Internet Engineering Task Force (IETF) C. LonvickInternet-DraftRequest for Comments: 9662 Updates:54255425, 6012(if approved)S. TurnerIntended status:Category: Standards Track sn3rdExpires: 25 January 2025ISSN: 2070-1721 J. Salowey Venafi24 JulySeptember 2024 Updates to the Cipher Suites in Secure Syslogdraft-ietf-uta-ciphersuites-in-sec-syslog-07AbstractThe IETF published two specifications, namely RFCRFCs 5425 andRFC 6012, for securing the Syslog protocol6012 describe using TLS andDTLS, respectively.DTLS to securely transport syslog messages. This document updates the cipher suitesinrequired by RFC5425, Transport Layer Security (TLS)5245 (TLS Transport Mapping forSyslog,Syslog) and RFC6012, Datagram Transport Layer Security (DTLS)6012 (DTLS Transport Mapping forSyslog.Syslog). It also updates thetransportprotocolinrecommended by RFC6012.6012 for secure datagram transport. Status of This Memo ThisInternet-Draftissubmitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documentsan Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF).Note that other groups may also distribute working documents as Internet-Drafts. The listIt represents the consensus ofcurrent Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents validthe IETF community. It has received public review and has been approved fora maximumpublication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 ofsix monthsRFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may beupdated, replaced, or obsoleted by other documentsobtained atany 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 2025.https://www.rfc-editor.org/info/rfc9662. Copyright Notice Copyright (c) 2024 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(https://trustee.ietf.org/ license-info)(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. . . . . . . . . . . . . . . . . . . . . . . . 22. Terminology. . . . . . . . . . . . . . . . . . . . . . . . . 33. Support for Updating. . . . . . . . . . . . . . . . . . . . 34. Updates to RFC 5425. . . . . . . . . . . . . . . . . . . . . 45. Updates to RFC 6012. . . . . . . . . . . . . . . . . . . . . 46. Early Data. . . . . . . . . . . . . . . . . . . . . . . . . 57.Authors Notes . . . . . . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 9.IANA Considerations. . . . . . . . . . . . . . . . . . . . . 6 10.8. Security Considerations. . . . . . . . . . . . . . . . . . . 6 11.9. References. . . . . . . . . . . . . . . . . . . . . . . . . 6 11.1.9.1. Normative References. . . . . . . . . . . . . . . . . . 6 11.2.9.2. Informative References. . . . . . . . . . . . . . . . . 8Acknowledgments Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . . 81. IntroductionThe IETF published RFC 5425, Transport"Transport Layer Security (TLS) Transport Mapping forSyslog,Syslog" [RFC5425] andRFC 6012, Datagram"Datagram Transport Layer Security (DTLS) Transport Mapping forSyslog. Both specifications, [RFC5425]Syslog" [RFC6012] describe using TLS and[RFC6012],DTLS to securely transport syslog messages. Both of these specifications require the use ofRSA- basedRSA-based certificates and the use ofTLS/DTLSTLS and DTLS versions that are not the most recent. Section 4.2 of [RFC5425] requires that implementations"MUST"MUST support TLS 1.2 [RFC5246] and are"REQUIRED"REQUIRED to support themandatory tomandatory-to- implement cipher suiteTLS_RSA_WITH_AES_128_CBC_SHA (Section 4.2).TLS_RSA_WITH_AES_128_CBC_SHA. Section 5.2 of [RFC6012] requires that implementations "MUST" support DTLS 1.0 [RFC4347] and are also "REQUIRED" to support themandatory to implementmandatory- to-implement cipher suiteTLS_RSA_WITH_AES_128_CBC_SHA (Section 5.2).TLS_RSA_WITH_AES_128_CBC_SHA. The community is moving away from ciphersuitssuites that don't offer forward secrecy and towards more robust suites. The DTLS 1.0 transport [RFC4347] has been deprecated by[BCP195]RFC 8996 [BCP195], and the community is moving to DTLS 1.2 [RFC6347] and DTLS 1.3 [RFC9147]. 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 ofby recommending amandatory tomandatory-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][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,Syslogsyslog 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. RFC 9325 [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][DEPRECATE-KEX] 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, RFC 9325 [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 as a currentlyRECCOMENDEDRECOMMENDED algorithm in[draft-ietf-tls-rfc8447bis-09][RFC8447bis] for their deployments of secure syslog. Additionally, RFC 8996 [BCP195][RFC8996]deprecates the use of DTLS 1.0 [RFC4347], which is themandatory to implementmandatory-to-implement transport protocolforper [RFC6012]. Therefore,thethat transport protocolfor [RFC6012]must be updated. Finally, RFC 9325 [BCP195](RFC9325)provides guidance on the support of TLS 1.3 [RFC8446] and DTLS 1.3 [RFC9147]. Therefore, to maintain interoperability across implementations, themandatory to implementmandatory-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 suitesmandatated to be used inmandated by [RFC6012], a sudden change is notdesireable.desirable. Toaccomodateaccommodate a migration path,this specification will allow the use of bothTLS_RSA_WITH_AES_128_CBC_SHAandor TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 may be used, butREQUIRESit is REQUIRED that TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 be preferred. 4. Updates to RFC 5425 Themandatory to implementmandatory-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 themandatory to implementmandatory-to-implement transport protocol. As per RFC 9325 [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 Themandatory to implementmandatory-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 [RFC6012] SHOULD offer TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 but MAY offer TLS_RSA_WITH_AES_128_CBC_SHA. As specified in RFCs 8996 and 9325 [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 themandatory to implementmandatory-to-implement cipher suite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256. As per RFC 9325 [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],[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[draft-ietf-tls-rfc8446bis-09][RFC8446bis] requires that applications not use early data without a profile that defines its use. Because syslog does not support replayprotection, seeprotection (see Section 8.4 of[RFC5424]",[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. 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 documentmakeshas norequests to IANA. 10.IANA actions. 8. Security Considerations RFCs 8996 and 9325 [BCP195]deprecatesdeprecate an insecure DTLS transport protocol from [RFC6012] anddeprecatesdeprecate insecure ciphersuitssuites from [RFC5425] and [RFC6012]. However, the installed base of syslog implementations is not easily updated to immediately adhere to those changes. This document updates themandatory to implementmandatory-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_SHA256.11.9. References11.1.9.1. 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>.[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>. [RFC2119] 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>. [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, DOI 10.17487/RFC5424, March 2009,<https://www.rfc-editor.org/rfc/rfc5424>.<https://www.rfc-editor.org/info/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>. [RFC8174] 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>. [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>.11.2.9.2. Informative References[draft-ietf-tls-deprecate-obsolete-kex-04][DEPRECATE-KEX] Bartle, C. and N. Aviram, "Deprecating Obsolete Key Exchange Methods inTLS",TLS 1.2", 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]draft-ietf-tls-deprecate-obsolete-kex-05, 3 September 2024, <https://datatracker.ietf.org/doc/html/ draft-ietf-tls-deprecate-obsolete-kex-05>. [RFC8446bis] 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]ietf-tls-rfc8446bis-11, 14 September 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-tls- rfc8446bis-11>. [RFC8447bis] 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 2023,30 April 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-tls- rfc8447bis-09>. 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. Authors' Addresses Chris Lonvick Email: lonvick.ietf@gmail.com Sean Turner sn3rd Email: sean@sn3rd.com Joe Salowey Venafi Email: joe@salowey.net