Re: [ietf-822] A permission to re-sign header
Alessandro Vesely <vesely@tana.it> Fri, 18 April 2014 12:17 UTC
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Date: Fri, 18 Apr 2014 14:17:09 +0200
From: Alessandro Vesely <vesely@tana.it>
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Subject: Re: [ietf-822] A permission to re-sign header
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Hi John, On Fri 18/Apr/2014 04:19:25 +0200 John Levine wrote: > As I understand it, the original sender puts a hard to forge single > use token in the message, which the forwarder can include in the > signed message. > > Since I am lazy, I will reuse DKIM key records and invent a new > May-Resign header something like this: > > May-Resign: f=marissam@yahoo.com; r=ietf.org; s=foo; a=rsa-sha256; \ > t=1397786669; b=hashhashhash > > This is a permission to re-sign for a message From: > marissam@yahoo.com, to be re-signed by a mailing list at ietf.org. The > s= and a= and t= are the same as DKIM, the b= is a signature of a hash > of the M-R header, similar to the b= signature in a DKIM-Signature. > > The relay includes the M-R header in the DKIM signature. So now > we modify DMARC to say that > > IF there is a M-R header with f= that matches the From: line address, > > AND the M-R header is included in a DKIM signature that is signed with > d= that matches the M-R r= > > AND the M-R signature validates using the s= selector and f= domain > > AND the t= isn't too old (for some meaning of too old) The difference from the Date: is interesting too, since the latter field is often visible and signed. > THEN the message is considered to be aligned. > > Is that the general idea? Even with the local part (marissam) an M-R is not really hard to forge, otherwise DKIM-Signature wouldn't have had to include all the other tags. If we worry about replay attacks, we can enhance M-R so that it includes them too. For example, we could make M-R exactly like a regular DKIM-Signature, except that it would be a very very weak one, something that the MLM won't break. Oh, and of course we have r=, but then its content could live in its own field. With such changes M-R would become quite similar to the joint signatures idea (http://tools.ietf.org/html/draft-vesely-dkim-joint-sigs-00). An obvious advantage of following the DKIM specs exactly is to save developing extra code. Another advantage is that end receivers who ignore M-R will just see a valid author signature. For example, this message likely passes DMARC validation. > You could put an M-R header on anything, but if you want to limit it > to mail to addresses that claim to be mailing lists, you could use the > same name convention as the DANE S/MIME draft, with hashed mailboxes, > e.g.: > > <hash of ietf-822>._mayresign.ietf.org TXT "v=MR1; d=ietf.org" > > That says the ietf-822@ietf.org list is signed with d=ietf.org. If a > domain contains only mailing lists, you can use a wildcard > > *._mayresign.lists.iecc.com TXT "v=MR1; d=lists.iecc.com" I'd add fields that won't be modified. For example: v=MR1; d=ietf.org; h=Date:From:To:References:In-Reply-To; Another tag could be used to say what to do with content, if it will be fine to sign it using l=original length, or l=0. The directive for l= may need to differ depending on the Content-Type (text/plain or MIME multipart). Lazy submission servers could stick to the least common signing directives instead of separately signing each copy of an outgoing message, in case there are multiple mailing lists among the recipients. BTW, would it make sense to mandate some simple heuristic, for example $addr=~/list/, to save DNS queries? Ale
- [ietf-822] A permission to re-sign header John Levine
- Re: [ietf-822] A permission to re-sign header Alessandro Vesely
- Re: [ietf-822] A permission to re-sign header John Levine
- Re: [ietf-822] A permission to re-sign header Hector Santos
- Re: [ietf-822] A permission to re-sign header Murray S. Kucherawy
- Re: [ietf-822] A permission to re-sign header John R Levine
- Re: [ietf-822] A permission to re-sign header Murray S. Kucherawy
- Re: [ietf-822] A permission to re-sign header John R Levine
- Re: [ietf-822] A permission to re-sign header Pete Resnick
- Re: [ietf-822] A permission to re-sign header Pete Resnick
- Re: [ietf-822] A permission to re-sign header John R Levine
- Re: [ietf-822] A permission to re-sign header Pete Resnick
- Re: [ietf-822] A permission to re-sign header John R Levine
- Re: [ietf-822] A permission to re-sign header Alessandro Vesely
- Re: [ietf-822] A permission to re-sign header Michael Richardson
- Re: [ietf-822] A permission to re-sign header Michael Richardson
- Re: [ietf-822] A permission to re-sign header Theodore Ts'o
- Re: [ietf-822] A permission to re-sign header Pete Resnick
- Re: [ietf-822] A permission to re-sign header Miles Fidelman
- Re: [ietf-822] A permission to re-sign header John Levine
- Re: [ietf-822] one can re-sign without a permissi… Ned Freed
- Re: [ietf-822] one can re-sign without a permissi… Alessandro Vesely
- Re: [ietf-822] A permission to re-sign header Ned Freed
- Re: [ietf-822] A permission to re-sign header Alessandro Vesely
- Re: [ietf-822] A permission to re-sign header Paul Smith
- Re: [ietf-822] don't need a permission to re-sign… John Levine
- Re: [ietf-822] don't need a permission to re-sign… Ned Freed
- Re: [ietf-822] don't need a permission to re-sign… John R Levine
- Re: [ietf-822] don't need a permission to re-sign… Ned Freed
- Re: [ietf-822] one can re-sign without a permissi… Alessandro Vesely
- Re: [ietf-822] one can re-sign without a permissi… Ned Freed
