Re: Strict canonicalization considered harmful

From: Alessandro Vesely <>
Date: Tue, 09 Dec 2014 12:08:49 +0100

On Tue 09/Dec/2014 01:10:35 +0100 Murray S. Kucherawy wrote:
> On Sat, 6 Dec 2014, Alessandro Vesely wrote:
>> Blackops and sendmail tried to validate messages whose headers respectively
>> contained the following fields:
>> From: "Display phrase of 51, total line length line of 76" <>
>> From: "Display phrase of 51, total line length line of 76" <>
>> (those two apparently identical fields came back from those two validators.)
>> The corresponding field in a bcc to myself was:
>> From: "Display phrase of 51, total line length line of 76" <>
> One obvious thing is that double-space at the front.

Yes. It is a triple space, actually. A single space was present in the
original. Other autoresponders insert a newline in there.

> Certain versions of sendmail consume the leading space in a way transparent
> to milter, so it's there in the transported version but absent in what's
> passed to the filter. opendkim attempts to determine if the MTA it's talking
> to has the capability not to do that, but not all versions do. The MTA flag
> of interest is SMFIP_HDR_LEADSPC.

I don't think it's that, as it at most inserts one space.

It doesn't seem to be a version problem. Sendmail run 8.14.9/8.14.7, blackops
8.14.5/8.14.5. Out of the box 8.14.4/8.14.4/Debian-4 adds no spaces to a
76-long From: field. So it must be something else; either a configuration item
or an extraneous filtering appliance in-between.

>>> However, I just sent an empty message (using alpine as the MUA) through
>>> to and it came back fine.
>> What length did you try?
> Zero, or at least I never typed any body into alpine.

Sorry mate, I should have said I meant the length of the From: field; I thought
it was obvious...

> I just also did this:
> medusa[1873]% sendmail
> From:

Would you try the following for me, please?
From: "Display phrase of 49, so total line length is 76" <>

> To:
> Subject: Empty message test
> ^D
> This also came back with a GOOD result.

I'd be baffled if testing with a long From: field succeeds to. But I have no
idea why a length of 76 would break anything.

Received on Tue Dec 09 2014 - 11:09:02 PST

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