A Message Header to Identify Subscription Form Mail
draft-levine-mailbomb-header-01

Versions: 00 01                                                         
Network Working Group                                          J. Levine
Internet-Draft                                      Taughannock Networks
Updates: 6376 (if approved)                              October 5, 2017
Intended status: Informational
Expires: April 8, 2018


          A Message Header to Identify Subscription Form Mail
                    draft-levine-mailbomb-header-01

Abstract

   Many organizations have web forms that provoke an e-mail confirmation
   to the e-mail address provided in the form.  Malicious entities do
   bulk form submissions with forged addresses, resulting in mail floods
   to the holders of those addresses.  This document defines a message
   header to identify mail sent in response to web forms, so that
   recipient mail systems can better recognize and mitigate the mail
   floods.

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 April 8, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  The Form-Sub header field . . . . . . . . . . . . . . . . . .   3
   4.  Mail flood enhanced status code . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Provisional Message Header Registry . . . . . . . . . . .   4
     6.2.  Enhanced Status Codes . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Appendix A.  Change log . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Discussion Venue:    For the time being, discussion about this draft
      is directed to the collaboration@mailman.m3aawg.org [1] mailing
      list.

   Many organizations have web forms that provoke an e-mail confirmation
   to the e-mail address provided in the form.  Malicious entities
   submit multiple forms with forged addresses, resulting in mail floods
   to those addresses.  We define a message header that identifies mail
   sent in response to web forms, so that recipient mail systems can
   better recognize and mitigate the mail floods.

   Mail systems that recognize a mail flood may defer or reject the
   mail.  We also define an SMTP enhanced status code that a mail system
   can use in a message rejection SMTP reponse to alert the sending
   system that the message was rejected due to being part of a mail
   flood.

2.  Conventions

   The terms Message Submission Agent (MSA) and Message Transfer Agent
   (MTA) are defined as in [RFC5598].

   The ABNF [RFC5234] terms CRLF, FWS, and fields are imported from
   [RFC5322].




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3.  The Form-Sub header field

   A MSA or an initial MTA adds a Form-Sub header field to indicate that
   the message was sent in response to a web form submission.  The
   header consists of a semicolon-separated list of tag=value pairs.
   The first tag-value pair is "v=1" to indicate that the header uses
   the initial version of this specification.  Receivers should ignore
   Form-Sub headers with a v= tag that indicates an unknown version.
   Subsequent tag-value pairs are optional, and receivers should ignore
   pairs with unknown tags.

   The tags ip4 or ip6 contain the IPv4 or IPv6 address, respectively,
   from which the web form was submitted.  The address may be partially
   redacted for privacy reasons, by replacing groups of digits with the
   letter "x", for example, 198.51.x.x or 2001:DB8::x or
   x::1234:abcd:5678:ef01.  If the sender cannot determine the
   submitting IP address, it can include "ip=none".  The goal of
   including the IP address is to help receiving mail systems recognize
   when a cluster of messages was provoked by the same submitter.  Using
   "x" rather than a hash of the the address provides a redaction that
   cannot be reversed but still can be correlated among multiple
   messages.

       ABNF:

       fields =/ "Form-Sub:" FWS "v=1" *(FWS ";" FWS fsarg) CRLF

       fsarg = "ip4=" ip4redacted
       ip4redacted = IPv4 address with parts optionally replaced by "x"

       fsarg =/ "ip6=" ip6redacted
       ip6redacted = IPv6 address with parts optionally replaced by "x"

       fsarg =/ "ip=none"

       fsarg =/ x-fsarg

       x-fsarg =/ ALPHA *(ALPHA / DIGIT) "=" tagdata
       tagdata = string of VCHAR excluding quote and semicolon

   The Form-Sub header should be included within the set of the headers
   signed by any DKIM [RFC6376] signature headers.

4.  Mail flood enhanced status code

   A mail receiver may choose to defer or reject mail that it recognizes
   as part of a mail flood.  It can include the enhanced status code




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   X.7.28 to indicate that the rejection is due to the message being
   part of a mail flood that includes Form-Sub headers.

   A sender would typically interpret the code as a strong hint that
   their systems are being abused, so they should mitigate the abuse to
   stop the mail flood.

5.  Security Considerations

   IP addresses are sometimes considered to be personally identifable
   information.  This specification allows partially redacted addresses
   as a compromise to avoid identifying individual persons, while still
   providing receivers a hint to recognize bulk submissions by the same
   party.

   The Form-Sub header discloses information from a sender to a
   receiver, and the X.7.28 enhanced status code discloses information
   from a receiver to a sender that they would not otherwise have.  If
   one party suspects the other is malicious, e.g., a receiver fears
   that a sender is probing to see what its mail volume limits are, it
   might not include the header or the status code for the possibly
   malicious other party.

6.  IANA Considerations

   IANA has updated registries as follows.

6.1.  Provisional Message Header Registry

   The following value has been added to the Provisional Message Header
   Registry

   +------------------+----------+----------+--------+-----------------+
   |   Header Field   | Template | Protocol | Status | Reference       |
   |       name       |          |          |        |                 |
   +------------------+----------+----------+--------+-----------------+
   |     Form-Sub     | .        | mail     | .      | (this document) |
   +------------------+----------+----------+--------+-----------------+

         Table 1: Provisional Message Header Registry Added Value

6.2.  Enhanced Status Codes

   The following value has been added to the Enhanced Status Codes
   Enumerated Status Codes Registry






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   +------+-------+--------+---------+--------+--------+---------------+
   | Code | Sampl | Associ | Descrip | Refere | Submit | Change        |
   |      | e     | ated   | tion    | nce    | ter    | Controller    |
   |      | Text  | Basic  |         |        |        |               |
   |      |       | Status |         |        |        |               |
   |      |       | Code   |         |        |        |               |
   +------+-------+--------+---------+--------+--------+---------------+
   | X.7. | Mail  | .      | The     | [this  | J.     | standards@tau |
   |  28  | flood |        | message | docume | Levine | gh.com        |
   |      | detec |        | appears | nt]    |        |               |
   |      | ted   |        | to be   |        |        |               |
   |      |       |        | part of |        |        |               |
   |      |       |        | a mail  |        |        |               |
   |      |       |        | flood   |        |        |               |
   |      |       |        | of      |        |        |               |
   |      |       |        | similar |        |        |               |
   |      |       |        | abusive |        |        |               |
   |      |       |        | message |        |        |               |
   |      |       |        | s.      |        |        |               |
   +------+-------+--------+---------+--------+--------+---------------+

           Table 2: Enunerated Status Codes Registry Added Value

7.  Acknowledgments

   Kurt Andersen and the M3AAWG Collaboration Committee provided the
   good parts.

8.  References

8.1.  Normative References

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/info/rfc5322>.

   [RFC5598]  Crocker, D., "Internet Mail Architecture", RFC 5598,
              DOI 10.17487/RFC5598, July 2009,
              <https://www.rfc-editor.org/info/rfc5598>.







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   [RFC6376]  Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
              "DomainKeys Identified Mail (DKIM) Signatures", STD 76,
              RFC 6376, DOI 10.17487/RFC6376, September 2011,
              <https://www.rfc-editor.org/info/rfc6376>.

8.2.  URIs

   [1] mailto:collaboration@mailman.m3aawg.org

Appendix A.  Change log

   00 to 01:  Fix ABNF to allow arbitrary tags.  Fix typos.  .

Author's Address

   John Levine
   Taughannock Networks
   PO Box 727
   Trumansburg, NY  14886

   Phone: +883.5100.01196712
   Email: standards@taugh.com





























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