1. ldap module

Jan Janak

   Iptel.org

   Copyright © 2008 Iptel.org GmBH
   Revision History
   Revision $Revision$ $Date$
     _________________________________________________________________

   1.1. Overview
   1.2. Dependencies
   1.3. Parameters

        1.3.1. config (string)
        1.3.2. reconnect_attempt (integer)

   1.4. Functions

1.1. Overview

   The LDAP module is database driver, i.e. it implements DB API functions. The
   goal is map database query defined by table, matching fields and result
   fields to LDAP search in sub-tree defined by root, object class, attributes
   and pass it to the OpenLDAP which communicates with the LDAP server.

   This procedure is sometimes tricky because the LDAP does not support all
   database features or supports them in different manner. Here we must express
   especially filtering and multi-values. The multi-value is de facto array of
   single values. If the LDAP module get a multi-value field then generates
   record for every single value, respectively for every combination in case
   the more fields contain multi-value.

   The LDAP supports natively "AND", "OR", "NOT" logical operators and "equal",
   "non-equal", "less-or-equal" and "greater-or-equal" comparison operators.
   Therefore    "less"    and   "greater"   operators   are   mapped   as
   "less/greater-or-equal-AND-not-equal". It's important realize it when the
   attribute which will be used for filtering may contain multi-value. The LDAP
   server evaluates comparison operator on multi-value so that the result for
   record is true if the condition is satisfied for any single value. The
   single values not satisfying condition are not truncated. It implies two
   cases for positive comparison, e.g. "equal", the result contains values not
   satisfying the condition, the case may be handled by additional filter in
   the LDAP module, the negative comparison, e.g. "non-equal", does not return
   record at all. Because the LDAP module cannot know if the LDAP attribute may
   logically  contain  multi-value  so  there is introduced DB API option
   client_side_filtering which forces filtering such fields in the LDAP module,
   i.e.  the  LDAP server returns larger result set because the filtering
   condition is not passed there.

   The syntax of client_side_filtering value is comma delimited of field names
   which won't be used for server-side filter if such a field appears in a
   match condition. Instead records will be filtered out in module. It implies
   such fields MUST exist in result field list.

   The necessary condition of successful filtering of particular attribute at
   the LDAP server is correct attribute definition. The "equal"/"non-equal"
   operator requires equality matching rule, the "greater"/"less" operator
   requires ordering matching rule. If required matching rule is missing the
   LDAP server silently returns empty result set. In case of double filtering
   both at the LDAP servar and the LDAP module, e.g. multi-value and equal
   comparison, check the LDAP server matching rule satisfies your needs or use
   client_side_filtering feature.

   The LDAP server may be identified either complete specification of host,
   user, password in URI or is specification reference to connection section of
   config file. Note in the second case there is only one slash.

   Example 1. URI example
        ...
        modparam("auth", "db_url", "ldap://admin:heslo@127.0.0.1");

        modparam("auth", "db_url", "ldap:/ldap_server1");

        ...

   Features:
     * simple, SASL authentication, TLS
     * server and client side filtering
     * read-only queries
     * optional referral chasing by OpenLDAP
     * optional reference chasing by OpenLDAP

1.2. Dependencies

   none

1.3. Parameters

1.3.1. config (string)

   Default value is ldap.cfg.

   The filename (relatively to ser config file) of mapping database to LDAP
   definition. It is the main configuration file for the LDAP module in SER.
   The  configuration  file maps database table names used in SER to LDAP
   directory sub-trees to be searched. In addition to that the configuration
   file also allows to configure the LDAP search filter and maps database field
   names to LDAP attribute names and vice versa.

   Example 2. Example config
        ...
        modparam("ldap", "config", "my-ldap.cfg");
        ...

   Example 3. Configuration file example
# Supported Attribute Type Names:
#  * GeneralizedTime
#  * Integer
#  * BitString
#  * Boolean
#  * String
#  * Binary
#  * Float
#

[connection:ldap_server1]
host=127.0.0.1
port=389
username=ser
password=heslo
# LDAP or LDAP SASL authentication mechanism.
# Allowed values: none (default), simple, digest-md5, external
authtype=simple

# tls encryption
tls=off

# Specifies the file that contains certificates for all of the Certificate
# Authorities the ldap module will recognize.
ca_list=/home/kg/work/openssl/demoCA/cacert.pem

# Specifies what checks to perform on server certificates in a TLS session
# allowed values are never/allow/try/demand
# see the TLS_REQCERT tls option part of ldap.conf(8) man page for more details
require_certificate=demand

#
# Table credentials contains SIP digest authentication credentials.
#
[table:credentials]

# In our LDAP directory we store SIP digest credentials under
# "Digest Credentials" organization unit so this is where searches for digest
# credentials should start.
base = "ou=Digest Credentials,dc=iptel,dc=org"

# We search the whole subtree.
scope = subtree

# For digest credentials we are only interested in objects with objectClass
# 'digestAuthCredentials', objects of all other types are ignored.
filter = "(objectClass=digestAuthCredentials)"

# Mapping of field names to LDAP attribute names and vice versa. Names are
# delimited using ':', the first name is database field name as used in SER
# modules, the second name (after :) is corresponding LDAP attribute name,
# optionally preceeded with LDAP attribute syntax name in parentheses.
field_map = password : (Binary) digestPassword
field_map = realm : digestRealm
field_map = auth_username : digestUsername
field_map = uid : serUID
field_map = flags : (BitString) serFlags

# retrieve at most sizelimit entries for a search
#sizelimit = 2147483647

# wait at most timelimit seconds for a search to complete
#timelimit = 120

# chase references automatically by OpenLDAP. Default is "never"
# chase_references = never | searching | finding | always

# chase referrals automatically by OpenLDAP. Default is "no"
# chase_referrals = yes | no

#
# Domain table stores information about virtual domains
#
[table:domain]

# Objects mapping domain IDs to domain names and vice versa are stored
# in the subtree with the following root:
base = "ou=Domains,dc=iptel,dc=org"

scope = subtree

# We are only interested in serDomain objects when looking up information
# about virtual domains.
filter = "(objectClass=serDomain)"

field_map = did : (String) serDID
field_map = domain : (String) serDomain
field_map = flags : (BitString) serFlags

#
# Table domain_attrs contains domain attributes, domain attributes store
# extra information about virtual domains.
#
[table:domain_attrs]
base = "ou=Domains, dc=iptel,dc=org"
scope = subtree

filter = "(objectClass=serDomainAttr)"

field_map = did : serDID
field_map = name : serAttrName
field_map = type : (Integer) serAttrType
field_map = value : serAttrValue
field_map = flags : (BitString) serFlags

1.3.2. reconnect_attempt (integer)

   Default value is 3.

   Number of reconnect attempts when connection to the LDAP server is lost.

   Example 4. Example reconnect_attempt
        ...
        modparam("ldap", "reconnect_attempt", "5");
        ...

1.4. Functions

   none