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 {:toc}
 
 # Spark Security: Things You Need To Know
 
 Security in Spark is OFF by default. This could mean you are vulnerable to attack by default.
 Spark supports multiple deployments types and each one supports different levels of security. Not
 all deployment types will be secure in all environments and none are secure by default. Be
 sure to evaluate your environment, what Spark supports, and take the appropriate measure to secure
 your Spark deployment.
 
 There are many different types of security concerns. Spark does not necessarily protect against
 all things. Listed below are some of the things Spark supports. Also check the deployment
 documentation for the type of deployment you are using for deployment specific settings. Anything
 not documented, Spark does not support.
 
 # Spark RPC (Communication protocol between Spark processes)
 
 ## Authentication
 
 Spark currently supports authentication for RPC channels using a shared secret. Authentication can
 be turned on by setting the `spark.authenticate` configuration parameter.
 
 The exact mechanism used to generate and distribute the shared secret is deployment-specific. Unless
 specified below, the secret must be defined by setting the `spark.authenticate.secret` config
 option. The same secret is shared by all Spark applications and daemons in that case, which limits
 the security of these deployments, especially on multi-tenant clusters.
 
 The REST Submission Server and the MesosClusterDispatcher do not support authentication.  You should
 ensure that all network access to the REST API & MesosClusterDispatcher (port 6066 and 7077
 respectively by default) are restricted to hosts that are trusted to submit jobs.
 
 ### YARN
 
 For Spark on [YARN](running-on-yarn.html), Spark will automatically handle generating and
 distributing the shared secret. Each application will use a unique shared secret. In
 the case of YARN, this feature relies on YARN RPC encryption being enabled for the distribution of
 secrets to be secure.
 
 ### Kubernetes
 
 On Kubernetes, Spark will also automatically generate an authentication secret unique to each
 application. The secret is propagated to executor pods using environment variables. This means
 that any user that can list pods in the namespace where the Spark application is running can
 also see their authentication secret. Access control rules should be properly set up by the
 Kubernetes admin to ensure that Spark authentication is secure.
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.authenticate</code></td>
   <td>false</td>
   <td>Whether Spark authenticates its internal connections.</td>
   <td>1.0.0</td>
 </tr>
 <tr>
   <td><code>spark.authenticate.secret</code></td>
   <td>None</td>
   <td>
     The secret key used authentication. See above for when this configuration should be set.
   </td>
   <td>1.0.0</td>
 </tr>
 </table>
 
 Alternatively, one can mount authentication secrets using files and Kubernetes secrets that
 the user mounts into their pods.
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.authenticate.secret.file</code></td>
   <td>None</td>
   <td>
     Path pointing to the secret key to use for securing connections. Ensure that the
     contents of the file have been securely generated. This file is loaded on both the driver
     and the executors unless other settings override this (see below).
   </td>
   <td>3.0.0</td>
 </tr>
 <tr>
   <td><code>spark.authenticate.secret.driver.file</code></td>
   <td>The value of <code>spark.authenticate.secret.file</code></td>
   <td>
     When specified, overrides the location that the Spark driver reads to load the secret.
     Useful when in client mode, when the location of the secret file may differ in the pod versus
     the node the driver is running in. When this is specified,
     <code>spark.authenticate.secret.executor.file</code> must be specified so that the driver
     and the executors can both use files to load the secret key. Ensure that the contents of the file
     on the driver is identical to the contents of the file on the executors.
   </td>
   <td>3.0.0</td>
 </tr>
 <tr>
   <td><code>spark.authenticate.secret.executor.file</code></td>
   <td>The value of <code>spark.authenticate.secret.file</code></td>
   <td>
     When specified, overrides the location that the Spark executors read to load the secret.
     Useful in client mode, when the location of the secret file may differ in the pod versus
     the node the driver is running in. When this is specified,
     <code>spark.authenticate.secret.driver.file</code> must be specified so that the driver
     and the executors can both use files to load the secret key. Ensure that the contents of the file
     on the driver is identical to the contents of the file on the executors.
   </td>
   <td>3.0.0</td>
 </tr>
 </table>
 
 Note that when using files, Spark will not mount these files into the containers for you. It is up
 you to ensure that the secret files are deployed securely into your containers and that the driver's
 secret file agrees with the executors' secret file.
 
 ## Encryption
 
 Spark supports AES-based encryption for RPC connections. For encryption to be enabled, RPC
 authentication must also be enabled and properly configured. AES encryption uses the
 [Apache Commons Crypto](https://commons.apache.org/proper/commons-crypto/) library, and Spark's
 configuration system allows access to that library's configuration for advanced users.
 
