Book Image

Openswan: Building and Integrating Virtual Private Networks

By : Ken Bantoft, Paul Wouters
Book Image

Openswan: Building and Integrating Virtual Private Networks

By: Ken Bantoft, Paul Wouters

Overview of this book

<p>With the widespread use of wireless and the integration of VPN capabilities in most modern laptops, PDA's and mobile phones, there is a growing desire for encrypting more and more communications to prevent eavesdropping. Can you trust the coffee shop's wireless network? Is your neighbor watching your wireless? Or are your competitors perhaps engaged in industrial espionage? Do you need to send information back to your office while on the road or on board a ship? Or do you just want to securely access your MP3's at home? IPsec is the industry standard for encrypted communication, and Openswan is the de-facto implementation of IPsec for Linux.</p> <p>Whether you are just connecting your home DSL connection with your laptop when you're on the road to access your files at home, or you are building an industry size, military strength VPN infrastructure for a medium to very large organization, this book will assist you in setting up Openswan to suit those needs.</p> <p>The topics discussed range from designing, to building, to configuring Openswan as the VPN gateway to deploy IPsec using Openswan. It not only for Linux clients, but also the more commonly used Operating Systems such as Microsoft Windows and MacOSX. Furthermore it discusses common interoperability examples for third party vendors, such as Cisco, Checkpoint, Netscreen and other common IPsec vendors.</p> <p>The authors bring you first hand information, as they are the official developers of the Openswan code. They have included the latest developments and upcoming issues. With experience in answering questions on a daily basis on the mailing lists since the creation of Openswan, the authors are by far the most experienced in a wide range of successful and not so successful uses of Openswan by people worldwide.</p>
Table of Contents (22 chapters)
Building and Integrating Virtual Private Networks with Openswan
Credits
About the Authors
Acknowledgements
About the Reviewers
Preface

Allowing IPsec Traffic


Chapter 2 explains in detail the IPsec protocols used to permit secure communication between hosts. From the firewall perspective, this comes down to:

Protocol

Port

Description

ESP (50)

N/A

ESP (Encrypted Secure Payload)

AH (51)

N/A

AH (Authentication Header)

UDP (17)

500

IKE

UDP (17)

4500 / high port

IKE, ESPinUDP encapsulation

Note

Note that ESP is protocol 50, not port 50!

For IPsec to establish a full tunnel, you will need to permit both ESP and UDP port 500 traffic between peers. If you have IPsec peers behind NAT devices, you will also need to permit UDP port 4500, which is used by both IKE and ESPinUDP encapsulation to pass through the NAT device. Authentication Header (AH) is rarely used these days. It only provides authentication without encryption, and has come under recent attack by crypto experts as a possible vulnerability in the IPsec specification.

The rules that need to be added to the firewall rules to allow IPsec packets are shown below...