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[role="xpack"]
[[auditing]]
== Auditing security events

You can enable auditing to keep track of security-related events such as
authentication failures and refused connections. Logging these events enables you
to monitor your cluster for suspicious activity and provides evidence in the
event of an attack.

[IMPORTANT]
============================================================================
Audit logs are **disabled** by default. To enable this functionality, you
must set `xpack.security.audit.enabled` to `true` in `elasticsearch.yml`.
============================================================================

{Security} provides two ways to persist audit logs:

* The <<audit-log-output, `logfile`>> output, which persists events to
a dedicated `<clustername>_access.log` file on the host's file system.
* The <<audit-index, `index`>> output, which persists events to an Elasticsearch index.
The audit index can reside on the same cluster, or a separate cluster.

By default, only the `logfile` output is used when enabling auditing.
To facilitate browsing and analyzing the events, you can also enable
indexing by setting `xpack.security.audit.outputs` in `elasticsearch.yml`:

[source,yaml]
----------------------------
xpack.security.audit.outputs: [ index, logfile ]
----------------------------

The `index` output type should be used in conjunction with the `logfile`
output type Because it is possible for the `index` output type to lose
messages if the target index is unavailable, the `access.log` should be
used as the official record of events.

NOTE: Audit events are batched for indexing so there is a lag before
events appear in the index. You can control how frequently batches of
events are pushed to the index by setting
`xpack.security.audit.index.flush_interval` in `elasticsearch.yml`.

[float]
[[audit-event-types]]
=== Audit event types
Expand Down Expand Up @@ -281,195 +241,3 @@ The log level determines which attributes are included in a log entry.
| `rule` | The <<ip-filtering, IP filtering>> rule that denied
the request.
|======

[float]
[[audit-log-output]]
=== Logfile audit output

The `logfile` audit output is the default output for auditing. It writes data to
the `<clustername>_access.log` file in the logs directory.

[float]
[[audit-log-entry-format]]
=== Log entry format

The format of a log entry is:

[source,txt]
----------------------------------------------------------------------------
[<timestamp>] [<local_node_info>] [<layer>] [<entry_type>] <attribute_list>
----------------------------------------------------------------------------

`<timestamp>` :: When the event occurred. You can configure the
timestamp format in `log4j2.properties`.
`<local_node_info>` :: Information about the local node that generated
the log entry. You can control what node information
is included by configuring the
{ref}/auditing-settings.html#node-audit-settings[local node info settings].
`<layer>` :: The layer from which this event originated:
`rest`, `transport` or `ip_filter`.
`<entry_type>` :: The type of event that occurred: `anonymous_access_denied`,
`authentication_failed`, `access_denied`, `access_granted`,
`connection_granted`, `connection_denied`.
`<attribute_list>` :: A comma-separated list of key-value pairs that contain
data pertaining to the event. Formatted as
`attr1=[val1], attr2=[val2]`. See <<audit-event-attributes,
Audit Entry Attributes>> for the attributes that can be included
for each type of event.

[float]
[[audit-log-settings]]
=== Logfile output settings

The events and some other information about what gets logged can be
controlled using settings in the `elasticsearch.yml` file. See
{ref}/auditing-settings.html#event-audit-settings[Audited Event Settings] and
{ref}/auditing-settings.html#node-audit-settings[Local Node Info Settings].

IMPORTANT: No filtering is performed when auditing, so sensitive data may be
audited in plain text when including the request body in audit events.

[[logging-file]]
You can also configure how the logfile is written in the `log4j2.properties`
file located in `CONFIG_DIR`. By default, audit information is appended to the
`<clustername>_access.log` file located in the standard Elasticsearch `logs` directory
(typically located at `$ES_HOME/logs`). The file rolls over on a daily basis.

[float]
[[audit-log-ignore-policy]]
=== Logfile audit events ignore policies

The comprehensive audit trail is necessary to ensure accountability. It offers tremendous
value during incident response and can even be required for demonstrating compliance.

