Kafka Connect Security Basics


If you have enabled SSL encryption in your Apache Kafka® cluster, then you must make sure that Kafka Connect is also configured for security. Click on the section to configure encryption in Kafka Connect:

Encryption with SSL


If you have enabled authentication in your Kafka cluster, then you must make sure that Kafka Connect is also configured for security. Click on the section to configure authentication in Kafka Connect:

Separate principals

Within the Connect worker configuration, all properties having a prefix of producer. and consumer. are applied to all source and sink connectors created in the worker. The admin. prefix is used for error reporting in sink connectors. The following describes how these prefixes are used:

  • The consumer. prefix controls consumer behavior for sink connectors.
  • The producer. prefix controls producer behavior for source connectors.
  • Both the producer. and admin. prefixes control producer and client behavior for sink connector error reporting.

You can override these properties for individual connectors using the producer.override., consumer.override., and admin.override. prefixes. This includes overriding the worker service principal configuration to create separate service principals for each connector. Overrides are disabled by default. They are enabled using the connector.client.config.override.policy worker property. This property sets the per-connector overrides the worker permits. The out-of-the-box (OOTB) options for the override policy are:

  • connector.client.config.override.policy=None
    Default. Does not allow any configuration overrides.
  • connector.client.config.override.policy=Principal
    Allows overrides for the security.protocol, sasl.jaas.config, and sasl.mechanism configuration properties, using the producer.override., consumer.override, and admin.override prefixes.
  • connector.client.config.override.policy=All
    Allows overrides for all configuration properties using the producer.override., consumer.override, and admin.override prefixes.


You can write your own implementation of the ConnectorClientConfigOverridePolicy class if any of the OOTB policies don’t meet your needs.

If your Kafka broker supports client authentication over SSL, you can configure a separate principal for the worker and the connectors. In this case, you need to generate a separate certificate for each of them and install them in separate keystores.

The key Connect configuration differences are as follows, notice the unique password, keystore location, and keystore password:

# Authentication settings for Connect workers

Connect workers manage the producers used by source connectors and the consumers used by sink connectors. So, for the connectors to leverage security, you also have to override the default producer/consumer configuration that the worker uses.

# Authentication settings for Connect producers used with source connectors

# Authentication settings for Connect consumers used with sink connectors

ACL Considerations

Using separate principals for the connectors allows you to define access control lists (ACLs) with finer granularity. For example, you can use this capability to prevent the connectors themselves from writing to any of internal topics used by the Connect cluster. Additionally, you can use different keystores for source and sink connectors and enable scenarios where source connectors have only write access to a topic but sink connectors have only read access to the same topic.

Worker ACL Requirements

Workers must be given access to the common group that all workers in a cluster join, and to all the internal topics required by Connect. Read and write access to the internal topics are always required, but create access is only required if the internal topics don’t yet exist and Kafka Connect is to automatically create them. The table below shows each required permission and the relevant configuration setting used to define its value.

Operation(s) Resource Configuration Item
Create Cluster config.storage.topic
Create Cluster config.storage.replication.factor
Create Cluster offset.storage.topic
Create Cluster offset.storage.partitions
Create Cluster offset.storage.replication.factor
Create Cluster status.storage.topic
Create Cluster status.storage.partitions
Create Cluster status.storage.replication.factor
Read/Write Topic config.storage.topic
Read/Write Topic offsets.storage.topic
Read/Write Topic status.storage.topic
Read Group group.id

See Adding ACLs for documentation on creating new ACLs from the command line.

Connector ACL Requirements

Source connectors must be given WRITE permission to any topics that they need to write to. Similarly, sink connectors need READ permission to any topics they will read from. They also need Group READ permission since sink tasks depend on consumer groups internally. Connect defines the consumer group.id conventionally for each sink connector as connect-{name} where {name} is substituted by the name of the connector. For example, if your sink connector is named “hdfs-logs” and it reads from a topic named “logs,” then you could add an ACL with the following command:

bin/kafka-acls --bootstrap-server localhost:9092 --command-config adminclient-configs.conf \
 --add --allow-principal User:<Sink Connector Principal> \
 --consumer --topic logs --group connect-hdfs-logs

Connectors that access the _confluent-command topic must configure the following ACLs:

  • CREATE and DESCRIBE on the resource cluster, if the connector needs to create the topic.
  • DESCRIBE, READ, and WRITE on the _confluent-command topic.

