(RADIATOR) Possible to Proxy PEAP-EAP-MSCHAP v2 to IAS?

[Mike McCauley]

Hello Jon,


On Mon, 9 Feb 2004 07:09 pm, Jon Snyder wrote:
> Hi all,
>
> We're trying to configure EAP for 802.1x wireless authentication with the
> general rule that Radiator will authenticate everything it can locally, and
> proxy the authentication types it can't.  Our Radiator instance is running
> on Solaris with passwords in NIS, so we can't for example authenticate
> MS-CHAP v2 requests.
>
> What I would like to do is proxy PEAP-EAP-MSCHAP v2 (from the Windows XP
> SP1 PEAP client) to an IAS server running on Windows 2003, which can
> authenticate the MS-CHAP v2 request.  But, if the request is TTLS with PAP
> or some other form that can be authenticated locally on the unix host, do
> so there.  The problem I think I'm running into is that Radiator is
> properly proxying the inner EAP-MSCHAP v2 on to the IAS server, but IAS
> can't handle EAP-MSCHAP v2 as it receives it; it wants either PEAP with
> MSCHAP v2 inside, or a regular MSCHAP v2 challenge in the radius packet (no
> EAP).

Its true that IAS cannot handle bare EAP-MSCHAPV2, only when it is tunnelled 
inside PEAP, so you would have to forward the entire PEAP conversation to the 
IAS server.

The problem is that is is not possible to distinguish between EAP types when 
trying to figure out where to proxy something. Mainly this is beacause the 
EAP type is not negotated until several packets have been exchanged, so you 
have a chicken-egg problem when trying to figure out where to send the 
requests. The uphot is that you need some other cue when trying to determnine 
where to send requests. Most commonly this is the realm in the users name, of 
course.


>
> Is it possible to accomplish what I'm trying to do?  It seems like if I
> could "extract" the MSCHAP v2 and send it over to IAS without it being
> EAP-MSCHAP v2 it might work.  I know it's possible with TTLS to have one
> server take the EAP-TTLS requests, and proxy the actual authentication to
> another server that knows nothing about EAP (as demonstrated in the goodies
> configs).  Can the same be done with PEAP?

I think it might be technically possible for an EAP-MSCHAPV2 authenticator to 
turn the requests into plain RADIUS-MSCHAPV2 and then forward them. However 
it would require some new code and we dont see muchg demand for this feature 
(yet).


>
> I have this working if I use an AuthBy FILE for handling the inner
> authentication, so I know it's not a general issue with my system or
> configuration for PEAP.  But with the AuthBy RADIUS below, no go.

This config would prob work if only IAS could understand EAP-MSCHAPV2 outside 
a PEAP tunnel. 

Actually Radiator understands bare EAP-MSCHAPV2 and when it runs on Windows, 
it can be configured to authenticate EAP-MSCHAPV2 against AD, LSA etc.

MAybe the right answer is to run your Radiator on Windows and configure to 
auth the inner EAP-MSCHAPV2 with AuthBy LSA?

Cheers.


>
> Thanks in advance!
>
> Here's what I'm doing in the Radiator config (this isn't the whole config,
> but should be all the relevant portions):
>
> <Handler TunnelledByPEAP=1,EAPType=MSCHAP-V2>
>         <Log FILE>
>                 Filename %L/PEAPInside.log
>                 Trace 4
>         </Log>
>
>        <AuthBy RADIUS>
>                NoDefault
>                EAPType MSCHAP-V2
>                <Host win2k3.ias.box>
>                        Secret secret
>                        AuthPort 1812
>                        AcctPort 1813
>                </Host>
>        </AuthBy>
> </Handler>
>
> <Handler TunnelledByPEAP=1>
>         <AuthBy SYSTEM>
>                 NoDefault
>         </AuthBy>
> </Handler>
>
> <Handler TunnelledByTTLS=1>
>         <AuthBy SYSTEM>
>                 NoDefault
>         </AuthBy>
> </Handler>
>
> <Handler Client-Identifier=wiAPs>
>         <Log FILE>
>                 Filename %L/PEAPOutside.log
>         </Log>
>         <AuthBy FILE>
>                 Filename %D/users
>                 EAPType PEAP,TTLS
>
>                 EAPTLS_CAFile %D/certificates/thawte/ThawteServerCA.txt
>                 EAPTLS_CertificateFile
> %D/certificates/radius-server.cert.pem
>                 EAPTLS_CertificateType PEM
>                 EAPTLS_PrivateKeyFile %D/certificates/radius-server.key.pem
>                 EAPTLS_PrivateKeyPassword whatever
>                 EAPTLS_MaxFragmentSize 1000
>
>                 AutoMPPEKeys
>         </AuthBy>
> </Handler>
>
> ----------
> Jon Snyder
> Computing & Network Services
> Portland State University
>
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-- 
Mike McCauley                               mikem at open.com.au
Open System Consultants Pty. Ltd            Unix, Perl, Motif, C++, WWW
9 Bulbul Place Currumbin Waters QLD 4223 Australia   http://www.open.com.au
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