Brand Indicators for Message Identification (BIMI)
draft-blank-ietf-bimi-01

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Network Working Group                                           S. Blank
Internet-Draft                                              P. Goldstein
Intended status: Experimental                                   Valimail
Expires: 1 February 2021                                   T. Loder, Ed.
                                                    Skye Logicworks, LLC
                                                            T. Zink, Ed.
                                               Zink Magical Contraptions
                                                        M. Bradshaw, Ed.
                                                                Fastmail
                                                            31 July 2020

           Brand Indicators for Message Identification (BIMI)
                        draft-blank-ietf-bimi-01

Abstract

   Brand Indicators for Message Identification (BIMI) permits Domain
   Owners to coordinate with Mail User Agents (MUAs) to display brand-
   specific Indicators next to properly authenticated messages.  There
   are two aspects of BIMI coordination: a scalable mechanism for Domain
   Owners to publish their desired Indicators, and a mechanism for Mail
   Transfer Agents (MTAs) to verify the authenticity of the Indicator.
   This document specifies how Domain Owners communicate their desired
   Indicators through the BIMI Assertion Record in DNS and how that
   record is to be interpreted by MTAs and MUAs.  MUAs and mail-
   receiving organizations are free to define their own policies for
   making use of BIMI data and for Indicator display as they see fit.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 1 February 2021.

Copyright Notice

   Copyright (c) 2020 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
   Provisions Relating to IETF Documents (http://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
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Overview
   3.  Requirements
       3.1.  High-Level Goals
       3.2.  Security
       3.3.  Out of Scope
   4.  Terminology and Definitions
       4.1.  BIMI Assertion
       4.2.  Indicator
       4.3.  Mark Verifying Authority (MVA)
       4.4.  BIMI Evidence Document
       4.5.  Verified Mark Certificate (VMC)
       4.6.  Protocol Client
       4.7.  Verifying Protocol Client
   5.  BIMI DNS Records
       5.1.  MUA Obligations
       5.2.  Assertion Record
             5.2.1.  Declination to Publish
             5.2.2.  Supported Image Formats for l= tag
       5.3.  Selectors
   6.  BIMI Header Fields
       6.1.  BIMI-Selector Header
       6.2.  BIMI-Location Header
       6.3.  BIMI-Indicator Header
       6.4.  Header Signing
   7.  Domain Owner Actions
       7.1.  Determine and Publish Indicator(s) for Use
       7.2.  Publish Assertion Records
       7.3.  Manage multiple uses of the same Indicator(s) within
             a trust boundary
       7.4.  Set the headers on outgoing email as appropriate
   8.  Receiver Actions
       8.1.  Authentication Requirements
       8.2.  Assertion Record Discovery
       8.3.  Indicator Discovery.
       8.4.  Indicator Discovery With Evidence.
       8.5.  Indicator Discovery Without Evidence.
       8.6.  Indicator Validation
       8.7.  Affix BIMI Status to Authentication Results Header
             Field
       8.8.  Handle Existing BIMI-Location and BIMI-Indicator
             Headers
       8.9.  Construct BIMI-Location URI
       8.10.  Construct BIMI-Indicator header
   9.  Security Considerations
       9.1.  Indirect Mail Flows
       9.2.  Lookalike Domains and Copycat Indicators
       9.3.  Large files and buffer overflows
       9.4.  Slow DNS queries
       9.5.  Unaligned Indicators and asserting domains
       9.6.  Unsigned BIMI-Selector Header
       9.7.  CGI scripts in Indicator payload
       9.8.  Metadata in Indicators