Apache Ranger

Apache Ranger models tabular objects are stored in a Kudu cluster in the following hierarchy: Database, Table, Column.

Database: Kudu does not have the concept of a database. Therefore, a database is indicated as a prefix of table names with the format <database>.<table>. Since Kudu's only restriction on table names is that they be valid UTF-8 encoded strings, Kudu considers special characters to be valid parts of database or table names. For example, if a managed Kudu table created from Impala is named impala::bar.foo, its database will be impala::bar.

Table: Is a single Kudu table.

Column: Is a column within a Kudu table.

In Ranger, privileges are also associated with specific actions. Access to Kudu tables may rely on privileges on the following actions:
  • DROP
There are two additional access types:
  • ALL

If a user has the ALL privilege on a resource, they implicitly have privileges to perform any action on that resource that does not require the users to be a delegated admin.

If a user is granted any privilege, they are able to perform actions requiring METADATA (for example, opening a table) without having to explicitly grant them METADATA privileges.

Ranger supports a delegate admin flag which is independent of the action type. It is not implied by ALL and does not imply METADATA. This is similar to the GRANT OPTION part of the ALL WITH GRANT OPTION in SQL as it is required to modify privileges in Ranger and change the owner of a Kudu table.

While the action types are hierarchical, in terms of privilege evaluation, Ranger does not have the concept of hierarchy. For instance, if a user has SELECT privilege on a database, it does not imply that the user has SELECT privilege on every table belonging to that database.

However, Ranger supports privilege wildcard matching. For example, db=a->table=\* matches all the tables that belong to database a. Therefore, in Ranger users actually need the SELECT privilege granted on db=a->table=*->column=* to allow SELECT on every table and every column in database a.

Nevertheless, with Ranger integration, when a Kudu master receives a request, it consults Ranger to determine what privileges a user has. And the required policies documented in the <<security.adoc#policy-for-kudu-masters, policy section>> are enforced to determine whether the user is authorized to perform the requested action or not.

In addition to granting privileges to a user by username, privileges can also be granted to table owners using the special {OWNER} username. These policies are evaluated only when a user tries to perform an action on a table that they own. For example, a policy can be defined for the {OWNER} user and db=*->table=* resource, and it will automatically be applied when any table is accessed by its owner. This way administrators do not need to choose between creating policies one by one for each table, and granting access to a wide range of users.