 There is also support for SASL-based encryption, although it should be considered deprecated. It
 is still required when talking to shuffle services from Spark versions older than 2.2.0.
 
 The following table describes the different options available for configuring this feature.
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.network.crypto.enabled</code></td>
   <td>false</td>
   <td>
     Enable AES-based RPC encryption, including the new authentication protocol added in 2.2.0.
   </td>
   <td>2.2.0</td>
 </tr>
 <tr>
   <td><code>spark.network.crypto.keyLength</code></td>
   <td>128</td>
   <td>
     The length in bits of the encryption key to generate. Valid values are 128, 192 and 256.
   </td>
   <td>2.2.0</td>
 </tr>
 <tr>
   <td><code>spark.network.crypto.keyFactoryAlgorithm</code></td>
   <td>PBKDF2WithHmacSHA1</td>
   <td>
     The key factory algorithm to use when generating encryption keys. Should be one of the
     algorithms supported by the javax.crypto.SecretKeyFactory class in the JRE being used.
   </td>
   <td>2.2.0</td>
 </tr>
 <tr>
   <td><code>spark.network.crypto.config.*</code></td>
   <td>None</td>
   <td>
     Configuration values for the commons-crypto library, such as which cipher implementations to
     use. The config name should be the name of commons-crypto configuration without the
     <code>commons.crypto</code> prefix.
   </td>
   <td>2.2.0</td>
 </tr>
 <tr>
   <td><code>spark.network.crypto.saslFallback</code></td>
   <td>true</td>
   <td>
     Whether to fall back to SASL authentication if authentication fails using Spark's internal
     mechanism. This is useful when the application is connecting to old shuffle services that
     do not support the internal Spark authentication protocol. On the shuffle service side,
     disabling this feature will block older clients from authenticating.
   </td>
   <td>2.2.0</td>
 </tr>
 <tr>
   <td><code>spark.authenticate.enableSaslEncryption</code></td>
   <td>false</td>
   <td>
     Enable SASL-based encrypted communication.
   </td>
   <td>2.2.0</td>
 </tr>
 <tr>
   <td><code>spark.network.sasl.serverAlwaysEncrypt</code></td>
   <td>false</td>
   <td>
     Disable unencrypted connections for ports using SASL authentication. This will deny connections
     from clients that have authentication enabled, but do not request SASL-based encryption.
   </td>
   <td>1.4.0</td>
 </tr>
 </table>
 
 
 # Local Storage Encryption
 
 Spark supports encrypting temporary data written to local disks. This covers shuffle files, shuffle
 spills and data blocks stored on disk (for both caching and broadcast variables). It does not cover
 encrypting output data generated by applications with APIs such as `saveAsHadoopFile` or
 `saveAsTable`. It also may not cover temporary files created explicitly by the user.
 
 The following settings cover enabling encryption for data written to disk:
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.io.encryption.enabled</code></td>
   <td>false</td>
   <td>
     Enable local disk I/O encryption. Currently supported by all modes except Mesos. It's strongly
     recommended that RPC encryption be enabled when using this feature.
   </td>
   <td>2.1.0</td>
 </tr>
 <tr>
   <td><code>spark.io.encryption.keySizeBits</code></td>
   <td>128</td>
   <td>
     IO encryption key size in bits. Supported values are 128, 192 and 256.
   </td>
   <td>2.1.0</td>
 </tr>
 <tr>
   <td><code>spark.io.encryption.keygen.algorithm</code></td>
   <td>HmacSHA1</td>
   <td>
     The algorithm to use when generating the IO encryption key. The supported algorithms are
     described in the KeyGenerator section of the Java Cryptography Architecture Standard Algorithm
     Name Documentation.
   </td>
   <td>2.1.0</td>
 </tr>
 <tr>
   <td><code>spark.io.encryption.commons.config.*</code></td>
   <td>None</td>
   <td>
     Configuration values for the commons-crypto library, such as which cipher implementations to
     use. The config name should be the name of commons-crypto configuration without the
     <code>commons.crypto</code> prefix.
   </td>
   <td>2.1.0</td>
 </tr>
 </table>
 
 
 # Web UI
 
 ## Authentication and Authorization
 
 Enabling authentication for the Web UIs is done using [javax servlet filters](https://docs.oracle.com/javaee/6/api/javax/servlet/Filter.html).
 You will need a filter that implements the authentication method you want to deploy. Spark does not
 provide any built-in authentication filters.
 
