The Sentry Service

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, Impala, and Solr 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 service instead of a file allows you to use the more traditional GRANT/REVOKE statements to modify privileges.

The rest of this topic will walk you through the prerequisites for Sentry, basic terminology, and the Sentry privilege model.

Prerequisites
Terminology
Privilege Model
User to Group Mapping
Authorization Privilege Model for Hive and Impala
Authorization Privilege Model for Solr

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

Prerequisites

CDH 5.1.x (or higher) managed by Cloudera Manager 5.1.x (or higher). See the Cloudera Manager Administration Guide and installation.html#xd_583c10bfdbd326ba--5a52cca-1476e7473cd--7fdb for instructions.
HiveServer2 and the Hive Metastore running with strong authentication. For HiveServer2, strong authentication is either Kerberos or LDAP. For the Hive Metastore, only Kerberos is considered strong authentication (to override, see Securing the Hive Metastore).
Impala 1.4.0 (or higher) running with strong authentication. With Impala, either Kerberos or LDAP can be configured to achieve strong authentication.
Cloudera Search for CDH 5.1.0 or higher. Solr supports using Sentry beginning with CDH 5.1.0. Different functionality is added at different releases:
- Sentry with policy files is added in CDH 5.1.0.
- Sentry with config support is added in CDH 5.5.0.
- Sentry with database-backed Sentry service is added with CDH 5.8.0.
Implement Kerberos authentication on your cluster. For instructions, see Enabling Kerberos Authentication Using the Wizard.

Terminology

An object is an entity protected by Sentry's authorization rules. The objects supported in the current release are server, database, table, URI, collection, and config.
A role is a collection of rules for accessing a given object.
A privilege is granted to a role to govern access to an object. With CDH 5.5, Sentry allows you to assign the SELECT privilege to columns (only for Hive and Impala). Supported privileges are:

Valid privilege types and the objects they apply to

Privilege Object

ALL SERVER, TABLE, DB, URI, COLLECTION, CONFIG

INSERT DB, TABLE

SELECT DB, TABLE, COLUMN

Note: In Beeline, you can also grant SELECT and INSERT on SERVER.
A user is an entity that is permitted by the authentication subsystem to access the service. This entity can be a Kerberos principal, an LDAP userid, or an artifact of some other supported pluggable authentication system.
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.

Valid privilege types and the objects they apply to
Privilege	Object
ALL	SERVER, TABLE, DB, URI, COLLECTION, CONFIG
INSERT	DB, TABLE
SELECT	DB, TABLE, COLUMN

Privilege Model

Sentry uses a role-based privilege model with the following characteristics.

Allows any user to execute show function, desc function, and show locks.
Allows the user to see only those tables, databases, collections, configs 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.
Privileges granted on URIs are recursively applied to all subdirectories. That is, privileges only need to be granted on the parent directory.
CDH 5.5 introduces column-level access control for tables in Hive and Impala. Previously, Sentry supported privilege granularity only down to a table. Hence, if you wanted to restrict access to a column of sensitive data, the workaround would be to first create view for a subset of columns, and then grant privileges on that view. To reduce the administrative overhead associated with such an approach, Sentry now allows you to assign the SELECT privilege on a subset of columns in a table.

User to Group Mapping

Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)

You can configure Sentry to use Hadoop groups. By default, Sentry looks up groups locally, but it can be configured to look up Hadoop groups using LDAP (for Active Directory). User/group information for Sentry, Hive and Impala must be made available for lookup on the following hosts:

Sentry - Groups are looked up on the host the Sentry Server runs on.
Hive - Groups are looked up on the hosts running HiveServer2 and the Hive Metastore.
Impala - Groups are looked up on the Catalog Server and on all of the Impala daemon hosts.

Group mappings in Sentry can be summarized as in the figure below.

The Sentry service only uses HadoopUserGroup mappings. See Configuring LDAP Group Mappings for details on configuring LDAP group mappings in Hadoop.

