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

From: John Foley <[email-masked]>
Date: Thu, 10 Dec 2015 12:40:48 -0500

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.

---

From: Eric Rescorla <[email-masked]>
Date: Thu, 10 Dec 2015 12:55:49 -0500

On Thu, Dec 10, 2015 at 12:40 PM, John Foley <[email-masked]> wrote:

> While reviewing the latest TLS 1.3 draft (revision 10), the description in
> section 6.3.3 uses the following wording:
>
> optional since it's not footnoted with an asterisk. The asterisk footnote
> is described as:
>
> 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

> _______________________________________________
> TLS mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/tls
>

---

From: Eric Rescorla <[email-masked]>
Date: Thu, 10 Dec 2015 12:56:22 -0500

https://github.com/tlswg/tls13-spec/issues/362 so this doesn't get lost.

---

From: John Foley <[email-masked]>
Date: Thu, 10 Dec 2015 13:06:34 -0500

On 12/10/2015 12:55 PM, Eric Rescorla wrote:
>
>
> On Thu, Dec 10, 2015 at 12:40 PM, John Foley <[email-masked] 
> <mailto:[email-masked]>> wrote:
>
>     While reviewing the latest TLS 1.3 draft (revision 10), the
>     description in section 6.3.3 uses the following wording:
>
>     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:
>
>     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.
>
Thanks for clarifying this.  I appreciate the prompt response.
>     [email-masked] <mailto:[email-masked]>