Subject: RE: [lemonade] Why are we keeping X-MMS headers?

From: "Vaudreuil, Greg M (Greg)" <[email-masked]>
Date: Fri, 24 Jun 2005 08:28:50 -0500

Mark,

You are arguing an extreme point.  You are effectively arguing that X- headers in general are bad, cause damage, and should be removed.  That may be perfectly true, but is a separate debate.  X-MMS headers are no more dangerous to the infrastructure than X-mailer and X-MS-priority.  Heck, by the time your message hit my UA, four X-headers were added.  When Randy sends messages, I seem to get a half-dozen or so X-headers.  It is hard to argue in the face of widespread use that these things are inherently useless or inherently dangerous.

For those X-headers who's insertion would cause harm, we need to write security considerations.  Fundamentally, I don't know why it is more harmful for a evil guy to add malicious X-headers than malicious regular headers.  If MMS has specific formatting, and getting it wrong would cause a problem, then the gateway should check before accepting... If a header indicates "A rely to this is free", it would be reasonable advise not to honor it unless you have other means to know it is trustworth.  This may even be a good case to suggest just dropping the reverse-charging header it since you can't trust anything sent over Internet email.  Good text for an implementation note or security consideration.

Greg V.

-----Original Message-----
From: Mark Crispin [mailto:[email-masked]]
Sent: Friday, June 24, 2005 2:48 AM
To: Eric Burger
Cc: [email-masked]
Subject: Re: [lemonade] Why are we keeping X-MMS headers?

On Fri, 24 Jun 2005, Eric Burger wrote:
> Are we keeping X-MMS headers because they are of use *ONLY* to a MMS MTA or
> MUA?  That is, do we want to tunnel the X-MMS header from MMS land through
> Internet land back to MMS land?

I don't think that you are asking the right question.  A better question 
is:

What harm is caused by requiring that all X-MMS headers be removed?  If 
there is no harm, then why haven't we required the removal of these 
headers?

> Conversely, do we want to enable an Internet MUA the ability to set a MMS
> header that gets appropriately translated into MMS land?  Do we want an
> Internet MUA or MTA to take special action based on a X-MMS header?

The first question is OK.  The second question needs to be rephrased as 
the following two questions:

Do we want to permit an Internet MUA or MTA to take special action based 
upon an MMS header?  If a hacker decides to generate X-MMS headers for the 
private use of the My Magic Service mailer, is there the slightest 
possibility that this will cause a problem for another Internet MUA or 
MTA?

I contend that:
 	if there is any harm caused by removing MMS headers
OR
 	if we want to permit an Internet MUA or MTA to take special action
 	based upon an MMS header
OR
 	if we want to allow an Internet MUA or MTA to set an MMS header
 	that can be passed to MMS land
OR
 	if our hacker using X- headers for the My Magic Service will
 	create the slightest possibility of grief for an Internet MUA or
 	MTA
then we MUST define non-experimental named (e.g. MMS) headers to represent 
these headers, and we MUST NOT use X-MMS headers.

Corrolary:

If there is no harm caused by removing MMS headers, then they MUST be 
removed because retaining them causes harm.  This is because:
  . if a header is defined, some hacker will decide to take special action
    based upon it.
  . some entity will presently to want to create an Internet->MMS gateway
    and define headers that go to MMS land.
  . there will presently be a hacker who uses X-MMS for the My Magic
    Service mailer.  [If challenged on this point, I hereby volunteer to be
    that hacker.]

If it is absolutely vital for debugging purposes that the MMS headers be 
passed, but NOT interpreted by Internet software, then use the existing 
comment mechanism of RFC 2822:

Comment: The following lines are from MMS for debugging purposes.  This
  data MUST NOT be used to take any special action.
   X-MMS-blurdybloop: 234
   X-MMS-sarasoop: owatagusiam
   X-MMS-Rena: a puppy rabbit, a twirly girl, a Missy Muddy-Paws
   X-MMS-MRC: this guy is freaking nuts
  E・nd of MMS debugging da.

Conclusion:

I see no place for X-MMS headers in the Internet world.  Either the 
headers are of value (their removal causes harm) and need real names of 
their own, or they are truly useless and their preservation causes harm.

I also don't understand why we are even discussing this point.  Whether or 
not you think that X-MMS is a problem, the fact that some people consider 
it to be a problem should suffice to deploy one of the presented 
alternatives which will silence our objections and allow us to move on to 
problems where there is no clear alternative.

Stubbornness in defense of something that is necessary may be a virtue. 
Stubbornness in defense of something that is unnecessary is not.

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.

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---

From: Mark Crispin <[email-masked]>
Date: Fri, 24 Jun 2005 09:15:16 -0700 (PDT)

On Fri, 24 Jun 2005, Vaudreuil, Greg M (Greg) wrote:
> X-MMS headers are no 
> more dangerous to the infrastructure than X-mailer and X-MS-priority.

You have just made my point.

We are under considerable pressure to support (not just generate, but 
process and make decisions based upon) X-Mailer and the various forms of 
X-Priority.  Because these are "standard", that's why; and we are being 
[pick your favorite slur] for not following this "standard".

The Lemonade WG, for the first time, proposes to define some X- headers as 
real IETF standards.  Rather than shore up the dyke, you want to bulldoze 
huge holes in it.

This is not progress.

-- Mark --

---

From: Randall Gellens <[email-masked]>
Date: Fri, 24 Jun 2005 10:10:55 -0700

At 9:15 AM -0700 6/24/05, Mark Crispin wrote:

>  We are under considerable pressure to support (not just generate, 
> but process and make decisions based upon) X-Mailer and the various 
> forms of X-Priority.  Because these are "standard", that's why; and 
> we are being [pick your favorite slur] for not following this 
> "standard".

Those headers have widely-implemented semantics within Internet mail. 
More importantly, those headers have nothing to do with the x-mms- 
headers in question.  Even more importantly, the proponents agreed 
many messages ago to change the treatment of the two x-mms- headers 
to match the rest of them.

-- 
Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
-------------- Randomly-selected tag: ---------------
(1) Alexander the Great was a great general.
(2) Great generals are forewarned.
(3) Forewarned is forearmed.
(4) Four is an even number.
(5) Four is certainly an odd number of arms for a man to have.
(6) The only number that is both even and odd is infinity.

Therefore, Alexander the Great had an infinite number of arms.