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Authentication using Kerberos

Kerberos is a network authentication protocol designed to provide strong authentication for client applications and server applications by using secret-key cryptography.

In Pulsar, you can use Kerberos with SASL as a choice for authentication. Since Pulsar uses the Java Authentication and Authorization Service (JAAS) for SASL configuration, you need to provide JAAS configurations for Kerberos authentication.

note

Kerberos authentication uses the authenticated principal as the role token for Pulsar authorization. If you've enabled authorizationEnabled, you need to set superUserRoles in broker.conf that corresponds to the name registered in KDC. For example:

superUserRoles=client/{clientIp}@EXAMPLE.COM

Prerequisites​

  • Set up and run a Key Distribution Center(KDC).
  • Install a Kerberos server if your organization doesn't have one. Your Linux vendor might have packages for Kerberos. For how to install and configure Kerberos, see Ubuntu and Redhat.
  • If you use Oracle Java, you need to download JCE policy files for your Java version and copy them to the $JAVA_HOME/jre/lib/security directory.

Enable Kerberos authentication on brokers​

To enable Kerberos authentication on brokers, complete the following steps.

Step 1: Create Kerberos principals​

If you use the existing Kerberos system, ask your Kerberos administrator to obtain a principal for each broker in your cluster and for every operating system user that accesses Pulsar with Kerberos authentication (via clients and CLI tools).

If you have installed your own Kerberos system, you need to create these principals with the following commands:

### add Principals for broker
sudo /usr/sbin/kadmin.local -q 'addprinc -randkey broker/{hostname}@{REALM}'
sudo /usr/sbin/kadmin.local -q "ktadd -k /etc/security/keytabs/{broker-keytabname}.keytab broker/{hostname}@{REALM}"
### add Principals for client
sudo /usr/sbin/kadmin.local -q 'addprinc -randkey client/{hostname}@{REALM}'
sudo /usr/sbin/kadmin.local -q "ktadd -k /etc/security/keytabs/{client-keytabname}.keytab client/{hostname}@{REALM}"

The first part of broker principal (for example, broker in broker/{hostname}@{REALM}) is the serverType of each host. The suggested values of serverType are broker (host machine runs Pulsar broker service) and proxy (host machine runs Pulsar Proxy service).

Note that Kerberos requires that all your hosts can be resolved with their FQDNs.

Step 2: Configure brokers​

In the broker.conf file, set Kerberos-related configurations. Here is an example:

authenticationEnabled=true
authenticationProviders=org.apache.pulsar.broker.authentication.AuthenticationProviderSasl
saslJaasClientAllowedIds=.*client.* ## regex for principals that are allowed to connect to brokers
saslJaasServerSectionName=PulsarBroker ## corresponds to the section in the JAAS configuration file for brokers

# Authentication settings of the broker itself. Used when the broker connects to other brokers, or when the proxy connects to brokers, either in same or other clusters
brokerClientAuthenticationPlugin=org.apache.pulsar.client.impl.auth.AuthenticationSasl
brokerClientAuthenticationParameters={"saslJaasClientSectionName":"PulsarClient", "serverType":"broker"}

To make Pulsar internal admin client work properly, you need to:

  • Set brokerClientAuthenticationPlugin to client plugin AuthenticationSasl;
  • Set brokerClientAuthenticationParameters to value in JSON string {"saslJaasClientSectionName":"PulsarClient", "serverType":"broker"}, in which PulsarClient is the section name in the pulsar_jaas.conf file, and "serverType":"broker" indicates that the internal admin client connects to a broker.

Step 3: Configure JAAS​

JAAS configuration file provides the information to connect KDC. Here is an example named pulsar_jaas.conf:

 PulsarBroker {
   com.sun.security.auth.module.Krb5LoginModule required
   useKeyTab=true
   storeKey=true
   useTicketCache=false
   keyTab="/etc/security/keytabs/pulsarbroker.keytab"
   principal="broker/localhost@EXAMPLE.COM";
};

 PulsarClient {
   com.sun.security.auth.module.Krb5LoginModule required
   useKeyTab=true
   storeKey=true
   useTicketCache=false
   keyTab="/etc/security/keytabs/pulsarclient.keytab"
   principal="client/localhost@EXAMPLE.COM";
};

In the above example:

  • PulsarBroker is a section name in the JAAS file that each broker uses. This section tells the broker to use which principal inside Kerberos and the location of the keytab where the principal is stored.
  • PulsarClient is a section name in the JASS file that each client uses. This section tells the client to use which principal inside Kerberos and the location of the keytab where the principal is stored.

