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Re: [TLS] EncryptedExtensions message in [draft-ietf-tls-tls13-10]

Eric Rescorla <ekr@rtfm.com> Thu, 10 December 2015 17:56 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 10 Dec 2015 12:55:49 -0500
Message-ID: <CABcZeBOdbKEF-MDw3fVvA76nicS0g4OdSscdn-VjdCjAno+U5w@mail.gmail.com>
To: John Foley <foleyj@cisco.com>
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Subject: Re: [TLS] EncryptedExtensions message in [draft-ietf-tls-tls13-10]
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On Thu, Dec 10, 2015 at 12:40 PM, John Foley <foleyj@cisco.com> wrote:

> While reviewing the latest TLS 1.3 draft (revision 10), the description in
> section 6.3.3 uses the following wording:
>
> When this message will be sent:
>
>       If this message is sent, it MUST be sent immediately after the
>       ServerHello message.  This is the first message that is encrypted
>       under keys derived from ES.
>
>
> The use of the word "if" implies this is an optional message. However,
> Figure 1 in section 6.2 implies the EncryptedExtensions message is not
> optional since it's not footnoted with an asterisk. The asterisk footnote
> is described as:
>
> Indicates optional or situation-dependent messages that are not always
> sent.
>
>
> Can anyone comment on whether the EncryptedExtensions message is
> optional?  If it is, should Figure 1 be updated to reflect this? Or, should
> the the text in section 6.3.3 be updated to indicated this message is
> required?
>
> This is an important detail for implementors, since the client-side state
> machine will need to know whether to expect the EncryptedExtensions message
> after the ServerHello, or to expect another one of the subsequent messages.
>

Yes, I agree.

It is mandatory. Pilot error on my part.

-Ekr


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