Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Certificate Handling
RFC 8550

Document Type RFC - Proposed Standard (April 2019; No errata)
Obsoletes RFC 5750
Last updated 2019-04-30
Replaces draft-schaad-lamps-rfc5750-bis
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Russ Housley
Shepherd write-up Show (last changed 2017-04-14)
IESG IESG state RFC 8550 (Proposed Standard)
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Responsible AD Eric Rescorla
Send notices to Russ Housley <housley@vigilsec.com>
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Internet Engineering Task Force (IETF)                         J. Schaad
Request for Comments: 8550                                August Cellars
Obsoletes: 5750                                              B. Ramsdell
Category: Standards Track                         Brute Squad Labs, Inc.
ISSN: 2070-1721                                                S. Turner
                                                                   sn3rd
                                                              April 2019

   Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
                          Certificate Handling

Abstract

   This document specifies conventions for X.509 certificate usage by
   Secure/Multipurpose Internet Mail Extensions (S/MIME) v4.0 agents.
   S/MIME provides a method to send and receive secure MIME messages,
   and certificates are an integral part of S/MIME agent processing.
   S/MIME agents validate certificates as described in RFC 5280
   ("Internet X.509 Public Key Infrastructure Certificate and
   Certificate Revocation List (CRL) Profile").  S/MIME agents must meet
   the certificate-processing requirements in this document as well as
   those in RFC 5280.  This document obsoletes RFC 5750.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8550.

Schaad, et al.               Standards Track                    [Page 1]
RFC 8550             S/MIME 4.0 Certificate Handling          April 2019

Copyright Notice

   Copyright (c) 2019 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
   (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.  Code Components extracted from this document must
   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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Schaad, et al.               Standards Track                    [Page 2]
RFC 8550             S/MIME 4.0 Certificate Handling          April 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Conventions Used in This Document . . . . . . . . . . . .   5
     1.3.  Compatibility with Prior Practice of S/MIME . . . . . . .   6
     1.4.  Changes from S/MIME v3 to S/MIME v3.1 . . . . . . . . . .   6
     1.5.  Changes from S/MIME v3.1 to S/MIME v3.2 . . . . . . . . .   7
     1.6.  Changes since S/MIME 3.2  . . . . . . . . . . . . . . . .   8
   2.  CMS Options . . . . . . . . . . . . . . . . . . . . . . . . .   8
     2.1.  Certificate Revocation Lists  . . . . . . . . . . . . . .   9
     2.2.  Certificate Choices . . . . . . . . . . . . . . . . . . .   9
       2.2.1.  Historical Note about CMS Certificates  . . . . . . .   9
     2.3.  Included Certificates . . . . . . . . . . . . . . . . . .  10
   3.  Using Distinguished Names for Internet Mail . . . . . . . . .  11
   4.  Certificate Processing  . . . . . . . . . . . . . . . . . . .  12
     4.1.  Certificate Revocation Lists  . . . . . . . . . . . . . .  13
     4.2.  Certificate Path Validation . . . . . . . . . . . . . . .  13
     4.3.  Certificate and CRL Signing Algorithms, and Key Sizes . .  14
     4.4.  PKIX Certificate Extensions . . . . . . . . . . . . . . .  15
       4.4.1.  Basic Constraints . . . . . . . . . . . . . . . . . .  16
       4.4.2.  Key Usage Extension . . . . . . . . . . . . . . . . .  16
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