nixos-config/modules/wireguard/home.nix

{ lib, config, pkgs, ... }:
let
  serverHostName = "vueko";
  serverPort = 51820;
  subnet = "10.80.0.0/24";
  peers = {
    hitagi = {
      address = "10.80.0.5";
      publicKey = "t7hpd2yZupAKHxYerHtXnlPRUjV1aGbrrzjYakKdOwE=";
    };
    vueko = {
      address = "10.80.0.6";
      publicKey = "JbOfL4FxPCzJOjI8AGklPHY2FniCXq0QwOa08gjSyns=";
    };
    fuuko = {
      address = "10.80.0.7";
      publicKey = "VXic8mhaJBSl6yFkx0Cu6JI8tqqjjM3UbW7x+05pV0M=";
    };
    mayushii = {
      address = "10.80.0.9";
      publicKey = "nnLdgywXmDg8HWH6I0G28Z2zb4OmmyFDpnvvEBzKJTg=";
    };
    renge = {
      address = "10.80.0.11";
      publicKey = "RlLs/uiWb9qaBU2iDgRag7Q+FFaR7oHI3yOPLZPKgmA=";
    };
    nunotaba = {
      address = "10.80.0.4";
      publicKey = "LscDAJR0IjOzNuwX3geYgcvxyvaNhAOc/ojgvGyunT8=";
    };
    okarin = {
      address = "10.80.0.10";
      publicKey = "KjDdTOVZ9RadDrNjJ11BWsY8SNBmDbuNoKm72wh9uCk=";
    };
    shinobu = {
      address = "10.80.0.12";
      publicKey = "ErLWueo4ikYH/mKHr3axyoAVZh+Bdh1NQBet42aD0kk=";
    };
  };

  cfg = config.sbruder.wireguard.home;
  enableServer = config.networking.hostName == serverHostName;
in
{
  options = {
    sbruder.wireguard.home = {
      enable = lib.mkEnableOption "WireGuard tunnel wg-home";
      address = lib.mkOption {
        type = lib.types.str;
        visible = false;
        readOnly = true;
      };
      subnet = lib.mkOption {
        type = lib.types.str;
        visible = false;
        readOnly = true;
      };
    };
  };

  config = lib.mkIf cfg.enable {
    sops.secrets.wg-home-private-key = {
      owner = config.users.users.systemd-network.name;
      sopsFile = ./../../machines + "/${config.networking.hostName}/secrets.yaml";
    };

    sbruder.wireguard.home = {
      address = peers."${config.networking.hostName}".address;
      inherit subnet;
    };

    systemd.network = {
      enable = true;
      netdevs = {
        wg-home = {
          netdevConfig = {
            Kind = "wireguard";
            Name = "wg-home";
          };
          wireguardConfig = {
            PrivateKeyFile = config.sops.secrets.wg-home-private-key.path;
          } // (lib.optionalAttrs enableServer {
            ListenPort = serverPort;
          });
          wireguardPeers =
            if enableServer
            then
              map
                (peerConfig: with peerConfig; {
                  wireguardPeerConfig = {
                    PublicKey = publicKey;
                    AllowedIPs = [ "${address}/32" ];
                  };
                })
                (lib.attrValues
                  (lib.filterAttrs
                    (n: v: n != config.networking.hostName)
                    peers))
            else [
              {
                wireguardPeerConfig = {
                  PublicKey = peers."${serverHostName}".publicKey;
                  AllowedIPs = [ subnet ];
                  #Endpoint = "${serverHostName}.sbruder.de:${toString serverPort}"; # not possible because sadly not all devices have IPv6 connectivity
                  Endpoint = "168.119.176.53:${toString serverPort}";
                  PersistentKeepalive = 25;
                };
              }
            ];
        };
      };
      networks = {
        wg-home = {
          name = "wg-home";
          address = lib.singleton "${config.sbruder.wireguard.home.address}/24";
          networkConfig = lib.optionalAttrs enableServer {
            IPForward = "ipv4";
          };
        };
      };
    };

    networking.firewall = {
      trustedInterfaces = [ "wg-home" ];
      allowedUDPPorts = lib.optionals enableServer [
        serverPort
        53
      ];
    };

    services.bind = lib.mkIf enableServer {
      enable = true;
      zones = lib.singleton {
        name = "vpn.sbruder.de";
        master = true;
        file =
          let
            # !!! very hacky
            hexStringToInt = hex: (builtins.fromTOML "int = 0x${hex}").int;

            peerRecords = lib.concatStrings
              (lib.mapAttrsToList
                (peer: peerConfig: ''
                  ${peer} IN A ${peerConfig.address}
                '')
                peers);

            peerRecordsHash = builtins.hashString "sha256" peerRecords;
            serial = hexStringToInt (lib.substring 0 8 peerRecordsHash);
          in
          pkgs.writeText "vpn.sbruder.de.zone" (''
            $TTL 3600
            @ IN SOA ${serverHostName}.sbruder.de. hostmaster.sbruder.de. ${toString serial} 28800 3600 604800 3600
            @ IN NS ${serverHostName}.sbruder.de.
          '' + peerRecords);
      };
    };
  };
}