Subject: Re: [TLS] Confirming Consensus: Negotiating upper layer protocols

From: Peter Gutmann <[email-masked]>
Date: Fri, 8 Feb 2013 12:47:09 +0000

Yoav Nir <[email-masked]> writes:
>On Feb 8, 2013, at 12:51 PM, Peter Gutmann <pgut001 at cs.auckland.ac.nz> wrote:
>> Eric Rescorla <ekr at rtfm.com> writes:
>> 
>>> WG members, please provide any comments on whether we should take this work
>>> on by February 21. Additionally, if you wish to propose an alternative, it
>>> would be nice if you could do so soon or at least provide an indication of
>>> interest.
>> 
>> A comment on both of these proposals, to encode their protocols they use an
>> ad-hoc, non-TLS-style encoding whose form is rather unclear:
>> 
>>  Protocols are named by IANA registered, opaque, non-empty byte strings and
>>  the list of protocols is serialized as a concatenation of 8-bit, length
>>  prefixed byte strings.
>> 
>> Does this mean the strings use 8-bit chars, the lengths are 8 bit, both, or
>> neither?  What's wrong with:
>
>I agree that it's not clean, but I took it to mean ...serialized as a
>concatenation of (((8-bit length) prefixed) byte strings)

Yeah, I'd sorta guessed that, but I'd really prefer it if they used the
standard TLS format for things.  At the moment I have to drop use of standard
TLS PDU parsing and switch to an ad-hoc custom-written parser for that one
data blob, I can't see any good reason to use the nonstandard format when
everything else in TLS uses the standard one.

Peter.

---

From: Adam Langley <[email-masked]>
Date: Fri, 8 Feb 2013 08:23:20 -0500

> everything else in TLS uses the standard one.

The difference between the wording and using the TLS presentation
format is the addition of an extra length prefix. Since the extension
already has a length, it's a little sad that using the presentation
format requires adding another one - it's not as if these structures
are ever extended with extra, optional fields.

None the less, in the interests of being uniform, maybe we should have
another length.

Cheers

AGL