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Auditing Security Events

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Auditing Security Events

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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.

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

X-Pack security provides two ways to persist audit logs:

The logfile output, which persists events to a dedicated <clustername>_access.log file on the host’s file system.
The 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:

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.

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.

Audit Event Types

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Each request may generate multiple audit events. The following is a list of the events that can be generated:

`anonymous_access_denied`			Logged when a request is denied due to a missing authentication token.
`authentication_success`			Logged when a user successfully authenticates.
`authentication_failed`			Logged when the authentication token cannot be matched to a known user.
`realm_authentication_failed`			Logged for every realm that fails to present a valid authentication token. `<realm>` represents the realm type.
`access_denied`			Logged when an authenticated user attempts to execute an action they do not have the necessary privilege to perform.
`access_granted`			Logged when an authenticated user attempts to execute an action they have the necessary privilege to perform. When the `system_access_granted` event is included, all system (internal) actions are also logged. The default setting does not log system actions to avoid cluttering the logs.
`run_as_granted`			Logged when an authenticated user attempts to run as another user that they have the necessary privileges to do.
`run_as_denied`			Logged when an authenticated user attempts to run as another user action they do not have the necessary privilege to do so.
`tampered_request`			Logged when X-Pack security detects that the request has been tampered with. Typically relates to `search/scroll` requests when the scroll ID is believed to have been tampered with.
`connection_granted`			Logged when an incoming TCP connection passes the IP Filter for a specific profile.
`connection_denied`			Logged when an incoming TCP connection does not pass the IP Filter for a specific profile.

Audit Event Attributes

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The following table shows the common attributes that can be associated with every event.

Table 12. Common Attributes

Attribute	Description
`timestamp`	When the event occurred.
`node_name`	The name of the node.
`node_host_name`	The hostname of the node.
`node_host_address`	The IP address of the node.
`layer`	The layer from which this event originated: `rest`, `transport` or `ip_filter`
`event_type`	The type of event that occurred: `anonymous_access_denied`, `authentication_failed`, `access_denied`, `access_granted`, `connection_granted`, `connection_denied`, `tampered_request`, `run_as_granted`, `run_as_denied`.

The following tables show the attributes that can be associated with each type of event. The log level determines which attributes are included in a log entry.

Table 13. REST anonymous_access_denied Attributes

Attribute	Description
`origin_address`	The IP address from which the request originated.
`uri`	The REST endpoint URI.
`request_body`	The body of the request, if enabled.

Table 14. REST authentication_success Attributes

Attribute	Description
`user`	The authenticated user.
`realm`	The realm that authenticated the user.
`uri`	The REST endpoint URI.
`params`	The REST URI query parameters.
`request_body`	The body of the request, if enabled.

Table 15. REST authentication_failed Attributes

Attribute	Description
`origin_address`	The IP address from which the request originated.
`principal`	The principal (username) that failed authentication.
`uri`	The REST endpoint URI.
`request_body`	The body of the request, if enabled.

Table 16. REST realm_authentication_failed Attributes

Attribute	Description
`origin_address`	The IP address from which the request originated.
`principal`	The principal (username) that failed authentication.
`uri`	The REST endpoint URI.
`request_body`	The body of the request, if enabled.
`realm`	The realm that failed to authenticate the user. NOTE: A separate entry is logged for each consulted realm.

Table 17. Transport anonymous_access_denied Attributes

Attribute	Description
`origin_type`	Where the request originated: `rest` (request originated from a REST API request), `transport` (request was received on the transport channel), `local_node` (the local node issued the request).
`origin_address`	The IP address from which the request originated.
`action`	The name of the action that was executed.
`request`	The type of request that was executed.
`indices`	A comma-separated list of indices this request pertains to (when applicable).

Table 18. Transport authentication_success Attributes

Attribute	Description
`origin_type`	Where the request originated: `rest` (request originated from a REST API request), `transport` (request was received on the transport channel), `local_node` (the local node issued the request).
`origin_address`	The IP address from which the request originated.
`user`	The authenticated user.
`realm`	The realm that authenticated the user.
`action`	The name of the action that was executed.
`request`	The type of request that was executed.

Table 19. Transport authentication_failed Attributes

Attribute	Description
`origin_type`	Where the request originated: `rest` (request originated from a REST API request), `transport` (request was received on the transport channel), `local_node` (the local node issued the request).
`origin_address`	The IP address from which the request originated.
`principal`	The principal (username) that failed authentication.
`action`	The name of the action that was executed.
`request`	The type of request that was executed.
`indices`	A comma-separated list of indices this request pertains to (when applicable).

Table 20. Transport realm_authentication_failed Attributes

Attribute	Description
`origin_type`	Where the request originated: `rest` (request originated from a REST API request), `transport` (request was received on the transport channel), `local_node` (the local node issued the request).
`origin_address`	The IP address from which the request originated.
`principal`	The principal (username) that failed authentication.
`action`	The name of the action that was executed.
`request`	The type of request that was executed.
`indices`	A comma-separated list of indices this request pertains to (when applicable).
`realm`	The realm that failed to authenticate the user. NOTE: A separate entry is logged for each consulted realm.

