polkit.nix

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

with lib;

let

  cfg = config.security.polkit;

in

{

  options = {

    security.polkit.enable = mkOption {
      type = types.bool;
      default = true;
      description = "Whether to enable PolKit.";
    };

    security.polkit.extraConfig = mkOption {
      type = types.lines;
      default = "";
      example =
        ''
          /* Log authorization checks. */
          polkit.addRule(function(action, subject) {
            polkit.log("user " +  subject.user + " is attempting action " + action.id + " from PID " + subject.pid);
          });

          /* Allow any local user to do anything (dangerous!). */
          polkit.addRule(function(action, subject) {
            if (subject.local) return "yes";
          });
        '';
      description =
        ''
          Any polkit rules to be added to config (in JavaScript ;-). See:
          http://www.freedesktop.org/software/polkit/docs/latest/polkit.8.html#polkit-rules
        '';
    };

    security.polkit.adminIdentities = mkOption {
      type = types.listOf types.str;
      default = [ "unix-user:0" "unix-group:wheel" ];
      example = [ "unix-user:alice" "unix-group:admin" ];
      description =
        ''
          Specifies which users are considered “administrators”, for those
          actions that require the user to authenticate as an
          administrator (i.e. have an <literal>auth_admin</literal>
          value).  By default, this is the <literal>root</literal>
          user and all users in the <literal>wheel</literal> group.
        '';
    };

  };


  config = mkIf cfg.enable {

    environment.systemPackages = [ pkgs.polkit.bin pkgs.polkit.out ];

    systemd.packages = [ pkgs.polkit.out ];

    systemd.services.polkit.restartTriggers = [ config.system.path ];
    systemd.services.polkit.stopIfChanged = false;

    # The polkit daemon reads action/rule files
    environment.pathsToLink = [ "/share/polkit-1" ];

    # PolKit rules for NixOS.
    environment.etc."polkit-1/rules.d/10-nixos.rules".text =
      ''
        polkit.addAdminRule(function(action, subject) {
          return [${concatStringsSep ", " (map (i: "\"${i}\"") cfg.adminIdentities)}];
        });

        ${cfg.extraConfig}
      ''; #TODO: validation on compilation (at least against typos)

    services.dbus.packages = [ pkgs.polkit.out ];

    security.pam.services.polkit-1 = {};

    security.wrappers = {
      pkexec.source = "${pkgs.polkit.bin}/bin/pkexec";
      "polkit-agent-helper-1".source = "${pkgs.polkit.out}/lib/polkit-1/polkit-agent-helper-1";
    };

    system.activationScripts.polkit =
      ''
        # Probably no more needed, clean up
        rm -rf /var/lib/{polkit-1,PolicyKit}
      '';

    users.extraUsers.polkituser = {
      description = "PolKit daemon";
      uid = config.ids.uids.polkituser;
    };

  };

}