Re: Updated RSA SHA-2 draft / New draft: SSH Extension Negotiation

[Jeffrey Hutzelman <jhutz%cmu.edu@localhost>]

On November 13, 2015 9:39:23 AM EST, denis bider <ietf-ssh3%denisbider.com@localhost> wrote:
>Much agreed.
>
>If the IETF will accept an erratum with a clarification, here's a
>proposed wording:
>
>
>"Servers and clients may or may not be aware of a future extension to
>this RFC that specifies a use for the KEXINIT reserved field.
>
>Servers and clients that are NOT aware of such an extension:
>- MUST send the reserved field with the value zero (indicating
>unawareness);
>- MUST NOT act on any value of this field when received, whether zero
>or non-zero;
>- in key exchange, MUST properly hash the actual received value of this
>field.
>
>This behavior is REQUIRED to allow use of this field in future protocol
>extension."

It certainly was a mistake not to specify this to begin with.  However, this represents a change to the protocol, not correction of a technical inaccuracy in the document.  Nor is it a change to reflect common, consistent actual practice which differs from the specified protocol.  So, I don't think it's appropriate for an erratum.  Further, it's too late: this behavior is only useful if older implementations follow it; you can't add extensibility after the fact.

-- Jeff