From 397d074fa395afdfd02073e81cee5576b742f3b6 Mon Sep 17 00:00:00 2001
From: Kjetil Orbekk <kj@orbekk.com>
Date: Sun, 7 Mar 2021 20:15:14 -0500
Subject: Add nftable based simple firewall module

---
 modules/desktop.nix         |  1 +
 modules/simple-firewall.nix | 65 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 modules/simple-firewall.nix

(limited to 'modules')

diff --git a/modules/desktop.nix b/modules/desktop.nix
index e348d77..8252110 100644
--- a/modules/desktop.nix
+++ b/modules/desktop.nix
@@ -11,6 +11,7 @@ in
 
   config = lib.mkIf cfg.enable {
     orbekk.yubikey.enable = lib.mkDefault true;
+    orbekk.simple-firewall.enable = true;
 
     location.latitude = 40.0;
     location.longitude = -74.0;
diff --git a/modules/simple-firewall.nix b/modules/simple-firewall.nix
new file mode 100644
index 0000000..eda869a
--- /dev/null
+++ b/modules/simple-firewall.nix
@@ -0,0 +1,65 @@
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.orbekk.simple-firewall;
+in
+{
+  options = {
+    orbekk.simple-firewall = {
+      enable = lib.mkEnableOption "Enable nftables firewall";
+
+      allowedUDPPorts = lib.mkOption {
+        type = lib.types.listOf lib.types.port;
+        default = [];
+        description = "List of TCP ports to allow";
+      };
+
+      allowedTCPPorts = lib.mkOption {
+        type = lib.types.listOf lib.types.port;
+        default = [];
+        description = "List of TCP ports to allow";
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    networking.firewall.enable = lib.mkForce false;
+
+    networking.nftables.enable = true;
+
+    networking.nftables.ruleset =
+      let
+        csvPorts = ports: lib.concatStringsSep "," (map toString ports);
+      in ''
+    table inet filter {
+      chain allowed_ports {
+        ${lib.optionalString (cfg.allowedTCPPorts != []) ''
+        tcp dport {${csvPorts cfg.allowedTCPPorts}} counter accept
+        ''}
+        ${lib.optionalString (cfg.allowedUDPPorts != []) ''
+        udp dport {${csvPorts cfg.allowedUDPPorts}} counter accept
+        ''}
+      }
+
+      chain input {
+        type filter hook input priority 0
+
+        iif lo accept
+
+        ct state {established, related} accept
+
+        ip protocol icmp limit rate 4/second counter accept
+        ip6 nexthdr ipv6-icmp limit rate 4/second counter accept
+
+        jump allowed_ports
+
+        counter drop
+      }
+
+      chain output {
+        type filter hook output priority 0
+        counter accept
+      }
+    }
+    '';
+  };
+}
-- 
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