Subject: [ietf-dkim] Regarding Relaxed Canonicalization

From: deiva shanmugam <[email-masked]>
Date: Tue, 10 Mar 2009 09:00:19 +0530

Hi,

   Can anyone please let me know, if control characters like vertical tab,
Form feed, page eject etc are available in the header, what has to be done,
when relaxed canonicalization for the headers is followed?

Example:

Content-Type:*^L*multipart/alternative;*^K*
boundary=^M"----=_NextPart_000_0000_JLZRZLJO.OULDWYUC"

Thanks,
Deiva Shanmugam
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From: Suresh Ramasubramanian <[email-masked]>
Date: Tue, 10 Mar 2009 09:08:08 +0530

As I understand it, that's broken.  Carriage returns / linefeeds fine.
 Form feeds, vertical tabs?

--srs

On Tue, Mar 10, 2009 at 9:00 AM, deiva shanmugam
<[email-masked]> wrote:
> Content-Type:^Lmultipart/alternative;^Kboundary=^M"----=_NextPart_000_0000_JLZRZLJO.OULDWYUC"
>
> Thanks,
> Deiva Shanmugam
>

---

From: deiva shanmugam <[email-masked]>
Date: Tue, 10 Mar 2009 09:18:43 +0530

Ya. I checked the definition before . I wanted clarify as in Sendmail's dkim
code , canonicalization for this header:
Content-Type:^Lmultipart/alternative;^Kboundary=^M"----=_NextPart_000_0000_JLZRZLJO.OULDWYUC"

On Canonicalization,
content-type:multipart/alternative;
boundary=^M"----=_NextPart_000_0000_JLZRZLJO.OULDWYUC"

Form feed was removed & vertical tab was converted into space.

So, control characters need not be removed and i can follow with the same
procedure?

Thanks,
Deiva Shanmugam

On Tue, Mar 10, 2009 at 9:10 AM, Tony Hansen <[email-masked]> wrote:
>
> Look at the definition of relaxed header section 3.4.2. It talks about
> stripping/reducing WSP (SP and TAB) characters, unfolding lines,
> removing CRLF before continuation lines, and doing case folding. It
> doesn't mention anything about treating any other characters specially.
>
>        Tony Hansen
>        [email-masked]
>
> deiva shanmugam wrote:
> > Hi,
> >
> >    Can anyone please let me know, if control characters like vertical
> > tab, Form feed, page eject etc are available in the header, what has to
> > be done, when relaxed canonicalization for the headers is followed?
> >
> > Example:
> >
> >
Content-Type:*^L*multipart/alternative;*^K*boundary=^M"----=_NextPart_000_0000_JLZRZLJO.OULDWYUC"

---

From: "Murray S. Kucherawy" <[email-masked]>
Date: Mon, 9 Mar 2009 21:13:24 -0700 (PDT)

> boundary=^M"----=_NextPart_000_0000_JLZRZLJO.OULDWYUC"

^L (ASCII 0x0C or "new page") and ^K (ASCII 0x0B or "vertical tab") are 
illegal in header fields according to RFC5322 (see section 2.2).  ^M 
(ASCII 0x0D or "carriage return") is only allowed when doing header 
folding, which means they must also be followed by whitespace.

So the above example is complete gibberish according to RFC5322 and, thus, 
to DKIM as well.
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---

From: Tony Hansen <[email-masked]>
Date: Mon, 09 Mar 2009 23:40:37 -0400

Tony Hansen
	[email-masked]

---

From: John Levine <[email-masked]>
Date: 10 Mar 2009 11:29:47 -0000

>So, control characters need not be removed and i can follow with the
>same procedure?

I recall a question something like this coming up in the past, and the
answer is that DKIM only applies to valid 2822 and now 5322 messages.
If the header contains characters not allowed in 2822/5322, no matter
what you do, it's not a valid signed message and you can't count on
recipients accepting it as signed.

R's,
John