Security

Authentication

Currently the only supported authentication mechanism is Kerberos, which is disabled by default. For Kerberos to work a Kerberos KDC is needed, which the users needs to provide. The secret-operator documentation states which kind of Kerberos servers are supported and how they can be configured.

Kerberos is supported starting from HDFS version 3.3.x

1. Prepare Kerberos server

To configure HDFS to use Kerberos you first need to collect information about your Kerberos server, e.g. hostname and port. Additionally you need a service-user, which the secret-operator uses to create create principals for the HDFS services.

2. Create Kerberos SecretClass

Afterwards you need to enter all the needed information into a SecretClass, as described in secret-operator documentation. The following guide assumes you have named your SecretClass kerberos-hdfs.

3. Configure HDFS to use SecretClass

The last step is to configure your HdfsCluster to use the newly created SecretClass.

spec:
  clusterConfig:
    authentication:
      tlsSecretClass: tls # Optional, defaults to "tls"
      kerberos:
        secretClass: kerberos-hdfs # Put your SecretClass name in here

The kerberos.secretClass is used to give HDFS the possibility to request keytabs from the secret-operator.

The tlsSecretClass is needed to request TLS certificates, used e.g. for the Web UIs.

4. Verify that Kerberos is used

Use stackablectl services list --all-namespaces to get the endpoints where the HDFS namenodes are reachable. Open the link (note that the namenode is now using https). You should see a Web UI similar to the following:

hdfs webui kerberos

The important part is

Security is on.

You can also shell into the namenode and try to access the file system: kubectl exec -it hdfs-namenode-default-0 -c namenode — bash -c 'kdestroy && bin/hdfs dfs -ls /'

You should get the error message org.apache.hadoop.security.AccessControlException: Client cannot authenticate via:[TOKEN, KERBEROS].

5. Access HDFS

In case you want to access your HDFS it is recommended to start up a client Pod that connects to HDFS, rather than shelling into the namenode. We have an integration test for this exact purpose, where you can see how to connect and get a valid keytab.

Authorization

We currently don’t support authorization yet. In the future support will be added by writing an opa-authorizer to match our general OPA authorization mechanisms.

In the meantime a very basic level of authorization can be reached by using configOverrides to set the hadoop.user.group.static.mapping.overrides property. In thew following example the dr.who=;nn=;nm=;jn=; part is needed for HDFS internal operations and the user testuser is granted admin permissions.

spec:
  nameNodes:
    configOverrides: &configOverrides
      core-site.xml:
        hadoop.user.group.static.mapping.overrides: "dr.who=;nn=;nm=;jn=;testuser=supergroup;"
  dataNodes:
    configOverrides: *configOverrides
  journalNodes:
    configOverrides: *configOverrides

Wire encryption

In case kerberos is enabled, Privacy mode is used for best security. Wire encryption without kerberos as well as other wire encryption modes are not supported.