Re: [TLS] RFC8446 Fig3

"Martin Thomson" <mt@lowentropy.net> Fri, 03 May 2019 00:47 UTC

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Date: Thu, 02 May 2019 20:47:21 -0400
From: "Martin Thomson" <mt@lowentropy.net>
To: tls@ietf.org
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Subject: Re: [TLS] RFC8446 Fig3
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That's right.  You might open an editorial erratum, which I would suggest be held for document update.

Note that there is no promise that the list of extensions is complete, as this doesn't show the supported_versions or signature_schemes extension either, but the omission is probably not great in this case, since the PSK modes  are highly relevant.

On Fri, May 3, 2019, at 10:30, Daniel Migault wrote:
> Hi, 
> 
> This might have already been mentioned on the list, but unless I 
> misinterpreter something it seems to me that the second handshake of 
> figure 3 is missing psk_key_exchange_modes extension. 
> 
> Yours, 
> Daniel
> 
>  Figure 3 shows a pair of handshakes in which the first handshake
>  establishes a PSK and the second handshake uses it:
>  Client Server
>  Initial Handshake:
>  ClientHello
>  + key_share -------->
>  ServerHello
>  + key_share
>  {EncryptedExtensions}
>  {CertificateRequest*}
>  {Certificate*}
>  {CertificateVerify*}
>  {Finished}
>  <-------- [Application Data*]
>  {Certificate*}
>  {CertificateVerify*}
>  {Finished} -------->
>  <-------- [NewSessionTicket]
>  [Application Data] <-------> [Application Data]
>  Subsequent Handshake:
>  ClientHello
>  + key_share*
>  + pre_shared_key -------->
>  ServerHello
>  + pre_shared_key
>  + key_share*
>  {EncryptedExtensions}
>  {Finished}
>  <-------- [Application Data*]
>  {Finished} -------->
>  [Application Data] <-------> [Application Data]
>  Figure 3: Message Flow for Resumption and PSK
> 
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