Hello, We noticed in Google Postmaster Tools a lot of bad reputation IPs which do not belong to us, and are actually forbidden from sending emails on our behalf via SPF -all, yet Gmail thinks the messages from these IPs were fully authenticated.
After investigating some reports, it looks like a DKIM replay attack, where Gmail does not validate the original DKIM signature (which includes Message-ID:Reply-To:To: fields), and even ignores SPF permerror, if the message contains ARC headers. Full headers below, any insights or suggestions would be appreciated: Delivered-To: incident-repor...@gmail.com Received: by 2002:ab0:340c:0:0:0:0:0 with SMTP id z12csp1291860uap; Fri, 28 Jan 2022 15:34:21 -0800 (PST) X-Google-Smtp-Source: ABdhPJxGsLcEEUpdbgGs3QgR03Rr9huo0nZHyOFLB9HDsbANUeb9dkNH/PpuXMfWArmb2WtJtVZk X-Received: by 2002:a17:902:cec8:: with SMTP id d8mr10494650plg.98.1643412861553; Fri, 28 Jan 2022 15:34:21 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1643412861; cv=pass; d=google.com; s=arc-20160816; b=VU0Qf7i3UDk9cIk0HEQEv2hW46LmdHN1Z9UysluJsh4o1O1v5t12RrICEe8YlzFcZZ UziO53/5IMPjyEVGqLIEyLq0v0Dz5B4gtR94biUHiyIVYEEbn+20dr6ONrGE/IKsYBWD 2pBDc/D+Ppe4rBBhwQOckw9xK9f/l+RS1sbRU1AY2sW2hqJZzjSZUe0scWUGvbwB4RZl IS+F5z/T/ZLZ9s1v4JXmOoEnKu5b9oZ3XhJgc5EVYuAWJRFOrqIA7bRS8ISDJ+J/eYtJ fI9gWI5UkkM6qIgY/wFngV0FifP2Yauo/ts7su9FzFmxgHJdCLioQiFy4E6EEv8qN78c YrAA== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=date:date:content-transfer-encoding:mime-version:to:reply-to:from :subject:subject:message-id:dkim-signature:dkim-signature :delivered-to; bh=JYMTX3Rr+OZICy76j7DTKZeSFGH9xqoJ5IlXE//bwFY=; b=FdwHNKthXMrmoT3OevMII/o6PzRZR8UA6zIwTYBTTF2EA63hRW6yJVj7mQLBEyAQ6x WzjOhIf9zLeqzNYraveRpGQRcXUE/PqTaKDbzhTcqPfP9g82ea9dLhHgviwerKh1IhAp 3dri2wT2epRaIYnzEX2gMzmt8YiYjj3sHgvDDjg4Up4W1pYPmP4zx7N0UYxihu0B7eP6 4igCLE8hfq1VPzWistU6uTe+HkSIupCpz8X1pQ41DcjLuwjfIsy18HXLH8yXqwyg37u5 +HX04rA5UlBMEOQnZhHneFGM7JrDU4Z7Yg6o/+uFkL7RfPE265N9CUS0YevgBX5D4IEY VwuA== ARC-Authentication-Results: i=2; mx.google.com; dkim=temperror (no key for signature) header.i=@ knowledgemodish.org.uk header.s=sender header.b=heNp+Lc9; dkim=pass header.i=@sendersrv.com header.s=smtp header.b=Ra7fdByf; arc=pass (i=1 spf=pass spfdomain=sendersrv.com dkim=pass dkdomain= sendersrv.com); spf=permerror (google.com: permanent error in processing during lookup of 921108683ccq405...@universidadebrasil.edu.br: host.universidadebrasil.email not found) smtp.mailfrom= 921108683ccq405...@universidadebrasil.edu.br Return-Path: <921108683ccq405...@universidadebrasil.edu.br> Received: from lingojam.com ([212.83.129.110]) by mx.google.com with ESMTP id j9si7146126plx.86.2022.01.28.15.34.21 for <incident-repor...@gmail.com>; Fri, 28 Jan 2022 15:34:21 -0800 (PST) Received-SPF: permerror (google.com: permanent error in processing during lookup of 921108683ccq405...@universidadebrasil.edu.br: host.universidadebrasil.email not found) client-ip=212.83.129.110; Authentication-Results: mx.google.com; dkim=temperror (no key for signature) header.i=@ knowledgemodish.org.uk header.s=sender header.b=heNp+Lc9; dkim=pass header.i=@sendersrv.com header.s=smtp header.b=Ra7fdByf; arc=pass (i=1 spf=pass spfdomain=sendersrv.com dkim=pass dkdomain= sendersrv.com); spf=permerror (google.com: permanent error in processing during lookup of 921108683ccq405...@universidadebrasil.edu.br: host.universidadebrasil.email not found) smtp.mailfrom= 921108683ccq405...@universidadebrasil.edu.br Delivered-To: ysoul8...