From nobody Mon Nov 29 23:27:54 2021 Return-Path: X-Original-To: dmarc@ietfa.amsl.com Delivered-To: dmarc@ietfa.amsl.com Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 57DA73A10BE for ; Mon, 29 Nov 2021 23:27:52 -0800 (PST) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -2.098 X-Spam-Level: X-Spam-Status: No, score=-2.098 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] autolearn=ham autolearn_force=no Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Wg8PPWGBSIXV for ; Mon, 29 Nov 2021 23:27:50 -0800 (PST) Received: from mail-ua1-x935.google.com (mail-ua1-x935.google.com [IPv6:2607:f8b0:4864:20::935]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 4AF0B3A10BB for ; Mon, 29 Nov 2021 23:27:50 -0800 (PST) Received: by mail-ua1-x935.google.com with SMTP id p37so39464972uae.8 for ; Mon, 29 Nov 2021 23:27:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=T2XmC5A6EiADWt78QV9qTcvQ46UH1fQM8oJwpfLNiDo=; b=oL+cdtcmrBZ0mMWQ9mPVfNG1ehHnn7PC/TuTJ8gYBEkNl7JePcm0/7NFllzygy+Dqw CLnWFd5UhnPUI8CFXtTOIs1mbavEOMi1IaMZuzPqfTxWe0mt452Vu9weO5/PRRq55vIF WNS8I8CK/zNogNSnqQoayCTNiInJpvB4lMznqSnOgSGK37gD2NSKi5HgM9JiMm3UqeZC V0yrZ4gSaWWAtHp6HXmeJeUvmP/uAqhqtpcB/KfQFmTymfdtu98x1lZClsrxfHOXyiZo mG50iiSsrBox+FUNUckf9cBIN3ibNLuTkhAROo6PrIJQ9cqZSYJ+NRZ1kHhF4MNjSHY+ 6N+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=T2XmC5A6EiADWt78QV9qTcvQ46UH1fQM8oJwpfLNiDo=; b=CMzBC4IS3oZSz1/9L+bXeefPlnICyVEwIXwlY9LY9VzJqEcnpoUbz8ir42FTEttY50 WkqOTssIOme+OjtcYeBd4YS0abcRz5/5khgA2+xdIkhNpVzFqxndFiZbqQLsMw4PDdo5 YYSROc5xSBRYZRle11/KFWKTfohprcRD+/PubcHT2KZItaQO/wSApi/vXZtXQaW7Uiux UrmPhQgh+8UHaVEUER1vvy8szu72MstE2v/0xecDae9fTqDQsz7/xJDFSWCSqYtTcLMH LeHSyYC1o6y+scF0Hexepk7sqleTJyxR0HHR6DktzSyhaNzBNS9f1GdFQHxY/Wa7Hd5J AKnA== X-Gm-Message-State: AOAM530u3tlx80gdt5onDKarRpq1ptB2TBGwlvSS1PlBI+iBr+rWZVDc O9qgOl5BCWj4b8+vLf7ZFgeG2DhTCuLd8Jc+N5M= X-Google-Smtp-Source: ABdhPJz1YRd4/fIpDq7kmqCVLq2WngXitAASnX+oxW9nfCoUyNUhJ55ylUe89hwLprd22FhxGFcGUAobqAjU8Tzmaho= X-Received: by 2002:a67:3382:: with SMTP id z124mr38680065vsz.57.1638257264933; Mon, 29 Nov 2021 23:27:44 -0800 (PST) MIME-Version: 1.0 References: <6aad0642-f73c-ba6f-d26c-1c1fd90e2c9a@tana.it> In-Reply-To: From: "Murray S. Kucherawy" Date: Mon, 29 Nov 2021 23:27:34 -0800 Message-ID: To: Wei Chuang Cc: Alessandro Vesely , IETF DMARC WG Content-Type: multipart/alternative; boundary="00000000000053c19c05d1fc7e85" Archived-At: Subject: Re: [dmarc-ietf] Reversing modifications from mailing lists X-BeenThere: dmarc@ietf.org 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: Tue, 30 Nov 2021 07:27:53 -0000 --00000000000053c19c05d1fc7e85 Content-Type: text/plain; charset="UTF-8" On Thu, Nov 25, 2021 at 12:07 AM Wei Chuang wrote: > Sorry I wasn't too clear here. It's largely the same idea as the DKIM > body length "l=" field above except for reformulated for the Subject header > and its mailing list mutations. The original sender would encode a length > of the original subject say "s.l=". A receiver would only hash the > right most "s.l=" length string when validating a Subject hash from > the original sender. This assumes that mailing lists may prepend a string > typically for identification. Seems to me that means I could insert anything I want before the last N octets of Subject -- say, a URI pointing you to an ad or other unsavory content -- and the original signature will verify. -MSK > --00000000000053c19c05d1fc7e85 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Thu, Nov 25, 2021 at 12:07 AM Wei Chua= ng <weihaw@google.com> wrote= :
Sorry I wasn't too clear here.=C2=A0 It's largely the same idea as = the DKIM body length "l=3D" field above except for reformulated f= or the Subject header and its mailing list mutations.=C2=A0 The original se= nder would encode a length of the original subject say "s.l=3D<valu= e>".=C2=A0 A receiver would only hash the right most "s.l=3D&l= t;value>" length string when validating a Subject hash from the ori= ginal sender.=C2=A0 This assumes that mailing lists may prepend a string ty= pically for identification.

Seems to me tha= t means I could insert anything I want before the last N octets of Subject = -- say, a URI pointing you to an ad or other unsavory content -- and the or= iginal signature will verify.

-MSK
--00000000000053c19c05d1fc7e85--