draft-ietf-tsvwg-dtls-for-sctp-00.txt   draft-ietf-tsvwg-dtls-for-sctp-01.txt 
Network Working Group M. Tuexen Network Working Group M. Tuexen
Internet-Draft R. Seggelmann Internet-Draft R. Seggelmann
Intended status: Standards Track Muenster Univ. of Applied Sciences Intended status: Standards Track Muenster Univ. of Applied Sciences
Expires: April 25, 2009 E. Rescorla Expires: January 9, 2010 E. Rescorla
RTFM, Inc. RTFM, Inc.
October 22, 2008 July 8, 2009
Datagram Transport Layer Security for Stream Control Transmission Datagram Transport Layer Security for Stream Control Transmission
Protocol Protocol
draft-ietf-tsvwg-dtls-for-sctp-00.txt draft-ietf-tsvwg-dtls-for-sctp-01.txt
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Abstract Abstract
This document describes the usage of the Datagram Transport Layer This document describes the usage of the Datagram Transport Layer
Security (DTLS) protocol over the Stream Control Transmission Security (DTLS) protocol over the Stream Control Transmission
Protocol (SCTP). Protocol (SCTP).
The user of DTLS over SCTP can take advantage of all features The user of DTLS over SCTP can take advantage of all features
provided by SCTP and its extensions, especially support of provided by SCTP and its extensions, especially support of
o multiple streams to avoid head of line blocking.
o multi-homing to provide network level fault tolerance. o multi-homing to provide network level fault tolerance.
o multiple streams to avoid head of line blocking.
o unordered delivery. o unordered delivery.
o dynamic reconfiguration of streams.
o partially reliable data transfer. o partially reliable data transfer.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. DTLS considerations . . . . . . . . . . . . . . . . . . . . . . 4 3. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . . 5
4. SCTP considerations . . . . . . . . . . . . . . . . . . . . . . 5 4. SCTP Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 8
1. Introduction 1. Introduction
1.1. Overview 1.1. Overview
This document describes the usage of the Datagram Transport Layer This document describes the usage of the Datagram Transport Layer
Security (DTLS) protocol, as defined in [RFC4347], over the Stream Security (DTLS) protocol, as defined in [RFC4347], over the Stream
Control Transmission Protocol (SCTP), as defined in [RFC4960]. Control Transmission Protocol (SCTP), as defined in [RFC4960].
TLS is designed to run on top of a byte-stream oriented transport TLS is designed to run on top of a byte-stream oriented transport
skipping to change at page 4, line 12 skipping to change at page 5, line 12
Connection: A TLS connection. Connection: A TLS connection.
Session: A TLS session. Session: A TLS session.
Stream: A unidirectional stream of an SCTP association. It is Stream: A unidirectional stream of an SCTP association. It is
uniquely identified by a stream identifier. uniquely identified by a stream identifier.
1.3. Abbreviations 1.3. Abbreviations
DTLS: Datagram Transport Layer Security DTLS: Datagram Transport Layer Security.
MTU: Maximum Transmission Unit MTU: Maximum Transmission Unit.
SCTP: Stream Control Transmission Protocol PPID: Payload Protocol Identifier.
TCP: Transmission Control Protocol SCTP: Stream Control Transmission Protocol.
TLS: Transport Layer Security TCP: Transmission Control Protocol.
TLS: Transport Layer Security.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. DTLS considerations 3. DTLS Considerations
3.1. Message sizes 3.1. Message Sizes
DTLS limits the user message size to the current Path MTU. This DTLS limits the DTLS user message size to the current Path MTU minus
limit SHOULD be increased to 2^14 Bytes for DTLS/SCTP. the header sizes. This limit SHOULD be increased to 2^14 Bytes for
DTLS over SCTP.
3.2. Message fragmentation 3.2. Message Fragmentation
The DTLS layer MUST NOT perform message fragmentation. The SCTP The DTLS layer MUST NOT perform message fragmentation. The SCTP
layer will perform this task. Thus the supported maximum length of layer will perform this task. Thus the supported maximum length of
SCTP user messages MUST be at least 2^14 + 2048 + 5 = 18437 bytes. SCTP user messages MUST be at least 2^14 + 2048 + 5 = 18437 bytes.
Every DTLS message MUST be handled as one user message for SCTP. Every DTLS message MUST be handled as one SCTP user message.
3.3. Replay detection 3.3. Replay Detection
Replay detection of DTLS MUST NOT be used. Replay detection of DTLS MUST NOT be used.
3.4. Path MTU Discovery 3.4. Path MTU Discovery
Path MTU discovery of DTLS MUST NOT be used. Path MTU discovery of DTLS MUST NOT be used.
3.5. Retransmission of Messages 3.5. Retransmission of Messages
DTLS procedures for retransmissions MUST NOT be used. DTLS procedures for retransmissions MUST NOT be used.
4. SCTP considerations 4. SCTP Considerations
4.1. Stream usage 4.1. Payload Protocol Identifier Usage
All DTLS control messages MUST be transported on stream 0 with Application protocols running over DTLS over SCTP SHOULD register and
unlimited reliability and with the ordered delivery feature. use a separate payload protocol identifier (PPID) and SHOULD NOT
reuse the PPID which they registered for running directly over SCTP.
User data messages MAY be transported over stream 0 but users SHOULD This means in particular that there is no specific PPID for DTLS.
use other streams for better performance.
4.2. Chunk handling 4.2. Stream Usage
All DTLS messages of the ChangeCipherSpec, Alert, or Handshake
protocol MUST be transported on stream 0 with unlimited reliability
and with the ordered delivery feature.
All DTLS messages of the ApplicationData protocol MAY be transported
over stream 0 but users SHOULD use other streams for better
performance.
