7225 lines
308 KiB
Text
7225 lines
308 KiB
Text
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Network Working Group C. Kaufman
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Internet-Draft Microsoft
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Obsoletes: 4306, 4718 P. Hoffman
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(if approved) VPN Consortium
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Intended status: Standards Track P. Eronen
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Expires: August 28, 2008 Nokia
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February 25, 2008
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Internet Key Exchange Protocol: IKEv2
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draft-hoffman-ikev2bis-03
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Status of this Memo
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By submitting this Internet-Draft, each author represents that any
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applicable patent or other IPR claims of which he or she is aware
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have been or will be disclosed, and any of which he or she becomes
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aware will be disclosed, in accordance with Section 6 of BCP 79.
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Internet-Drafts are working documents of the Internet Engineering
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Task Force (IETF), its areas, and its working groups. Note that
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other groups may also distribute working documents as Internet-
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Drafts.
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Internet-Drafts are draft documents valid for a maximum of six months
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and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
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material or to cite them other than as "work in progress."
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The list of current Internet-Drafts can be accessed at
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http://www.ietf.org/ietf/1id-abstracts.txt.
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The list of Internet-Draft Shadow Directories can be accessed at
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http://www.ietf.org/shadow.html.
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This Internet-Draft will expire on August 28, 2008.
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Copyright Notice
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Copyright (C) The IETF Trust (2008).
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Abstract
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This document describes version 2 of the Internet Key Exchange (IKE)
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protocol. It is a restatement of RFC 4306, and includes all of the
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clarifications from RFC 4718.
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Kaufman, et al. Expires August 28, 2008 [Page 1]
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Internet-Draft IKEv2bis February 2008
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Table of Contents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
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1.1. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . 6
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1.1.1. Security Gateway to Security Gateway Tunnel . . . . . 6
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1.1.2. Endpoint-to-Endpoint Transport . . . . . . . . . . . 7
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1.1.3. Endpoint to Security Gateway Tunnel . . . . . . . . . 8
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1.1.4. Other Scenarios . . . . . . . . . . . . . . . . . . . 8
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1.2. The Initial Exchanges . . . . . . . . . . . . . . . . . . 9
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1.3. The CREATE_CHILD_SA Exchange . . . . . . . . . . . . . . 11
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1.3.1. Creating New CHILD_SAs with the CREATE_CHILD_SA
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Exchange . . . . . . . . . . . . . . . . . . . . . . 13
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1.3.2. Rekeying IKE_SAs with the CREATE_CHILD_SA Exchange . 14
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1.3.3. Rekeying CHILD_SAs with the CREATE_CHILD_SA
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Exchange . . . . . . . . . . . . . . . . . . . . . . 14
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1.4. The INFORMATIONAL Exchange . . . . . . . . . . . . . . . 15
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1.5. Informational Messages outside of an IKE_SA . . . . . . . 17
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1.6. Requirements Terminology . . . . . . . . . . . . . . . . 17
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1.7. Differences Between RFC 4306 and This Document . . . . . 18
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2. IKE Protocol Details and Variations . . . . . . . . . . . . . 19
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2.1. Use of Retransmission Timers . . . . . . . . . . . . . . 20
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2.2. Use of Sequence Numbers for Message ID . . . . . . . . . 21
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2.3. Window Size for Overlapping Requests . . . . . . . . . . 21
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2.4. State Synchronization and Connection Timeouts . . . . . . 23
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2.5. Version Numbers and Forward Compatibility . . . . . . . . 25
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2.6. Cookies . . . . . . . . . . . . . . . . . . . . . . . . . 27
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2.6.1. Interaction of COOKIE and INVALID_KE_PAYLOAD . . . . 29
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2.7. Cryptographic Algorithm Negotiation . . . . . . . . . . . 30
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2.8. Rekeying . . . . . . . . . . . . . . . . . . . . . . . . 31
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2.8.1. Simultaneous CHILD_SA rekeying . . . . . . . . . . . 33
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2.8.2. Rekeying the IKE_SA Versus Reauthentication . . . . . 35
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2.9. Traffic Selector Negotiation . . . . . . . . . . . . . . 36
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2.9.1. Traffic Selectors Violating Own Policy . . . . . . . 38
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2.10. Nonces . . . . . . . . . . . . . . . . . . . . . . . . . 39
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2.11. Address and Port Agility . . . . . . . . . . . . . . . . 39
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2.12. Reuse of Diffie-Hellman Exponentials . . . . . . . . . . 40
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2.13. Generating Keying Material . . . . . . . . . . . . . . . 40
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2.14. Generating Keying Material for the IKE_SA . . . . . . . . 42
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2.15. Authentication of the IKE_SA . . . . . . . . . . . . . . 42
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2.16. Extensible Authentication Protocol Methods . . . . . . . 44
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2.17. Generating Keying Material for CHILD_SAs . . . . . . . . 46
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2.18. Rekeying IKE_SAs Using a CREATE_CHILD_SA Exchange . . . . 47
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2.19. Requesting an Internal Address on a Remote Network . . . 48
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2.19.1. Configuration Payloads . . . . . . . . . . . . . . . 49
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2.20. Requesting the Peer's Version . . . . . . . . . . . . . . 51
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2.21. Error Handling . . . . . . . . . . . . . . . . . . . . . 51
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2.22. IPComp . . . . . . . . . . . . . . . . . . . . . . . . . 52
