Internet DRAFT - draft-ietf-uta-ciphersuites-in-sec-syslog
draft-ietf-uta-ciphersuites-in-sec-syslog
Internet Engineering Task Force C. Lonvick
Internet-Draft
Updates: 5425 6012 (if approved) S. Turner
Intended status: Standards Track sn3rd
Expires: 24 March 2024 J. Salowey
Venafi
21 September 2023
Updates to the Cipher Suites in Secure Syslog
draft-ietf-uta-ciphersuites-in-sec-syslog-05
Abstract
The Syslog Working Group 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 24 March 2024.
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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.
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Please review these documents carefully, as they describe your rights
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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 . . . . . . . . . . . . . . . . . . . . . . . 5
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
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 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 out-of-date TLS/DTLS versions.
[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.
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 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
[draft-ietf-tls-rfc8447bis-04] 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-02] 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 [draft-ietf-tls-rfc8447bis-04].
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.
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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.
Finally, [BCP195] [RFC9325] provides guidance on the support of
[[RFC8446] and [RFC9147].
4. Updates to RFC 5425
Implementations of [RFC5425] SHOULD 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.
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
Implementations of [RFC6012] SHOULD 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.
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.
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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 [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 -05 for the UTA Working Group. These edits reflect
comments from the WGLC discussions.
This version changed the MUST NOTs to SHOULD NOTs in Sections 4 and
5. This better conforms with BCP 195 and does not break
interoperability from clients that may not yet have been upgraded to
current MTI cipher suites.
The Security Considerations section has been updated to reflect this.
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, and Viktor Dukhovni for their
comments and constructive feedback.
9. IANA Considerations
This document makes no requests to IANA.
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10. Security Considerations
[BCP195] deprecates an insecure DTLS transport protocol from
[RFC6012] and deprecates insecure cipher suits from [RFC5425] and
[RFC6012]. This document updates the mandatory to implement cipher
suites to conform with those RFCs and the latest version of the DTLS
protocol [RFC6012].
The insecure cipher suites SHOULD NOT be offered. If a device
currently only has an insecure cipher suite, an administrator of the
network should evaluate the conditions and determine if the insecure
cipher suite should be allowed so that syslog messages may continue
to be delivered until the device is updated to have a secure cipher
suite.
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.
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, November 2022.
<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,
<http://www.rfc-editor.org/rfc/rfc5424.txt>.
[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>.
[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-02]
Bartle, C. and N. Aviram, "Deprecating Obsolete Key
Exchange Methods in TLS", Work in Progress, Internet-
Draft, draft-ietf-tls-deprecate-obsolete-kex-02, 11 July
2023, <https://www.ietf.org/archive/id/draft-ietf-tls-
deprecate-obsolete-kex-02.txt>.
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[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-04]
Salowey, J. A. and S. Turner, "IANA Registry Updates for
TLS and DTLS", Work in Progress, Internet-Draft, draft-
ietf-tls-rfc8447bis-04, 28 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
rfc8447bis-04>.
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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