path: root/docs/man/polkit.xml

<?xml version="1.0"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
               "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" [
<!ENTITY version SYSTEM "../version.xml">
]>
<refentry id="polkit.8" xmlns:xi="http://www.w3.org/2003/XInclude">
  <refentryinfo>
    <title>polkit</title>
    <date>January 2009</date>
    <productname>polkit</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>polkit</refentrytitle>
    <manvolnum>8</manvolnum>
    <refmiscinfo class="version"></refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>polkit</refname>
    <refpurpose>Authorization Manager</refpurpose>
  </refnamediv>

  <refsect1 id="polkit-overview"><title>OVERVIEW</title>
    <para>
      polkit provides an authorization API intended to be used by
      privileged programs (<quote>MECHANISMS</quote>) offering service
      to unprivileged programs (<quote>SUBJECTS</quote>) often through
      some form of inter-process communication mechanism. In this
      scenario, the mechanism typically treats the subject as
      untrusted. For every request from a subject, the mechanism needs
      to determine if the request is authorized or if it should refuse
      to service the subject. Using the polkit APIs, a mechanism can
      offload this decision to a trusted party: The polkit authority.
    </para>

    <para>
      The polkit authority is implemented as an system daemon,
      <link linkend="polkitd.8"><citerefentry><refentrytitle>polkitd</refentrytitle><manvolnum>8</manvolnum></citerefentry></link>,
      which itself has little privilege as it is running as the
      <emphasis>polkitd</emphasis> system user. Mechanisms, subjects
      and authentication agents communicate with the authority using
      the system message bus.
    </para>

    <para>
      In addition to acting as an authority, polkit allows users to
      obtain temporary authorization through authenticating either an
      administrative user or the owner of the session the client
      belongs to. This is useful for scenarios where a mechanism needs
      to verify that the operator of the system really is the user or
      really is an administrative user.
    </para>

  </refsect1>

  <refsect1 id="polkit-system-architecture"><title>SYSTEM ARCHITECTURE</title>
    <para>
      The system architecture of polkit is comprised of the
      <emphasis>Authority</emphasis> (implemented as a service on the
      system message bus) and an <emphasis>Authentication
      Agent</emphasis> per user session (provided and started by the
      user's graphical environment). <emphasis>Actions</emphasis> are
      defined by applications. Vendors, sites and system
      administrators can control authorization policy through
      <emphasis>Authorization Rules</emphasis>.
    </para>
    <mediaobject id="polkit-architecture">
      <imageobject>
        <imagedata fileref="polkit-architecture.png" format="PNG"/>
      </imageobject>
      <textobject>
        <programlisting><![CDATA[
 +-------------------+
 |   Authentication  |
 |       Agent       |
 +-------------------+
 | libpolkit-agent-1 |
 +-------------------+
        ^                                  +---------+
        |                                  | Subject |
        +--------------+                   +---------+
                       |                        ^
                       |                        |
User Session           |                        |
=======================|========================|=============
System Context         |                        |
                       |                        |
                       |                    +---+
                       V                    |
                     /------------\         |
                     | System Bus |         |
                     \------------/         |
                       ^        ^           V
                       |        |      +---------------------+
        +--------------+        |      |      Mechanism      |
        |                       |      +---------------------+
        V                       +----> | libpolkit-gobject-1 |
+------------------+                   +---------------------+
|    polkitd(8)    |
+------------------+
| org.freedesktop. |
|    PolicyKit1    |<---------+
+------------------+          |
          ^                   |
          |            +--------------------------------------+
          |            | /usr/share/polkit-1/actions/*.policy |
          |            +--------------------------------------+
          |
   +--------------------------------------+
   | /etc/polkit-1/rules.d/*.rules        |
   | /usr/share/polkit-1/rules.d/*.rules  |
   +--------------------------------------+
]]></programlisting>
      </textobject>
    </mediaobject>
    <para>
      For convenience, the <literal>libpolkit-gobject-1</literal>
      library wraps the polkit D-Bus API and is usable from any C/C++
      program as well as higher-level languages <ulink
      url="https://live.gnome.org/GObjectIntrospection">GObjectIntrospection</ulink>
      support such as Javascript and Python.  A mechanism can also use
      the D-Bus API or the
      <link linkend="pkcheck.1"><citerefentry><refentrytitle>pkcheck</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>
      command to check authorizations. The
      <literal>libpolkit-agent-1</literal> library provides an
      abstraction of the native authentication system, e.g.
      <citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
      and also facilities registration and communication with the
      polkit D-Bus service.
    </para>

