OpenSearch/docs/en/security/authentication.asciidoc

[[setting-up-authentication]]
== Setting Up User Authentication

Authentication identifies an individual. To gain access to restricted resources,
a user must prove their identity, via passwords, credentials, or some other
means (typically referred to as authentication tokens).

You can use the native support for managing and authenticating users, or
integrate with external user management systems such as LDAP and Active
Directory. For information about managing native users,
see <<managing-native-users, Managing Native Users>>.

[float]
[[built-in-users]]
=== Built-in Users

{security} provides built-in user credentials to help you get up and running.
These users have a fixed set of privileges and cannot be authenticated until their
passwords have been set. The exception is the `elastic` user which can be authenticated
from a localhost rest request with an empty password. Until a password is set, the elastic
user is only authorized to perform change password requests.
Please read <<reset-built-in-user-passwords,Reset Built-in User Passwords>> below.

.{security} Built-in Users
|========
| Name               | Description
| `elastic`          | A built-in _superuser_. See <<built-in-roles>>.
| `kibana`           | The user Kibana uses to connect and communicate with Elasticsearch.
| `logstash_system`  | The user Logstash uses when storing monitoring information in Elasticsearch.
|========

[float]
[[built-in-user-explanation]]
==== How the Built-in Users Work
These built-in users are stored within a special `.security` index managed by
{security}.
This means that, if the password is changed, or a user is disabled, then that
change is automatically reflected on each node in the cluster. It also means
that if your `.security` index is deleted, or restored from a snapshot, then
any changes you have applied will be lost.

Although they share the same API, the built-in users are separate and distinct
from users managed by the <<native-realm, native realm>>. Disabling the native
realm will not have any effect on the built-in users. The built-in users can
be disabled individually, using the
{ref}/security-api-users.html[user management API].

[float]
[[reset-built-in-user-passwords]]
==== Reset Built-in User Passwords
[IMPORTANT]
=============================================================================
You must set the passwords for all built-in users.
You can update passwords from the *Management > Users* UI in Kibana or with the
{ref}/security-api-users.html#security-api-reset-user-password[Reset Password API]:

[source,js]
---------------------------------------------------------------------
PUT _xpack/security/user/elastic/_password
{
  "password": "elasticpassword"
}
---------------------------------------------------------------------
// CONSOLE

[source,js]
---------------------------------------------------------------------
PUT _xpack/security/user/kibana/_password
{
  "password": "kibanapassword"
}
---------------------------------------------------------------------
// CONSOLE

[source,js]
---------------------------------------------------------------------
PUT _xpack/security/user/logstash_system/_password
{
  "password": "logstashpassword"
}
---------------------------------------------------------------------
// CONSOLE

Once the `kibana` user password is reset, you need to update the Kibana server
with the new password by setting `elasticsearch.password` in the
`kibana.yml` configuration file:

[source,yaml]
-----------------------------------------------
elasticsearch.password: kibanapassword
-----------------------------------------------

The `logstash_system` user is used internally within Logstash when
monitoring is enabled for Logstash.

To enable this feature in Logstash, you need to update the Logstash
configuration with the new password by setting `xpack.monitoring.elasticsearch.password` in
the `logstash.yml` configuration file:

[source,yaml]
----------------------------------------------------------
xpack.monitoring.elasticsearch.password: logstashpassword
----------------------------------------------------------

If you have upgraded from an older version of elasticsearch/x-pack,
the `logstash_system` user may have defaulted to _disabled_ for security reasons.
Once the password has been changed, you can enable the user via the following API call:

[source,js]
---------------------------------------------------------------------
PUT _xpack/security/user/logstash_system/_enable
---------------------------------------------------------------------
// CONSOLE
=============================================================================

[float]
[[internal-users]]
=== Internal Users

{security} has two _internal_ users (`_system` and `_xpack`) that are
responsible for the operations that take place inside an Elasticsearch cluster.

These users are only used by requests that originate from within the cluster.
For this reason, they cannot be used to authenticate against the API, and there
is no password to manage or reset.

From time-to-time you may find a reference to one of these users inside your
logs, including <<auditing, audit logs>>.

=== How Authentication Works

Authentication in {security} is handled by one or more authentication services
called _realms_. A _realm_ is used to resolve and authenticate users based on
authentication tokens. {security} provides the following built-in realms:

_native_::
An internal realm where users are stored in a dedicated Elasticsearch index.
This realm supports an authentication token in the form of username and password,
and is available by default when no realms are explicitly configured. See
<<native-realm>>.

