DKIM Deployment

[Jose-Marcio Martins da Cruz <>]

Serge Aumont wrote:
> On 14/01/10 01:37, Dave CROCKER wrote:
> > On 1/13/2010 4:27 PM, Jim Fenton wrote:
> > > > 1. changing the case of header names
> > > > e.g. s/Message\-ID/Message\-id/
> > > >
> > > > #2. changing the value of the Content-type header
> > > > # s/charset=us\-ascii/CHARSET=US\-ASCII/
> > > > # this one might be due to a misconfiguration
> > > These are both pretty silly -- changing the case of case-insensitive
> > > values.
> > Actually, what's silly is having an algorithm that /cares/ about case,
> > for a case-insensitive string...
> Do you mean that DKIM canonicalization algorithm should convert all
> headers when preparing message from signature or verification ?

There were two examples :

* converting header names (name, not value) to low/high case doesn't seem to me a big problem, as 
headers are some sort of structured information. Message body isn't. So, why not ?

* reformating dates in a received header inserted by some one other... is a more complex operation 
and opens the door to many other questions...

> Received: from [128.104.19.133] by web81602.mail.mud.yahoo.com via HTTP; 
Wed,
>- 13 Jan 2010 08:22:31 -0800 (PST)
>-Message-id: 
<>
>+ 13 Jan 2010 08:22:31 PST
>+Message-ID: 
<>

Converting headers case before signing and verification may be a problem in some cases. Headers 
names are case insensitive, but headers value aren't allways. E.g. an email address information in 
From and To headers is case insensitive, but the subject isn't.

IMHO, as long as possible, DKIM should avoid any heuristics needing some 
semantics interpretation.


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 Jose Marcio MARTINS DA CRUZ           http://j-chkmail.ensmp.fr
 Ecole des Mines de Paris
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