See License topic ACLs for details about configuring ACLs for the _confluent-command topic.

Enterprise Connector ACL Requirements

The _confluent-command topic contains the license that corresponds to the license key supplied through the confluent.license property and is created by default. Connectors that access the _confluent-command topic must have the following ACLs configured:

  • CREATE and DESCRIBE on the resource cluster, if the connector needs to create the topic.
  • DESCRIBE, READ, and WRITE on the _confluent-command topic.

Connect Reporter

The Kafka Connect Reporter submits the result of a sink operation to a reporter topic. After successfully sinking a record or following an error condition, the Connect Reporter is called to submit the result report. The report is constructed to include details about how the original record was handled along with additional information about the sink event. These records are written to configurable success and error topics for further consumption. The following is an example of the basic Connect Reporter configuration properties added to a sink connector configuration:


To completely disable Connect Reporter, see Disabling Connect Reporter.

If you have a secure environment, you use configuration blocks for both an Admin Client and Producer. A Producer is constructed to send records to the reporter topic. The Admin Client creates the topic. Credentials need to be added in a secure environment. Example Admin and Producer properties are shown below:

reporter.admin.sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule \
required username="<username>" password="<password>";

reporter.producer.sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule \
required username="<username>" password="<password>";

Additional Reporter configuration property examples are provided in each applicable Kafka Connect sink connector document. For an example, see the Reporter properties in the HTTP Sink connecter.

Reporter and Kerberos security

The following configuration example shows a sink connector with all the necessary configuration properties for Reporter and Kerberos security. This example shows the Prometheus Metrics Sink Connector for Confluent Platform, but can be modified for any applicable sink connector.


  "name" : "prometheus-connector",
  "config" : {
    "connector.class" : "io.confluent.connect.prometheus.PrometheusMetricsSinkConnector",
    "tasks.max" : "1",
    "confluent.topic.replication.factor": "3",
    "confluent.topic.sasl.jaas.config":"com.sun.security.auth.module.Krb5LoginModule required \nuseKeyTab=true \nstoreKey=true \nkeyTab=\"/etc/security/keytabs/svc.kfkconnect.lab.keytab\" \nprincipal=\"svc.kfkconnect.lab@DS.DTVENG.NET\";",
    "prometheus.scrape.url": "http://localhost:8889/metrics",
    "value.converter": "org.apache.kafka.connect.json.JsonConverter",
    "value.converter.schemas.enable": "false",
    "behavior.on.error": "LOG",
    "reporter.result.topic.replication.factor": "3",
    "reporter.error.topic.replication.factor": "3",
    "reporter.producer.sasl.jaas.config":"com.sun.security.auth.module.Krb5LoginModule required \nuseKeyTab=true \nstoreKey=true \nkeyTab=\"/etc/security/keytabs/svc.kfkconnect.lab.keytab\" \nprincipal=\"svc.kfkconnect.lab@DS.DTVENG.NET\";",
    "reporter.admin.sasl.jaas.config":"com.sun.security.auth.module.Krb5LoginModule required \nuseKeyTab=true \nstoreKey=true \nkeyTab=\"/etc/security/keytabs/svc.kfkconnect.lab.keytab\" \nprincipal=\"svc.kfkconnect.lab@DS.DTVENG.NET\";",
    "confluent.license":"eyJ0eXAiOiJK ...omitted"


Role-Based Access Control

If your organization has enabled Role-Based Access Control (RBAC), you need to review your user principal, RBAC role, and RBAC role permissions before performing any Kafka Connect or Apache Kafka® cluster operations. Refer to Kafka Connect and RBAC to learn more about how RBAC is configured for Kafka Connect to protect your Kafka cluster.

Externalizing Secrets

You can use the ConfigProvider class interface to prevent secrets from appearing in cleartext in connector configurations.

