Remote Authenticator /Authorizer

Instructor: 張顧耀 老師Student: 曾冠樺

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

Outline

Introduction Intent Example Problem of this Example Forces Solution Implementation Consequence

Introduction

Many distributed systems need to access shared resources.

We need a secure and easily manageable authentication and authorization mechanism.

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.

Intent

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

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.

Example

There are two possible ways to achieve this

1. Replicate.

2. Borrow.

Both of these solutions have their disadvantages.

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.

Forces

No more redundant.

Transparent.

Standardize the roles.

Keep the user ID.

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.

Solution: Proxy Pattern Definition:

Provide a surrogate or placeholder for another object to control access to it.

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();    }  } 

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;}  }

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);     }  }}

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.

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.

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.

Solution: Role Based Access Control Pattern

Solution

Implementation

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

Implementation

Implementation

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.

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.

The End

Thank You!!!