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Trusted clients vs. untrusted clients

A brief look at the CLIENT authentication types in DB2 UDB 8.1.

Controlling database access is one of the first steps in making sure your data is protected. There are various types of authentication available. The different types of authentication are usually distinguished by where and how the user is authenticated. Some examples of the different authentication types are SERVER, SERVER_ENCRYPT, CLIENT, KERBEROS or KRB_ SERVER_ENCRYPT. This tip from InformIT examines the CLIENT authentication type and the ways in which Version 8.1 of DB2 UDB handles client authentication.

If both the server and the client are configured to use the CLIENT authentication type, authentication occurs at the client workstation (if the database is a nonpartitioned database) or at the database partition where the client application is invoked from (if the database is a partitioned database), using the security facility that is provided by the client's operating system. But what happens if the client workstation is using an operating system that does not contain a tightly integrated security facility, and no separate add-on security facility has been made available? Does such a configuration compromise security? The answer is no. However, in such environments, the DB2 Database Manager for the instance at the server must be able to determine which clients will be responsible for validating users and which clients will be forced to let the server handle user authentication. To make this distinction, clients that use an operating system that contains an integrated security facility (for example, Windows NT, Windows 2000, all supported versions of UNIX, MVS, OS/390, VM, VSE, and AS/400) are classified as trusted clients, and clients that use an operating system that does not provide an integrated security facility (for example, Windows 95, Windows 98, and Windows Millennium Edition) are classified as untrusted clients.

The trust_allclnts parameter of a DB2 Database Manager configuration file helps the DB2 Database Manager for an instance on a server anticipate whether its clients are to be treated as trusted or untrusted. If this configuration parameter is set to YES (which is the default), the DB2 Database Manager assumes that any client that accesses the instance is a trusted client and that authentication will take place at the client. However, if this configuration parameter is set to NO, the DB2 Database Manager assumes that one or more untrusted clients will be used to access the server; therefore, all users must be authenticated at the server. (If this configuration parameter is set to DRDAONLY, only MVS, OS/390, VM, VSE, and OS/400 clients will be treated as trusted clients.) It is important to note that regardless of how the trust_allclnts parameter is set, whenever an untrusted client attempts to access an instance or a database, user authentication always takes place at the server.

In some situations, it may be desirable to authenticate users at the server, even when no untrusted clients will need access. In such situations, the trust_clntauth configuration parameter of a DB2 Database Manager configuration file can be used to control where trusted clients are to be validated. By accepting the default value for this parameter (which is CLIENT), authentication for trusted clients will take place at the client workstation. However, if the value for this parameter is changed to SERVER, authentication for all trusted clients will take place at the server.

Read more about authentication and security in DB2 at InformIT.


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