The LDAP module implements an LDAP search interface for Kamailio. It exports script functions to perform an LDAP search operation and to store the search results as Kamailio AVPs. This allows for using LDAP directory data in the Kamailio SIP message routing script.

The following features are offered by the LDAP module:

LDAP search function taking an LDAP URL as input
LDAP result parsing functions to store LDAP data as AVP
Support for accessing multiple LDAP servers
LDAP SIMPLE authentication
LDAP server failover and automatic reconnect
Configurable LDAP connection and bind timeouts
Module API for LDAP search operations that can be used by other Kamailio modules

The module implementation makes use of the open source OpenLDAP library available on most UNIX/Linux platforms. Besides LDAP server failover and automatic reconnect, this module can handle multiple LDAP sessions concurrently allowing to access data stored on different LDAP servers. Each Kamailio worker process maintains one LDAP TCP connection per configured LDAP server. This enables parallel execution of LDAP requests and offloads LDAP concurrency control to the LDAP server(s).

An LDAP search module API is provided that can be used by other Kamailio modules. A module using this API does not have to implement LDAP connection management and configuration, while still having access to the full OpenLDAP API for searching and result handling.

Since LDAP server implementations are optimized for fast read access they are a good choice to store SIP provisioning data. Performance tests have shown that this module achieves lower data access times and higher call rates than other database modules like e.g. the Kamailio MYSQL module.

1.1. Usage Basics

First so called LDAP sessions have to be specified in an external configuration file (as described in Section 3, “LDAP Configuration File”). Each LDAP session includes LDAP server access parameters like server hostname or connection timeouts. Normally only a single LDAP session will be used unless there is a need to access more than one LDAP server. The LDAP session name will then be used in the Kamailio configuration script to refer to a specific LDAP session.

The ldap_search function (Section 5.1, “ldap_search(ldap_url)”) performs an LDAP search operation. It expects an LDAP URL as input which includes the LDAP session name and search parameters. Section 1.2, “LDAP URLs” provides a quick overview on LDAP URLs.

The result of an LDAP search is stored internally and can be accessed with one of the ldap_result* functions. ldap_result (Section 5.2, “ldap_result("ldap_attr_name/avp_spec[/avp_type]" [, regex_subst])”) stores resulting LDAP attribute value as AVPs. ldap_result_check (Section 5.3, “ldap_result_check("ldap_attr_name/string_to_match" [, regex_subst])”) is a convenience function to compare a string with LDAP attribute values using regular expression matching. Finally, ldap_result_next (Section 5.4, “ldap_result_next()”) allows to handle LDAP search queries that return more than one LDAP entry.

All ldap_result* functions do always access the LDAP result set from the last ldap_search call. This should be kept in mind when calling ldap_search more than once in the Kamailio configuration script.

1.2. LDAP URLs

ldap_search expects an LDAP URL as argument. This section describes the format and semantics of an LDAP URL.

RFC 4516 [RFC4516] describes the format of an LDAP Uniform Resource Locator (URL). An LDAP URL represents an LDAP search operation in a compact format. The LDAP URL format is defined as follows (slightly modified, refer to section 2 of [RFC4516] for ABNF notation):

ldap://[ldap_session_name][/dn?attrs[?scope[?filter]]]]

ldap_session_name

An LDAP session name as defined in the LDAP configuration file.

(RFC 4516 defines this as LDAP hostport parameter)

dn

Base Distinguished Name (DN) of LDAP search or target of non-search operation, as defined in RFC 4514 [RFC4514]

attrs

Comma separated list of LDAP attributes to be returned

scope

Scope for LDAP search, valid values are “base”, “one”, or “sub”

filter

LDAP search filter definition following rules of RFC 4515 [RFC4515]

Note

The following table lists characters that have to be escaped in LDAP search filters:

Table 1.1. RFC 4515 Escaping Rules

`*`	`\2a`
`(`	`\28`
`)`	`\29`
`\`	`\5c`

Note

Non-URL characters in an LDAP URL have to be escaped using percent-encoding (refer to section 2.1 of RFC 4516). In particular this means that any "?" character in an LDAP URL component must be written as "%3F", since "?" is used as a URL delimiter.

