Status

Current state: Draft

Discussion thread:

JIRA:

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Kafka adoption is growing day-by-day and it is used by all sizes of organizations serving varied technical and business domains like banking, entertainment, financial technology to name a few. These organizations depending upon their size and domain may have more internal and external InfoSec/AppSec/Compliance standards they have to meet while using Kafka. SSL/TLS communication is very critical part of those standards. While Kafka supports SSL communication sometimes it becomes challenging to use out-of-the-box solution provided by Kafka for SSL/TLS given the organization's needs.

Currently Kafka provides several SSL related configurations that typically starts with 'ssl.' prefix. Those configurations focuses on ability to specify Keystore and Truststores parameters, supply custom java security Providers etc. However as mentioned before there is still room to allow more flexibility/extensibility to allow organizations to fully comply to their requirement without one-off customizations of Kafka.

According to JSSE Documentation SSLContext and SSLEngine are the endpoint classes for the secure connection. Moreover, SSLEngine is created by SSLContext and can be further customized according to the needs. Hence if Kafka provides a way to customize SSLContext and/or SSLEngine it would be a great lever and provide the ultimate extensibility for Kafka users.

This work is influenced by past KIPs (mentioned below) and is a fresh attempt to provide a conclusive solution. It also got more energy from discussion on KIP-486: Support custom way to load KeyStore and TrustStore.

Past KIPs,

KIP-76 Enable getting password from executable rather than passing as plaintext in config files

KIP-383: Pluggable interface for SSL Factory

This KIP proposes the work on top of what has been done already for SSL configuration like KIP-226 - Dynamic Broker Configuration and KIP-492: Add java security providers in Kafka Security config.

Public Interfaces

New ssl configuration

ssl.engine.factory.class - This configuration will take class of the below interface's type and will be used to create javax.net.ssl.SSLEngine object.

Interface for SSLEngineFactory

package org.apache.kafka.common.security.ssl;

import org.apache.kafka.common.network.Mode;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLEngine;
import java.util.Map;
import java.util.Set;

public interface SslEngineFactory {

	/**
     * Creates SSLContext by providing required key material and {@code java.security.SecureRandom}
     *
     * @return	The SSLContext.
     */
	SSLContext createSSLContext();

    /**
     * Creates a new SSLEngine object.
     *
     * @param mode      Whether to use client or server mode.
     * @param peerHost  The peer host to use. This is used in client mode if endpoint validation is enabled.
     * @param peerPort  The peer port to use. This is a hint and not used for validation.
     * @param endpointIdentification Endpoint identification algorithm for client mode.
     * @return          The new SSLEngine.
     */
    SSLEngine create(Mode mode, String peerHost, int peerPort, String endpointIdentification);

    /**
     * Returns the currently used configurations by this engine.
     * @return
     */
    Map<String, Object> currentConfigs();

    /**
     * Returns the reconfigurable configs used by this engine.
     * @return
     */
    Set<String> reconfigurableConfigs();

    /**
     * Returns true if this engine needs to be rebuilt.
     *
     * @param nextConfigs       The configuration we want to use.
     * @return                  True only if this builder should be rebuilt.
     */
    boolean shouldBeRebuilt(Map<String, Object> nextConfigs);
}

Proposed Changes

Currently SslFactory.java uses SslEngineBuilder.java. Instead of that we will modify SslFactory.java to load a class configured via the new configuration 'ssl.engine.factory.class' and delegate the SSLEngine creation call to the implementation. 

We will also provide default implementation for the 'ssl.engine.factory.class' which will be used in absence of provided config.

Default implementation would be along the lines (but not necessarily the same) of - sample code which is copied from current SslEngineBuilder.java.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?

There will be no impact on existing users who do not specify the new configuration.

• If we are changing behavior how will we phase out the older behavior?

No impact

• If we need special migration tools, describe them here.

None

• When will we remove the existing behavior?

Not applicable since old code behavior will be kept with default implementation of DefaultSslEngineFactory.

Rejected Alternatives

TBD