path: root/modules/pam_namespace/pam_namespace.8.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
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<refentry id='pam_namespace'>

  <refmeta>
    <refentrytitle>pam_namespace</refentrytitle>
    <manvolnum>8</manvolnum>
    <refmiscinfo class='setdesc'>Linux-PAM Manual</refmiscinfo>
  </refmeta>

  <refnamediv id='pam_namespace-name'>
    <refname>pam_namespace</refname>
    <refpurpose>
      PAM module for configuring namespace for a session
    </refpurpose>
  </refnamediv>

<!-- body begins here -->

  <refsynopsisdiv>
    <cmdsynopsis id="pam_namespace-cmdsynopsis">
      <command>pam_namespace.so</command>
      <arg choice="opt">
        debug
      </arg>
      <arg choice="opt">
        unmnt_remnt
      </arg>
      <arg choice="opt">
        unmnt_only
      </arg>
      <arg choice="opt">
        require_selinux
      </arg>
      <arg choice="opt">
        gen_hash
      </arg>
      <arg choice="opt">
        ignore_config_error
      </arg>
      <arg choice="opt">
        ignore_instance_parent_mode
      </arg>
      <arg choice="opt">
        unmount_on_close
      </arg>
      <arg choice="opt">
        use_current_context
      </arg>
      <arg choice="opt">
        use_default_context
      </arg>
      <arg choice="opt">
        mount_private
      </arg>
    </cmdsynopsis>
  </refsynopsisdiv>


  <refsect1 id="pam_namespace-description">
    <title>DESCRIPTION</title>
    <para>
      The pam_namespace PAM module sets up a private namespace for a session
      with polyinstantiated directories. A polyinstantiated directory
      provides a different instance of itself based on user name, or when
      using SELinux, user name, security context or both.  If an executable
      script <filename>/etc/security/namespace.init</filename> exists, it
      is used to initialize the instance directory after it is set up
      and mounted on the polyinstantiated directory. The script receives the
      polyinstantiated directory path, the instance directory path, flag
      whether the instance directory was newly created (0 for no, 1 for yes),
      and the user name as its arguments.
    </para>

    <para>
      The pam_namespace module disassociates the session namespace from
      the parent namespace. Any mounts/unmounts performed in the parent
      namespace, such as mounting of devices, are not reflected in the
      session namespace. To propagate selected mount/unmount events from
      the parent namespace into the disassociated session namespace, an
      administrator may use the special shared-subtree feature. For
      additional information on shared-subtree feature, please refer to
      the mount(8) man page and the shared-subtree description at
      http://lwn.net/Articles/159077 and http://lwn.net/Articles/159092.
    </para>

  </refsect1>

  <refsect1 id="pam_namespace-options">
    <title>OPTIONS</title>
    <variablelist>

      <varlistentry>
        <term>
          <option>debug</option>
        </term>
        <listitem>
          <para>
            A lot of debug information is logged using syslog
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>unmnt_remnt</option>
        </term>
        <listitem>
          <para>
            For programs such as su and newrole, the login
            session has already setup a polyinstantiated
            namespace. For these programs, polyinstantiation
            is performed based on new user id or security
            context, however the command first needs to
            undo the polyinstantiation performed by login.
            This argument instructs the command to
            first undo previous polyinstantiation before
            proceeding with new polyinstantiation based on
            new id/context
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>unmnt_only</option>
        </term>
        <listitem>
          <para>
            For trusted programs that want to undo any
            existing bind mounts and process instance
            directories on their own, this argument allows
            them to unmount currently mounted instance
            directories
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>require_selinux</option>
        </term>
        <listitem>
          <para>
            If selinux is not enabled, return failure
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>gen_hash</option>
        </term>
        <listitem>
          <para>
            Instead of using the security context string
            for the instance name, generate and use its
            md5 hash.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>ignore_config_error</option>
        </term>
        <listitem>
          <para>
            If a line in the configuration file corresponding
            to a polyinstantiated directory contains format
            error, skip that line process the next line.
            Without this option, pam will return an error
            to the calling program resulting in termination
            of the session.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>ignore_instance_parent_mode</option>
        </term>
        <listitem>
          <para>
	    Instance parent directories by default are expected to have
	    the restrictive mode of 000. Using this option, an administrator
	    can choose to ignore the mode of the instance parent. This option
            should be used with caution as it will reduce security and
            isolation goals of the polyinstantiation mechanism.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>unmount_on_close</option>
        </term>
        <listitem>
          <para>
           Explicitly unmount the polyinstantiated directories instead
           of relying on automatic namespace destruction after the last
           process in a namespace exits. This option should be used
           only in case it is ensured by other means that there cannot be
           any processes running in the private namespace left after the
           session close. It is also useful only in case there are
           multiple pam session calls in sequence from the same process.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>use_current_context</option>
        </term>
        <listitem>
          <para>
	    Useful for services which do not change the SELinux context
	    with setexeccon call. The module will use the current SELinux
	    context of the calling process for the level and context
	    polyinstantiation.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>use_default_context</option>
        </term>
        <listitem>
          <para>
	    Useful for services which do not use pam_selinux for changing
	    the SELinux context with setexeccon call. The module will use
	    the default SELinux context of the user for the level and context
	    polyinstantiation.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>mount_private</option>
        </term>
        <listitem>
          <para>
	    This option can be used on systems where the / mount point or
	    its submounts are made shared (for example with a
	    <command>mount --make-rshared /</command> command).
	    The module will mark the whole directory tree so any mount and
	    unmount operations in the polyinstantiation namespace are private.
	    Normally the pam_namespace will try to detect the
	    shared / mount point and make the polyinstantiated directories
	    private automatically. This option has to be used just when
	    only a subtree is shared and / is not.
          </para>
          <para>
	    Note that mounts and unmounts done in the private namespace will not
	    affect the parent namespace if this option is used or when the
	    shared / mount point is autodetected.
          </para>
        </listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1 id="pam_namespace-types">
    <title>MODULE TYPES PROVIDED</title>
    <para>
      Only the <option>session</option> module type is provided.
      The module must not be called from multithreaded processes.
    </para>
  </refsect1>

