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Re: [ietf-dkim] Re: Use of LWSP in ABNF -- consensus call

Tony Finch <dot@dotat.at> Fri, 18 May 2007 08:00 UTC

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Date: Fri, 18 May 2007 09:00:43 +0100
From: Tony Finch <dot@dotat.at>
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To: John C Klensin <john-ietf@jck.com>
Subject: Re: [ietf-dkim] Re: Use of LWSP in ABNF -- consensus call
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On Thu, 17 May 2007, John C Klensin wrote:
>
> After all <CRLF> Thing <SPACE><CRLF> could case similar problems if
> some construction permitted it ...

This is not news. There have for a long time been problems with
significant trailing space, which is why CRLF 1*WSP CRLF in a header
is part of the obs- syntax of 2822, and why quoted-printable encodes
WSP at the end of a line.

> ... and defining a grammar that would prohibit any <SPACE><CRLF>
> construction isn't easy in ABNF for reasons that have nothing to
> do with LWSP.

This is simply incorrect. It's trivial to define a whitespace
construction that only allows CRLF at the beginning of a sequence:

	NTWSP = [CRLF] 1*WSP ; non-trailing white space

Tony.
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