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Updates to the Cipher Suites in Secure Syslog
draft-ietf-uta-ciphersuites-in-sec-syslog-01

Document Type Active Internet-Draft (uta WG)
Authors Chris M. Lonvick , Sean Turner , Joseph A. Salowey
Last updated 2022-07-24
Replaces draft-ciphersuites-in-sec-syslog
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draft-ietf-uta-ciphersuites-in-sec-syslog-01
Internet Engineering Task Force                               C. Lonvick
Internet-Draft                                                          
Updates: 5425 6012 (if approved)                               S. Turner
Intended status: Standards Track                                   sn3rd
Expires: 25 January 2023                                      J. Salowey
                                                              Salesforce
                                                            24 July 2022

             Updates to the Cipher Suites in Secure Syslog
              draft-ietf-uta-ciphersuites-in-sec-syslog-01

Abstract

   This document updates the cipher suites in RFC 5425, Transport Layer
   Security (TLS) Transport Mapping for Syslog, and RFC 6012, Datagram
   Transport Layer Security (DTLS) Transport Mapping for Syslog.  It
   also updates the transport protocol in RFC 6012.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 25 January 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Support for Updating  . . . . . . . . . . . . . . . . . . . .   3
   4.  Updates to RFC 5425 . . . . . . . . . . . . . . . . . . . . .   4
   5.  Updates to RFC 6012 . . . . . . . . . . . . . . . . . . . . .   4
   6.  Early Data  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Authors Notes . . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   6
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     11.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The Syslog Working Group produced Transport Layer Security (TLS)
   Transport Mapping for Syslog [RFC5425] and Datagram Transport Layer
   Security (DTLS) Transport Mapping for Syslog [RFC6012].

   Both [RFC5425] and [RFC6012] MUST support certificates as defined in
   [RFC5280].

   [RFC5425] requires that implementations "MUST" support TLS 1.2
   [RFC5246] and are "REQUIRED" to support the mandatory to implement
   cipher suite TLS_RSA_WITH_AES_128_CBC_SHA (Section 4.2).

   [RFC6012] requires that implementations "MUST" support DTLS 1.0
   [RFC4347] and are also "REQUIRED" to support the mandatory to
   implement cipher suite TLS_RSA_WITH_AES_128_CBC_SHA (Section 5.2).

   The TLS_RSA_WITH_AES_128_CBC_SHA cipher suite has been found to be
   weak and the community is moving away from it and towards more robust
   suites.

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   The DTLS 1.0 transport [RFC4347] has been deprecated by [BCP195] and
   the community is moving to DTLS 1.2 [RFC6347] and DTLS 1.3
   [I-D.ietf-tls-dtls13].

   This document updates [RFC5425] and [RFC6012] to deprecate the use of
   TLS_RSA_WITH_AES_128_CBC_SHA and to make new recommendations to a
   mandatory to implement cipher suite to be used for implementations.
   This document also updates [RFC6012] to make a recommendation of a
   mandatory to implement secure datagram transport.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Support for Updating

   [I-D.salowey-tls-rfc8447bis] generally reminds us that cryptographic
   algorithms and parameters will be broken or weakened over time.
   Blindly implementing the cryptographic algorithms listed in any
   specification is not advised.  Implementers and users need to check
   that the cryptographic algorithms specified continue to provide the
   expected level of security.

   As the Syslog Working Group determined, Syslog clients and servers
   MUST use certificates as defined in [RFC5280].  Since both [RFC5425]
   and [RFC6012] REQUIRE the use of TLS_RSA_WITH_AES_128_CBC_SHA, it is
   very likely that RSA certificates have been implemented in devices
   adhering to those specifications.  [BCP195] notes that ECDHE cipher
   suites exist for both RSA and ECDSA certificates, so moving to an
   ECDHE cipher suite will not require replacing or moving away from any
   currently installed RSA-based certificates.

   [I-D.saviram-tls-deprecate-obsolete-kex] documents that the cipher
   suite TLS_RSA_WITH_AES_128_CBC_SHA has been found to be weak.  As
   such, the community is moving away from that and other weak suites
   and towards more robust suites such as
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, which is also listed as a
   currently Recommended algorithm in [I-D.salowey-tls-rfc8447bis].