    <para>
      See the <ulink
      url="http://www.freedesktop.org/software/polkit/docs/latest/">developer
      documentation</ulink> for more information about writing polkit
      applications.
    </para>
  </refsect1>

  <refsect1 id="polkit-authentication-agents"><title>AUTHENTICATION AGENTS</title>
    <para>
      An authentication agent is used to make the user of a session
      prove that the user of the session really is the user (by
      authenticating as the user) or an administrative user (by
      authenticating as a administrator). In order to integrate well
      with the rest of the user session (e.g. match the look and
      feel), authentication agents are meant to be provided by the
      user session that the user uses. For example, an authentication
      agent may look like this:
    </para>
    <mediaobject id="polkit-authentication-agent-example">
      <imageobject>
        <imagedata fileref="polkit-authentication-agent-example.png" format="PNG"/>
      </imageobject>
      <textobject>
        <programlisting><![CDATA[
+----------------------------------------------------------+
|                                                          |
|  [Icon]  Authentication required                         |
|                                                          |
|          Authentication is required to format INTEL      |
|          SSDSA2MH080G1GC (/dev/sda)                      |
|                                                          |
|          Administrator                                   |
|                                                          |
|          Password: [__________________________________]  |
|                                                          |
| [Cancel]                                  [Authenticate] |
+----------------------------------------------------------+
]]></programlisting>
      </textobject>
    </mediaobject>
    <para>
      If the system is configured without a <emphasis>root</emphasis>
      account it may prompt for a specific user designated as the
      administrative user:
    </para>
    <mediaobject id="polkit-authentication-agent-example-wheel">
      <imageobject>
        <imagedata fileref="polkit-authentication-agent-example-wheel.png" format="PNG"/>
      </imageobject>
      <textobject>
        <programlisting><![CDATA[
+----------------------------------------------------------+
|                                                          |
|  [Icon]  Authentication required                         |
|                                                          |
|          Authentication is required to format INTEL      |
|          SSDSA2MH080G1GC (/dev/sda)                      |
|                                                          |
|          [Icon] David Zeuthen                            |
|                                                          |
|          Password: [__________________________________]  |
|                                                          |
| [Cancel]                                  [Authenticate] |
+----------------------------------------------------------+
]]></programlisting>
      </textobject>
    </mediaobject>
    <para>
      Applications that do not run under a desktop environment (for
      example, if launched from a
      <citerefentry><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>
      login) may not have have an authentication agent associated with
      them. Such applications may use the <link
      linkend="PolkitAgentTextListener-struct">PolkitAgentTextListener</link>
      type or the
      <link linkend="pkttyagent.1"><citerefentry><refentrytitle>pkttyagent</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>
      helper so the user can authenticate using a textual interface.
    </para>
  </refsect1>

  <refsect1 id="polkit-declaring-actions"><title>DECLARING ACTIONS</title>
    <para>
      A mechanism need to declare a set of <emphasis>actions</emphasis> in
      order to use polkit. Actions correspond to operations that
      clients can request the mechanism to carry out and are defined
      in XML files that the mechanism installs into the <filename
      class='directory'>/usr/share/polkit-1/actions</filename>
      directory.
    </para>

    <para>
      polkit actions are namespaced and can only contain the
      characters <literal>[A-Z][a-z][0-9].-</literal> e.g. ASCII,
      digits, period and hyphen. Each XML file can contain more than
      one action but all actions need to be in the same namespace and
      the file needs to be named after the namespace and have the
      extension <filename class='extension'>.policy</filename>.
    </para>

