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Re: [TLS] draft-ietf-tls-renegotiation-01.txt and DTLS

Marsh Ray <marsh@extendedsubset.com> Thu, 03 December 2009 20:02 UTC

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Date: Thu, 03 Dec 2009 14:01:32 -0600
From: Marsh Ray <marsh@extendedsubset.com>
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To: Tolga Acar <Tolga.Acar@microsoft.com>
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Cc: Kyle Hamilton <aerowolf@gmail.com>, "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] draft-ietf-tls-renegotiation-01.txt and DTLS
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Tolga Acar wrote:
> I looked at DTLS and it doesn't seem like it is vulnerable as TLS is.
>  The "uint16 epoch" and "uint48 sequence_number" in the record header
> are input to the MAC and are validated per RFC4347 Section 4.1.2.1.
> It seems to me that a MiTM would not have a  matching epoch+sequence
> number, the MiTM can't change them (ok, may change, but MAC would not
> validate), and it takes 2^48 for them to roll over.

Couldn't he possibly 'prep' the client by triggering the exchange of the
appropriate number of dummy records before splicing him into the server
connection?

Is there something about the DTLS sequence_number that makes it more
resilient than the TLS record sequence number?

- Marsh

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