Author: Jonathan Hassell

ISBN: 0596003226

Publisher: O'Reilly & Associates

Reviewed by: Dean Wilson

RADIUS (the Remote Authentication Dial-In User Service) isn't getting any younger or popular, it's a specialised technology that very few people seem to discuss and even fewer write books about. Unfortunately the ones we do have, such as this, don't exactly encourage it's adoption.

The book starts with a solid overview of the AAA process/framework, AAA in this context being Authentication, Authorisation and Access Control. This is followed by a look at the typical client authentication processes (in regards to systems layout and topology) and then finishes with a brief, and very high level, overview of RADIUS.

Chapter two introduces some of the more technical details and covers the basic packet structure, the packet types that comprise the authentication and authorisation phases of each transaction and the two main methods of authentication, PAP and CHAP. This is where I began to struggle with the book, after a concise start in the first chapter I felt I was being introduced to too much dry detail before I had a conceptual grasp or relevant overview.

While I understand the need for the reader to possess certain knowledge before advancing into the book, the facts seemed too dry and too early to encourage anyone but the most determined first time reader. If the reader was already familiar with the RADIUS protocol and applications, then this section would make a better reference guide than the RFC, although this is faint praise as it leaves the chapter in no- mans land; too dry for casual reading and not the definitive answer.

Then we get to the chapter that made me stop reading the book on my first and second attempt. Chapter 3 is an alphabetised listing of 63 RADIUS attributes taken from the RFC, but with slightly expanded explanations. It's also a chapter that you'll skip, skim-read or it will cause you to stop reading the book due to the sheer dry and frankly dull explanations.

So you've persevered, skim-read when no one was looking and made it to chapter 4! What delights await you? Well a short explanation of how RADIUS accounting works and yes, more attribute lifted from the RFC. This marks the end of what I'd consider the first part of the book (the dry as heck theory section).

Moving on from here we have two hands-on chapters that introduce FreeRADIUS, or at least they introduce an old version of the software. It's worth noting that the book was released in October 2002 (and so was probably written early in 2002) and my reading and review were both done in 2004 so the aging of the software is an inescapable issue. These chapters details configuration files that are no longer used and covers config directives that are no longer valid or make any sense. Not something that makes it easy to follow the text.

For the sake of full disclosure I'll confess I gave up half way through chapter 5 (Getting Started With FreeRADIUS), I wasn't getting anywhere trying to mentally map the configs in the book to those on screen so I just skipped this and the following chapter, Advanced FreeRADIUS, with the assumption I can learn enough about the server from current articles and the man pages.

The tragic thing is that the third part of the book, chapters 7 through to 10, is actually quite interesting, finally the author starts to discuss how RADIUS fits into the bigger picture; it's just a shame so few people will get this far. Topics include the current security problems in the protocol, what's being planned for future releases (including a short mention of a potential RADIUS replacement) and details two sample, RADIUScentric, infrastructures.

With the benefit of hindsight (and this of course is going to be highly subjective) I think the layout of the book is wrong, when you start reading the early chapters no real hook is given. You are thrown into low level details that are of very little use to beginners (I know nothing of RADIUS) too soon. Instead I think the later chapters, the where, why and how should be pulled forward and "dumb downed" to require less knowledge of how RADIUS works. These would then provide a hook to interest people and show them the more pragmatic and useful aspects of the technology. After they know it can be useful illustrate how to set up a simple server and then, in the third part, show how the underlying principles work.

The short summary? If you have no previous knowledge of RADIUS then the first and last four chapters are worth a read. If you do understand the basics then save your money and read the man pages and RFCs (when actually needed) instead. Score: 3/10