In this case, definitely that's fine. Can you point out where in the spec it
mentions opaque data encoding a length? I even looked for that in the TLS
style syntax description again, since everything I was worried about in the
draft made since if that was the case, but couldn't find it.

I think we may have the very minor bug of needing to make the fact the
length is encoded a bit more clear in the draft (or I'm just blind), but
given this, my bigger concern is a non-issue. Thanks, that clears it up.

David (as individual)

On Jul 8, 2010 4:11 PM, "Cullen Jennings" <[email protected]> wrote:


Agree with what you are getting at here but I think the draft is already
pretty much what you want and this is just a syntax confusion.

When the spec has a typedef like

    typedef opaque       ResourceId<0..2^8-1>;

This results in bits on the wire that look like an 8 bit integer as the
length followed by that many byes of data. So any time we have a variably
length element generated by the < > operators, it includes the length as
well as the data.

So with that in mind, looking at section 5.3.3, the

  MessageExtensions      extensions<0..2^32-1>;

will contain the length all *all* the extensions if a parser just wanted to
skip over them all. If it did not skip them all, the

 opaque                extension_contents<0..2^32-1>;

will start with the length of the extension data so the parser can skip over
an extenuation it does not understand.

So given all that, does draft look reasonable. I completely agree an peer
needs to be able to know the length of an unknown extortion to be able to
step over it in parsing so if we can't do that, we need to fix it.




On Jul 8, 2010, at 8:58 AM, David A. Bryan wrote:

> So looking at the extension mechanism in 5.3...
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Cullen Jennings
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