feat(server): add wireguard gateway with LAN access for VPN clients

system/machines/server/modules/wireguard/default.nix

@@ -0,0 +1,106 @@
+{ pkgs, lib, config, ... }:
+
+with lib;
+let
+  cfg = config.modules.system.wireguard;
+in
+{
+  options.modules.system.wireguard = {
+    enable = mkEnableOption "WireGuard VPN";
+
+    address = mkOption {
+      type = types.str;
+      default = "10.8.0.1/24";
+      description = "WireGuard interface address with CIDR";
+    };
+
+    subnet = mkOption {
+      type = types.str;
+      default = "10.8.0.0/24";
+      description = "WireGuard subnet used for peer allocations";
+    };
+
+    listenPort = mkOption {
+      type = types.port;
+      default = 51820;
+      description = "WireGuard UDP listen port";
+    };
+
+    privateKeyFile = mkOption {
+      type = types.str;
+      default = "/var/lib/wireguard/server.key";
+      description = "Path to WireGuard server private key";
+    };
+
+    peers = mkOption {
+      type = types.listOf (types.submodule ({ ... }: {
+        options = {
+          publicKey = mkOption {
+            type = types.str;
+            description = "Peer public key";
+          };
+
+          allowedIPs = mkOption {
+            type = types.listOf types.str;
+            description = "Allowed IPs for peer, usually a single /32";
+          };
+
+          presharedKeyFile = mkOption {
+            type = types.nullOr types.str;
+            default = null;
+            description = "Optional preshared key file";
+          };
+
+          persistentKeepalive = mkOption {
+            type = types.nullOr types.int;
+            default = 25;
+            description = "Persistent keepalive interval seconds";
+          };
+        };
+      }));
+      default = [ ];
+      description = "WireGuard peers";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    networking.firewall.allowedUDPPorts = [ cfg.listenPort ];
+    networking.nat.internalInterfaces = mkAfter [ "wg0" ];
+
+    systemd.tmpfiles.rules = [
+      "d /var/lib/wireguard 0700 root root -"
+    ];
+
+    systemd.services.wireguard-generate-key = {
+      description = "Generate WireGuard server key if missing";
+      before = [ "wireguard-wg0.service" ];
+      wantedBy = [ "wireguard-wg0.service" ];
+      serviceConfig = {
+        Type = "oneshot";
+      };
+      path = with pkgs; [ wireguard-tools coreutils ];
+      script = ''
+        set -euo pipefail
+
+        if [ ! -s "${cfg.privateKeyFile}" ]; then
+          umask 077
+          wg genkey | tee "${cfg.privateKeyFile}" | wg pubkey > /var/lib/wireguard/server.pub
+        elif [ ! -s /var/lib/wireguard/server.pub ]; then
+          umask 077
+          wg pubkey < "${cfg.privateKeyFile}" > /var/lib/wireguard/server.pub
+        fi
+      '';
+    };
+
+    networking.wireguard.interfaces.wg0 = {
+      ips = [ cfg.address ];
+      listenPort = cfg.listenPort;
+      privateKeyFile = cfg.privateKeyFile;
+      peers = map (peer: {
+        inherit (peer) publicKey allowedIPs;
+        presharedKeyFile = peer.presharedKeyFile;
+        persistentKeepalive = peer.persistentKeepalive;
+      }) cfg.peers;
+    };
+  };
+}

system/machines/server/system.nix

@@ -19,6 +19,10 @@
     frigate.enable = true;
     immich.enable = true;
     webdav.enable = false;
+    wireguard = {
+      enable = true;
+      peers = [ ];
+    };
     # bitcoin = {
     #   enable = true;
     #   electrum.enable = true;
@@ -172,7 +176,7 @@
       cache-size = 1000;
 
       # Camera network DHCP (isolated - no gateway = no internet)
-      interface = "enp2s0f1";
+      interface = [ "enp2s0f1" "wg0" ];
       bind-interfaces = true;
       dhcp-range = "192.168.1.100,192.168.1.200,24h";