ietf-mxcomp
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Re: Unified SPF: scope macro to distinguish identities

2004-06-24 07:26:54

On Thu, Jun 24, 2004 at 06:57:50AM -0700, william(at)elan.net wrote:
| 
| For technical comment, I think it would be good if SPF had scope modifier 
| where it could be set which identity (or more then one if necessary) is 
| this record for. For example:
| 
| v=spf1 id:mailfrom { ip4:192.168.0.1/16 } id:submitter { ip4:192.168.0.20/24 }
| v=spf1 id:mailfrom+submitter ip4:192.168.0.1/16 id:ehlo mx id:all -all
| 
| This may possibly be as an operator that changes scope of the identity for 
| record that follows to only cover certain specified identity type, if what 
| is being verified is of different identity type, that data is ignored
| until another modifier is found that changes the scope back to either all 
| or identity type that is wanted.

A macro to represent scope is probably cleaner than a scope modifier.

I want to state up front my assumption that most publishers
will never need to distinguish between scopes: most domains
should be able to simply set-join all the four scopes into a
single record, and apply local policy from there.

That is to say, if the policy for HELO names is

  v=spf1 A -all

and the policy for PRA names, if different, is

  v=spf1 B -all

the joint policy can be

  v=spf1 A B -all

However, if it really is important to distinguish the two,

            domain.com   v=spf1 redirect=%{scope}._spf.%{d}

  helo._spf.domain.com   v=spf1 A -all
   pra._spf.domain.com   v=spf1 B -all

This solution provides the desired functionality of "which
identity?"  scoping.

In practice the %{scope} would really be a single character
not chosen yet.