NTP Client Data Minimization
draft-ietf-ntp-data-minimization-04
Network Working Group D. Franke
Internet-Draft Akamai
Updates: 5905 (if approved) A. Malhotra
Intended status: Standards Track Boston University
Expires: September 26, 2019 March 25, 2019
NTP Client Data Minimization
draft-ietf-ntp-data-minimization-04
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
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 26, 2019.
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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 . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Network Time Protocol (NTP) 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 (mode
5) and symmetric peering modes (mode 1/2), most of this information
is essential for accurate and reliable time synchronizaton. However,
in mode 3 packets (requests sent from client to server), most of
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 of
clients 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. This is a fully backwards-compatible proposal. 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, SHOULD be set to 0x23 (LI = 0, VN = 4,
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