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   Along those lines, [I-D.ietf-uta-rfc7525bis] notes that
   TLS_RSA_WITH_AES_128_CBC_SHA does not provide forward secrecy, a
   feature that is highly desirable in securing event messages.  That
   document also goes on to recommend
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 as a cipher suite that does
   provide forward secrecy.

   Therefore, the mandatory to implement cipher suites listed in
   [RFC5425] and [RFC6012] must be updated so that implementations of
   secure syslog are still considered to provide an acceptable and
   expected level of security.

   Additionally, [BCP195] [RFC8996] deprecates the use of DTLS 1.0
   [RFC4347], which is the mandatory to implement transport protocol for
   [RFC6012].  Therefore, the transport protocol for [RFC6012] must be
   updated.

4.  Updates to RFC 5425

   Implementations of [RFC5425] MUST NOT offer
   TLS_RSA_WITH_AES_128_CBC_SHA.  The mandatory to implement cipher
   suite is REQUIRED to be TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256.

   Implementations of [RFC5425] MUST continue to use TLS 1.2 [RFC5246]
   as the mandatory to implement transport protocol.

   Implementations of [RFC5425] MAY use TLS 1.3 [RFC8446] as a transport
   as long as they support the currently recommended cipher suites.

5.  Updates to RFC 6012

   Implementations of [RFC6012] MUST NOT offer
   TLS_RSA_WITH_AES_128_CBC_SHA.  The mandatory to implement cipher
   suite is REQUIRED to be TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256.

   As specified in [BCP195], implementations of [RFC6012] must not use
   DTLS 1.0 [RFC4347].  Implementations MUST use DTLS 1.2 [RFC6347].

   DTLS 1.2 [RFC6347] implementations are REQUIRED to support the
   mandatory to implement cipher suite, which is
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256.

   Implementations of [RFC6012] MAY use DTLS 1.3 [I-D.ietf-tls-dtls13]
   as a transport as long as they support the currently recommended
   cipher suites.

   EDITOR's NOTE: Need to address 0-RTT considerations.

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6.  Early Data

   Early data (aka 0-RTT data) is a mechanism defined in TLS 1.3
   [RFC8446] that allows a client to send data ("early data") as part of
   the first flight of messages to a server.  Early data is permitted by
   TLS 1.3 when the client and server share a PSK, either obtained
   externally or via a previous handshake.  The client uses the PSK to
   authenticate the server and to encrypt the early data.

   As noted in Section 2.3 of [I-D.ietf-tls-rfc8446bis], the security
   properties for early data are weaker than those for subsequent TLS-
   protected data.  In particular, early data is not forward secret, and
   there are no protections against the replay of early data between
   connections.  Appendix E.5 of [I-D.ietf-tls-rfc8446bis] requires
   applications not use early data without a profile that defines its
   use.  Because syslog does not support replay protection, see
   Section 8.4 of [RFC5424]", and most implementations establish a long-
   lived connection, this document specifies that implementations MUST
   NOT use early data.

7.  Authors Notes

   This section will be removed prior to publication.

   This is version -01 for the UTA Working Group.  This version proposes
   a section to address early data (aka 0-RTT data).

   Members of IEC 62351 TC 57 WG15, who prompted this work, have
   proposed the following text to be inserted into their documents.

   |  The selection of TLS connection parameters such as cipher suites,
   |  session resumption and renegotiation shall be reused from IEC
   |  62351-3 specification.  Note that port TCP/6514 is assigned by
   |  IANA to RFC 5425 (syslog-tls).  The RFC requires the support of
   |  TLS1.2 and a SHA-1 based cipher suite, but does not mandate its
   |  use.  The cipher does not align with IEC 62351-3 Ed.2 for
   |  profiling TLS.  Nevertheless, RFC 5425 does not rule out to use
   |  stronger cipher suites.  With this, clients and server supporting
   |  the selection of cipher suites stated in IEC 62351-3 Ed2 will not
   |  experience interoperability problems.  Caution has to be taken in
   |  environments in which interworking with existing services
   |  utilizing syslog over TLS is intended.  For these, the syslog
   |  server needs to be enabled to support the required cipher suites.
   |  This ensures connectivity with clients complying to this document
   |  and others complying to RFC 5425.  Note that meanwhile the work on
   |  an update of RFC 5425 and RFC 6012 has started.  It targets the
   |  adoption of stronger cipher suites for TLS and DTLS to protect
   |  syslog communication.