 Spark also supports access control to the UI when an authentication filter is present. Each
 application can be configured with its own separate access control lists (ACLs). Spark
 differentiates between "view" permissions (who is allowed to see the application's UI), and "modify"
 permissions (who can do things like kill jobs in a running application).
 
 ACLs can be configured for either users or groups. Configuration entries accept comma-separated
 lists as input, meaning multiple users or groups can be given the desired privileges. This can be
 used if you run on a shared cluster and have a set of administrators or developers who need to
 monitor applications they may not have started themselves. A wildcard (`*`) added to specific ACL
 means that all users will have the respective privilege. By default, only the user submitting the
 application is added to the ACLs.
 
 Group membership is established by using a configurable group mapping provider. The mapper is
 configured using the <code>spark.user.groups.mapping</code> config option, described in the table
 below.
 
 The following options control the authentication of Web UIs:
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.ui.filters</code></td>
   <td>None</td>
   <td>
     See the <a href="configuration.html#spark-ui">Spark UI</a> configuration for how to configure
     filters.
   </td>
   <td>1.0.0</td>
 </tr>
 <tr>
   <td><code>spark.acls.enable</code></td>
   <td>false</td>
   <td>
     Whether UI ACLs should be enabled. If enabled, this checks to see if the user has access
     permissions to view or modify the application. Note this requires the user to be authenticated,
     so if no authentication filter is installed, this option does not do anything.
   </td>
   <td>1.1.0</td>
 </tr>
 <tr>
   <td><code>spark.admin.acls</code></td>
   <td>None</td>
   <td>
     Comma-separated list of users that have view and modify access to the Spark application.
   </td>
   <td>1.1.0</td>
 </tr>
 <tr>
   <td><code>spark.admin.acls.groups</code></td>
   <td>None</td>
   <td>
     Comma-separated list of groups that have view and modify access to the Spark application.
   </td>
   <td>2.0.0</td>
 </tr>
 <tr>
   <td><code>spark.modify.acls</code></td>
   <td>None</td>
   <td>
     Comma-separated list of users that have modify access to the Spark application.
   </td>
   <td>1.1.0</td>
 </tr>
 <tr>
   <td><code>spark.modify.acls.groups</code></td>
   <td>None</td>
   <td>
     Comma-separated list of groups that have modify access to the Spark application.
   </td>
   <td>2.0.0</td>
 </tr>
 <tr>
   <td><code>spark.ui.view.acls</code></td>
   <td>None</td>
   <td>
     Comma-separated list of users that have view access to the Spark application.
   </td>
   <td>1.0.0</td>
 </tr>
 <tr>
   <td><code>spark.ui.view.acls.groups</code></td>
   <td>None</td>
   <td>
     Comma-separated list of groups that have view access to the Spark application.
   </td>
   <td>2.0.0</td>
 </tr>
 <tr>
   <td><code>spark.user.groups.mapping</code></td>
   <td><code>org.apache.spark.security.ShellBasedGroupsMappingProvider</code></td>
   <td>
     The list of groups for a user is determined by a group mapping service defined by the trait
     <code>org.apache.spark.security.GroupMappingServiceProvider</code>, which can be configured by
     this property.
 
     <br />By default, a Unix shell-based implementation is used, which collects this information
     from the host OS.
 
     <br /><em>Note:</em> This implementation supports only Unix/Linux-based environments.
     Windows environment is currently <b>not</b> supported. However, a new platform/protocol can
     be supported by implementing the trait mentioned above.
   </td>
   <td>2.0.0</td>
 </tr>
 </table>
 
 On YARN, the view and modify ACLs are provided to the YARN service when submitting applications, and
 control who has the respective privileges via YARN interfaces.
 
 ## Spark History Server ACLs
 
 Authentication for the SHS Web UI is enabled the same way as for regular applications, using
 servlet filters.
 
 To enable authorization in the SHS, a few extra options are used:
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.history.ui.acls.enable</code></td>
   <td>false</td>
   <td>
     Specifies whether ACLs should be checked to authorize users viewing the applications in
     the history server. If enabled, access control checks are performed regardless of what the
     individual applications had set for <code>spark.ui.acls.enable</code>. The application owner
     will always have authorization to view their own application and any users specified via
     <code>spark.ui.view.acls</code> and groups specified via <code>spark.ui.view.acls.groups</code>
     when the application was run will also have authorization to view that application.
     If disabled, no access control checks are made for any application UIs available through
     the history server.
   </td>
   <td>1.0.1</td>
 </tr>
 <tr>
   <td><code>spark.history.ui.admin.acls</code></td>
   <td>None</td>
   <td>
     Comma separated list of users that have view access to all the Spark applications in history
     server.
   </td>
   <td>2.1.1</td>
 </tr>
 <tr>
   <td><code>spark.history.ui.admin.acls.groups</code></td>
   <td>None</td>
   <td>
     Comma separated list of groups that have view access to all the Spark applications in history
     server.
   </td>
   <td>2.1.1</td>
 </tr>
 </table>
 
 The SHS uses the same options to configure the group mapping provider as regular applications.
 In this case, the group mapping provider will apply to all UIs server by the SHS, and individual
 application configurations will be ignored.
 
