Network Working Group R. Seggelmann
Internet-Draft M. Tuexen
Intended status: Standards Track Muenster Univ. of Applied
Expires: July 31, 2011 Sciences
M. Williams
January 27, 2011
Transport Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension
draft-ietf-tls-dtls-heartbeat-01.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.
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This Internet-Draft will expire on July 31, 2011.
Copyright Notice
Copyright (c) 2011 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
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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 . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. 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].
2. 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;
3. 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 no 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.
4. Heartbeat Request and Response Messages
The Heartbeat protocol messages consist of their type and an
arbitrary payload and padding.
struct {
HeartbeatMessageType type;
uint16 payload_length;
opaque payload[HeartbeatMessage.payload_length];
opaque padding[padding_length];
} HeartbeatMessage;
The length of a HeartbeatMessage in total MUST NOT exceed 2^14 or
max_fragment_length when negotiated as defined in [RFC6066].
type The message type, either heartbeat_request or
heartbeat_response.
payload_length The length of the payload.
payload The payload consists of arbitrary content.
padding The padding is additional arbitrary content which MUST be
ignored by the receiver. The padding_length is
TLSPlaintext.length - payload_length - 3 with TLS and
DTLSPlaintext.length - payload_length - 3 with DTLS.
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.
If payload_length is either shorter than expected and thus indicates
padding in a HeartbeatResponse or exceeds the actual message length
in any message type, an illegal parameter alert MUST be sent in
response.
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5. IANA Considerations
[NOTE to RFC-Editor:
"RFCXXXX" is to be replaced by the RFC number you assign this
document.
]
IANA needs to assign the heartbeat content type (value TBD) from the
TLS ContentType Registry as specified in [RFC5246]. The reference
should be RFCXXXX.
IANA needs to maintain a new registry for Heartbeat Message Types.
Initially IANA needs to assign the heartbeat_request (suggested value
1) and the heartbeat_response (suggested value 2) message type. The
message types are numbers in the range from 0 to 255 (decimal). This
registry uses the Specification Required policy as described in
[RFC5226]. The reference should be RFCXXXX.
IANA needs to assign the heartbeat extension type (value TBD) from
the TLS Extension Type Registry as specified in [RFC5246]. The
reference should be RFCXXXX.
IANA needs to maintain a new registry for Heartbeat Modes. Initially
IANA needs to assign the peer_allowed_to_send (suggested value 1) and
the peer_not_allowed_to_send (suggested value 2) modes. The modes
are numbers in the range from 0 to 255 (decimal). This registry uses
the Specification Required policy as described in [RFC5226]. The
reference should be RFCXXXX.
6. Security Considerations
This document does not add any additional security considerations in
addition to the ones given in [RFC4347] and [RFC5246].
7. Acknowledgments
The authors wish to thank Pasi Eronen, Adam Langley, Eric Rescorla,
Peter Saint-Andre, and Juho Vaehae-Herttua for their invaluable
comments.
8. 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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
Extension Definitions", RFC 6066, January 2011.
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
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Michael Williams
Email: michael.glenn.williams@gmail.com
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