Book Image

ASP.NET Core 5 Secure Coding Cookbook

By : Roman Canlas
Book Image

ASP.NET Core 5 Secure Coding Cookbook

By: Roman Canlas

Overview of this book

ASP.NET Core developers are often presented with security test results showing the vulnerabilities found in their web apps. While the report may provide some high-level fix suggestions, it does not specify the exact steps that you need to take to resolve or fix weaknesses discovered by these tests. In ASP.NET Secure Coding Cookbook, you’ll start by learning the fundamental concepts of secure coding and then gradually progress to identifying common web app vulnerabilities in code. As you progress, you’ll cover recipes for fixing security misconfigurations in ASP.NET Core web apps. The book further demonstrates how you can resolve different types of Cross-Site Scripting. A dedicated section also takes you through fixing miscellaneous vulnerabilities that are no longer in the OWASP Top 10 list. This book features a recipe-style format, with each recipe containing sample unsecure code that presents the problem and corresponding solutions to eliminate the security bug. You’ll be able to follow along with each step of the exercise and use the accompanying sample ASP.NET Core solution to practice writing secure code. By the end of this book, you’ll be able to identify unsecure code causing different security flaws in ASP.NET Core web apps and you’ll have gained hands-on experience in removing vulnerabilities and security defects from your code.
Table of Contents (15 chapters)

Fixing XXE injection with LINQ to XML

Language-Integrated Query or LINQ is an API within the .NET framework that provides query-like syntax for writing declarative code. LINQ comes in different flavors, and LINQ to XML is one of them. LINQ to XML is an in-memory XML parser that allows you to perform XML transformations – from modifying elements and nodes to serialization.

In general, LINQ to XML is safe from XXE injection. The XDocument class has DTD processing disabled by default. However, this can be unsafe when it's instantiated with an insecure XML parser such as XmlReader. This recipe will show you how to find a security flaw in your LINQ to XML code and fix the bug by disabling DTD processing.

Getting ready

Using Visual Studio Code, open the sample Online Banking app folder at \Chapter05\xxe-injection03\before\OnlineBankingApp\.

You can perform the steps for fixing XXE injections with LINQ to XML in this folder.

How to do it…

Let's take...