1. Remote Authenticator /Authorizer Instructor: 張顧耀 老師 Student: 曾冠樺

2. Author and Source Author: Eduardo B. Fernandez and Reghu Warrier Dept. of Computer Science and Eng.Florida Atlantic University Boca Raton, FL, USA Source: PLoP 2003

3. Outline Introduction Intent Example Problem of this Example Forces Solution Implementation Consequence

4. Introduction Many distributed systems need to access shared resources. We need a secure and easily manageable authentication and authorization mechanism.

5. Introduction We present here a pattern called remote authentication/authorization pattern. This is a composite pattern consisting of two known patterns: 1. Proxy. 2. Role-Based Access Control.

6. Intent Provide facilities for authentication and authorization when accessing shared resources in a loosely-coupled distributed system.

7. Example A multinational corporation in the US and Brazil. Assume an employee from the US is traveling to Brazil and has the need to access some data from the Brazilian database servers.

8. Example There are two possible ways to achieve this 1. Replicate. 2. Borrow. Both of these solutions have their disadvantages.

9. Problem of this example How can we provide authentication and authorization in a distributed environment without the need for redundant user login information? The changes of the consumer activities.

10. Forces No more redundant. Transparent. Standardize the roles. Keep the user ID.

11. Solution Set up a single entry point that can transparently redirect the user to the correct server where his user login and access information can be validated.

12. Solution: Proxy Pattern Definition: Provide a surrogate or placeholder for another object to control access to it.

13. Solution: Proxy Pattern { // Mainapp test application class MainApp { static void Main() { // Create math proxy MathProxy p = new MathProxy(); // Do the math Console.WriteLine("4 + 2 = " + p.Add(4, 2)); Console.WriteLine("4 - 2 = " + p.Sub(4, 2)); Console.WriteLine("4 * 2 = " + p.Mul(4, 2)); Console.WriteLine("4 / 2 = " + p.Div(4, 2)); // Wait for user Console.Read(); } }

14. Solution: Proxy Pattern // "Subject" public interface IMath { double Add(double x, double y); double Sub(double x, double y); double Mul(double x, double y); double Div(double x, double y); } // "RealSubject" class Math : IMath { public double Add(double x, double y){return x + y;} public double Sub(double x, double y){return x - y;} public double Mul(double x, double y){return x * y;} public double Div(double x, double y){return x / y;} }

15. Solution: Proxy Pattern // "Proxy Object" class MathProxy : IMath { Math math; public MathProxy() { math = new Math(); } public double Add(double x, double y) { return math.Add(x,y); } public double Sub(double x, double y) { return math.Sub(x,y); } public double Mul(double x, double y) { return math.Mul(x,y); } public double Div(double x, double y) { return math.Div(x,y); } } }

16. Solution: Role Based Access Control Pattern Problem: Web-based systems have a variety of users: company employees, customers, partners, search engines, etc. How to assign rights to users according to their roles.

17. Solution: Role Based Access Control Pattern Forces: 1. Different needs for access to information. 2. Storing. 3. Define precisely. 4. Users may have more than one role. 5. Hierarchies of roles, with inheritance of rights. 6. to individual users or to groups of users.

18. Solution: Role Based Access Control Pattern Classes User and Role describe the registered users and the predefined roles, respectively. Users are assigned to roles, roles are given rights according to their functions. The association class Right defines the access types that a user within a role is authorized to apply to the protection object. In fact, the combination Role, ProtectionObject, and Right is an instance of the Authorization pattern.

19. Solution: Role Based Access Control Pattern

20. Solution

21. Implementation Remote Authentication Dial-In User Service (RADIUS) is a widely deployed IETF protocol enabling centralized authentication, authorization, and accounting for network access

22. Implementation

24. Consequence: Advantage 1. Roaming. 2. Store the user login and access rights at a single location. 3. The user's login ID, password etc. are stored in the internal RADIUS database or can be accessed from an SQL Database. 4. Transparent. 5. Units such as active cards [ACS] allow complex request/challenge interactions.

25. Consequence: Disadvantage The additional messages used increase overhead, thus reducing performance for simple requests. The system is more complex than a system that directly validates clients.

26. The End Thank You!!!