Configuring Flink Authentication and Encryption

Security Authentication

Flink supports the following authentication modes:

Kerberos authentication: It is used between the Flink Yarn client and Yarn ResourceManager, JobManager and ZooKeeper, JobManager and HDFS, TaskManager and HDFS, Kafka and TaskManager, as well as TaskManager and ZooKeeper.
Security cookie authentication: Security cookie authentication is used between Flink Yarn client and JobManager, JobManager and TaskManager, as well as TaskManager and TaskManager.

Internal authentication of Yarn: The Internal authentication mechanism of Yarn is used between Yarn ResourceManager and ApplicationMaster (AM).

Flink JobManager and Yarn ApplicationMaster are in the same process.
If Kerberos authentication is enabled for the user's cluster, Kerberos authentication is required.
For versions earlier than MRS 3.x, Flink does not support security cookie authentication.

**Table 1** Authentication modes
Authentication Mode	Description	Configuration Method
Kerberos authentication	Currently, only keytab authentication mode is supported.	Download the user keytab file from FusionInsight Manager and save the keytab file to a folder on the host where the Flink client is located. Configure the following parameters in the flink-conf.yaml file: Keytab path security.kerberos.login.keytab: /home/flinkuser/keytab/abc222.keytab Note: /home/flinkuser/keytab/abc222.keytab indicates the user directory. Principal name security.kerberos.login.principal: abc222 In HA mode, if ZooKeeper is configured, the Kerberos authentication configuration items must be configured as follows: zookeeper.sasl.disable: false security.kerberos.login.contexts: Client If you want to perform Kerberos authentication between Kafka client and Kafka broker, set the value as follows: security.kerberos.login.contexts: Client,KafkaClient
Security cookie authentication	-	Generate the generate_keystore.sh script by referring to Example of Issuing a Certificate and place it in the bin directory of the Flink client. In the bin directory of the Flink client, run the generate_keystore.sh script to generate security cookie, flink.keystore, and flink.truststore. Run the sh generate_keystore.sh command and enter the user-defined password. The password cannot contain #. NOTE: After the script is executed, the flink.keystore and flink.truststore files are generated in the conf directory on the Flink client. In the flink-conf.yaml file, default values are specified for following parameters: Set security.ssl.keystore to the absolute path of the flink.keystore file. Set security.ssl.truststore to the absolute path of the flink.truststore file. Set security.cookie to a random password automatically generated by the generate_keystore.sh script. By default, security.ssl.encrypt.enabled: false is set in the flink-conf.yaml file by default. The generate_keystore.sh script sets security.ssl.key-password, security.ssl.keystore-password, and security.ssl.truststore-password to the password entered when the generate_keystore.sh script is called. There can be security risks if a configuration file contains the authentication password. You are advised to delete the configuration file or use other secure methods to keep the password. Check whether Security Cookie is enabled. That is, check security.enable: true in the flink-conf.yaml file and check whether security cookie is configured. An example is as follows: security.cookie: ae70acc9-9795-4c48-ad35-8b5adc8071744f605d1d-2726-432e-88ae-dd39bfec40a9 NOTE: Obtain the SSL certificate and save it to the Flink client. For details, see Example of Issuing a Certificate. The validity period of the SSL certificate obtained by using the generate_keystore.sh script preset on the MRS client is 5 years. The validity period of the SSL certificate obtained by referring to Example of Issuing a Certificate is 10 years. To disable the default SSL authentication mode, set security.ssl.enabled to false in the flink-conf.yaml file and comment out security.ssl.key-password, security.ssl.keystore-password, security.ssl.keystore, security.ssl.truststore-password, and security.ssl.trustore.
Internal authentication of Yarn	This authentication mode does not need to be configured by the user.	-

One Flink cluster supports only one user. One user can create multiple Flink clusters.

Encrypted Transmission

Flink supports three encrypted transmission modes:

Encrypted transmission inside Yarn: It is used between the Flink Yarn client and Yarn ResourceManager, as well as Yarn ResourceManager and JobManager.
SSL transmission: SSL transmission is used between Flink Yarn client and JobManager, JobManager and TaskManager, as well as TaskManager and TaskManager.
Encrypted transmission inside Hadoop: The internal encrypted transmission mode of Hadoop used between JobManager and HDFS, TaskManager and HDFS, JobManager and ZooKeeper, as well as TaskManager and ZooKeeper.

Configuration about SSL encrypted transmission is mandatory while configuration about encryption of Yarn and Hadoop is not required.

To configure SSL encrypted transmission, configure the following parameters in the flink-conf.yaml file on the client:

Enable SSL and configure the SSL encryption algorithm. For MRS 3.x or later, see Table 2. Modify the parameters as required.

**Table 2** Parameter description
Parameter	Example Value	Description
security.ssl.enabled	true	Enable SSL.
akka.ssl.enabled	true	Enable Akka SSL.
blob.service.ssl.enabled	true	Enable SSL for the Blob channel.
taskmanager.data.ssl.enabled	true	Enable SSL transmissions between TaskManagers.
security.ssl.algorithms	TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384	Configure the SSL encryption algorithm.

For versions earlier than MRS 3.x, see Table 3.

