path: root/docs/man/polkit.xml

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<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 Framework</refpurpose>
  </refnamediv>

  <refsect1 id="polkit-overview"><title>OVERVIEW</title>
    <para>
      PolicyKit provides an authorization API intended to be used by
      privileged programs (<quote>MECHANISMS</quote>) offering service
      to unprivileged programs (<quote>CLIENTS</quote>) through some
      form of IPC mechanism such as D-Bus or Unix pipes. In this
      scenario, the mechanism typically treats the client as
      untrusted. For every request from a client, the mechanism needs
      to determine if the request is authorized or if it should refuse
      to service the client. Using the PolicyKit API, a mechanism can
      offload this decision to a trusted party: The PolicyKit
      Authority.
    </para>

    <para>
      In addition to acting as an authority, PolicyKit 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 PolicyKit is comprised of
      the <emphasis>Authority</emphasis> (implemented as a service on
      the system message bus) and a
      <emphasis>Authentication Agent</emphasis> per user session
      (provided and started by the user session e.g. GNOME or KDE).
      Additionally, PolicyKit supports a number of extension points –
      specifically, vendors and/or sites can write extensions to
      completely control authorization policy. In a block diagram, the
      architecture looks like this:
    </para>
    <mediaobject id="polkit-architecture">
      <imageobject>
        <imagedata fileref="polkit-architecture.png" format="PNG"/>
      </imageobject>
      <textobject>
        <programlisting><![CDATA[
 +-------------------+
 |   Authentication  |
 |       Agent       |
 +-------------------+
 | libpolkit-agent-1 |
 +-------------------+
        ^                                  +--------+
        |                                  | Client |
        +--------------+                   +--------+
                       |                        ^
                       |                        |
User Session           |                        |
=======================|========================|=============
System Context         |                        |
                       |                        |
                       |                    +---+
                       V                    |
                     /------------\         |
                     | System Bus |         |
                     \------------/         |
                       ^        ^           V
                       |        |      +---------------------+
        +--------------+        |      |      Mechanism      |
        |                       |      +---------------------+
        V                       +----> | libpolkit-gobject-1 |
+------------------+                   +---------------------+
| org.freedesktop. |
|    PolicyKit1    |
+------------------+
|   Backends and   |
|    Extensions    |
+------------------+
]]></programlisting>
      </textobject>
    </mediaobject>
    <para>
      For convenience, the <literal>libpolkit-gobject-1</literal>
      library wraps the PolicyKit D-Bus API using GObject. However, a
      mechanism can also use the D-Bus API or the
      <citerefentry><refentrytitle>pkcheck</refentrytitle><manvolnum>1</manvolnum></citerefentry>
      command to check authorizations.
    </para>

    <para>
      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
      PolicyKit D-Bus service.
    </para>

    <para>
      PolicyKit extensions and authority backends are implemented
      using the
      <literal>libpolkit-backend-1</literal> library.
    </para>

    <para>
      See the
      <ulink url="file:///usr/share/gtk-doc/html/polkit-1/index.html">developer
      documentation</ulink> for more information about using and
      extending PolicyKit.
    </para>

    <para>
      See
      <citerefentry><refentrytitle>pklocalauthority</refentrytitle><manvolnum>8</manvolnum></citerefentry>
      for information about the Local Authority - the default
      authority implementation shipped with PolicyKit.
    </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[
+----------------------------------------------------------+
|                     Authenticate                     [X] |
+----------------------------------------------------------+
|                                                          |
|  [Icon]  Authentication is required to run ATA SMART     |
|          self tests                                      |
|                                                          |
|          An application is attempting to perform an      |
|          action that requires privileges. Authentication |
|          as the super user is required to perform this   |
|          action.                                         |
|                                                          |
|          Password for root: [_________________________]  |
|                                                          |
| [V] Details:                                             |
|  Drive:  ATA INTEL SSDSA2MH08 (045C)                     |
|  Device: /dev/sda                                        |
|  Action: org.fd.devicekit.disks.drive-ata-smart-selftest |
|  Vendor: The DeviceKit Project                           |
|                                                          |
|                                  [Cancel] [Authenticate] |
+----------------------------------------------------------+
]]></programlisting>
      </textobject>
    </mediaobject>
    <para>
      If the system is configured without a <emphasis>root</emphasis>
      account it may allow you to select the administrative user who
      is authenticating:
    </para>
    <mediaobject id="polkit-authentication-agent-example-wheel">
      <imageobject>
        <imagedata fileref="polkit-authentication-agent-example-wheel.png" format="PNG"/>
      </imageobject>
      <textobject>
        <programlisting><![CDATA[
+----------------------------------------------------------+
|                     Authenticate                     [X] |
+----------------------------------------------------------+
|                                                          |
|  [Icon]  Authentication is required to run ATA SMART     |
|          self tests                                      |
|                                                          |
|          An application is attempting to perform an      |
|          action that requires privileges. Authentication |
|          as one of the users below is required to        |
|          perform this action.                            |
|                                                          |
|          [[Face] Patrick Bateman (bateman)         [V]]  |
|                                                          |
|          Password for bateman: [______________________]  |
|                                                          |
| [V] Details:                                             |
|  Drive:  ATA INTEL SSDSA2MH08 (045C)                     |
|  Device: /dev/sda                                        |
|  Action: org.fd.devicekit.disks.drive-ata-smart-selftest |
|  Vendor: The DeviceKit Project                           |
|                                                          |
|                                  [Cancel] [Authenticate] |
+----------------------------------------------------------+
]]></programlisting>
      </textobject>
    </mediaobject>
    <para>
      See
      <citerefentry><refentrytitle>pklocalauthority</refentrytitle><manvolnum>8</manvolnum></citerefentry>
      on how to set up the local authority
      implemention for systems without a <literal>root</literal>
      account.
    </para>

    <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
      <citerefentry><refentrytitle>pkttyagent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
      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 <quote>ACTIONS</quote> in
      order to use PolicyKit. 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>/usr/share/polkit-1/actions</filename> directory.
    </para>

    <para>
      PolicyKit actions are namespaced and can only contain the
      characters <literal>[a-z][0-9].-</literal> e.g. lower-case
      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 <literal>.policy</literal>.
    </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 PolicyKit Policy Configuration 1.0//EN"
"http://www.freedesktop.org/standards/PolicyKit/1.0/policyconfig.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][0-9].-</literal>
        e.g. lower-case ASCII, digits, period and
        hyphen.</para></listitem>
      </varlistentry>
    </variablelist>
    <para>
      Elements that can be used inside <emphasis>action</emphasis> includes:
    </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.</para>
          <para>
            Elements that can be used inside <emphasis>defaults</emphasis> includes:
          </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 PolicyKit actions, use the
      <citerefentry><refentrytitle>pkaction</refentrytitle><manvolnum>1</manvolnum></citerefentry>
      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 PolicyKit - see the
      <citerefentry><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry>
      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-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>
      <citerefentry>
        <refentrytitle>pklocalauthority</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>
      <citerefentry>
        <refentrytitle>polkitd</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>
      <citerefentry>
        <refentrytitle>pkaction</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pkcheck</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pkttyagent</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>
    </para>
  </refsect1>
</refentry>