nixos-config/nixos/system/server/initssh.nix

{ config, lib, pkgs, ... }:

with lib;

let

  cfg = config.configuration.init-ssh;

in
{

  options.configuration.init-ssh = {

    enable = mkOption {
      default = "disable";
      type = with types; enum [ "disable" "prepare" "enabled" ];
    };

    kernelModules = mkOption {
      type = with types; listOf str;
      description =
        "lspci -v will tell you which kernel module is used for the ethernet interface";
    };

    port = mkOption {
      default = 2222;
      type = with types; int;
    };

    authorizedKeys = mkOption {
      type = with types; listOf str;
      default = config.users.users.root.openssh.authorizedKeys.keys
        ++ (map (keyFile: lib.fileContents keyFile)
        config.users.users.root.openssh.authorizedKeys.keyFiles);
    };
    hostKey = mkOption {
      default = "/etc/ssh/ssh_host_ed25519_key";
      type = with types; path;
      description = ''
        To generate keys, use ssh-keygen(1):
        # ssh-keygen -t rsa -N "" -f /etc/secrets/initrd/ssh_host_rsa_key
        # ssh-keygen -t ed25519 -N "" -f /etc/secrets/initrd/ssh_host_ed25519_key
      '';
    };

  };

  config = mkMerge [

    (mkIf (cfg.enable != "disable") {
      services.tor = {
        enable = true;
        client.enable = true;
        relay.onionServices.bootup.map = [{ port = 22; }];
      };
    })

    (mkIf (cfg.enable == "enabled") {

      # tor setup
      boot.initrd.secrets = {
        "/etc/tor/onion/bootup" = /var/lib/tor/onion/bootup;
      };

      boot.initrd.extraUtilsCommands = ''
        copy_bin_and_libs ${pkgs.tor}/bin/tor
      '';

      boot.initrd.network.postCommands =
        let
          torRc = (pkgs.writeText "tor.rc" ''
            DataDirectory /etc/tor
            SOCKSPort 127.0.0.1:9050 IsolateDestAddr
            SOCKSPort 127.0.0.1:9063
            HiddenServiceDir /etc/tor/onion/bootup
            HiddenServicePort ${toString cfg.port} 127.0.0.1:${toString cfg.port}
          '');
        in
        ''
          echo "tor: preparing onion folder"
          # have to do this otherwise tor does not want to start
          chmod -R 700 /etc/tor

          echo "make sure localhost is up"
          ip a a 127.0.0.1/8 dev lo
          # ifconfig lo up
          ip link set lo up

          echo "tor: starting tor"
          tor -f ${torRc} --verify-config
          tor -f ${torRc} &
        '';

      # ssh setup
      # todo add the ssh host fingerprint to your trusted stuff
      # todo set ssh host key here
      boot.initrd.network.enable = true;
      boot.initrd.network.ssh = {
        enable = true;
        authorizedKeys = cfg.authorizedKeys;
        port = cfg.port;
        hostKeys = [ cfg.hostKey ];
      };
      boot.initrd.availableKernelModules = cfg.kernelModules;
    })
  ];
}