# &adminguide;

## Overview

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 based on a LDAP URL

- LDAP result parsing functions to store LDAP data as AVP variables

- 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 access to 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.

### Usage Basics

LDAP sessions is specified in an external configuration file (as described in ). Each of these LDAP sessions includes LDAP server access parameters like server hostname or connection timeouts. Normally only a single LDAP session per process 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 () performs an LDAP search operation. It expects an LDAP URL as input which includes the LDAP session name and search parameters. The section provides a quick overview on LDAP URLs.

The result of a LDAP search is stored internally and can be accessed with one of the `ldap_result*` functions. `ldap_result` () stores resulting LDAP attribute values as AVPs. `ldap_result_check` () is a convenience function to compare a string with LDAP attribute values using regular expression matching. Finally, `ldap_result_next` () allows using LDAP search queries that return more than one LDAP entry.

All `ldap_result*` functions 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.

### LDAP URLs

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

RFC 4516 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 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

`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

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

  #### RFC 4515 Escaping Rules

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

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` () implements RFC 4515/4516 LDAP search filter and URL escaping rules.

## Dependencies

### &kamailio; Modules

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

- No dependencies on other &kamailio; modules.

### 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.

## LDAP Configuration File

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

### 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

### 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

  #### `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)

  #### `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)

  #### `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)

  #### `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)

  #### `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)

  #### `ldap_client_bind_timeout` example

      ldap_client_bind_timeout = 1000

### 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 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

## Parameters

### `config_file` (string)

Full path to LDAP configuration file.

Default value: `/usr/local/etc/&kamailiobinary;/ldap.cfg`

#### `config_file` parameter usage

    modparam("ldap", "config_file", "/usr/local/etc/&kamailiobinary;/ldap.ini")

### `connect_mode` (int)

Control if the module must stop loading when connecting to server fails during start up. Values: 0 - stop loading; 1 - continue even if connecting to database server fails..

Default value: `0`

#### Set `connect_mode` parameter

    modparam("ldap", "connect_mode", 1)

## Functions

### 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 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 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 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)");
    ...

### 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 will 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 successful.

#### 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

  Optional 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 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/");
    ...

### 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 variables 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 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;
        }
    }
    ...

### 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 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)");
    }
    ...

### ldap_filter_url_encode(string, avp_spec)

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

#### 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 escaping 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 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))"))
        { ... }
    ...

## Installation & Running

### Compiling the LDAP 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

.