[role="xpack"]
[[service-accounts]]
=== Service accounts

The {stack-security-features} provide _service accounts_ specifically for
integration with external services that connect to {es}, such as {fleet} server.
Service accounts have a fixed set of privileges and cannot authenticate
until you create a service account token for them. Additionally, service
accounts are predefined in code, and are always enabled.

A service account corresponds to a specific external service. You create service
account tokens for a service account. The service can then authenticate with the
token and perform relevant actions. For example, {fleet} server can use its
service token to authenticate with {es} and then manage its own API keys.

You can create multiple service tokens for the same service account, which
prevents credential sharing between multiple instances of the same
external service. Each instance can assume the same identity while using
their own distinct service token for authentication.

Service accounts provide flexibility over <<built-in-users,built-in users>>
because they:

* Do not rely on the <<native-realm,internal `native` realm>>, and aren't
always required to rely on the `.security` index
* Use a <<security-api-create-api-key-request-body,role descriptor>> named after the service account principal instead of
traditional roles
* Support multiple credentials through service account tokens

Service accounts are not included in the response of the
<<security-api-get-user,get users API>>. To retrieve a service account, use the
<<security-api-get-service-accounts,get service accounts API>>.

[discrete]
[[service-accounts-explanation]]
=== Service accounts usage
Service accounts have a
<<security-api-get-service-accounts-path-params,unique principal>> that takes
the format of `<namespace>/<service>`, where the `namespace` is a top-level
grouping of service accounts, and `service` is the name of the service and
must be unique within its namespace.

Service accounts are predefined in code. The following service accounts are
available:

`elastic/fleet-server`:: The service account used by the {fleet} server to
communicate with {es}.

`elastic/kibana`:: The service account used by {kib} to communicate with
{es}.

// tag::service-accounts-usage[]
IMPORTANT: Do not attempt to use service accounts for authenticating individual
users. Service accounts can only be authenticated with service tokens, which are
not applicable to regular users.
// end::service-accounts-usage[]

[discrete]
[[service-accounts-tokens]]
=== Service account tokens
A service account token, or service token, is a unique string that a
service uses to authenticate with {es}. For a given service account, each token
must have a unique name. Because tokens include access credentials, they should
always be kept secret by whichever client is using them.

Service tokens can be backed by either the `.security` index (recommended) or
the `service_tokens` file. You can create multiple service tokens for a single
service account, which enables multiple instances of the same service to run
with different credentials.

You must create a service token to use a service account. You can
create a service token using either:

* The <<security-api-create-service-token,create service account token API>>,
which saves the new service token in the `.security` index and returns
the bearer token in the HTTP response.
* The <<service-tokens-command,elasticsearch-service-tokens>> CLI tool, which
saves the new service token in the `$ES_HOME/config/service_tokens` file
and outputs the bearer token to your terminal

We recommend that you create service tokens via the REST API rather than the CLI.
The API stores service tokens within the `.security` index which means that the
tokens are available for authentication on all nodes, and will be backed up within
cluster snapshots.
The use of the CLI is intended for cases where there is an external orchestration
process (such as {ece-ref}[{ece}] or {eck-ref}[{eck}]) that will manage the
creation and distribution of the `service_tokens` file.

Both of these methods (API and CLI) create a service token with a guaranteed
secret string length of `22`.
The minimal, acceptable length of a secret string for a service token is `10`.
If the secret string doesn't meet this minimal length, authentication with {es}
will fail without even checking the value of the service token.

Service tokens never expire. You must actively
<<security-api-delete-service-token,delete>> them if they are no longer needed.

[discrete]
[[authenticate-with-service-account-token]]
=== Authenticate with service tokens

NOTE: Service accounts currently do not support basic authentication.

To use a service account token, include the generated token value in a request
with an `Authorization: Bearer` header:

[source,shell]
----
curl -H "Authorization: Bearer AAEAAWVsYXN0aWM...vZmxlZXQtc2VydmVyL3Rva2VuMTo3TFdaSDZ" http://localhost:9200/_security/_authenticate
----
// NOTCONSOLE

A successful authentication response includes a `token` field, which contains a
`name` field for the name of the service token and a `type` field for the
type of the service token:

[source,js]
----
{
  "username": "elastic/fleet-server",
  "roles": [],
  "full_name": "Service account - elastic/fleet-server",
  "email": null,
  "token": {
    "name": "token1",                 <1>
    "type": "_service_account_index"  <2>
  },
  "metadata": {
    "_elastic_service_account": true
  },
  "enabled": true,
  "authentication_realm": {
    "name": "_service_account",
    "type": "_service_account"
  },
  "lookup_realm": {
    "name": "_service_account",
    "type": "_service_account"
  },
  "authentication_type": "token"
}
----
// NOTCONSOLE
<1> Name of the service account token.
<2> Type of service account token. The value always begins with
`_service_account_` and is followed by a string that indicates the service
token backend in use (can be either `file` or `index`).
