Service Search Descriptors and Schema Mapping

As previously discussed, LDAP naming services expect, by default, the DIT to be structured in a certain way. If you want, you can instruct the LDAP naming service to search in other locations than the default locations in the DIT by using service search descriptors (SSDs). Additionally, you can specify that different attributes and object classes be used in place of those specified by the default schema. For a list of default filters, see Default Filters Used by LDAP Naming Services.

Description of SSDs

The serviceSearchDescriptor attribute defines how and where an LDAP naming service client should search for information for a particular service. The serviceSearchDescriptor contains a service name, followed by one or more semicolon-separated base-scope-filter triples. These base-scope-filter triples are used to define searches only for the specific service and are searched in order. If multiple base-scope-filters are specified for a given service, then when that service looks for a particular entry, it will search in each base with the specified scope and filter.

In the following example, the LDAP naming service client performs a one-level search in ou=west,dc=example,dc=com followed by a one-level search in ou=east,dc=example,dc=com for the passwd service. To look up the passwd data for a user's username, the default LDAP filter (&(objectClass=posixAccount)(uid=username)) is used for each BaseDN.

serviceSearchDescriptor: passwd:ou=west,dc=example,dc=com;ou=east,
dc=example,dc=com 

In the following example, the LDAP naming service client would perform a subtree search in ou=west,dc=example,dc=com for the passwd service. To look up the passwd data for user username, the subtree ou=west,dc=example,dc=com would be searched with the LDAP filter (&(fulltimeEmployee=TRUE)(uid=username)).

serviceSearchDescriptor: passwd:ou=west,dc=example,
dc=com?sub?fulltimeEmployee=TRUE

It is also possible to associate multiple containers with a particular service type. In the following example, the service search descriptor specifies searching for the password entries in three containers.

Note that a trailing ',' in the example implies that the defaultSearchBase is appended to the relative base in the SSD.

defaultSearchBase: dc=example,dc=com
serviceSearchDescriptor: \
passwd:ou=myuser,;ou=newuser,;ou=extuser,dc=example,dc=com

attributeMap Attributes

The LDAP naming service allows one or more attribute names to be remapped for any of its services. (The LDAP client uses the well-known attributes documented in Chapter 14, LDAP Naming Service (Reference).) If you map an attribute, you must be sure that the attribute has the same meaning and syntax as the original attribute. Note that mapping the userPassword attribute might cause problems.

There are a couple of reasons you might want to use schema mappings.

• You want to map attributes in an existing directory server

• If you have user names that differ only in case, you must map the uid attribute, which ignores case, to an attribute that does not ignore case

The format for this attribute is service:attribute-name=mapped-attribute-name.

If you want to map more than one attribute for a given service, you can define multiple attributeMap attributes.

In the following example, the employeeName and home attributes would be used whenever the uid and homeDirectory attributes would be used for the passwd service.

attributeMap: passwd:uid=employeeName
attributeMap: passwd:homeDirectory=home

There exists one special case where you can map the passwd service's gecos attribute to several attributes. The following is an example.

attributeMap: gecos=cn sn title

This maps the gecos values to a space separated list of the cn, sn, and title attribute values.

objectclassMap Attribute

The LDAP naming service allows object classes to be remapped for any of its services. If you want to map more than one object class for a given service, you can define multiple objectclassMap attributes. In the following example, the myUnixAccount object class is used whenever the posixAccount object class is used.

objectclassMap: passwd:posixAccount=myUnixAccount