4.3. Chunk Handling
The DATA, SACK and FORWARD-TSN chunks of SCTP MUST be sent in an The DATA, SACK and FORWARD-TSN chunks of SCTP MUST be sent in an
authenticated way as described in [RFC4895]. Other chunks MAY be authenticated way as described in [RFC4895]. Other chunks MAY be
sent in an authenticated way. sent in an authenticated way.
This makes sure that an attacker can not modify the stream a message This makes sure that an attacker can not modify the stream a message
is sent in or affect the ordered/unordered delivery of the message. is sent in or affect the ordered/unordered delivery of the message.
It is also not possible for an attacker to drop messages and use It is also not possible for an attacker to drop messages and use
forged FORWARD-TSN and SACK chunks to hide this dropping. forged FORWARD-TSN and SACK chunks to hide this dropping.
4.3. Handshake 4.4. Handshake
To prevent DTLS from discarding user messages while renegotiating, To prevent DTLS from discarding DTLS user messages while
before sending a ClientHello all user messages MUST have been renegotiating, before sending a ChangeCipherSpec message all
acknowledged and can not be revoked anymore by the peer. outstanding SCTP user messages MUST have been acknowledged by the
SCTP peer and MUST NOT be revoked anymore by the SCTP peer.
Prior to sending a HelloVerifyRequest, all user messages MUST be read Prior to processing a received ChangeCipherSpec all other received
from the transport layer or user messages MUST be allowed during SCTP user messages which are buffered in the SCTP layer MUST be read
handshake. and processed by DTLS.
4.4. Handling of endpoint-pair shared secrets User messages arriving between ChangeCipherSpec and Finished using
the new epoch have probably passed the Finished and MUST be buffered
by DTLS until the Finished is read.
4.5. Handling of Endpoint-pair Shared Secrets
The endpoint-pair shared secret for Shared Key Identifier 0 is empty. The endpoint-pair shared secret for Shared Key Identifier 0 is empty.
Whenever the master key changes, a 64 byte shared secret is derived Whenever the master key changes, a 64 byte shared secret is derived
from every master secret and provided as a new end-point pair shared from every master secret and provided as a new end-point pair shared
secret by using the algorithm described in [I-D.ietf-tls-extractor]. secret by using the algorithm described in [I-D.ietf-tls-extractor].
The Shared Key Identifier MUST be incremented by 1. If it is 65535, The Shared Key Identifier MUST be incremented by 1. If it is 65535,
the next value MUST be 1. the next value MUST be 1.
Before sending the Finished message the active SCTP-AUTH key MUST be Before sending the Finished message the active SCTP-AUTH key MUST be
switched to the new one. The Finished message MUST NOT be sent switched to the new one.
before all messages except the ones from this handshake have been
acknowledged and can not be revoked anymore by the peer.
Once the corresponding Finished message from the peer has been Once the corresponding Finished message from the peer has been
received the old key SHOULD be removed. received the old key SHOULD be removed.
4.6. Shutdown
To prevent DTLS from discarding DTLS user messages while shutting
down, before sending a CloseNotify message all outstanding SCTP user
messages MUST have been acknowledged by the SCTP peer and MUST NOT be
revoked anymore by the SCTP peer.
Prior to processing a received CloseNotify all other received SCTP
user messages which are buffered in the SCTP layer MUST be read and
processed by DTLS.
5. IANA Considerations 5. IANA Considerations
IANA needs to add a value to the TLS Extractor Label registry as IANA needs to add a value to the TLS Exporter Label registry as
described in [I-D.ietf-tls-extractor]. The label suggested is described in [I-D.ietf-tls-extractor]. The label suggested is
EXTRACTOR_DTLS_OVER_SCTP. The reference should refer to this EXTRACTOR_DTLS_OVER_SCTP. The reference should refer to this
document. document.
6. Security Considerations 6. Security Considerations
This section is not complete yet. This document does not add any additional security considerations in
addition to the ones given in [RFC4347] and [RFC4895].
7. Acknowledgments 7. Acknowledgments
The authors wish to thank Carsten Hohendorf, and Alfred Hoenes for The authors wish to thank Carsten Hohendorf, and Alfred Hoenes for
their invaluable comments. their invaluable comments.
8. References 8. References
8.1. Normative References 8.1. Normative References
skipping to change at page 7, line 4 skipping to change at page 8, line 32
Security", RFC 4347, April 2006. Security", RFC 4347, April 2006.
[RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla, [RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
"Authenticated Chunks for the Stream Control Transmission "Authenticated Chunks for the Stream Control Transmission
Protocol (SCTP)", RFC 4895, August 2007. Protocol (SCTP)", RFC 4895, August 2007.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007. RFC 4960, September 2007.
[I-D.ietf-tls-extractor] [I-D.ietf-tls-extractor]
Rescorla, E., "Keying Material Extractors for Transport Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", draft-ietf-tls-extractor-02 (work Layer Security (TLS)", draft-ietf-tls-extractor-05 (work
in progress), September 2008. in progress), March 2009.
8.2. Informative References 8.2. Informative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC3436] Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport [RFC3436] Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport
Layer Security over Stream Control Transmission Protocol", Layer Security over Stream Control Transmission Protocol",
RFC 3436, December 2002. RFC 3436, December 2002.
skipping to change at page 8, line 4 skipping to change at line 327
Email: seggelmann@fh-muenster.de Email: seggelmann@fh-muenster.de
Eric Rescorla Eric Rescorla
RTFM, Inc. RTFM, Inc.
2064 Edgewood Drive 2064 Edgewood Drive
Palo Alto, CA 94303 Palo Alto, CA 94303
USA USA
Email: ekr@networkresonance.com Email: ekr@networkresonance.com
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