_ldap_::
A realm that uses an external LDAP server to authenticate the
users. This realm supports an authentication token in the form of username and
password, and requires explicit configuration in order to be used. See
<<ldap-realm>>.

_active_directory_::
A realm that uses an external Active Directory Server to authenticate the
users. With this realm, users are authenticated by usernames and passwords.
See <<active-directory-realm>>.

_pki_::
A realm that authenticates users using Public Key Infrastructure (PKI). This
realm works in conjunction with SSL/TLS and identifies the users through the
Distinguished Name (DN) of the client's X.509 certificates. See <<pki-realm>>.

_file_::
An internal realm where users are defined in files stored on each node in the
Elasticsearch cluster. This realm supports an authentication token in the form
of username and password, and is always available. See <<file-realm>>.

{security} also supports custom realms. If you need to integrate with another
authentication system, you can build a custom realm plugin. For more information,
see <<custom-realms, Integrating with Other Authentication Systems>>.

Realms live within a _realm chain_. It is essentially a prioritized list of
configured realms (typically of various types). The order of the list determines
the order in which the realms will be consulted. During the authentication process,
{security} will consult and try to authenticate the request one realm at a time.
Once one of the realms successfully authenticates the request, the authentication
is considered to be successful and the authenticated user will be associated
with the request (which will then proceed to the authorization phase). If a realm
cannot authenticate the request, the next in line realm in the chain will be
consulted. If all realms in the chain could not authenticate the request, the
authentication is then considered to be unsuccessful and an authentication error
will be returned (as HTTP status code `401`).

NOTE: Some systems (e.g. Active Directory) have a temporary lock-out period after
      several successive failed login attempts. If the same username exists in
      multiple realms, unintentional account lockouts are possible. For more
      information, please see <<trouble-shoot-active-directory, here>>.

The default realm chain contains the `native` and `file` realms. To explicitly,
configure a realm chain, you specify the chain in `elasticsearch.yml`. When you
configure a realm chain, only the realms you specify are used for authentication.
To use the `native` and `file` realms, you must include them in the chain.

The following snippet configures a realm chain that includes the `file` and
`native` realms, as well as two LDAP realms and an Active Directory realm.

[source,yaml]
----------------------------------------
xpack.security.authc:
  realms:

    file:
      type: file
      order: 0

    native:
      type: native
      order: 1

    ldap1:
      type: ldap
      order: 2
      enabled: false
      url: 'url_to_ldap1'
      ...

    ldap2:
      type: ldap
      order: 3
      url: 'url_to_ldap2'
      ...

    ad1:
      type: active_directory
      order: 4
      url: 'url_to_ad'
----------------------------------------

As can be seen above, each realm has a unique name that identifies it and each
realm type dictates its own set of required and optional settings. That said,
there are three settings that are common to all realms:

[cols=",^,",options="header"]
|=========
| Setting     | Required  | Description

| `type`      | true      | Identifies the type of the realm. The realm type
                            determines what other settings the realms should be
                            configured with. The type can be one of: `native`,
                            `ldap`, `active_directory`, `pki`, `file`, or in case
                            of a custom realm, the type name that identifies it.

| `order`     | false     | A numeric value representing the priority/index of
                            the realm within the realm chain. This will determine
                            the order by which the realms will be consulted
                            during authentication, with lower order being consulted
                            first.

| `enabled`   | false     | When set to `false` the realm will be disabled and
                            will not be added to the realm chain. This is useful
                            for debugging purposes as it enables you to remove
                            a realm from the chain without deleting and losing
                            its configuration.
|=========

Realm types can roughly be classified in two categories:

Internal::  Realms that are internal to Elasticsearch and don't require any
            communication with external parties. They are fully managed by
            {security}. There can only be a maximum of one configured realm
            per internal realm type. {security} provides two internal realm
            types: `native` and `file`.

External::  Realms that require interaction with parties/components external to
            Elasticsearch, typically, with enterprise grade identity management
            systems. Unlike internal realms, there can be as many external realms
            as one would like - each with its own unique name and configuration.
            {security} provides three external realm types: `ldap`,
            `active_directory` and `pki`.

include::authentication/anonymous-access.asciidoc[]

include::authentication/native-realm.asciidoc[]

include::authentication/ldap-realm.asciidoc[]

include::authentication/active-directory-realm.asciidoc[]

include::authentication/pki-realm.asciidoc[]

include::authentication/file-realm.asciidoc[]

include::authentication/custom-realm.asciidoc[]

include::authentication/user-cache.asciidoc[]