The ConfigProvider class interface allows you to use variables in your worker configuration that are dynamically resolved upon startup. It also allows you to use variables in your connector configurations that are dynamically resolved when the connector is (re)started. You can use variables within configuration property values in place of secrets, or in place of any information that should be resolved dynamically at runtime.


Connector configurations are persisted and shared over the Connect REST API with the variables. Only when the connector starts does it transiently resolve and replace variables in-memory. Secrets are never persisted in connector configs, logs, or in REST API requests and responses.

The Connect worker relies upon the named ConfigProviders defined in the worker configuration to resolve the variables. Each variable specifies the name of the ConfigProvider that should be used, and the information the ConfigProvider uses to resolve the variable into a replacement string.

All ConfigProvider implementations are discovered using the standard Java ServiceLoader mechanism. To create a custom implementation of ConfigProvider, implement the ConfigProvider interface. Package the implementation class(es) and a file named META-INF/services/org.apache.kafka.common.config.provider.ConfigProvider containing the fully qualified name of the ConfigProvider implementation class into a JAR file. Note that the JAR file can use third-party libraries other than those provided by the Connect framework, but they must be installed with the JAR file as described below.

To install the custom implementation, add a new subdirectory containing the JAR files to the directory that is in Connect’s plugin.path and (re)start the Connect workers.

To implement a custom ConfigProvider, add a new subdirectory containing the JAR files under the default CLASSPATH location—for example, /usr/local/share/java—and restart the Connect workers. Note that the JAR files should not be placed under a subdirectory in Connect’s plugin.path. The plugin.path locations are for connectors and their specific dependent JARs and not for config.providers.

When the Connect worker starts, it instantiates all ConfigProvider implementations specified in the worker configuration. All properties prefixed with config.providers.[provider].param.* are passed to the configure() method of the ConfigProvider. When the Connect worker shuts down, it calls the close() method of the ConfigProvider.


Any worker in a Connect cluster must be able to resolve every variable in the worker configuration, and must be able to resolve all variables used in every connector configuration. This requires the following:

  • All of the workers in a Connect cluster must have the same set of named config providers.
  • Each provider on every worker must have access to any resources required to resolve variables used in the worker config or in the connector configs.

The following configuration properties are added to the distributed worker configuration to make this work:

  • config.providers: A comma-separated list of names for providers.
  • config.providers.{name}.class: The Java class name for a provider.
  • config.providers.{name}.param.{param-name}: A parameter (or parameters) to be passed to the above Java class on initialization.


Kafka provides an implementation of ConfigProvider called FileConfigProvider that allows variable references to be replaced with values from local files on each worker. For example, rather than having a secret in a configuration property, you can put the secret in a local file and use a variable in connector configurations. When the connector is started, Connect will use the file config provider to resolve and replace the variable with the actual secret, ensuring that the connector configuration does not include the secret when it is persisted and shared over the Connect REST API.


Every worker in the Connect cluster must have access to the files referenced by all variables referencing the config provider.

Variables that refer by name to a FileConfigProvider should be in the form ${provider:[path:]key}. The path is the fully-qualified path of the property file on each Connect worker; the key is the name of the key within that property file. Note that the FileConfigProvider supports reading any file, where the path (and property key in that file) is specified in each variable. When Connect resolves one of these variables, it will read the properties file, extract the value for the corresponding key, and replace the whole variable with that value.

The following shows a JDBC connector configuration that includes the database URL, username, and password:


Instead of having these details exposed in the connector configuration, you can use FileConfigProvider and store them in a file accessible to each Connect worker and protect them from other OS users. In the following examples, the separate file is named /opt/connect-secrets.properties. The properties added to /opt/connect-secrets.properties are listed below:


Then, you can configure each Connect worker to use FileConfigProvider. The worker configuration would include the following properties:

# Additional properties added to the worker configuration


The JDBC connector configuration can now use variables in place of the secrets:

# Additional properties added to the connector configuration


Another connector configuration could use variables with a different file, or variables that use different properties in the same file:

