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  • KIP-208: Add SSL support to Kafka Connect REST interface
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Status

Current state: Approved

Discussion thread: here

JIRA: KAFKA-4029

Pull Request: https://github.com/apache/kafka/pull/4429

Released: 1.1.0

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

Motivation

Kafka Connect has a REST interface for managing and monitoring connectors. Currently this REST interface is using only plain HTTP without any encryption and authentication. This is not ideal because:

  • The interface might be used to transfer sensitive information (e.g. passwords in Kafka Connect connector configurations)
  • Anyone with access to the interface can add connectors (which can forward sensitive messages from Kafka brokers somewhere else)

Extending the REST interface with support for SSL / TLS encryption and SSL / TLS client authentication could address these issues.

Proposed Change

This KIP proposes enabling SSL support in the Jetty HTTP server. Jetty already supports SSL / TLS. So the main work in this KIP will be around enabling and configuring SSL / TLS. 

Users will be able to configure REST listeners using a new configuration option listeners. It will allow to configure the protocol (which will be either HTTP or HTTPS), host and port. Users will be allowed to configure either HTTP listener or HTTPS listener or both. For example:
  listeners=http://myhost:8080,https://myhost:8443
or
  listeners=https://myhost:8443

When the listeners parameter is configured, the existing options rest.host.name and rest.port will be ignored. The fields rest.host.name and rest.port will be marked as deprecated.

The HTTPS listener (when configured in listeners) will by default use the SSL configuration from the ssl.* options. In case the user needs to use different SSL configuration for connecting to Kafka brokers and for the REST interface, the default settings can be overridden by using the prefix listeners.https. - for example:
listeners.https.ssl.keystore.location=/my/path/keystore.jks

The rest.advertised.host.name and rest.advertised.port options will continue to be used as today to specify the connection address which should be used by other workers. In addition a new option rest.advertised.listener will define whether other workers should connect using HTTP or HTTPS protocols. In case HTTPS is selected, the connecting worker will use the SSL configuration from the existing ssl.* options. Even in case when rest.advertised.host.name and rest.advertised.port options are not specified this field will be used to define which protocol should be advertised to other workers in combination with the appropriate hostname and port from the listener field.

This proposal doesn't include any authorization / ACL features. Only encryption and authentication. Authorization / ACLs should be subject of separate KIP in order to keep the scope of this KIP under control. It also doesn't add any other authentication options than SSL/TLS client authentication.

Public Interfaces

Configuration of SSL / TLS for the Kafka Connect REST interface tries to follow the configuration for other SSL / TLS enabled server interfaces. It will be done through the properties configuration file for the distributed Kafka Connect workers.

Following new options will be added:

ParameterDefault valueNote
listenersnullList of REST listeners in the format protocol://host:port,protocol2://host2:port2 where the protocol is one of HTTP and HTTPS.

rest.advertised.listener

null

Configures the listener used for communication between workers. Valid values are either HTTP or HTTPS.

When the listeners configuration is not defined or when it contains HTTP listener, the default value for this field will be HTTP. When the listeners option is configured and contains only HTTPS listener, the default value will be HTTPS.

ssl.client.authnoneValid values are none, requested and required. It will controls whether:
  • the connecting client is required to do SSL/TLS client authentication (required
  • it can decide to skip the SSL/TLS client authentication (requested
  • the SSL/TLS authentication will be completely disabled (none)

This is the only authentication option suggested as part of this KIP.

listeners.https.ssl.* The listeners.https. prefix can be used with any SSL configuration option mentioned below to override the default SSL configuration which is shared with the connections to Kafka broker. In case at least one option with this prefix exists, the implementation will use only SSL options with this prefix and will ignore all options without prefix. In case no option with prefix listeners.https. exists, the options without prefix will be used.

 

Following existing options will be affected by this KIP:

ParameterDefault valueNote
rest.host.namenullWhen listeners option is defined, this field will be ignored.
rest.port8083When listeners option is defined, this field will be ignored.

The rest.host.name and rest.port will be marked as deprecated. The listeners field would be the one preferred for the long term future.

 

Following existing options will be reused by this KIP without any changes:

ParameterDefault valueNote
rest.advertised.host.namenull 
rest.advertised.portnullThis field will be reused without any changes.
ssl.keystore.locationnull 
ssl.keystore.passwordnull 
ssl.keystore.typeJKS 
ssl.key.passwordnull 
ssl.truststore.locationnull 
ssl.truststore.passwordnull 
ssl.truststore.typeJKS 
ssl.enabled.protocolsTLSv1.2,TLSv1.1,TLSv1 
ssl.providernull 
ssl.protocolTLS 
ssl.cipher.suitesnull 
ssl.keymanager.algorithmSunX509 
ssl.secure.random.implementationnull 
ssl.trustmanager.algorithmPKIX 
ssl.endpoint.identification.algorithmnull 


Migration Plan and Compatibility

This KIP is a new implementation and doesn't have any backwards compatibility issues or special requirements on migration from older versions. Existing Kafka Connect installation would work in the same way as before this change. Without the SSL configuration, the REST interface will continue to be configured as today - i.e. without SSL / TLS.

Rejected Alternatives

  • The first version of this KIP suggested only single REST listener - either HTTP or HTTPS. This was changed based on the feedback from the discussion

 

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