types.str;
+      default = "#moderators:example.org";
+      description = ''
+        The room ID where people can use the bot. The bot has no access controls, so
+        anyone in this room can use the bot - secure your room!
+        This should be a room alias or room ID - not a matrix.to URL.
+        Note: <literal>mjolnir</literal> is fairly verbose - expect a lot of messages from it.
+      '';
+    };
+
+    protectedRooms = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      example = literalExample ''
+        [
+          "https://matrix.to/#/#yourroom:example.org"
+          "https://matrix.to/#/#anotherroom:example.org"
+        ]
+      '';
+      description = ''
+        A list of rooms to protect (matrix.to URLs).
+      '';
+    };
+
+    settings = mkOption {
+      default = { };
+      type = (pkgs.formats.yaml { }).type;
+      example = literalExample ''
+        {
+          autojoinOnlyIfManager = true;
+          automaticallyRedactForReasons = [ "spam" "advertising" ];
+        }
+      '';
+      description = ''
+        Additional settings (see <link xlink:href="https://github.com/matrix-org/mjolnir/blob/main/config/default.yaml">mjolnir default config</link> for available settings). These settings will override settings made by the module config.
+      '';
+    };
+  };
+
+  config = mkIf config.services.mjolnir.enable {
+    assertions = [
+      {
+        assertion = !(cfg.pantalaimon.enable && cfg.pantalaimon.passwordFile == null);
+        message = "Specify pantalaimon.passwordFile";
+      }
+      {
+        assertion = !(cfg.pantalaimon.enable && cfg.accessTokenFile != null);
+        message = "Do not specify accessTokenFile when using pantalaimon";
+      }
+      {
+        assertion = !(!cfg.pantalaimon.enable && cfg.accessTokenFile == null);
+        message = "Specify accessTokenFile when not using pantalaimon";
+      }
+    ];
+
+    services.pantalaimon-headless.instances."mjolnir" = mkIf cfg.pantalaimon.enable
+      {
+        homeserver = cfg.homeserverUrl;
+      } // cfg.pantalaimon.options;
+
+    systemd.services.mjolnir = {
+      description = "mjolnir - a moderation tool for Matrix";
+      wants = [ "network-online.target" ] ++ optionals (cfg.pantalaimon.enable) [ "pantalaimon-mjolnir.service" ];
+      after = [ "network-online.target" ] ++ optionals (cfg.pantalaimon.enable) [ "pantalaimon-mjolnir.service" ];
+      wantedBy = [ "multi-user.target" ];
+
+      serviceConfig = {
+        ExecStart = ''${pkgs.mjolnir}/bin/mjolnir'';
+        ExecStartPre = [ generateConfig ];
+        WorkingDirectory = cfg.dataPath;
+        StateDirectory = "mjolnir";
+        StateDirectoryMode = "0700";
+        ProtectSystem = "strict";
+        ProtectHome = true;
+        PrivateTmp = true;
+        NoNewPrivileges = true;
+        PrivateDevices = true;
+        User = "mjolnir";
+        Restart = "on-failure";
+
+        /* TODO: wait for #102397 to be resolved. Then load secrets from $CREDENTIALS_DIRECTORY+"/NAME"
+        DynamicUser = true;
+        LoadCredential = [] ++
+          optionals (cfg.accessTokenFile != null) [
+            "access_token:${cfg.accessTokenFile}"
+          ] ++
+          optionals (cfg.pantalaimon.passwordFile != null) [
+            "pantalaimon_password:${cfg.pantalaimon.passwordFile}"
+          ];
+        */
+      };
+    };
+
+    users = {
+      users.mjolnir = {
+        group = "mjolnir";
+        isSystemUser = true;
+      };
+      groups.mjolnir = { };
+    };
+  };
+
+  meta = {
+    maintainers = with maintainers; [ jojosch ];
+  };
+}