This is the documentation for Cloudera 5.2.x.
Documentation for other versions is available at Cloudera Documentation.

The Sentry Service

  Important: This is the documentation for the Sentry service introduced in CDH 5.1. If you want to use Sentry's previous policy file approach to secure your data, see Sentry Policy File Authorization.

The Sentry service is a RPC server that stores the authorization metadata in an underlying relational database and provides RPC interfaces to retrieve and manipulate privileges. It supports secure access to services using Kerberos. The service serves authorization metadata from the database backed storage; it does not handle actual privilege validation. The Hive and Impala services are clients of this service and will enforce Sentry privileges when configured to use Sentry.

The motivation behind introducing a new Sentry service is to make it easier to handle user privileges than the existing policy file approach. Providing a database instead, allows you to use the more traditional GRANT/REVOKE statements to modify privileges.

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For more information on installing, upgrading and configuring the Sentry service, see:

Prerequisites

Privilege Model

With CDH 5.1, the privilege model has undergone changes to accommodate the new grant/revoke syntax that is used with the Sentry service. These changes are common to both the new database-backed Sentry service, as well as the previous policy file approach.

The Sentry privilege model has the following characteristics:
  • Allows any user to execute show function, desc function, and show locks.
  • Allows the user to see only those tables and databases for which this user has privileges.
  • Requires a user to have the necessary privileges on the URI to execute HiveQL operations that take in a location. Examples of such operations include LOAD, IMPORT, and EXPORT.
  Important: When Sentry is enabled, a user with no privileges on a database will not be allowed to connect to HiveServer2. This is because the use <database> command is now executed as part of the connection to HiveServer2, which is why the connection fails. See HIVE-4256.

For more information, see Appendix: Authorization Privilege Model for Hive and Impala.

Users and Groups

  • A user is an entity that is permitted by the authentication subsystem to access the Hive service. This entity can be a Kerberos principal, an LDAP userid, or an artifact of some other pluggable authentication system supported by HiveServer2.
  • A group connects the authentication system with the authorization system. It is a collection of one or more users who have been granted one or more authorization roles. Sentry allows a set of roles to be configured for a group.
  • A configured group provider determines a user’s affiliation with a group. The current release supports HDFS-backed groups and locally configured groups.
For example,
analyst = sales_reporting, data_export, audit_report
Here the group analyst is granted the roles sales_reporting, data_export, and audit_report. The members of this group can run the HiveQL statements that are allowed by these roles. If this is an HDFS-backed group, then all the users belonging to the HDFS group analyst can run such queries.

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User to Group Mapping

You can configure Sentry to use either Hadoop groups or groups defined in the policy file. By default, Sentry looks up groups locally, but it can be configured to look up Hadoop groups using LDAP (for Active Directory). Local groups will be looked up on the host Sentry runs on. For Hive, this will be the host running HiveServer2. Group mappings in Sentry can be summarized as in the figure below:

  Important: You can use either Hadoop groups or local groups, but not both at the same time. Use local groups if you want to do a quick proof-of-concept. For production, use Hadoop groups. Refer Configuring LDAP Group Mappings for details on configuring LDAP group mappings in Hadoop.

Configuring User to Group Mappings

Required Role:

Hadoop Groups

  1. Go to the Hive service.
  2. Click the Configuration tab.
  3. Under the Service-Wide category, go to the Sentry section.
  4. Set the Sentry User to Group Mapping Class property to org.apache.sentry.provider.file.HadoopGroupResourceAuthorizationProvider.
  5. Click Save Changes.
  6. Restart the Hive service.

Local Groups

  1. Define local groups in the [users] section of the Policy File. For example:
    [users]
    user1 = group1, group2, group3
    user2 = group2, group3
  2. Modify Sentry configuration as follows:
    1. Go to the Hive service.
    2. Click the Configuration tab.
    3. Under the Service-Wide category, go to the Sentry section.
    4. Set the Sentry User to Group Mapping Class property to org.apache.sentry.provider.file.LocalGroupResourceAuthorizationProvider.
    5. Click Save Changes.
    6. Restart the Hive service.

Appendix: Authorization Privilege Model for Hive and Impala

Privileges can be granted on different objects in the Hive warehouse. Any privilege that can be granted is associated with a level in the object hierarchy. If a privilege is granted on a container object in the hierarchy, the base object automatically inherits it. For instance, if a user has ALL privileges on the database scope, then (s)he has ALL privileges on all of the base objects contained within that scope.

