The Web Application Hacker’s Handbook Discovering and Exploiting Security Flaws

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Chapter 3 

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Web Application Technologies

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Hex Encoding 

Many applications use straightforward hexadecimal encoding when transmit-

ting binary data, using ASCII characters to represent the hexadecimal block.

For example, hex-encoding the username “daf” within a cookie would result in:

646166

As with Base64, hex-encoded data is usually easy to spot, and you should

always attempt to decode any such data that the server sends to the client, to

understand its function.

Next Steps

So far, we have described the current state of web application (in)security,

examined the core mechanisms by which web applications can defend them-

selves, and taken a brief look at the key technologies employed in today’s

applications. With this groundwork in place, we are now in a position to start

looking at the actual practicalities of attacking web applications.

In any attack, your first task is to map the target application’s content and

functionality, to establish how it functions, how it attempts to defend itself,

and what technologies it uses. The next chapter examines this mapping

process in detail and shows how you can use it to obtain a deep understand-

ing of an application’s attack surface that will prove vital when it comes to

finding and exploiting security flaws within your target.

Questions

Answers can be found at 

www.wiley.com/go/webhacker

.

1. What is the 

OPTIONS

method used for?

2. What are the 

If-Modified-Since

and 

If-None-Match

headers used for?

Why might you be interested in these when attacking an application?

3. What is the significance of the 

secure

flag when a server sets a cookie?

4. What is the difference between the common status codes 301 and 302?

5. How does a browser interoperate with a web proxy when SSL is being

used?