This page will outline design of Howl Security.
Related Hive Work
Initially the thought is that Howl will have authorization implemented at some level to provide security. The initial implementation will be based on HDFS directory permissions. This may be enhanced/replaced by a role based model in a later release.
The initial idea for authorization in Howl is to use the HDFS permissions to authorize metadata operations. To be able to do this, we would like to extend createTable() to add the ability to record a different group from the user's primary group and to record the complete Unix permissions on the table directory. Also, we would like to have a way for partition directories to inherit permissions and group information based on the table directory. To keep the metastore backward compatible for use with Hive, I propose having conf variables to achieve these objectives:
table.group.name : value will indicate the name of the Unix group for the table directory. This will be used by createTable() to perform a chgrp to the value provided. This property will provide the user the ability to choose from one of the many Unix groups he is part of to associate with the table.
table.permissions : value will be of the form rwxrwxrwx to indicate read-write-execute permissions on the table directory. This will be used by createTable() to perform a chmod to the value provided. This will let the user decide what permissions he wants on the table.
partitions.inherit.permissions : a value of true will indicate that partitions inherit the group name and permissions of the table level directory. This will be used by addPartition() to perform a chgrp and chmod to the values as on the table directory.
Conf properties are preferable over API changes since the complete authorization design for Hive is not finalized yet. These properties can be deprecated/removed when that is in place. These properties would also be useful to some installation of vanilla Hive since at least DFS level authorization can now be achieved by Hive without the user having to manually perform chgrp and chmod operations on DFS.
Reading data(Select)/Writing data (Insert)
This will simply be governed by the dfs permission at the time of the read and will result in runtime errors if the user does not have permissions.
Internal/External table without location specified
If the user has permissions to the directory pointed by hive.metastore.warehouse.dir then he can create the table.
Internal/External table with location specified
If the user has permissions to the location specified then he can create the table.
A user can drop a table (internal or external) only if he has write permissions to the table directory. A user could have write permission either by virtue of him being the owner of the table or through the group he belongs to. So if the permissions on the table directory allow him to write to it, he can drop the table.
Partition directories will inherit the permissions/(owner,group) of the table directory.
A user can "alter" table if he has write permissions on the table directory. So any of the following alter table commands are allowed only if the user has write permissions on the table directory:
ALTER TABLE table_name ADD partition_spec [ LOCATION 'location1' ] partition_spec [ LOCATION 'location2' ] ...
ALTER TABLE table_name DROP partition_spec, partition_spec,...
ALTER TABLE table_name RENAME TO new_table_name
ALTER TABLE table_name CHANGE [COLUMN] col_old_name col_new_name column_type [COMMENT col_comment] [FIRST|AFTER column_name]
ALTER TABLE table_name ADD|REPLACE COLUMNS (col_name data_type [COMMENT col_comment], ...)
ALTER TABLE table_name SET TBLPROPERTIES table_properties
ALTER TABLE table_name SET SERDE serde_class_name [WITH SERDEPROPERTIES serde_properties]
ALTER TABLE table_name SET SERDEPROPERTIES serde_properties
ALTER TABLE table_name SET FILEFORMAT file_format
ALTER TABLE table_name CLUSTERED BY (col_name, col_name, ...) [SORTED BY (col_name, ...)] INTO num_buckets BUCKETS
ALTER TABLE table_name TOUCH;
ALTER TABLE table_name TOUCH PARTITION partition_spec;
Since the top level warehouse dir will have read/write permissions for everyone, show tables will show all tables to all users.
Show Table/Partitions Extended
A user can issue "show table/partitions extended" on a table only if he has read permissions on the table directory. This query is of the form:
SHOW TABLE EXTENDED [IN|FROM database_name] LIKE identifier_with_wildcards [PARTITION(partition_desc)]
A user can issue show partitions on a table only if he has read permissions on the table directory.
A user can issue describe table/column/partition on a table only if he has read permissions on the table directory.
Database related operations
Just like create table, create db will have db.group.name and db.permissions properties which will dictate the group and permissions of the db directory. This will be set up by the Howl CLI and the database directory will need to be updated with the appropriate chgroup and chmod operations. There will be NO inheritance of permissions from db directory to table directory. The table directory can have potentially different group/perms from the db directory.
use db will be permitted only if the user has read permission on the db directory. So subsequent operation like create table will still be authorized based on the rules laid above once the use db call has been authorized. So the user would need write permission on the db directory to be able create the table directory under it.
If db.tablename syntax is supported (I believe it may not be supported in the initial commit), then create db.tablename will need to check that the user has write permission on db directory.
Howl specific semantic Analyzers
To implement a CLI, Howl will have Howl specific semantic analyzers in place. It will be in these Howl specific semantic analyzers that the checks outlined above will be made to implement authorization.
The Howl CLI program will take --group and --perms commandline options which will only apply to create table DDL queries. The value for --group will indicate the name of the Unix group for the table directory. The value for --perms will be of the form rwxrwxrwx which will indicate the Unix permissions on the table directory. The CLI program will have to partially parse the user supplied query to look for create table .* and set these values in the HiveConf (for use by createTable() metastore API). If these are not supplied, the CLI program should check what the umask is and warn the user that the table will be create with permissions dictated by the umask and if that is not intended, the user should drop and re-create the table with --group and --perms options. Similarly it should warn when the perms are too permissive like rwx for others.
To be able to do this, we should extend createTable() to add the ability to record a different group from the user's primary group and to record the complete Unix permissions on the table directory. Also, we would like to have a way for partition directories to inherit permissions and group information based on the table directory. To keep the metastore backward compatible for use with Hive, the conf variables discussed above will be used.
The Howl CLI will always set the property partitions.inherit.permissions to true. createTable() should also store these as table properties in the metastore so that a subsequent addPartition() can look at these and also do a chgrp and chmod - the changes in addPartition() should also be implemented.
One line of thought is to use HTTP as transport and Thrift as serialization mechanism. Since in this setup the Howl server would be a Tomcat server, standard means of authentication for a tomcat server can be used. The one challenge is that HowlOutputFormat will need to connect to this server from the cluster nodes - authenticating those requests is difficult since they are on behalf of the user and not by the user himself.
Design yet to come.