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List:       freeradius-users
Subject:    Re: "Outer and inner identities are the same"
From:       Alan DeKok <aland () deployingradius ! com>
Date:       2019-10-21 22:42:09
Message-ID: 39CC0252-9283-4B53-92FA-FF6476AD6E4C () deployingradius ! com
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On Oct 21, 2019, at 6:23 PM, Gregory Sloop <gregs@sloop.net> wrote:
> 
> I have a EAP-MSCAPv2 WPA-Enterprise setup working so that's good.

  As a nitpick, it's not doing EAP-MSCHAPv2.  It's probably doing PEAP.  Which is an \
outer TLS session, followed by EAP-MSCHAPv2 as application data inside of the TLS \
tunnel.

  This is largely similar to HTTPS in some ways.  There's a TLS session setup for \
security, and then actual data (HTTP) inside of the TLS session.

> I get warnings about "Outer and inner identities are the same," however.
> Searching the list doesn't do a lot to illuminate me as to exactly what the inner \
> and outer tunnels are.

  sites-enabled/inner-tunnel is the virtual server which handles the inner-tunnel \
authentication.  It has some comments describing what's going on.

> I think I understand this warning - though some explanation would be handy.
> 
> I assume, given the message, that the User identity is available outside the \
> MS-CHAP/MPPE "envelope" - in the "outer" tunnel.

  MS-CHAP doesn't have inner tunnel.  It's largely just a two-way handshake of \
hash(password).  And the MPPE keys are sent in the Access-Accept, and are unrelated \
to identities or tunnels.

> But, if we're using a CA/server-cert+key, the user identity should be encrypted \
> inside the "outer" tunnel too, right? To say that another way - the outer tunnel is \
> protected via the server-cert+key, and the inner tunnel is protected by the \
> chapv2/mppe protocol. Do I have that right?

  Not really.  Read the debug output to see what's going on.  You will see:

* outer identity is User-Name, and is in the clear
* at some point, it goes "TLS session established"
* followed by running sites-enabled/inner-tunnel
* which then does EAP-MSCHAPv2
* and which in turn has an inner identity

> In this case, the MPPE tunnel is far less secure [provided modern encryption \
> standards] than say a AES-256/SHA-256 RSA outer tunnel, and I shouldn't need to \
> worry about the warning.

  The warning is there for a reason.

  The point is that the outer identity is entirely in the clear.  Anyone can see it.  \
It's sent in the clear over WiFi.  If you want privacy, you should use an anonymous \
outer identity (e.g. @example.com), and then use your "real" identity inside of the \
TLS tunnel.  Which, of course, is encrypted via all of the normal TLS magic.  So no \
one can snoop on it.

  There's a standard for this, of course.  RFC 7542.  Written by your friendly \
neighbourhood RADIUS guy.

> If there's a doc somewhere that covers this, I'd be happy to read it, but I haven't \
> seen one - or been able to find one by searching.

  Wikipedia has a good page on PEAP.  It covers a lot of these subjects at a high \
level.

> Lets deal with that first, and then once I understand it well enough, I may have \
> follow-on questions.

  That's a very good approach.

  Alan DeKok.


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