Software Engineering Institute

David Litchfield of NGSSoftware has released a paper titled Hackproofing Oracle Application Server that describes a number of security issues in Oracle's PL/SQL system. This document addresses a problem in which a number of procedures in the OWA_UTIL PL/SQL application disclose sensitive information.

Quoting from Hackproofing:

PL/SQL is Oracle’s Procedural Language extension to Structured Query Language. PL/SQL packages [applications] are essentially stored procedures in the database. The package exposes procedures that can be called directly, but also has functions that are called internally from within another package. The PL/SQL module for Apache extends the functionality of a web server, enabling the web server to execute these stored PL/SQL packages in the database. The best way to imagine the PL/SQL module is like a gateway into an Oracle database server over the Web using stored procedures.
The OWA_UTIL PL/SQL application exposes a number of procedures to the web via the Apache PL/SQL module. By default, anonymous web access is permitted to some of these procedures.

OWA_UTIL.signature returns a message containing version information about the PL/SQL module. An attacker could use this procedure to verify access to OWA_UTIL.

OWA_UTIL.showsource returns the source code of the specified PL/SQL application. According to Oracle9i AS v1.0.2.2 documentation, web access to OWA_UTIL.cellsprint is prevented by default.

OWA_UTIL.cellsprint allows an attacker to run arbitrary SQL queries. Litchfield notes that queries could be made to the sys.link$ table, which could provide credentials and access to other Oracle database servers. According to Oracle9i AS v1.0.2.2 documentation, web access to OWA_UTIL.cellsprint is prevented by default.

OWA_UTIL.listprint allows an attacker to run arbitrary SQL queries, but only returns specified columns.

OWA_UTIL.show_query_columns returns column names of a database table. This procedure could be used to obtain column names for use with OWA_UTILS.listprint.

The PL/SQL module provides a configuration parameter called exclusion_list. Procedures (as well as applications and schemas) specified in exclusion_list cannot be directly executed over the web. As noted above, Oracle9i AS v1.0.2.2 documentation states that web access to OWA_UTIL.showsource and OWA_UTIL.cellsprint is prevented by default.

The vulnerable PL/SQL module may also be used by Oracle9i Database and Oracle8i Database.

An unauthenticated, remote attacker could use procedures provided by OWA_UTIL to view the source code of PL/SQL applications, obtain access credentials for other database servers, access other database servers, and perform SQL queries on accessible database servers.

Block or Restrict Access
Unauthenticated PUBLIC access to PL/SQL procedures and applications can be restricted using the exclusion_list parameter in the PL/SQL gateway configuration file, /Apache/modplsql/cfg/wdbsvr.app. This solution is described in Oracle Security Alert #28. For more information, read the section titled Protecting the PL/SQL Procedures Granted to PUBLIC in the Oracle iAS documentation under Using the PL/SQL Gateway.

Disable Vulnerable Service

Disable the PL/SQL service (modplsql or mod_plsql in Apache).