Auditing security events | Elastic Stack Overview [6.3]

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Auditing security eventsedit

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 typesedit

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 attributesedit

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

Table 3. 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 4. 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 5. 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 6. 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 7. 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 8. 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 9. 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 10. 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 11. 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 12. 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.
`roles`	The set of roles granting permissions.
`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 13. 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.
`roles`	The set of roles granting permissions.
`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 14. 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 15. 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 16. 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 outputedit

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 formatedit

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 settingsedit

The events and some other information about what gets logged can be controlled using settings in the elasticsearch.yml file. See Audited Event Settings and Local Node Info Settings.

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

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.

Logfile audit events ignore policiesedit

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, 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 include/exclude method. Imagine the corpus of audit events and the policies chopping off unwanted events.

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 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*:

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 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:

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.

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

Index audit outputedit

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 ]

For more configuration options, see Audit log indexing configuration settings.

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 settingsedit

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 clusteredit

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 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:

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