ietf-dkim
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Re: [ietf-dkim] wildcards, was Focusing on 4871bis

2010-10-25 16:03:30
John,

The reported issue was about *mixed* TXT usage caused by wildcards. 
And it amounted to a large Domain Hosting vendor ONLY offering this 
for spf:

   *.example.com  IN TXT "v=spf1 .........."

And that created mixed query results after adding DKIM related TXT 
records.

The proposed correction text is a) reminder to avoid using them and b) 
for verifiers to be ready to deal with it. i.e. be able to parse for 
the right DKIM related text string.

-- 
HLS

John R. Levine wrote:
Forgive me if I repeat myself, but I still don't see anything wrong 
with this:

*._domainkey.example.com  IN TXT "v=DKIM1; p=; n=revoked"

Do you have an actual use case for that sort of thing, or is it just 
an example to poke at the "thou shalt not wildcard" wording?

That example above revokes all unknown keys.

On this message, I've encoded a timestamp and the pid into the DKIM 
signature selector, so I can use my DNS query logs to get an idea of 
who's checking the signatures on what messages.

These may not be fabulous uses of wildcards, but they are at worst 
harmless.  There's a lot of places in the DKIM spec where we say if you 
do so-and-so, you'll be sorry.  I'd like to avoid saying that unless we 
have a good reason to do so, and I only see problems with wildcards 
above the _domainkey label.

Regards,
John Levine, johnl(_at_)iecc(_dot_)com, Primary Perpetrator of "The Internet 
for 
Dummies",
Please consider the environment before reading this e-mail. http://jl.ly


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