On Wed, 2002-10-02 at 15:17, Lars Viklund wrote:
> On Wed, 2002-10-02 at 09:24, Pat Calhoun wrote:
> > > send the supplicant an EAPOL-Key message with an empty Key field, which
> > > means use the specified number of bits from the MS-MPPE-Send-Key as the
> > > key-mapping key.
> > 
> > check... unfortunately, this doesn't appear to work. 
> 
> Do you mean "not work" in the sense that Win XP doesn't accept such
> EAPOL-Key messages that you send to it?

well, XP isn't quite nice enough to actually *tell* me that it doesn't
like my EAPOL-Key message... but I know that manually decoding the
packets it sends using what I believe is the key (from the MPPE-Send-Key
attribute) fails the checksum process... so it's using something other
than what's in the MPPE-Send-Key (or perhaps a different set of bits
than I am).

> 
> > However, I found
> > going through the various revisions of the congdon draft that the
> > signature has changed over time, and this may be what's biting me. I
> > found that in -17 of the draft, the signature doesn't cover the EAPOL
> > header, while -20 it does. I suspect what's going on is that they are
> > trying to play catch up with the work in .1aa, but it would be really
> > nice if there were a draft that showed how 802.1X worked :(
> > 
> > Any ideas how XP behaves?
> 
> No, but I seem to remember that the Cisco 340 sends EAPOL-Key with an
> empty Key field (at least if 104-bit keys are used) and that this works
> with Win XP, so it should be possible to figure out the details.

Right. Sending a unicast key is really unnecessary (and in some cases
even not recommended). So sending an EAPOL-Key packet with the optional
key field absent is a message to the supplicant that it should use the
key it received during the TLS negotiation.

This is what I am trying to do, but XP doesn't seem happy. I suspect
that as I mentioned above, I need to find the exact congdon draft that
covers 802.1X expected behavior :(

PatC

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