The exported function ldap_filter_url_encode (Section 5.5, “ldap_filter_url_encode(string, avp_spec)”) implements RFC 4515/4516 LDAP search filter and URL escaping rules.

2. Dependencies

2.1. Kamailio Modules

The module depends on the following modules (the listed modules must be loaded before this module):

No dependencies on other Kamailio modules.

2.2. External Libraries or Applications

The following libraries or applications must be installed before running Kamailio with this module loaded:

OpenLDAP library (libldap) v2.1 or greater, libldap header files (libldap-dev) are needed for compilation

OpenSSL library if you compile your OpenLDAP library with SSL/TLS support.

3. LDAP Configuration File

The module reads an external configuration file at module initialization time that includes LDAP session definitions.

3.1. Configuration File Syntax

The configuration file follows the Windows INI file syntax, section names are enclosed in square brackets:

[Section_Name]

Any section can contain zero or more configuration key assignments of the form

key = value ; comment

Values can be given enclosed with quotes. If no quotes are present, the value is understood as containing all characters between the first and the last non-blank characters. Lines starting with a hash sign and blank lines are treated as comments.

Each section describes one LDAP session that can be referred to in the Kamailio configuration script. Using the section name as the host part of an LDAP URL tells the module to use the LDAP session specified in the respective section. An example LDAP session specification looks like:

[example_ldap]
ldap_server_url            = "ldap://ldap1.example.com, ldap://ldap2.example.com"
ldap_bind_dn               = "cn=sip_proxy,ou=accounts,dc=example,dc=com"
ldap_bind_password         = "pwd"
ldap_network_timeout       = 500
ldap_client_bind_timeout   = 500

The configuration keys are explained in the following section. This LDAP session can be referred to in the routing script by using an LDAP URL like e.g.

ldap://example_ldap/cn=admin,dc=example,dc=com

3.2. LDAP Session Settings

ldap_server_url (mandatory)

LDAP URL including fully qualified domain name or IP address of LDAP server optionally followed by a colon and TCP port to connect: ldap://<FQDN/IP>[:<port>]. Failover LDAP servers can be added, each separated by a comma. In the event of connection errors, the module tries to connect to servers in order of appearance. To connect over TLS/SSL, use ldaps://.

Default value: none, this is a mandatory setting

Example 1.1. ldap_server_url examples

ldap_server_url = "ldap://localhost"
ldap_server_url = "ldaps://ldap.example.com:7777"
ldap_server_url = "ldap://ldap1.example.com, 
                   ldap://ldap2.example.com:80389"

ldap_version (optional)

Supported LDAP versions are 2 and 3.

Default value: 3 (LDAPv3)

Example 1.2. ldap_version example

ldap_version = 2

ldap_bind_dn (optional)

Authentication user DN used to bind to LDAP server (module currently only supports SIMPLE_AUTH). Empty string enables anonymous LDAP bind.

Default value: “” (empty string --> anonymous bind)

Example 1.3. ldap_bind_dn example

ldap_bind_dn = "cn=root,dc=example,dc=com";

ldap_bind_password (optional)

Authentication password used to bind to LDAP server (SIMPLE_AUTH). Empty string enables anonymous bind.

Default value: “” (empty string --> anonymous bind)

Example 1.4. ldap_bind_password example

ldap_bind_password = "secret";

ldap_network_timeout (optional)

LDAP TCP connect timeout in milliseconds. Setting this parameter to a low value enables fast failover if ldap_server_url contains more than one LDAP server addresses.

Default value: 1000 (one second)

Example 1.5. ldap_network_timeout example

ldap_network_timeout = 500 ; setting TCP timeout to 500 ms

ldap_client_bind_timeout (optional)

LDAP bind operation timeout in milliseconds.

Default value: 1000 (one second)

Example 1.6. ldap_client_bind_timeout example

ldap_client_bind_timeout = 1000

3.3. Configuration File Example

The following configuration file example includes two LDAP session definitions that could be used e.g. for accessing H.350 data and do phone number to name mappings.

