Mailing List Manager (MLM) Transformations
draft-vesely-dmarc-mlm-transform-00

Document Type Active Internet-Draft (individual)
Author Alessandro Vesely 
Last updated 2020-11-16
Replaces draft-dmarc-vesely-mlm-transform
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Network Working Group                                          A. Vesely
Internet-Draft                                             November 2020
Intended status: Informational                                          
Expires: 20 May 2021

               Mailing List Manager (MLM) Transformations
                  draft-vesely-dmarc-mlm-transform-00

Abstract

   The widespread adoption of Domain-based Message Authentication,
   Reporting, and Conformance (DMARC) led Mailing List Managers (MLM) to
   rewrite the From: header field as a workaround.

   This document describes cases where it is possible to revert MLM
   transformations and hence verify DomainKeys Identified Mail (DKIM)
   signatures that were applied at submission time.  For reliable
   results, some compliance is required of all agents involved, author
   domain signers, MLMs, forwarders, and final recipients.

   MLM transformation reversion reduces the DMARC's effects on indirect
   mail flows.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 5 May 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Vesely                     Expires 20 May 2021                  [Page 1]
Internet-Draft             MLM Transformations             November 2020

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terms Definitions . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Revertible Transformations  . . . . . . . . . . . . . . . . .   3
     3.1.  Header Transformations  . . . . . . . . . . . . . . . . .   3
     3.2.  Body Transformations  . . . . . . . . . . . . . . . . . .   4
   4.  Outline of a Reverting Verifier . . . . . . . . . . . . . . .   4
   5.  Actors Roles and Compliance . . . . . . . . . . . . . . . . .   6
     5.1.  Original Signer . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  MLM . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.3.  Verifier  . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Permanent Message Header Field Names  . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  11
     A.1.  Single-part plain text  . . . . . . . . . . . . . . . . .  11
     A.2.  Multipart added . . . . . . . . . . . . . . . . . . . . .  12
     A.3.  Multipart wrapped . . . . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Mailing List Managers (MLMs) can be configured to add a footer and a
   subject tag to the messages that they redistribute.  Although that
   behavior slightly exceeds the very limited set of modifications and
   actions described by Section 3.9.2 of [RFC5321], it is a welcome,
   time-honored tradition.  According to their configuration, the
   modifications they carry out on messages may result in a set of
   stylized transformations that are programmatically revertible.
   Reversion allows to verify DomainKeys Identified Mail (DKIM)
   signatures ([RFC6376]) that were applied before the transformation.

   Domain-based Message Authentication, Reporting, and Conformance
   (DMARC) ([I-D.ietf-dmarc-dmarcbis]) hinges on the alignment of the
   domain in the From: header field with a verified DKIM signature.  For
   that reason, MLMs that transform messages have to rewrite From:.  A
   deed which can be mitigated in some cases.

Vesely                     Expires 20 May 2021                  [Page 2]
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   Mailbox providers can configure their mail submission agents (MSAs)
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