**Table 3** Parameter description
Parameter	Example Value	Description
security.ssl.internal.enabled	true	Enable internal SSL.
akka.ssl.enabled	true	Enable Akka SSL.
blob.service.ssl.enabled	true	Enable SSL for the Blob channel.
taskmanager.data.ssl.enabled	true	Enable SSL transmissions between TaskManagers.
security.ssl.algorithms	TLS_RSA_WITH_AES128CBC_SHA256	Configure the SSL encryption algorithm.

For versions earlier than MRS 3.x, the following parameters in Table 4 do not exist in the default Flink configuration of MRS. If you want to enable SSL for external connections, add the following parameters. After SSL for external connection is enabled, the native Flink page cannot be accessed using a Yarn proxy, because the Yarn open-source version cannot process HTTPS requests using a proxy. However, you can create a Windows VM in the same VPC of the cluster and access the native Flink page from the VM.

**Table 4** Parameter description
Parameter	Example Value	Description
security.ssl.rest.enabled	true	Enable external SSL. If this parameter is set to true, set the related parameters by referring to Table 4.
security.ssl.rest.keystore	${path}/flink.keystore	Path for storing the keystore.
security.ssl.rest.keystore-password	-	A user-defined password of keystore.
security.ssl.rest.key-password	-	A user-defined password of the SSL key.
security.ssl.rest.truststore	${path}/flink.truststore	Path for storing the truststore.
security.ssl.rest.truststore-password	-	A user-defined password of truststore.

Enabling SSL for data transmission between TaskManagers may pose great impact on the system performance.
There can be security risks if a configuration file contains the authentication password. You are advised to delete the configuration file or use other secure methods to keep the password.

Generate the generate_keystore.sh script by referring to Example of Issuing a Certificate and place it in the bin directory of the Flink client. In the bin directory of the Flink client, run the sh generate_keystore.sh <password> command. For details, see Configuring Flink Authentication and Encryption. The configuration items in Table 5 are set by default for MRS 3.x or later. You can also configure them manually.

**Table 5** Parameter description
Parameter	Example Value	Description
security.ssl.keystore	${path}/flink.keystore	Path for storing the keystore. flink.keystore indicates the name of the keystore file generated by the generate_keystore.sh* tool.
security.ssl.keystore-password	-	A user-defined password of keystore.
security.ssl.key-password	-	A user-defined password of the SSL key.
security.ssl.truststore	${path}/flink.truststore	Path for storing the truststore. flink.truststore indicates the name of the truststore file generated by the generate_keystore.sh* tool.
security.ssl.truststore-password	-	A user-defined password of truststore.

For versions earlier than MRS 3.x, the generate_keystore.sh command is generated automatically, and the configuration items in Table 6 are set by default. You can also configure them manually.

**Table 6** Parameter description
Parameter	Example Value	Description
security.ssl.internal.keystore	${path}/flink.keystore	Path for storing the keystore. flink.keystore indicates the name of the keystore file generated by the generate_keystore.sh* tool.
security.ssl.internal.keystore-password	-	A user-defined password of keystore.
security.ssl.internal.key-password	-	A user-defined password of the SSL key.
security.ssl.internal.truststore	${path}/flink.truststore	Path for storing the truststore. flink.truststore indicates the name of the truststore file generated by the generate_keystore.sh* tool.
security.ssl.internal.truststore-password	-	A user-defined password of truststore.

For versions earlier than MRS 3.x, if SSL for external connections is enabled, that is, security.ssl.rest.enabled is set to true, you need to configure the parameters listed in Table 7.

**Table 7** Parameters
Parameter	Example Value	Description
security.ssl.rest.enabled	true	Enable external SSL. If this parameter is set to true, set the related parameters by referring to Table 7.
security.ssl.rest.keystore	${path}/flink.keystore	Path for storing the keystore.
security.ssl.rest.keystore-password	-	A user-defined password of keystore.
security.ssl.rest.key-password	-	A user-defined password of the SSL key.
security.ssl.rest.truststore	${path}/flink.truststore	Path for storing the truststore.
security.ssl.rest.truststore-password	-	A user-defined password of truststore.

The path directory is a user-defined directory for storing configuration files of the SSL keystore and truststore.

Configure the paths for the client to access the keystore or truststore file.
- Relative path (recommended)
  Perform the following steps to set the file paths of flink.keystore and flink.truststore to relative paths and ensure that the directory where the Flink client command is executed can directly access the relative paths.
  1. In the conf/ directory of the Flink client, create a directory, for example, ssl.
    cd / Flink client directory/Flink/flink/conf/
    
    mkdir ssl
  2. Move the flink.keystore and flink.truststore files to the new paths.
    mv flink.keystore ssl/
    
    mv flink.truststore ssl/
  3. Change the values of the following parameters to relative paths in the flink-conf.yaml file:
    vi / Flink client directory/Flink/flink/conf/flink-conf.yaml
    security.ssl.keystore: ssl/flink.keystore security.ssl.truststore: ssl/flink.truststore
- Absolute path
  After the generate_keystore.sh script is executed, the flink.keystore and flink.truststore file paths are automatically set to absolute paths in the flink-conf.yaml file by default. In this case, you need to place the flink.keystore and flink.truststore files in the conf directory to the absolute paths of the Flink client and each Yarn node, respectively.