Table 21. Transport access_granted Attributes

Attribute	Description
`origin_type`	Where the request originated: `rest` (request originated from a REST API request), `transport` (request was received on the transport channel), `local_node` (the local node issued the request).
`origin_address`	The IP address from which the request originated.
`principal`	The principal (username) that passed authentication.
`action`	The name of the action that was executed.
`request`	The type of request that was executed.
`indices`	A comma-separated list of indices this request pertains to (when applicable).

Table 22. Transport access_denied Attributes

Attribute	Description
`origin_type`	Where the request originated: `rest` (request originated from a REST API request), `transport` (request was received on the transport channel), `local_node` (the local node issued the request).
`origin_address`	The IP address from which the request originated.
`principal`	The principal (username) that failed authentication.
`action`	The name of the action that was executed.
`request`	The type of request that was executed.
`indices`	A comma-separated list of indices this request relates to (when applicable).

Table 23. Transport tampered_request Attributes

Attribute	Description
`origin_type`	Where the request originated: `rest` (request originated from a REST API request), `transport` (request was received on the transport channel), `local_node` (the local node issued the request).
`origin_address`	The IP address from which the request originated.
`principal`	The principal (username) that failed to authenticate.
`action`	The name of the action that was executed.
`request`	The type of request that was executed.
`indices`	A comma-separated list of indices this request pertains to (when applicable).

Table 24. IP Filter connection_granted Attributes

Attribute	Description
`origin_address`	The IP address from which the request originated.
`transport_profile`	The transport profile the request targeted.
`rule`	The IP filtering rule that granted the request.

Table 25. IP Filter connection_denied Attributes

Attribute	Description
`origin_address`	The IP address from which the request originated.
`transport_profile`	The transport profile the request targeted.
`rule`	The IP filtering rule that denied the request.

Logfile Audit Output

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

Log Entry Format

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The format of a log entry is:

[<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 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 Entry Attributes for the attributes that can be included for each type of event.

Logfile Output Settings

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The events and some other information about what gets logged can be controlled using settings in the elasticsearch.yml file.

Table 26. Audited Event Settings

Name	Default	Description
`xpack.security.audit.logfile.events.include`	`access_denied`, `access_granted`, `anonymous_access_denied`, `authentication_failed`, `connection_denied`, `tampered_request`, `run_as_denied`, `run_as_granted`	Includes the specified events in the output.
`xpack.security.audit.logfile.events.exclude`		Excludes the specified events from the output.
`xpack.security.audit.logfile.events.emit_request_body`	false	Include or exclude the request body from REST requests on certain event types such as `authentication_failed`.

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

Table 27. Local Node Info Settings

Name	Default	Description
`xpack.security.audit.logfile.prefix.emit_node_name`	true	Include or exclude the node’s name from the local node info.
`xpack.security.audit.logfile.prefix.emit_node_host_address`	false	Include or exclude the node’s IP address from the local node info.
`xpack.security.audit.logfile.prefix.emit_node_host_name`	false	Include or exclude the node’s host name from the local node info.

You configure also configure how the logfile is written in the log4j2.properties file located in CONFIG_DIR/x-pack. 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.

Index Audit Output

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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:

xpack.security.audit.outputs: [ index, logfile ]

Table 28. Audit Log Indexing Configuration

Attribute	Default Setting	Description
`xpack.security.audit.index.bulk_size`	`1000`	Controls how many audit events are batched into a single write.
`xpack.security.audit.index.flush_interval`	`1s`	Controls how often buffered events are flushed to the index.
`xpack.security.audit.index.rollover`	`daily`	Controls how often to roll over to a new index: `hourly`, `daily`, `weekly`, or `monthly`.
`xpack.security.audit.index.events.include`	`anonymous_access_denied`, `authentication_failed`, `realm_authentication_failed`, `access_granted`, `access_denied`, `tampered_request`, `connection_granted`, `connection_denied`, `run_as_granted`, `run_as_denied`	The audit events to be indexed. See Audit Entry Types for the complete list.
`xpack.security.audit.index.events.exclude`		The audit events to exclude from indexing.
`xpack.security.audit.index.events.emit_request_body`	false	Include or exclude the request body from REST requests on certain event types such as `authentication_failed`.

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

Audit Index Settings

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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:

xpack.security.audit.index.settings:
  index:
    number_of_shards: 1
    number_of_replicas: 1

Forwarding Audit Logs to a Remote Cluster

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

Table 29. Remote Audit Log Indexing Configuration

Attribute	Description
`xpack.security.audit.index.client.hosts`	Comma-separated list of `host:port` pairs. These hosts should be nodes in the remote cluster.
`xpack.security.audit.index.client.cluster.name`	The name of the remote cluster.
`xpack.security.audit.index.client.xpack.security.user`	The `username:password` pair to use to authenticate with the remote cluster.

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:

xpack.security.audit.index.client.transport.sniff: true

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