The drawback of an audited system is represented by the inevitable performance penalty incurred.
In all truth, the audit trail spends _I/O ops_ that are not available anymore for the user's queries.
Sometimes the verbosity of the audit trail may become a problem that the event type restrictions,
<<audit-log-settings, defined by `include` and `exclude`>>, will not alleviate.

*Audit events ignore policies* are a finer way to tune the verbosity of the audit trail.
These policies define rules that match audit events which will be _ignored_ (read as: not printed).
Rules match on the values of attributes of audit events and complement the <<audit-log-settings, include/exclude>> method.
Imagine the corpus of audit events and the policies chopping off unwanted events.

IMPORTANT: When utilizing audit events ignore policies you are acknowledging potential
accountability gaps that could render illegitimate actions undetectable.
Please take time to review these policies whenever your system architecture changes.

A policy is a named set of filter rules. Each filter rule applies to a single event attribute,
one of the `users`, `realms`, `roles` or `indices` attributes. The filter rule defines
a list of {ref}/query-dsl-regexp-query.html#regexp-syntax[Lucene regexp], *any* of which has to match the value of the audit
event attribute for the rule to match.
A policy matches an event if *all* the rules comprising it match the event.
An audit event is ignored, therefore not printed, if it matches *any* policy. All other
non-matching events are printed as usual.

All policies are defined under the `xpack.security.audit.logfile.events.ignore_filters`
settings namespace. For example, the following policy named _example1_ matches
events from the _kibana_ or _admin_user_ principals **and** operating over indices of the
wildcard form _app-logs*_:

[source,yaml]
----------------------------
xpack.security.audit.logfile.events.ignore_filters:
example1:
users: ["kibana", "admin_user"]
indices: ["app-logs*"]
----------------------------

An audit event generated by the _kibana_ user and operating over multiple indices
, some of which do not match the indices wildcard, will not match.
As expected, operations generated by all other users (even operating only on indices that
match the _indices_ filter) will not match this policy either.

Audit events of different types may have <<audit-event-attributes, different attributes>>.
If an event does not contain an attribute for which some policy defines filters, the
event will not match the policy.
For example, the following policy named _example2_, will never match `authentication_success` or
`authentication_failed` events, irrespective of the user's roles, because these
event schemas do not contain the `role` attribute:

[source,yaml]
----------------------------
xpack.security.audit.logfile.events.ignore_filters:
example2:
roles: ["admin", "ops_admin_*"]
----------------------------

Likewise, any events of users with multiple roles, some of which do not match the
regexps will not match this policy.

For completeness, although practical use cases should be sparse, a filter can match
a missing attribute of an event, using the empty string ("") or the empty list ([]).
For example, the following policy will match events that do not have the `indices`
attribute (`anonymous_access_denied`, `authentication_success` and other types) as well
as events over the _next_ index.

[source,yaml]
----------------------------
xpack.security.audit.logfile.events.ignore_filters:
example3:
indices: ["next", ""]
----------------------------


[float]
[[audit-index]]
=== Index audit output

In addition to logging to a file, you can store audit logs in Elasticsearch
rolling indices. These indices can be either on the same cluster, or on a
remote cluster. You configure the following settings in
`elasticsearch.yml` to control how audit entries are indexed. To enable
this output, you need to configure the setting `xpack.security.audit.outputs`
in the `elasticsearch.yml` file:

[source,yaml]
----------------------------
xpack.security.audit.outputs: [ index, logfile ]
----------------------------

For more configuration options, see
{ref}/auditing-settings.html#index-audit-settings[Audit log indexing configuration settings].

IMPORTANT: No filtering is performed when auditing, so sensitive data may be
audited in plain text when including the request body in audit events.

