questions about a custom freeradius configuration

Jeff Smith jsmith at
Wed Jul 27 20:12:58 CEST 2005


Our wireless network currently authenticates and authorizes users via 
freeradius 0.8.1 with a custom module that talks to custom 
authentication and authorization servers.

I'm upgrading the server side to freeradius 1.0.4.  At the same time, 
the people who run the wireless network are switching to using EAP-PEAP 
with MS-CHAP v2.

I'm fairly new to freeradius, but I have been spending a lot of time 
reading this list, the documents, the O'Reilly book, and experimenting 
with the server.  So far I've been able to do PEAP authentications to 
the server via the users file.

The custom authentication module I referred to in the first paragraph 
basically re-implemented MS-CHAP v2 and talked to the custom servers on 
the back end.  It would not be easy to wedge into the rlm_eap code. 
Instead, I'd like to find a solution that makes the fewest possible (if 
any) modifications to stock freeradius, so we can track releases more 
closely. I would like to continue using the custom authentication and 
authorization servers.

My thinking on this so far is that I might be able to use the 
Exec-Program-Wait atribute and/or the rlm_perl modules to call out to 
the custom servers, which have command-line interfaces.  Ideally, I'd be 
able to do something like this:

1) In the authorization phase, call out to the custom authorization 
server and ask a question like "Is this user who claims to be ``joe'' 
authorized to use the wireless service?"  I can get back a yes/no answer 
and send an Access-Reject with an explanation, or continue on if they 
are authorized.  (I don't think Exec-Program-Wait can help here since I 
understand it only gets called after the user is authenticated.  I could 
make this check after and only if mschap returns success, though.)

2) In the authorization phase, also call out to the custom 
authentication server to get pack the NT-Password and add that to the 
value pairs in the check list in the request packet, so that when 
EAP-PEAP finally gets down to the MS-CHAP v2 part, the NT-password is 

I have been having a hard time getting my mind around the complexity of 
RADIUS and freeradius.  It may be that I'm taking a completely 
wrong-headed approach here.  If anyone on this list has any thoughts on 
how this could be done best, I'd appreciate  hearing your ideas.

Thanks in advance!

Jeff Smith
Security Analyst - ITaP Identity & Access Management
Purdue University
W. Lafayette IN 47907-1408
Phone: 765-496-8285

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