Secure PHP Development- P20 pptx

So far, our intranet application framework has the following requirements: ◆ Central authentication: Users need to be authenticated to access intranet applications.. There are likely to

Figure 4-1: A typical intranet-enabled company.

Figure 4-2: User requirements for a typical intranet-enabled company.

Each intranet application you develop must be able to authenticate and autho-rize different types of users For example, an employee vacation management application has to incorporate the hierarchical chain of command that enables employee vacation requests to be reviewed and approved first by team leaders and then by the department head So far, our intranet application framework has the following requirements:

◆ Central authentication: Users need to be authenticated to access intranet

applications There are likely to be many intranet applications within an organization and therefore user authentication should be done such that

a user logs in only once to access any application A session should be

Any Department

Department Head

Team

Employee

Project 1

Team Leader

Team

Employee

Project (n)

Team Leader

Marketing

PC

Engineering

PC PC PC

PC PC PC

Intranet Server Firewall

Database Server

Administration

PC PC PC

created that allows all applications to identify an authenticated user.

When a user attempts to access an intranet application without logging in first, the application should automatically redirect the user to the login application When the user is successfully authenticated via the login application, she should be automatically forwarded back to the applica-tion she had been attempting to access The login process should be seam-less Similarly, a central, seamless logout facility should be provided to allow the users to log out from the intranet

◆ Application-specific authorization: Different types of users exist in an

intranet and, therefore, intranet applications must discriminate when authorizing users Employee access to an intranet application will vary

Because each application will have different requirements for authorizing the user, the task of authorization should be left to the application itself

◆ A shared database: Most intranet activity involves collaboration or group

efforts For example, users working in a team within a project might need

to report the status of the project tasks individually, but the team leader or department head needs to access the information from the entire team to make technical or business decisions A shared database is therefore the solution to store data

Based on these requirements, let’s go ahead and build an intranet application framework

Building an Intranet Application Framework

An intranet consists of many applications It is a good idea to create an application framework that provides a set of commonly needed objects and services to imple-ment applications Typical intranet applications have user authentication require-ments, database access requirerequire-ments, user interfaces requirerequire-ments, and business logic requirements Each application’s business logic, which is the work done by the application, is unique and must be implemented in the application code itself

However, each application can benefit from using a standard application frame-work consisting of objects that standardize authentication, database access, user interface, etc The framework I will build here will do just that

Figure 4-3 shows the high-level design diagram for an intranet application that will use our application framework

Now let’s discuss the components of this architecture

Figure 4-3: High-level architecture diagram of an intranet application using our framework.

Using an HTML template-based presentation layer

All input and output to and from the application is handled via a template-driven HTML presentation layer When the application needs input from the user, it pre-sents an HTML page generated from an appropriate HTML template Similarly, when the application needs to display output, it generates an HTML page by replac-ing special application-specific tags within the template This ensures that cosmetic changes to the input or output interfaces can be done without requiring help from the application developer For example, an application that uses the template-based presentation layer can have its interface modified by an HTML writer or graphics artist

Using PHP Application Framework components

The components in the PHP Application Framework (PHPAF) layer implement the base application by providing the following services:

◆ Database abstraction support: See the “Relational database” section later

in this chapter for details

◆ Centralized authentication support: All applications defer the login and

logout to the central authentication facility, as discussed earlier in this chapter

Relational Database

Business Logic

Your PHP Application

PHP Application Framework Components

HTML Template-based Presentation Layer

INPUT OUTPUT

◆ Override authorization support: Each application using the intranet

application defines its own authorization method

◆ Debugging support: An application needs to be debugged many times

during the development process Because debugging is a core part of the development process, the framework includes a built-in debugger The current implementation is very simple yet useful

◆ Internationalized error and status message handling support: Each

application using the framework must use a central error message and status message repository Both error and status messages can be internationalized

Business logic

Each application has its own business-logic requirements The business-logic objects will be given database connectivity from the application framework This ensures that database abstraction is maintained

Relational database

The relational database access is abstracted from the application using an abstrac-tion layer, which is part of the applicaabstrac-tion framework This ensures that applicaabstrac-tion database requirements can change without drastically affecting the application For example, an application can be developed with this framework such that it works with the widely used, high-performance MySQL database and then deployed in an environment where the database is Oracle Of course, the developers have to be careful not to use any vendor-specific features

Figure 4-4 shows a block diagram of an application that uses the previously mentioned application framework

Figure 4-4: A block diagram of an application using the PHP Application Framework.

Application Specific Error and Status Messages (Supports Internationalization)

Database Independent Abstraction

Authentication

(Valid User Credentials)

Authorization

(Application Specific Authorization Requirements)

Application Run()

(Application Specific Driver Code)

Business Logic Objects

(Application Specific Code)

The application checks for valid user credentials in the authentication phase, which is already supplied by the framework’s login application for valid users The authorization step involves application-specific privilege management Not all valid (authenticated) users are likely to have the same privilege based on the type of application For example, an Employee Information System (EIS) applica-tion in an engineering firm can assign different privileges to executive manage-ment, department heads, team leaders, and engineers This is why the authorization code is specific to the instance of the application and should be written by the application developer and should not be provided by the framework

When an application has gone through the authentication and authorization phases, it will run the application This code will involve invoking application spe-cific business objects and database interaction

The application will have database access via the database-independent abstrac-tion and also will produce status messages and errors using the facilities provided

by the framework

Figure 4-5 shows a real-world application framework that we will create in this chapter

Figure 4-5: A real-world PHP Application Framework.

The core of this framework is the class.PHPApplication.php This class provides

an abstract PHP application that you can extend to incorporate facilities provided by the error handler (class.ErrorHandler.php), the debugger (class.Debugger.php), and the database abstraction (class.DBI.php)

DB.php (from PEAR)

class.PHPApplication.php

class.Debugger.php class.ErrorHandler.php

class.DBI.php

Your PHP Application Business

Logic