nixos_flake_config/fuji/wireguard.nix

{ config
, pkgs
, lib
, ...
}:
{
  sops.secrets = {
    "wg_privkey" = {
      sopsFile = ./secrets/wg_privkey.yaml;
    };

    "wg_preshared/nixy" = {
      sopsFile = ../common/secrets/wg_preshared.yaml;
    };

    "wg_privkey_proton" = {
      sopsFile = ./secrets/wg_privkey_proton.yaml;
    };

    "wg_endpoint_proton" = {
      sopsFile = ./secrets/wg_privkey_proton.yaml;
    };
  };

  # Personal mesh: dials into the magpie hub (10.100.0.0/24)
  networking.wireguard.interfaces = {
    wg0 = {
      ips = [ "10.100.0.6/24" ];
      privateKeyFile = config.sops.secrets."wg_privkey".path;
      peers = [
        {
          publicKey = builtins.readFile ../magpie/wg_pubkey;
          presharedKeyFile = config.sops.secrets."wg_preshared/nixy".path;
          allowedIPs = [ "10.100.0.0/24" ];
          endpoint = "5.75.229.224:51820";
          persistentKeepalive = 25;
        }
      ];
    };
  };

  systemd = {
    services = {
      # ProtonVPN split tunnel: proton_wg lives inside the `wg` network
      # namespace; anything that should egress over Proton is launched
      # with `ip netns exec wg ...`.
      "netns@" = {
        description = "%I network namespace";
        before = [ "network.target" ];
        serviceConfig = {
          Type = "oneshot";
          RemainAfterExit = true;
          ExecStart = "${pkgs.iproute2}/bin/ip netns add %I";
          ExecStop = "${pkgs.iproute2}/bin/ip netns del %I";
        };
      };

      "wg_proton" = {
        description = "wg network interface";
        bindsTo = [ "netns@wg.service" ];
        requires = [ "network-online.target" ];
        wants = [ "dnscrypt-proxy_proton.service" ];
        after = [ "netns@wg.service" ];
        before = [ "dnscrypt-proxy_proton.service" ];
        serviceConfig = {
          Type = "oneshot";
          RemainAfterExit = true;
          ExecStart = pkgs.writers.writeBash "wg-up" ''
            set -e
            ENDPOINT_IP=$(${pkgs.coreutils-full}/bin/cat "${config.sops.secrets."wg_endpoint_proton".path}")
            ${pkgs.iproute2}/bin/ip link add proton_wg type wireguard
            ${pkgs.iproute2}/bin/ip link set proton_wg netns wg
            ${pkgs.iproute2}/bin/ip -n wg address add 10.2.0.2/32 dev proton_wg
            ${pkgs.iproute2}/bin/ip netns exec wg \
              ${pkgs.wireguard-tools}/bin/wg set "proton_wg" private-key "${
                config.sops.secrets."wg_privkey_proton".path
              }"
            ${pkgs.iproute2}/bin/ip netns exec wg \
              ${pkgs.wireguard-tools}/bin/wg set "proton_wg" peer "${lib.fileContents ../common/wg_pubkey_proton}" \
                endpoint "$ENDPOINT_IP:51820" \
                persistent-keepalive "25" \
                allowed-ips "0.0.0.0/0"
            ${pkgs.iproute2}/bin/ip -n wg link set lo up
            ${pkgs.iproute2}/bin/ip -n wg link set proton_wg up
            ${pkgs.iproute2}/bin/ip -n wg route add default dev proton_wg
          '';
          ExecStop = pkgs.writers.writeBash "wg-down" ''
            ${pkgs.iproute2}/bin/ip -n wg route del default dev proton_wg
            ${pkgs.iproute2}/bin/ip -n wg link del proton_wg
          '';
        };
      };

      "dnscrypt-proxy_proton" = {
        description = "DNSCrypt-proxy client proton";
        wants = [
          "network-online.target"
          "nss-lookup.target"
        ];
        before = [ "nss-lookup.target" ];
        after = [ "wg_proton.service" ];
        partOf = [ "wg_proton.service" ];
        serviceConfig = {
          AmbientCapabilities = "CAP_NET_BIND_SERVICE";
          CacheDirectory = "dnscrypt-proxy";
          DynamicUser = true;
          ExecStart = "${pkgs.dnscrypt-proxy}/bin/dnscrypt-proxy -config ${config.services.dnscrypt-proxy.configFile}";
          LockPersonality = true;
          LogsDirectory = "dnscrypt-proxy";
          MemoryDenyWriteExecute = true;
          NetworkNamespacePath = "/var/run/netns/wg";
          NonBlocking = true;
          NoNewPrivileges = true;
          PrivateDevices = true;
          ProtectClock = true;
          ProtectControlGroups = true;
          ProtectHome = true;
          ProtectHostname = true;
          ProtectKernelLogs = true;
          ProtectKernelModules = true;
          ProtectKernelTunables = true;
          ProtectSystem = "strict";
          Restart = "always";
          RestrictAddressFamilies = [
            "AF_INET"
            "AF_INET6"
          ];
          RestrictNamespaces = true;
          RestrictRealtime = true;
          RuntimeDirectory = "dnscrypt-proxy";
          StateDirectory = "dnscrypt-proxy";
          SystemCallArchitectures = "native";
          SystemCallFilter = [
            "@system-service"
            "@chown"
            "~@aio"
            "~@keyring"
            "~@memlock"
            "~@setuid"
            "~@timer"
          ];
        };
      };
    };

    # Don't bring wg0 up at boot
    targets."wireguard-wg0".wantedBy = lib.mkForce [ ];
  };
}