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LDAP_BIND(3) Library Functions Manual LDAP_BIND(3)
NAME
ldap_bind, ldap_bind_s, ldap_simple_bind, ldap_simple_bind_s,
ldap_sasl_bind, ldap_sasl_bind_s, ldap_sasl_interactive_bind_s,
ldap_parse_sasl_bind_result, ldap_unbind, ldap_unbind_s,
ldap_unbind_ext, ldap_unbind_ext_s, ldap_set_rebind_proc - LDAP bind
routines
LIBRARY
OpenLDAP LDAP (libldap, -lldap)
SYNOPSIS
#include <ldap.h>
int ldap_bind(LDAP *ld, const char *who, const char *cred,
int method);
int ldap_bind_s(LDAP *ld, const char *who, const char *cred,
int method);
int ldap_simple_bind(LDAP *ld, const char *who, const char *passwd);
int ldap_simple_bind_s(LDAP *ld, const char *who, const char *passwd);
int ldap_sasl_bind(LDAP *ld, const char *dn, const char *mechanism,
struct berval *cred, LDAPControl *sctrls[],
LDAPControl *cctrls[], int *msgidp);
int ldap_sasl_bind_s(LDAP *ld, const char *dn, const char *mechanism,
struct berval *cred, LDAPControl *sctrls[],
LDAPControl *cctrls[], struct berval **servercredp);
int ldap_parse_sasl_bind_result(LDAP *ld, LDAPMessage *res,
struct berval **servercredp, int freeit);
int ldap_sasl_interactive_bind_s(LDAP *ld, const char *dn,
const char *mechs,
LDAPControl *sctrls[], LDAPControl *cctrls[],
unsigned flags, LDAP_SASL_INTERACT_PROC *interact,
void *defaults);
int ldap_sasl_interactive_bind(LDAP *ld, const char *dn,
const char *mechs,
LDAPControl *sctrls[], LDAPControl *cctrls[],
unsigned flags, LDAP_SASL_INTERACT_PROC *interact,
void *defaults, LDAPMessage *result,
const char **rmechp, int *msgidp);
int (LDAP_SASL_INTERACT_PROC)(LDAP *ld, unsigned flags, void *defaults, void *sasl_interact);
int ldap_unbind(LDAP *ld);
int ldap_unbind_s(LDAP *ld);
int ldap_unbind_ext(LDAP *ld, LDAPControl *sctrls[],
LDAPControl *cctrls[]);
int ldap_unbind_ext_s(LDAP *ld, LDAPControl *sctrls[],
LDAPControl *cctrls[]);
int ldap_set_rebind_proc (LDAP *ld, LDAP_REBIND_PROC *ldap_proc, void *params);
int (LDAP_REBIND_PROC)(LDAP *ld, LDAP_CONST char *url, ber_tag_t request, ber_int_t msgid, void *params);
DESCRIPTION
These routines provide various interfaces to the LDAP bind operation.
After an association with an LDAP server is made using ldap_init(3), an
LDAP bind operation should be performed before other operations are
attempted over the connection. An LDAP bind is required when using
Version 2 of the LDAP protocol; it is optional for Version 3 but is
usually needed due to security considerations.
There are three types of bind calls, ones providing simple authentica-
tion, ones providing SASL authentication, and general routines capable
of doing either simple or SASL authentication.
SASL (Simple Authentication and Security Layer) can negotiate one of
many different kinds of authentication. Both synchronous and asynchro-
nous versions of each variant of the bind call are provided. All rou-
tines take ld as their first parameter, as returned from ldap_init(3).
SIMPLE AUTHENTICATION
The simplest form of the bind call is ldap_simple_bind_s(). It takes
the DN to bind as in who, and the userPassword associated with the
entry in passwd. It returns an LDAP error indication (see
ldap_error(3)). The ldap_simple_bind() call is asynchronous, taking
the same parameters but only initiating the bind operation and return-
ing the message id of the request it sent. The result of the operation
can be obtained by a subsequent call to ldap_result(3). The
ldap_sasl_bind_s() and asynchronous ldap_sasl_bind() functions can also
be used to make a simple bind by using LDAP_SASL_SIMPLE as the SASL
mechanism.
GENERAL AUTHENTICATION
The ldap_bind() and ldap_bind_s() routines can be used when the authen-
tication method to use needs to be selected at runtime. They both take
an extra method parameter selecting the authentication method to use.
It should be set to LDAP_AUTH_SIMPLE to select simple authentication.
ldap_bind() returns the message id of the request it initiates.
ldap_bind_s() returns an LDAP error indication.
SASL AUTHENTICATION
For SASL binds the server always ignores any provided DN, so the dn
parameter should always be NULL. ldap_sasl_bind_s() sends a single
SASL bind request with the given SASL mechanism and credentials in the
cred parameter. The format of the credentials depends on the particular
SASL mechanism in use. For mechanisms that provide mutual authentica-
tion the server's credentials will be returned in the servercredp
parameter. The routine returns an LDAP error indication (see
ldap_error(3)). The ldap_sasl_bind() call is asynchronous, taking the
same parameters but only sending the request and returning the message
id of the request it sent. The result of the operation can be obtained
by a subsequent call to ldap_result(3). The result must be addition-
ally parsed by ldap_parse_sasl_bind_result() to obtain any server cre-
dentials sent from the server.
