RE: Supplied Packages, Database Links, and SQL Injection

  • From: "Hostetter, Jay M" <JHostetter@xxxxxxxxxxxxxxxxxxxx>
  • To: <ian@xxxxxxxxxxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
  • Date: Tue, 9 May 2006 15:05:36 -0400

These are the standard revokes that I issue.  If a user needs it, I
grant it directly to that user.  I put these revokes right into
postDBCreation.sql that is generated by DBCA.  

/* Revoke privileges per page 715 of the Admin Manual (Security
Checklist).  */
revoke execute on utl_smtp    from public;
revoke execute on utl_tcp     from public;
revoke execute on utl_http    from public;
revoke execute on utl_file    from public;
revoke execute on dbms_random from public;

/* From Oracle9i Application Developer's Guide - Fundamentals  Ch. 14 */
revoke execute on dbms_obfuscation_toolkit from public;

/* Oracle Database Security Benchmark v1.1 */
revoke execute on dbms_lob from public;
revoke execute on dbms_job from public; 

Some new revokes to consider:

/* Related to CPUApr2006 -
http://www.red-database-security.com/advisory/oracle_cpu_apr_2006.html
*/
revoke execute on dbms_reputil          from public;
revoke execute on dbms_snapshot_utl     from public;
revoke execute on dbms_export_extension from public;

You are right - it's fairly easy to find existing stored objects that
will break if you make these revokes.  It's a bit more difficult for the
anonymous blocks.  I modified an old query for v$db_object_cache in an
attempt to find out if one of these packages was called recently.  I'm
sure somebody could improve upon it:

select owner || '.' || name OBJECT
        , type
        , to_char(sharable_mem/1024,'9,999.9') "SPACE(K)"
        , loads
        , executions execs
        , kept
from v$db_object_cache
where name in ('UTL_SMTP','UTL_TCP','UTL_HTTP','UTL_FILE','DBMS_RANDOM',
    'DBMS_OBFUSCATION_TOOLSKIT','DBMS_LOB','DBMS_JOB')
order by owner, name
;

Jay

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of MacGregor, Ian A.
Sent: Tuesday, May 09, 2006 2:18 PM
To: oracle-l
Subject: Supplied Packages, Database Links, and SQL Injection

Certain supplied packages such as dbms_export_extension are flawed, you
can inject SQL such as "grant dba to me;"  into them and the code will
be executed.  Now suppose you are pulling data from a database which
includes sensitive information to one that does not via a database link.
No sensitive data is accessible, the account on the sensitive database
to which the database link connects has no privilege to access the
sensitive objects.  However there is a package, I'll call it dbms_flawed
which is exploitable via  SQL injection.  A user runs
dbms_flawed.exeute_this@remote_db('grant dba to me')  thereby gaining
that privilege or execute dbms_flawed.execute@remote_db('grant all on
trusted_user.cofidential_info_table to me');  The controls setup to
prevent improper access are bypassed.

The answer is to to not allow "me" to execute dbms_flawed.  However,
there are other packages which might now or someday be exploitable.  How
are folks handling this.  Have you revoked execute privileges from
public from all packages, a certain set of packages (if so which ones)?
Is there a list of packages which have the potential to be exploited.
Revoking privileges can be tricky.  Dba_dependencies will find  calls
from stored procedures, but not anonymous blocks.



Ian MacGregor
Stanford Linear Accelerator Center
ian@xxxxxxxxxxxxxxxxx








  
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