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Versions: 00 01 02 03 04 05 06 RFC 6012

Network Working Group                                         J. Salowey
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                                 H. Feng
Expires: April 17, 2010                             Huaweisymantec, Inc.
                                                                T. Petch
                                                Engineering Networks Ltd
                                                             R. Gerhards
                                                            Adiscon GmbH
                                                        October 14, 2009


 Datagram Transport Layer Security (DTLS) Transport Mapping for Syslog
                     draft-ietf-syslog-dtls-00.txt

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Copyright Notice



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   Copyright (c) 2009 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 in effect on the date of
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   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.











































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Abstract

   This document describes the transport of syslog messages over DTLS
   (Datagram Transport Level Security).  It provides a secure transport
   for syslog messages in cases where a connection-less transport is
   desired.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4

   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5

   3.  Security Requirements for Syslog . . . . . . . . . . . . . . .  6

   4.  Using DTLS to Secure Syslog  . . . . . . . . . . . . . . . . .  7

   5.  Protocol Elements  . . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  Transport  . . . . . . . . . . . . . . . . . . . . . . . .  8
       5.1.1.  Congestion Control . . . . . . . . . . . . . . . . . .  8
       5.1.2.  Reliability  . . . . . . . . . . . . . . . . . . . . .  8
       5.1.3.  Reordering . . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  Port Assignment  . . . . . . . . . . . . . . . . . . . . .  9
     5.3.  Initiation . . . . . . . . . . . . . . . . . . . . . . . .  9
       5.3.1.  Certificate-Based Authentication . . . . . . . . . . .  9
       5.3.2.  Cryptographic Level  . . . . . . . . . . . . . . . . . 10
     5.4.  Sending data . . . . . . . . . . . . . . . . . . . . . . . 10
       5.4.1.  Message Size . . . . . . . . . . . . . . . . . . . . . 10
     5.5.  Closure  . . . . . . . . . . . . . . . . . . . . . . . . . 11

   6.  Security Policies  . . . . . . . . . . . . . . . . . . . . . . 12

   7.  IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 13

   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14

   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15

   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 16
     10.2. Informative References . . . . . . . . . . . . . . . . . . 16

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18







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1.  Introduction

   The Syslog protocol [RFC5424] is designed to run over different
   transports for different environments.  [RFC5425] provides a
   combination of TCP transport reliability with TLS security [RFC5246].

   However, TCP performance can be a problem when a network has a high
   rate of lost packets.  In these circumstances, an operator might
   prefer using UDP to TCP as transport.  Transmission of Syslog
   Messages over UDP [RFC5426] defines how to provide unreliable, non-
   secure datagram transport for SYSLOG.

   The datagram transport layer security protocol (DTLS) [RFC4347] is
   designed to meet the requirements of applications that need secure
   datagram transport, by combining UDP transport with TLS security
   [RFC5246].  DTLS has been mapped onto different transports (i.e.
   UDP, DCCP, SCTP), to secure syslog in more situations.

   This document describes how to use SYSLOG with a DTLS transport.
































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2.  Terminology

   The following definitions from [RFC5424] are used in this document:

   o  An "originator" generates syslog content to be carried in a
      message.

   o  A "collector" gathers syslog content for further analysis.

   o  A "relay" forwards messages, accepting messages from originators
      or other relays, and sending them to collectors or other relays.

   o  A "transport sender" passes SYSLOG messages to a specific
      transport protocol.

   o  A "transport receiver" takes SYSLOG messages from a specific
      transport protocol.

   o  A "DTLS client" is an application that can initiate a DTLS Client
      Hello to a server.

   o  A "DTLS server" is an application that can receive a Client Hello
      from a client and reply with a Server Hello.

   The term "connection" used in this document is used to refer to a
   secure association between transport sender and transport receiver
   that permits the transmission of one or more SYSLOG messages within
   the lifetime of the connection.

   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].



















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3.  Security Requirements for Syslog

   Syslog messages are secured in a hop-by-hop manner.  The security
   requirements for Syslog are discussed in [RFC5425].

   The following secondary threat is also considered in this document:

   o  Denial of Service.  Denial of service is discussed in [RFC5424],
      which states that an attacker may send more messages to a
      transport receiver than the transport receiver could handle.  When
      using a secure transport protocol handshake, an attacker may use a
      spoofed IP source to engage the server in a cryptographic
      handshake to deliberately consume the server's resources.






































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4.  Using DTLS to Secure Syslog

   DTLS can be used as a secure transport to counter all the primary
   threats to SYSLOG described in [RFC5425]:

   o  Confidentiality to counter disclosure of the message contents.

   o  Integrity checking to counter modifications to a message on a hop-
      by-hop basis.

   o  Server or mutual authentication to counter masquerade.

   In addition DTLS also provides:

   o  A cookie exchange mechanism during handshake to counter Denial of
      Service attacks

   o  A sequence number in the header to counter replay attacks.