Example 1.7. Example LDAP Configuration File

# LDAP session "sipaccounts":
#
# - using LDAPv3 (default)
# - two redundant LDAP servers
#
[sipaccounts]
ldap_server_url = "ldap://h350-1.example.com, ldap://h350-2.example.com"
ldap_bind_dn = "cn=sip_proxy,ou=accounts,dc=example,dc=com"
ldap_bind_password = "pwd"
ldap_network_timeout = 500
ldap_client_bind_timeout = 500


# LDAP session "campus":
#
# - using LDAPv2
# - anonymous bind
#
[campus]
ldap_version = 2
ldap_server_url = "ldap://ldap.example.com"
ldap_network_timeout = 500
ldap_client_bind_timeout = 500

4. Parameters

4.1. config_file (string)

Full path to LDAP configuration file.

Default value: /usr/local/etc/kamailio/ldap.cfg

Example 1.8. config_file parameter usage

modparam("ldap", "config_file", "/usr/local/etc/kamailio/ldap.ini")

5. Functions

5.1. ldap_search(ldap_url)

Performs an LDAP search operation using given LDAP URL and stores result internally for later retrieval by ldap_result* functions. If one or more LDAP entries are found the function returns the number of found entries which evaluates to TRUE in the Kamailio configuration script. It returns -1 (FALSE) in case no LDAP entry was found, and -2 (FALSE) if an internal error like e.g. an LDAP error occurred.

Function Parameters:

ldap_url

An LDAP URL defining the LDAP search operation (refer to Section 1.2, “LDAP URLs” for a description of the LDAP URL format). The hostport part must be one of the LDAP session names declared in the LDAP configuration script.

Kamailio pseudo variables and AVPs included in ldap_url do get substituted with their value.

Example 1.9. Example Usage of ldap_url

Search with LDAP session named sipaccounts, base ou=sip,dc=example,dc=com, one level deep using search filter (cn=schlatter) and returning all attributes:

ldap://sipaccounts/ou=sip,dc=example,dc=com??one?(cn=schlatter)

Subtree search with LDAP session named ldap1, base dc=example,dc=com using search filter (cn=$(avp(s:name))) and returning SIPIdentityUserName and SIPIdentityServiceLevel attributes

ldap://ldap_1/dc=example,dc=com?
       SIPIdentityUserName,SIPIdentityServiceLevel?sub?(cn=$(avp(s:name)))

Return Values:

n > 0 (TRUE):

Found n matching LDAP entries

-1 (FALSE):

No matching LDAP entries found

-2 (FALSE):

LDAP error (e.g. LDAP server unavailable), or
internal error

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE.

Example 1.10. Example Usage

...
# ldap search
if (!ldap_search("ldap://sipaccounts/ou=sip,dc=example,dc=com??one?(cn=$rU)"))
{
    switch ($retcode)
    {
    case -1:
        # no LDAP entry found
        sl_send_reply("404", "User Not Found");
        exit;
    case -2:
        # internal error
        sl_send_reply("500", "Internal server error");
        exit;
    default:
        exit;
    }
}
xlog("L_INFO", "ldap_search: found [$retcode] entries for (cn=$rU)");

# save telephone number in $avp(s:tel_number)
ldap_result("telephoneNumber/$avp(s:tel_number)");
...

5.2. ldap_result("ldap_attr_name/avp_spec[/avp_type]" [, regex_subst])

This function converts LDAP attribute values into AVPs for later use in the message routing script. It accesses the LDAP result set fetched by the last ldap_search call. ldap_attr_name specifies the LDAP attribute name who's value should be stored in AVP avp_spec. Multi valued LDAP attributes generate an indexed AVP. The optional regex_subst parameter allows to further define what part of an attribute value should be stored as AVP.

An AVP can either be of type string or integer. As default, ldap_result stores LDAP attribute values as AVP of type string. The optional avp_type parameter can be used to explicitly specify the type of the AVP. It can be either str for string, or int for integer. If avp_type is specified as int then ldap_result tries to convert the LDAP attribute values to integer. In this case, the values are only stored as AVP if the conversion to integer is succesfull.

