DOTS A. Mortensen
Internet-Draft Arbor Networks, Inc.
Intended status: Standards Track October 31, 2016
Expires: May 4, 2017

DDoS Open Threat Signaling over UDP


This document describes the use of the Distributed-Denial-of-Service (DDoS) Open Threat Signaling (DOTS) protocol over UDP [RFC0768].

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Table of Contents

1. Introduction

The DOTS protocol described in [I-D.teague-dots-protocol] defines the protocol message format and message exchanges, but purposely divides the protocol from the transport in order to make DOTS adaptable to arbitrary transports.

This division is meant to simplify the process of bringing DOTS to modern secure transports like QUIC [I-D.hamilton-quic-transport-protocol] and the experimental CurveCP [CURVECP], as well as application-layer protocols like CoAP [RFC7252] and HTTP/2 [RFC7540].

This document defines the most basic option for a DOTS protocol transport, implementing the protocol over UDP, using DTLS1.3 [I-D.rescorla-tls-dtls13] to secure the signaling session.

1.1. Terminology

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 [RFC2119].

Terms used to define entity relationships, transmitted data, and methods of communication are drawn from the terminology defined in [I-D.ietf-dots-requirements].

2. Architecture

The architecture in which the DOTS protocol operates is assumed to be derived from the architectural components and concepts described in [I-D.ietf-dots-architecture].

3. Protocol

This document uses the signal channel message exchanges and message serialization defined in [I-D.teague-dots-protocol], except as specified below.

3.1. Provisioning

3.1.1. DOTS Server Discovery

DOTS server address discovery is implementation-specific, but anticipates methods such as direct configuration (i.e., DOTS server address is manually provided to the DOTS client) and DNS SRV records will be the most common.

3.1.2. Keying Material

A key challenge to deploying DOTS unsurprisingly is provisioning DOTS clients, including the distribution of keying material to DOTS clients to make possible the required mutual authentication of DOTS agents. DOTS over UDP relies on Enrollment over Secure Transport (EST) [RFC7030] to overcome this. EST defines a method of certificate enrollment by which domains operating DOTS servers may provision DOTS clients with all necessary cryptographic keying material, including a private key and certificate with which to authenticate itself.

This document does not specify which EST mechanism the DOTS client uses to achieve initial enrollment. Each mechanism has certain advantages balanced by obvious drawbacks. For example, HTTP-based client authentication for initial enrollment is by far the simplest, allowing DOTS clients to enroll with just a username and one-time-use password, but is also by far the most easily abused. Client authentication using a previously installed certificate improves on HTTP-based client authentication, but requires either a manufacturer-installed certificate, or yet another mechanism to install the client certificate. The EST mechanism for initial enrollment is therefore left to the operators of the DOTS deployment.

3.2. Signal Channel

3.2.1. Initialization

[I-D.teague-dots-protocol] defines a DOTS signal channel initialization message exchange in which the DOTS client initiates contact with the DOTS server by connecting to the DOTS server on port 4646, but leaves instantiation of the signal channel’s security context up to DOTS transport documents.

DOTS over UDP uses DTLS1.3 [I-D.rescorla-tls-dtls13] to secure the signal channel and provide the requisite confidentiality, integrity, and authenticity for messages exchanged between DOTS agents [I-D.ietf-dots-requirements]. Signal channel initialization assumes the presence of a DOTS client certificate and DOTS server certificate obtained through EST as described in Section 3.1 above.

As described in [I-D.teague-dots-protocol], the DOTS client begins creation of the security context for the the signaling session after successfully connecting to the DOTS server on port 4646. The DOTS over UDP client makes that connection over UDP.

Once connected, DOTS over UDP clients SHOULD attempt session resumption through use of pre-shared keys (PSKs) created during previous signaling sessions with the DOTS server. Session resumption using PSKs from a previous DTLS session is described in [I-D.ietf-tls-tls13].

