Re: [TLS] Inter-protocol attacks

mrex@sap.com (Martin Rex) Fri, 15 August 2014 01:57 UTC

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To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Date: Fri, 15 Aug 2014 03:56:30 +0200 (CEST)
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From: mrex@sap.com (Martin Rex)
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Cc: Antoine Delignat-Lavaud <antoine@delignat-lavaud.fr>, "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Inter-protocol attacks
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Ilari Liusvaara wrote:
>> 
>> But with your description I somehow still fail to see a problem.
>> If the server certificate of such resumptions will *pass* the
>> "server endpoint identification", then why would re-doing the
>> server endpoint identification make a difference?
> 
> As far as I understand, the actual issue is HTTP servers issuing
> false responses to HTTP reqeusts if sent to wrong server (but
> that server may still have valid certificate). And clients
> interpretting those false responses as proper ones then leads
> to all sorts of unpleasant problems.

I did understand that part.


> 
> Where session resumption comes in is that it is more vulernable
> than full handshake to attacker interference, resulting in it
> being easier to make user connect to wrong server.

But I still fail to see how session resumption would aggravate
any bogosities performed by applications as long as the servers
certificates on both handshakes (resumption an full)
will properly *PASS* the usual server endpoint identification checks,
which is what has been asserted.

-Martin