   Note: This secure transport (i.e., DTLS) only secures syslog
   transport in a hop-by-hop manner, and is not concerned with the
   contents of syslog messages.  In particular, the authenticated
   identity of the transport sender (e.g., subject name in the
   certificate) is not necessarily related to the HOSTNAME field of the
   syslog message.  When authentication of syslog message origin is
   required, [I-D.ietf-syslog-sign] can be used.

























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5.  Protocol Elements

5.1.  Transport

   DTLS can run over multiple transports.  Implementations of this
   specification MUST support DTLS over UDP.  Transports, such as UDP or
   DCCP do not provide session multiplexing and session-demultiplexing.
   In such case, the application implementer provides this functionality
   by mapping a unique combination of the remote address, remote port
   number, local address and local port number to a session.

   When TCP is used syslog over DTLS MUST NOT be used.  If a secure
   transport is required with TCP then the appropriate mechanism is
   syslog over TLS.

5.1.1.  Congestion Control

   The DTLS mapping on UDP transport does not provide congestion control
   mechanism, so, SYSLOG transport over DTLS have the same congestion
   control problems with transport over UDP.  [RFC5426] has state such
   problems, when generated unlimited amounts of log transport on the
   internet, could influence the stable operation of the internet.
   [RFC5405] has guideline for an application SHOULD perform congestion
   control over UDP transport, referring to [RFC5405] for details.

   Datagram Congestion Control Protocol [RFC4340] is designed and is
   usually be thought as UDP plus congestion control, which builds-in
   congestion control mechanism for datagram.  DTLS can run over DCCP,
   [RFC5238] (Datagram Transport Layer Security over the Datagram
   Congestion Control Protocol) states such combination.  To respond to
   congestion and establish a degree of fairness [RFC2914], it is
   RECOMMENDED that the implementer also support DCCP [RFC4340] for DTLS
   to provide congestion control.

5.1.2.  Reliability

   When DTLS runs over an unreliable transport such as UDP reliability
   is not provided.  With DTLS, an originator or relay may not realize
   that a collector has gone down or lost its connection state so
   messages may be lost.

   If reliability is required then Syslog over TLS may be used.

5.1.3.  Reordering

   Each SYSLOG message is delivered by DTLS record protocol, which has
   assigned a sequence number for each DTLS record.  Although the DTLS
   implementer may adopt Queue mechanism to resolve reordering, it may



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   not assure that all the messages delivered in order when mapping on
   UDP transport.

5.2.  Port Assignment

   A SYSLOG transport sender is always a DTLS client and a transport
   receiver is always a DTLS server.

   The UDP and DCCP port [TBD] has been allocated as the default port
   for syslog over DTLS as defined in this document.

5.3.  Initiation

   The transport sender initiates a DTLS connection by sending a DTLS
   Client Hello to the transport receiver.  It is RECOMMENDED that
   implementations support the denial of service countermeasures defined
   by DTLS.  In this case, the transport receiver responds with a DTLS
   Hello Verify Request containing a cookie.  The transport sender
   responds with a DTLS Client Hello containing the received cookie
   which initiates the DTLS handshake.  When the DTLS handshake has
   finished, the transport sender MAY then send the first syslog
   message.

   TLS typically uses certificates [RFC5280] to authenticate peers.
   Implementations MUST support DTLS 1.1 [RFC4347] and are REQUIRED to
   support the mandatory to implement cipher suite, which is
   TLS_RSA_WITH_AES_128_CBC_SHA.  This document is assumed to apply to
   future versions of DTLS, in which case the mandatory to implement
   cipher suite for the implemented version MUST be supported.

5.3.1.  Certificate-Based Authentication

   Both syslog transport sender (DTLS client) and syslog transport
   receiver (DTLS server) MUST implement certificate-based
   authentication.  This consists of validating the certificate and
   verifying that the peer has the corresponding private key.  The
   latter part is performed by DTLS.  To ensure interoperability between
   clients and servers, the methods for certificate validation defined
   in [RFC5425] SHALL be implemented.

   Both transport receiver and transport sender implementations MUST
   provide means to generate a key pair and self-signed certificate in
   the case that a key pair and certificate are not available through
   another mechanism.

   The transport receiver and transport sender SHOULD provide mechanisms
   to record the end-entity certificate for the purpose of correlating
   it with the sent or received data.



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5.3.2.  Cryptographic Level

   Syslog applications SHOULD be implemented in a manner that permits
   administrators, as a matter of local policy, to select the
   cryptographic level and authentication options they desire.

   DTLS permits the resumption of an earlier DTLS session or the use of
   another active session when a new session is requested, in order to
   save the expense of another full DTLS handshake.  The security
   parameters of the resumed session are reused for the requested
   session.  The security parameters SHOULD be checked against the
   security requirements of the requested session to make sure that the
   resumed session provides proper security.

