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Re: [TLS] Finished verify_data collision (Was Re: draft-turner-ssl-must-not)

Nikos Mavrogiannopoulos <nmav@gnutls.org> Thu, 08 July 2010 08:07 UTC

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From: Nikos Mavrogiannopoulos <nmav@gnutls.org>
To: Marsh Ray <marsh@extendedsubset.com>
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Cc: Simon Josefsson <simon@josefsson.org>, "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Finished verify_data collision (Was Re: draft-turner-ssl-must-not)
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[...]
> * Mitm needs to obtain the client's premaster secret as part of the attack
> (the key material is needed to generate the hash). Note this is trivial with
> some real clients in common use that don't validate the server cert until
> they receive the Finished message.

Why is this trivial? If you do mitm it will be discovered at the
verification point and game is over.

regards,
Nikos

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