Function Parameters:

ldap_attr_name: The name of the LDAP attribute who's value should be stored, e.g. SIPIdentityServiceLevel or telephonenumber
avp_spec: Specification of destination AVP, e.g. $avp(s:service_level) or $avp(i:12)
avp_type: Opional specification of destination AVP type, either str or int. If this parameter is not specified then the LDAP attribute values are stored as AVP of type string.
regex_subst: Regex substitution that gets applied to LDAP attribute value before storing it as AVP, e.g. "/^sip:(.+)$/\1/" to strip off "sip:" from the beginning of an LDAP attribute value.

Return Values:

n > 0 (TRUE): LDAP attribute ldap_attr_name found in LDAP result set and n LDAP attribute values stored in avp_spec
-1 (FALSE): No LDAP attribute ldap_attr_name found in LDAP result set
-2 (FALSE): Internal error occurred

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE.

Example 1.11. Example Usage

...

# ldap_search call
...

# save SIPIdentityServiceLevel in $avp(s:service_level)
if (!ldap_result("SIPIdentityServiceLevel/$avp(s:service_level)"))
{
    switch ($retcode)
    {
    case -1:
        # no SIPIdentityServiceLevel found
        sl_send_reply("403", "Forbidden");
        exit;
    case -2:
        # internal error
        sl_send_reply("500", "Internal server error");
        exit;
    default: 
        exit;
    }
}

# save SIP URI domain in $avp(i:10)
ldap_result("SIPIdentitySIPURI/$avp(i:10)", "/^[^@]+@(.+)$/\1/");
...

5.3. ldap_result_check("ldap_attr_name/string_to_match" [, regex_subst])

This function compares ldap_attr_name's value with string_to_match for equality. It accesses the LDAP result set fetched by the last ldap_search call. The optional regex_subst parameter allows to further define what part of the attribute value should be used for the equality match. If ldap_attr_name is multi valued, each value is checked against string_to_match. If one or more of the values do match the function returns 1 (TRUE).

Function Parameters:

ldap_attr_name: The name of the LDAP attribute who's value should be matched, e.g. SIPIdentitySIPURI
string_to_match: String to be matched. Included AVPs and pseudo variabels do get expanded.
regex_subst: Regex substitution that gets applied to LDAP attribute value before comparing it with string_to_match, e.g. "/^[^@]@+(.+)$/\1/" to extract the domain part of a SIP URI

Return Values:

1 (TRUE): One or more ldap_attr_name attribute values match string_to_match (after regex_subst is applied)
-1 (FALSE): ldap_attr_name attribute not found or attribute value doesn't match string_to_match (after regex_subst is applied)
-2 (FALSE): Internal error occurred

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE.

Example 1.12. Example Usage

...
# ldap_search call
...

# check if 'sn' ldap attribute value equals username part of R-URI,
# the same could be achieved with ldap_result_check("sn/$rU")
if (!ldap_result_check("sn/$ru", "/^sip:([^@]).*$/\1/"))
{
    switch ($retcode)
    {
    case -1:
        # R-URI username doesn't match sn
        sl_send_reply("401", "Unauthorized");
        exit;
    case -2:
        # internal error
        sl_send_reply("500", "Internal server error");
        exit;
    default:
        exit;
    }
}
...

5.4. ldap_result_next()

An LDAP search operation can return multiple LDAP entries. This function can be used to cycle through all returned LDAP entries. It returns 1 (TRUE) if there is another LDAP entry present in the LDAP result set and causes ldap_result* functions to work on the next LDAP entry. The function returns -1 (FALSE) if there are no more LDAP entries in the LDAP result set.

Return Values:

1 (TRUE): Another LDAP entry is present in the LDAP result set and result pointer is incremented by one
-1 (FALSE): No more LDAP entries are available
-2 (FALSE): Internal error

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE.

