Hive Default Authorization - Legacy Mode

This document describes Hive security using the basic authorization scheme, which regulates access to Hive metadata on the client side. 

Disclaimer

Hive authorization is not completely secure. The basic authorization scheme is intended primarily to prevent good users from accidentally doing bad things, but makes no promises about preventing malicious users from doing malicious things.  See the Hive authorization main page for the secure options.

Prerequisites

In order to use Hive authorization, there are two parameters that should be set in hive-site.xml:

<property>
  <name>hive.security.authorization.enabled</name>
  <value>true</value>
  <description>enable or disable the hive client authorization</description>
</property>

<property>
  <name>hive.security.authorization.createtable.owner.grants</name>
  <value>ALL</value>
  <description>the privileges automatically granted to the owner whenever a table gets created. 
   An example like "select,drop" will grant select and drop privilege to the owner of the table</description>
</property>

Note that, by default, the hive.security.authorization.createtable.owner.grants are set to null, which would result in the creator of a table having no access to the table.

Users, Groups, and Roles

At the core of Hive's authorization system are users, groups, and roles. Roles allow administrators to give a name to a set of grants which can be easily reused. A role may be assigned to users, groups, and other roles. For example, consider a system with the following users and groups:

• <User>: <Groups>
• user_all_dbs: group_db1, group_db2
• user_db1: group_db1
• user_db2: group_db2

If we wanted to restrict each user to a specific set of databases, we could use roles to build the authorization mechanism. The administrator would create two roles, called role_db1 and role_db2. The role_db1 role would provide privileges just for the first database, and the role_db2 role would provide privileges just for the second database. The administrator could then grant the role_db1 role to group_db1, or explicitly for the users in the group, and do the same for role_db2 with the users of the second database. In order to allow users who need to see all databases to get their appropriate privileges, a third role could be created called role_all_dbs, which would be granted role_db1 and role_db2. When user_all_dbs is granted the role_all_dbs role, the user implicitly is granted all the privileges of role_db1 and role_db2.

Hive roles must be created manually before being used, unlike users and groups. Users and groups are managed by the hive.security.authenticator.manager. When a user connects to a Metastore Server and issues a query, the Metastore will determine the username of the connecting user, and the groups associated with that ushive.security.authorization.ername. That information is then used to determine if the user should have access to the metadata being requested, by comparing the required privileges of the Hive operation to the user privileges using the following rules:

• User privileges (Has the privilege been granted to the user)
• Group privileges (Does the user belong to any groups that the privilege has been granted to)
• Role privileges (Does the user or any of the groups that the user belongs to have a role that grants the privilege)

By default, the Metastore uses the HadoopDefaultAuthenticator for determing user -> group mappings, which determines authorization by using the Unix usernames and groups on the machine where the Metastore is running. To make this more clear, consider a scenario where a user foo is a member of group bar on the machine running the Hive CLI, and connects to a Metastore running on a separate server that also has a user named foo, but on the Metastore Server, foo is a member of group baz. When an operation is executed, the Metastore will determine foo to be in the group baz.

Taking this a step further, it is also possible for the groups that a user belongs to on the Metastore Server may differ from the groups that the same user belongs to, as determined by HDFS. This could be the case if Hive or HDFS are configured to use non-default user -> group mappers, or the Metastore and the Namenode both use the defaults, but the processes are running on different machines, and the user -> group mappings are not the same on each machine.

It is important to realize that Hive Metastore only controls authorization for metadata, and the underlying data is controlled by HDFS, so if permissions and privileges between the two systems are not in sync, users may have access to metadata, but not the physical data. If the user -> group mappings across the Metastore and Namenode are not in sync, as in the scenarios above, a user may have the privileges required to access a table according to the Metastore, but may not have permission to access the underlying files according to the Namenode. This could also happen due to administrator intervention, if permissions on the files were changed by hand, but Metastore grants had not been updated.

Names of Users and Roles

Role names are case insensitive. That is, “marketing” and “MarkEting” refer to same role.

User names are case sensitive. This is because, unlike role names, user names are not managed within Hive.

Creating/Dropping/Using Roles

Create/Drop Role

CREATE ROLE role_name

DROP ROLE role_name

Grant/Revoke Roles

GRANT ROLE role_name [, role_name] ...
TO principal_specification [, principal_specification] ...
[WITH ADMIN OPTION]

REVOKE [ADMIN OPTION FOR] ROLE role_name [, role_name] ...
FROM principal_specification [, principal_specification] ...

principal_specification:
    USER user
  | GROUP group
  | ROLE role

Viewing Granted Roles

SHOW ROLE GRANT principal_specification
 
principal_specification:
    USER user
  | GROUP group
  | ROLE role

Privileges

The following privileges are supported in Hive:

• ALL - Gives users all privileges
• ALTER - Allows users to modify the metadata of an object
• UPDATE - Allows users to modify the physical data of an object
• CREATE - Allows users to create objects. For a database, this means users can create tables, and for a table, this means users can create partitions
• DROP - Allows users to drop objects
• INDEX - Allows users to create indexes on an object (Note: this is not currently implemented)
• LOCK - Allows users to lock or unlock tables when concurrency is enabled
• SELECT - Allows users to access data for objects
• SHOW_DATABASE - Allows users to view available databases

Grant/Revoke Privileges

GRANT
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    [ON object_specification]
    TO principal_specification [, principal_specification] ...
    [WITH GRANT OPTION]

REVOKE [GRANT OPTION FOR]
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    [ON object_specification]
    FROM principal_specification [, principal_specification] ...

REVOKE ALL PRIVILEGES, GRANT OPTION
    FROM user [, user] ...

priv_type:
    ALL | ALTER | UPDATE | CREATE | DROP
  | INDEX | LOCK | SELECT | SHOW_DATABASE 
 
object_specification:
    TABLE tbl_name
  | DATABASE db_name
 
principal_specification:
    USER user
  | GROUP group
  | ROLE role

Viewing Granted Privileges

SHOW GRANT principal_specification
[ON object_specification [(column_list)]]
 
principal_specification:
    USER user
  | GROUP group
  | ROLE role
 
object_specification:
    TABLE tbl_name
  | DATABASE db_name

Hive Operations and Required Privileges

As of the release of Hive 0.7, only these operations require permissions, according to org.apache.hadoop.hive.ql.plan.HiveOperation: