ith the increasing use of distributed systems, users often need to access multiple resources to finish a single business transaction. Traditionally, users have had to sign on to all these systems, each of which may involve different usernames and authentication requirements. With the introduction of the single sign-on technique, users can login once and be authenticated for all systems involved in a given business transaction.
Although the single sign-on concept is appealing, implementing it is not at all easy because enterprise systems often have varying security requirements and a wide range of underlying technologies on which they are deployed. In Java environments, Java Authentication and Authorization Service (JAAS) has made implementation easier. JAAS, a significant enhancement to the Java security architecture, is an ideal tool for access control in a multi-user environment where users must be granted varying privileges. Unlike the standard JDK security model, which is code-source-based permission checking, JAAS controls access to resources with both code-source-based and user/role-based permission checking. Most importantly, the "pluggable" and stackable login module architecture that JAAS defines makes it instrumental in supporting legacy security implementations on different technologies and serves as a useful mechanism for implementing single sign-on.
Single sign-on can be implemented for applications that are deployed either locally or over a network. In the case of a network, after the user logs into the primary domain, an encrypted secure token is created and sent over the wire to other applications. In local networks, user credential data is exchanged directly between applications. Both deployment options share two key challenges: passing user credential information between involved domains and translating this information.
An enterprise application can be comprised of several Web applications, each of which may depend on different technologies and data stores to retrieve the user information it needs to authenticate the user and determine his or her privilege. If a business transaction crosses the Web application boundary, the user needs to log into each Web application and present similar credentials to each of the application authentication services.
This article demonstrates a single sign-on implementation for multiple Web applications based on JAAS. Specifically, it introduces an approach to achieving single sign-on between Web applications deployed on the same application server. (see Sidebar: Security Issues of JAAS Single Sign-on Implementation)