Example 1.13. Example Usage

...
# ldap_search call
...

ldap_result("telephonenumber/$avp(s:tel1)");
if (ldap_result_next())
{
	ldap_result("telephonenumber/$avp(s:tel2)");
}
if (ldap_result_next())
{
	ldap_result("telephonenumber/$avp(s:tel3)");
}
if (ldap_result_next())
{
	ldap_result("telephonenumber/$avp(s:tel4)");
}	
...

5.5. ldap_filter_url_encode(string, avp_spec)

This function applies the following escaping rules to string and stores the result in AVP avp_spec:

Table 1.2. ldap_filter_url_encode() escaping rules

character in `string`	gets replaced with	defined in
*	\2a	RFC 4515
(	\28	RFC 4515
)	\29	RFC 4515
\	\5c	RFC 4515
?	%3F	RFC 4516

The string stored in AVP avp_spec can be safely used in an LDAP URL filter string.

Function Parameters:

string: String to apply RFC 4515 and URL escpaing rules to. AVPs and pseudo variables do get expanded. Example: "cn=$avp(s:name)"
avp_spec: Specification of AVP to store resulting RFC 4515 and URL encoded string, e.g. $avp(s:ldap_search) or $avp(i:10)

Return Values:

1 (TRUE): RFC 4515 and URL encoded filter_component stored as AVP avp_name
-1 (FALSE): Internal error

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE.

Example 1.14. Example Usage

...
if (!ldap_filter_url_encode("cn=$avp(s:name)", "$avp(s:name_esc)"))
{
    # RFC 4515/URL encoding failed --> silently discard request
    exit;
}

xlog("L_INFO", "encoded LDAP filter component: [$avp(s:name_esc)]\n");

if (ldap_search(
     "ldap://h350/ou=commObjects,dc=example,dc=com??sub?($avp(s:name_esc))")) 
    { ... }
...

6. Installation & Running

6.1. Compiling the Module

OpenLDAP library (libldap) and header files (libldap-dev) v2.1 or greater (this module was tested with v2.1.3 and v2.3.32) are required for compiling the LDAP module. The OpenLDAP source is available at http://www.openldap.org/. Note that TLS support needs to be added a compile time for the libraries.

The OpenLDAP library is available pre-compiled for most UNIX/Linux flavors. On Debian/Ubuntu, the following packages must be installed:

# apt-get install libldap2 libldap2-dev

Chapter 2. Developer Guide

Table of Contents

1. Overview

2. API Functions

2.1. ldap_params_search
2.2. ldap_url_search
2.3. ldap_result_attr_vals
2.4. ldap_value_free_len
2.5. ldap_result_next
2.6. ldap_str2scope
2.7. ldap_rfc4515_escape
2.8. get_ldap_handle
2.9. get_last_ldap_result

3. Example Usage

1. Overview

The LDAP module API can be used by other Kamailio modules to implement LDAP search functionality. This frees the module implementer from having to care about LDAP connection management and configuration.

In order to use this API, a module has to load the API using the load_ldap_api function which returns a pointer to a ldap_api structure. This structure includes pointers to the API functions described below. The LDAP module source file api.h includes all declarations needed to load the API, it has to be included in the file that use the API. Loading the API is typically done inside a module's mod_init call as the following example shows:

Example 2.1. Example code fragment to load LDAP module API

#include "../../sr_module.h"
#include "../ldap/api.h"

/*
 * global pointer to ldap api
 */
extern ldap_api_t ldap_api;

...

static int mod_init(void)
{
    /*
     * load the LDAP API
     */
    if (load_ldap_api(&ldap_api) != 0)
    {
        LM_ERR("Unable to load LDAP API - this module requires ldap module\n");
        return -1;
    }

    ...
}

...

The API functions can then be used like in the following example:

Example 2.2. Example LDAP module API function call

...
	
    rc = ldap_api.ldap_rfc4515_escape(str1, str2, 0);	
				
...

