The Lightweight Directory Access Protocol (LDAP) (RFC 3377) provides
access to X.500 directory services. These services may be stand-alone
or part of a distributed directory service. This client API supports
LDAP over TCP (RFC2251), LDAP over TLS/SSL, and LDAP over IPC (UNIX
domain sockets). This API supports SASL (RFC2829) and Start TLS
(RFC2830) as well as a number of protocol extensions. This API is
loosely based upon IETF/LDAPEXT C LDAP API draft specification, a (orphaned)
work in progress.
The OpenLDAP Software package includes a stand-alone server in
slapd(8),
various LDAP clients, and an LDAP client library used to provide
programmatic access to the LDAP protocol. This man page gives an
overview of the LDAP library routines.
Both synchronous and asynchronous APIs are provided. Also included are
various routines to parse the results returned from these routines.
These routines are found in the -lldap library.
The basic interaction is as follows. A session handle is
created using
ldap_initialize(3)
and set the protocol version to 3 by calling
ldap_set_option(3).
The underlying session is established first operation is
issued. This would generally be a Start TLS or Bind operation.
A Start TLS operation is performed by calling
ldap_start_tls_s(3).
A LDAP bind operation is performed by calling
ldap_sasl_bind(3)
or one of its friends. Subsequently, other operations are performed
by calling one of the synchronous or asynchronous routines (e.g.,
ldap_search_ext_s(3)
or
ldap_search_ext(3)
followed by
ldap_result(3)).
Results returned from these routines are interpreted by calling the
LDAP parsing routines such as
ldap_parse_result(3).
The LDAP association and underlying connection is terminated by calling
ldap_unbind_ext(3).
Errors can be interpreted by calling
ldap_err2string(3).
LDAP versions
This library supports version 3 of the Lightweight Directory Access
Protocol (LDAPv3) as defined in RFC 3377. It also supports a variant
of version 2 of LDAP as defined by U-Mich LDAP and, to some degree,
RFC 1777. Version 2 (all variants) should be viewed as obsolete.
Version 3 should be used instead.
For backwards compatibility reasons, the library defaults to version 2.
Hence, all new applications (and all actively maintained applications)
should use
ldap_set_option(3)
to select version 3. The library manual pages assume version 3
has been selected.
INPUT and OUTPUT PARAMETERS
All character string input/output is expected to be/is UTF-8
encoded Unicode (version 3.2).
Distinguished names (DN) (and relative distinguished names (RDN) to
be passed to the LDAP routines should conform to RFC 2253 UTF-8
string representation.
Search filters to be passed to the search routines are to be
constructed by hand and should conform to RFC 2254 UTF-8
string representation.
LDAP URL are to be passed to routines are expected to conform
to RFC 2255 syntax. The
ldap_url(3)
routines can be used to work with LDAP URLs.
DISPLAYING RESULTS
Results obtained from the search routines can be output by hand,
by calling
ldap_first_entry(3)
and
ldap_next_entry(3)
to step through
the entries returned,
ldap_first_attribute(3)
and
ldap_next_attribute(3)
to step through an entry's attributes, and
ldap_get_values(3)
to retrieve a given attribute's values. Attribute values
may or may not be displayable.
UTILITY ROUTINES
Also provided are various utility routines. The
ldap_sort(3)
routines are used to sort the entries and values returned via
the ldap search routines.
BER LIBRARY
Also included in the distribution is a set of lightweight Basic
Encoding Rules routines. These routines are used by the LDAP library
routines to encode and decode LDAP protocol elements using the
(slightly simplified) Basic Encoding Rules defined by LDAP. They are
not normally used directly by an LDAP application program except
in the handling of controls and extended operations. The
routines provide a printf and scanf-like interface, as well as
lower-level access. These routines are discussed in
lber-decode(3),
lber-encode(3),
lber-memory(3),
and
lber-types(3).
OpenLDAP
is developed and maintained by The OpenLDAP Project (http://www.openldap.org/).OpenLDAP
is derived from University of Michigan LDAP 3.3 Release.
These API manual pages are loosely based upon descriptions provided
in the IETF/LDAPEXT C LDAP API Internet Draft, a (orphaned) work
in progress.
