RE: Does marid-submitter-02 really make sense?

["Harry Katz" <hkatz@xxxxxxxxxxxxxxxxxxxxxx>]

On Monday, August 09, 2004 4:49 PM Shevek wrote:

> On Mon, 9 Aug 2004, Harry Katz wrote:
> 
> > On Monday, August 09, 2004 10:24 AM ned.freed@xxxxxxxxxxx wrote:
> > 
> > > First, I am not proposing anything here. Not only is 
> SUBMITTER not 
> > > my idea, I have been quite clear that I am ambivalent about its 
> > > inclusion in MARID.
> > > 
> > > Second, the optimization in case 1 isn't a failure case but a 
> > > success case.
> > > There may be a throughput improvement in some MTAs if the 
> check can 
> > > be done sooner. Mind you, I'm not saying there is 
> guaranteed to be 
> > > such an improvement
> > > - just that it is a possibility. Actual implementation experience 
> > > would be needed to tell for sure.
> > 
> > Ned is exactly correct here.  The purpose of SUBMITTER is to allow 
> > early (i.e. at 2821-time) verification of the sender's identity, 
> > namely the PRA.  At the IETF meetings last week there was some 
> > discussion of whether this would result in bandwidth saving, 
> > throughput improvement, or no benefit at all.  I tend to 
> think there 
> > will be modest throughput improvement, but agree with Ned 
> that we need to verify through testing.
> 
> This is incorrect. At 2821 time, we know only who the sender 
> CLAIMS to be via SUBMITTER. It's not until after 2822 time, 
> when we can compare the SUBMITTER value to the PRA value 
> computed from the 2822 headers that we have verified the 
> identity of the sender.

Actually, it is correct.  From section 4.2 of the submitter-02 draft:

   If these tests indicate that the connecting SMTP client is not
   authorized to transmit e-mail messages on behalf of the SUBMITTER
   domain, the receiving SMTP server SHOULD reject the message and when
   rejecting MUST use "550 5.7.1 Submitter not allowed."

   If the receiving SMTP server allows the connecting SMTP client to
   transmit message data, then the server SHOULD determine the purported
   responsible address of the message by examining the RFC 2822 message
   headers as described in [SENDER-ID].  If this purported responsible
   address does not match the address appearing in the SUBMITTER
   parameter, the receiving SMTP server SHOULD reject the message and
   when rejecting MUST use "550 5.7.1 Submitter does not match header."

In other words, if SUBMITTER is present and fails the Sender ID check at
2821 time, then the message SHOULD be rejected.  The subsequent matching
of SUBMITTER to 2822 headers is only to confirm - if DATA is accepted -
that the SMTP client didn't lie about the value.