    <para>
      The XML file must have the following doctype declaration
    </para>
    <programlisting><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE policyconfig PUBLIC "-//freedesktop//DTD polkit Policy Configuration 1.0//EN"
"http://www.freedesktop.org/software/polkit/policyconfig-1.dtd">
]]></programlisting>
    <para>
      The <emphasis>policyconfig</emphasis> element must be present
      exactly once. Elements that can be used
      inside <emphasis>policyconfig</emphasis> includes:
    </para>
    <variablelist>
      <varlistentry>
        <term><emphasis>vendor</emphasis></term>
        <listitem>
          <para>
            The name of the project or vendor that is supplying the
            actions in the XML document. Optional.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>vendor_url</emphasis></term>
        <listitem>
          <para>
            A URL to the project or vendor that is supplying the
            actions in the XML document.  Optional.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>icon_name</emphasis></term>
        <listitem>
          <para>
            An icon representing the project or vendor that is
            supplying the actions in the XML document. The icon name
            must adhere to the <ulink
            url="http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html">Freedesktop.org
            Icon Naming Specification</ulink>. Optional.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>action</emphasis></term>
        <listitem>
          <para>
            Declares an action. The action name is specified using the
            <literal>id</literal> attribute and can only contain the
            characters <literal>[A-Z][a-z][0-9].-</literal>
            e.g. ASCII, digits, period and hyphen.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
    <para>
      Elements that can be used inside <emphasis>action</emphasis> include:
    </para>
    <variablelist>
      <varlistentry>
        <term><emphasis>description</emphasis></term>
        <listitem>
          <para>
            A human readable description of the action,
            e.g. <quote>Install unsigned software</quote>.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>message</emphasis></term>
        <listitem>
          <para>
            A human readable message displayed to the user when asking
            for credentials when authentication is needed,
            e.g. <quote>Installing unsigned software requires
            authentication</quote>.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>defaults</emphasis></term>
        <listitem>
          <para>
            This element is used to specify implicit authorizations
            for clients. Elements that can be used inside
            <emphasis>defaults</emphasis> include:
          </para>
          <variablelist>
            <varlistentry>
              <term><emphasis>allow_any</emphasis></term>
              <listitem><para>Implicit authorizations that apply to
              any client. Optional.</para></listitem>
            </varlistentry>
            <varlistentry>
              <term><emphasis>allow_inactive</emphasis></term>
              <listitem><para>Implicit authorizations that apply to
              clients in inactive sessions on local
              consoles. Optional.</para></listitem>
            </varlistentry>
            <varlistentry>
              <term><emphasis>allow_active</emphasis></term>
              <listitem><para>Implicit authorizations that apply to
              clients in active sessions on local
              consoles. Optional.</para></listitem>
            </varlistentry>
          </variablelist>
          <para>
            Each of
            the <emphasis>allow_any</emphasis>, <emphasis>allow_inactive</emphasis>
            and <emphasis>allow_active</emphasis> elements can contain
            the following values:
          </para>
          <variablelist>
            <varlistentry>
              <term><literal>no</literal></term>
              <listitem><para>Not authorized.</para></listitem>
            </varlistentry>
            <varlistentry>
              <term><literal>yes</literal></term>
              <listitem><para>Authorized.</para></listitem>
            </varlistentry>
            <varlistentry>
              <term><literal>auth_self</literal></term>
              <listitem><para>Authentication by the owner of the
              session that the client originates from is
              required.</para></listitem>
            </varlistentry>
            <varlistentry>
              <term><literal>auth_admin</literal></term>
              <listitem><para>Authentication by an administrative user
              is required.</para></listitem>
            </varlistentry>
            <varlistentry>
              <term><literal>auth_self_keep</literal></term>
              <listitem><para>Like <literal>auth_self</literal> but
              the authorization is kept for a brief
              period.</para></listitem>
            </varlistentry>
            <varlistentry>
              <term><literal>auth_admin_keep</literal></term>
              <listitem><para>Like <literal>auth_admin</literal> but the authorization is kept for a brief period.</para></listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>annotate</emphasis></term>
        <listitem>
          <para>
            Used for annotating an action with a key/value pair. The
            key is specified using the the <literal>key</literal>
            attribute and the value is specified using the
            <literal>value</literal> attribute. This element may
            appear zero or more times. See below for known
            annotations.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>vendor</emphasis></term>
        <listitem>
          <para>
            Used for overriding the vendor on a per-action
            basis. Optional.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>vendor_url</emphasis></term>
        <listitem>
          <para>
            Used for overriding the vendor URL on a per-action
            basis. Optional.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><emphasis>icon_name</emphasis></term>
        <listitem>
          <para>
            Used for overriding the icon name on a per-action
            basis. Optional.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
    <para>
      For localization, <emphasis>description</emphasis> and
      <emphasis>message</emphasis> elements may occur multiple times
      with different <literal>xml:lang</literal> attributes.
    </para>
    <para>
      To list installed polkit actions, use the
      <link linkend="pkaction.1"><citerefentry><refentrytitle>pkaction</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>
      command.
    </para>

