Distributed Database Administration

Authentication Through Database Links

Database links are either private or public, authenticated or non-authenticated. You create public links by specifying the PUBLIC keyword in the link creation statement. For example, you can issue:

CREATE PUBLIC DATABASE LINK foo USING 'sales';

You create authenticated links by specifying the CONNECT TO clause, AUTHENTICATED BY clause, or both clauses together in the database link creation statement. For example, you can issue:

CREATE DATABASE LINK sales CONNECT TO scott IDENTIFIED BY tiger USING 'sales';
CREATE SHARED PUBLIC DATABASE LINK sales CONNECT TO nick IDENTIFIED BY firesign 
     AUTHENTICATED BY david IDENTIFIED BY bowie USING 'sales';

This table describes how users access the remote database through the link:

Authentication Without Passwords

When using a connected user or current user database link, you can use an external authentication source such as Kerberos to obtain end-to-end security. In end-to-end authentication, credentials are passed from server to server and can be authenticated by a database server belonging to the same domain. For example, if jane is authenticated externally on a local database, and wants to use a connected user link to connect as herself to a remote database, the local server passes the security ticket to the remote database.

Supporting User Accounts and Roles

In a distributed database system, you must carefully plan the user accounts and roles that are necessary to support applications using the system. Note that:

• The user accounts necessary to establish server-to-server connections must be available in all databases of the distributed database system.

• The roles necessary to make available application privileges to distributed database application users must be present in all databases of the distributed database system.

As you create the database links for the nodes in a distributed database system, determine which user accounts and roles each site needs to support server-to-server connections that use the links.

In a distributed environment, users typically require access to many network services. When you must configure separate authentications for each user to access each network service, security administration can become unwieldy, especially for large systems.

Centralized User and Privilege Management

The database provides different ways for you to manage the users and privileges involved in a distributed system. For example, you have these options:

• Enterprise user management. You can create global users who are authenticated through SSL or by using passwords, then manage these users and their privileges in a directory through an independent enterprise directory service.

• Network authentication service. This common technique simplifies security management for distributed environments. You can use the Oracle Advanced Security option to enhance Oracle Net and the security of an Oracle Database distributed database system. Windows NT native authentication is an example of a non-Oracle authentication solution.

  See Also:

  • Oracle Database Advanced Security Administrator's Guide

  • Oracle Database Enterprise User Security Administrator's Guide

CREATE USER fred IDENTIFIED GLOBALLY AS 'CN=fred adams,O=Oracle,C=England';

Schema-Independent Global Users

The database supports functionality that allows a global user to be centrally managed by an enterprise directory service. Users who are managed in the directory are called enterprise users. This directory contains information about:

• Which databases in a distributed system an enterprise user can access

• Which role on each database an enterprise user can use

• Which schema on each database an enterprise user can connect to

The administrator of each database is not required to create a global user account for each enterprise user on each database to which the enterprise user needs to connect. Instead, multiple enterprise users can connect to the same database schema, called a shared schema.

Note:

You cannot access a current user database link in a shared schema.

For example, suppose jane, bill, and scott all use a human resources application. The hq application objects are all contained in the guest schema on the hq database. In this case, you can create a local global user account to be used as a shared schema. This global username, that is, shared schema name, is guest. jane, bill, and scott are all created as enterprise users in the directory service. They are also mapped to the guest schema in the directory, and can be assigned different authorizations in the hq application.

Figure 30-5 illustrates an example of global user security using the enterprise directory service:

Figure 30-5 Global User Security

Description of "Figure 30-5 Global User Security"

Assume that the enterprise directory service contains the following information on enterprise users for hq and sales:

Database	Role	Schema	Enterprise Users
tb	clerk1	guest	bill scott
sales	clerk2	guest	jane scott

Also, assume that the local administrators for hq and sales have issued statements as follows:

Database	CREATE Statements
hq	CREATE USER guest IDENTIFIED GLOBALLY AS ''; CREATE ROLE clerk1 GRANT select ON emp; CREATE PUBLIC DATABASE LINK sales_link CONNECT AS CURRENT_USER USING 'sales';
sales	CREATE USER guest IDENTIFIED GLOBALLY AS ''; CREATE ROLE clerk2 GRANT select ON dept;

Assume that enterprise user scott requests a connection to local database hq in order to execute a distributed transaction involving sales. The following steps occur (not necessarily in this exact order):

1. Enterprise user scott is authenticated using SSL or a password.

2. User scott issues the following statement:

   SELECT e.ename, d.loc 
   FROM emp e, dept@sales_link d
   WHERE e.deptno=d.deptno;
   

3. Databases hq and sales mutually authenticate one another using SSL.

4. Database hq queries the enterprise directory service to determine whether enterprise user scott has access to hq, and discovers scott can access local schema guest using role clerk1.

5. Database sales queries the enterprise directory service to determine whether enterprise user scott has access to sales, and discovers scott can access local schema guest using role clerk2.

6. Enterprise user scott logs into sales to schema guest with role clerk2 and issues a SELECT to obtain the required information and transfer it to hq.

7. Database hq receives the requested data from sales and returns it to the client scott.

   See Also:

   Oracle Database Enterprise User Security Administrator's Guide for more information about enterprise user security

Data Encryption

The Oracle Advanced Security option also enables Oracle Net and related products to use network data encryption and checksumming so that data cannot be read or altered. It protects data from unauthorized viewing by using the RSA Data Security RC4 or the Data Encryption Standard (DES) encryption algorithm.

To ensure that data has not been modified, deleted, or replayed during transmission, the security services of the Oracle Advanced Security option can generate a cryptographically secure message digest and include it with each packet sent across the network.

Enterprise Manager

Enterprise Manager is the Oracle Database administration tool that provides a graphical user interface (GUI). Enterprise Manager provides administrative functionality for distributed databases through an easy-to-use interface. You can use Enterprise Manager to:

• Administer multiple databases. You can use Enterprise Manager to administer a single database or to simultaneously administer multiple databases.

• Centralize database administration tasks. You can administer both local and remote databases running on any Oracle Database platform in any location worldwide. In addition, these Oracle Database platforms can be connected by any network protocols supported by Oracle Net.

• Dynamically execute SQL, PL/SQL, and Enterprise Manager commands. You can use Enterprise Manager to enter, edit, and execute statements. Enterprise Manager also maintains a history of statements executed.

  Thus, you can reexecute statements without retyping them, a particularly useful feature if you need to execute lengthy statements repeatedly in a distributed database system.

• Manage security features such as global users, global roles, and the enterprise directory service.

Third-Party Administration Tools

Currently more than 60 companies produce more than 150 products that help manage Oracle Databases and networks, providing a truly open environment.

SNMP Support

Besides its network administration capabilities, Oracle Simple Network Management Protocol (SNMP) support allows an Oracle Database server to be located and queried by any SNMP-based network management system. SNMP is the accepted standard underlying many popular network management systems such as:

• HP OpenView

• Digital POLYCENTER Manager on NetView

• IBM NetView/6000

• Novell NetWare Management System

• SunSoft SunNet Manager