Audit Log Concepts

Audit logs provide a way to capture, protect, and preserve authorization activity into topics in Kafka clusters on Confluent Platform using Confluent Server Authorizer. Specifically, audit logs record the runtime decisions of the permission checks that occur as users attempt to take actions that are protected by ACLs and RBAC. Auditable events are recorded in chronological order, although it is possible for a consumer of audit log messages to fetch them out of order.

Each auditable event includes information about who tried to do what, when they tried, and whether or not the system gave permission to proceed.

By default, audit logs are enabled and are managed by the inter-broker principal (typically, the user kafka), who has expansive permissions.

The primary value of audit logs is that they provide data you can use to assess security risks in your local and remote Kafka clusters. They contain all of the information necessary to follow a user’s interaction with your local or remote Kafka clusters, and provide a way to:

  • Track user and application access across the platform
  • Identify abnormal behavior and anomalies
  • Proactively monitor and resolve security risks

You can use Splunk, S3, and other sink connectors to move your audit log data to a target platform for analysis.

Before configuring and using audit logs, you must configure the Confluent Server Authorizer:

authorizer.class.name=io.confluent.kafka.security.authorizer.ConfluentServerAuthorizer

Auditable events

Note

These are event authorizations, so at the time of logging the event is about to occur. Also, users may attempt to authorize a task solely to see if they can perform the task, but not follow through with it. In these instances, the authorization is still captured in the audit log.

Each type of audit log event belongs to exactly one event category, and you can configure audit log routing rules to match specific event categories. MANAGEMENT and AUTHORIZE events are captured by default.

You can configure audit logs to capture the following events:

Event name Description Category Captured by Default
mds.Authorize An RBAC authorization is being requested using MDS. AUTHORIZE Yes
kafka.AlterConfigs A Kafka configuration is being altered/updated MANAGEMENT Yes
kafka.AlterPartitionReassignments Reassignments for a topic partition are being altered. MANAGEMENT Yes
kafka.AlterReplicaLogDirs Log directory of a replica of a partition is being altered. MANAGEMENT Yes
kafka.CreateAcls A Kafka broker ACL is being created. MANAGEMENT Yes
kafka.CreateDelegationToken A delegation token is being created. MANAGEMENT Yes
kafka.CreatePartitions Partitions are being added to a topic. MANAGEMENT Yes
kafka.CreateTopics A topic is being created. MANAGEMENT Yes
kafka.DeleteAcls A Kafka broker ACL is being deleted MANAGEMENT Yes
kafka.DeleteGroups A consumer group is being deleted. MANAGEMENT Yes
kafka.DeleteRecords Records are being deleted from a topic. MANAGEMENT Yes
kafka.DeleteTopics Topics are being deleted. MANAGEMENT Yes
kafka.ElectLeaders A replica is being elected as the leader of a topic partition. MANAGEMENT Yes
kafka.ExpireDelegationToken The delegation token is being marked as expired. MANAGEMENT Yes
kafka.IncrementalAlterConfigs A dynamic configuration of a Kafka broker is being altered. MANAGEMENT Yes
kafka.OffsetDelete Committed offset for a partition in a consumer group is being deleted. MANAGEMENT Yes
kafka.RenewDelegationToken A delegation token is being renewed. MANAGEMENT Yes
kafka.AddPartitionToTxn A partition is being added to a transaction. PRODUCE No
kafka.EndTxn A transaction is being completed. PRODUCE No
kafka.InitProducerId A transaction or idempotent write is being initialized by a Kafka producer. PRODUCE No
kafka.Produce A Kafka producer is writing a batch of records to a topic. PRODUCE No
kafka.AddOffsetsToTxn A producer is sending offsets to the consumer group coordinator and marking those offsets as part of the current transaction. CONSUME No
kafka.FetchConsumer A Kafka consumer is reading a batch of records from a topic. CONSUME No
kafka.JoinGroup A Kafka consumer is joining a consumer group. CONSUME No
kafka.LeaveGroup A Kafka consumer is leaving a group. CONSUME No
kafka.ListOffsets The offsets of a topic partition are being requested. CONSUME No
kafka.OffsetCommit A consumer is committing offsets of a partition that have been processed. CONSUME No
kafka.OffsetFetch Committed offsets of a consumer group are being requested. CONSUME No
kafka.SyncGroup A Kafka consumer is participating in a group rebalance. CONSUME No
kafka.TxnOffsetCommit Consumer offsets are being committed for a consumer group within a transaction. CONSUME No
kafka.ControlledShutdown A broker is being shut down. INTERBROKER No
kafka.FetchFollower A broker with a follower replica of a partition is fetching records for replication. INTERBROKER No
kafka.LeaderAndIsr Controller is sending leader and ISR (in-sync replica) state to a broker. INTERBROKER No
kafka.StopReplica Replication is being stopped for the replica of a topic partition. INTERBROKER No
kafka.UpdateMetadata Controller is sending new metadata to a broker. INTERBROKER No
kafka.WriteTxnMarkers A broker is writing transaction markers to update transaction state. INTERBROKER No
kafka.DescribeAcls Information about Kafka broker ACLs is being requested. DESCRIBE No
kafka.DescribeConfigs Information about broker configuration is being requested. DESCRIBE No
kafka.DescribeDelegationToken Information about a delegation token is being requested. DESCRIBE No
kafka.DescribeGroups Information about consumer groups is being requested. DESCRIBE No
kafka.DescribeLogDirs Information about replica log directories is being requested. DESCRIBE No
kafka.FindCoordinator A Kafka consumer is requesting information about its group coordinator. DESCRIBE No
kafka.ListGroups Information about consumer groups is being requested. DESCRIBE No
kafka.ListPartitionReassignments Current partition reassignments are being requested. DESCRIBE No
kafka.Metadata Topic metadata is being requested. DESCRIBE No
kafka.OffsetForLeaderEpoch Last offsets corresponding to a leader epoch are being requested. DESCRIBE No
kafka.Heartbeat A consumer is letting the group know that it is still active. HEARTBEAT No

