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

Limitations of the Random Device


The other issue at startup is entropy from /dev/random. In July 2004, 1006 IPsec Tunnels were established in 205 seconds (~3.5 minutes), giving a rate of 5 tunnels/sec. This scales linearly, if the tunnel initiation rate does not increase. The CPU load during the test was always around 60% to 90% (very low).

The main problem we found was that there was a bottleneck in the Linux kernel random number generator. Switching from /dev/random to /dev/urandom increased the set-up rate to 10 tunnels per second, at the risk of being slightly less secure due to not-as-random numbers being used for the Diffe-Hellman calculations.

Note that both versions 1 and 2 of Openswan already use /dev/urandom, which is safe enough for generating the session keys that normally only last for an hour anyway. When the ipsec newhostkey command is used to generate long-term RSA keys, Openswan explicitly uses /dev/random to generate these keys.

If you are using a VIA CPU with the PadLock...