# Additional properties added to another connector configuration



Confluent Platform provides another implementation of ConfigProvider named InternalSecretConfigProvider which is used with the Connect Secret Registry. The InternalSecretConfigProvider requires Role-based access control (RBAC) with Secret Registry. The Secret Registry is a secret serving layer that enables Connect to store encrypted Connect credentials in a topic exposed through a REST API. This eliminates any unencrypted credentials being located in the actual connector configuration. The following example shows how InternalSecretConfigProvider is configured in the worker configuration file:

### Secret Provider


config.providers.secret.param.master.encryption.key=<encryption key>
config.providers.secret.param.kafkastore.bootstrap.servers=SASL_PLAINTEXT://<Kafka broker URLs>
config.providers.secret.param.kafkastore.sasl.jaas.config=org.apache.kafka.common.security.oauthbearer.OAuthBearerLoginModule required \
  username="<service-principal-username>" \
  password="<service-principal-password>" \
  metadataServerUrls="<metadata server URLs>";

Using Secrets with a JSON Connector Configuration

Use the following steps to use encrypted secrets for a connector JSON configuration.

  1. Create the security.properties file to store the master encryption key. You can use an existing security.properties file if the Secrets feature is already enabled for the Confluent Platform environment. Note that secrets are managed using confluent secret commands.

  2. If you created a new security.properties file, create a directory to store the file. For example:

    mkdir /usr/secrets

    Choose a location for the secrets file on the local host and not a location where Confluent Platform services run. The secrets file contains encrypted secrets for the master encryption key, data encryption key, configuration parameters, and metadata such as the cipher used for encryption.

  3. Generate the master encryption key based on a passphrase. For example:

    confluent secret master-key generate \
    --local-secrets-file /usr/secrets/security.properties \
    --passphrase @<passphrase.txt>
  4. Save the master key. It cannot be retrieved later.

    | Master Key | abc123def456ghi789JKLMNOP012346Qrst789123ab= |
  5. Export the master key using the following environment variable. You can also add the master key to a bash script. If the master key is not exported, any subsequent secret commands will fail.

    export CONFLUENT_SECURITY_MASTER_KEY=abc123def456ghi789JKLMNOP012346Qrst789123ab=
  6. Create a working properties file that contains only the properties you want to encrypt. The name of the file is not important. It’s used to create the property key and encrypted secret added to the security.properties file. For example, create my-jdbc-connector.properties with the following secret:

  7. Encrypt the properties in the working my-jdbc-connector.properties file.

    confluent secret file encrypt --config-file my-jdbc-connect.properties \
    --local-secrets-file /usr/secrets/security.properties \
    --remote-secrets-file /usr/secrets/security.properties \
    --config "database.password"

    This command updates the /usr/secrets/security.properties file with the encrypted database.password. For example:

    my-jdbc-connector.properties/database.password = ENC[AES/CBC/PKCS5Padding,data:CUpHh5lRDfIfqaL49V3iGw==,iv:vPBmPkctA+yYGVQuOFmQJw==,type:str]

    You use the property key (that is, my-jdbc-connector.properties/database.password) in the connector configuration. The working properties file my-jdbc-connector.properties file can be discarded.

  8. Distribute the updated security.properties file to all Connect worker nodes where you want the connector to run. This assumes that Connect is configured and restarted using the master password.

  9. Add the variable in place of the secret to the JSON connector configuration file. The variable is in the form {{$ {securepass:<path-to-secret-file>:<secret-key>} }}, where <path-to-secret-file> is the path to the shared security.properties file containing the encrypted secret. For example:

      "name": "my-jdbc-connector",
      "config": {
          "connector.class": "io.confluent.connect.jdbc.JdbcSourceConnector",
          "connection.url": "jdbc:oracle:thin:@//xx.xx.xx.xx:xxxx/xe",
          "connection.user": "<username>",
          "connection.password": "${securepass:/usr/secrets/security.properties:my-jdbc-connector.properties/database.password}",
          "mode": "bulk",
          "query": "select * from Foo"

    You can use any number of secrets in the connector configuration file. The variables are generally set to the entire configuration property value as shown in the example configuration above.

