:_mod-docs-content-type: CONCEPT

To configure custom client authentication, set the `type` property to `custom`.
Custom client authentication allows you to use any type of Kafka-supported authentication mechanism.
This authentication option is especially useful with third-party Apache Kafka services, such as Amazon MSK, that require their own authentication mechanisms.

.Example custom client authentication configuration using the `AWS_MSK_IAM` authentication
[source,yaml,subs="attributes+"]
----
  authentication:
    type: custom
    sasl: true
    config:
      sasl.mechanism: AWS_MSK_IAM
      sasl.jaas.config: software.amazon.msk.auth.iam.IAMLoginModule required;
      sasl.client.callback.handler.class: software.amazon.msk.auth.iam.IAMClientCallbackHandler
----

The `config` section accepts only options that start with the prefixes `sasl.` and `ssl.keystore.`.
All other options are ignored.
To configure additional options, use the related properties of the Strimzi custom resource, such as `.spec.config` or `.spec.tls`.
The `security.protocol `setting is generated automatically from the `sasl` property (when you use `custom` authentication) and the `tls` configuration in the same Strimzi custom resource:

* SASL = True, TLS = True -> SASL_SSL
* SASL = False, TLS = True -> SSL
* SASL = True, TLS = False -> SASL_PLAINTEXT
* SASL = False, TLS = False -> PLAINTEXT

= Using secrets in custom authentication

If your custom authentication mechanism requires additional information from `Secret` or `ConfigMap` resources, use the link:{BookURLConfiguring}#con-common-configuration-volumes-reference[Additional Volumes^] feature to mount them into the operands.
Kafka configuration providers can be used to load them from the disk.

= Using additional authentication plugins

Custom authentication mechanisms might require additional plugins for the operand.
You can add them using the link:{BookURLConfiguring}#con-common-configuration-volumes-reference[Additional Volumes^] feature.
Alternatively, you can build a custom container image.
