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
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This Internet-Draft will expire on January 3, 2019.
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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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