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<!DOCTYPE refentry PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
<refentry id="cifs.upcall.8">


<refmeta>
        <refentrytitle>cifs.upcall</refentrytitle>
        <manvolnum>8</manvolnum>
        <refmiscinfo class="source">cifs-utils</refmiscinfo>
        <refmiscinfo class="manual">System Administration tools</refmiscinfo>
        <refmiscinfo class="version">4.0</refmiscinfo>
</refmeta>

<refnamediv>
        <refname>cifs.upcall</refname>
        <refpurpose>Userspace upcall helper for Common Internet File System (CIFS)</refpurpose>
</refnamediv>

<refsynopsisdiv>
        <cmdsynopsis>
                <command>cifs.upcall</command>
                <arg choice="opt">--trust-dns|-t</arg>
                <arg choice="opt">--version|-v</arg>
                <arg choice="req">keyid</arg>
        </cmdsynopsis>
</refsynopsisdiv>


<refsect1>
        <title>DESCRIPTION</title>

        <para>This tool is part of the cifs-utils suite.</para>

<para>cifs.upcall is a userspace helper program for the linux CIFS client
filesystem. There are a number of activities that the kernel cannot easily
do itself. This program is a callout program that does these things for the
kernel and then returns the result.</para>

<para>cifs.upcall is generally intended to be run when the kernel calls
request-key<manvolnum>8</manvolnum> for a particular key type. While it
can be run directly from the command-line, it's not generally intended
to be run that way.</para>
</refsect1>

<refsect1>
	<title>OPTIONS</title>
	<variablelist>
		<varlistentry>
		<term>-c</term>
		<listitem><para>This option is deprecated and is currently ignored.
		</para></listitem>
		</varlistentry>
		<varlistentry>
		<term>--trust-dns|-t</term>
		<listitem><para>With krb5 upcalls, the name used as the host portion of the service principal defaults to the hostname portion of the UNC. This option allows the upcall program to reverse resolve the network address of the server in order to get the hostname.</para>
		<para>This is less secure than not trusting DNS. When using this option, it's possible that an attacker could get control of DNS and trick the client into mounting a different server altogether. It's preferable to instead add server principals to the KDC for every possible hostname, but this option exists for cases where that isn't possible. The default is to not trust reverse hostname lookups in this fashion.
		</para></listitem>
		</varlistentry>
		<varlistentry>
		<term>--version|-v</term>
		<listitem><para>Print version number and exit.
		</para></listitem>
		</varlistentry>
	</variablelist>
</refsect1>

<refsect1>
	<title>CONFIGURATION FOR KEYCTL</title>
	<para>cifs.upcall is designed to be called from the kernel via the
	request-key callout program. This requires that request-key be told
	where and how to call this program. The current cifs.upcall program
	handles two different key types:
	</para>

	<variablelist>
		<varlistentry>
		<term>cifs.spnego</term>
		<listitem><para>This keytype is for retrieving kerberos session keys
		</para></listitem>
		</varlistentry>

		<varlistentry>
		<term>dns_resolver</term>
		<listitem><para>This key type is for resolving hostnames into IP addresses
		</para></listitem>
		</varlistentry>
	</variablelist>

	<para>To make this program useful for CIFS, you'll need to set up entries for them in request-key.conf<manvolnum>5</manvolnum>. Here's an example of an entry for each key type:</para>
<programlisting>
#OPERATION  TYPE           D C PROGRAM ARG1 ARG2...
#=========  =============  = = ================================
create      cifs.spnego    * * /usr/local/sbin/cifs.upcall %k
create      dns_resolver   * * /usr/local/sbin/cifs.upcall %k
</programlisting>
<para>
See <citerefentry><refentrytitle>request-key.conf<manvolnum>5</manvolnum></refentrytitle></citerefentry> for more info on each field.
</para>
</refsect1>

<refsect1>
        <title>SEE ALSO</title>
        <para>
	<citerefentry><refentrytitle>request-key.conf</refentrytitle>
        <manvolnum>5</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>mount.cifs</refentrytitle>
        <manvolnum>8</manvolnum></citerefentry>
	</para>
</refsect1>

<refsect1>
        <title>AUTHOR</title>

	<para>Igor Mammedov wrote the cifs.upcall program.</para>
	<para>Jeff Layton authored this manpage.</para>
	<para>The maintainer of the Linux CIFS VFS is Steve French.</para>
        <para>The <ulink url="mailto:linux-cifs-client@lists.samba.org">Linux
		CIFS Mailing list</ulink> is the preferred place to ask
		questions regarding these programs.
	</para>
</refsect1>

</refentry>
