kelvk/opa-kafka-plugin

Open Policy Agent (OPA) plugin for Kafka authorization

Open Policy Agent plugin for Kafka authorization

Open Policy Agent (OPA) plugin for Kafka authorization.

Prerequisites

• Kafka 2.3.x (compile from source for other versions)
• Java 11 or above
• OPA installed and running on the brokers

Installation

Download the latest OPA authorizer plugin jar and put the file (opa-authorizer-{$VERSION}-all.jar) somewhere Kafka recognizes it - this could be directly in Kafkas libs directory or in a separate plugin directory pointed out to Kafka at startup, e.g:

CLASSPATH=/usr/local/share/kafka/plugins/*

To activate the opa-kafka-plugin add the authorizer.class.name to server.properties
authorizer.class.name=com.bisnode.kafka.authorization.OpaAuthorizer

The plugin supports the following properties:

Property Key	Example	Default	Description
opa.authorizer.url	http://opa:8181/v1/data/kafka/authz/allow		Name of the OPA policy to query. [required]
opa.authorizer.allow.on.error	false	false	Fail-closed or fail-open if OPA call fails.
opa.authorizer.cache.initial.capacity	5000	5000	Initial decision cache size.
opa.authorizer.cache.maximum.size	50000	50000	Max decision cache size.
opa.authorizer.cache.expire.after.seconds	3600	3600	Decision cache expiry in milliseconds.

Usage

Example structure of input data provided from opa-kafka-plugin to Open Policy Agent.

{
  "operation": {
    "name": "Write"
  },
  "resource": {
    "resourceType": {
      "name": "Topic"
    },
    "name": "alice-topic1"
  },
  "session": {
    "principal": {
      "principalType": "alice-producer"
    },
    "clientAddress": "172.21.0.5",
    "sanitizedUser": "alice-producer"
  }
}

The following table summarizes the supported resource types and operation names.

input.resourceType.name	input.operation.name
Cluster	ClusterAction
Cluster	Create
Cluster	Describe
Group	Read
Group	Describe
Topic	Alter
Topic	Delete
Topic	Describe
Topic	Read
Topic	Write

Policy sample

With the sample policy rego you will out of the box get a structure where an "owner" can one user per type (consumer, producer, mgmt). The owner and user type is separated by -.

• Username structure: <owner>-<type>
• Topic name structure: <owner->.*

Example:
User alice-consumer will be...

• allowed to consume on topic alice-topic1
• allowed to consume on topic alice-topic-test
• denied to produce on any topic
• denied to consume on topic bob-topic

See sample rego

Performance

Performance results of opa-kafka-plugin compared with ACL's and even unauthorized access to Kafka shows that there is a very little trade off when it comes to performance when using either this opa-kafka-plugin or ACL's.

The tests were made with the following setup:

Resources	#
Brokers	3
Partitions per topic	10
Replicas per topic	3
Zookeeper nodes	3

Background noise on one topic with a producer producing 5000 msgs/s with message size of 512b were used in all tests.

opa-kafka-plugin test results

Test #	Records sent	Payload(b)	records/s	MB/sec	avg latency (ms)	latency avg 50th perc (ms)	latency avg 95th perc (ms)	latency avg 99th perc (ms)	latency avg 99,99 perc (ms)
1	102000	666	170	0.11	4.07	1	2	18	748
2	102000	330	170	0.05	2.03	1	2	18	754
3	102000	1200	170	0.19	2.09	1	2	19	946

ACL test results

Test #	Records sent	Payload(b)	records/s	MB/sec	avg latency (ms)	latency avg 50th perc (ms)	latency avg 95th perc (ms)	latency avg 99th perc (ms)	latency avg 99,99 perc (ms)
1	102000	666	170	0.11	3.45	1	4	21	604
2	102000	330	170	0.05	3.21	1	3	22	566
3	102000	1200	170	0.19	3.01	1	3	19	504

No authorization test results

Test #	Records sent	Payload(b)	records/s	MB/sec	avg latency (ms)	latency avg 50th perc (ms)	latency avg 95th perc (ms)	latency avg 99th perc (ms)	latency avg 99,99 perc (ms)
1	102000	666	170	1.11	1.70	1	2	19	128
2	102000	330	170	0.05	2.03	1	2	18	298
3	102000	1200	170	0.19	2.09	1	2	18	332

Build from source

Using gradle wrapper: ./gradlew clean test shadowJar

The resulting jar (with dependencies embedded) will be named opa-authorizer-{$VERSION}-all.jar and stored in build/libs.

Logging

Set log level log4j.logger.com.bisnode=INFO in config/log4j.properties Use DEBUG or TRACE for debugging.

In a busy Kafka cluster it might be good to tweak the cache since it may produce a lot of log entries in Open Policy Agent, especially if decision logs are turned on. If the policy isn't dynamically updated very often it's recommended to cache a lot to improve performance and reduce the amount of log entries.