mailserver: Add spam filter

modules/mailserver.nix

@@ -84,6 +84,9 @@ in
         "spammer@example.com"
       ];
     };
+    spam = {
+      enable = (lib.mkEnableOption "spam filtering") // { default = true; };
+    };
   };
 
   config = lib.mkIf cfg.enable {
@@ -357,5 +360,55 @@ in
     networking.resolvconf.extraConfig = ''
       name_servers='127.0.0.53'
     '';
+
+    # rspamd
+    sops.secrets.rspamd-worker-controller = lib.mkIf cfg.spam.enable {
+      owner = config.users.users.rspamd.name;
+      sopsFile = ../machines + "/${config.networking.hostName}/secrets.yaml";
+    };
+
+    services.rspamd = {
+      enable = cfg.spam.enable;
+      postfix.enable = true;
+      workers = {
+        normal = {
+          includes = [ "$CONFDIR/worker-normal.inc" ];
+          bindSockets = lib.singleton {
+            socket = "/run/rspamd/rspamd.sock";
+            mode = "0660";
+            owner = "${config.services.rspamd.user}";
+            group = "${config.services.rspamd.group}";
+          };
+        };
+        controller = {
+          includes = [ "$CONFDIR/worker-controller.inc" ];
+          bindSockets = [ "127.0.0.1:11334" ] ++ lib.optional config.sbruder.wireguard.home.enable "${config.sbruder.wireguard.home.address}:11334";
+        };
+      };
+      locals = {
+        "dkim_signing.conf".text = ''
+          enabled = false;
+        '';
+        "logging.inc".text = ''
+          # starts at info, drops to notice once started up
+          level = "silent";
+        '';
+        "milter_headers.conf".text = ''
+          extended_spam_headers = true;
+        '';
+        "redis.conf".text = ''
+          servers = "127.0.0.1:${toString config.services.redis.servers.rspamd.port}"
+        '';
+        "worker-controller.inc".source = config.sops.secrets.rspamd-worker-controller.path; # includes password
+      };
+    };
+
+    services.redis = lib.mkIf cfg.spam.enable {
+      vmOverCommit = true;
+      servers.rspamd = {
+        enable = true;
+        port = 6379;
+      };
+    };
   };
 }