Re: [TLS] Suspicious behaviour of TLS server implementations

"Andreas Walz" <andreas.walz@hs-offenburg.de> Wed, 21 September 2016 09:45 UTC

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Date: Wed, 21 Sep 2016 11:45:15 +0200
From: "Andreas Walz" <andreas.walz@hs-offenburg.de>
To: <martin.thomson@gmail.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] Suspicious behaviour of TLS server implementations
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Ok, thanks. This is close to my sense of it. Actually, I wasn't aware of the fact that
 the TLS 1.3 draft now  explicitly addresses this in the Presentation Language section:

     "Peers which receive a message which cannot be parsed according to the syntax
     (e.g., have a length extending beyond the message boundary or contain an
     out-of-range
length) MUST terminate the connection with a "decoding_error" alert."

Cheers,
Andi


>>> Martin Thomson <martin.thomson@gmail.com>; 09/21/16 9:25 AM >>>
On 21 September 2016 at 17:21, Andreas Walz
<andreas.walz@hs-offenburg.de>; wrote:
> Do you see any argument why ignoring such trailing data would be acceptable
> (or even desirable)?

No.

Well, we exploited that to add extensions to the protocol once, so I
won't categorically rule it out, but in the case of
supported_groups/supported_curves, no good can come of ignoring
rubbish.  Of course, it's hard to point to this being harmful as well
:)