LDAP auxprop plugin for SASL-enabled servers.
Copyright (C) 2002,2003 by Howard Chu, hyc@symas.com

This software is licensed under the terms of the OpenLDAP license.

The file ldapdb.c was written for Cyrus SASL 2.1.3 and OpenLDAP 2.1.3.
Due to various bugs in the Cyrus source you should use Cyrus SASL 2.1.15
or newer. You need at least Cyrus SASL 2.1.16 to use the auxprop-store
functionality.

The version of ldapdb bundled with OpenLDAP 2.1.22 and older will work
with all OpenLDAP releases 2.1.3 and up. The ldapdb in OpenLDAP 2.1.23
uses a different LDAP request and requires the server to be 2.1.23 or newer.

It can be compiled by copying into the Cyrus SASL source tree, in the
plugins subdirectory. No configuration or build script is provided.

To compile, type "make ldapdb.lo". To link, you'll have to copy the
link rule for one of the other plugins. Below is a sample on my Linux
system:

	/bin/sh ../libtool --mode=link gcc  -Wall -W -g -O2 -L/usr/local/lib -Wl,-rpath,/usr/local/lib -module -export-dynamic -rpath /usr/lib/sasl2 -o libldapdb.la  -version-info 2:4:0 ldapdb.lo -lldap -llber -lssl -lcrypto

Once installed, you need to add some config items to the SASL server's
config file in /usr/lib/sasl2. For example:

ldapdb_uri: ldap://ldap.example.com
ldapdb_id: root
ldapdb_pw: secret
ldapdb_mech: DIGEST-MD5

This config assumes an LDAP server on the same machine as the server
that is using SASL. The LDAP server must be configured to map the SASL
authcId "root" into a DN that has proxy authorization privileges to
every account that is allowed to login to this server. (See the OpenLDAP
Admin Guide section 10 for details.)

Unlike other LDAP-enabled plugins for other services that are common
on the web, this plugin does not require you to configure DN search
patterns to map usernames to LDAP DNs. This plugin requires SASL name
mapping to be configured on the target slapd. This approach keeps the
LDAP-specific configuration details in one place, the slapd.conf, and
makes the configuration of remote services much simpler.

An additional keyword "ldapdb_rc" may be specified in the config file.
The filename specified here will be put into the server's LDAPRC
environment variable, and libldap-specific config options may be set
in that ldaprc file. The main purpose behind this option is to allow
a client TLS certificate to be configured, so that SASL/EXTERNAL may
be used between the SASL server and the LDAP server. This is the most
optimal way to use this plugin when the servers are on separate machines.

Note: this plugin is not for use with slapd itself. When OpenLDAP is
built with SASL support, slapd uses its own internal auxprop module.
By default, without configuring anything else, slapd will fail to load
the ldapdb module when it's present. This is as it should be. If you
don't like the "auxpropfunc: error -7" message that is sent to syslog
by slapd, you can stop it by creating /usr/lib/sasl2/slapd.conf with:

	auxprop_plugin: slapd

which will force the SASL library to ignore all other auxprop modules.

This plugin has been in use for over a year at many sites with good
results. If you have questions or problems, please send feedback via
the openldap-software mailing list.

  -- Howard Chu

Update... With OpenLDAP 2.1.13 you can use SASL/EXTERNAL on ldapi://.
This is fast and secure, and needs no username or password to be stored.
The SASL config file is just

ldapdb_uri: ldapi://
ldapdb_mech: EXTERNAL

The slapd.conf will need to map these usernames to LDAP DNs:

sasl-regexp uidNumber=(.*)\\+gidNumber=(.*),cn=peercred,cn=external,cn=auth
	ldap:///dc=example,dc=com??sub?(&(uidNumber=$1)(gidNumber=$2))

sasl-regexp uid=(.*),cn=external,cn=auth
	ldap:///dc=example,dc=com??sub?(uid=$1)

Update... With OpenLDAP 2.1.23 you can use the ldapdb_starttls keyword
to use the StartTLS extended operation on an LDAP session. This item
may be set to either "try" or "demand", e.g.:

ldapdb_uri: ldap://ldap.example.com
ldapdb_starttls: try

When set to "try" any failure in StartTLS is ignored. When set to "demand"
then any failure aborts the connection.