Simple Authentication

The simplest form of the bind call is ldap_simple_bind_s(). The function takes the DN (Distinguished Name) of the dn parameter and the userPassword associated with the entry in passwd to return an LDAP error code. See ldap_error(3LDAP).

The ldap_simple_bind() call is asynchronous. The function takes the same parameters as ldap_simple_bind_s() but initiates the bind operation and returns the message ID of the request sent. The result of the operation can be obtained by a subsequent call to ldap_result(3LDAP).

General Authentication

The ldap_bind() and ldap_bind_s() functions are used to select the authentication method at runtime. Both functions take an extra method parameter to set the authentication method. For simple authentication, the method parameter is set to LDAP_AUTH_SIMPLE. The ldap_bind() function returns the message id of the request initiated. The ldap_bind_s() function returns an LDAP error code.

SASL Authentication

The ldap_sasl_bind() and ldap_sasl_bind_s() functions are used for general and extensible authentication over LDAP through the use of the Simple Authentication Security Layer. The routines both take the DN to bind as the authentication method. A dotted-string representation of an OID identifies the method, and the berval structure holds the credentials. The special constant value LDAP_SASL_SIMPLE ("") can be passed to request simple authentication. Otherwise, the ldap_simple_bind() function or the ldap_simple_bind_s() function can be used.

The ldap_sasl_interactive_bind_s() helper function takes its data and performs the necessary ldap_sasl_bind() and associated SASL library authentication sequencing with the LDAP server that uses the provided connection (ld).

Upon a successful bind, the ldap_sasl_bind() function will, if negotiated by the SASL interface, install the necessary internal libldap plumbing to enable SASL integrity and privacy (over the wire encryption) with the LDAP server.

The LDAP_SASL_INTERACTIVE option flag is passed to the libldap API through the flags argument of the API. The flag tells the API to use the SASL interactive mode and to have the API request SASL authentication data through the LDAP_SASL_INTERACTIVE_PROC callback as needed. The callback provided is in the form:

typedef int (LDAP_SASL_INTERACT_PROC)


    (LDAP *ld, unsigned flags, void* defaults, void *interact);

The user-provided SASL callback is passed to the current LDAP connection pointer, the current flags field, an optional pointer to user-defined data, and the list of sasl_interact_t authentication values requested by libsasl(3LIB) to complete authentication.

The user-defined callback collects and returns the authentication information in the sasl_interact_t array according to libsasl rules. The authentication information can include user IDs, passwords, realms, or other information defined by SASL. The SASL library uses this date during sequencing to complete authentication.

Unbinding

The ldap_unbind() call is used to unbind from a directory, to terminate the current association, and to free the resources contained in the ld structure. Once the function is called, the connection to the LDAP server is closed and the ld structure is invalid. The ldap_unbind_s() and ldap_unbind() calls are identical and synchronous in nature.

The ldap_unbind_ext() function is used to unbind from a directory, to terminate the current association, and to free the resources contained in the LDAP structure. Unlike ldap_unbind() and ldap_unbind_s(), both server and client controls can be explicitly included with ldap_unbind_ext() requests. No server response is made to an unbind request and responses should not be expected from server controls included with unbind requests.

Rebinding While Following Referral

The ldap_set_rebind_proc() call is used to set a function called back to obtain bind credentials. The credentials are used when a new server is contacted after an LDAP referral. If ldap_set_rebind_proc() is never called, or if it is called with a NULL rebindproc parameter, an unauthenticated simple LDAP bind is always done when chasing referrals.

The rebindproc() function is declared as shown below:

int rebindproc(LDAP *ld, char **whop, char **credp,


    int *methodp, int freeit);

The LDAP library first calls the rebindproc() to obtain the referral bind credentials. The freeit parameter is zero. The whop, credp, and methodp parameters should be set as appropriate. If rebindproc() returns LDAP_SUCCESS, referral processing continues. The rebindproc() is called a second time with a non-zero freeit value to give the application a chance to free any memory allocated in the previous call.

If anything but LDAP_SUCCESS is returned by the first call to rebindproc(), referral processing is stopped and the error code is returned for the original LDAP operation.