DOC Audit security config change (elastic#67624)

Audit log doc changes about:
* the new security_config_change event type (main scope of this PR)
* remove mentions of the 6.5 audit format changes (the JSON format)
* mention the new archiving and rotation by size (in v8 only)
* mention the request.id event attribute used to correlate audit events
* mention that audit is only available on certain subscription levels
* add an exhaustive audit event example list (because schema became too complex to explain in words 😢 given the new security_config_change events)
* move the ignore policies are explained on a separate page (it was collocated with the logfile output since we had multiple outputs and the policies were specific the the logfile only).

Co-authored-by: Lisa Cawley [email protected]

Relates elastic#62916
Closes elastic#29912

docs/reference/settings/audit-settings.asciidoc

@@ -8,7 +8,15 @@
 [[auditing-settings-description]]
 You can use <<enable-audit-logging,audit logging>> to record security-related
 events, such as authentication failures, refused connections, and data-access
-events.
+events. In addition, changes via the APIs to the security configuration, such
+as creating, updating and removing <<native-realm, native>> and
+<<built-in-users, built-in>> users, <<security-api-put-role, roles>>,
+<<security-api-put-role-mapping, role mappings>> and
+<<security-api-create-api-key, API keys>> are also recorded.
+--
+TIP: Audit logs are only available on certain subscription levels.
+For more information, see {subscriptions}.
+--
 
 If configured, auditing settings must be set on every node in the cluster.
 Static settings, such as `xpack.security.audit.enabled`, must be configured in
@@ -40,29 +48,38 @@ by using the following settings:
 // tag::xpack-sa-lf-events-include-tag[]
 `xpack.security.audit.logfile.events.include`::
 (<<dynamic-cluster-setting,Dynamic>>)
-Specifies which events to include in the auditing output. The default value is:
+Specifies the <<audit-event-types, kind of events>> to print in the auditing output.
+In addition, `_all` can be used to exhaustively audit all the events, but this is usually
+discouraged since it will get very verbose.
+The default list value contains:
 `access_denied, access_granted, anonymous_access_denied, authentication_failed,
-connection_denied, tampered_request, run_as_denied, run_as_granted`.
+connection_denied, tampered_request, run_as_denied, run_as_granted,
+security_config_change`.
 // end::xpack-sa-lf-events-include-tag[]
 
 [[xpack-sa-lf-events-exclude]]
 // tag::xpack-sa-lf-events-exclude-tag[]
 `xpack.security.audit.logfile.events.exclude`::
 (<<dynamic-cluster-setting,Dynamic>>)
-Excludes the specified events from the output. By default, no events are
-excluded.
+Excludes the specified <<audit-event-types, kind of events>> from the include list.
+This is useful in the case where the `events.include` setting contains the special value `_all`.
+The default is the empty list.
 // end::xpack-sa-lf-events-exclude-tag[]
 
 [[xpack-sa-lf-events-emit-request]]
 // tag::xpack-sa-lf-events-emit-request-tag[]
 `xpack.security.audit.logfile.events.emit_request_body`::
 (<<dynamic-cluster-setting,Dynamic>>)
-Specifies whether to include the request body from REST requests on certain
-event types such as `authentication_failed`. The default value is `false`.
+Specifies whether to include the full request body from REST requests as an
+attribute of certain kinds of audit events. This setting can be used to
+<<auditing-search-queries, audit search queries>>.
++
+The default value is `false`, so request bodies are not printed.
 +
 --
-IMPORTANT: No filtering is performed when auditing, so sensitive data may be
-audited in plain text when including the request body in audit events.
+IMPORTANT: Be advised that sensitive data may be audited in plain text when including
+the request body in audit events, even though all the security APIs, such as those that
+change the user's password, have the credentials filtered out when audited.
 --
 
 // end::xpack-sa-lf-events-emit-request-tag[]
@@ -99,8 +116,6 @@ The default value is `false`.
 `xpack.security.audit.logfile.emit_node_id`::
 (<<dynamic-cluster-setting,Dynamic>>)
 Specifies whether to include the node id as a field in each audit event.
-This is available for the new format only. That is to say, this information
-does not exist in the `<clustername>_access.log` file.
 Unlike <<node-name,node name>>, whose value might change if the administrator
 changes the setting in the config file, the node id will persist across cluster
 restarts and the administrator cannot change it.
@@ -110,11 +125,13 @@ The default value is `true`.
 [[audit-event-ignore-policies]]
 ==== Audit Logfile Event Ignore Policies
 