2. API Functions

2.1. ldap_params_search

Performs an LDAP search using the parameters given as function arguments.

typedef int (*ldap_params_search_t)(int* _ld_result_count,
                                    char* _lds_name,
                                    char* _dn,
                                    int _scope,
                                    char** _attrs,
                                    char* _filter,
                                    ...);

Function arguments:

int* _ld_result_count: The function stores the number of returned LDAP entries in _ld_result_count.
char* _lds_name: LDAP session name as configured in the LDAP module configuration file.
char* _dn: LDAP search DN.
int _scope: LDAP search scope, one of LDAP_SCOPE_ONELEVEL, LDAP_SCOPE_BASE, or LDAP_SCOPE_SUBTREE, as defined in OpenLDAP's ldap.h.
char** _attrs: A null-terminated array of attribute types to return from entries. If empty (NULL), all attribute types are returned.
char* _filter: LDAP search filter string according to RFC 4515. printf patterns in this string do get replaced with the function arguments' values following the _filter argument.

Return Values:

-1: Internal error.
0: Success, _ld_result_count includes the number of LDAP entries found.

2.2. ldap_url_search

Performs an LDAP search using an LDAP URL.

typedef int (*ldap_url_search_t)(char* _ldap_url,
                                 int* _result_count);

Function arguments:

char* _ldap_url: LDAP URL as described in Section 1.2, “LDAP URLs”.
int* _result_count: The function stores the number of returned LDAP entries in _ld_result_count.

Return Values:

-1: Internal error.
0: Success, _ld_result_count includes the number of LDAP entries found.

2.3. ldap_result_attr_vals

Retrieve the value(s) of a returned LDAP attribute. The function accesses the LDAP result returned by the last call of ldap_params_search or ldap_url_search. The berval structure is defined in OpenLDAP's ldap.h, which has to be included.

This function allocates memory to store the LDAP attribute value(s). This memory has to freed with the function ldap_value_free_len (see next section).

typedef int (*ldap_result_attr_vals_t)(str* _attr_name,
                                       struct berval ***_vals);
									   
typedef struct berval {
        ber_len_t       bv_len;
        char            *bv_val;
} BerValue;

Function arguments:

str* _attr_name: str structure holding the LDAP attribute name.
struct berval ***_vals: A null-terminated array of the attribute's value(s).

Return Values:

-1: Internal error.
0: Success, _vals includes the attribute's value(s).
1: No attribute value found.

2.4. ldap_value_free_len

Function used to free memory allocated by ldap_result_attr_vals. The berval structure is defined in OpenLDAP's ldap.h, which has to be included.

typedef void (*ldap_value_free_len_t)(struct berval **_vals);

typedef struct berval {
        ber_len_t       bv_len;
        char            *bv_val;
} BerValue;

Function arguments:

struct berval **_vals: berval array returned by ldap_result_attr_vals.

2.5. ldap_result_next

Increments the LDAP result pointer.

typedef int (*ldap_result_next_t)();

Return Values:

-1: No LDAP result found, probably because ldap_params_search or ldap_url_search was not called.
0: Success, LDAP result pointer points now to next result.
1: No more results available.

2.6. ldap_str2scope

Converts LDAP search scope string into integer value e.g. for ldap_params_search.

typedef int (*ldap_str2scope_t)(char* scope_str);

Function arguments:

char* scope_str: LDAP search scope string. One of "one", "onelevel", "base", "sub", or "subtree".

Return Values:

-1: scope_str not recognized.
n >= 0: LDAP search scope integer.

2.7. ldap_rfc4515_escape

Applies escaping rules described in Section 5.5, “ldap_filter_url_encode(string, avp_spec)”.

typedef int (*ldap_rfc4515_escape_t)(str *sin, str *sout, int url_encode);

Function arguments:

str *sin: str structure holding the string to apply the escaping rules.
str *sout: str structure holding the escaped string. The length of this string must be at least three times the length of sin plus one.
int url_encode: Flag that specifies if a '?' character gets escaped with '%3F' or not. If url_encode equals 0, '?' does not get escaped.

Return Values:

-1: Internal error.
0: Success, sout contains escaped string.

