Book Image

CORS Essentials

By : Rajesh Gunasundaram
Book Image

CORS Essentials

By: Rajesh 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

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CORS Essentials
Rajesh Gunasundaram
May, 2017 | 144 pages
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Table of Contents (15 chapters)
CORS Essentials
CORS Essentials
Credits
Credits
About the Authors
About the Authors
www.PacktPub.com
www.PacktPub.com
Customer Feedback
Customer Feedback
Preface
Preface
Free Chapter
1
Why You Need CORS
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
Creating Proxies for CORS
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
Usability and Security
Usability and Security
CORS usability
Enhancing security in CORS
Summary
4
CORS in Popular Content Management Frameworks
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
CORS in Windows
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
CORS in the Cloud
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
CORS in Node.js
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
CORS Best Practices
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
Index
Index

CORS in Windows browsers – Internet Explorer and Edge

The good news is that Edge, the browser that ships with Windows 10, and Internet Explorer 10 fully support the W3C specification for CORS, and you can use standard techniques with XmlHttpRequest (XHR) and CORS headers. Internet Explorer 7 and older versions do not support CORS at all.

According to Can I Use... (as of August 2015), CORS is supported by 97.69% of browsers in the USA and 92.76% globally. For more information about CORS support in browsers, see the Can I Use... page for CORS: .

In Internet Explorer 8 and 9, you have to use feature detection and XDomainRequest instead of XHR. We covered using XDomainRequest in Chapter 1, Why You Need CORS.

The following example shows how to detect XHR withCredentials and XDomainRequest support. If a new XmlHttpRequest has "withCredentials", then CORS is supported; if the window has XDomainRequest, then that method is supported; if neither is present, you cannot use CORS:

function browserSupportsCors...
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