    <refsect2>
      <title>Known annotations</title>
      <para>
        The <literal>org.freedesktop.policykit.exec.path</literal>
        annotation is used by the <command>pkexec</command> program
        shipped with polkit - see the
        <link linkend="pkexec.1"><citerefentry><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>
        man page for details.
      </para>
      <para>
        The <literal>org.freedesktop.policykit.imply</literal>
        annotation (its value is a string containing a space separated
        list of action identifiers) can be used to define
        <emphasis>meta actions</emphasis>. The way it works is that if
        a subject is authorized for an action with this annotation,
        then it is also authorized for any action specified by the
        annotation. A typical use of this annotation is when defining
        an UI shell with a single lock button that should unlock
        multiple actions from distinct mechanisms.
      </para>
      <para>
        The <literal>org.freedesktop.policykit.owner</literal>
        annotation can be used to define a set of users who can query
        whether a client is authorized to perform this action.  If
        this annotation is not specified then only root can query
        whether a client running as a different user is authorized for
        an action.  The value of this annotation is a string
        containing a space separated list of <link
        linkend="PolkitIdentity-struct">PolkitIdentity</link> entries,
        for example <literal>"unix-user:42
        unix-user:colord"</literal>.  A typical use of this annotation
        is for a daemon process that runs as a system user rather than
        root.
      </para>
    </refsect2>
  </refsect1>

  <refsect1 id="polkit-rules"><title>AUTHORIZATION RULES</title>
    <para>
      <command>polkitd</command> reads
      <filename class='extension'>.rules</filename> files from the
      <filename class='directory'>/etc/polkit-1/rules.d</filename> and
      <filename class='directory'>/usr/share/polkit-1/rules.d</filename>
      directories by sorting the files in lexical order based on the
      basename on each file (and if there's a tie, files in
      <filename class='directory'>/etc</filename>
      are processed before files in
      <filename class='directory'>/usr</filename>).
      For example, for the following four
      files, the order is
    </para>
    <itemizedlist mark='opencircle' spacing='compact'>
      <listitem><para><filename>/etc/polkit-1/rules.d/10-auth.rules</filename></para></listitem>
      <listitem><para><filename>/usr/share/polkit-1/rules.d/10-auth.rules</filename></para></listitem>
      <listitem><para><filename>/etc/polkit-1/rules.d/15-auth.rules</filename></para></listitem>
      <listitem><para><filename>/usr/share/polkit-1/rules.d/20-auth.rules</filename></para></listitem>
    </itemizedlist>
    <para>
      Both directories are monitored so if a rules file is changed,
      added or removed, existing rules are purged and all files are
      read and processed again.  Rules files are written in the
      <ulink url="http://en.wikipedia.org/wiki/JavaScript">JavaScript</ulink>
      programming language and interface with <command>polkitd</command>
      through the global
      <literal>polkit</literal> object (of type <type>Polkit</type>).
    </para>

    <refsect2 id="polkit-rules-polkit">
      <title>The <type>Polkit</type> type</title>

      <para>
        The following methods are available on the <literal>polkit</literal> object:
      </para>

      <funcsynopsis>
        <funcprototype>
          <?dbhtml funcsynopsis-style='ansi'?>
          <funcdef>void <function>addRule</function></funcdef>
          <paramdef>string <function>function</function>(<parameter>action</parameter>, <parameter>subject</parameter>) {...}</paramdef>
        </funcprototype>
      </funcsynopsis>

      <funcsynopsis>
        <funcprototype>
          <?dbhtml funcsynopsis-style='ansi'?>
          <funcdef>void <function>addAdminRule</function></funcdef>
          <paramdef>string[] <function>function</function>(<parameter>action</parameter>, <parameter>subject</parameter>) {...}</paramdef>
        </funcprototype>
      </funcsynopsis>

