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Mastering Modern Web Penetration Testing

You're reading from   Mastering Modern Web Penetration Testing Master the art of conducting modern pen testing attacks and techniques on your web application before the hacker does!

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Product type Paperback
Published in Oct 2016
Publisher Packt
ISBN-13 9781785284588
Length 298 pages
Edition 1st Edition
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Authors (2):
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Prakhar Prasad Prakhar Prasad
Author Profile Icon Prakhar Prasad
Prakhar Prasad
Rafay Baloch Rafay Baloch
Author Profile Icon Rafay Baloch
Rafay Baloch
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Toc

Table of Contents (13) Chapters Close

Preface 1. Common Security Protocols FREE CHAPTER 2. Information Gathering 3. Cross-Site Scripting 4. Cross-Site Request Forgery 5. Exploiting SQL Injection 6. File Upload Vulnerabilities 7. Metasploit and Web 8. XML Attacks 9. Emerging Attack Vectors 10. OAuth 2.0 Security 11. API Testing Methodology Index

XML quadratic blowup


The XML quadratic blowup attack is a denial of service attack vector against an XML parser. Before I start writing about XQB, let me first explain a technique known as billion laughs, which doesn't work nowadays but will give you a foundation toward XQB.

XML billion laughs

The XML billion laughs DoS attack simply starts by declaring an XML document with an entity named lol (hence the name laugh gets associated with it, but in a general case it can be any valid name). The entity is then nested recursively 10 times (or more). This forces the XML parser to allocate memory for every single entity reference. Hence a huge chunk of memory gets wasted, by sending the same XML document again and again; one can simply choke a server out of all memory, eventually killing it. However, parsers these days detect nested XML entities and stop parsing immediately, killing this vector. A classic XML billion laughs XML payload is as follows:

<?xml version="1.0"?>
<!DOCTYPE lolz...
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