NAME

       idmap_script - Samba's idmap_script Backend for Winbind

DESCRIPTION

       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.

       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.

IDMAP OPTIONS

       range = low - high
           Defines the available matching uid and gid range for which the backend is
           authoritative.

       script
           This option can be used to configure an external program for performing id mappings.

IDMAP SCRIPT

       The tdb2 idmap backend supports an external program for performing id mappings through the
       /etc/samba/smb.conf option idmap config * : script or its deprecated legacy form idmap :
       script.

       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.

       The script should accept the following command line options.

                SIDTOID S-1-xxxx
                IDTOSID UID xxxx
                IDTOSID GID xxxx
                IDTOSID XID xxxx

       And it should return one of the following responses as a single line of text.

                UID:yyyy
                GID:yyyy
                XID:yyyy
                SID:ssss
                ERR:yyyy

       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.

EXAMPLES

       This example shows how script is used as a the default idmap backend using an external
       program via the script parameter:

                [global]
                idmap config * : backend = script
                idmap config * : range = 1000000-2000000
                idmap config * : script = /usr/local/samba/bin/idmap_script.sh

       This shows a simple script to partially perform the task:

                #!/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

       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.

       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 ls -l could
       trigger such an infinite recursion.

       It is safe to call wbinfo -n and wbinfo -s from within an idmap script. To do so, the
       script must unset the _NO_WINBINDD environment variable right before the call to wbinfo
       and set it to 1 again right after wbinfo has returned to protect against the recursion.

AUTHOR

       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.