Streams Security

Kafka Streams natively integrates with the Kafka’s security features and supports all of the client-side security features in Kafka. Streams leverages the Java Producer and Consumer API.

To secure your Stream processing applications, configure the security settings in the corresponding Kafka producer and consumer clients, and then specify the corresponding configuration settings in your Kafka Streams application.

Kafka supports cluster encryption and authentication, including a mix of authenticated and unauthenticated, and encrypted and non-encrypted clients. Using security is optional.

Here a few relevant client-side security features:

Encrypt data-in-transit between your applications and Kafka brokers
You can enable the encryption of the client-server communication between your applications and the Kafka brokers. For example, you can configure your applications to always use encryption when reading and writing data to and from Kafka. This is critical when reading and writing data across security domains such as internal network, public internet, and partner networks.
Client authentication
You can enable client authentication for connections from your application to Kafka brokers. For example, you can define that only specific applications are allowed to connect to your Kafka cluster.
Client authorization
You can enable client authorization of read and write operations by your applications. For example, you can define that only specific applications are allowed to read from a Kafka topic. You can also restrict write access to Kafka topics to prevent data pollution or fraudulent activities.

For more information about the security features in Apache Kafka, see Kafka Security and the blog post Apache Kafka Security 101.

Required ACL setting for secure Kafka clusters

Kafka clusters can use ACLs to control access to resources (like the ability to create topics), and for such clusters each client, including Kafka Streams, is required to authenticate as a particular user in order to be authorized with appropriate access. In particular, when Streams applications are run against a secured Kafka cluster, the principal running the application must have the ACL set so that the application has the permissions to create internal topics. Since all internal topics as well as the embedded consumer group name are prefixed with the application id, it is recommended to use ACLs on prefixed resource pattern to configure control lists to allow client to manage all topics and consumer groups started with this prefix as --resource-pattern-type prefixed --topic <application.id> --operation All (see KIP-277 and KIP-290 for details). For example, given the following setup of your Streams application:

  • Config application.id value is team1-streams-app1.
  • Authenticating with the Kafka cluster as a team1 user.
  • The application’s coded topology reads from input topics input-topic1 and input-topic2.
  • The application’s topology write to output topics output-topic1 and output-topic2.

Then the following commands would create the necessary ACLs in the Kafka cluster to allow your application to operate:

# Allow Streams to read the input topics:
bin/kafka-acls ... --add --allow-principal User:team1 --operation Read --topic input-topic1 --topic input-topic2

# Allow Streams to write to the output topics:
bin/kafka-acls ... --add --allow-principal User:team1 --operation Write --topic output-topic1 --topic output-topic2

# Allow Streams to manage its own internal topics and consumer groups:
bin/kafka-acls ... --add --allow-principal User:team1 --operation All --resource-pattern-type prefixed --topic team1-streams-app1 --group team1-streams-app1

Security example

This example is based on the Confluent blog post Apache Kafka Security 101. The purpose is to configure a Kafka Streams application to enable client authentication and encrypt data-in-transit when communicating with its Kafka cluster.

Tip

A complete demo application is available at SecureKafkaStreamsExample.java in the Confluent Examples repository.

This example assumes that the Kafka brokers in the cluster already have their security setup and that the necessary SSL certificates are available to the application in the local filesystem locations. For example, if you are using Docker then you must also include these SSL certificates in the correct locations within the Docker image.

The snippet below shows the settings to enable client authentication and SSL encryption for data-in-transit between your Kafka Streams application and the Kafka cluster it is reading and writing from:

# Essential security settings to enable client authentication and SSL encryption
bootstrap.servers=kafka.example.com:9093
security.protocol=SSL
ssl.truststore.location=/etc/security/tls/kafka.client.truststore.jks
ssl.truststore.password=test1234
ssl.keystore.location=/etc/security/tls/kafka.client.keystore.jks
ssl.keystore.password=test1234
ssl.key.password=test1234

Configure these settings in the application for your StreamsConfig instance. These settings will encrypt any data-in-transit that is being read from or written to Kafka, and your application will authenticate itself against the Kafka brokers that it is communicating with. Note that this example does not cover client authorization.

// Code of your Java application that uses the Kafka Streams library
Properties settings = new Properties();
settings.put(StreamsConfig.APPLICATION_ID_CONFIG, "secure-kafka-streams-app");
// Where to find secure Kafka brokers.  Here, it's on port 9093.
settings.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka.example.com:9093");
//
// ...further non-security related settings may follow here...
//
// Security settings.
// 1. These settings must match the security settings of the secure Kafka cluster.
// 2. The SSL trust store and key store files must be locally accessible to the application.
settings.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SSL");
settings.put(SslConfigs.SSL_TRUSTSTORE_LOCATION_CONFIG, "/etc/security/tls/kafka.client.truststore.jks");
settings.put(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG, "test1234");
settings.put(SslConfigs.SSL_KEYSTORE_LOCATION_CONFIG, "/etc/security/tls/kafka.client.keystore.jks");
settings.put(SslConfigs.SSL_KEYSTORE_PASSWORD_CONFIG, "test1234");
settings.put(SslConfigs.SSL_KEY_PASSWORD_CONFIG, "test1234");

If you incorrectly configure a security setting in your application, it will fail at runtime, typically right after you start it. For example, if you enter an incorrect password for the ssl.keystore.password setting, an error message similar to this would be logged and then the application would terminate:

# Misconfigured ssl.keystore.password
Exception in thread "main" org.apache.kafka.common.KafkaException: Failed to construct kafka producer
[...snip...]
Caused by: org.apache.kafka.common.KafkaException: org.apache.kafka.common.KafkaException:
   java.io.IOException: Keystore was tampered with, or password was incorrect
[...snip...]
Caused by: java.security.UnrecoverableKeyException: Password verification failed

Monitor your Kafka Streams application log files for such error messages to spot any misconfigured applications quickly.