Add WireGuard tunnels as firewall zone members

router.wireguard.<name> configures tunnels through networkd: road warrior (listening, dual-stack), site-to-site (no transfer network) and provider dial-out with masquerade. A tunnel has a zone like a LAN, so inter-zone rules apply; management, DNS and internet are opt-in. Peers' allowedIPs become routes (destination-based routing; default-route tunnels are rejected). Tunnels have a kill switch (default on): forwarded packets for their allowedIPs are dropped if they would leave via an uplink, before the established-accept so flows that used the tunnel are cut too. Private keys stay outside the Nix store and are passed to the unprivileged systemd-networkd with LoadCredential, so key files can be root-only. Assertions cover CIDR/key/endpoint formats, duplicate allowedIPs, overlaps with LAN subnets, port and device clashes, and rule destinations inside tunnel networks. A five-VM `wireguard` check covers road warrior, site-to-site, the provider tunnel with an IPv6 transfer net, zone rules and the kill switch. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
2026-10-27 19:56:45 +01:00
parent 6015ee2e6d
commit 30ab1a0ed6
11 changed files with 975 additions and 26 deletions
@@ -0,0 +1,71 @@
+{ config, lib, ... }:
+let
+  cfg = config.router;
+
+  # systemd-networkd runs unprivileged and could not read root-only key files.
+  # LoadCredential= makes systemd read them as root and hand networkd a copy
+  # in its credentials directory, so the files can stay 0600 root.
+  credDir = "/run/credentials/systemd-networkd.service";
+  keyCred = name: "wg-${name}-key";
+  pskCred = name: peer: "wg-${name}-${peer}-psk";
+  credentials = lib.concatLists (
+    lib.mapAttrsToList (
+      name: wg:
+      [ "${keyCred name}:${toString wg.privateKeyFile}" ]
+      ++ lib.concatLists (
+        lib.mapAttrsToList (
+          peer: p:
+          lib.optional (p.presharedKeyFile != null) "${pskCred name peer}:${toString p.presharedKeyFile}"
+        ) wg.peers
+      )
+    ) cfg.wireguard
+  );
+in
+{
+  config = lib.mkIf (cfg.enable && cfg.wireguard != { }) {
+    systemd.network.netdevs = lib.mapAttrs' (
+      name: wg:
+      lib.nameValuePair "30-wg-${name}" {
+        netdevConfig = {
+          Kind = "wireguard";
+          Name = wg.interface;
+        }
+        // lib.optionalAttrs (wg.mtu != null) { MTUBytes = wg.mtu; };
+        wireguardConfig = {
+          PrivateKeyFile = "${credDir}/${keyCred name}";
+        }
+        // lib.optionalAttrs (wg.listenPort != null) { ListenPort = wg.listenPort; };
+        wireguardPeers = lib.mapAttrsToList (
+          peer: p:
+          {
+            PublicKey = p.publicKey;
+            AllowedIPs = p.allowedIPs;
+          }
+          // lib.optionalAttrs (p.endpoint != null) { Endpoint = p.endpoint; }
+          // lib.optionalAttrs (p.persistentKeepalive != null) {
+            PersistentKeepalive = p.persistentKeepalive;
+          }
+          // lib.optionalAttrs (p.presharedKeyFile != null) {
+            PresharedKeyFile = "${credDir}/${pskCred name peer}";
+          }
+        ) wg.peers;
+      }
+    ) cfg.wireguard;
+
+    systemd.services.systemd-networkd.serviceConfig.LoadCredential = credentials;
+
+    systemd.network.networks = lib.mapAttrs' (
+      name: wg:
+      lib.nameValuePair "30-wg-${name}" {
+        matchConfig.Name = wg.interface;
+        address = wg.addresses;
+        networkConfig = {
+          ConfigureWithoutCarrier = true;
+          IPv6AcceptRA = false;
+        };
+        # Cryptokey routing: a peer's allowedIPs are the destinations sent into the tunnel.
+        routes = lib.concatMap (p: map (ip: { Destination = ip; }) p.allowedIPs) (lib.attrValues wg.peers);
+      }
+    ) cfg.wireguard;
+  };
+}