5.4.  Sending data

   All syslog messages MUST be sent as DTLS "application data".  It is
   possible that multiple syslog messages be contained in one DTLS
   record, or that a syslog message be transferred in multiple DTLS
   records.  The application data is defined with the following ABNF
   [RFC5234] expression:

   APPLICATION-DATA = 1*SYSLOG-FRAME

   SYSLOG-FRAME = MSG-LEN SP SYSLOG-MSG

   MSG-LEN = NONZERO-DIGIT *DIGIT

   SP = %d32

   NONZERO-DIGIT = %d49-57

   DIGIT = %d48 / NONZERO-DIGIT

   SYSLOG-MSG is defined in syslog [RFC5424] protocol.

5.4.1.  Message Size

   The message length is the octet count of the SYSLOG-MSG in the
   SYSLOG-FRAME.  A transport receiver MUST use the message length to
   delimit a syslog message.  There is no upper limit for a message
   length per se.  As stated in [RFC4347], each DTLS record must fit
   within a single DTLS datagram.  When mapping onto different
   transports, DTLS has different record size limitations.  The
   application implementer SHOULD determine the maximum record size to
   that allowed by DTLS protocol running over the transport in use.  The
   message size SHOULD NOT exceed the maximum record size limitation by
   DTLS.



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5.5.  Closure

   A transport sender MUST close the associated DTLS connection if the
   connection is not expected to deliver any syslog messages later.  It
   MUST send a DTLS close_notify alert before closing the connection.  A
   transport sender (DTLS client) MAY choose to not wait for the
   transport receiver's close_notify alert and simply close the
   connection.  Once the transport receiver gets a close_notify from the
   transport sender, it MUST reply with a close_notify.

   When no data is received from a connection for a long time (where the
   application decides what "long" means), a transport receiver MAY
   close the connection.  The transport receiver (DTLS server) MUST
   attempt to initiate an exchange of close_notify alerts with the
   transport sender before closing the connection.  Transport receivers
   that are unprepared to receive any more data MAY close the connection
   after sending the close_notify alert.

   Although closure alerts form part of DTLS, they, like all alerts, are
   not retransmitted by DTLS and so may be lost over an unreliable
   network.






























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6.  Security Policies

   Syslog transport over DTLS has been designed to minimize the security
   and operational differences for environments where both [RFC5425] and
   SYSLOG over DTLS are supported.  The security policies for SYSLOG
   over DTLS are the same as those described in [RFC5425].













































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7.  IANA Consideration

   IANA is requested to assign a registered UDP and DCCP port number for
   SYSLOG over DTLS.















































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8.  Security Considerations

   The security considerations in [RFC5425], [RFC5246] and [RFC4347]
   apply to this document.















































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9.  Acknowledgements

   The authors would like to thank Wes Hardaker for his review on this
   proposal and contributing his valuable suggestions on the use of
   DTLS.  Thanks also to Pasi Eronen and David Harrington for their
   comments, suggestions and review.













































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10.  References

10.1.  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.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

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

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424, March 2009.

   [RFC5425]  Miao, F., Ma, Y., and J. Salowey, "Transport Layer
              Security (TLS) Transport Mapping for Syslog", RFC 5425,
              March 2009.

   [RFC5426]  Okmianski, A., "Transmission of Syslog Messages over UDP",
              RFC 5426, March 2009.

10.2.  Informative References

   [I-D.ietf-syslog-sign]
              Kelsey, J., Callas, J., and A. Clemm, "Signed syslog
              Messages", draft-ietf-syslog-sign-27 (work in progress),
              August 2009.

   [RFC2914]  Floyd, S., "Congestion Control Principles", BCP 41,
              RFC 2914, September 2000.

   [RFC4340]  Kohler, E., Handley, M., and S. Floyd, "Datagram
              Congestion Control Protocol (DCCP)", RFC 4340, March 2006.

   [RFC5238]  Phelan, T., "Datagram Transport Layer Security (DTLS) over
              the Datagram Congestion Control Protocol (DCCP)",
              RFC 5238, May 2008.

   [RFC5405]  Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines



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              for Application Designers", BCP 145, RFC 5405,
              November 2008.

















































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Authors' Addresses

   Joseph Salowey
   Cisco Systems, Inc.
   2901 3rd. Ave
   Seattle, WA  98121
   USA

   Email: jsalowey@cisco.com


   Hongyan. Feng
   Huaweisymantec, Inc.

   Email: hongyanfeng@huaweisymantec.com


   Tom Petch
   Engineering Networks Ltd
   18 Parkwood Close
   Lymm, Cheshire  WA13 0NQ
   UK

   Email: tomSecurity@network-engineer.co.uk


   Rainer Gerhards
   Adiscon GmbH
   Mozartstrasse 21
   Grossrinderfeld, BW  97950
   Germany

   Email: rgerhards@adiscon.com


















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