Subject: Re: [saag] RADIUS is deprecating MD5

From: Peter Gutmann <[email-masked]>
Date: Mon, 1 Apr 2024 07:04:06 +0000

Viktor Dukhovni <[email-masked]> writes:

>Others can speak to whether or not the deprecation is or isn't overly
>disruptive relative to the benefits.

It depends on whether RADIUS is being used for authentication or as a
transport layer.  As I've already pointed out, with RADIUS-for-transport
there's nothing to fix because RADIUS isn't doing anything that matters.

For those who aren't familiar with how this works, the layering is as follows:

UDP - Unreliable, and fragments
RADIUS - Fragments again, but differently to UDP.
EAP-over-RADIUS
EAP - Fragments yet again, and differently again.
A turtle
More turtles
Four elephants
Some form of TLS encapsulation, e.g. EAP-TLS, PEAP, etc
*** TLS ***
EAP/DIAMETER/some mess Microsoft invented
The authentication you're using, often MSCHAPv2 by the time you get here

Of all that mess, the only parts that matter are the TLS tunnel and the
authentication run inside it.  Everything before the point marked *** TLS ***
is irrelevant because its sole purpose is to comply with a decades-long
accretion of unnecessary layering in various RFCs.

So when RADIUS is used this way there's nothing to "fix", since the bit that
matters is already being run inside a TLS tunnel.  It's only when the layering
is:

UDP
RADIUS

that there's something that needs fixing.

Peter.