eap Mailing List: RE: Re: Confidentiality of TLS keying information for wireless

[Frank Akujobi (fakujobi]

Aboba,
Thanks for your response. I understand how TLS provides mutual
authentication and key exchange. I also understand that data frames sent
after the key negotiations are encrypted and from that stand point a
man-in-the-middle attack can be prevented.
However my question was directed towards the confidentiality of the
signaling process (more like the management frames NOT data frames)
between the client and server before session key and WEP keys are
generated. Is the signaling traffic itself encrypted? Pls find my
comments within:
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"Hi,
I have a couple of questions concerning wireless clients using EAP-TLS
authentication against a radius server:

1. Are all the TLS session negotiations between supplicant (on the
client) and authenticator (AP) sent in the clear? In other words is
there any form of confidentiality for TLS keying information?

2. If there is none, what prevents a potential attacker from listening
in on TLS sessions and eventually gathering enough information (like the
session key and eventually WEP keys) to launch a man-in-the-middle
attack?

Thanks
Frank

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-
As noted in Section 3 of [Rescorla], when server certificate
authentication is supported, the server sends its certificate to the
client in the Certificate message.  The client then responds with the
ClientKeyExchange message, in which it encrypts a randomly chosen
PreMasterSecret and encrypts it using the server's public key.  The
server
subsequently demonstrates receipt of the PreMasterSecret (and possession
of the private key corresponding to the public enclosed within its
certificate) by using it in the calculation of the Finished message.
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>From your comments about section 3, I would be concerned as to whether
the "Certificate message" sent from the server was encrypted and if so
with what key?
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As noted in Section 4 of [Rescorla] when the client authentication is
supported and certificates are used, client authentication is initiated
by
the server sending a CertificateRquest message to the client.  The
client
responds by sending a Certificate message to the server as well as a
CertificateVerify message, which is signed with the private key
associated
with the transmitted client certificate.  The client therefore
demonstrates possession of the private key corresponding to the public
key
enclosed within its certificate.
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Also from your comments about section 4, I would be concerned as to
whether the "Certificate message" for the client to server was
encrypted.
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Thanks
Frank.


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