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2.23. NAT Traversal . . . . . . . . . . . . . . . . . . . . . . 54
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Kaufman, et al. Expires August 28, 2008 [Page 2]
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Internet-Draft IKEv2bis February 2008
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2.24. Explicit Congestion Notification (ECN) . . . . . . . . . 57
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3. Header and Payload Formats . . . . . . . . . . . . . . . . . 57
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3.1. The IKE Header . . . . . . . . . . . . . . . . . . . . . 58
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3.2. Generic Payload Header . . . . . . . . . . . . . . . . . 61
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3.3. Security Association Payload . . . . . . . . . . . . . . 63
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3.3.1. Proposal Substructure . . . . . . . . . . . . . . . . 65
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3.3.2. Transform Substructure . . . . . . . . . . . . . . . 66
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3.3.3. Valid Transform Types by Protocol . . . . . . . . . . 69
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3.3.4. Mandatory Transform IDs . . . . . . . . . . . . . . . 70
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3.3.5. Transform Attributes . . . . . . . . . . . . . . . . 71
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3.3.6. Attribute Negotiation . . . . . . . . . . . . . . . . 73
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3.4. Key Exchange Payload . . . . . . . . . . . . . . . . . . 73
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3.5. Identification Payloads . . . . . . . . . . . . . . . . . 74
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3.6. Certificate Payload . . . . . . . . . . . . . . . . . . . 77
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3.7. Certificate Request Payload . . . . . . . . . . . . . . . 79
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3.8. Authentication Payload . . . . . . . . . . . . . . . . . 81
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3.9. Nonce Payload . . . . . . . . . . . . . . . . . . . . . . 82
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3.10. Notify Payload . . . . . . . . . . . . . . . . . . . . . 83
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3.10.1. Notify Message Types . . . . . . . . . . . . . . . . 84
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3.11. Delete Payload . . . . . . . . . . . . . . . . . . . . . 87
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3.12. Vendor ID Payload . . . . . . . . . . . . . . . . . . . . 89
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3.13. Traffic Selector Payload . . . . . . . . . . . . . . . . 90
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3.13.1. Traffic Selector . . . . . . . . . . . . . . . . . . 91
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3.14. Encrypted Payload . . . . . . . . . . . . . . . . . . . . 93
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3.15. Configuration Payload . . . . . . . . . . . . . . . . . . 95
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3.15.1. Configuration Attributes . . . . . . . . . . . . . . 96
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3.15.2. Meaning of INTERNAL_IP4_SUBNET/INTERNAL_IP6_SUBNET . 99
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3.15.3. Configuration payloads for IPv6 . . . . . . . . . . . 101
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3.15.4. Address Assignment Failures . . . . . . . . . . . . . 101
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3.16. Extensible Authentication Protocol (EAP) Payload . . . . 102
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4. Conformance Requirements . . . . . . . . . . . . . . . . . . 104
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5. Security Considerations . . . . . . . . . . . . . . . . . . . 106
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5.1. Traffic selector authorization . . . . . . . . . . . . . 108
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6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 109
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7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 110
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8. References . . . . . . . . . . . . . . . . . . . . . . . . . 110
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8.1. Normative References . . . . . . . . . . . . . . . . . . 110
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8.2. Informative References . . . . . . . . . . . . . . . . . 112
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Appendix A. Summary of changes from IKEv1 . . . . . . . . . . . 115
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Appendix B. Diffie-Hellman Groups . . . . . . . . . . . . . . . 117
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B.1. Group 1 - 768 Bit MODP . . . . . . . . . . . . . . . . . 117
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B.2. Group 2 - 1024 Bit MODP . . . . . . . . . . . . . . . . . 117
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Appendix C. Exchanges and Payloads . . . . . . . . . . . . . . . 118
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C.1. IKE_SA_INIT Exchange . . . . . . . . . . . . . . . . . . 118
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C.2. IKE_AUTH Exchange without EAP . . . . . . . . . . . . . . 119
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C.3. IKE_AUTH Exchange with EAP . . . . . . . . . . . . . . . 120
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C.4. CREATE_CHILD_SA Exchange for Creating or Rekeying
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CHILD_SAs . . . . . . . . . . . . . . . . . . . . . . . . 121
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Kaufman, et al. Expires August 28, 2008 [Page 3]
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C.5. CREATE_CHILD_SA Exchange for Rekeying the IKE_SA . . . . 121
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C.6. INFORMATIONAL Exchange . . . . . . . . . . . . . . . . . 121
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Appendix D. Changes Between Internet Draft Versions . . . . . . 121
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D.1. Changes from IKEv2 to draft -00 . . . . . . . . . . . . . 121
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D.2. Changes from draft -00 to draft -01 . . . . . . . . . . . 122
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D.3. Changes from draft -00 to draft -01 . . . . . . . . . . . 124
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D.4. Changes from draft -01 to draft -02 . . . . . . . . . . . 124
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D.5. Changes from draft -02 to draft -03 . . . . . . . . . . . 125
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 127
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Intellectual Property and Copyright Statements . . . . . . . . . 129
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Kaufman, et al. Expires August 28, 2008 [Page 4]
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Internet-Draft IKEv2bis February 2008
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1. Introduction
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{{ An introduction to the differences between RFC 4306 [IKEV2] and
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this document is given at the end of Section 1. It is put there
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(instead of here) to preserve the section numbering of RFC 4306. }}
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IP Security (IPsec) provides confidentiality, data integrity, access
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control, and data source authentication to IP datagrams. These
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services are provided by maintaining shared state between the source
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and the sink of an IP datagram. This state defines, among other
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things, the specific services provided to the datagram, which
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cryptographic algorithms will be used to provide the services, and
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the keys used as input to the cryptographic algorithms.