 ## SSL Configuration
 
 Configuration for SSL is organized hierarchically. The user can configure the default SSL settings
 which will be used for all the supported communication protocols unless they are overwritten by
 protocol-specific settings. This way the user can easily provide the common settings for all the
 protocols without disabling the ability to configure each one individually. The following table
 describes the SSL configuration namespaces:
 
 <table class="table">
   <tr>
     <th>Config Namespace</th>
     <th>Component</th>
   </tr>
   <tr>
     <td><code>spark.ssl</code></td>
     <td>
       The default SSL configuration. These values will apply to all namespaces below, unless
       explicitly overridden at the namespace level.
     </td>
   </tr>
   <tr>
     <td><code>spark.ssl.ui</code></td>
     <td>Spark application Web UI</td>
   </tr>
   <tr>
     <td><code>spark.ssl.standalone</code></td>
     <td>Standalone Master / Worker Web UI</td>
   </tr>
   <tr>
     <td><code>spark.ssl.historyServer</code></td>
     <td>History Server Web UI</td>
   </tr>
 </table>
 
 The full breakdown of available SSL options can be found below. The `${ns}` placeholder should be
 replaced with one of the above namespaces.
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th></tr>
   <tr>
     <td><code>${ns}.enabled</code></td>
     <td>false</td>
     <td>Enables SSL. When enabled, <code>${ns}.ssl.protocol</code> is required.</td>
   </tr>
   <tr>
     <td><code>${ns}.port</code></td>
     <td>None</td>
     <td>
       The port where the SSL service will listen on.
 
       <br />The port must be defined within a specific namespace configuration. The default
       namespace is ignored when reading this configuration.
 
       <br />When not set, the SSL port will be derived from the non-SSL port for the
       same service. A value of "0" will make the service bind to an ephemeral port.
     </td>
   </tr>
   <tr>
     <td><code>${ns}.enabledAlgorithms</code></td>
     <td>None</td>
     <td>
       A comma-separated list of ciphers. The specified ciphers must be supported by JVM.
 
       <br />The reference list of protocols can be found in the "JSSE Cipher Suite Names" section
       of the Java security guide. The list for Java 8 can be found at
       <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#ciphersuites">this</a>
       page.
 
       <br />Note: If not set, the default cipher suite for the JRE will be used.
     </td>
   </tr>
   <tr>
     <td><code>${ns}.keyPassword</code></td>
     <td>None</td>
     <td>
       The password to the private key in the key store.
     </td>
   </tr>
   <tr>
     <td><code>${ns}.keyStore</code></td>
     <td>None</td>
     <td>
       Path to the key store file. The path can be absolute or relative to the directory in which the
       process is started.
     </td>
   </tr>
   <tr>
     <td><code>${ns}.keyStorePassword</code></td>
     <td>None</td>
     <td>Password to the key store.</td>
   </tr>
   <tr>
     <td><code>${ns}.keyStoreType</code></td>
     <td>JKS</td>
     <td>The type of the key store.</td>
   </tr>
   <tr>
     <td><code>${ns}.protocol</code></td>
     <td>None</td>
     <td>
       TLS protocol to use. The protocol must be supported by JVM.
 
       <br />The reference list of protocols can be found in the "Additional JSSE Standard Names"
       section of the Java security guide. For Java 8, the list can be found at
       <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#jssenames">this</a>
       page.
     </td>
   </tr>
   <tr>
     <td><code>${ns}.needClientAuth</code></td>
     <td>false</td>
     <td>Whether to require client authentication.</td>
   </tr>
   <tr>
     <td><code>${ns}.trustStore</code></td>
     <td>None</td>
     <td>
       Path to the trust store file. The path can be absolute or relative to the directory in which
       the process is started.
     </td>
   </tr>
   <tr>
     <td><code>${ns}.trustStorePassword</code></td>
     <td>None</td>
     <td>Password for the trust store.</td>
   </tr>
   <tr>
     <td><code>${ns}.trustStoreType</code></td>
     <td>JKS</td>
     <td>The type of the trust store.</td>
   </tr>
 </table>
 
