Re: [TLS] renegotiation draft needs clarification !!

Wan-Teh Chang <wtc@google.com> Thu, 12 November 2009 01:48 UTC

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Date: Wed, 11 Nov 2009 17:48:26 -0800
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From: Wan-Teh Chang <wtc@google.com>
To: Nelson B Bolyard <nelson@bolyard.me>
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Cc: Eric Rescorla <ekr@rtfm.com>, tls@ietf.org
Subject: Re: [TLS] renegotiation draft needs clarification !!
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On Wed, Nov 11, 2009 at 5:29 PM, Nelson B Bolyard <nelson@bolyard.me> wrote:
> At least Two implementers have read the draft differently and implemented
> non-interoperable implementations.  The draft needs clarification.
>
> First the draft says:
>
>   The "extension data" field of this extension contains a
>   "Renegotiation_Info" structure:
>
>             struct {
>               opaque renegotiated_connection<0..255>;
>             } Renegotiation_Info;
>
> Then it says:
>
>   The contents of this extension are specified as follows.
>
>   o  If this is the initial handshake for a connection, then this field
>      is of zero length in both the ClientHello and the ServerHello.
>
> One implementer interprets this to mean that the extension data field
> is of zero length.  Another interprets it to mean that the
> "renegotiated_connection" field inside the Renegotiation_Info is to
> have zero length.  This leads to two different encodings, which are:
>
>  FF 01 00 00
>
>  FF 01 00 01 00
>
> I suggest replacing "the contents of this extension" with either
> "The contents of the renegotiated_connection", or
> "the contents of the extension data field", to make this sufficiently
> explicit.

This kind of ambiguity was also in the original RFC 4507 for
the TLS session ticket extension, and had to be addressed in
a new RFC 5077.  See RFC 5077 section 1 and appendix A.

Wan-Teh