Subject: [ietf-822] Q: Space stuffing (RFC 3676)

From: Alessandro Vesely <[email-masked]>
Date: Mon, 18 Jul 2016 10:53:31 +0200

Hi all,

Section 4.4 of RFC 3676 says:

    On generation, any unquoted lines which start with ">", and any lines
    which start with a space or "From " MUST be space-stuffed.  Other
    lines MAY be space-stuffed as desired.

What does "as desired" mean?  If lines are treated at random, it is obviously 
impossible to tell stuffed spaces from original indentation.  (By comparison, 
SMTP leaves no ambiguity on whether or not a line has to be dot-stuffed.)

My question is how is that extra leeway to be interpreted.  What are the best 
practices for space-stuffing?  Let me recall that those ">From "s break many a 
DKIM signature, so supporting RFC 3676 is de rigueur for mailers committed to 
email authentication.

Ale

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From: Tony Finch <[email-masked]>
Date: Mon, 18 Jul 2016 14:39:43 +0100

Alessandro Vesely <[email-masked]> wrote:
> impossible to tell stuffed spaces from original indentation.

I think it should say that indented lines MUST also be space-stuffed.

Tony.
-- 
f.anthony.n.finch  <[email-masked]>  http://dotat.at/  -  I xn--zr8h punycode
Portland, Plymouth: East 4 or 5, becoming variable 3 or 4 later. Slight,
occasionally moderate. Fair. Moderate or good.

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From: Alessandro Vesely <[email-masked]>
Date: Mon, 18 Jul 2016 19:59:03 +0200

> I think it should say that indented lines MUST also be space-stuffed.

Agreed.  I'm puzzled by that paragraph only says /space/ while Section 4.2 (on 
the DelSp parameter) proves full awareness of non-ASCII spaces, such as nbsp 
(160) and the suite of invisible unicode points, not to mention tab (9), that 
an author may use to produce indentation.  Does that deserve errata?

Adding a space in front of each line would make the message appear less garbled 
to users of space-stuffing-unaware clients.  Are such clients so many to 
justify the waste of one more byte per line?

Ale