Object Hierarchy in Hive

Server
     Database
         Table
             Partition
             Columns
         View
         Index
     Function/Routine
     Lock
Table 1. Valid privilege types and objects they apply to
Privilege Object
INSERT DB, TABLE
SELECT DB, TABLE
ALL SERVER, TABLE, DB, URI
Table 2. Privilege hierarchy
Base Object Granular privileges on object Container object that contains the base object Privileges on container object that implies privileges on the base object
DATABASE ALL SERVER ALL
TABLE INSERT DATABASE ALL
TABLE SELECT DATABASE ALL
VIEW SELECT DATABASE ALL
Table 3. Privilege table for Hive & Impala operations
Operation Scope Privileges URI Others
CREATE DATABASE SERVER ALL    
DROP DATABASE DATABASE ALL
CREATE TABLE DATABASE ALL
DROP TABLE TABLE ALL
CREATE VIEW DATABASE; SELECT on TABLE ALL SELECT on TABLE
DROP VIEW VIEW/TABLE ALL
CREATE INDEX TABLE ALL
DROP INDEX TABLE ALL
ALTER TABLE .. ADD COLUMNS TABLE ALL
ALTER TABLE .. REPLACE COLUMNS TABLE ALL
ALTER TABLE .. CHANGE column TABLE ALL
ALTER TABLE .. RENAME TABLE ALL
ALTER TABLE .. SET TBLPROPERTIES TABLE ALL
ALTER TABLE .. SET FILEFORMAT TABLE ALL
ALTER TABLE .. SET LOCATION TABLE ALL URI  
ALTER TABLE .. ADD PARTITION TABLE ALL
ALTER TABLE .. ADD PARTITION location TABLE ALL URI  
ALTER TABLE .. DROP PARTITION TABLE ALL
ALTER TABLE .. PARTITION SET FILEFORMAT TABLE ALL
SHOW TBLPROPERTIES TABLE SELECT/INSERT    
SHOW CREATE TABLE TABLE SELECT/INSERT    
SHOW PARTITIONs TABLE SELECT/INSERT    
DESCRIBE TABLE TABLE SELECT/INSERT    
DESCRIBE TABLE .. PARTITION TABLE SELECT/INSERT    
LOAD DATA TABLE INSERT URI  
SELECT TABLE SELECT    
INSERT OVERWRITE TABLE TABLE INSERT    
CREATE TABLE .. AS SELECT DATABASE; SELECT on TABLE ALL SELECT on TABLE
USE <dbName> Any
ALTER TABLE .. SET SERDEPROPERTIES TABLE ALL
ALTER TABLE .. PARTITION SET SERDEPROPERTIES TABLE ALL
Hive-Only Operations
INSERT OVERWRITE DIRECTORY TABLE INSERT URI  
Analyze TABLE TABLE SELECT + INSERT    
IMPORT TABLE DATABASE ALL URI  
EXPORT TABLE TABLE SELECT URI  
ALTER TABLE TOUCH TABLE ALL
ALTER TABLE TOUCH PARTITION TABLE ALL
ALTER TABLE .. CLUSTERED BY SORTED BY TABLE ALL
ALTER TABLE .. ENABLE/DISABLE TABLE ALL
ALTER TABLE .. PARTITION ENABLE/DISABLE TABLE ALL
ALTER TABLE .. PARTITION.. RENAME TO PARTITION TABLE ALL    
ALTER DATABASE DATABASE ALL    
DESCRIBE DATABASE DATABASE SELECT/INSERT    
SHOW COLUMNS TABLE SELECT/INSERT    
SHOW INDEXES TABLE SELECT/INSERT    
GRANT PRIVILEGE Allowed only for Sentry admin users
REVOKE PRIVILEGE Allowed only for Sentry admin users
SHOW GRANTS Allowed only for Sentry admin users
ADD JAR Not Allowed      
ADD FILE Not Allowed      
DFS Not Allowed      
Impala-Only Operations
EXPLAIN TABLE SELECT    
INVALIDATE METADATA SERVER ALL    
INVALIDATE METADATA <table name> TABLE SELECT/INSERT    
REFRESH <table name> TABLE SELECT/INSERT    
CREATE FUNCTION SERVER ALL    
DROP FUNCTION SERVER ALL    
COMPUTE STATS TABLE ALL