Wednesday, September 28, 2016

Securing an Apache Kafka broker - part IV

This is the fourth in a series of articles on securing an Apache Kafka broker. The first post looked at how to secure messages and authenticate clients using SSL. The second post built on the first post by showing how to perform authorization using some custom logic. The third post showed how Apache Ranger could be used instead to create and enforce authorization policies for Apache Kafka. In this post we will look at an alternative authorization solution called Apache Sentry.

1) Build the Apache Sentry distribution

First we will build and install the Apache Sentry distribution. Download Apache Sentry (1.7.0 was used for the purposes of this tutorial). Verify that the signature is valid and that the message digests match. Now extract and build the source and copy the distribution to a location where you wish to install it:
  • tar zxvf apache-sentry-1.7.0-src.tar.gz
  • cd apache-sentry-1.7.0-src
  • mvn clean install -DskipTests
  • cp -r sentry-dist/target/apache-sentry-1.7.0-bin ${sentry.home}
Apache Sentry has an authorization plugin for Apache Kafka, amongst other big data projects. In addition it comes with an RPC service which stores authorization privileges in a database. For the purposes of this tutorial we will just configure the authorization privileges in a configuration file locally to the broker. Therefore we don't need to do any further configuration to the distribution at this point.

2) Configure authorization in the broker

Configure Apache Kafka as per the first tutorial. To enable authorization using Apache Sentry we also need to follow these steps. First edit 'config/server.properties' and add:
  • authorizer.class.name=org.apache.sentry.kafka.authorizer.SentryKafkaAuthorizer
  • sentry.kafka.site.url=file:./config/sentry-site.xml
Next copy the jars from the "lib" directory of the Sentry distribution to the Kafka "libs" directory. Then create a new file in the config directory called "sentry-site.xml" with the following content:

This is the configuration file for the Sentry plugin for Kafka. It essentially says that the authorization privileges are stored in a local file, and that the groups for authenticated users should be retrieved from this file. Finally, we need to specify the authorization privileges. Create a new file in the config directory called "sentry.ini" with the following content:

This configuration file contains three separate sections. The "[users]" section maps the authenticated principals to local groups. The "[groups]" section maps the groups to roles, and the "[roles]" section lists the actual privileges. Now we can start the broker as in the first tutorial:
  • bin/kafka-server-start.sh config/server.properties 
3) Test authorization

Now lets test the authorization logic. Start the producer:
  • bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test --producer.config config/producer.properties
Send a few messages to check that the producer is authorized correctly. Now start the consumer:
  • bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test --from-beginning --consumer.config config/consumer.properties --new-consumer
If everything is configured correctly then it should work as in the first tutorial. 

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