Re: [secdir] draft-ietf-appsawg-mdn-3798bis-15 SECDIR Review

[Alexey Melnikov <[e-mail]>]

Hi Donald,

Thank you for your comments.


On 01/12/2016 02:02, Donald Eastlake wrote:
> My apologies for getting this in late. I have reviewed this document 
> as part of the security directorate's ongoing effort to review all 
> IETF documents being processed by the IESG. Document editors and WG 
> chairs should treat these comments just like any other last call comments.
>
> This draft appears to be ready for publication with some nits..
>
> This draft polishes and advances to Internet Standard level RFC 3798 
> on Message Disposition Notifications.
>
> _Security Considerations:_
>
> The Security Considerations seem good except for one minor point: in 
> my opinion the option to return all or a portion of the original 
> message significantly increases the possible risk of use MDNs as a 
> traffic multiplier. I believe this should be mentioned in Section 6.4.

Thank you, I've added some text on this to the first paragraph of 
Section 6.4:

   Additionally, as generated MDN notifications can include full content 
of messages that caused them
   and thus they can be bigger than such messages, they can be used for 
bandwidth amplification attacks.

>
> _Miscellaneous:_
>
> The style of this draft is to say that you MUST do this and MUST NOT 
> do that without indicating what action should be taken if this is 
> violated. This is like saying a protocol field "MUST be zero" without 
> adding the usual "and is ignored on receipt". For example, in Section 
> 3 it says that a message disposition notification MUST NOT itself 
> request an MDN. I believe it should go on and add the few words to 
> say: "If one does, this is ignored." (unless that's wrong...) I'm not 
> saying this must always be done but there may be 1 or 2 other cases 
> like this in the draft where such wording should be added.

This is a difficult area, because we typically don't describe how to 
handle violations of MUSTs. In the case that you mention above, the text 
is added in order to prevent loops. Not much can be done on recipients 
end other than usual handling of spam and/or broken implementations.

Can you list other possible cases where you wanted some advice to be given?

> _Wording:_
>
> In Section 3, the wording of the last sentence of point d seems just a 
> bit obscure. It says
>         However, in the case of encrypted messages requesting MDNs,
>         encrypted message text MUST be returned, if it is returned at
>         all, only in its original encrypted form.
> I think it would be a just bit clearer as
>         However, in the case of encrypted messages requesting MDNs, if
>         the original message or a portion thereof is returned, it MUST
>         be in its original encrypted form.

I used your text, thank you.
>
> _Trivia:_
>
> I do wonder if the references to X.400 mail are necessary. They seem 
> archaic. Does anyone run X.400 email any more?

Yes :-)

> It is just used as an example, along with proprietary mail systems. I 
> think such proprietary systems still exist, but X.400 mail? I'm not so 
> sure. If it is going to be retained, maybe there should be an 
> Informational reference for it.

I will try to dig one out.