-These settings affect the <<audit-log-ignore-policy,ignore policies>>
+The following settings affect the <<audit-log-ignore-policy,ignore policies>>
 that enable fine-grained control over which audit events are printed to the log file.
 All of the settings with the same policy name combine to form a single policy.
-If an event matches all of the conditions for a specific policy, it is ignored
-and not printed.
+If an event matches all the conditions of any policy, it is ignored and not printed.
+Most audit events are subject to the ignore policies. The sole exception are
+events of the `security_config_change` type, which cannot be filtered out, unless
+<<xpack-sa-lf-events-exclude, excluded>> altogether.
 
 [[xpack-sa-lf-events-ignore-users]]
 // tag::xpack-sa-lf-events-ignore-users-tag[]

x-pack/docs/en/security/auditing/auditing-search-queries.asciidoc

@@ -4,14 +4,15 @@
 === Auditing search queries
 
 There is no <<audit-event-types, audit event type>> specifically
-dedicated to search queries. Search queries are analyzed and then processed; the 
+dedicated to search queries. Search queries are analyzed and then processed; the
 processing triggers authorization actions that are audited.
 However, the original raw query, as submitted by the client, is not accessible
 downstream when authorization auditing occurs.
 
 Search queries are contained inside HTTP request bodies, however, and some
-audit events that are generated by the REST layer can be toggled to output
-the request body to the audit log.
+audit events that are generated by the REST layer, on the coordinating node,
+can be toggled to output the request body to the audit log. Therefore, one
+must audit request bodies in order to audit search queries.
 
 To make certain audit events include the request body, edit the following
 setting in the `elasticsearch.yml` file:
@@ -26,9 +27,15 @@ audited in plain text when audit events include the request body. Also, the
 request body can contain malicious content that can break a parser consuming
 the audit logs.
 
-There are only a handful of <<audit-event-types, audit event types>> that are 
-generated in the REST layer and can access the request body. Most of them are not
-included by default.
+The request body is printed as an escaped JSON string value (RFC 4627) to the `request.body`
+event attribute.
+
+Not all events contain the `request.body` attribute, even when the above setting
+is toggled. The ones that do are: `authentication_success`,
+`authentication_failed`, `realm_authentication_failed`, `tampered_request`, `run_as_denied`,
+and `anonymous_access_denied`. The `request.body` attribute is printed on the coordinating node only
+(the node that handles the REST request). Most of these event types are
+<<xpack-sa-lf-events-include, not included by default>>.
 
 A good practical piece of advice is to add `authentication_success` to the event
 types that are audited (add it to the list in the `xpack.security.audit.logfile.events.include`),

x-pack/docs/en/security/auditing/enable-audit-logging.asciidoc

@@ -3,21 +3,28 @@
 == Enabling audit logging
 
 You can log security-related events such as authentication failures and refused connections
-to monitor your cluster for suspicious activity. 
+to monitor your cluster for suspicious activity (including data access authorization and user
+security configuration changes).
+
 Audit logging also provides forensic evidence in the event of an attack.
 
 [IMPORTANT]
 ============================================================================
 Audit logs are **disabled** by default. You must explicitly enable audit logging.
 ============================================================================
+--
+TIP: Audit logs are only available on certain subscription levels.
+For more information, see {subscriptions}.
+--
 
 To enable enable audit logging:
 
 . Set `xpack.security.audit.enabled` to `true` in `elasticsearch.yml`.
 . Restart {es}.
 
 When audit logging is enabled, <<audit-event-types, security events>> are persisted to 
-a dedicated `<clustername>_audit.json` file on the host's file system (on each node).
+a dedicated `<clustername>_audit.json` file on the host's file system, on every cluster node.
+For more information, see <<audit-log-output>>.
 
 You can configure additional options to control what events are logged and 
 what information is included in the audit log.