feat: fail2ban

hosts/lab/fail2ban.nix

@@ -0,0 +1,61 @@
+{ ... }:
+{
+  services.fail2ban = {
+    enable = true;
+    maxretry = 5;
+    bantime = "1h";
+    bantime-increment = {
+      enable = true;
+      maxtime = "168h";
+      overalljails = true;
+    };
+    ignoreIP = [ "127.0.0.1/8" "::1" ];
+
+    jails = {
+      # SSH jail auto-created by NixOS — just tighten the limits
+      sshd.settings = {
+        maxretry = 3;
+        findtime = "15m";
+      };
+
+      forgejo.settings = {
+        enabled = true;
+        port = "http,https,4201";
+        filter = "forgejo";
+        backend = "systemd";
+        journalmatch = "_SYSTEMD_UNIT=forgejo.service";
+        maxretry = 5;
+        findtime = "10m";
+      };
+
+      caddy-status.settings = {
+        enabled = true;
+        port = "http,https";
+        filter = "caddy-status";
+        backend = "systemd";
+        journalmatch = "_SYSTEMD_UNIT=caddy.service";
+        maxretry = 10;
+        findtime = "10m";
+      };
+    };
+  };
+
+  # Enable Caddy access logging (to journal via stderr)
+  services.caddy.globalConfig = ''
+    servers {
+      logs
+    }
+  '';
+
+  environment.etc."fail2ban/filter.d/forgejo.conf".text = ''
+    [Definition]
+    failregex = ^.*Failed authentication attempt for .* from <HOST>
+    ignoreregex =
+  '';
+
+  environment.etc."fail2ban/filter.d/caddy-status.conf".text = ''
+    [Definition]
+    failregex = ^.*"client_ip":"<HOST>".*"status":\s*(401|403)
+    ignoreregex =
+  '';
+}