Chapter 8. The Security of RADIUS

It's a little ironic that I'm devoting a chapter (albeit shorter than the others) to the security shortcomings of the RADIUS protocol, but it's something that needs doing. Unfortunately, RADIUS—a protocol designed from the outset to provide security so that only authorized users can take advantage of resources offered to a large group of people—has security problems, and some are actually quite serious.

The most prominent security vulnerability is rooted in RADIUS's wide use. It enjoys support from a number of network equipment vendors and is found in nearly all Internet service providers and corporate dial-up implementations. This popularity, however, is a double-edged sword. Security vulnerabilities in the core RADIUS protocol leave thousands upon thousands of systems open to compromise. Further, major changes can't be made to the core protocol, because that would run the risk of breaking compatibility with those same thousands upon thousands of systems that run RADIUS.

In this chapter, I'll discuss these vulnerabilities, offer some workarounds that protect your systems better, and close with a commentary from a security analyst on why users of RADIUS should push for minor protocol changes.