@gmail.com Received: by 2002:a02:a14a:0:0:0:0:0 with SMTP id m10csp394823jah; Fri, 28 Jan 2022 07:31:40 -0800 (PST) X-Received: by 2002:a2e:2a04:: with SMTP id q4mr6116831ljq.428.1643383900388; Fri, 28 Jan 2022 07:31:40 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1643383900; cv=none; d=google.com; s=arc-20160816; b=Lnn5XQ1j10ikEZENe8i0XPsyPhwpp7AAaEODfKuODEjNcgDxtfjOyVE4biwI1oWuel znv1YmtupI95DExnRKpyq20MVqQL9IhRrMxK/O5lrxz9u8tgwzFpq4fTh4urmZTy/dnW EWvT5WZWdK0+8k5+1WRtiCiLTj5cg6VIT+vrC+1ut/X2o9bMghmgqZETCQpMGSHvcWkB WN1iuiszzcHB+/v6LTtAwxJIi3UGrsmEj5IwfSOyIEljA+S2ZYKFGm/08s4ulS5nfRru gFLMH+hrsAi4YyJwSDhkNegHZYYUFmB24zA2CCwss+FJSlKSRtliiVnVP2TfWbUfxxA4 QD9w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=date:content-transfer-encoding:mime-version:to:reply-to:from :subject:message-id:dkim-signature:dkim-signature; bh=JYMTX3Rr+OZICy76j7DTKZeSFGH9xqoJ5IlXE//bwFY=; b=nkQkfmL3Wm2z/Jl6yBa1TjePKO2rjBSUPrLlpKwWItDIjX5qEAHJIY2fjQ0rDPe20F OJuiHppDcLLSImVdVVW542bNQWr8bwBhI+dJJ9VFFJqvssH5Apu+f3KU1bq5hQg+GFhu /Xx1Pl+I63f5TTyzqOGxS74fv2ycytsumnRvrC3SSN2TN8FAoD9eCq64y2ufcvfogmr+ /qQiNBxLyiCL+lJd0pau8YpyeA+MP5iVcAjIulXD9JqBfZvUiNm7Lj5l8CxNLXKcPcPR dHFlMGQ1G/qMulV/2ag1OiQcT9NriqHsxgZ1N9cFnMAFdTz1470CRhx7rcRFsiI2auon IG/Q== ARC-Authentication-Results: i=1; mx.google.com; dkim=temperror (no key for signature) header.i=@ knowledgemodish.org.uk header.s=sender header.b=heNp+Lc9; dkim=pass header.i=@sendersrv.com header.s=smtp header.b=Ra7fdByf; spf=pass (google.com: domain of bounces-test770...@sendersrv.com designates 185.3.229.126 as permitted sender) smtp.mailfrom= bounces-test770...@sendersrv.com Return-Path: <bounces-test770...@sendersrv.com> Received: from mail2.sendersrv.com (mail2.sendersrv.com. [185.3.229.126]) by mx.google.com with ESMTPS id x14si4818800lfu.581.2022.01.28.07.31.39 for <ysoul8...@gmail.com> (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 28 Jan 2022 07:31:39 -0800 (PST) Received-SPF: pass (google.com: domain of bounces-test770...@sendersrv.com designates 185.3.229.126 as permitted sender) client-ip=185.3.229.126; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; s=sender; d= knowledgemodish.org.uk; h=Message-ID:Subject:From:Reply-To:To:MIME-Version:Content-Type: Content-Transfer-Encoding:Date; i=i...@knowledgemodish.org.uk; bh=JYMTX3Rr+OZICy76j7DTKZeSFGH9xqoJ5IlXE//bwFY=; b=heNp+Lc9pjUvcl7261qiyZUMEyujFujFFM4JWbthE4qeaCwXcCD3ePFEU5I66Iy/eG/bks4nPCE1 tu2ijH5HuwYwBGC89rkxHXqBzSxb3taREXKm7DeIN7J/2/L2LQo6kd5opfdRABl3qQxeH6GXFmCt fQ8Q/8pQw8Z7oKFyJTQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; s=smtp; d= sendersrv.com; h=Message-ID:Subject:From:Reply-To:To:MIME-Version:Content-Type: Content-Transfer-Encoding:Date; bh=JYMTX3Rr+OZICy76j7DTKZeSFGH9xqoJ5IlXE//bwFY=; b=Ra7fdByfHfiOJTQl1izbL8wR7bEBsR/q3tetReHIm798TzvIW4Qgvd4Ovbfrh/qcqzzy95yUocOc Y5zuge0sep0S6zsQjA/5COgoEjtx2W7RAlo59L7nlxtvyNd5zwZQ1QOX1YnnDZ5WaEnNyZboXHth OXukNXbiai1NhnJv3s4= Return-Path: <bounces-test770...@sendersrv.com> Message-ID: <ad4ee4db20cd64959ddf0f9976c24...@app.sender.net> Subject: 𝟸ɴᴅ ᴀᴛᴛᴇᴍᴘᴛ: ʏᴏᴜ ᴀʀᴇ ᴀ ᴡɪɴɴᴇʀ $𝟷𝟶𝟶 ᴄᴏsᴛᴄᴏ ғᴏʀ ʏᴏᴜ #16351 Subject: [Test Email] Costco !! From: Costco Stores <i...@knowledgemodish.org.uk> Reply-To: i...@knowledgemodish.org.uk To: ysoul8...@gmail.com MIME-Version: 1.0 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 28 Jan 2022 18:34:18 -0500 (EST) Date: Fri, 28 Jan 2022 17:31:39 +0200 ---------- Forwarded message --------- From: Costco Stores <i...@knowledgemodish.org.uk> Date: Fri, Jan 28, 2022 at 6:34 PM Subject: 𝟸ɴᴅ ᴀᴛᴛᴇᴍᴘᴛ: ʏᴏᴜ ᴀʀᴇ ᴀ ᴡɪɴɴᴇʀ $𝟷𝟶𝟶 ᴄᴏsᴛᴄᴏ ғᴏʀ ʏᴏᴜ #16351 To: <ysoul8...@gmail.com> [image: Sender] Edgar Vaitkevičius, founder / CEO ed...@sender.net
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