You need to set the pulsar_jaas.conf file path as a JVM parameter. For example:

    -Djava.security.auth.login.config=/etc/pulsar/pulsar_jaas.conf

Step 4: Connect to KDC​

note

If your machines configured with Kerberos already have a system-wide configuration, you can skip this configuration.

The content of krb5.conf file indicates the default Realm and KDC information. See JDK's Kerberos Requirements for more details.

To specify the path to the krb5.conf file for brokers, enter the command below.

-Djava.security.krb5.conf=/etc/pulsar/krb5.conf

Here is an example of the krb5.conf file.

[libdefaults]
 default_realm = EXAMPLE.COM

[realms]
 EXAMPLE.COM  = {
  kdc = localhost:62037
 }

In the above example:

  • EXAMPLE.COM is the default Realm;
  • kdc = localhost:62037 is the KDC server URL for the EXAMPLE.COM Realm.

Enable Kerberos authentication on proxies​

If you want to use proxies between brokers and clients, Pulsar proxies (as a SASL server in Kerberos) will authenticate clients (as a SASL client in Kerberos) before brokers authenticate proxies.

To enable Kerberos authentication on proxies, complete the following steps.

Step 1: Create Kerberos principals​

Add new principals for Pulsar proxies.

### add Principals for Pulsar Proxy
sudo /usr/sbin/kadmin.local -q 'addprinc -randkey proxy/{hostname}@{REALM}'
sudo /usr/sbin/kadmin.local -q "ktadd -k /etc/security/keytabs/{proxy-keytabname}.keytab proxy/{hostname}@{REALM}"

For principals set for brokers and clients, see here.

Step 2: Configure proxies​

In the proxy.conf file, set Kerberos-related configuration.

## related to authenticate client.
authenticationEnabled=true
authenticationProviders=org.apache.pulsar.broker.authentication.AuthenticationProviderSasl
saslJaasClientAllowedIds=.*client.*
saslJaasServerSectionName=PulsarProxy

## related to be authenticated by broker
brokerClientAuthenticationPlugin=org.apache.pulsar.client.impl.auth.AuthenticationSasl
brokerClientAuthenticationParameters={"saslJaasClientSectionName":"PulsarProxy", "serverType":"broker"}
forwardAuthorizationCredentials=true

In the above example:

  • The first part relates to the authentication between clients and proxies. In this phase, clients work as SASL clients, while proxies work as SASL servers.
  • The second part relates to the authentication between proxies and brokers. In this phase, proxies work as SASL clients, while brokers work as SASL servers.

Step 3: Configure JAAS​

Add a new section for proxies in the pulsar_jaas.conf file. Here is an example:

 PulsarProxy {
   com.sun.security.auth.module.Krb5LoginModule required
   useKeyTab=true
   storeKey=true
   useTicketCache=false
   keyTab="/etc/security/keytabs/pulsarproxy.keytab"
   principal="proxy/localhost@EXAMPLE.COM";
};

Configure Kerberos authentication in Java clients​

note

Ensure that the operating system user who starts Pulsar clients can access the keytabs configured in the pulsar_jaas.conf file and the KDC server configured in the krb5.conf file.

  1. In client applications, include pulsar-client-auth-sasl in your project dependency.

        <dependency>
          <groupId>org.apache.pulsar</groupId>
          <artifactId>pulsar-client-auth-sasl</artifactId>
          <version>${pulsar.version}</version>
        </dependency>

  2. Configure the authentication type to use AuthenticationSasl and provide the following parameters.

    • set saslJaasClientSectionName to PulsarClient;
    • set serverType to broker. serverType stands for whether this client connects to brokers or proxies. Clients use this parameter to know which server-side principal should be used.

