Taken from
http://www.ccm.ece.vt.edu/~lscharf/samd/?topic=Linux&title=Linux+autofs+with+LDAP :

Linux autofs with LDAP
Keywords:
Date Created: 2002-05-17
Author: Luke Scharf <luke@vt.edu>

Problem: The Linux automounter (autofs) will not bind to an LDAP server
that requires the client to authenticate. Autofs is only able to get
automount information from an LDAP server that will allow
anyone-in-the-world to bind to it. I verified this by reading
lookup_ldap.c from the autofs-3.1.7 source code.

Solution: Autofs conveniently allows you to generate your mapping with
an external program. This program takes a username as a command-line
parameter and writes the location to standard output. There is also the
ldapsearch command line tool, which will authenticate (properly) to an
ldap server and search for arbitrary information.

I put these pieces together with a perl script. In addition to actually
authenticating with the LDAP server before attempting a query, this
script reads the settings from the global LDAP settings.

Here's the script:

#!/usr/bin/perl -w
#
# Name: auto.home_ldap
#
# Purpose: To retrieve automount information from an LDAP server that
# refuses anonymous binding.  The existing Linux automount client (as of
# RedHat 7.3) can only retrieve automount information if anonymous
# binding is allowed.  Since I don't want to hand out user information
# to just anyone, a password is required to connect to the server.
#
# Author: Luke Scharf (luke@vt.edu) May, 2002
#
# License: GNU General Public License (http://www.gnu.org)
#

##### Includes #####
use strict;


##### Constants #####
my $scope  = "subtree";
my $fields = "automountInformation";


##### Variables #####
my $host;
my $binddn;
my $bindpw;
my $base;
my $ssl;
my $username;
my $query;


##### Get Parameters #####
# Parse command line
my $ARGC = @ARGV;
if ($ARGC < 1) { exit 0; } # Abort if no commands were given
$username = $ARGV[0]; # What user's home directory are we looking for?

# Read system-wide ldap configuration file(s)
open(CONFIG, "< /etc/ldap.conf");
while(<CONFIG>) {
	# Tokenize the line
	@_ = split();

	# Do not process blank or bogus lines
	if ( not $_[0] ) { next; }

	# Store parameters from the config file
	if ( $_[0] =~ /^host$/ ) { $host = $_[1];  }
	if ( $_[0] =~ /^binddn$/ ) { $binddn= $_[1]; }
	if ( $_[0] =~ /^bindpw$/ ) { $bindpw= $_[1]; }
	if ( $_[0] =~ /^base$/ ) { $base= $_[1]; }
	if ( $_[0] =~ /^ssl$/ ) { $ssl = $_[1]; }
}


##### Communicate With LDAP Server #####
# Compose the query
$query = "(&(objectClass=automount)(cn=$username))";

# Glob together a command line with all of the search parameters
my $ldapcommand;
$ldapcommand = "ldapsearch -LLL";
$ldapcommand .= " -h $host";
$ldapcommand .= " -D $binddn";
if ($ssl=~/no/) {
	$ldapcommand .= " -x";
}
$ldapcommand .=	" -w \"$bindpw\"";
$ldapcommand .=	" -b $base";
$ldapcommand .=	" -s $scope";
$ldapcommand .=	" \'$query\'";
$ldapcommand .=	" $fields";

# Open a pipe to ldapsearch
open(LDAP, "$ldapcommand |");

# Output in an automounter-friendly manner
my $user;
my $home;
while( my $line = <LDAP>) {
	chomp $line;

	if ($line =~ /^automountInformation\:/) {
		$home = $line;
		$home =~ s|^automountInformation\: ||g;
		print "$home\n";
	}
}

This script is then referenced by an entry in /etc/auto.master that
looks like this:

/home program:/etc/auto.home_ldap.pl

Despite the fact that this script necessitates two forks for every
search, the speed is quite good. My guestimate is that the NFS-mount
takes most of the time when you reference a file in an unmounted home
directory.