Many SASL mechanisms require multiple message exchanges to perform a
complete authentication. Applications should generally use
ldap_sasl_interactive_bind_s() rather than calling the basic
ldap_sasl_bind() functions directly. The mechs parameter should contain
a space-separated list of candidate mechanisms to use. If this parame-
ter is NULL or empty the library will query the supportedSASLMechanisms
attribute from the server's rootDSE for the list of SASL mechanisms the
server supports. The flags parameter controls the interaction used to
retrieve any necessary SASL authentication parameters and should be one
of:
LDAP_SASL_AUTOMATIC
use defaults if available, prompt otherwise
LDAP_SASL_INTERACTIVE
always prompt
LDAP_SASL_QUIET
never prompt
The interact function uses the provided defaults to handle requests
from the SASL library for particular authentication parameters. There
is no defined format for the defaults information; it is up to the
caller to use whatever format is appropriate for the supplied interact
function. The sasl_interact parameter comes from the underlying SASL
library. When used with Cyrus SASL this is an array of sasl_interact_t
structures. The Cyrus SASL library will prompt for a variety of inputs,
including:
SASL_CB_GETREALM
the realm for the authentication attempt
SASL_CB_AUTHNAME
the username to authenticate
SASL_CB_PASS
the password for the provided username
SASL_CB_USER
the username to use for proxy authorization
SASL_CB_NOECHOPROMPT
generic prompt for input with input echoing disabled
SASL_CB_ECHOPROMPT
generic prompt for input with input echoing enabled
SASL_CB_LIST_END
indicates the end of the array of prompts
See the Cyrus SASL documentation for more details.
Applications which need to manage connections asynchronously may use
ldap_sasl_interactive_bind() instead of the synchronous version. A
valid mechs parameter must be supplied, otherwise the library will be
forced to query the server for a list of supported mechanisms, and this
query will be performed synchronously. The other parameters are the
same as for the synchronous function, with three additional parameters.
The actual SASL mechanism that was used, and the message ID for use
with ldap_result() will be returned in rmechp and msgidp, respectively.
The value in rmechp must not be modified by the caller and must be
passed back on each subsequent call. The message obtained from
ldap_result() must be passed in the result parameter. This parameter
must be NULL when initiating a new Bind. The caller must free the
result message after each call using ldap_msgfree(). The
ldap_sasl_interactive_bind() function returns an LDAP result code. If
the code is LDAP_SASL_BIND_IN_PROGRESS then the Bind is not complete
yet, and this function must be called again with the next result from
the server.
REBINDING
The ldap_set_rebind_proc function() sets the process to use for binding
when an operation returns a referral. This function is used when an
application needs to bind to another server in order to follow a refer-
ral or search continuation reference.
The function takes ld, the rebind function, and the params, the arbi-
trary data like state information which the client might need to prop-
erly rebind. The LDAP_OPT_REFERRALS option in the ld must be set to ON
for the libraries to use the rebind function. Use the ldap_set_option
function to set the value.
The rebind function parameters are as follows:
The ld parameter must be used by the application when binding to the
referred server if the application wants the libraries to follow the
referral.
The url parameter points to the URL referral string received from the
LDAP server. The LDAP application can use the ldap_url_parse(3) func-
tion to parse the string into its components.
The request parameter specifies the type of request that generated the
referral.
The msgid parameter specifies the message ID of the request generating
the referral.
The params parameter is the same value as passed originally to the
ldap_set_rebind_proc() function.
The LDAP libraries set all the parameters when they call the rebind
function. The application should not attempt to free either the ld or
the url structures in the rebind function.
The application must supply to the rebind function the required authen-
tication information such as, user name, password, and certificates.
The rebind function must use a synchronous bind method.
UNBINDING
The ldap_unbind() call is used to unbind from the directory, terminate
the current association, and free the resources contained in the ld
structure. Once it is called, the connection to the LDAP server is
closed, and the ld structure is invalid. The ldap_unbind_s() call is
just another name for ldap_unbind(); both of these calls are synchro-
nous in nature.
The ldap_unbind_ext() and ldap_unbind_ext_s() allows the operations to
specify controls.
ERRORS
Asynchronous routines will return -1 in case of error, setting the
ld_errno parameter of the ld structure. Synchronous routines return
whatever ld_errno is set to. See ldap_error(3) for more information.
NOTES
If an anonymous bind is sufficient for the application, the rebind
process need not be provided. The LDAP libraries with the
LDAP_OPT_REFERRALS option set to ON (default value) will automatically
follow referrals using an anonymous bind.
If the application needs stronger authentication than an anonymous
bind, you need to provide a rebind process for that authentication
method. The bind method must be synchronous.
SEE ALSO
ldap(3), ldap_error(3), ldap_open(3), ldap_set_option(3),
ldap_url_parse(3) RFC 4422 (http://www.rfc-editor.org), Cyrus SASL
(http://asg.web.cmu.edu/sasl/)
ACKNOWLEDGEMENTS
OpenLDAP Software is developed and maintained by The OpenLDAP Project
<http://www.openldap.org/>. OpenLDAP Software is derived from the Uni-
versity of Michigan LDAP 3.3 Release.
OpenLDAP 2.4.46 2018/03/22 LDAP_BIND(3)
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