Book Image

Web Penetration Testing with Kali Linux - Third Edition

By : Gilberto Najera-Gutierrez, Juned Ahmed Ansari
Book Image

Web Penetration Testing with Kali Linux - Third Edition

By: Gilberto Najera-Gutierrez, Juned Ahmed Ansari

Overview of this book

Web Penetration Testing with Kali Linux - Third Edition shows you how to set up a lab, helps you understand the nature and mechanics of attacking websites, and explains classical attacks in great depth. This edition is heavily updated for the latest Kali Linux changes and the most recent attacks. Kali Linux shines when it comes to client-side attacks and fuzzing in particular. From the start of the book, you'll be given a thorough grounding in the concepts of hacking and penetration testing, and you'll see the tools used in Kali Linux that relate to web application hacking. You'll gain a deep understanding of classicalSQL, command-injection flaws, and the many ways to exploit these flaws. Web penetration testing also needs a general overview of client-side attacks, which is rounded out by a long discussion of scripting and input validation flaws. There is also an important chapter on cryptographic implementation flaws, where we discuss the most recent problems with cryptographic layers in the networking stack. The importance of these attacks cannot be overstated, and defending against them is relevant to most internet users and, of course, penetration testers. At the end of the book, you'll use an automated technique called fuzzing to identify flaws in a web application. Finally, you'll gain an understanding of web application vulnerabilities and the ways they can be exploited using the tools in Kali Linux.
Table of Contents (19 chapters)
Title Page
Copyright and Credits
Packt Upsell

Command injection

Web applications, which are dynamic in nature, may use scripts to invoke some functionality within the operating system on the web server to process the input received from the user. An attacker may try to get this input processed at the command line by circumventing the input validation filters implemented by the application. Command injection usually invokes commands on the same web server, but it is possible that the command can be executed on a different server, depending on the architecture of the application.

Let's take a look at a simple code snippet, that is vulnerable to a command injection flaw, taken from DVWA's command injection exercise. It is a very simple script that receives an IP address and sends pings (ICMP packets) to that address:

  $target = $_REQUEST[ 'ip' ]; 
  $cmd = shell_exec( 'ping  -c 3 ' . $target ); 
  $html .= '<pre>'.$cmd.'</pre>'; 
  echo $html; 

As you can see, there is no input validation before accepting the...