NTP Client Data Minimization
draft-dfranke-ntp-data-minimization-00

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Last updated 2016-10-17
Replaced by draft-ietf-ntp-data-minimization
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Network Working Group                                          D. Franke
Internet-Draft                                                    Akamai
Updates: 5905 (if approved)                             October 17, 2016
Intended status: Standards Track
Expires: April 20, 2017

                      NTP Client Data Minimization
                 draft-dfranke-ntp-data-minimization-00

Abstract

   This memo proposes backward-compatible updates to the Network Time
   Protocol to strip unnecessary identifying information from client
   requests and to improve resilience against blind spoofing of
   unauthenticated server responses.

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 April 20, 2017.

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
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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   2
   3.  Client Packet Format  . . . . . . . . . . . . . . . . . . . .   2
   4.  Security and Privacy Considerations . . . . . . . . . . . . .   3
     4.1.  Data Minimization . . . . . . . . . . . . . . . . . . . .   3
     4.2.  Transmit Timestamp Randomization  . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Network Time Protocol packets, as specified by RFC 5905 [RFC5905],
   carry a great deal of information about the state of the NTP daemon
   which transmitted them.  In the case of mode 4 packets (responses
   sent from server to client), as well as in broadcast and symmetric
   modes, most of this information is essential for accurate and
   reliable time synchronizaton.  However, in mode 3 packets (requests
   sent from client to server), these fields serve no purpose.  Server
   implementations never need to inspect them, and they can achieve
   nothing by doing so.  Populating these fields with accurate
   information is harmful to privacy because it allows a passive
   observer to fingerprint clients and track them as they move across
   networks.

   This memo updates RFC 5905 to redact unnecessary data from mode 3
   packets.  It calls for no changes on the server side, and clients
   which implement these updates will remain fully interoperable with
   existing servers.

2.  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].

3.  Client Packet Format

   In every client-mode packet sent by a Network Time Protocol [RFC5905]
   implementation:

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      The first octet, which contains the leap indicator, version
      number, and mode fields, SHALL be set to 0x23 (LI = 0, VN = 4,
      Mode = 3).

      The Transmit Timestamp field SHALL be set uniformly at random,
      generated by a mechanism suitable for cryptographic purposes.
      [RFC4086] provides guidance on the generation of random values.

      All other header fields, specifically the Stratum, Poll,
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