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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 6 Feb 2019 07:27:25 +0000
Message-ID: <CAADWXX-nxpVxPmwsKKqeNHZY1OWF=a1YB93Y9g3w87zPSa5=CQ@mail.gmail.com>
Subject: Re: [PATCH v3 1/4] staging: iio: ad7780: add gain & filter gpio support
To:     Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc:     lkml <linux-kernel@vger.kernel.org>
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Peter,

 this email was marked as spam for me (and probably others) because of
this DKIM signature:

   DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=pmeerw.net; s=mail;
       ....

where the problem is that when the message goes through the
vger.kernel.org mailing list machinery, the header whitespace will be
modified.

As a result, the DKIM signature no longer matched, and at least gmail
will consider the email to be spam.

That's arguably a bug in the vger mail server setup, but equally
arguably the "c=simple/simple" model of hashing in DKIM is just
broken, and shouldn't be used. Whitespace in SMTP headers is simply
not meaningful, and checking whitespace in them (like simple/simple
does) is misguided.

If you have control over the DKIM setup of pmeerw.net, may I suggest
changing the DKIM setup to use "c=relaxed/relaxed", which doesn't
invalidate the signature just for whitespace changes in the headers,
and which is the proper DKIM model to use. The simple canonicalization
really is too simple-minded for  email.

            Linus

On Tue, Feb 5, 2019 at 7:58 PM Peter Meerwald-Stadler <pmeerw@pmeerw.net> wrote:
>
> On Tue, 5 Feb 2019, Renato Lui Geh wrote:
>
> > Previously, the AD7780 driver only supported gpio for the 'powerdown'
> > pin. This commit adds suppport for the 'gain' and 'filter' pin.
>
> comments below
[...]