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<chapter id="privileges">
  <title>Privileges and Permissions</title>

  <para>When a user is logged into Cockpit, they are logged into a normal session
    that has exactly the same privileges as if they logged in via SSH or on
    the console.</para>

  <para>In some cases Cockpit will try to escalate the privileges of the user
    using <ulink url="http://www.freedesktop.org/wiki/Software/polkit/">Policy Kit</ulink>
    or <ulink url="http://www.sudo.ws/">sudo</ulink>. If the user is able to escalate
    privileges from the command line, then Cockpit will use that same capability to
    perform certain privileged tasks.</para>

  <para>Cockpit can use the user's login password internally to escalate privileges
    in these situations. By selecting the
    <emphasis>Reuse my password for privileged tasks</emphasis> option on the login screen
    the login password will be cached internally and passed to <emphasis>Policy Kit</emphasis>
    when requested in order to escalate privileges.</para>

  <para>To test out whether Cockpit can escalate privileges, you can run these commands
    from a the <link linkend="feature-terminal">terminal built into Cockpit</link>.</para>

<programlisting>
$ sudo cockpit-bridge
...
$ pkexec cockpit-bridge
...
</programlisting>

  <para>If either of these commands succeed without prompting for a password,
    Cockpit will be able to start a privileged copy of the
    <filename>cockpit-bridge</filename> and use it to perform privileged tasks
    when necessary.</para>

  <para>Usually a user needs to be in the <code>wheel</code> Unix user group for the
    user to be able to escalate privileges in this way. However both Policy Kit and
    sudo may be configured to use other criteria.</para>

  <section id="privileges-polkit">
    <title>Customizing Polkit Privileges</title>

    <para>Services like <ulink url="http://www.freedesktop.org/wiki/Software/systemd/">systemd</ulink>
      and <ulink url="https://wiki.gnome.org/Projects/NetworkManager">NetworkManager</ulink> use
      <ulink url="http://www.freedesktop.org/wiki/Software/polkit/">Polkit</ulink> to
      validate and escalate privileges. It is possible to customize these rules with files
      in <filename>/etc/polkit-1/rules.d</filename>.</para>

    <para>Polkit rules files are
      <ulink url="https://www.freedesktop.org/software/polkit/docs/latest/polkit.8.html">javascript with specific methods and objects</ulink>. For example, placing the following polkit rule to
      <filename>/etc/polkit-1.rules.d/10-operators.rule</filename> allows all users in the
      <code>operators</code> group to start, stop, restart and otherwise manage systemd services:</para>

<programlisting>
polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.systemd1.manage-units") {
        if (subject.isInGroup("operators")) {
            return polkit.Result.YES;
        }
    }
});
</programlisting>

    <para>In order to allow a certain group to perform any administrative action you could add
      a rule like this:</para>

<programlisting>
polkit.addAdminRule(function(action, subject) {
    return ["unix-group:operators"];
});
</programlisting>

  </section>
</chapter>
