1. ldap module

Jan Janak

   Iptel.org

   Copyright © 2008 Iptel.org GmBH
     __________________________________________________________________

   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