      <funcsynopsis>
        <funcprototype>
          <?dbhtml funcsynopsis-style='ansi'?>
          <funcdef>void <function>log</function></funcdef>
          <paramdef>string <parameter>message</parameter></paramdef>
        </funcprototype>
      </funcsynopsis>

      <funcsynopsis>
        <funcprototype>
          <?dbhtml funcsynopsis-style='ansi'?>
          <funcdef>string <function>spawn</function></funcdef>
          <paramdef>string[] <parameter>argv</parameter></paramdef>
        </funcprototype>
      </funcsynopsis>

      <para>
        The <function>addRule()</function> method is used for adding a
        function that may be called whenever an authorization check for
        <parameter>action</parameter> and <parameter>subject</parameter>
        is performed. Functions are
        called in the order they have been added until one of the
        functions returns a value. Hence, to add an authorization rule
        that is processed before other rules, put it in a file in
        <filename class='directory'>/etc/polkit-1/rules.d</filename>
        with a name that sorts before other rules files, for example
        <filename>00-early-checks.rules</filename>. Each function should
        return one of the values <literal>"no"</literal>,
        <literal>"yes"</literal>, <literal>"auth_self"</literal>,
        <literal>"auth_self_keep"</literal>,
        <literal>"auth_admin"</literal>,
        <literal>"auth_admin_keep"</literal> as defined above. If the
        function returns <constant>null</constant>,
        <constant>undefined</constant> or does not return a value at
        all, the next function is tried.
      </para>

      <para>
        The <function>addAdminRule()</function> method is used for
        adding a function may be called whenever administrator
        authentication is required. The function is used to specify what
        identies may be used for administrator authentication for the
        authorization check identified by <parameter>action</parameter>
        and <parameter>subject</parameter>. Functions added are called in
        the order they have been added until one of the functions
        returns a value. Each function should return an array of strings
        where each string is of the form
        <literal>"unix-group:&lt;group&gt;"</literal>,
        <literal>"unix-netgroup:&lt;netgroup&gt;"</literal> or
        <literal>"unix-user:&lt;user&gt;"</literal>.  If the function
        returns <constant>null</constant>,
        <constant>undefined</constant> or does not return a value at
        all, the next function is tried.
      </para>

      <para>
        There is no guarantee that a function registered with
        <function>addRule()</function> or
        <function>addAdminRule()</function> is ever called - for example
        an early rules file could register a function that always return
        a value, hence ensuring that functions added later are never
        called.
      </para>

      <para>
        If user-provided code takes a long time to execute an exception
        will be thrown which normally results in the function being
        terminated (the current limit is 15 seconds). This is used to
        catch runaway scripts.
      </para>

      <para>
        The <function>spawn()</function> method spawns an external
        helper identified by the argument vector
        <parameter>argv</parameter> and waits for it to terminate. If an
        error occurs or the helper doesn't exit normally with exit code
        0, an exception is thrown. If the helper does not exit within 10
        seconds it is killed. Otherwise, the program's
        <emphasis>standard output</emphasis> is returned as a string.
        The <function>spawn()</function> method should be used sparingly
        as helpers may take a very long or indeterminate amount of time
        to complete and no other authorization check can be handled
        while the helper is running. Note that the spawned programs
        will run as the unprivileged <emphasis>polkitd</emphasis> system
        user.
      </para>

