[ietf-dkim] Issue 1576: Revise wildcard discussion

[Stephen Farrell]

Can I ask those who think that the current text is not sufficient
to please suggest alternative text?

Thanks,
S.

PS: Eliot - since this one has attracted discussion, it should not
be closed by default on July 11.


John Levine wrote:
>>>      A simple "MUST start with 'dkim='" (or similar) could fix it.
>> But to what end?  In what circumstance would a wildcard that stops at an 
>> existing label be at all useful?  This is where I have been bashing my head.
> 
> Let's pretend that we want to try to tell the world that we don't send
> mail from all the subdomains we don't send mail from:
> 
> *.foo.com. mx 0 .  	                ; MX says no mail
> *.foo.com. txt "v=spf1 -all"            ; SPF says no mail
> *.foo.com. txt "spf2.0/mfrom,pra -all"  ; Sender ID says no mail
> *.foo.com. txt "dkim=discardable"       ; ADSP says no mail
> 
> So you can look up the MX or TXT for plugh.foo.com and get answers,
> and you can also look up _adsp._domainkey.plugh.foo.com, only you get
> the same answers.
> 
> Plan A: forget that silly prefixed name stuff and add yet another
> magic string to tell our records apart from the other umpteen strings
> that will soon overflow our 512 byte buffer.
> 
> Plan B: note that DNS wildcards, once again, don't do what you want
> particularly when prefixed names are involved.  This issue is not
> unique to ADSP and affects DKIM keys as well.
> 
> I believe we chose Plan B.
> 
> R's,
> John
> 
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