  <refsect1 id="pam_namespace-return_values">
    <title>RETURN VALUES</title>
    <variablelist>
      <varlistentry>
        <term>PAM_SUCCESS</term>
        <listitem>
           <para>
             Namespace setup was successful.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_SERVICE_ERR</term>
        <listitem>
           <para>
             Unexpected system error occurred while setting up namespace.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_SESSION_ERR</term>
        <listitem>
           <para>
             Unexpected namespace configuration error occurred.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id="pam_namespace-files">
    <title>FILES</title>
    <variablelist>
      <varlistentry>
        <term><filename>/etc/security/namespace.conf</filename></term>
        <listitem>
          <para>Main configuration file</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><filename>/etc/security/namespace.d</filename></term>
        <listitem>
          <para>Directory for additional configuration files</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><filename>/etc/security/namespace.init</filename></term>
        <listitem>
          <para>Init script for instance directories</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id="pam_namespace-examples">
    <title>EXAMPLES</title>

    <para>
      For the &lt;service&gt;s you need polyinstantiation (login for example)
      put the following line in /etc/pam.d/&lt;service&gt; as the last line for
      session group:
    </para>

    <para>
      session  required  pam_namespace.so [arguments]
    </para>

    <para>
      To use polyinstantiation with graphical display manager gdm, insert the
      following line, before exit 0, in /etc/gdm/PostSession/Default:
    </para>

    <para>
      /usr/sbin/gdm-safe-restart
    </para>

    <para>
      This allows gdm to restart after each session and appropriately adjust
      namespaces of display manager and the X server. If polyinstantiation
      of /tmp is desired along with the graphical environment, then additional
      configuration changes are needed to address the interaction of X server
      and font server namespaces with their use of /tmp to create
      communication sockets. Please use the initialization script
      <filename>/etc/security/namespace.init</filename> to ensure that
      the X server and its clients can appropriately access the
      communication socket X0. Please refer to the sample instructions
      provided in the comment section of the instance initialization script
      <filename>/etc/security/namespace.init</filename>. In addition,
      perform the following changes to use graphical environment with
      polyinstantiation of /tmp:
    </para>

    <para>
    <literallayout>
      1. Disable the use of font server by commenting out "FontPath"
         line in /etc/X11/xorg.conf. If you do want to use the font server
         then you will have to augment the instance initialization
         script to appropriately provide /tmp/.font-unix from the
         polyinstantiated /tmp.
      2. Ensure that the gdm service is setup to use pam_namespace,
         as described above, by modifying /etc/pam.d/gdm.
      3. Ensure that the display manager is configured to restart X server
         with each new session. This default setup can be verified by
         making sure that /usr/share/gdm/defaults.conf contains
         "AlwaysRestartServer=true", and it is not overridden by
         /etc/gdm/custom.conf.
    </literallayout>
    </para>

  </refsect1>

  <refsect1 id="pam_namespace-see_also">
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
        <refentrytitle>namespace.conf</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>

  <refsect1 id="pam_namespace-authors">
    <title>AUTHORS</title>
    <para>
      The namespace setup scheme was designed by Stephen Smalley, Janak Desai
      and Chad Sellers.
      The pam_namespace PAM module was developed by Janak Desai &lt;janak@us.ibm.com&gt;,
      Chad Sellers &lt;csellers@tresys.com&gt; and Steve Grubb &lt;sgrubb@redhat.com&gt;.
      Additional improvements by Xavier Toth &lt;txtoth@gmail.com&gt; and Tomas Mraz
      &lt;tmraz@redhat.com&gt;.
    </para>
  </refsect1>
</refentry>