nix-config/modules/nixos/services/ssh-server/default.nix

# An SSH server, using 'mosh'
{ config, lib, ... }:
let
  cfg = config.my.services.ssh-server;
in
{
  options.my.services.ssh-server = {
    enable = lib.mkEnableOption "SSH Server using 'mosh'";
  };

  config = lib.mkIf cfg.enable {
    services.openssh = {
      # Enable the OpenSSH daemon.
      enable = true;

      settings = {
        # Be more secure
        PermitRootLogin = "no";
        PasswordAuthentication = false;
      };
    };

    # Persist SSH keys
    my.system.persist.files =
      let
        pubAndPrivKey = key: [ key.path "${key.path}.pub" ];
      in
      lib.concatMap pubAndPrivKey config.services.openssh.hostKeys;

    # Opens the relevant UDP ports.
    programs.mosh.enable = true;
  };
}