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

Server
     URI
     Database
         Table
             Partition
             Columns
         View

Valid privilege types and objects they apply to
Privilege	Object
INSERT	DB, TABLE
SELECT	DB, TABLE, VIEW, COLUMN
ALL	SERVER, TABLE, DB, URI

Note that when you grant ALL on a URI, those permissions extend into the subdirectories in that path. For example, if a role has ALL on the following URI:

hdfs://host:port/directory_A/directory_B

That role will also have ALL on these directories:

hdfs://host:port/directory_A/directory_B/directory_C
hdfs://host:port/directory_A/directory_B/directory_C/directory_D
hdfs://host:port/directory_A/directory_B/directory_E

URI permissions do not affect HDFS ACL's.

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
COLUMN	SELECT	DATABASE	ALL
VIEW	SELECT	DATABASE	ALL

Privilege table for Hive & Impala operations
Operation	Scope	Privileges Required	URI
CREATE DATABASE	SERVER	ALL
DROP DATABASE	DATABASE	ALL
CREATE TABLE	DATABASE	ALL
DROP TABLE	TABLE	ALL
CREATE VIEW -This operation is allowed if you have column-level `SELECT` access to the columns being used.	DATABASE; SELECT on TABLE;	ALL
ALTER VIEW -This operation is allowed if you have column-level `SELECT` access to the columns being used.	VIEW/TABLE	ALL
DROP VIEW	VIEW/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 CREATE TABLE	TABLE	SELECT
SHOW PARTITIONS	TABLE	SELECT/INSERT
SHOW TABLES -Output includes all the tables for which the user has table-level privileges and all the tables for which the user has some column-level privileges.	TABLE	SELECT/INSERT
SHOW GRANT ROLE -Output includes an additional field for any column-level privileges.	TABLE	SELECT/INSERT
DESCRIBE TABLE -Output shows all columns if the user has table level-privileges or `SELECT` privilege on at least one table column	TABLE	SELECT/INSERT
LOAD DATA	TABLE	INSERT	URI
SELECT -You can grant the SELECT privilege on a view to give users access to specific columns of a table they do not otherwise have access to. -See Column-level Authorization for details on allowed column-level operations.	VIEW/TABLE; COLUMN	SELECT
INSERT OVERWRITE TABLE	TABLE	INSERT
CREATE TABLE .. AS SELECT -This operation is allowed if you have column-level `SELECT` access to the columns being used.	DATABASE; SELECT on TABLE	ALL
USE <dbName>	Any
CREATE FUNCTION	SERVER	ALL
ALTER TABLE .. SET SERDEPROPERTIES	TABLE	ALL
ALTER TABLE .. PARTITION SET SERDEPROPERTIES	TABLE	ALL

Privilege table for Hive-only operations
Operation	Scope	Privileges Required	URI
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
MSCK REPAIR TABLE	TABLE	ALL
ALTER DATABASE	DATABASE	ALL
DESCRIBE DATABASE	DATABASE	SELECT/INSERT
SHOW COLUMNS -Output for this operation filters columns to which the user does not have explicit `SELECT` access	TABLE	SELECT/INSERT
CREATE INDEX	TABLE	ALL
DROP INDEX	TABLE	ALL
SHOW INDEXES	TABLE	SELECT/INSERT
GRANT PRIVILEGE	Allowed only for Sentry admin users
REVOKE PRIVILEGE	Allowed only for Sentry admin users
SHOW GRANT	Allowed only for Sentry admin users
SHOW TBLPROPERTIES	TABLE	SELECT/INSERT
DESCRIBE TABLE .. PARTITION	TABLE	SELECT/INSERT
ADD ARCHIVE[S]	Not Allowed
ADD FILE[S]	Not Allowed
ADD JAR[S]	Not Allowed
DELETE JAR[S]	Not Allowed
DFS	Not Allowed
LIST JAR[S]	Not Allowed
SHOW CREATE VIEW	VIEW	SELECT

Privilege table for Impala-only operations
Operation	Scope	Privileges Required
EXPLAIN INSERT	TABLE; COLUMN	INSERT
EXPLAIN SELECT	TABLE; COLUMN	SELECT
INVALIDATE METADATA	SERVER	ALL
INVALIDATE METADATA <table name>	TABLE	SELECT/INSERT
REFRESH <table name> or REFRESH <table name> PARTITION (<partition_spec>)	TABLE	SELECT/INSERT
DROP FUNCTION	SERVER	ALL
COMPUTE STATS	TABLE	ALL
SHOW CREATE VIEW	VIEW / TABLE(S)	SELECT

Authorization Privilege Model for Solr

The tables below refer to the request handlers defined in the generated solrconfig.xml.secure. If you are not using this configuration file, the below may not apply.

admin is a special collection in Sentry used to represent administrative actions. A non-administrative request may only require privileges on the collection or config on which the request is being performed. This is called either collection1 or config1 in these tables. An administrative request may require privileges on both the admin collection and collection1. This is denoted as admin, collection1 in the tables below.

