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CORS Essentials

CORS Essentials

By : Gunasundaram
3 (1)
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CORS Essentials

CORS Essentials

3 (1)
By: Gunasundaram

Overview of this book

This book explains how to use CORS, including specific implementations for platforms such as Drupal, WordPress, IIS Server, ASP.NET, JBoss, Windows Azure, and Salesforce, as well as how to use CORS in the Cloud on Amazon AWS, YouTube, Mulesoft, and others. It examines limitations, security risks, and alternatives to CORS. It explores the W3C Specification and major developer documentation sources about CORS. It attempts to predict what kinds of extension to the CORS specification, or completely new techniques, will come in the future to address the limitations of CORS Web developers will learn how to share code and assets across domains with CORS. They will learn a variety of techniques that are rather similar in their method and syntax. The book is organized by similar types of framework and application, so it can be used as a reference. Developers will learn about special cases, such as when a proxy is necessary. And they will learn about some alternative techniques that achieve similar goals, and when they may be preferable to using CORS
Table of Contents (10 chapters)
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Preface
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Free Chapter
1
1. Why You Need CORS
1. Why You Need CORS
The same-origin policy
Considering the origin of entities
Commonly allowed cross-origin resource sharing
Permissions required by JavaScript
How CORS works – the header and the request
CORS with Preflight
Troubleshooting and debugging CORS
CORS with jQuery
Enabling CORS globally with server configuration
Alternatives to CORS
Summary
2
2. Creating Proxies for CORS
2. Creating Proxies for CORS
Proxies and the World Wide Web
What is a proxy server?
Reasons to use a proxy
Creating a proxy server with Google App Engine
Summary
3
3. Usability and Security
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3. Usability and Security
CORS usability
Enhancing security in CORS
Summary
4
4. CORS in Popular Content Management Frameworks
4. CORS in Popular Content Management Frameworks
Incoming CORS requests
SAAS or self-hosted?
CORS in WordPress
CORS in Drupal
CORS in Joomla!
CORS in Adobe Experience Manager
Summary
5
5. CORS in Windows
5. CORS in Windows
Incoming CORS requests
How to set the Access-Control-Allow-Origin header globally in Windows IIS Server
CORS in the ASP.NET Web API
CORS in Windows Communication Foundation
CORS in Windows browsers – Internet Explorer and Edge
Summary
6
6. CORS in the Cloud
6. CORS in the Cloud
CORS requests in cloud APIs
CORS in Amazon Simple Storage Service (S3)
Using CORS in Google Cloud Storage
Authenticated access to Google APIs with CORS
CORS in IBM Cloudant
CORS in Windows Azure Storage
CORS in Box API
CORS in the Dropbox API
Summary
References
7
7. CORS in Node.js
7. CORS in Node.js
JavaScript frameworks are very popular
Introduction to Node.js
JavaScript frameworks that work with Node.js
CORS in Express.js
CORS npm for Express.js using Connect.js middleware
CORS in AngularJS
CORS in Backbone.js
Node.js and JavaScript frameworks are evolving rapidly
Summary
References
8
8. CORS Best Practices
8. CORS Best Practices
Enabling API to public CORS requests
Limiting API to allow CORS requests to a whitelisted set of origins
Protecting against cross-site request forgery (CSRF)
Summary
9
Index
Index

Enhancing security in CORS

CORS by itself does not provide any security, except for the domain allowed in the Access-Control-Allow-Origin header.

Some recommended practices for better security when using CORS are as follows:

  • Place the CORS header only on page(s) that need it; do not add the header across site

  • Use Access-Control-Allow-Origin: * only for publicly accessible static resources that do not include sensitive information or modify data

Limiting access when using the Access-Control-Allow-Origin, * wildcard

Although the CORS specification suggests that a list of allowed domains may be provided, in practice, very few clients support a list of allowed domains. Therefore, if you need to allow more than one domain, you must allow all domains with the Access-Control-Allow-Origin, * wildcard. Then, any domain, even the ones that are not intended, can make a CORS request to the page with the header.

You must provide additional security when using the wildcard if you want to prevent CORS requests...

End of Chapter 3
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