Julian Mehnle wrote:
I don't quite see yet how the conflict with Sender ID's
v=spf1/PRA abuse could be resolved.
We specify a IANA registry of SPF tags + modifiers + options
like this:
Record tag Specification, applicability, (status)
v=spf1 4408
spf2.0/mfrom 4406, same as v=spf1 (DEPRECATED)
spf2.0/mfrom,pra 4406, same as v=spf1 + spf2.0/pra (DEPRECATED)
spf2.0/pra,mfrom 4406, same as spf2.0/mfrom,pra (DEPRECATED)
spf2.0/pra 4406
Modifier Specification, applicability, (status)
redirect= 4408, used for v=spf1 and spf2.0/pra
exp= 4408, used for v=spf1 and spf2.0/pra
op= NNNN, used for v=spf1 and spf2.0/pra
Option Specification, applicability, (status)
op=pra (eliminated by what I'm talking about)
op=auth NNNN, used for v=spf1
op=strict NNNN, if Scott still wants it for SSP ;-)
This proposal will explain why mixing v=spf1 and spf2.0/pra
cannot work in practice: A v=spf1 implementation doesn't
necessarily know what spf2.0/mfrom (etc.) is, and vice versa
an spf2.0/pra implementation won't care about obscure op=pra
drafts.
It will also explain that v=spf1 and spf2.0/pra are rather
different, and that spf2.0/pra support is poor because PRA
inherits all v=spf1 issues adding its own PRA issues while
losing the very desirable v=spf1 PASS advantage.
It will be clear (between the lines) that PRA might turn out
to be hopeless for now, it will be also clear that spf2.0/pra
and v=spf1 are disjunct: "Updates 4408" and "updates 4406".
As for amendments to RFC 4408, I'm extremely sceptical of
changing any semantics of the spec. Maybe we can clean the
document up and apply the handful of errata[1] that we have
collected.
And elaborate on the "DDoS" SHOULD in some way, e.g. picking
your proposal in the "rebuttal", and/or add a recommendation
to use at most one mx-mechanism per record, and to be very
paranoid about evaluating more mx-mechanisms per record.
Plus a few other details, quoted strings in local part etc.
Frank
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