  10. Enable externalized secrets in the distributed Connect worker properties.

    ### enable Externalized Secrets ###
  11. Deploy the connector using the JSON configuration file.

    When Connect starts the connector, it resolves the variable by looking up the secret with a matching secret key in the secrets file, uses the master key to decrypt the secret, replaces the variable(s) with the decrypted secret(s), and passes this configuration to the connector.

Configuring the Connect REST API for HTTP or HTTPS

By default you can make REST API calls over HTTP with Kafka Connect. You can also configure Connect to allow either HTTP or HTTPS, or both.

The listeners configuration parameter determines the protocol used by Kafka Connect. This configuration should contain a list of listeners in this format: protocol://host:port,protocol2://host2:port2. For example:


By default, if no listeners are specified, the REST server runs on port 8083 using the HTTP protocol. When using HTTPS, the configuration must include the SSL configuration. By default, it will use the ssl.* settings. You can use a different configuration for the REST API than for the Kafka brokers, by using the listeners.https prefix. If you use the listeners.https prefix, the ssl.* options are ignored.

You can use the following fields to configure HTTPS for the REST API:

  • ssl.keystore.location
  • ssl.keystore.password
  • ssl.keystore.type
  • ssl.key.password
  • ssl.truststore.location
  • ssl.truststore.password
  • ssl.truststore.type
  • ssl.enabled.protocols
  • ssl.provider
  • ssl.protocol
  • ssl.cipher.suites
  • ssl.keymanager.algorithm
  • ssl.secure.random.implementation
  • ssl.trustmanager.algorithm
  • ssl.endpoint.identification.algorithm
  • ssl.client.auth

For more information, see Distributed Worker Configuration.

The REST API is used to monitor and manage Kafka Connect and for Kafka Connect cross-cluster communication. Requests that are received on the follower nodes REST API are forwarded on to the leader node REST API. If the URI host is different from the URI that it listens on, you can change the URI with the rest.advertised.host.name, rest.advertised.port and rest.advertised.listener configuration options. This URI will be used by the follower nodes to connect with the leader.

When using both HTTP and HTTPS listeners, you can use the rest.advertised.listener option to define which listener is used for the cross-cluster communication. When using HTTPS for communication between nodes, the same ssl.* or listeners.https options are used to configure the HTTPS client.

These are the currently supported REST API endpoints:

  • GET /connectors - Return a list of active connectors.
  • POST /connectors - Create a new connector; the request body should be a JSON object containing a string name field and an object configuration field with the connector configuration parameters.
  • GET /connectors/{name} - Get information about a specific connector.
  • GET /connectors/{name}/config - Get the configuration parameters for a specific connector.
  • PUT /connectors/{name}/config - Update the configuration parameters for a specific connector.
  • GET /connectors/{name}/status - Get the current status of the connector, including whether it is running, failed, or paused; which worker it is assigned to, error information if it has failed, and the state of all its tasks.
  • GET /connectors/{name}/tasks - Get a list of tasks currently running for a connector.
  • GET /connectors/{name}/tasks/{taskid}/status - Get current status of the task, including if it is running, failed, or paused; which worker it is assigned to, and error information if it has failed.
  • PUT /connectors/{name}/pause - Pause the connector and its tasks, which stops message processing until the connector is resumed.
  • PUT /connectors/{name}/resume - Resumes a paused connector or does nothing if the connector is not paused.
  • POST /connectors/{name}/restart - Restart a connector. This is typically used because it has failed.
  • POST /connectors/{name}/tasks/{taskId}/restart - Restart an individual task. This is typically used because it has failed.
  • DELETE /connectors/{name} - Delete a connector, halting all tasks and deleting its configuration.

You can also use Kafka Connect REST API to get information about connector plugins:

  • GET /connector-plugins - Returns a list of connector plugins installed in the Kafka Connect cluster. The API only checks for connectors on the worker that handles the request. This means you might see inconsistent results, especially during a rolling upgrade if you add new connector JARs.
  • PUT /connector-plugins/{connector-type}/config/validate - Validate the provided configuration values against the configuration definition. This API performs perconfigurationvalidation, returns suggested values and error messages during validation.

For more information, see REST API.

For demo of Kafka Connect configured with an HTTPS endpoint, and Confluent Control Center connecting to it, check out Confluent Platform demo.