      <para>
        The <function>log()</function> method writes the given
        <parameter>message</parameter> to the system logger prefixed
        with the JavaScript filename and line number. Log entries are
        emitted using the <constant>LOG_AUTHPRIV</constant> flag meaning
        that the log entries usually ends up in the file
        <filename>/var/log/secure</filename>. The
        <function>log()</function> method is usually only used when
        debugging rules. The <type>Action</type> and
        <type>Subject</type> types has suitable
        <function>toString()</function> methods defined for easy
        logging, for example,
      </para>
      <programlisting><![CDATA[
polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.policykit.exec") {
        polkit.log("action=" + action);
        polkit.log("subject=" + subject);
    }
});
]]></programlisting>
      <para>
        will produce the following when the user runs 'pkexec -u bateman bash -i' from a shell:
      </para>
      <programlisting><![CDATA[
May 24 14:28:50 thinkpad polkitd[32217]: /etc/polkit-1/rules.d/10-test.rules:3: action=[Action id='org.freedesktop.policykit.exec' command_line='/usr/bin/bash -i' program='/usr/bin/bash' user='bateman' user.gecos='Patrick Bateman' user.display='Patrick Bateman (bateman)']
May 24 14:28:50 thinkpad polkitd[32217]: /etc/polkit-1/rules.d/10-test.rules:4: subject=[Subject pid=1352 user='davidz' groups=davidz,wheel, seat='seat0' session='1' local=true active=true]
]]></programlisting>

    </refsect2>

    <refsect2 id="polkit-rules-actions">
      <title>The <type>Action</type> type</title>

      <para>
        The <parameter>action</parameter> parameter passed to user
        functions is an object with information about the action
        being checked. It is of type <type>Action</type> and has
        the following attribute:
      </para>

      <variablelist id="polkit-js-action-attributes">
        <varlistentry>
          <term><type>string</type> id</term>
          <listitem>
            <para>
              The action identifier, for example
              <emphasis>org.freedesktop.policykit.exec</emphasis>.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>
        The following methods are available on the <type>Action</type> type:
      </para>

      <funcsynopsis>
        <funcprototype>
          <?dbhtml funcsynopsis-style='ansi'?>
          <funcdef>string <function>lookup</function></funcdef>
          <paramdef>string <parameter>key</parameter></paramdef>
        </funcprototype>
      </funcsynopsis>

      <para>
        The <function>lookup()</function> method is used to lookup the
        polkit variables passed from the mechanism. For example, the
        <link linkend="pkexec.1"><citerefentry><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>
        mechanism sets the variable <parameter>program</parameter>
        which can be obtained in Javascript using the expression
        <literal>action.lookup("program")</literal>. If there is
        no value for the given <parameter>key</parameter>,
        then <constant>undefined</constant> is returned.
      </para>
      <para>
        Consult the documentation for each mechanism for what
        variables are available for each action.
      </para>
    </refsect2>

    <refsect2 id="polkit-rules-subject">
      <title>The <type>Subject</type> type</title>

      <para>
        The <parameter>subject</parameter> parameter passed to user
        functions is an object with information about the process
        being checked. It is of type <type>Subject</type> and has the
        following attributes
      </para>

      <variablelist id="polkit-js-subject-attributes">
        <varlistentry>
          <term><type>int</type> pid</term>
          <listitem>
            <para>
              The process id.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><type>string</type> user</term>
          <listitem>
            <para>
              The user name.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><type>string[]</type> groups</term>
          <listitem>
            <para>
              Array of groups that <parameter>user</parameter> user belongs to.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><type>string</type> seat</term>
          <listitem>
            <para>
              The seat that the subject is associated with - blank if not on a local seat.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><type>string</type> session</term>
          <listitem>
            <para>
              The session that the subject is associated with.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><type>boolean</type> local</term>
          <listitem>
            <para>
              Set to <constant>true</constant> only if seat is local.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><type>boolean</type> active</term>
          <listitem>
            <para>
              Set to <constant>true</constant> only if the session is active.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>
        The following methods are available on the <type>Subject</type> type:
      </para>

      <funcsynopsis>
        <funcprototype>
          <?dbhtml funcsynopsis-style='ansi'?>
          <funcdef>boolean <function>isInGroup</function></funcdef>
          <paramdef>string <parameter>groupName</parameter></paramdef>
        </funcprototype>
      </funcsynopsis>

      <funcsynopsis>
        <funcprototype>
          <?dbhtml funcsynopsis-style='ansi'?>
          <funcdef>boolean <function>isInNetGroup</function></funcdef>
          <paramdef>string <parameter>netGroupName</parameter></paramdef>
        </funcprototype>
      </funcsynopsis>

      <para>
        The <function>isInGroup()</function> method can be used to
        check if the subject is in a given group and
        <function>isInNetGroup()</function> can be used to check if
        the subject is in a given netgroup.
      </para>
    </refsect2>

