Re: Read-only proc privledges

From: Pete Finnigan <plsql_at_petefinnigan.com>
Date: Wed, 27 Oct 2004 13:37:29 +0100
Message-ID: <s+4H1eCJa5fBRx4t@peterfinnigan.demon.co.uk>

Hi,

Your DBA is partly correct the only way to give access to the stored procedure code is to grant select on the view DBA_SOURCE or the underlying table SYS.SOURCE$ but doing so would give the user access to all source code held in the database. This can be demonstrated as follows:

<pre>

SQL> connect system/manager
Connected.
SQL> drop user sp cascade;

User dropped.

SQL> create user sp identified by sp;

User created.

SQL> grant create session to sp;

Grant succeeded.

SQL> grant select on sys.dba_source to sp;

Grant succeeded.

SQL>
</pre>

Now we can try and access the source of a package procedure for example DBMS_OUTPUT:
<pre>

SQL> connect sp/sp_at_sans
Connected.
SQL> select text
  2 from dba_source
  3 where name='DBMS_OUTPUT'
  4 and owner='SYS';

TEXT

package dbms_output as                                                          
                                                                                
-- DE-HEAD     <- tell SED where to cut when generating fixed package           
                                                                                
  ------------                                                                  
  --  OVERVIEW

...
{output snipped}
...

168 rows selected.

SQL>
</pre>

OK, so we can get read only access to the source code of procedures by this method. the only privileges i have granted to the read only user are CREATE SESSION and SELECT ON DBA_SOURCE.

But what is wrong with this picture? Obviously this user can now see all source stored in the database. This is not ideal unless you want to allow a user read only access to all of the source code in the database. This would be a big security risk though. A better solution would be to do the same select as above but through the view ALL_SOURCE instead. This view gives the user access to source code he owns and also to source code of procedures he has been granted EXECUTE PRIVILEGES on. This is where the your DBA got to and decided that he could not grant EXECUTE PRIVILEGE on procedures to this user.

A better solution would be to create a new view based on DBA_SOURCE and through this view expose the source code of the procedures that the read-only user actually needs to see. I would guess that this is not as complicated as it sounds. For instance the your read-only user probably needs access to a set of application procedures owned by one or more schema accounts. Creating a view based on DBA_SOURCE and restricting its output to include certain schemas only or even certain procedures by name only is a better solution. If the list of procedures your user needs to see spans multiple schema accounts and does not include all procedures for those accounts then either further restrict based on the names of the procedures or even implement a look up table of procedures names the user is allowed to see. Create the new view and optional look up table in a secure schema that has access to DBA_SOURCE and then grant select access on this view to the read-only user.

kind regards

Pete

-- 
Pete Finnigan (email:pete_at_petefinnigan.com)
Web site: http://www.petefinnigan.com - Oracle security audit specialists
Oracle security blog: http://www.petefinnigan.com/weblog/entries/index.html
Book:Oracle security step-by-step Guide - see http://store.sans.org for details.

Received on Wed Oct 27 2004 - 07:37:29 CDT