- Re: [ietf-822] one can re-sign without a permissi… Pete Resnick
- Re: [ietf-822] one can re-sign without a permissi… Douglas Otis
- [ietf-822] We need a DKIM Policy Working Group Hector Santos
- Re: [ietf-822] We need a DKIM Policy Working Group S Moonesamy
- Re: [ietf-822] one can re-sign without a permissi… John Levine
- Re: [ietf-822] one can re-sign without a permissi… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Miles Fidelman
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Alessandro Vesely
- Re: [ietf-822] one can re-sign without a permissi… Douglas Otis
- Re: [ietf-822] one can re-sign without a permissi… Pete Resnick
- Re: [ietf-822] one can re-sign without a permissi… Alessandro Vesely
- Re: [ietf-822] one can re-sign without a permissi… Paul Smith
- Re: [ietf-822] one can re-sign without a permissi… John R Levine
- Re: [ietf-822] one can re-sign without a permissi… Hector Santos
- Re: [ietf-822] one can re-sign without a permissi… Douglas Otis
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Alessandro Vesely
- Re: [ietf-822] one can re-sign without a permissi… Hector Santos
- [ietf-822] WSJ/gmail/ML, was a permission to... Alessandro Vesely
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John R Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Paul Smith
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Rolf E. Sonneveld
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Hector Santos
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Michael Richardson
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Paul Smith
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Alessandro Vesely
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Miles Fidelman
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John R Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Arnt Gulbrandsen
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Ned Freed
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Dave Crocker
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Ned Freed
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John R Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John R Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Arnt Gulbrandsen
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Bart Schaefer
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Hector Santos
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Michael Richardson
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Michael Richardson
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Ned Freed
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Michael Richardson
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Michael Richardson
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Russ Allbery
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Brandon Long
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Brandon Long
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Arnt Gulbrandsen
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Alessandro Vesely
- Re: [ietf-822] one can re-sign without a permissi… Paul Smith
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Hector Santos
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John R Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Ned Freed
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… S Moonesamy
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Russ Allbery
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Hector Santos
- Re: [ietf-822] one can re-sign without a permissi… Brandon Long
- Re: [ietf-822] one can re-sign without a permissi… Murray S. Kucherawy
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Miles Fidelman
- Re: [ietf-822] one can re-sign without a permissi… John R Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Ned Freed
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… S Moonesamy
- Re: [ietf-822] one can re-sign without a permissi… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Miles Fidelman
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Scott Kitterman
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Russ Allbery
- Re: [ietf-822] one can re-sign without a permissi… Murray S. Kucherawy
- Re: [ietf-822] one can re-sign without a permissi… John R Levine
- Re: [ietf-822] one can re-sign without a permissi… Hector Santos
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… S Moonesamy
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Paul Smith
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Alessandro Vesely
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Miles Fidelman
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… John Levine
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Brandon Long
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Brandon Long
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Russ Allbery
- [ietf-822] Aptness of DKIM for MLs Alessandro Vesely
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Alessandro Vesely
- Re: [ietf-822] Aptness of DKIM for MLs S Moonesamy
- Re: [ietf-822] Aptness of DKIM for MLs Alessandro Vesely
- Re: [ietf-822] Aptness of DKIM for MLs S Moonesamy
- Re: [ietf-822] Aptness of DKIM for MLs Hector Santos
- Re: [ietf-822] Aptness of DKIM for MLs Douglas Otis
- Re: [ietf-822] Aptness of DKIM for MLs Alessandro Vesely
- Re: [ietf-822] Aptness of DKIM for MLs Douglas Otis
- Re: [ietf-822] WSJ/gmail/ML, was a permission to.… Douglas Otis
- Re: [ietf-822] Aptness of DKIM for MLs Alessandro Vesely
- Re: [ietf-822] one can re-sign without a permissi… Douglas Otis