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Internet Engineering Task Force                                 H. Stenn
Internet-Draft                                                  D. Mills
Intended status: Standards Track                          P. Prindeville
Expires: January 3, 2019                         Network Time Foundation
                                                            July 2, 2018


               Network Time Protocol: Secure Network Time
                 draft-stenn-ntp-secure-network-time-00

Abstract

   The proposal specifies a means for NTP instances that can establish a
   TCP connection between themselves to create secure ephemeral keys.
   With the known weaknesses of the public-key security protocol,
   Autokey, which is defined by RFC 5906 [RFC5906], a replacement for
   Autokey that supports at least Client/Server and Symmetric modes must
   be provided.

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 3, 2019.

Copyright Notice

   Copyright (c) 2018 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



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   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.  Secure Network Time . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   From almost the beginning, NTP has provided a mechanism to
   authenticate an NTP packet.  To date, that mechanism is a Message
   Authentication Code, or MAC.  The MAC is comprised of two subfields,
   a 32-bit keyID and a signature.  A keyID with a value between 1 and
   65535, inclusive, is a symmetric key.  A keyID with a value greater
   than 65535 is not provided by the symmetric key file, and has
   traditionally been negotiated ephemerally, with Autokey, defined by
   RFC 5906 [RFC5906], being one example.

   The mechanism by which keys are exchanged between NTP instance can be
   thought of as a black-box exchange.  One of these black-box key
   exchange mechanisms is "the way the ntp.keys file containing
   symmetric keys is distributed."  Another way keys have been exchaned
   is via Autokey.

   This Secure Network Time proposal uses the NTP TCP Services mechanism
   to perform key exchange, follwed by negotiation of a keyID, a hash
   algorithm, and a secret key over a TLS connection.  Once this has
   been done, each participant can use the keyID, hash algorithm, and
   secret key to provide MAC protection for NTP packets, using ephemeral
   keys that can be re-negotiated as-needed.

   Should additional security measures be desired, for example using a
   cookie as additional replay prevention, that can be easily provided.

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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2.  Secure Network Time

   Secure Network Time uses "NTP TCP Services" to perform key exchange
   over a TLS connection, followed by an agreement on a keyID, hash
   algorithm, and a secret.  With the secure communication of a keyID, a
   cryptographically strong hash algorithm, and a secret of sufficient
   strength, we have an ephemeral key exchange mechanism that provides
   MAC authentication for NTP packets.

3.  IANA Considerations

   TBD

4.  Security Considerations

   Additional information TBD

5.  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>.

   [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,
              <https://www.rfc-editor.org/info/rfc5905>.

   [RFC5906]  Haberman, B., Ed. and D. Mills, "Network Time Protocol
              Version 4: Autokey Specification", RFC 5906,
              DOI 10.17487/RFC5906, June 2010,
              <https://www.rfc-editor.org/info/rfc5906>.

Authors' Addresses

   Harlan Stenn
   Network Time Foundation
   P.O. Box 918
   Talent, OR  97540
   US

   Email: stenn@nwtime.org








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   David L. Mills
   Network Time Foundation
   P.O. Box 918
   Talent, OR  97540
   US

   Email: mills@udel.edu


   Philip Prindeville
   Network Time Foundation
   P.O. Box 918
   Talent, OR  97540
   US

   Email: prindeville@ntp.org



































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