[refpolicy] [PATCH] New database object classes

KaiGai Kohei kaigai at ak.jp.nec.com
Fri Dec 10 03:49:24 CST 2010


The attached patch adds a few database object classes, as follows:

* db_schema
------------
A schema object performs as a namespace in database; similar to
directories in filesystem.
It seems some of (but not all) database objects are stored within
a certain schema logically. We can qualify these objects using
schema name. For example, a table: "my_tbl" within a schema: "my_scm"
is identified by "my_scm.my_tbl". This table is completely different
from "your_scm.my_tbl" that it a table within a schema: "your_scm".
Its characteristics is similar to a directory in filesystem, so
it has similar permissions.
The 'search' controls to resolve object name within a schema.
The 'add_name' and 'remove_name' controls to add/remove an object
to/from a schema.
See also,
  http://developer.postgresql.org/pgdocs/postgres/sql-createschema.html

In the past discussion, a rubix folks concerned about no object
class definition for schema and catalog which is an upper level
namespace. Since I'm not certain whether we have a disadvantage
when 'db_schema' class is applied on catalog class, I don't add
this definition yet.

Default security context of 'db_table' and 'db_procedure' classes
get being computed using type_transition with 'db_schema' class,
instead of 'db_database' class. It reflects logical hierarchy of
database object more correctly.


* db_view
----------
A view object performs as a virtual table. We can run SELECT
statement on views, although it has no physical entities.
The definition of views are expanded in run-time, so it allows
us to describe complex queries with keeping readability.
This object class uniquely provides 'expand' permission that
controls whether user can expand this view, or not.
The default security context shall be computed by type transition
rule with a schema object that owning the view.

See also,
  http://developer.postgresql.org/pgdocs/postgres/sql-createview.html


* db_sequence
--------------
A sequence object is a sequential number generator.
This object class uniquely provides 'get_value', 'next_value' and
'set_value' permissions. The 'get_value' controls to reference the
sequence object. The 'next_value' controls to fetch and increment
the value of sequence object. The 'set_value' controls to set
an arbitrary value.
The default security context shall be computed by type transition
rule with a schema object that owning the sequence.

See also,
  http://developer.postgresql.org/pgdocs/postgres/sql-createsequence.html


* db_language
--------------
A language object is an installed engine to execute procedures.
PostgreSQL supports to define SQL procedures using regular script
languages; such as Perl, Tcl, not only SQL or binary modules.
In addition, v9.0 or later supports DO statement. It allows us to
execute a script statement on server side without defining a SQL
procedure. It requires to control whether user can execute DO
statement on this language, or not.
This object class uniquely provides 'implement' and 'execute'
permissions. The 'implement' controls whether a procedure can
be implemented with this language, or not. So, it takes security
context of the procedure as subject. The 'execute' controls to
execute code block using DO statement.
The default security context shall be computed by type transition
rule with a database object, because it is not owned by a certain
schema.

In the default policy, we provide two types: 'sepgsql_lang_t' and
'sepgsql_safe_lang_t' that allows unpriv users to execute DO
statement. The default is 'sepgsql_leng_t'.
We assume newly installed language may be harm, so DBA has to relabel
it explicitly, if he want user defined procedures using the language.

See also,
  http://developer.postgresql.org/pgdocs/postgres/sql-createlanguage.html
  http://developer.postgresql.org/pgdocs/postgres/sql-do.html

P.S)
I found a bug in MCS. It didn't constraint 'relabelfrom' permission
of 'db_procedure' class. IIRC, I fixed it before, but it might be
only MLS side. Sorry.

Thanks,
-- 
KaiGai Kohei <kaigai at ak.jp.nec.com>
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