    <refsect2 id="polkit-rules-examples">
      <title>Authorization Rules Examples</title>

      <para>
        Allow all users in the <literal>admin</literal> group to
        perform user administration without changing policy for other
        users:
      </para>
      <programlisting><![CDATA[
polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.accounts.user-administration" &&
        subject.isInGroup("admin")) {
        return "yes";
    }
});
]]></programlisting>

      <para>
        Define administrative users to be the users in the <literal>wheel</literal> group:
      </para>
      <programlisting><![CDATA[
polkit.addAdminRule(function(action, subject) {
    return ["unix-group:wheel"];
});
]]></programlisting>

      <para>
        Forbid users in group <literal>children</literal> to change
        hostname configuration (that is, any action with an identifier
        starting with <literal>org.freedesktop.hostname1.</literal>)
        and allow anyone else to do it after authenticating as
        themselves:
      </para>
      <programlisting><![CDATA[
polkit.addRule(function(action, subject) {
    if (action.id.indexOf("org.freedesktop.hostname1.") == 0) {
        if (subject.isInGroup("children")) {
            return "no";
        } else {
            return "auth_self_keep";
        }
    }
});
]]></programlisting>

      <para>
        Run an external helper to determine if the current user may reboot the system:
      </para>
      <programlisting><![CDATA[
polkit.addRule(function(action, subject) {
    if (action.id.indexOf("org.freedesktop.login1.reboot") == 0) {
        try {
            // user-may-reboot exits with succeess (exit code 0)
            // only if the passed username is authorized
            polkit.spawn(["/opt/company/bin/user-may-reboot",
                          subject.user]);
            return "yes";
        } catch (error) {
            // Nope, but do allow admin authentication
            return "auth_admin";
        }
    }
});
]]></programlisting>

      <para>
        The following example shows how the authorization decision
        can depend on variables passed by the
        <link linkend="pkexec.1"><citerefentry><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>
        mechanism:
      </para>
      <programlisting><![CDATA[
polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.policykit.exec" &&
        action.lookup("program") == "/usr/bin/cat") {
        return "auth_self";
    }
});
]]></programlisting>

      <para>
        The following example shows another use of variables passed from the
        mechanism. In this case, the mechanism is
        <ulink url="http://udisks.freedesktop.org/docs/latest/udisks.8.html">UDisks</ulink>
        which defines a set of
        <ulink url="http://udisks.freedesktop.org/docs/latest/udisks-polkit-actions.html">actions and variables</ulink>
        that is used to match on:
      </para>
      <programlisting><![CDATA[
// Allow users in group 'engineers' to perform any operation on
// some drives without having to authenticate
//
polkit.addRule(function(action, subject) {
    if (action.id.indexOf("org.freedesktop.udisks2.") == 0 &&
        action.lookup("drive.vendor") == "SEAGATE" &&
        action.lookup("drive.model") == "ST3300657SS" &&
        subject.isInGroup("engineers")) {
            return "yes";
        }
    }
});
]]></programlisting>
    </refsect2>
  </refsect1>

  <refsect1 id="polkit-author"><title>AUTHOR</title>
    <para>
      Written by David Zeuthen <email>davidz@redhat.com</email> with
      a lot of help from many others.
    </para>
  </refsect1>

  <refsect1 id="polkit-bugs">
    <title>BUGS</title>
    <para>
      Please send bug reports to either the distribution or the
      polkit-devel mailing list,
      see the link <ulink url="http://lists.freedesktop.org/mailman/listinfo/polkit-devel"/>
      on how to subscribe.
    </para>
  </refsect1>

  <refsect1 id="polkit-see-also">
    <title>SEE ALSO</title>
    <para>
      <link linkend="polkitd.8"><citerefentry><refentrytitle>polkitd</refentrytitle><manvolnum>8</manvolnum></citerefentry></link>,
      <link linkend="pkaction.1"><citerefentry><refentrytitle>pkaction</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>,
      <link linkend="pkcheck.1"><citerefentry><refentrytitle>pkcheck</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>,
      <link linkend="pkexec.1"><citerefentry><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>,
      <link linkend="pkttyagent.1"><citerefentry><refentrytitle>pkttyagent</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>
    </para>
  </refsect1>
</refentry>