Deprecation of IKEv1 and obsoleted algorithms

Internet-Draft	Deprecation of IKEv1 and some algorithms	December 2022
Wouters	Expires 22 June 2023	[Page]

Abstract

Internet Key Exchange version 1 (IKEv1) has been deprecated and its specification in RFC2407, RFC2408 and RFC2409 have been moved to Historic status. This document updates RFC 8221 and RFC 8247 to reflect the usage guidelines of old algorithms that are associated with IKEv1, and are not specified or commonly implemented for IKEv2. This document further updates the IANA IKEv2 Transform Type registries to add a Status column where deprecation status can be listed.¶

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶

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This Internet-Draft will expire on 22 June 2023.¶

Copyright Notice

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1. Introduction

IKEv1 has been moved to Historic status. IKEv1 [RFC2409] and its related documents for ISAKMP [RFC2408] and IPsec DOI [RFC2407] were obsoleted by IKEv2 [RFC4306] in December 2005. The latest version of IKEv2 at the time of writing was published in 2014 in [RFC7296]. The Internet Key Exchange (IKE) version 2 has replaced version 1 over 15 years ago. IKEv2 has now seen wide deployment and provides a full replacement for all IKEv1 functionality. No new modifications or new algorithms have been accepted for IKEv1 for at least a decade. IKEv2 addresses various issues present in IKEv1, such as IKEv1 being vulnerable to amplification attacks.¶

Algorithm implementation requirements and usage guidelines for IKEv2 [RFC8247] and ESP/AH [RFC8221] gives guidance to implementors but limits that guidance to avoid broken or weak algorithms. These two RFCs do not deprecate algorithms that have aged and are not in use, but leave these algorithms in a state of "MAY be used" by not mentioning them. This document deprecates those unmentioned algorithms that are no longer advised but for which there are no known attacks resulting in their earlier deprecation.¶

3. RFC2407, RFC2408 and RFC2409 are Historic

IKEv1 is deprecated. Systems running IKEv1 should be upgraded and reconfigured to run IKEv2. Systems that support IKEv1 but not IKEv2 are most likely also unsuitable candidates for continued operation:¶

IKEv1 development ceased over a decade ago and no new work will happen. This poses the risk of unmaintained code in an otherwise supported product which can result in security vulnerabilities.¶
A number of IKEv1 systems have reached their End of Life and therefor will never be patched by the vendor if a vulnerability is found.¶
There are vendors that still provide updates for their equipment that supports IKEv1 and IKEv2, but have "frozen" their IKEv1 implementation. Such users might not be aware that they are running unmaintained code with its associated security risks.¶
IKEv1 systems can be abused for packet amplification attacks, as documented in the Security Bulletin [CVE-2016-5361].¶
Great strides have been made in cryptography since IKEv1 development ceased. While some modern cryptographic algorithms were added to IKEv1, interoperability concerns mean that the defacto algorithms negotiated by IKEv1 will consist of dated or deprecated algorithms like AES-CBC, SHA1, and Diffie-Hellman groups 1 or 2. IKEv2 provides state-of-the-art suite of cryptographic algorithms that IKEv1 lacks.¶

IKEv2 is a more secure protocol than IKEv1. For example, IKEv2 offers more modern cryptographic primitives, proper defense against denial of service attacks, improved authentication via EAP methods, PAKE support and is actively worked on with respect to defending against quantum computer attacks.¶

IKEv1-only systems should be upgraded or replaced by systems supporting IKEv2. IKEv2 implementations SHOULD NOT directly import IKEv1 configurations without updating the cryptographic algorithms used.¶

4. IKEv1 feature equivalents for IKEv2

A few notable IKEv1 features are not present in the IKEv2 core specification [RFC7296] but are available for IKEv2 via an additional specification:¶

4.1. IKEv2 postquantum support

IKEv1 and its way of using Preshared Keys (PSKs) protects against quantum computer based attacks. IKEv2 updated its use of PSK to improve the error reporting, but at the expense of post-quantum security. If post-quantum security is required, these systems should be migrated to use IKEv2 Postquantum Preshared Keys (PPK) [RFC8784]¶

4.2. IKEv2 Labeled IPsec support

Some IKEv1 implementations support Labeled IPsec, a method to negotiate an additional Security Context selector to the SPD, but this method was never standardized in IKEv1. Those IKEv1 systems that require Labeled IPsec should migrate to an IKEv2 system supporting Labeled IPsec as specified in [draft-ietf-ipsecme-labeled-ipsec].¶

4.3. IKEv2 Group SA / Multicast support

The Group Domain of Interpretation (GDOI, [RFC6407]) protocol, based on IKEv1 defines the support for Multicast Group SAs. For IKEv2, this work is currently in progress via [draft-ietf-ipsecme-g-ikev2]¶

7. IANA Considerations

This document instructs IANA to insert the following line at the top of the Notes section of the 'Internet Key Exchange (IKE) Attributes' registry and the '"Magic Numbers" for ISAKMP Protocol' registry: All registries listed below have been closed, see RFCxxxx. [Note to RFC Editor: change RFCxxx to this document's RFC number]¶