 Spark also supports retrieving `${ns}.keyPassword`, `${ns}.keyStorePassword` and `${ns}.trustStorePassword` from
 [Hadoop Credential Providers](https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/CredentialProviderAPI.html).
 User could store password into credential file and make it accessible by different components, like:
 
 ```
 hadoop credential create spark.ssl.keyPassword -value password \
     -provider jceks://hdfs@nn1.example.com:9001/user/backup/ssl.jceks
 ```
 
 To configure the location of the credential provider, set the `hadoop.security.credential.provider.path`
 config option in the Hadoop configuration used by Spark, like:
 
 ```
   <property>
     <name>hadoop.security.credential.provider.path</name>
     <value>jceks://hdfs@nn1.example.com:9001/user/backup/ssl.jceks</value>
   </property>
 ```
 
 Or via SparkConf "spark.hadoop.hadoop.security.credential.provider.path=jceks://hdfs@nn1.example.com:9001/user/backup/ssl.jceks".
 
 ## Preparing the key stores
 
 Key stores can be generated by `keytool` program. The reference documentation for this tool for
 Java 8 is [here](https://docs.oracle.com/javase/8/docs/technotes/tools/unix/keytool.html).
 The most basic steps to configure the key stores and the trust store for a Spark Standalone
 deployment mode is as follows:
 
 * Generate a key pair for each node
 * Export the public key of the key pair to a file on each node
 * Import all exported public keys into a single trust store
 * Distribute the trust store to the cluster nodes
 
 ### YARN mode
 
 To provide a local trust store or key store file to drivers running in cluster mode, they can be
 distributed with the application using the `--files` command line argument (or the equivalent
 `spark.files` configuration). The files will be placed on the driver's working directory, so the TLS
 configuration should just reference the file name with no absolute path.
 
 Distributing local key stores this way may require the files to be staged in HDFS (or other similar
 distributed file system used by the cluster), so it's recommended that the underlying file system be
 configured with security in mind (e.g. by enabling authentication and wire encryption).
 
 ### Standalone mode
 
 The user needs to provide key stores and configuration options for master and workers. They have to
 be set by attaching appropriate Java system properties in `SPARK_MASTER_OPTS` and in
 `SPARK_WORKER_OPTS` environment variables, or just in `SPARK_DAEMON_JAVA_OPTS`.
 
 The user may allow the executors to use the SSL settings inherited from the worker process. That
 can be accomplished by setting `spark.ssl.useNodeLocalConf` to `true`. In that case, the settings
 provided by the user on the client side are not used.
 
 ### Mesos mode
 
 Mesos 1.3.0 and newer supports `Secrets` primitives as both file-based and environment based
 secrets. Spark allows the specification of file-based and environment variable based secrets with
 `spark.mesos.driver.secret.filenames` and `spark.mesos.driver.secret.envkeys`, respectively.
 
 Depending on the secret store backend secrets can be passed by reference or by value with the
 `spark.mesos.driver.secret.names` and `spark.mesos.driver.secret.values` configuration properties,
 respectively.
 
 Reference type secrets are served by the secret store and referred to by name, for example
 `/mysecret`. Value type secrets are passed on the command line and translated into their
 appropriate files or environment variables.
 
 ## HTTP Security Headers
 
 Apache Spark can be configured to include HTTP headers to aid in preventing Cross Site Scripting
 (XSS), Cross-Frame Scripting (XFS), MIME-Sniffing, and also to enforce HTTP Strict Transport
 Security.
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.ui.xXssProtection</code></td>
   <td><code>1; mode=block</code></td>
   <td>
     Value for HTTP X-XSS-Protection response header. You can choose appropriate value
     from below:
     <ul>
       <li><code>0</code> (Disables XSS filtering)</li>
       <li><code>1</code> (Enables XSS filtering. If a cross-site scripting attack is detected,
         the browser will sanitize the page.)</li>
       <li><code>1; mode=block</code> (Enables XSS filtering. The browser will prevent rendering
         of the page if an attack is detected.)</li>
     </ul>
   </td>
   <td>2.3.0</td>
 </tr>
 <tr>
   <td><code>spark.ui.xContentTypeOptions.enabled</code></td>
   <td><code>true</code></td>
   <td>
     When enabled, X-Content-Type-Options HTTP response header will be set to "nosniff".
   </td>
   <td>2.3.0</td>
 </tr>
 <tr>
   <td><code>spark.ui.strictTransportSecurity</code></td>
   <td>None</td>
   <td>
     Value for HTTP Strict Transport Security (HSTS) Response Header. You can choose appropriate
     value from below and set <code>expire-time</code> accordingly. This option is only used when
     SSL/TLS is enabled.
     <ul>
       <li><code>max-age=&lt;expire-time&gt;</code></li>
       <li><code>max-age=&lt;expire-time&gt;; includeSubDomains</code></li>
       <li><code>max-age=&lt;expire-time&gt;; preload</code></li>
     </ul>
   </td>
   <td>2.3.0</td>
 </tr>
 </table>
 
