MBOX-Line: From barryleiba at computer.org  Sat Mar 14 07:25:21 2015
To: imap-protocol@u.washington.edu
From: Barry Leiba <barryleiba@computer.org>
Date: Fri Jun  8 12:34:54 2018
Subject: [Imap-protocol] DKIM signatures on this list
In-Reply-To: <alpine.LSU.2.20.1503131631020.2099@linux-0rhy>
References: <20150313211600.25485.qmail@ary.lan>
	<alpine.LSU.2.20.1503131631020.2099@linux-0rhy>
Message-ID: <CAC4RtVA-D1_yvYb8LOsN+ed7J=SyGNp3qEvgTsW=Gxst4xCw1A@mail.gmail.com>

The problem with your "you" thesis is that you're attributing things
to the signature that are not meant by DKIM signatures.  There is no
sensible comparison to be made between a purported signature by your
boss that asserts that she authorized you to spend money... and what a
DKIM signature asserts.  As John says, it's critical to fully
understand what DKIM signatures do and don't do, and not to use them
for things beyond what they're intended for.

Barry

On Fri, Mar 13, 2015 at 6:49 PM, Eduardo Chappa <echappa@gmx.com> wrote:
> On Fri, 13 Mar 2015, John Levine wrote:
>
>>>> The point of a signature is to have a way of verification of the message
>>>> as sent and received. If "you" received a message from your boss saying "I
>>>> approve that you spend ten thousand dollars in the company party" and the
>>>> signature of such message would not validate, that would certainly not be a
>>>> situation where "you" would say "the correct thing to do is to ignore it."
>>
>>
>> RFC 6376 is quite clear about what you do with an invalid DKIM signature
>> -- you ignore it, as though the signature wasn't there at all.  We
>> deliberately wrote it that way.
>
>
> The question is who is "you" in the sentence above. If you mean to say that
> "you" is the client implementor, well, there is no much that can be done to
> recover from such error. It is hard to try to recover, so "ignoring it" is
> sensible.
>
> However, the comment that originated this conversation was not a comment
> about the implementation of a RFC, it was about a user point of view, so
> while the comment you made may be sensible to implementors, I do not see it
> as such for users, and that is the context of what I saw.I read originally
> was not meant to say (in my opinion) that the list was
>
>> It's fine to treat mail with valid signatures differently from mail
>> without valid signatures, but it's not fine to treat mail with an invalid
>> signature differently from mail with no signature.  That's why you shouldn't
>> depend on lists to strip the signatures they break.
>>
>> I would have hoped that people interested enough in mail software to be on
>> this list would go to the effort to read and understand the specs they
>> implement.
>
>
> In generic terms I understand you. But the RFC is just that, and it is for
> implementors, not for users. I do not think that you can tell me, as a user,
> that it is "fine" when a signature does not validate, because I care to
> receive what was sent and I do not have any algorithmic way to know what the
> original message was. I know there is no much that can be done to fix it as
> an implementor, so in that sense, I should ignore the failure, but that is
> not what makes a user feels warm and fuzzy about the message they just
> received and fails to validate.
>
> --
> Eduardo
>
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