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 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.
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.
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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 Cloudera Installation Guide 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.
- Implement Kerberos authentication on your cluster. For instructions, see Enabling Kerberos Authentication Using the Wizard.
Terminologies
- An object is an entity protected by Sentry's authorization rules. The objects supported in the current release are server, database, table, and URI.
- A role is a collection of rules for accessing a given Hive 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 - 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.
Privilege Model
- 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.
- 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.
For more information, see Appendix: Authorization Privilege Model for Hive and Impala.
User to Group Mapping
Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)
Group mappings in Sentry can be summarized as in the figure below.
![](../images/groupmappings.png)
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 URI Database Table Partition Columns View Index Function/Routine Lock
Privilege | Object |
---|---|
INSERT | DB, TABLE |
SELECT | DB, TABLE, COLUMN |
ALL | SERVER, TABLE, DB, URI |
- hdfs://host:port/directory_A/directory_B
- 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
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 |
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 on DATABASE | |
ALTER TABLE .. PARTITION SET SERDEPROPERTIES | TABLE | ALL on DATABASE | |
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 on DATABASE | |
ALTER TABLE TOUCH PARTITION | TABLE | ALL on DATABASE | |
ALTER TABLE .. CLUSTERED BY SORTED BY | TABLE | ALL on DATABASE | |
ALTER TABLE .. ENABLE/DISABLE | TABLE | ALL on DATABASE | |
ALTER TABLE .. PARTITION ENABLE/DISABLE | TABLE | ALL on DATABASE | |
ALTER TABLE .. PARTITION.. RENAME TO PARTITION | TABLE | ALL on DATABASE | |
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 | |
Impala-Only Operations | |||
EXPLAIN SELECT | TABLE; COLUMN | SELECT | |
EXPLAIN INSERT | TABLE; COLUMN | INSERT | |
INVALIDATE METADATA | SERVER | ALL | |
INVALIDATE METADATA <table name> | TABLE | SELECT/INSERT | |
REFRESH <table name> | TABLE | SELECT/INSERT | |
DROP FUNCTION | SERVER | ALL | |
COMPUTE STATS | TABLE | ALL | |
SHOW CREATE VIEW | VIEW / TABLE(S) | SELECT |