In this chapter, security means allowing people to see what you want them to see and preventing them from seeing what you don't want them to see. Additionally, there are the issues of what measures you need to take on your server in order to restrict access via non-Web means. This chapter illustrates the precautions you need to take to protect your server from malicious access and modification of your web site.
The most common questions ask how to protect documents and restrict access. Unfortunately, due to the complexity of the subject and the nature of the web architecture, these questions tend to also have the most complex answers or often no convenient answers at all.
Normal security nomenclature and methodology separate the process of applying access controls into two discrete steps; in the case of the Web, they may be thought of as the server asking itself these questions:
Are you really who you claim to be?
Are you allowed to be here?
These steps are called authentication and authorization , respectively. Here's a real-world example: a flight attendant checks your photo identification (authentication) and your ticket (authorization) before permitting you to board an airplane.
Authentication can be broken down into what might be called weak and strong. Weak authentication is based on the correctness of credentials that the end user supplies (which therefore may have been stolen from the real owner—hence the name "weak"), whereas strong authentication is based ...