    The following is an example of configuring a Java client:

    System.setProperty("java.security.auth.login.config", "/etc/pulsar/pulsar_jaas.conf");
    System.setProperty("java.security.krb5.conf", "/etc/pulsar/krb5.conf");

    Map<String, String> authParams = Maps.newHashMap();
    authParams.put("saslJaasClientSectionName", "PulsarClient");
    authParams.put("serverType", "broker");

    Authentication saslAuth = AuthenticationFactory
            .create(org.apache.pulsar.client.impl.auth.AuthenticationSasl.class.getName(), authParams);

    PulsarClient client = PulsarClient.builder()
            .serviceUrl("pulsar://my-broker.com:6650")
            .authentication(saslAuth)
            .build();
    note
    • To configure clients for proxies, you need to set serverType to proxy instead of broker.
    • The first two lines in the above example are hard-coded. Alternatively, you can set additional JVM parameters for pulsar_jaas.conf and krb5.conf files when you run the application like below:
    java -cp -Djava.security.auth.login.config=/etc/pulsar/pulsar_jaas.conf -Djava.security.krb5.conf=/etc/pulsar/krb5.conf $APP-jar-with-dependencies.jar $CLASSNAME

Configure Kerberos authentication in CLI tools​

Command-line tools like pulsar-admin, pulsar-perf, and pulsar-client use the conf/client.conf file in a Pulsar installation.

When using command-line tools, you need to perform the following steps:

  1. Configure the conf/client.conf file.

    authPlugin=org.apache.pulsar.client.impl.auth.AuthenticationSasl
    authParams={"saslJaasClientSectionName":"PulsarClient", "serverType":"broker"}

  2. Set JVM parameters for the pulsar_jaas.conf file and krb5.conf files with additional options.

    -Djava.security.auth.login.config=/etc/pulsar/pulsar_jaas.conf -Djava.security.krb5.conf=/etc/pulsar/krb5.conf

    You can add this at the end of PULSAR_EXTRA_OPTS in the file pulsar_tools_env.sh, or add this line OPTS="$OPTS -Djava.security.auth.login.config=/etc/pulsar/pulsar_jaas.conf -Djava.security.krb5.conf=/etc/pulsar/krb5.conf" directly to the CLI tool script. The meaning of configurations is the same as the meaning of configurations in Java client section.

Configure Kerberos authentication between ZooKeeper and broker​

Pulsar broker acts as a Kerberos client when authenticating with Zookeeper.

  1. Add the settings in conf/zookeeper.conf.

    authProvider.1=org.apache.zookeeper.server.auth.SASLAuthenticationProvider
    requireClientAuthScheme=sasl

  2. Enter the following commands to add a section of Client configurations in pulsar_jaas.conf that Pulsar broker uses:

     Client {
       com.sun.security.auth.module.Krb5LoginModule required
       useKeyTab=true
       storeKey=true
       useTicketCache=false
       keyTab="/etc/security/keytabs/pulsarbroker.keytab"
       principal="broker/localhost@EXAMPLE.COM";
    };

    In this setting, the principal of Pulsar broker and keytab file indicates the role of brokers when you authenticate with ZooKeeper.

For more information, see ZooKeeper document

Configure Kerberos authentication for BookKeeper and broker​

Pulsar broker acts as a Kerberos client when authenticating with Bookie.

  1. Add the bookkeeperClientAuthenticationPlugin parameter in broker.conf.

    bookkeeperClientAuthenticationPlugin=org.apache.bookkeeper.sasl.SASLClientProviderFactory

    SASLClientProviderFactory creates a BookKeeper SASL client in a broker, and the broker uses the created SASL client to authenticate with a Bookie node.

  2. Add a section of BookKeeper configurations in the pulsar_jaas.conf file that broker/proxy uses.

     BookKeeper {
       com.sun.security.auth.module.Krb5LoginModule required
       useKeyTab=true
       storeKey=true
       useTicketCache=false
       keyTab="/etc/security/keytabs/pulsarbroker.keytab"
       principal="broker/localhost@EXAMPLE.COM";
    };

    In this setting, the principal of Pulsar broker and keytab file indicates the role of brokers when you authenticate with Bookie.

For more information, see BookKeeper document.

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