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CORS Essentials
CORS Essentials

CORS Essentials: Access web resources on different domains

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CORS Essentials

Chapter 2. Creating Proxies for CORS

A proxy generally acts as an agent or an intermediary for a client that requests for a resource from a server. In this chapter, we will learn about the following:

  • What is a proxy server?
  • Reasons to use a proxy server
  • Types of proxy server: forward and reverse proxies
  • Reverse proxy in node.js with CORS anywhere

Proxies and the World Wide Web

Generally speaking, a proxy is someone or something that has the authority to represent some other person or thing; for example, a proxy may be authorized to vote on behalf of another person.

The World Wide Web is composed of individual machines communicating with each other. A web proxy acts as an intermediary with the authority to communicate with a third-party server on behalf of a server contacting the proxy server. Modern web applications are often distributed across many servers, and proxies can tie them together.

What is a proxy server?

A proxy server handles requests from clients asking for resources from another server. The requests may be for resources, such as files, web pages, or other resources from different servers. If the request is validated, the proxy server retrieves the resource and sends it to the requesting client. There are many types of proxy; they share the common purpose of acting as intermediaries to facilitate requests between clients and target servers.

Note

Proxy servers are defined by the Internet Engineering Task Force (IETF) at

.

Proxy server connections are specified by the W3C at

.

People who work for large organizations are probably familiar with the process of configuring their web browser, or other desktop applications that require Internet access to connect through a proxy. The proxy provides them with access to the Internet, while the network firewall protects the devices inside their network from intrusions.

Note

A proxy server may eliminate the need for CORS in your application...

Proxies and the World Wide Web


Generally speaking, a proxy is someone or something that has the authority to represent some other person or thing; for example, a proxy may be authorized to vote on behalf of another person.

The World Wide Web is composed of individual machines communicating with each other. A web proxy acts as an intermediary with the authority to communicate with a third-party server on behalf of a server contacting the proxy server. Modern web applications are often distributed across many servers, and proxies can tie them together.

What is a proxy server?


A proxy server handles requests from clients asking for resources from another server. The requests may be for resources, such as files, web pages, or other resources from different servers. If the request is validated, the proxy server retrieves the resource and sends it to the requesting client. There are many types of proxy; they share the common purpose of acting as intermediaries to facilitate requests between clients and target servers.

Note

Proxy servers are defined by the Internet Engineering Task Force (IETF) at

.

Proxy server connections are specified by the W3C at

.

People who work for large organizations are probably familiar with the process of configuring their web browser, or other desktop applications that require Internet access to connect through a proxy. The proxy provides them with access to the Internet, while the network firewall protects the devices inside their network from intrusions.

Note

A proxy server may eliminate the need for CORS in your application...

Reasons to use a proxy


There are several reasons why you should place a proxy between your local domain and the target domain, which are as follows:

Avoid mixing up protocols

If your local domain application is served over SSL with HTTPS and you request a resource that is not served via SSL, the user may get a warning in the browser about mixing secure and non-secure content. Since the request to a proxy can also be made over SSL, there is no mixed content and the user sees no warning.

Some API platforms require proxies or CORS

An API hosted on a domain different from the local domain, a cloud-hosted API, or an Enterprise Service Bus (ESB) may require that cross-domain requests pass through a proxy or be handled by CORS. Apigee Edge, Mulesoft, and Google App Engine are platforms that require a proxy, or CORS, to pass requests. We will review solutions for specific platforms and applications in later chapters.

Getting through a local network firewall

In the same way that you may have to set up...

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Key benefits

  • A step-by-step guide but at a high level/fast pace. Not all steps are covered as a basic knowledge is assumed
  • Provides a basic overview of the concepts but the focus is on providing the practical skills required to develop applications
  • Focuses on providing practical examples

Description

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

Who is this book for?

Web developers have been limited by the Same Origin Policy and often wish they could spread their application across different domains. You know JavaScript and AJAX, and have run up against the Same Domain Policy, which is limiting your applications.

What you will learn

  • Why you need CORS: Bending the Same Origin Policy and basic CORS implementation, headers and XMLHttpRequest
  • Creating proxies for CORS: Sometimes the header is not enough
  • Security: vulnerabilities and how to secure your CORS application
  • CORS implementations in Content Management systems
  • Learn about CORS in Windows applications
  • Take CORS on the Cloud
  • Apply CORS in Node.js
  • Best practices for CORS

Product Details

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Publication date : May 30, 2017
Length: 144 pages
Edition : 1st
Language : English
ISBN-13 : 9781784391119
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Microsoft
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Product Details

Publication date : May 30, 2017
Length: 144 pages
Edition : 1st
Language : English
ISBN-13 : 9781784391119
Vendor :
Microsoft
Languages :

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Table of Contents

9 Chapters
1. Why You Need CORS Chevron down icon Chevron up icon
2. Creating Proxies for CORS Chevron down icon Chevron up icon
3. Usability and Security Chevron down icon Chevron up icon
4. CORS in Popular Content Management Frameworks Chevron down icon Chevron up icon
5. CORS in Windows Chevron down icon Chevron up icon
6. CORS in the Cloud Chevron down icon Chevron up icon
7. CORS in Node.js Chevron down icon Chevron up icon
8. CORS Best Practices Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
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(1 Ratings)
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3 star 100%
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1 star 0%
Bill W Sep 12, 2020
Full star icon Full star icon Full star icon Empty star icon Empty star icon 3
I thought I would get some good examples. Disappointed in that I didn't get one new thing to further my work with CORS issues
Amazon Verified review Amazon
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