Re: [dmarc-ietf] Authentication of reports

"Murray S. Kucherawy" <> Wed, 20 January 2021 22:56 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id B63A33A15AF for <>; Wed, 20 Jan 2021 14:56:45 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.097
X-Spam-Status: No, score=-2.097 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id cjEgDQV5LQKu for <>; Wed, 20 Jan 2021 14:56:44 -0800 (PST)
Received: from ( [IPv6:2607:f8b0:4864:20::e32]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id DFFB43A15AD for <>; Wed, 20 Jan 2021 14:56:43 -0800 (PST)
Received: by with SMTP id j17so36547vso.9 for <>; Wed, 20 Jan 2021 14:56:43 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=UlnepI50Pbm7nlUD7T2+iQWuE8+81RKjSDLTl3EXkO0=; b=PS5c7oYOcZraXx/9KIfW1wWcB0tWUjSuoKypoyY45FsLNaCXMjZVnsNfg4TBuzpJOj JD8e/jKBdNjQD41HnJHW6eboerdDK+6t83Z6WoL2IVAPklpRyqYef3+wXntYhHuBzD1g hShCBGiRZ5YttscZ7LdSXJQ6RUsn8btPBxxPdKSVre04XZGsJMc8pic+EHvsUxlIbXF3 q0lBvX5YiYxHzfPgjecAFH28NevGlrT/ZMg0onZTOPwCLIc+KQjoNrYktO6x4XhA9Y+U okUHcIZRmq1NQficRqAhX0HXuc1OT1Ub08rapK8rMHpIYeZhjW5l4K6qm+RJVZWlBt+2 Wy1A==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=UlnepI50Pbm7nlUD7T2+iQWuE8+81RKjSDLTl3EXkO0=; b=LriuwqgOfpgcc+Hqg4idR/NzB8zZnrETH1WBYS4IdTv0zQRhQkSV7ZD5PLXrjEzmfx L9xpfc5d/W0ohcO7Sp2qC6O9MqIW7fgljWRwSTPpIn3LciUXdaUQubjsCeKS/+DtYHj/ JfY+PMJythLNHcuNkJOS0SPOPiTcLniE2M6XySsjYjVzABxhjxeDiONQ6KkIohfKzhk2 Y3Uu6MF+j8UFzSXR8N2wNCj9Bel4K0FppH1sfisfFyVvvyBDPAmxdx39vU6/xX+2NSUY cB8qhC6frxjICgtyYt0/jfq0Ac287hXc20wlkh96nSMonNFXlvzKIHdAB6mheXQ0vjfP dlbQ==
X-Gm-Message-State: AOAM531oMhWsnALpwg4i8aeZASmaLKSfVm16acXinacW7RCXY85XbyRe IoPRtXff7gHyOTT7o7lbHddTYcQK6MZd/Wx1dVPDE8PWIa4=
X-Google-Smtp-Source: ABdhPJwk/3E2MRPNNus1iesFHJTp6FR95bB5EG32GXcsxyHo9Vur4jl/dkjiIbIHE4Xm/ddU2Lj6V/I0m0pVwNxqKWY=
X-Received: by 2002:a67:18c6:: with SMTP id 189mr8504840vsy.54.1611183402743; Wed, 20 Jan 2021 14:56:42 -0800 (PST)
MIME-Version: 1.0
References: <>
In-Reply-To: <>
From: "Murray S. Kucherawy" <>
Date: Wed, 20 Jan 2021 14:56:31 -0800
Message-ID: <>
To: Michael Thomas <>
Cc: "" <>
Content-Type: multipart/alternative; boundary="00000000000063808e05b95cdefa"
Archived-At: <>
Subject: Re: [dmarc-ietf] Authentication of reports
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Domain-based Message Authentication, Reporting, and Compliance \(DMARC\)" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 20 Jan 2021 22:56:46 -0000

On Wed, Jan 20, 2021 at 1:21 PM Michael Thomas <> wrote:

> I just scanned through DMARC and I couldn't find any security
> requirements/mechanisms for the failure reports. I would think at the
> very least the receiver consuming the reports ought make certain that
> the report at the very least have either a valid DKIM signature or a SPF
> pass. Unauthenticated data is always the source of mischief, and I'm
> sure that there have to be attacks that are possible with
> unauthenticated reports. At the very least this should be a security
> consideration, and most likely should have some normative language to
> back it up.

I thought the usual rules about when you should or shouldn't trust a
message ought to be applied, but I guess we never actually said that in the
document.  We certainly could.

Since I'm sort of new, it's been unclear to me whether whether having a
> new https transport mechanism is in scope or not -- it seems to come up
> pretty often -- but I'm not sure how people would propose to
> authenticate the report sending client. That seems to me to be a basic
> security requirement for any new delivery method. The problem here is
> there isn't a client certificate to determine where the report is coming
> from or any other identifying mechanism. An alternative might be to DKIM
> sign the report itself, but the long and short is that it would need to
> be addressed.

As I recall DMARC originally (in its pre-RFC versions) did have "https" as
a supported scheme for "rua", but since nobody implemented it during the
years DMARC was in development, it got dropped before publication.