Internet Engineering Task Force H. Stenn Internet-Draft Network Time Foundation Intended status: Standards Track March 14, 2016 Expires: September 15, 2016 Network Time Protocol Last Extension Field draft-stenn-ntp-last-extension-00 Abstract NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions of the NTP Protocol have supported symmetric private key MAC authentication. MACs pre-date the Extension Fields introduced in RFC 5905 [RFC5905], and as the number of Extension Fields grows there is an increasing chance of ambiguity when deciding if the "next" set of data is an Extension Field or a MAC. This proposal defines a new Extension Field which is used to signifiy that it is the last Extension Field in the packet. If present, any subsequent data SHOULD be considered to be a legacy MAC. 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 http://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 September 15, 2016. Copyright Notice Copyright (c) 2016 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 (http://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 Stenn Expires September 15, 2016 [Page 1] Internet-Draft Network Time Protocol Last Extension Field March 2016 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 Language . . . . . . . . . . . . . . . . . . 2 2. The Last Extension Field Extension Field . . . . . . . . . . 2 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. Normative References . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions of the NTP Protocol have supported symmetric private key MAC authentication. MACs pre-date the Extension Fields introduced in RFC 5905 [RFC5905], and as the number of Extension Fields grows there is an increasing chance of ambiguity when deciding if the "next" set of data is an Extension Field or a MAC. This proposal defines a new Extension Field which is used to signifiy that it is the last Extension Field in the packet. If present, any subsequent data SHOULD be considered to be a legacy MAC. 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]. 2. The Last Extension Field Extension Field Now that multiple extension fields are a possibility, and the chance that additional packet data could be an Extension Field or an old- style MAC, having a means to indicate that there are no more Extension Fields in an NTP packet, and any subsequent data MUST be something else, almost certainly an old-style MAC, is a valuable facility. Stenn Expires September 15, 2016 [Page 2] Internet-Draft Network Time Protocol Last Extension Field March 2016 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+-------------------------------+ | Field Type | Field Length | +-------------------------------+-------------------------------+ NTP Extension Field: Last Extension Field Field Type: TBD (Recommendation for IANA: 0x2008 (Last Extension Field, MAC OPTIONAL)) Field Length: 4 Payload: None. Example: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+-------------------------------+ | Field Type (0x2008) | Field Length (0x0004) | +-------------------------------+-------------------------------+ | MAC Key ID | +-------------------------------+-------------------------------+ | Sixteen | +-------------------------------+-------------------------------+ | Octets | +-------------------------------+-------------------------------+ | of | +-------------------------------+-------------------------------+ | MAC | +-------------------------------+-------------------------------+ Example: NTP Extension Field: Last Extension Field 3. Acknowledgements The author wishes to acknowledge the contributions of Joey Saccadonuts. 4. IANA Considerations This memo requests IANA to allocate NTP Extension Field Types 0x0007 (I-Do), 0x2007 (I-Do, MAC OPTIONAL), 0x4007 (I-Do Response), and 0x6007 (I-Do Response, MAC OPTIONAL) for this proposal. Stenn Expires September 15, 2016 [Page 3] Internet-Draft Network Time Protocol Last Extension Field March 2016 5. Security Considerations Additional information TBD 6. 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, . [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, . [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, October 2014, . Author's Address Harlan Stenn Network Time Foundation P.O. Box 918 Talent, OR 97540 US Email: stenn@nwtime.org Stenn Expires September 15, 2016 [Page 4]