ietf-dkim
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Re: [ietf-dkim] Everything not forbidden is permitted

2009-08-04 11:20:13
On 8/3/09 5:28 PM, hector wrote:
The near issue has already come up and the end-result - NO.  A
customer was asked by their direct marketing spammer to add DKIM/DKEY
records because YAHOO was forcing the issue on the spammer to access
YAHOO recipients.

They wanted to signed:

        coupons.majorcompany.com

and ask the company to add DNS selector records.  But the major
company did have a way to stop fake or 3rd party

        majorcompany.com
        dept.majorcompany.com
        services.majorcompany.com

signatures once bad guys learned that the domain was being signed!

Since DKIM lacks fault detection, the answer was no.

The g= tag within the key could limit the local-part of the i= value 
found in the signature header, but would not prevent the use of 
subdomains. This would mean that g=noreply would allow:

  noreply(_at_)coupons(_dot_)majorcompany(_dot_)com
  noreply(_at_)dept(_dot_)coupons(_dot_)majorcompany(_dot_)com
  noreply(_at_)services(_dot_)coupons(_dot_)majorcompany(_dot_)com

and even without the g= restriction the key would not allow:

  majorcompany.com
  dept.majorcompany.com
  services.majorcompany.com

-Doug
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