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<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE refentry PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
<refentry id="idmap_script.8">
<refmeta>
<refentrytitle>idmap_script</refentrytitle>
<manvolnum>8</manvolnum>
<refmiscinfo class="source">Samba</refmiscinfo>
<refmiscinfo class="manual">System Administration tools</refmiscinfo>
<refmiscinfo class="version">4.7</refmiscinfo>
</refmeta>
<refnamediv>
<refname>idmap_script</refname>
<refpurpose>Samba's idmap_script Backend for Winbind</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>DESCRIPTION</title>
<para>
The idmap_script plugin is a substitute for the idmap_tdb2
backend used by winbindd for storing SID/uid/gid mapping tables
in clustered environments with Samba and CTDB. It is a read only
backend that uses a script to perform mapping.
</para>
<para>
It was developed out of the idmap_tdb2 back end and does not store
SID/uid/gid mappings in a TDB, since the winbind_cache tdb will
store the mappings once they are provided.
</para>
</refsynopsisdiv>
<refsect1>
<title>IDMAP OPTIONS</title>
<variablelist>
<varlistentry>
<term>range = low - high</term>
<listitem><para>
Defines the available matching uid and gid range for which the
backend is authoritative.
</para></listitem>
</varlistentry>
<varlistentry>
<term>script</term>
<listitem><para>
This option can be used to configure an external program
for performing id mappings.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>IDMAP SCRIPT</title>
<para>
The tdb2 idmap backend supports an external program for performing id mappings
through the smb.conf option <parameter>idmap config * : script</parameter> or
its deprecated legacy form <parameter>idmap : script</parameter>.
</para>
<para>
The mappings obtained by the script are then stored in the idmap tdb2
database instead of mappings created by the incrementing id counters.
It is therefore important that the script covers the complete range of
SIDs that can be passed in for SID to Unix ID mapping, since otherwise
SIDs unmapped by the script might get mapped to IDs that had
previously been mapped by the script.
</para>
<para>
The script should accept the following command line options.
</para>
<programlisting>
SIDTOID S-1-xxxx
IDTOSID UID xxxx
IDTOSID GID xxxx
IDTOSID XID xxxx
</programlisting>
<para>
And it should return one of the following responses as a single line of
text.
</para>
<programlisting>
UID:yyyy
GID:yyyy
XID:yyyy
SID:ssss
ERR:yyyy
</programlisting>
<para>
XID indicates that the ID returned should be both a UID and a GID.
That is, it requests an ID_TYPE_BOTH, but it is ultimately up to
the script whether or not it can honor that request. It can choose
to return a UID or a GID mapping only.
</para>
</refsect1>
<refsect1>
<title>EXAMPLES</title>
<para>
This example shows how script is used as a the default idmap backend
using an external program via the script parameter:
</para>
<programlisting>
[global]
idmap config * : backend = script
idmap config * : range = 1000000-2000000
idmap config * : script = /usr/local/samba/bin/idmap_script.sh
</programlisting>
<para>
This shows a simple script to partially perform the task:
</para>
<programlisting>
#!/bin/sh
#
# Uncomment this if you want some logging
#echo $@ >> /tmp/idmap.sh.log
if [ "$1" == "SIDTOID" ]
then
# Note. The number returned has to be within the range defined
#echo "Sending UID:1000005" >> /tmp/idmap.sh.log
echo "UID:1000005"
exit 0
else
#echo "Sending ERR: No idea what to do" >> /tmp/idmap.sh.log
echo "ERR: No idea what to do"
exit 1
fi
</programlisting>
<para>
Clearly, this script is not enough, as it should probably use wbinfo
to determine if an incoming SID is a user or group SID and then
look up the mapping in a table or use some other mechanism for
mapping SIDs to UIDs and etc.
</para>
<para>
Please be aware that the script is called with the
_NO_WINBINDD environment variable set to 1. This prevents
recursive calls into winbind from the script both via
explicit calls to wbinfo and via implicit calls via
nss_winbind. For example a call to <command>ls -l</command>
could trigger such an infinite recursion.
</para>
<para>
It is safe to call <command>wbinfo -n</command> and
<command>wbinfo -s</command> from within an idmap script. To
do so, the script must unset the _NO_WINBINDD environment
variable right before the call to <command>wbinfo</command>
and set it to 1 again right after <command>wbinfo</command>
has returned to protect against the recursion.
</para>
</refsect1>
<refsect1>
<title>AUTHOR</title>
<para>
The original Samba software and related utilities
were created by Andrew Tridgell. Samba is now developed
by the Samba Team as an Open Source project similar
to the way the Linux kernel is developed.
</para>
</refsect1>
</refentry>
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