2.8. get_ldap_handle

Returns the OpenLDAP LDAP handle for a specific LDAP session. This allows a module implementor to use the OpenLDAP API functions directly, instead of using the API functions exported by the Kamailio LDAP module. The LDAP structure is defined in OpenLDAP's ldap.h, which has to be included.

typedef int (*get_ldap_handle_t)(char* _lds_name, LDAP** _ldap_handle);

Function arguments:

char* _lds_name: LDAP session name as specified in the LDAP module configuration file.
LDAP** _ldap_handle: OpenLDAP LDAP handle returned by this function.

Return Values:

-1: Internal error.
0: Success, _ldap_handle contains the OpenLDAP LDAP handle.

2.9. get_last_ldap_result

Returns the OpenLDAP LDAP handle and OpenLDAP result handle of the last LDAP search operation. These handles can be used as input for OpenLDAP LDAP result API functions. LDAP and LDAPMessage structures are defined in OpenLDAP's ldap.h, which has to be included.

typedef void (*get_last_ldap_result_t)
	     (LDAP** _last_ldap_handle, LDAPMessage** _last_ldap_result);

Function arguments:

LDAP** _last_ldap_handle: OpenLDAP LDAP handle returned by this function.
LDAPMessage** _last_ldap_result: OpenLDAP result handle returned by this function.

3. Example Usage

The following example shows how this API can be used to perform an LDAP search operation. It is assumed that the API is loaded and available through the ldap_api pointer.

...
	
int rc, ld_result_count, scope = 0;
char* sip_username = "test";

/*
 * get LDAP search scope integer
 */
scope = ldap_api.ldap_str2scope("sub");
if (scope == -1)
{
    LM_ERR("ldap_str2scope failed\n");
    return -1;
}

/*
 * perform LDAP search
 */

if (ldap_api.ldap_params_search(
       &ld_result_count,
       "campus",
       "dc=example,dc=com",
       scope,
       NULL,
       "(&(objectClass=SIPIdentity)(SIPIdentityUserName=%s))",
       sip_username)
     != 0)
{
    LM_ERR("LDAP search failed\n");
    return -1;
}

/*
 * check result count
 */
if (ld_result_count < 1)
{
    LM_ERR("LDAP search returned no entry\n");
    return 1;
}

/*
 * get password attribute value 
 */
 
struct berval **attr_vals = NULL;
str ldap_pwd_attr_name = str_init("SIPIdentityPassword");
str res_password;

rc = ldap_api.ldap_result_attr_vals(&ldap_pwd_attr_name, &attr_vals);
if (rc < 0)
{
    LM_ERR("ldap_result_attr_vals failed\n");
    ldap_api.ldap_value_free_len(attr_vals);
    return -1;
}
if (rc == 1)
{
    LM_INFO("No password attribute value found for [%s]\n", sip_username);
    ldap_api.ldap_value_free_len(attr_vals);
    return 2;
}

res_password.s = attr_vals[0]->bv_val;
res_password.len = attr_vals[0]->bv_len;

ldap_api.ldap_value_free_len(attr_vals);

LM_INFO("Password for user [%s]: [%s]\n", sip_username, res_password.s);

...

return 0;

Resources

[RFC4510] Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map. June 2006. Internet Engineering Task Force.

[RFC4511] Lightweight Directory Access Protocol (LDAP): The Protocol. June 2006. Internet Engineering Task Force.

[RFC4514] Lightweight Directory Access Protocol (LDAP): String Representation of Distinguished Names. June 2006. Internet Engineering Task Force.

[RFC4515] Lightweight Directory Access Protocol (LDAP): String Representation of Search Filters. June 2006. Internet Engineering Task Force.

[RFC4516] Lightweight Directory Access Protocol (LDAP): Uniform Resource Locator. June 2006. Internet Engineering Task Force.

[RFC2617] HTTP Authentication: Basic and Digest Access Authentication. June 1999. Internet Engineering Task Force.

[RFC3261] SIP: Session Initiation Protocol. June 2002. Internet Engineering Task Force.

[H.350] Directory Services Architecture for Multimedia Conferencing. August 2003. ITU-T.

[H.350.4] Directory services architecture for SIP. August 2003. ITU-T.