 
 # Configuring Ports for Network Security
 
 Generally speaking, a Spark cluster and its services are not deployed on the public internet.
 They are generally private services, and should only be accessible within the network of the
 organization that deploys Spark. Access to the hosts and ports used by Spark services should
 be limited to origin hosts that need to access the services.
 
 Below are the primary ports that Spark uses for its communication and how to
 configure those ports.
 
 ## Standalone mode only
 
 <table class="table">
   <tr>
     <th>From</th><th>To</th><th>Default Port</th><th>Purpose</th><th>Configuration
     Setting</th><th>Notes</th>
   </tr>
   <tr>
     <td>Browser</td>
     <td>Standalone Master</td>
     <td>8080</td>
     <td>Web UI</td>
     <td><code>spark.master.ui.port /<br> SPARK_MASTER_WEBUI_PORT</code></td>
     <td>Jetty-based. Standalone mode only.</td>
   </tr>
   <tr>
     <td>Browser</td>
     <td>Standalone Worker</td>
     <td>8081</td>
     <td>Web UI</td>
     <td><code>spark.worker.ui.port /<br> SPARK_WORKER_WEBUI_PORT</code></td>
     <td>Jetty-based. Standalone mode only.</td>
   </tr>
   <tr>
     <td>Driver /<br> Standalone Worker</td>
     <td>Standalone Master</td>
     <td>7077</td>
     <td>Submit job to cluster /<br> Join cluster</td>
     <td><code>SPARK_MASTER_PORT</code></td>
     <td>Set to "0" to choose a port randomly. Standalone mode only.</td>
   </tr>
   <tr>
     <td>External Service</td>
     <td>Standalone Master</td>
     <td>6066</td>
     <td>Submit job to cluster via REST API</td>
     <td><code>spark.master.rest.port</code></td>
     <td>Use <code>spark.master.rest.enabled</code> to enable/disable this service. Standalone mode only.</td>
   </tr>
   <tr>
     <td>Standalone Master</td>
     <td>Standalone Worker</td>
     <td>(random)</td>
     <td>Schedule executors</td>
     <td><code>SPARK_WORKER_PORT</code></td>
     <td>Set to "0" to choose a port randomly. Standalone mode only.</td>
   </tr>
 </table>
 
 ## All cluster managers
 
 <table class="table">
   <tr>
     <th>From</th><th>To</th><th>Default Port</th><th>Purpose</th><th>Configuration
     Setting</th><th>Notes</th>
   </tr>
   <tr>
     <td>Browser</td>
     <td>Application</td>
     <td>4040</td>
     <td>Web UI</td>
     <td><code>spark.ui.port</code></td>
     <td>Jetty-based</td>
   </tr>
   <tr>
     <td>Browser</td>
     <td>History Server</td>
     <td>18080</td>
     <td>Web UI</td>
     <td><code>spark.history.ui.port</code></td>
     <td>Jetty-based</td>
   </tr>
   <tr>
     <td>Executor /<br> Standalone Master</td>
     <td>Driver</td>
     <td>(random)</td>
     <td>Connect to application /<br> Notify executor state changes</td>
     <td><code>spark.driver.port</code></td>
     <td>Set to "0" to choose a port randomly.</td>
   </tr>
   <tr>
     <td>Executor / Driver</td>
     <td>Executor / Driver</td>
     <td>(random)</td>
     <td>Block Manager port</td>
     <td><code>spark.blockManager.port</code></td>
     <td>Raw socket via ServerSocketChannel</td>
   </tr>
 </table>
 
 
 # Kerberos
 
 Spark supports submitting applications in environments that use Kerberos for authentication.
 In most cases, Spark relies on the credentials of the current logged in user when authenticating
 to Kerberos-aware services. Such credentials can be obtained by logging in to the configured KDC
 with tools like `kinit`.
 
 When talking to Hadoop-based services, Spark needs to obtain delegation tokens so that non-local
 processes can authenticate. Spark ships with support for HDFS and other Hadoop file systems, Hive
 and HBase.
 
 When using a Hadoop filesystem (such HDFS or WebHDFS), Spark will acquire the relevant tokens
 for the service hosting the user's home directory.
 