[float]
==== Audit index settings

You can also configure settings for the indices that the events are stored in.
These settings are configured in the `xpack.security.audit.index.settings` namespace
in `elasticsearch.yml`. For example, the following configuration sets the
number of shards and replicas to 1 for the audit indices:

[source,yaml]
----------------------------
xpack.security.audit.index.settings:
index:
number_of_shards: 1
number_of_replicas: 1
----------------------------

[float]
==== Forwarding audit logs to a remote cluster

To index audit events to a remote Elasticsearch cluster, you configure
the following `xpack.security.audit.index.client` settings:

* `xpack.security.audit.index.client.hosts`
* `xpack.security.audit.index.client.cluster.name`
* `xpack.security.audit.index.client.xpack.security.user`

For more information about these settings, see
{ref}/auditing-settings.html#remote-audit-settings[Remote Audit Log Indexing Configuration Settings].

You can pass additional settings to the remote client by specifying them in the
`xpack.security.audit.index.client` namespace. For example, to allow the remote
client to discover all of the nodes in the remote cluster you can specify the
`client.transport.sniff` setting:

[source,yaml]
----------------------------
xpack.security.audit.index.client.transport.sniff: true
----------------------------
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[role="xpack"]
[float]
[[forwarding-audit-logfiles]]
==== Forwarding audit logs to a remote cluster

To index audit events to a remote Elasticsearch cluster, you configure
the following `xpack.security.audit.index.client` settings:

* `xpack.security.audit.index.client.hosts`
* `xpack.security.audit.index.client.cluster.name`
* `xpack.security.audit.index.client.xpack.security.user`

For more information about these settings, see
{ref}/auditing-settings.html#remote-audit-settings[Remote Audit Log Indexing Configuration Settings].

You can pass additional settings to the remote client by specifying them in the
`xpack.security.audit.index.client` namespace. For example, to allow the remote
client to discover all of the nodes in the remote cluster you can specify the
`client.transport.sniff` setting:

[source,yaml]
----------------------------
xpack.security.audit.index.client.transport.sniff: true
----------------------------
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:edit_url: https://github.com/elastic/elasticsearch/edit/{branch}/x-pack/docs/en/security/auditing/overview.asciidoc
include::overview.asciidoc[]

:edit_url: https://github.com/elastic/elasticsearch/edit/{branch}/x-pack/docs/en/security/auditing/event-types.asciidoc
include::event-types.asciidoc[]

:edit_url: https://github.com/elastic/elasticsearch/edit/{branch}/x-pack/docs/en/security/auditing/output-logfile.asciidoc
include::output-logfile.asciidoc[]

:edit_url: https://github.com/elastic/elasticsearch/edit/{branch}/x-pack/docs/en/security/auditing/output-index.asciidoc
include::output-index.asciidoc[]

:edit_url: https://github.com/elastic/elasticsearch/edit/{branch}/x-pack/docs/en/security/auditing/forwarding-logs.asciidoc
include::forwarding-logs.asciidoc[]
38 changes: 38 additions & 0 deletions x-pack/docs/en/security/auditing/output-index.asciidoc
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[role="xpack"]
[float]
[[audit-index]]
=== Index audit output

In addition to logging to a file, you can store audit logs in Elasticsearch
rolling indices. These indices can be either on the same cluster, or on a
remote cluster. You configure the following settings in
`elasticsearch.yml` to control how audit entries are indexed. To enable
this output, you need to configure the setting `xpack.security.audit.outputs`
in the `elasticsearch.yml` file:

[source,yaml]
----------------------------
xpack.security.audit.outputs: [ index, logfile ]
----------------------------

For more configuration options, see
{ref}/auditing-settings.html#index-audit-settings[Audit log indexing configuration settings].

IMPORTANT: No filtering is performed when auditing, so sensitive data may be
audited in plain text when including the request body in audit events.

[float]
==== Audit index settings

You can also configure settings for the indices that the events are stored in.
These settings are configured in the `xpack.security.audit.index.settings` namespace
in `elasticsearch.yml`. For example, the following configuration sets the
number of shards and replicas to 1 for the audit indices:

[source,yaml]
----------------------------
xpack.security.audit.index.settings:
index:
number_of_shards: 1
number_of_replicas: 1
----------------------------
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