OpenSearch/x-pack/docs/en/security/authentication/configuring-ldap-realm.asciidoc

To integrate with LDAP, you configure an `ldap` realm and map LDAP groups to
user roles.

. Determine which mode you want to use. The `ldap` realm supports two modes of 
operation, a user search mode and a mode with specific templates for user DNs. 
+
--
LDAP user search is the most common mode of operation. In this mode, a specific
user with permission to search the LDAP directory is used to search for the DN 
of the authenticating user based on the provided username and an LDAP attribute. 
Once found, the user is authenticated by attempting to bind to the LDAP server 
using the found DN and the provided password.

If your LDAP environment uses a few specific standard naming conditions for
users, you can use user DN templates to configure the realm. The advantage of
this method is that a search does not have to be performed to find the user DN.
However, multiple bind operations might be needed to find the correct user DN.
--

. To configure an `ldap` realm with user search:

.. Add a realm configuration of to `elasticsearch.yml` under the
`xpack.security.authc.realms.ldap` namespace. At a minimum, you must specify
the `url` of the LDAP server, and set `user_search.base_dn` to the container DN
where the users are searched for.
If you are configuring multiple realms, you should also explicitly set the
`order` attribute to control the order in which the realms are consulted during 
authentication. See <<ref-ldap-settings>> for all of the options you can set for 
an `ldap` realm.
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--
For example, the following snippet shows an LDAP realm configured with a user search:

[source, yaml]
------------------------------------------------------------
xpack:
  security:
    authc:
      realms:
        ldap:
          ldap1:
            order: 0
            url: "ldaps://ldap.example.com:636"
            bind_dn: "cn=ldapuser, ou=users, o=services, dc=example, dc=com"
            user_search:
              base_dn: "dc=example,dc=com"
              filter: "(cn={0})"
            group_search:
              base_dn: "dc=example,dc=com"
            files:
              role_mapping: "ES_PATH_CONF/role_mapping.yml"
            unmapped_groups_as_roles: false
------------------------------------------------------------

The password for the `bind_dn` user should be configured by adding the appropriate
`secure_bind_password` setting to the {es} keystore.
For example, the following command adds the password for the example realm above:

[source, shell]
------------------------------------------------------------
bin/elasticsearch-keystore add \
xpack.security.authc.realms.ldap.ldap1.secure_bind_password
------------------------------------------------------------

IMPORTANT: When you configure realms in `elasticsearch.yml`, only the
realms you specify are used for authentication. If you also want to use the
`native` or `file` realms, you must include them in the realm chain.

--

. To configure an `ldap` realm with user DN templates:

.. Add a realm configuration to `elasticsearch.yml` in the
`xpack.security.authc.realms.ldap` namespace. At a minimum, you must specify
the `url` of the LDAP server, and specify at least one template with the
`user_dn_templates` option. If you are configuring multiple realms, you should
also explicitly set the `order` attribute to control the order in which the
realms are consulted during authentication.
See <<ref-ldap-settings>> for all of the options you can set for an `ldap` realm.
+
--
For example, the following snippet shows an LDAP realm configured with user DN 
templates:

[source, yaml]
------------------------------------------------------------
xpack:
  security:
    authc:
      realms:
        ldap:
          ldap1:
            order: 0
            url: "ldaps://ldap.example.com:636"
            user_dn_templates:
              - "cn={0}, ou=users, o=marketing, dc=example, dc=com"
              - "cn={0}, ou=users, o=engineering, dc=example, dc=com"
            group_search:
              base_dn: "dc=example,dc=com"
            files:
              role_mapping: "/mnt/elasticsearch/group_to_role_mapping.yml"
            unmapped_groups_as_roles: false
------------------------------------------------------------

IMPORTANT: The `bind_dn` setting is not used in template mode.
All LDAP operations run as the authenticating user.

--

. (Optional) Configure how the {security-features} interact with multiple LDAP
servers. 
+ 
--
The `load_balance.type` setting can be used at the realm level. The {es}
{security-features} support both failover and load balancing modes of operation.
See <<ref-ldap-settings>>.
--

. (Optional) To protect passwords, 
<<tls-ldap,encrypt communications between {es} and the LDAP server>>. 

. Restart {es}. 

. Map LDAP groups to roles. 
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--
The `ldap` realm enables you to map LDAP users to roles via their LDAP
groups, or other metadata. This role mapping can be configured via the
<<security-api-put-role-mapping,add role mapping API>> or by using a file stored
on each node. When a user authenticates with LDAP, the privileges
for that user are the union of all privileges defined by the roles to which
the user is mapped.

Within a mapping definition, you specify groups using their distinguished
names. For example, the following mapping configuration maps the LDAP
`admins` group to both the `monitoring` and `user` roles, and maps the
`users` group to the `user` role.

Configured via the role-mapping API:

[source,console]
--------------------------------------------------
PUT /_security/role_mapping/admins
{
  "roles" : [ "monitoring" , "user" ],
  "rules" : { "field" : {
    "groups" : "cn=admins,dc=example,dc=com" <1>
  } },
  "enabled": true
}
--------------------------------------------------

<1> The LDAP distinguished name (DN) of the `admins` group.

[source,console]
--------------------------------------------------
PUT /_security/role_mapping/basic_users
{
  "roles" : [ "user" ],
  "rules" : { "field" : {
    "groups" : "cn=users,dc=example,dc=com" <1>
  } },
  "enabled": true
}
--------------------------------------------------

<1> The LDAP distinguished name (DN) of the `users` group.

Or, alternatively, configured via the role-mapping file:
[source, yaml]
------------------------------------------------------------
monitoring: <1>
  - "cn=admins,dc=example,dc=com" <2>
user:
  - "cn=users,dc=example,dc=com" <3>
  - "cn=admins,dc=example,dc=com"
------------------------------------------------------------
<1> The name of the mapped role.
<2> The LDAP distinguished name (DN) of the `admins` group.
<3> The LDAP distinguished name (DN) of the `users` group.

For more information, see 
<<mapping-roles-ldap>> and <<mapping-roles>>.

NOTE: The LDAP realm supports
<<authorization_realms,authorization realms>> as an
alternative to role mapping.

--

. (Optional) Configure the `metadata` setting on the LDAP realm to include extra 
fields in the user's metadata. 
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--
By default, `ldap_dn` and `ldap_groups` are populated in the user's metadata. 
For more information, see 
<<ldap-user-metadata>>. 

The example below includes the user's common name (`cn`) as an additional
field in their metadata.
[source,yaml]
--------------------------------------------------
xpack:
  security:
    authc:
      realms:
        ldap:
          ldap1:
            metadata: cn
--------------------------------------------------
--

. Set up SSL to encrypt communications between {es} and LDAP. See <<tls-ldap>>.