Re: Random data

[Tom Yu <[e-mail]>]

"Frank Ellermann" <[e-mail]> writes:

> Tom Yu wrote:
>
>>> The right hand side of a challenge in "Message-ID format"
>>> can be twisted into what I expect by an attacker, it's no
>>> security feature.
>  
>> Might this have been an aborted attempt at specifying how
>> to use the challenge to transmit additional information to
>> a server, such as channel binding information?  Or am I
>> thinking of DIGEST?
>
> I'd guess that RFC 2195 uses the format of a Message-ID for
> a challenge, because that's what APOP also uses, and a known
> (for mail and news related protocols) concept.

I meant that the introduction in draft-ietf-sasl-crammd5 of a new
requirement that an implementation not interpret the "string that
RFC2195 required to look like a RFC822 msg-id" might have been an
aborted attempt to provide a "covert channel" for signaling the use of
a channel binding.

Alternatively, the new requirement that the client not interpret the
challenge string might be an effort to improve interoperability with
servers that do not send challenge strings that strictly conform to
the syntax of RFC822 or RFC2822 msg-id strings.

Authors or others, please elaborate if you recall the history of this
change.