dotfiles/systems/ceres/config/wireguard.nix

{
  config,
  flake,
  pkgs,
  ...
}:
let
  inherit (flake.config.services.instances) wireGuard;
  inherit (flake.config.machines.devices) mars ceres;
  service = wireGuard;
  hostIP = "${ceres.wireguard.ip0}/24";
in
{
  networking = {
    firewall = {
      allowedTCPPorts = [
        service.ports.port0
      ];
      allowedUDPPorts = [
        service.ports.port0
        service.ports.port1
      ];
    };

    nat = {
      enable = true;
      enableIPv6 = true;
      externalInterface = "eth0";
      internalInterfaces = [ "wg0" ];
    };

    wg-quick.interfaces = {
      wg0 = {
        address = [
          hostIP
          "fdc9:281f:04d7:9ee9::1/64"
        ];
        listenPort = service.ports.port1;
        privateKeyFile = config.sops.secrets."${service.name}-private".path;
        postUp = ''
          ${pkgs.iptables}/bin/iptables -A FORWARD -i wg0 -j ACCEPT
          ${pkgs.iptables}/bin/iptables -t nat -A POSTROUTING -s ${hostIP} -o eth0 -j MASQUERADE
          ${pkgs.iptables}/bin/ip6tables -A FORWARD -i wg0 -j ACCEPT
          ${pkgs.iptables}/bin/ip6tables -t nat -A POSTROUTING -s fdc9:281f:04d7:9ee9::1/64 -o eth0 -j MASQUERADE
        '';

        # Undo the above
        preDown = ''
          ${pkgs.iptables}/bin/iptables -D FORWARD -i wg0 -j ACCEPT
          ${pkgs.iptables}/bin/iptables -t nat -D POSTROUTING -s ${hostIP} -o eth0 -j MASQUERADE
          ${pkgs.iptables}/bin/ip6tables -D FORWARD -i wg0 -j ACCEPT
          ${pkgs.iptables}/bin/ip6tables -t nat -D POSTROUTING -s fdc9:281f:04d7:9ee9::1/64 -o eth0 -j MASQUERADE
        '';
        peers = [
          {
            publicKey = "9zfRPxkxTLHM9tABC8lIaDMrzdjcF2l1mtG82uqGKUQ=";
            presharedKeyFile = config.sops.secrets."${service.name}-mars-public".path;
            allowedIPs = [
              "${mars.wireguard.ip0}/32"
              "fdc9:281f:04d7:9ee9::2/128"
            ];
          }
        ];
      };
    };
  };

  sops =
    let
      sopsPath = secret: {
        path = "${service.sops.path0}/${service.name}-${secret}-pass";
        owner = "root";
        mode = "600";
      };
    in
    {
      secrets = builtins.listToAttrs (
        map
          (secret: {
            name = "${service.name}-${secret}";
            value = sopsPath secret;
          })
          [
            "private"
            "public"
            "mars-public"
          ]
      );
    };

  boot.kernel.sysctl = {
    "net.ipv4.ip_forward" = 1;
  };
}