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   Comments on this text are welcome.

8.  Acknowledgments

   The authors would like to thank Arijit Kumar Bose, Steffen Fries and
   the members of IEC TC57 WG15 for their review, comments, and
   suggestions.  The authors would also like to thank Tom Petch and
   Juergen Schoenwaelder for their comments and constructive feedback.

9.  IANA Considerations

   This document makes no requests to IANA.

10.  Security Considerations

   [BCP195] deprecates an insecure DTLS transport protocol from
   [RFC6012] and deprecates insecure cipher suits from [RFC5425] and
   [RFC6012].  This document specifies mandatory to implement cipher
   suites to those RFCs and the latest version of the DTLS protocol to
   [RFC6012].

11.  References

11.1.  Normative References

   [BCP14]    Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

              Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, May 2017.

              <https://www.rfc-editor.org/info/bcp14>

   [BCP195]   Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, May 2015.

              Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
              1.1", BCP 195, RFC 8996, March 2021.

              <https://www.rfc-editor.org/info/bcp195>

   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security", RFC 4347, DOI 10.17487/RFC4347, April 2006,
              <https://www.rfc-editor.org/info/rfc4347>.

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   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [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, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424, March 2009,
              <https://www.rfc-editor.org/rfc/rfc5424>.

   [RFC5425]  Miao, F., Ed., Ma, Y., Ed., and J. Salowey, Ed.,
              "Transport Layer Security (TLS) Transport Mapping for
              Syslog", RFC 5425, DOI 10.17487/RFC5425, March 2009,
              <https://www.rfc-editor.org/info/rfc5425>.

   [RFC6012]  Salowey, J., Petch, T., Gerhards, R., and H. Feng,
              "Datagram Transport Layer Security (DTLS) Transport
              Mapping for Syslog", RFC 6012, DOI 10.17487/RFC6012,
              October 2010, <https://www.rfc-editor.org/info/rfc6012>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

11.2.  Informative References

   [I-D.ietf-tls-dtls13]
              Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
              dtls13, 30 April 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-tls-
              dtls13>.

   [I-D.ietf-tls-rfc8446bis]
              Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", Work in Progress, Internet-Draft, draft-
              ietf-tls-rfc8446bis-00, 5 October 2020,
              <https://datatracker.ietf.org/doc/html/draft-ietf-tls-
              rfc8446bis-00>.

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   [I-D.ietf-uta-rfc7525bis]
              Sheffer, Y., Holz, R., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", Work in Progress, Internet-Draft, draft-ietf-uta-
              rfc7525bis-04, 2 December 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-uta-
              rfc7525bis-04>.

   [I-D.salowey-tls-rfc8447bis]
              Salowey, J. and S. Turner, "IANA Registry Updates for TLS
              and DTLS", Work in Progress, Internet-Draft, draft-
              salowey-tls-rfc8447bis-01, 2 December 2021,
              <https://datatracker.ietf.org/doc/html/draft-salowey-tls-
              rfc8447bis-01>.

   [I-D.saviram-tls-deprecate-obsolete-kex]
              Aviram, N., "Deprecating Obsolete Key Exchange Methods in
              TLS", Work in Progress, Internet-Draft, draft-aviram-tls-
              deprecate-obsolete-kex-00, 9 July 2021,
              <https://datatracker.ietf.org/doc/html/draft-aviram-tls-
              deprecate-obsolete-kex-00>.

Authors' Addresses

   Chris Lonvick
   Email: lonvick.ietf@gmail.com

   Sean Turner
   sn3rd
   Email: sean@sn3rd.com

   Joe Salowey
   Salesforce
   Email: joe@salowey.net

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