Re: [Fwd: [Asrg] Re: Documents for LMAP BOF]

On Sun, Feb 08, 2004 at 03:31:10PM -0500, Yakov Shafranovich wrote:
> 
> Well actuall we have IP address of the MTA, HELO parameter used by the 
> MTA, and MAIL FROM/From headers used by the sender. So I am refering to 
> the MAIL FROM and "from" header information.


That's misleading. You don't "have" this information. 

What you have is the IP address. Everything else is not (yet)
verified, so you don't "have" this information. 


For sake of security engineering keep those informations 
that are already verified and reliable distinct from those 
which are only claimed by the caller and yet are to be 
verified. Once the LMAP query succeeded, then you 
"have" this information. Avoid ambiguous or misleading language.

Use different wording for what is verified and what is not verified.






> Isn't the HELO name unique to the MTA as opposed for the MAIL FROM 
> address which is unique to the sender? It is feasible that an MTA might 
> want to do multiple mail transaction in one SMTP connection using one 
> HELO identifier.

As far as I know the helo name can be anything. 
Of course the MTA can do multiple transaction in one connection. 
But I don't see what you want to say.



However, there is a point of view from which it doesn't make any
difference whether to use HELO, FROM, or any header line:

If we just require that any domain is taking responsibility
for the message transfer and we just require that this domain 
name is mentioned just *anywhere* within the transfer process, 
no matter whether where (reply-to, sender,...), then these
different approaches all melt into one.


We just force the sender to print it's domain name *anywhere* in the 
transmission process. All those proposals about envelope senders, 
HELO names, headers are just dancing around the little question, 
where RFC821/822 leave place to print a domain name in without further
meaning.

That's it. Very simple story. Just force the sender to reveal who he is 
(=print the name of the domain he's belonging to).


In principle, you could write the helo name, the envelope sender and 
every header entry containing a domain name in a list and verify one 
after another. Once you found an entry with positive LMAP reply
-> Bingo, you've got it. Irrelevant what entry type it was.
Only disadvantage is that it takes many DNS queries. 

All those proposals who try to be different from other proposals in 
using different "information" are actually not really different. 
It's just not understanding the problem.

But I'd prefer to stick at the envelope sender where possible. Because
this is the only entry which has a real meaning.

regards
Hadmut