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# Service Level Authorization Guide

- Purpose
- Prerequisites
- Overview
- Configuration
  - Enable Service Level Authorization
  - Hadoop Services and Configuration Properties
  - Access Control Lists
  - Refreshing Service Level Authorization Configuration
  - Examples

## Purpose

This document describes how to configure and manage Service Level Authorization for Hadoop.

## Prerequisites

Make sure Hadoop is installed, configured and setup correctly. For more information see:

- Single Node Setup for first-time users.
- Cluster Setup for large, distributed clusters.

## Overview

Service Level Authorization is the initial authorization mechanism to ensure clients connecting to a particular Hadoop service have the necessary, pre-configured, permissions and are authorized to access the given service. For example, a MapReduce cluster can use this mechanism to allow a configured list of users/groups to submit jobs.

The ${HADOOP_CONF_DIR}/hadoop-policy.xml configuration file is used to define the access control lists for various Hadoop services.

Service Level Authorization is performed much before to other access control checks such as file-permission checks, access control on job queues etc.

## Configuration

This section describes how to configure service-level authorization via the configuration file {HADOOP_CONF_DIR}/hadoop-policy.xml.

### Enable Service Level Authorization

By default, service-level authorization is disabled for Hadoop. To enable it set the configuration property hadoop.security.authorization to true in ${HADOOP_CONF_DIR}/core-site.xml.

### Hadoop Services and Configuration Properties

This section lists the various Hadoop services and their configuration knobs:

Property | Service
--- | ---
security.client.protocol.acl | ACL for ClientProtocol, which is used by user code via the DistributedFileSystem.
security.client.datanode.protocol.acl | ACL for ClientDatanodeProtocol, the client-to-datanode protocol for block recovery.
security.datanode.protocol.acl | ACL for DatanodeProtocol, which is used by datanodes to communicate with the namenode.
security.inter.datanode.protocol.acl | ACL for InterDatanodeProtocol, the inter-datanode protocol for updating generation timestamp.
security.namenode.protocol.acl | ACL for NamenodeProtocol, the protocol used by the secondary namenode to communicate with the namenode.
security.inter.tracker.protocol.acl | ACL for InterTrackerProtocol, used by the tasktrackers to communicate with the jobtracker.
security.job.submission.protocol.acl | ACL for JobSubmissionProtocol, used by job clients to communciate with the jobtracker for job submission, querying job status etc.
security.task.umbilical.protocol.acl | ACL for TaskUmbilicalProtocol, used by the map and reduce tasks to communicate with the parent tasktracker.
security.refresh.policy.protocol.acl | ACL for RefreshAuthorizationPolicyProtocol, used by the dfsadmin and mradmin commands to refresh the security policy in-effect.

### Access Control Lists

${HADOOP_CONF_DIR}/hadoop-policy.xml defines an access control list for each Hadoop service. Every access control list has a simple format:

The list of users and groups are both comma separated list of names. The two lists are separated by a space.

Example: user1,user2 group1,group2.

Add a blank at the beginning of the line if only a list of groups is to be provided, equivalently a comman-separated list of users followed by a space or nothing implies only a set of given users.

A special value of * implies that all users are allowed to access the service.

### Refreshing Service Level Authorization Configuration

The service-level authorization configuration for the NameNode and JobTracker can be changed without restarting either of the Hadoop master daemons. The cluster administrator can change ${HADOOP_CONF_DIR}/hadoop-policy.xml on the master nodes and instruct the NameNode and JobTracker to reload their respective configurations via the -refreshServiceAcl switch to dfsadmin and mradmin commands respectively.

Refresh the service-level authorization configuration for the NameNode:

$ bin/hadoop dfsadmin -refreshServiceAcl

Refresh the service-level authorization configuration for the JobTracker:

$ bin/hadoop mradmin -refreshServiceAcl

Of course, one can use the security.refresh.policy.protocol.acl property in ${HADOOP_CONF_DIR}/hadoop-policy.xml to restrict access to the ability to refresh the service-level authorization configuration to certain users/groups.

### Examples

Allow only users alice, bob and users in the mapreduce group to submit jobs to the MapReduce cluster:

    <property>
         <name>security.job.submission.protocol.acl</name>
         <value>alice,bob mapreduce</value>
    </property>

Allow only DataNodes running as the users who belong to the group datanodes to communicate with the NameNode:

    <property>
         <name>security.datanode.protocol.acl</name>
         <value>datanodes</value>
    </property>

Allow any user to talk to the HDFS cluster as a DFSClient:

    <property>
         <name>security.client.protocol.acl</name>
         <value>*</value>
    </property>