nixpkgs/nixos/modules/services/security/physlock.nix

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

with lib;

let
  cfg = config.services.physlock;
in

{

  ###### interface

  options = {

    services.physlock = {

      enable = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Whether to enable the <command>physlock</command> screen locking mechanism.

          Enable this and then run <command>systemctl start physlock</command>
          to securely lock the screen.

          This will switch to a new virtual terminal, turn off console
          switching and disable SysRq mechanism (when
          <option>services.physlock.disableSysRq</option> is set)
          until the root or user password is given.
        '';
      };

      disableSysRq = mkOption {
        type = types.bool;
        default = true;
        description = ''
          Whether to disable SysRq when locked with physlock.
        '';
      };

      lockOn = {

        suspend = mkOption {
          type = types.bool;
          default = true;
          description = ''
            Whether to lock screen with physlock just before suspend.
          '';
        };

        hibernate = mkOption {
          type = types.bool;
          default = true;
          description = ''
            Whether to lock screen with physlock just before hibernate.
          '';
        };

        extraTargets = mkOption {
          type = types.listOf types.str;
          default = [];
          example = [ "display-manager.service" ];
          description = ''
            Other targets to lock the screen just before.

            Useful if you want to e.g. both autologin to X11 so that
            your <filename>~/.xsession</filename> gets executed and
            still to have the screen locked so that the system can be
            booted relatively unattended.
          '';
        };

      };

    };

  };


  ###### implementation

  config = mkIf cfg.enable {

    # for physlock -l and physlock -L
    environment.systemPackages = [ pkgs.physlock ];

    systemd.services."physlock" = {
      enable = true;
      description = "Physlock";
      wantedBy = optional cfg.lockOn.suspend   "suspend.target"
              ++ optional cfg.lockOn.hibernate "hibernate.target"
              ++ cfg.lockOn.extraTargets;
      before   = optional cfg.lockOn.suspend   "systemd-suspend.service"
              ++ optional cfg.lockOn.hibernate "systemd-hibernate.service"
              ++ cfg.lockOn.extraTargets;
      serviceConfig.Type = "forking";
      script = ''
        ${pkgs.physlock}/bin/physlock -d${optionalString cfg.disableSysRq "s"}
      '';
    };

  };

}