draft-ietf-acme-email-smime-01.txt   draft-ietf-acme-email-smime-02.txt 
Network Working Group A. Melnikov Network Working Group A. Melnikov
Internet-Draft Isode Ltd Internet-Draft Isode Ltd
Intended status: Informational October 29, 2017 Intended status: Informational March 4, 2018
Expires: May 2, 2018 Expires: September 5, 2018
Extensions to Automatic Certificate Management Environment for end user Extensions to Automatic Certificate Management Environment for end user
S/MIME certificates S/MIME certificates
draft-ietf-acme-email-smime-01 draft-ietf-acme-email-smime-02
Abstract Abstract
This document specifies identifiers and challenges required to enable This document specifies identifiers and challenges required to enable
the Automated Certificate Management Environment (ACME) to issue the Automated Certificate Management Environment (ACME) to issue
certificates for use by email users that want to use S/MIME. certificates for use by email users that want to use S/MIME.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 2, 2018. This Internet-Draft will expire on September 5, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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proves ownership of an email address. proves ownership of an email address.
This document defines a new Identifier Type "email" which corresponds This document defines a new Identifier Type "email" which corresponds
to an (all ASCII) email address [RFC5321] or Internationalized Email to an (all ASCII) email address [RFC5321] or Internationalized Email
addresses [RFC6531]. This can be used with S/MIME or other similar addresses [RFC6531]. This can be used with S/MIME or other similar
service that requires posession of a certificate tied to an email service that requires posession of a certificate tied to an email
address. address.
A new challenge type "email-reply-00" is used with "email" Identifier A new challenge type "email-reply-00" is used with "email" Identifier
Type, which provides proof that an ACME client has control over an Type, which provides proof that an ACME client has control over an
email address: [[Very rough outline follows]] email address:
1. ACME server generates a "challenge" email message with the 1. ACME server generates a "challenge" email message with the
subject "ACME: <token-part1>", where <token-part1> is the subject "ACME: <token-part1>", where <token-part1> is the
base64url encoded first part of the token, which contains at base64url encoded first part of the token, which contains at
least 64 bit of entropy. The challenge email message MUST have a least 64 bit of entropy. The challenge email message MUST have a
single text/plain MIME body part [RFC2045]. The second part of single text/plain MIME body part [RFC2045]. The second part of
the token (token-part2, which also contains at least 64 bit of the token (token-part2, which also contains at least 64 bit of
entropy) is returned over HTTPS to the ACME client. ACME client entropy) is returned over HTTPS to the ACME client. ACME client
concatenates "token-part1" and "token-part2" to create "token", concatenates "token-part1" and "token-part2" to create "token",
calculates key-authz (as per Section 8.1 of calculates key-authz (as per Section 8.1 of
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of a response email message containing a single text/plain MIME of a response email message containing a single text/plain MIME
body part [RFC2045]. body part [RFC2045].
4. Open Issues 4. Open Issues
[[This section should be empty before publication]] [[This section should be empty before publication]]
1. Do we need to handle text/html or multipart/alternative in email 1. Do we need to handle text/html or multipart/alternative in email
challenge? Simplicity suggests "no". challenge? Simplicity suggests "no".
2. Do we need a proof that ACME client can submit email on behalf of
the user, not just read the challenge using IMAP? Alexey:
probably yes, because intercepting somebody's email is easier
than generating email on the user's behalf.
5. IANA Considerations 5. IANA Considerations
IANA is requested to register a new Identifier Type "email" which IANA is requested to register a new Identifier Type "email" which
corresponds to an (all ASCII) email address [RFC5321]. corresponds to an (all ASCII) email address [RFC5321].
And finally, IANA is requested to register the following ACME And finally, IANA is requested to register the following ACME
challenge types that are used with Identifier Type "email": "email- challenge types that are used with Identifier Type "email": "email-
reply". The reference for it is this document. reply". The reference for it is this document.
6. Security Considerations 6. Security Considerations
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[RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, DOI 10.17487/RFC5751, January Specification", RFC 5751, DOI 10.17487/RFC5751, January
2010, <https://www.rfc-editor.org/info/rfc5751>. 2010, <https://www.rfc-editor.org/info/rfc5751>.
[RFC6531] Yao, J. and W. Mao, "SMTP Extension for Internationalized [RFC6531] Yao, J. and W. Mao, "SMTP Extension for Internationalized
Email", RFC 6531, DOI 10.17487/RFC6531, February 2012, Email", RFC 6531, DOI 10.17487/RFC6531, February 2012,
<https://www.rfc-editor.org/info/rfc6531>. <https://www.rfc-editor.org/info/rfc6531>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
Author's Address Author's Address
Alexey Melnikov Alexey Melnikov
Isode Ltd Isode Ltd
14 Castle Mews 14 Castle Mews
Hampton, Middlesex TW12 2NP Hampton, Middlesex TW12 2NP
UK UK
EMail: Alexey.Melnikov@isode.com EMail: Alexey.Melnikov@isode.com
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