Privilege table for non-administrative request handlers
Request Handler	Required Collection Privilege	Collections that Require Privilege
`select`	`QUERY`	`collection1`
`query`	`QUERY`	`collection1`
`get`	`QUERY`	`collection1`
`browse`	`QUERY`	`collection1`
`tvrh`	`QUERY`	`collection1`
`clustering`	`QUERY`	`collection1`
`terms`	`QUERY`	`collection1`
`elevate`	`QUERY`	`collection1`
`analysis/field`	`QUERY`	`collection1`
`analysis/document`	`QUERY`	`collection1`
`update`	`UPDATE`	`collection1`
`update/json`	`UPDATE`	`collection1`
`update/csv`	`UPDATE`	`collection1`

Privilege table for collections admin actions
Collection Action	Required Collection Privilege	Collections that Require Privilege
`create`	`UPDATE`	`admin`, `collection1`
`delete`	`UPDATE`	`admin`, `collection1`
`reload`	`UPDATE`	`admin`, `collection1`
`createAlias`	`UPDATE`	`admin`, `collection1` Note: `collection1` here refers to the name of the alias, not the underlying collection(s). For example, `http://YOUR-HOST:8983/ solr/admin/collections?action= CREATEALIAS&name=collection1 &collections=underlyingCollection`
`deleteAlias`	`UPDATE`	`admin`, `collection1` Note: `collection1` here refers to the name of the alias, not the underlying collection(s). For example, `http://YOUR-HOST:8983/ solr/admin/collections?action= DELETEALIAS&name=collection1`
`syncShard`	`UPDATE`	`admin`, `collection1`
`splitShard`	`UPDATE`	`admin`, `collection1`
`deleteShard`	`UPDATE`	`admin`, `collection1`

Privilege table for core admin actions
Collection Action	Required Collection Privilege	Collections that Require Privilege
`create`	`UPDATE`	`admin`, `collection1`
`rename`	`UPDATE`	`admin`, `collection1`
`load`	`UPDATE`	`admin`, `collection1`
`unload`	`UPDATE`	`admin`, `collection1`
`status`	`UPDATE`	`admin`, `collection1`
`persist`	`UPDATE`	`admin`
`reload`	`UPDATE`	`admin`, `collection1`
`swap`	`UPDATE`	`admin`, `collection1`
`mergeIndexes`	`UPDATE`	`admin`, `collection1`
`split`	`UPDATE`	`admin`, `collection1`
`prepRecover`	`UPDATE`	`admin`, `collection1`
`requestRecover`	`UPDATE`	`admin`, `collection1`
`requestSyncShard`	`UPDATE`	`admin`, `collection1`
`requestApplyUpdates`	`UPDATE`	`admin`, `collection1`

Privilege table for Info and AdminHandlers
Request Handler	Required Collection Privilege	Collections that Require Privilege
`LukeRequestHandler`	`QUERY`	`admin`
`SystemInfoHandler`	`QUERY`	`admin`
`SolrInfoMBeanHandler`	`QUERY`	`admin`
`PluginInfoHandler`	`QUERY`	`admin`
`ThreadDumpHandler`	`QUERY`	`admin`
`PropertiesRequestHandler`	`QUERY`	`admin`
`LoginHandler`	`QUERY`, `UPDATE` (or `*`)	`admin`
`ShowFileRequestHandler`	`QUERY`	`admin`

Privilege table for Config Admin actions
Config Action	Required Collection Privilege	Collections that Require Privilege	Required Config Privilege	Configs that Require Privilege
`CREATE`	`UPDATE`	`admin`	`*`	`config1`
`DELETE`	`UPDATE`	`admin`	`*`	`config1`

Authorization With Apache Sentry

Installing and Upgrading the Sentry Service