Concise Binary Object Representation (CBOR) Tags for Date
draft-ietf-cbor-date-tag-05

CBOR Working Group                                              M. Jones
Internet-Draft                                                A. Nadalin
Intended status: Standards Track                               Microsoft
Expires: January 2, 2021                                      J. Richter
                                             pdv Financial Software GmbH
                                                            July 1, 2020


       Concise Binary Object Representation (CBOR) Tags for Date
                      draft-ietf-cbor-date-tag-03

Abstract

   The Concise Binary Object Representation (CBOR, RFC 7049) is a data
   format whose design goals include the possibility of extremely small
   code size, fairly small message size, and extensibility without the
   need for version negotiation.

   In CBOR, one point of extensibility is the definition of CBOR tags.
   RFC 7049 defines two tags for time: CBOR tag 0 (RFC 3339 date/time
   string) and tag 1 (Posix "seconds since the epoch").  Since then,
   additional requirements have become known.  This specification
   defines a CBOR tag for an RFC 3339 date text string, for applications
   needing a textual date representation without a time.  It also
   defines a CBOR tag for days since the Posix epoch, for applications
   needing a numeric date representation without a time.  These tags are
   both for representations of calendar dates.  It is intended as the
   reference document for the IANA registration of the CBOR tags
   defined.

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 January 2, 2021.





Jones, et al.            Expires January 2, 2021                [Page 1]


Internet-Draft              CBOR Tag for Date                  July 2020


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
   (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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation and Conventions . . . . . . . . . .   3
   2.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Concise Binary Object Representation (CBOR) Tags
           Registrations . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     4.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   4
   Document History  . . . . . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Concise Binary Object Representation (CBOR) [RFC7049] provides
   for the interchange of structured data without a requirement for a
   pre-agreed schema.  RFC 7049 defines a basic set of data types, as
   well as a tagging mechanism that enables extending the set of data
   types supported via an IANA registry.

   This specification defines a CBOR tag for a text string representing
   a date without a time.  The tagged text string is represented as
   specified by the RFC 3339 [RFC3339] "full-date" production.

   This specification also defines a CBOR tag for an integer
   representing a date without a time.  The tagged integer is an
   unsigned or negative value indicating the number of days since the
   IEEE Std 1003.1, 2013 Edition [POSIX.1] epoch date 1970-01-01.  As an
   implementation note, this value has a constant offset from the
   Modified Julian Date value (which is defined by the Smithsonian



Jones, et al.            Expires January 2, 2021                [Page 2]


Internet-Draft              CBOR Tag for Date                  July 2020


   Astrophysical Observatory as the number of days since November 17,
   1858); this value is the Modified Julian Date minus 40,587.

   Note that since both tags are for dates without times, time zones and
   leap seconds are not applicable to these values.  These tags are both
   for representations of calendar dates.

1.1.  Requirements Notation and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  IANA Considerations

2.1.  Concise Binary Object Representation (CBOR) Tags Registrations

   This section registers the following values in the IANA "Concise
   Binary Object Representation (CBOR) Tags" registry [IANA.cbor-tags].

   o  Tag: 1004 (value requested)
   o  Data Item: UTF-8 text string
   o  Semantics: RFC 3339 full-date string
   o  Reference: [[ this specification ]]

   o  Tag: 100 (ASCII 'd') (value requested)
   o  Data Item: Unsigned or negative integer
   o  Semantics: Number of days since the epoch date 1970-01-01
   o  Reference: [[ this specification ]]

3.  Security Considerations

   The security considerations of RFC 7049 apply; the tags introduced
   here are not expected to raise security considerations beyond those.

   A date, of course, has significant security considerations; these
   include the exploitation of ambiguities where the date is security
   relevant or where the date is used in access control decisions.  When
   using a calendar date for decision making, for example access
   control, it needs to be noted that since calendar dates do not
   represent a specific point in time, the results of the evaluation can
   differ depending upon where the decision is made.  For instance, a
   person may have reached their 21st birthday in Japan while
   simultaneously being a day short of their 21st birthday in Hawaii.





Jones, et al.            Expires January 2, 2021                [Page 3]


Internet-Draft              CBOR Tag for Date                  July 2020


4.  References

4.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

4.2.  Informative References

   [IANA.cbor-tags]
              IANA, "Concise Binary Object Representation (CBOR) Tags",
              <http://www.iana.org/assignments/cbor-tags>.

   [POSIX.1]  IEEE, "The Open Group Base Specifications Issue 7",
              IEEE Std 1003.1, 2013 Edition, 2013,
              <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
              V1_chap04.html#tag_04_15>.

Acknowledgements

   Thanks to Carsten Bormann for supporting creation of this
   specification.  Parts of the explanatory text in this specification
   come from draft-bormann-cbor-time-tag-02.

   Thanks to these people for reviews of the specification: Henk
   Birkholz, Carsten Bormann, Thiago Macieira, Michael Richardson, Jim
   Schaad, Juergen Schoenwaelder, and Dale Worley.

Document History

   [[ to be removed by the RFC Editor before publication as an RFC ]]

   -03




Jones, et al.            Expires January 2, 2021                [Page 4]


Internet-Draft              CBOR Tag for Date                  July 2020


   o  Added statement that these tags are both for representations of
      calendar dates.

   o  Described consequences of using calendar dates in access control
      decisions.

   -02

   o  Addressed working group last call comments, including stating that
      time zones are not applicable to these values.

   -01

   o  Changed "positive or negative" to "unsigned or negative".

   o  Added an implementation note about the relationship to Modified
      Julian Dates.

   -00

   o  Initial working group version based on draft-jones-cbor-date-
      tag-01 with no normative changes.

Authors' Addresses

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   https://self-issued.info/


   Anthony Nadalin
   Microsoft

   Email: tonynad@microsoft.com


   Joerg Richter
   pdv Financial Software GmbH

   Email: joerg.richter@pdv-fs.de









Jones, et al.            Expires January 2, 2021                [Page 5]