If a DOTS client does not have a PSK from a previous signaling session, or if the PSK is expired or otherwise invalid, the DOTS client will fallback to a full DTLS1.3 handshake, using the private key and certificates obtained through EST at the time of client provisioning. After performing a full DTLS handshake, the DOTS server SHOULD send a NewSessionTicket message to the client after receiving the client’s Finished message, as described in [I-D.ietf-tls-tls13]. The DOTS client SHOULD cache the PSK identity and use it for future session resumption.

Once the DTLS handshake is complete, the DOTS signal channel security context is established, the DOTS over UDP client proceeds to establish the signaling session by sending a channel initiatlization method, as described in [I-D.teague-dots-protocol].

3.2.2. Messaging

Once the signal channel security context is established through DTLS and the signaling session is active, all messaging proceeds as defined in [I-D.teague-dots-protocol], relying on DTLS to provide the requisite channel security. Heartbeats

DOTS over UDP purposely avoids using DTLS heartbeats [RFC6520] to maintain the signaling session, depending instead on DOTS protocol heartbeats to track signal session health. DTLS Alerts

DOTS over UDP is subject to any condition triggering DTLS Alert messages as described in [I-D.rescorla-tls-dtls13]. Should the alert lead to connection termination, the DOTS over UDP MAY attempt to reestablish the

3.3. Data Channel

DOTS over UDP adopts the data channel as specified in [I-D.teague-dots-protocol] with modification or extension.

4. Congestion Control Considerations

DOTS over UDP is subject to the congestion control discussion in [RFC5405].

5. Security Considerations

[I-D.teague-dots-protocol] describes general DOTS protocol security considerations. Additionally, all security considerations in [I-D.rescorla-tls-dtls13] apply to DOTS over UDP.

When provisioning DOTS clients using EST, all considerations in [RFC7030] also apply to DOTS over UDP.

6. Contributors

Nik Teague Verisign, Inc.

7. References

7.1. Normative References

[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines for Application Designers", BCP 145, RFC 5405, DOI 10.17487/RFC5405, November 2008.
[RFC6520] Seggelmann, R., Tuexen, M. and M. Williams, "Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension", RFC 6520, DOI 10.17487/RFC6520, February 2012.
[RFC7030] Pritikin, M., Yee, P. and D. Harkins, "Enrollment over Secure Transport", RFC 7030, DOI 10.17487/RFC7030, October 2013.
[RFC7540] Belshe, M., Peon, R. and M. Thomson, "Hypertext Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI 10.17487/RFC7540, May 2015.
[I-D.ietf-dots-architecture] Mortensen, A., Andreasen, F., Reddy, T.,, c., Compton, R. and N. Teague, "Distributed-Denial-of-Service Open Threat Signaling (DOTS) Architecture", Internet-Draft draft-ietf-dots-architecture-00, July 2016.
[I-D.ietf-dots-requirements] Mortensen, A., Moskowitz, R. and T. Reddy, "Distributed Denial of Service (DDoS) Open Threat Signaling Requirements", Internet-Draft draft-ietf-dots-requirements-03, October 2016.
[I-D.ietf-tls-tls13] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", Internet-Draft draft-ietf-tls-tls13-18, October 2016.
[I-D.rescorla-tls-dtls13] Rescorla, E. and H. Tschofenig, "The Datagram Transport Layer Security (DTLS) Protocol Version 1.3", Internet-Draft draft-rescorla-tls-dtls13-00, October 2016.

7.2. Informative References

[RFC7252] Shelby, Z., Hartke, K. and C. Bormann, "The Constrained Application Protocol (CoAP)", RFC 7252, DOI 10.17487/RFC7252, June 2014.
[I-D.hamilton-quic-transport-protocol] Hamilton, R., Iyengar, J., Swett, I. and A. Wilk, "QUIC: A UDP-Based Multiplexed and Secure Transport", Internet-Draft draft-hamilton-quic-transport-protocol-00, July 2016.
[CURVECP] Bernstein, D., "CurveCP: Usable security for the Internet", 2014.

Author's Address

Andrew Mortensen Arbor Networks, Inc. 2727 S. State St Ann Arbor, MI, 48104 United States EMail: