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.

Danger

Important: ACLs are only compatible with Agent version 526 and above. Make sure you use a compatible agent version, if your cluster has self-hosted agents.

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/PLAIN or SASL/SCRAM-SHA-512, 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.

New UILegacy UI

With mTLS, the 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.

With SASL/OAUTHBEARER the principal is identified by the subject of the OAuth token.

All principals should be prefixed with User: when creating ACL rules.

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.

For SASL/PLAIN or SASL/SCRAM-SHA-512, 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. You can create super users through the credentials, as explained at SASL Generating Credentials.

For mTLS, you can create super users by clicking the “Create mTLS Super User” button in the Credentials page and entering the certificate DN or TLS principal.

For SASL/OAUTHBEARER, you can create super users by clicking the “Create mTLS Super User” button in the Credentials page and entering the OAuth subject you want to be a super user.

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.

ACL Shadowing

ACL Shadowing allows a WarpStream cluster to evaluate Kafka ACLs against live traffic without enforcing authorization decisions. This mode is designed to help operators validate ACL behavior before enabling full ACL enforcement.

When ACL Shadowing is enabled:

• All incoming requests are evaluated against the cluster’s configured ACLs.
• Authorization results are not enforced (no requests are blocked).
• Would-be denials are logged and surfaced through Diagnostics.

ACL Shadowing can be enabled from the WarpStream Console in the ACLs tab for your cluster or via Terraform.

New UILegacy UI

Note that ACL Shadowing will be automatically disabled when you enable ACLs for your cluster.

Enabling and Disabling ACLs

Danger

Warning

Before enabling ACLs, be aware that improper configurations may lead to denied access for producers and consumers. Make sure to configure ACLs correctly to avoid any disruption of service.

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.

New UILegacy UI

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

New UILegacy UI

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/Disable 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 to DescribeConfiguration 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.

New UILegacy UI

Note

Important: Credentials are shown only once. Store them securely.

Managing ACLs via WarpStream Console

1. Navigate to the WarpStream console.
2. Select the desired Virtual Cluster, for example vcn_default.
3. Click on the ACLs tab.
4. Click “Add ACL Rule”

New UILegacy UI

5. Fill in the rule information. In this example we are creating a TOPIC ACL for topics that match the name foo exactly for the User ccn_user_1234 and allowing that user to WRITE to the topic.

New UILegacy UI

For information on ACL resource types and operations see the Confluent Operation Documentation.

Managing ACLs via Kafka API

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

Managing ACLs via HTTP API

You can create, list, and delete ACLs using the WarpStream HTTP API. See the ACLs API Reference for full endpoint documentation.

Managing ACLs via Terraform

ACLs can be managed using the WarpStream Terraform provider.

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,

    // See above the above ACL Principal section for information.
    Principal:           "User:<credential_principal>",

    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,

    // See above the above ACL Principal section for information.
    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

Using the ANY Resource Type in ACLs

Our system supports creating ACLs with the resource type ANY through the console, API, and Terraform. This differs from standard Apache Kafka, where clients typically cannot create ACLs with resource type ANY and may reject them.

Caution

Warning

Using the ANY resource type is not recommended. It grants permissions across all resources of that type, broadening the attack surface, and can cause compatibility issues with standard Kafka clients, which expect ACLs for specific resource types. Whenever possible, use particular resource types to ensure stricter access control and interoperability.

Denied Authorization Logs

Logs for denied authorizations are enabled by default and can be enable/disabled by setting the -enableACLLogs flag or WARPSTREAM_ENABLE_ACL_LOGS environment variable to true or false 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.