This document further instructs IANA to add an additional Status column to the IKEv2 Transform Type registries and mark the following entries as DEPRECATED:¶


          Transform Type 1 - Encryption Algorithm IDs

          Number    Name                Status
          ------    ---------------     ------
          1         ENCR_DES_IV64       DEPRECATED [this document]
          2         ENCR_DES            DEPRECATED [RFC8247]
          4         ENCR_RC5            DEPRECATED [this document]
          5         ENCR_IDEA           DEPRECATED [this document]
          6         ENCR_CAST           DEPRECATED [this document]
          7         ENCR_BLOWFISH       DEPRECATED [this document]
          8         ENCR_3IDEA          DEPRECATED [this document]
          9         ENCR_DES_IV32       DEPRECATED [this document]

Figure 1


          Transform Type 2 - Pseudorandom Function Transform IDs

          Number    Name                Status
          ------    ------------        ----------
          1         PRF_HMAC_MD5        DEPRECATED [RFC8247]
          3         PRF_HMAC_TIGER      DEPRECATED [this document]

Figure 2


          Transform Type 3 - Integrity Algorithm Transform IDs

          Number    Name                Status
          ------    -----------------   ----------
          1         AUTH_HMAC_MD5_96    DEPRECATED [RFC8247]
          3         AUTH_DES_MAC        DEPRECATED [RFC8247]
          4         AUTH_KPDK_MD5       DEPRECATED [RFC8247]
          6         AUTH_HMAC_MD5_128   DEPRECATED [this document]
          7         AUTH_HMAC_SHA1_160  DEPRECATED [this document]

Figure 3


          Transform Type 4 - Diffie Hellman Group Transform IDs

          Number    Name                           Status
          ------    ----------------------------   ----------
          1         768-bit MODP Group             DEPRECATED [RFC8247]
          22        1024-bit MODP Group with
                    160-bit Prime Order Subgroup   DEPRECATED [RFC8247]

Figure 4

All entries not mentioned here should receive no value in the new Status field.¶

8. References

8.1. Normative References

[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>.
[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>.
[RFC8247]: Nir, Y., Kivinen, T., Wouters, P., and D. Migault, "Algorithm Implementation Requirements and Usage Guidance for the Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 8247, DOI 10.17487/RFC8247, September 2017, <https://www.rfc-editor.org/info/rfc8247>.

8.2. Informative References

[CVE-2016-5361]: National Institute of Science and Technology (NIST), "National Vulnerability Database - CVE-2016-5361", 16 June 2016, <https://nvd.nist.gov/vuln/detail/CVE-2016-5361>.
[draft-ietf-ipsecme-g-ikev2]: Smyslov, V. and B. Weis, "Group Key Management using IKEv2", Work in Progress, Internet-Draft, draft-ietf-ipsecme-g-ikev2, 11 January 2021, <https://www.ietf.org/archive/id/draft-ietf-ipsecme-g-ikev2-03.txt>.
[draft-ietf-ipsecme-labeled-ipsec]: Wouters, P. and S. Prasad, "Labeled IPsec Traffic Selector support for IKEv2", Work in Progress, Internet-Draft, draft-ietf-ipsecme-labeled-ipsec, 25 October 2021, <https://tools.ietf.org/id/draft-ietf-ipsecme-labeled-ipsec-06.txt>.
[RFC2407]: Piper, D., "The Internet IP Security Domain of Interpretation for ISAKMP", RFC 2407, DOI 10.17487/RFC2407, November 1998, <https://www.rfc-editor.org/info/rfc2407>.
[RFC2408]: Maughan, D., Schertler, M., Schneider, M., and J. Turner, "Internet Security Association and Key Management Protocol (ISAKMP)", RFC 2408, DOI 10.17487/RFC2408, November 1998, <https://www.rfc-editor.org/info/rfc2408>.
[RFC2409]: Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, DOI 10.17487/RFC2409, November 1998, <https://www.rfc-editor.org/info/rfc2409>.
[RFC4306]: Kaufman, C., Ed., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, DOI 10.17487/RFC4306, December 2005, <https://www.rfc-editor.org/info/rfc4306>.
[RFC6407]: Weis, B., Rowles, S., and T. Hardjono, "The Group Domain of Interpretation", RFC 6407, DOI 10.17487/RFC6407, October 2011, <https://www.rfc-editor.org/info/rfc6407>.
[RFC7296]: Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC8221]: Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T. Kivinen, "Cryptographic Algorithm Implementation Requirements and Usage Guidance for Encapsulating Security Payload (ESP) and Authentication Header (AH)", RFC 8221, DOI 10.17487/RFC8221, October 2017, <https://www.rfc-editor.org/info/rfc8221>.
[RFC8784]: Fluhrer, S., Kampanakis, P., McGrew, D., and V. Smyslov, "Mixing Preshared Keys in the Internet Key Exchange Protocol Version 2 (IKEv2) for Post-quantum Security", RFC 8784, DOI 10.17487/RFC8784, June 2020, <https://www.rfc-editor.org/info/rfc8784>.