Network Time Protocol MAC/Last Extension Fields
draft-stenn-ntp-mac-last-ef-03

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Internet Engineering Task Force                                 H. Stenn
Internet-Draft                                                  D. Mayer
Intended status: Standards Track                 Network Time Foundation
Expires: April 5, 2019                                   October 2, 2018

            Network Time Protocol MAC/Last Extension Fields
                     draft-stenn-ntp-mac-last-ef-03

Abstract

   NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions
   of the NTP Protocol have supported symmetric private key Message
   Authentication Code (MAC) authentication.  MACs were first described
   in Appendix C of RFC 1305 [RFC1305] and are further described in RFC
   5905 [RFC5905].  As the number of Extension Fields grows there is an
   increasing chance of a parsing ambiguity when deciding if the "next"
   set of data is an Extension Field or a legacy MAC.  This proposal
   defines two new Extension Fields to avoid this ambiguity.  One, LAST-
   EF, is used to signify that it is the last Extension Field in the
   packet.  If the LAST-EF is present, any subsequent data MUST be
   considered to be a legacy MAC.  The other, MAC-EF, allows one or more
   MACs to be encapsulated in an Extension Field.  If all parties in an
   association support MAC-EF, the use of a legacy MAC may be avoided.

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
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   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 April 5, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Stenn & Mayer             Expires April 5, 2019                 [Page 1]
Internet-Draft        NTP MAC/Last Extension Fields         October 2018

   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
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   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 Language . . . . . . . . . . . . . . . . . .   2
   2.  The Last Extension Field Extension Field - LAST-EF  . . . . .   3
   3.  MAC Extension Field . . . . . . . . . . . . . . . . . . . . .   4
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions
   of the NTP Protocol have supported symmetric private key Message
   Authentication Code (MAC) authentication.  MACs were first described
   in Appendix C of RFC 1305 [RFC1305] and are further described in RFC
   5905 [RFC5905].  As the number of Extension Fields grows there is an
   increasing chance of a parsing ambiguity when deciding if the "next"
   set of data is an Extension Field or a legacy MAC.  This proposal
   defines two new Extension Fields to avoid this ambiguity.  One, LAST-
   EF, is used to signify that it is the last Extension Field in the
   packet.  If the LAST-EF is present, any subsequent data MUST be
   considered to be a legacy MAC, or if you prefer, any subsequent data
   MUST NOT be considered to be an EF.  The other, MAC-EF, allows one or
   more MACs to be encapsulated in an Extension Field.  If all parties
   in an association support MAC-EF, the use of a legacy MAC may be
   avoided.

1.1.  Requirements Language

   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 RFC 2119 [RFC2119].

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