Network Working Group                                      R. Seggelmann
Internet-Draft                                                 M. Tuexen
Intended status: Standards Track      Muenster Univ. of Applied Sciences
Expires: December 20, 2010                                   M. Williams
                                                           June 18, 2010


  Transport Layer Security (TLS) and Datagram Transport Layer Security
                       (DTLS) Heartbeat Extension
                  draft-ietf-tls-dtls-heartbeat-00.txt

Abstract

   This document describes the Heartbeat Extension for the Transport
   Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
   protocol.

   The Heartbeat Extension provides a new protocol for TLS/DTLS allowing
   the usage of keep-alive functionality without performing a
   renegotiation and a basis for path maximum transmission unit (PMTU)
   discovery for DTLS.

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 December 20, 2010.

Copyright Notice

   Copyright (c) 2010 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Heartbeat Hello Extension . . . . . . . . . . . . . . . . . . . 3
   3.  Heartbeat Protocol  . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Heartbeat Request and Response Messages . . . . . . . . . . . . 5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6































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.  Introduction

1.1.  Overview

   This document describes the Heartbeat Extension for the Transport
   Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
   protocols, as defined in [RFC5246] and [RFC4347].

   DTLS is designed to secure traffic running on top of unreliable
   transport protocols.  Usually such protocols have no session
   management.  The only mechanism available at the DTLS layer to figure
   out if a peer is still alive is performing a costly renegotiation.
   If the application uses unidirectional traffic there is no other way.
   Furthermore, DTLS needs to perform path maximum transmission unit
   (PMTU) discovery but has no specific message type to realize it
   without affecting user message transfer.

   TLS is based on reliable protocols but there is not necessarily a
   feature available to keep the connection alive without continuous
   data transfer.

   The Heartbeat Extension as described in this document overcomes these
   limitations.  The user can use the new HeartbeatRequest message which
   has to be answered by the peer with a HeartbeartResponse immediately.
   To perform PMTU discovery HeartbeatRequest messages containing
   padding can be used as described in [RFC4821] for the Stream Control
   Transmission Protocol (SCTP) using the padding chunk (PAD-chunk)
   defined in [RFC4820].

1.2.  Conventions

   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].


.  Heartbeat Hello Extension

   The support of Heartbeats is indicated with Hello Extensions.  A peer
   can not only indicate that its implementation supports Heartbeats, it
   can also choose whether it is willing to receive and respond or only
   to send them.  This decision can be changed with every renegotiation.
   HeartbeatRequests MUST NOT be sent to a peer denying acceptance.








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   enum {
      peer_allowed_to_send(1),
      peer_not_allowed_to_send(2),
      (255)
   } HeartbeatMode;

   struct {
      HeartbeatMode mode;
   } HeartbeatExtension;


.  Heartbeat Protocol

   The Heartbeat protocol is a new protocol on top of the Record Layer.
   The protocol itself consists of two message types: HeartbeatRequest
   and HeartbeatResponse.

   enum {
      heartbeat_request(1),
      heartbeat_response(2),
      (255)
   } HeartbeatMessageType;

   Like the ChangeCipherSpec message, a HeartbeatRequest message can
   arrive at any time during the lifetime of a connection.  Whenever a
   HeartbeatRequest message is received, it has to be answered with a
   corresponding HeartbeatResponse message immediately.

   However, a HeartbeatRequest message SHOULD NOT be sent during
   handshakes.

   There MUST NOT be more than one HeartbeatRequest message in flight at
   a time.

   When using DTLS, HeartbeatRequest messages MUST be retransmitted
   using the simple timeout and retransmission scheme DTLS uses for
   flights.  In particular, after a number of retransmissions without
   receiving a corresponding HeartbeatResponse message having the
   expected payload the DTLS connection SHOULD be terminated.  The
   threshold used for this SHOULD be the same as for DTLS handshake
   messages.  Please note, that after the timer supervising a
   HeartbeatRequest messages expires, this message is not longer
   considered in flight.  Therefore the HeartbeatRequest message is
   eligible for retransmission.

   When using TLS, HeartbeatRequest messages only need to be sent once.
   The transport layer will handle retransmissions.  If no corresponding
   HeartbeatResponse message has been received after a user configured



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   amount of time, the TLS connection SHOULD be terminated.


.  Heartbeat Request and Response Messages

   The Heartbeat protocol messages consist of their type and an
   arbitrary payload and padding.

   struct {
      HeartbeatMessageType type;
      opaque payload<0..2^14-5>;
      opaque padding<0..2^14-5>;
   } HeartbeatMessage;

   The length of payload and padding in total MUST NOT exceed 2^14-5
   bytes.

   When a HeartbeatRequest message is received, a corresponding
   HeartbeatResponse message MUST be sent carrying an exact copy of the
   payload of the HeartbeatRequest.  The padding of the received
   HeartbeatRequest message MUST be ignored.  It MUST NOT be included in
   the HeartbeatResponse message, i.e. the padding field of the
   HeartbeatResponse message MUST have a length of zero.

   If a received HeartbeatResponse message does not contain the expected
   payload the message MUST be discarded silently.  If it does contain
   the expected payload the retransmission timer MUST be stopped.


.  IANA Considerations

   The extension, content and message types have to be assigned by IANA.


.  Security Considerations

   This document does not add any additional security considerations in
   addition to the ones given in [RFC4347] and [RFC5246].


.  Acknowledgments

   The authors wish to thank Pasi Eronen, Eric Rescorla, and Peter
   Saint-Andre for their invaluable comments.


.  References




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8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security", RFC 4347, April 2006.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

8.2.  Informative References

   [RFC4820]  Tuexen, M., Stewart, R., and P. Lei, "Padding Chunk and
              Parameter for the Stream Control Transmission Protocol
              (SCTP)", RFC 4820, March 2007.

   [RFC4821]  Mathis, M. and J. Heffner, "Packetization Layer Path MTU
              Discovery", RFC 4821, March 2007.


Authors' Addresses

   Robin Seggelmann
   Muenster University of Applied Sciences
   Stegerwaldstr. 39
   48565 Steinfurt
   DE

   Email: seggelmann@fh-muenster.de


   Michael Tuexen
   Muenster University of Applied Sciences
   Stegerwaldstr. 39
   48565 Steinfurt
   DE

   Email: tuexen@fh-muenster.de


   Michael Williams

   Email: michael.glenn.williams@gmail.com







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