Audit log content

The following example shows the contents of an audit log message that is returned from a cluster when a user creates a new topic:

{
    "id": "889bdcd9-a378-4bfe-8860-180ef8efd208",
    "source": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q",
    "specversion": "1.0",
    "type": "io.confluent.kafka.server/authorization",
    "time": "2019-10-24T16:15:48.355Z",
    "datacontenttype": "application/json",
    "subject": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q/topic=app3-topic",
    "confluentRouting": {
        "route": "confluent-audit-log-events"
    },
    "data": {
      "serviceName": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q",
      "methodName": "kafka.CreateTopics",
      "resourceName": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q/topic=app3-topic",
      "authenticationInfo": {
          "principal": "User:admin"
      },
      "authorizationInfo": {
          "granted": true,
          "operation": "Create",
          "resourceType": "Topic",
          "resourceName": "app3-topic",
          "patternType": "LITERAL",
          "superUserAuthorization": true
      },
      "request": {
          "correlation_id": "3",
          "client_id": "adminclient-6"
      },
      "requestMetadata": {
          "client_address": "/127.0.0.1"
      }
    }
}

The first section of the audit log displays information about the log message itself. Think of it as the envelope in which the message is delivered; it contains the following audit log implementation details:

Audit log entry Description
id A randomly-generated UUID that ensures uniqueness across all sources.
source Identifies the Kafka cluster that made the decision about whether or not the authorization was allowed. Always includes the CRN, and is always the same as the serviceName.
specversion The version of CloudEvents in use (CloudEvents is a vendor-neutral specification that defines the format of event data).
type The type of event that occurred (authorization request).
time The time at which the event occurred.
datacontenttype Identifies the CloudEvent format that the audit data is presented in (JSON).
subject Identifies the resource on which access has been allowed or denied.
confluentRouting Identifies the topic to which the event is sent. Topic routing is configurable. Refer to Configuring audit logs for details.

The next section of the audit log displays data (data) you can use to assess security risks in your local and remote Kafka clusters.

Audit log entry Description
serviceName Identifies the Kafka cluster that made the decision about whether or not the authorization was allowed. Always includes the CRN, and is always the same as source.
methodName The type of request that was made. For example, the methodName above shows that the user attempted to create a Kafka topic. This entry will include one of the event names listed above, and display either mds (if it’s an AUTHORIZE event) or kafka (if any other event) before it. For example: mds.Authorize, kafka.Metadata, kafka.CreateTopics.
resourceName The resource identifier (CRN) of the target of the request. For example, the resourceName above indicates the user attempted to create a topic in a uniquely-identified Kafka cluster.
authenticationInfo Identifies the user, service principal account, or principal attempting the request.
authorizationInfo Includes details about the decision that was made to authorize the request. The example above shows that the authorization request to create a topic in a Kafka cluster was granted. If RBAC is used, the resource and role (if any) are included. If ACLs are used, the ACL information is also included.
requestMetadata Identifies how the authorization request was sent and shows the requestor’s IP address, if known.

Audit log content examples

The following example shows what an audit log message looks like when RBAC is enabled:

{
    "id": "889bdcd9-a378-4bfe-8860-180ef8efd208",
    "source": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q",
    "specversion": "1.0",
    "type": "io.confluent.kafka.server/authorization",
    "time": "2019-10-24T16:15:48.355Z",
    "datacontenttype": "application/json",
    "subject": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q/topic=app3-topic",
    "confluentRouting": {
        "route": "confluent-audit-log-events"
    },
    "data": {
        "serviceName": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q",
        "methodName": "kafka.CreateTopics",
        "resourceName": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q/topic=app3-topic",
        "authenticationInfo": {
            "principal": "User:resourceOwner1"
        },
        "authorizationInfo": {
            "granted": true,
            "operation": "Create",
            "resourceType": "Topic",
            "resourceName": "app3-topic",
            "patternType": "LITERAL",
            "rbacAuthorization": {
                "role": "ResourceOwner",
                "scope": {
                    "outerScope": [],
                    "clusters": {
                        "kafka-cluster": "j94C72q3Qpym0MJ9McEufQ"
                    }
                }
            }
        }
    }
}

The following example shows what an audit log message looks like when you are using an ACL:

{
    "id": "889bdcd9-a378-4bfe-8860-180ef8efd208",
    "source": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q",
    "specversion": "1.0",
    "type": "io.confluent.kafka.server/authorization",
    "time": "2019-10-24T16:15:48.355Z",
    "datacontenttype": "application/json",
    "subject": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q/topic=app3-topic",
    "confluentRouting": {
        "route": "confluent-audit-log-events"
    },
    "data": {
        "serviceName": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q",
        "methodName": "kafka.CreateTopics",
        "resourceName": "crn:///kafka=8caBa-0_Tu-2k3rKSxY64Q/topic=app3-topic",
        "authenticationInfo": {
            "principal": "User:alice"
        },
        "authorizationInfo": {
            "granted": true,
            "operation": "DescribeConfigs",
            "resourceType": "Topic",
            "resourceName": "app3-topic",
            "patternType": "LITERAL",
            "aclAuthorization" : {
              "permissionType":"ALLOW",
              "host":"*"
            }
        },
    }
}

Confluent Resource Name (CRN)

CRNs provide a uniform way to uniquely identify resources referenced throughout Confluent Platform, and are used in audit logs. Each CRN is a uniform resource identifier (URI) that uniquely identifies the associated Confluent resource cluster and is prefixed with crn://.

You can configure the authority (also known as host name) of a CRN at the cluster level. This setting is empty by default, even if using the Confluent Metadata Service (MDS). Unless you specify an authority name using the confluent.authorizer.authority.name= option in server.properties, it will remain empty. If you have a single cluster or context, this approach could be sufficient.

However, consider the scenario where you have multiple production clusters that all refer to a single MDS for RBAC, and you also have a test group of clusters with its own MDS. In your production environment you are using the same MDS for RBAC, so on every cluster here you specify the authority as confluent.authorizer.authority.name=prod.mds.mycompany.com. In your test environment you specify the authority as confluent.authorizer.authority.name=test.mds.mycompany.com. The production cluster includes a topic named “travel” and your test cluster also has a topic named “travel” (the data in each is different). Because you configured an authority for each cluster, you can quickly and easily identify which cluster each “travel” topic resides in. Any time identical names are used in both your production and test clusters, the distinct authority provides a way to distinguish between the two.

We recommend setting the authority as the DNS name associated with your installation, which is an easy way to make CRNs more meaningful. So all of the brokers in any logical group (for example, your company’s staging environment) should specify the same authority.name (for example, confluent.authorizer.authority.name=mds.mycompany.com) in server.properties. For a logical group, such as clusters managed by a single MDS, you should specify the hostname used to reach the MDS. Do not specify different authority.name values for individual clusters unless you are deliberately keeping them separate (for example, a separate production cluster, separate staging cluster, or separate test cluster).

CRN formats vary by resource:

  • Kafka cluster: <authority>/kafka=<kafka-cluster-id>
  • Topic: <authority>/kafka=<kafka-cluster-id>/topic=<topic-name>
  • Consumer group: <authority>/kafka=<kafka-cluster-id>/group=<consumer-group-name>
  • ksqlDB cluster: <authority>/kafka=<kafka-cluster-id>/ksql=<ksql-cluster>
  • Connect: <authority>/kafka=<kafka-cluster-id>/connect=<connect-cluster>/connector=<connector-name>

Here are examples of CRNs used to associate audit logs with specific Confluent resources:

  • Kafka cluster: crn://mds.mycompany.com/kafka=rKtuRNiDQb2k9NMml6rLfA
  • Topic: crn://mds.mycompany.com/kafka=rKtuRNiDQb2k9NMml6rLfA/topic=app1-topic
  • Consumer group: crn://mds.mycompany.com/kafka=rKtuRNiDQb2k9NMml6rLfA/group=app1-consumer-group
  • KQSL cluster: crn://mds.mycompany.com/kafka=rKtuRNiDQb2k9NMml6rLfA/ksql=default_
  • Connect: crn://mds.mycompany.com/kafka=rKtuRNiDQb2k9NMml6rLfA/connect=ydfk/connector=sink-connector

Default audit log configuration

Audit logs are enabled by default, and are managed by the inter-broker principal (typically, the user kafka), who has expansive permissions.

If you do not configure anything, then audit logs are sent to a single topic in the local cluster that captures “allowed” and “denied” authorization events. This topic is named confluent-audit-log-events. Default audit logs capture MANAGEMENT and AUTHORIZE categories of authorization events only.

The following example shows the default audit log configuration:

{
    "destinations": {
        "topics": {
            "confluent-audit-log-events": {
                "retention_ms": 7776000000
            }
        }
    },
    "default_topics": {
        "allowed": "confluent-audit-log-events",
        "denied": "confluent-audit-log-events"
    }
}

For details about how to disable audit logging refer to Disabling audit logs.

Audit log configuration considerations

Most organizations have strict and specific security governance requirements and policies. In such cases, you can configure audit logs on a more granular level. Specifically, you can configure:

  • Which event categories you want to capture (including categories like produce, consume, and inter-broker, which are disabled by default)
  • Multiple topics to capture logs of differing importance
  • Which cluster to deliver audit logs to
  • Topic destination routes optimized for security and performance
  • Retention periods that serve the needs of your organization
  • Excluded principals, which ensures performance is not compromised by excessively high message volumes
  • The Kafka port over which to communicate with your audit log cluster

When enabling audit logging for produce and consume, be very selective about which events you want logged, and configure logging for only the most sensitive topics.

Also consider the following configuration recommendations for securing your audit logs:

  • For improved security, send audit logs to a different cluster. Limit permissions on the audit log cluster to ensure the audit log is trustworthy.
  • Create an audit log principal with limited permissions (for example, a user identified as confluent-audit). The default is to use the broker principal, which has expansive permissions.

Audit log destination cluster

Consider delivering audit log messages to a specific cluster set aside for the sole purpose of retaining them. This ensures that no one can access or tamper with your organization’s audit logs, and enables you to selectively conduct more in-depth auditing of sensitive data, while keeping log volumes down for less sensitive data.

If you deliver audit logs to another cluster, you must configure the connection to that cluster.

Audit log destination topics

Carefully consider the your topic settings when planning your audit logging configuration. You can flexibly route audit log messages to different topics based on subject, category, and whether authorizations were allowed or denied. You can also specify routes for specific subjects, or use prefixes (for example, _secure-* for sensitive authorization events) and wildcards to cover larger groups of resources.

Audit log replication factor and retention

You can specify the replication factor and retention period for your audit logs. The retention period specified in the audit log configuration is only enforced if the audit log feature automatically creates a topic that doesn’t already exist.

If you create a topic manually with a retention period value that conflicts with the retention specified in the router configuration, then the manually-created setting is used. The default retention period for audit log messages is 90 days (7776000000 ms).

Excluded principals

You can control the volume of audit log messages with excluded principals. If produce and consume audit logging is turned on, reads and writes conducted by principals generate additional audit logs, which means each log read and every log write results in yet another audit log message being created. This can quickly grow out of control and adversely impact cluster performance.

To keep audit logs from accumulating into an unmanageable volume you should always include the following excluded principals in your configuration:

  • A trusted principal responsible for writing to audit log topics. Make audit log writes the only task this principal performs. Do not grant additional permissions to this principal, and do not allow other principals to write to audit log topics.
  • A trusted principal responsible for reading from audit log topics. Make audit log reads the only task this principal performs. Do not grant additional permissions to this principal, and do not allow other principals to read from audit log topics.

Another approach to avoid unwanted audit log accumulation and the need to configure excluded principals altogether, is to direct audit logs to a secured cluster with limited access, and don’t enable audit logs on this cluster.