ACLs

Prerequisites

Before you begin, ensure you have administrative access to the WarpStream console and are familiar with the basic concepts of ACLs.

The current version of ACLs supports SASL and mTLS authentication method. Review Authentication for more information.

Important considerations

There are a few things to keep in mind when using ACLs, which are covered below.

ACL Principal

ACLs operate using Principals, which are entities capable of being authenticated by the Authorizer. In the context of WarpStream agents, clients authenticate as a specific principal by using either SASL or mTLS authentication.

With SASL, the principal is identified by one of the three following:

1. The assigned username (prefixed with ccun_)

2. Chosen name during credential creation, (prefixed with ccn_)

3. Chosen name during credential creation, without prefix ccn_

In the screenshot below, valid principal examples include: user_1234, ccn_user_1234, and ccun_3cc6c05a56b396fc084ef1e113150970cd148c87b5f64babfd3b8cf67d4d8840.

With mTLS, the principal is identified from the Distinguished Name(DN) from the client TLS certificate. To use a custom principal, view the mutual TLS authentication page. Importantly, note that mTLS ACL principals don't have to be identified using a valid cluster credential username(ccun_...) or cluster credential name like the SASL ACL principals.

Super users

In the context of ACLs, a 'superuser' is a specially designated user who possesses elevated privileges. Superusers are granted overarching access rights, allowing them to bypass standard ACL restrictions. This includes unrestricted abilities to create, modify, or delete resources, and to manage access controls for other users. In Warpstream you can create super users through the credentials, as explained at SASL Generating Credentials.

For SASL, you can authorize as super user by setting your SASL username as either the generated cluster credentials username(ccun_) or by using the "Name" which you set while generating credentials.

For mTLS, the ACL principal is either the Distinguished Name(DN) from the client TLS certificate, or extracted from the DN according to the -tlsPrincipalMappingRule flag set in the Agents as described in the mutual tls authentication page.

• If you set a tlsPrincipalMappingRule in the Agents, then you need to make sure that the string extracted from the DN which will be used as the ACL principal matches either the "Name" you picked when generating credentials or matches the generated cluster credentials username(ccun_).

• If you don't set a tlsPrincipalMappingRule in the Agents and if you set the "Name" when generating credentials as the DN of your certificate, then the certificate will authorize as superuser.

Caching of ACLs

For performance reasons, ACLs are cached, so changes to ACLs may take between 30 seconds to 1 minute to take effect. Plan accordingly when updating ACLs in a production environment to ensure a smooth transition.

allow.everyone.if.no.acl.found

Warpstream does not implement the allow.everyone.if.no.acl.found Kafka configuration, because:

1. It's not safe for production environments.

2. You can get the equivalent (and safer) behaviour by simply using Super users, who are authorized to access everything.

Enabling and Disabling ACLs

To Enable ACLs

1. Navigate to the WarpStream console.

2. Select the desired Virtual Cluster, for example vcn_default.

3. Click on the ACLs tab.

   
4. You will see the ACLs: Disabled status label if ACLs are currently disabled.

   
5. Click on the Enable ACLs button to change its status to Enabled.

To Disable ACLs

1. Follow the same steps to navigate to the ACLs tab of your Virtual Cluster.

2. If ACLs are enabled, you will see the ACLs: Enabled status label.

3. Click on the Disable ACLs button to turn off ACLs for the cluster.

Enable/Disbable Using the HTTP API

Alternatively, you can switch ACLs on and off using the HTTP APIs, which is a convenient alternative to doing it through the console UI. Refer toDescribeConfiguration and UpdateConfiguration for details.

Generating Credentials

To interact with WarpsSream clusters, you need to generate credentials:

1. Within the WarpStream console, navigate to the Credentials tab of your Virtual Cluster.

2. Click on Generate Credentials.

3. Provide a name for the credentials.

4. If necessary, enable Super User for broader permissions.

   • Important: If a resource has no associated ACLs, then only superusers can access that resource.

5. Click Generate Credentials. The credentials will be displayed for you to use with the CLI.

Managing ACLs via Kafka API

To manage ACLs via the Kafka API, use the Kafka Admin API with appropriate Kafka credentials.

Create an ACL

To create an ACL, use the createAcls method with the required ACL details:

_, err = admin.CreateACLs(
	context.Background(),
	kafka.ACLBindings{{
		Type:                kafka.ResourceTopic,
		Name:                "topic_name",
		ResourcePatternType: kafka.ResourcePatternTypeLiteral,
		Principal:           "User:<credential_username>",
		Host:                "*", // Request can come from any host.
		Operation:           kafka.ACLOperationWrite,
		PermissionType:      kafka.ACLPermissionTypeAllow,
	}},
)
if err != nil {
	fmt.Printf("Failed to create ACLs: %s\n", err.Error())
	os.Exit(1)
}

Delete an ACL

To delete an ACL, use the deleteAcls method with a filter matching the ACL you wish to remove:

_, err = admin.DeleteACLs(
	context.Background(),
	kafka.ACLBindingFilters{{
		Type:                kafka.ResourceTopic,
		Name:                "topic_name",
		ResourcePatternType: kafka.ResourcePatternTypeLiteral,
		Principal:           "User:<credential_username>",
		Host:                "*",
		Operation:           kafka.ACLOperationWrite,
		PermissionType:      kafka.ACLPermissionTypeAllow,
	}},
)
if err != nil {
	fmt.Printf("Failed to delete ACLs: %s\n", err)
	os.Exit(1)
}

The examples above use the librdkafka package from Go. You can also try the bin/kafka-acls.sh script from Apache Kafka®'s official binary release for more hands-on experience:

bin/kafka-acls.sh --bootstrap-server localhost:9092 --remove --allow-principal User:<credential_username> --allow-principal User:Alice --allow-host 198.51.100.0 --allow-host 198.51.100.1 --operation Read --operation Write --topic Test-topic

bin/kafka-acls.sh --bootstrap-server localhost:9092 --add --allow-principal User:Bob --allow-principal User:<credential_username> --allow-host 198.51.100.0 --allow-host 198.51.100.1 --operation Read --operation Write --topic Test-topic

Denied Authorization Logs

Logs for denied authorizations can be enabled by setting the -enableACLLogs flag or WARPSTREAM_ENABLE_ACL_LOGS environment variable to true on the Agents.

Any actions that are denied due to a missing ACL or an explicit DENY ACL will show up in these logs. An example log is below:

{"time":"2025-03-13T13:02:05.176353-05:00","level":"WARN","msg":"ACL Denied Operation on resource","principal":"User:ccun_9c5d...","operation":"CREATE","host":"127.0.0.1:56216","resource_type":"TOPIC","resource_name":"foo"}

In the example above we can see the user User:ccun_9c5d... tried to CREATE a TOPIC called foo and was denied.