 An HBase token will be obtained if HBase is in the application's classpath, and the HBase
 configuration has Kerberos authentication turned (`hbase.security.authentication=kerberos`).
 
 Similarly, a Hive token will be obtained if Hive is in the classpath, and the configuration includes
 URIs for remote metastore services (`hive.metastore.uris` is not empty).
 
 If an application needs to interact with other secure Hadoop filesystems, their URIs need to be
 explicitly provided to Spark at launch time. This is done by listing them in the
 `spark.kerberos.access.hadoopFileSystems` property, described in the configuration section below.
 
 Spark also supports custom delegation token providers using the Java Services
 mechanism (see `java.util.ServiceLoader`). Implementations of
 `org.apache.spark.security.HadoopDelegationTokenProvider` can be made available to Spark
 by listing their names in the corresponding file in the jar's `META-INF/services` directory.
 
 Delegation token support is currently only supported in YARN and Mesos modes. Consult the
 deployment-specific page for more information.
 
 The following options provides finer-grained control for this feature:
 
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th><th>Since Version</th></tr>
 <tr>
   <td><code>spark.security.credentials.${service}.enabled</code></td>
   <td><code>true</code></td>
   <td>
     Controls whether to obtain credentials for services when security is enabled.
     By default, credentials for all supported services are retrieved when those services are
     configured, but it's possible to disable that behavior if it somehow conflicts with the
     application being run.
   </td>
   <td>2.3.0</td>
 </tr>
 <tr>
   <td><code>spark.kerberos.access.hadoopFileSystems</code></td>
   <td>(none)</td>
   <td>
     A comma-separated list of secure Hadoop filesystems your Spark application is going to access. For
     example, <code>spark.kerberos.access.hadoopFileSystems=hdfs://nn1.com:8032,hdfs://nn2.com:8032,
     webhdfs://nn3.com:50070</code>. The Spark application must have access to the filesystems listed
     and Kerberos must be properly configured to be able to access them (either in the same realm
     or in a trusted realm). Spark acquires security tokens for each of the filesystems so that
     the Spark application can access those remote Hadoop filesystems.
   </td>
   <td>3.0.0</td>
 </tr>
 </table>
 
 ## Long-Running Applications
 
 Long-running applications may run into issues if their run time exceeds the maximum delegation
 token lifetime configured in services it needs to access.
 
 This feature is not available everywhere. In particular, it's only implemented
 on YARN and Kubernetes (both client and cluster modes), and on Mesos when using client mode.
 
 Spark supports automatically creating new tokens for these applications. There are two ways to
 enable this functionality.
 
 ### Using a Keytab
 
 By providing Spark with a principal and keytab (e.g. using `spark-submit` with `--principal`
 and `--keytab` parameters), the application will maintain a valid Kerberos login that can be
 used to retrieve delegation tokens indefinitely.
 
 Note that when using a keytab in cluster mode, it will be copied over to the machine running the
 Spark driver. In the case of YARN, this means using HDFS as a staging area for the keytab, so it's
 strongly recommended that both YARN and HDFS be secured with encryption, at least.
 
 ### Using a ticket cache
 
 By setting `spark.kerberos.renewal.credentials` to `ccache` in Spark's configuration, the local
 Kerberos ticket cache will be used for authentication. Spark will keep the ticket renewed during its
 renewable life, but after it expires a new ticket needs to be acquired (e.g. by running `kinit`).
 
 It's up to the user to maintain an updated ticket cache that Spark can use.
 
 The location of the ticket cache can be customized by setting the `KRB5CCNAME` environment
 variable.
 
 ## Secure Interaction with Kubernetes
 
 When talking to Hadoop-based services behind Kerberos, it was noted that Spark needs to obtain delegation tokens
 so that non-local processes can authenticate. These delegation tokens in Kubernetes are stored in Secrets that are
 shared by the Driver and its Executors. As such, there are three ways of submitting a Kerberos job:
 
 In all cases you must define the environment variable: `HADOOP_CONF_DIR` or
 `spark.kubernetes.hadoop.configMapName.`
 
 It also important to note that the KDC needs to be visible from inside the containers.
 
 If a user wishes to use a remote HADOOP_CONF directory, that contains the Hadoop configuration files, this could be
 achieved by setting `spark.kubernetes.hadoop.configMapName` to a pre-existing ConfigMap.
 
