Re: [Emu] EAP TLS 1.3 backward compatibility with RFC 5216

On Sun, Jun 13, 2021 at 2:44 PM Bernard Aboba <bernard.aboba@gmail.com>
wrote:

> draft-ietf-emu-eap-tls13-16 Section 2.1 contains the following text:
>
>    EAP-TLS 1.3 remains backwards compatible with EAP-TLS 1.2 [RFC5216] . TLS version
>    negotiation is handled by the TLS layer, and thus outside of the
>    scope of EAP-TLS.  Therefore so long as the underlying TLS
>    implementation correctly implements TLS version negotiation, EAP-TLS
>    will automatically leverage that capability.
>
>
> I am concerned that this statement is potentially misleading. An
> implementation of RFC 5216 that negotiates TLS 1.2 and utilizes the key
> hierarchy defined in RFC 5216 Section 2.3 will not interoperate with an
> implementation of draft-ietf-emu-tls13-16 that also negotiates TLS 1.2 and
> utilizes the key hierarchy defined in Section 2.3 of that document.
>
> So in what sense is EAP-TLS 1.3 "backwards compatible" with EAP-TLS 1.2?
>
> The only way this makes sense to me is if it is stated that
> draft-ietf-emu-eap-tls13 applies only when TLS 1.3 is negotiated, and that
> if TLS 1.2, 1.1 or 1.0 is negotiated, then RFC 5216 applies.
>
>
[Joe] Good point.  I think this is missing from the draft.  The EAP-TLS
implementation does need to know which version of TLS is negotiated.   I
agree that this draft applies to when TLS 1.3 is negotiated and not
previous versions of TLS.

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