Extensions to Automatic Certificate Management Environment for end user S/MIME certificates
draft-ietf-acme-email-smime-02
Network Working Group A. Melnikov
Internet-Draft Isode Ltd
Intended status: Informational March 4, 2018
Expires: September 5, 2018
Extensions to Automatic Certificate Management Environment for end user
S/MIME certificates
draft-ietf-acme-email-smime-02
Abstract
This document specifies identifiers and challenges required to enable
the Automated Certificate Management Environment (ACME) to issue
certificates for use by email users that want to use S/MIME.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. Use of ACME for issuing end user S/MIME certificates . . . . 2
4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
6. Security Considerations . . . . . . . . . . . . . . . . . . . 3
7. Normative References . . . . . . . . . . . . . . . . . . . . 3
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
[I-D.ietf-acme-acme] is a mechanism for automating certificate
management on the Internet. It enables administrative entities to
prove effective control over resources like domain names, and
automates the process of generating and issuing certificates.
This document describes an extension to ACME for use by S/MIME.
Section 3 defines extensions for issuing end user S/MIME [RFC5751]
certificates.
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Use of ACME for issuing end user S/MIME certificates
[I-D.ietf-acme-acme] defines "dns" Identifier Type that is used to
verify that a particular entity has control over a domain or specific
service associated with the domain. In order to be able to issue
end-user S/MIME certificates, ACME needs a new Identifier Type that
proves ownership of an email address.
This document defines a new Identifier Type "email" which corresponds
to an (all ASCII) email address [RFC5321] or Internationalized Email
addresses [RFC6531]. This can be used with S/MIME or other similar
service that requires posession of a certificate tied to an email
address.
A new challenge type "email-reply-00" is used with "email" Identifier
Type, which provides proof that an ACME client has control over an
email address:
1. ACME server generates a "challenge" email message with the
subject "ACME: <token-part1>", where <token-part1> is the
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base64url encoded first part of the token, which contains at
least 64 bit of entropy. The challenge email message MUST have a
single text/plain MIME body part [RFC2045]. The second part of
the token (token-part2, which also contains at least 64 bit of
entropy) is returned over HTTPS to the ACME client. ACME client
concatenates "token-part1" and "token-part2" to create "token",
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