 1. Submitting with a $kinit that stores a TGT in the Local Ticket Cache:
 ```bash
 /usr/bin/kinit -kt <keytab_file> <username>/<krb5 realm>
 /opt/spark/bin/spark-submit \
     --deploy-mode cluster \
     --class org.apache.spark.examples.HdfsTest \
     --master k8s://<KUBERNETES_MASTER_ENDPOINT> \
     --conf spark.executor.instances=1 \
     --conf spark.app.name=spark-hdfs \
     --conf spark.kubernetes.container.image=spark:latest \
     --conf spark.kubernetes.kerberos.krb5.path=/etc/krb5.conf \
     local:///opt/spark/examples/jars/spark-examples_<VERSION>.jar \
     <HDFS_FILE_LOCATION>
 ```
 2. Submitting with a local Keytab and Principal
 ```bash
 /opt/spark/bin/spark-submit \
     --deploy-mode cluster \
     --class org.apache.spark.examples.HdfsTest \
     --master k8s://<KUBERNETES_MASTER_ENDPOINT> \
     --conf spark.executor.instances=1 \
     --conf spark.app.name=spark-hdfs \
     --conf spark.kubernetes.container.image=spark:latest \
     --conf spark.kerberos.keytab=<KEYTAB_FILE> \
     --conf spark.kerberos.principal=<PRINCIPAL> \
     --conf spark.kubernetes.kerberos.krb5.path=/etc/krb5.conf \
     local:///opt/spark/examples/jars/spark-examples_<VERSION>.jar \
     <HDFS_FILE_LOCATION>
 ```
 
 3. Submitting with pre-populated secrets, that contain the Delegation Token, already existing within the namespace
 ```bash
 /opt/spark/bin/spark-submit \
     --deploy-mode cluster \
     --class org.apache.spark.examples.HdfsTest \
     --master k8s://<KUBERNETES_MASTER_ENDPOINT> \
     --conf spark.executor.instances=1 \
     --conf spark.app.name=spark-hdfs \
     --conf spark.kubernetes.container.image=spark:latest \
     --conf spark.kubernetes.kerberos.tokenSecret.name=<SECRET_TOKEN_NAME> \
     --conf spark.kubernetes.kerberos.tokenSecret.itemKey=<SECRET_ITEM_KEY> \
     --conf spark.kubernetes.kerberos.krb5.path=/etc/krb5.conf \
     local:///opt/spark/examples/jars/spark-examples_<VERSION>.jar \
     <HDFS_FILE_LOCATION>
 ```
 
 3b. Submitting like in (3) however specifying a pre-created krb5 ConfigMap and pre-created `HADOOP_CONF_DIR` ConfigMap
 ```bash
 /opt/spark/bin/spark-submit \
     --deploy-mode cluster \
     --class org.apache.spark.examples.HdfsTest \
     --master k8s://<KUBERNETES_MASTER_ENDPOINT> \
     --conf spark.executor.instances=1 \
     --conf spark.app.name=spark-hdfs \
     --conf spark.kubernetes.container.image=spark:latest \
     --conf spark.kubernetes.kerberos.tokenSecret.name=<SECRET_TOKEN_NAME> \
     --conf spark.kubernetes.kerberos.tokenSecret.itemKey=<SECRET_ITEM_KEY> \
     --conf spark.kubernetes.hadoop.configMapName=<HCONF_CONFIG_MAP_NAME> \
     --conf spark.kubernetes.kerberos.krb5.configMapName=<KRB_CONFIG_MAP_NAME> \
     local:///opt/spark/examples/jars/spark-examples_<VERSION>.jar \
     <HDFS_FILE_LOCATION>
 ```
 # Event Logging
 
 If your applications are using event logging, the directory where the event logs go
 (`spark.eventLog.dir`) should be manually created with proper permissions. To secure the log files,
 the directory permissions should be set to `drwxrwxrwxt`. The owner and group of the directory
 should correspond to the super user who is running the Spark History Server.
 
 This will allow all users to write to the directory but will prevent unprivileged users from
 reading, removing or renaming a file unless they own it. The event log files will be created by
 Spark with permissions such that only the user and group have read and write access.
 
 # Persisting driver logs in client mode
 
 If your applications persist driver logs in client mode by enabling `spark.driver.log.persistToDfs.enabled`,
 the directory where the driver logs go (`spark.driver.log.dfsDir`) should be manually created with proper
 permissions. To secure the log files, the directory permissions should be set to `drwxrwxrwxt`. The owner
 and group of the directory should correspond to the super user who is running the Spark History Server.
 
 This will allow all users to write to the directory but will prevent unprivileged users from
 reading, removing or renaming a file unless they own it. The driver log files will be created by
 Spark with permissions such that only the user and group have read and write access.

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