Updates to the Cipher Suites in Secure Syslog
draft-ietf-uta-ciphersuites-in-sec-syslog-07

Internet Engineering Task Force                               C. Lonvick
Internet-Draft                                                          
Updates: 5425 6012 (if approved)                               S. Turner
Intended status: Standards Track                                   sn3rd
Expires: 25 January 2025                                      J. Salowey
                                                                  Venafi
                                                            24 July 2024

             Updates to the Cipher Suites in Secure Syslog
              draft-ietf-uta-ciphersuites-in-sec-syslog-07

Abstract

   The IETF published two specifications, namely RFC 5425 and RFC 6012,
   for securing the Syslog protocol using TLS and DTLS, respectively.

   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
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   This Internet-Draft will expire on 25 January 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights

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   and restrictions with respect to this document.  Code Components
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   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 . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The IETF published RFC 5425, Transport Layer Security (TLS) Transport
   Mapping for Syslog, and RFC 6012, Datagram Transport Layer Security
   (DTLS) Transport Mapping for Syslog.

   Both specifications, [RFC5425] and [RFC6012], require the use of RSA-
   based certificates and the use of TLS/DTLS versions that are not the
   most recent.

   [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 community is moving away from cipher suits that don't offer
   forward secrecy and towards more robust suites.

   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 [RFC9147].

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   This document updates [RFC5425] and [RFC6012] to prefer the use of
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 over the use of
   TLS_RSA_WITH_AES_128_CBC_SHA.

   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

   [draft-ietf-tls-rfc8447bis-09] 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] REQUIRED 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.

   [draft-ietf-tls-deprecate-obsolete-kex-04] documents that the cipher
   suite TLS_RSA_WITH_AES_128_CBC_SHA, along with some other cipher
   suites, may require mitigation techniques to achieve expected
   security, which may be difficult to effectively implement.  Along
   those lines, [BCP195] [RFC9325] 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.

   As such, the community is moving away from algorithms that do not
   provide forward secrecy.  For example, the International
   Electrotechnical Commission (IEC) has selected more robust suites
   such as TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, which is also listed

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   as a currently RECCOMENDED algorithm in
   [draft-ietf-tls-rfc8447bis-09] for their deployments of secure
   syslog.

   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.

   Finally, [BCP195] (RFC9325) provides guidance on the support of
   [RFC8446] and [RFC9147].

   Therefore, to maintain interoperability across implementations, the
   mandatory to implement cipher suites listed in [RFC5425] and
   [RFC6012] should be updated so that implementations of secure syslog
   will still interoperate and provide an acceptable and expected level
   of security.

   However, since there are many implementations of syslog using the
   cipher suites mandatated to be used in [RFC6012], a sudden change is
   not desireable.  To accomodate a migration path, this specification
   will allow the use of both TLS_RSA_WITH_AES_128_CBC_SHA and
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 but REQUIRES that
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 be preferred.

4.  Updates to RFC 5425

   The mandatory to implement cipher suites are REQUIRED to be
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 and
   TLS_RSA_WITH_AES_128_CBC_SHA.

   Implementations of [RFC5425] SHOULD offer
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 but MAY offer
   TLS_RSA_WITH_AES_128_CBC_SHA.

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

   As per [BCP195], implementations of [RFC5425] SHOULD support TLS 1.3
   [RFC8446] and, if implemented, MUST prefer to negotiate TLS 1.3 over
   earlier versions of TLS.

5.  Updates to RFC 6012

   The mandatory to implement cipher suites are REQUIRED to be
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 and
   TLS_RSA_WITH_AES_128_CBC_SHA.

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   Implementations of [RFC6012] SHOULD offer
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 but MAY offer
   TLS_RSA_WITH_AES_128_CBC_SHA.

   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 SHOULD support and prefer the
   mandatory to implement cipher suite
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256.

   As per [BCP195], implementations of [RFC6012] SHOULD support DTLS 1.3
   [RFC9147] and, if implemented, MUST prefer to negotiate DTLS version
   1.3 over earlier versions of DTLS.

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 [draft-ietf-tls-rfc8446bis-09], 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
   [draft-ietf-tls-rfc8446bis-09] 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 -07 for the UTA Working Group.  These edits reflect
   comments from IESG review.

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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, Juergen
   Schoenwaelder, Hannes Tschofenig, Viktor Dukhovni, and the IESG
   members 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].  However, the installed base of syslog implementations is
   not easily updated to immediately adhere to those changes.

   This document updates the mandatory to implement cipher suites to
   allow for a migration from TLS_RSA_WITH_AES_128_CBC_SHA to
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 without deprecating the former.
   Implementations should prefer to use
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256.

   If a device currently only has TLS_RSA_WITH_AES_128_CBC_SHA, an
   administrator of the network should evaluate the conditions and
   determine if TLS_RSA_WITH_AES_128_CBC_SHA should be allowed so that
   syslog messages may continue to be delivered until the device is
   updated to have TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256.

11.  References

11.1.  Normative References

   [BCP14]    Best Current Practice 14,
              <https://www.rfc-editor.org/info/bcp14>.
              At the time of writing, this BCP comprises the following:

              Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

              Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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   [BCP195]   Best Current Practice 195,
              <https://www.rfc-editor.org/info/bcp195>.
              At the time of writing, this BCP comprises the following:

              Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
              1.1", BCP 195, RFC 8996, DOI 10.17487/RFC8996, March 2021,
              <https://www.rfc-editor.org/info/rfc8996>.

              Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/info/rfc9325>.

   [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>.

   [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>.

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   [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>.

   [RFC9147]  Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
              <https://www.rfc-editor.org/info/rfc9147>.

11.2.  Informative References

   [draft-ietf-tls-deprecate-obsolete-kex-04]
              Bartle, C. and N. Aviram, "Deprecating Obsolete Key
              Exchange Methods in TLS", Work in Progress, Internet-
              Draft, draft-ietf-tls-deprecate-obsolete-kex-04, 11 July
              2023, <https://www.ietf.org/archive/id/draft-ietf-tls-
              deprecate-obsolete-kex-04.txt>.

   [draft-ietf-tls-rfc8446bis-09]
              Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", Work in Progress, Internet-Draft, draft-
              ietf-tls-rfc8446bis-09, 7 July 2023,
              <https://www.ietf.org/archive/id/draft-ietf-tls-
              rfc8446bis-09.txt>.

   [draft-ietf-tls-rfc8447bis-09]
              Salowey, J. A. and S. Turner, "IANA Registry Updates for
              TLS and DTLS", Work in Progress, Internet-Draft, draft-
              ietf-tls-rfc8447bis-09, 28 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-tls-
              rfc8447bis-09>.

Authors' Addresses

   Chris Lonvick
   Email: lonvick.ietf@gmail.com

   Sean Turner
   sn3rd
   Email: sean@sn3rd.com

   Joe Salowey
   Venafi
   Email: joe@salowey.net

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