Authenticating against an LDAP server

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Symfony provides different means to work with an LDAP server.

The Security component offers:

The ldap user provider, using the LdapUserProvider class. Like all other user providers, it can be used with any authentication provider.
The form_login_ldap authentication provider, for authenticating against an LDAP server using a login form. Like all other authentication providers, it can be used with any user provider.
The http_basic_ldap authentication provider, for authenticating against an LDAP server using HTTP Basic. Like all other authentication providers, it can be used with any user provider.

This means that the following scenarios will work:

Checking a user's password and fetching user information against an LDAP server. This can be done using both the LDAP user provider and either the LDAP form login or LDAP HTTP Basic authentication providers.
Checking a user's password against an LDAP server while fetching user information from another source (database using FOSUserBundle, for example).
Loading user information from an LDAP server, while using another authentication strategy (token-based pre-authentication, for example).

Ldap Configuration Reference

See Security Configuration Reference (SecurityBundle) for the full LDAP configuration reference (form_login_ldap, http_basic_ldap, ldap). Some of the more interesting options are explained below.

Configuring the LDAP client

All mechanisms actually need an LDAP client previously configured. The providers are configured to use a default service named ldap, but you can override this setting in the security component's configuration.

An LDAP client can be simply configured, using the following service definition:

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        # app/config/services.yml
services:
    ldap:
        class: Symfony\Component\Ldap\LdapClient
        arguments:
            - my-server   # host
            - 389         # port
            - 3           # version
            - false       # SSL
            - true        # TLS
    

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        <!-- app/config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="ldap" class="Symfony\Component\Ldap\LdapClient">
            <argument>my-server</argument>
            <argument>389</argument>
            <argument>3</argument>
            <argument>false</argument>
            <argument>true</argument>
        </service>
    </services>
</container>
    

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        // app/config/services.php
use Symfony\Component\Ldap\LdapClient;
use Symfony\Component\DependencyInjection\Definition;

$container
    ->setDefinition('ldap', new Definition(LdapClient::class, array(
        'my-server',
        389,
        3,
        false,
        true,

    ));
    

Fetching Users Using the LDAP User Provider

If you want to fetch user information from an LDAP server, you may want to use the ldap user provider.

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        # app/config/security.yml
security:
    # ...

    providers:
        my_ldap:
            ldap:
                service: ldap
                base_dn: dc=example,dc=com
                search_dn: "cn=read-only-admin,dc=example,dc=com"
                search_password: password
                default_roles: ROLE_USER
                uid_key: uid
    

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        <!-- app/config/security.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<srv:container xmlns="http://symfony.com/schema/dic/security"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:srv="http://symfony.com/schema/dic/services"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <config>
        <provider name="my_ldap">
            <ldap
                    service="ldap"
                    base-dn="dc=example,dc=com"
                    search-dn="cn=read-only-admin,dc=example,dc=com"
                    search-password="password"
                    default-roles="ROLE_USER"
                    uid-key="uid"
            />
        </provider>
    </config>
</srv:container>
    

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        $container->loadFromExtension('security', array(
    'providers' => array(
        'ldap_users' => array(
            'ldap' => array(
                'service' => 'ldap',
                'base_dn' => 'dc=example,dc=com',
                'search_dn' => 'cn=read-only-admin,dc=example,dc=com',
                'search_password' => 'password',
                'default_roles' => 'ROLE_USER',
                'uid_key' => 'uid',
            ),
        ),
    ),
);
    

Caution

The Security component escapes provided input data when the LDAP user provider is used. However, the LDAP component itself does not provide any escaping yet. Thus, it's your responsibility to prevent LDAP injection attacks when using the component directly.

Caution

The user configured above in the the user provider is only used to retrieve data. It's a static user defined by its username and password (for improved security, define the password as an environment variable).

If your LDAP server allows to retrieve information anonymously, you can set the search_dn and search_password options to null.

The ldap user provider supports many different configuration options:

service

type: string default: ldap

This is the name of your configured LDAP client. You can freely chose the name, but it must be unique in your application and it cannot start with a number or contain white spaces.

base_dn

type: string default: null

This is the base DN for the directory

search_dn

type: string default: null

This is your read-only user's DN, which will be used to authenticate against the LDAP server in order to fetch the user's information.

search_password

type: string default: null

This is your read-only user's password, which will be used to authenticate against the LDAP server in order to fetch the user's information.

default_roles

type: array default: []

This is the default role you wish to give to a user fetched from the LDAP server. If you do not configure this key, your users won't have any roles, and will not be considered as authenticated fully.

uid_key

type: string default: sAMAccountName

This is the entry's key to use as its UID. Depends on your LDAP server implementation. Commonly used values are:

sAMAccountName
userPrincipalName
uid

filter

type: string default: ({uid_key}={username})

This key lets you configure which LDAP query will be used. The {uid_key} string will be replaced by the value of the uid_key configuration value (by default, sAMAccountName), and the {username} string will be replaced by the username you are trying to load.

For example, with a uid_key of uid, and if you are trying to load the user fabpot, the final string will be: (uid=fabpot).

Of course, the username will be escaped, in order to prevent LDAP injection.

The syntax for the filter key is defined by RFC4515.

For example, if your users have DN strings in the form uid=einstein,dc=example,dc=com, then the dn_string will be uid={username},dc=example,dc=com.

Examples are provided below, for both form_login_ldap and http_basic_ldap.

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        # app/config/security.yml
security:
    # ...

    firewalls:
        main:
            # ...
            form_login_ldap:
                login_path: login
                check_path: login_check
                # ...
                service: ldap
                dn_string: 'uid={username},dc=example,dc=com'
    

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        <!-- app/config/security.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<srv:container xmlns="http://symfony.com/schema/dic/security"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:srv="http://symfony.com/schema/dic/services"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <config>
        <firewall name="main">
            <form-login-ldap
                    login-path="login"
                    check-path="login_check"
                    service="ldap"
                    dn-string="uid={username},dc=example,dc=com" />
        </firewall>
    </config>
</srv:container>
    

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        $container->loadFromExtension('security', array(
    'firewalls' => array(
        'main' => array(
            'form_login_ldap' => array(
                'login_path' => 'login',
                'check_path' => 'login_check',
                'service' => 'ldap',
                'dn_string' => 'uid={username},dc=example,dc=com',
                // ...
            ),
        ),
    )
);
    

Configuration example for HTTP Basic

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        # app/config/security.yml
security:
    # ...

    firewalls:
        main:
            # ...
            http_basic_ldap:
                # ...
                service: ldap
                dn_string: 'uid={username},dc=example,dc=com'
    

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        <!-- app/config/security.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<srv:container xmlns="http://symfony.com/schema/dic/security"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:srv="http://symfony.com/schema/dic/services"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <config>
        <firewall name="main" stateless="true">
            <http-basic-ldap service="ldap" dn-string="uid={username},dc=example,dc=com" />
        </firewall>
    </config>
</srv:container>
    

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        $container->loadFromExtension('security', array(
    'firewalls' => array(
        'main' => array(
            'http_basic_ldap' => array(
                'service' => 'ldap',
                'dn_string' => 'uid={username},dc=example,dc=com',
                // ...
            ),
            'stateless' => true,
        ),
    ),
);
    

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.

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