[ietf-dkim] [dkim-ops] key validation question
hsantos at isdg.net
Tue Apr 12 00:56:44 PDT 2011
> Adding text in RFCs to prevent lies doesn't usually solve problems. :-)
Sure, but that is what h= attempts to trap using another level of
authenticity requirements. We can categorized that scenario many ways
but its simply about the domain trying to exclude an method a "bad
guy" can use fraudulently.
>> Overall, my suggestion for the text would be something like:
>> h= A colon-separated list of hash algorithms that might be used
>> as acceptable hash algorithms. (plain-text; OPTIONAL,
>> defaults to allowing only standard registered algorithms).
>> When signing mail, the signer MUST use one of the h= methods
>> explicitly specified or implicitly using one the default
>> standard registered hash algorithms.
>> Verifiers not recognizing a hash algorithm or does not
>> match a= value MUST invalidate the signature.
> The key in the text proposed earlier is "operational choice" (see what
> Tony suggested). It is a fix that does not introduce any requirements.
> The text proposed earlier takes into account what is stated in other
> sections of draft-ietf-dkim-rfc4871bis-05.
The point in my text is to spell it out. Yes, its an operational
choice, but one that does come with a non-written technical
requirement. If you specified h=, you are expected to use one of the
methods listed for signing. Otherwise, current verifiers will see you
as a "liar" (or bad guy mail) when using something else. :)
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