Chapter 9. Designing a Secure Directory

Protecting the directory from unauthorized access may seem straightforward, but implementing a secure solution may be more complex than it first appears. A number of potential access points exist on the directory information delivery path where an unauthorized client may gain access to data.

For example, an unauthorized client can use another client's credentials to access the data. This is particularly likely when the directory uses unprotected passwords. An unauthorized client can also eavesdrop on the information exchanged between a legitimate client and Directory Server.

Unauthorized access can occur from inside the company or, if the company is connected to an extranet or to the Internet, from outside the company.

The following scenarios describe just a few examples of how an unauthorized client might access the directory data.

The authentication methods, password policies, and access control mechanisms provided by the Directory Server offer efficient ways of preventing unauthorized access. See the following sections for more information:

If intruders gain access to the directory or intercept communications between Directory Server and a client application, they have the potential to modify (or tamper with) the directory data. The directory service is useless if the data can no longer be trusted by clients or if the directory itself cannot trust the modifications and queries it receives from clients.

For example, if the directory cannot detect tampering, an attacker could change a client's request to the server (or not forward it) and change the server's response to the client. TLS and similar technologies can solve this problem by signing information at either end of the connection. For more information about using TLS with Directory Server, see Section 9.9, “Securing Server Connections”.

In a denial of service attack, the attacker's goal is to prevent the directory from providing service to its clients. For example, an attacker might use all of the system's resources, thereby preventing these resources from being used by anyone else.

Directory Server can prevent denial of service attacks by setting limits on the resources allocated to a particular bind DN. For more information about setting resource limits based on the user's bind DN, see the "User Account Management" chapter in the Red Hat Directory Server Administration Guide.