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Establishing this shared state in a manual fashion does not scale
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well. Therefore, a protocol to establish this state dynamically is
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needed. This memo describes such a protocol -- the Internet Key
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Exchange (IKE). Version 1 of IKE was defined in RFCs 2407 [DOI],
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2408 [ISAKMP], and 2409 [IKEV1]. IKEv2 was defined in [IKEV2] and
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clarified in [Clarif]. This single document is intended to replace
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all of those RFCs.
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IKE performs mutual authentication between two parties and
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establishes an IKE security association (SA) that includes shared
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secret information that can be used to efficiently establish SAs for
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Encapsulating Security Payload (ESP) [ESP] and/or Authentication
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Header (AH) [AH] and a set of cryptographic algorithms to be used by
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the SAs to protect the traffic that they carry. In this document,
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the term "suite" or "cryptographic suite" refers to a complete set of
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algorithms used to protect an SA. An initiator proposes one or more
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suites by listing supported algorithms that can be combined into
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suites in a mix-and-match fashion. IKE can also negotiate use of IP
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Compression (IPComp) [IPCOMP] in connection with an ESP and/or AH SA.
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We call the IKE SA an "IKE_SA". The SAs for ESP and/or AH that get
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set up through that IKE_SA we call "CHILD_SAs".
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All IKE communications consist of pairs of messages: a request and a
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response. The pair is called an "exchange". We call the first
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messages establishing an IKE_SA IKE_SA_INIT and IKE_AUTH exchanges
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and subsequent IKE exchanges CREATE_CHILD_SA or INFORMATIONAL
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exchanges. In the common case, there is a single IKE_SA_INIT
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exchange and a single IKE_AUTH exchange (a total of four messages) to
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establish the IKE_SA and the first CHILD_SA. In exceptional cases,
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there may be more than one of each of these exchanges. In all cases,
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all IKE_SA_INIT exchanges MUST complete before any other exchange
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type, then all IKE_AUTH exchanges MUST complete, and following that
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any number of CREATE_CHILD_SA and INFORMATIONAL exchanges may occur
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in any order. In some scenarios, only a single CHILD_SA is needed
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Kaufman, et al. Expires August 28, 2008 [Page 5]
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between the IPsec endpoints, and therefore there would be no
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additional exchanges. Subsequent exchanges MAY be used to establish
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additional CHILD_SAs between the same authenticated pair of endpoints
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and to perform housekeeping functions.
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IKE message flow always consists of a request followed by a response.
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It is the responsibility of the requester to ensure reliability. If
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the response is not received within a timeout interval, the requester
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needs to retransmit the request (or abandon the connection).
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The first request/response of an IKE session (IKE_SA_INIT) negotiates
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security parameters for the IKE_SA, sends nonces, and sends Diffie-
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Hellman values.
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The second request/response (IKE_AUTH) transmits identities, proves
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knowledge of the secrets corresponding to the two identities, and
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sets up an SA for the first (and often only) AH and/or ESP CHILD_SA.
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The types of subsequent exchanges are CREATE_CHILD_SA (which creates
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a CHILD_SA) and INFORMATIONAL (which deletes an SA, reports error
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conditions, or does other housekeeping). Every request requires a
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response. An INFORMATIONAL request with no payloads (other than the
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empty Encrypted payload required by the syntax) is commonly used as a
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check for liveness. These subsequent exchanges cannot be used until
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the initial exchanges have completed.
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In the description that follows, we assume that no errors occur.
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Modifications to the flow should errors occur are described in
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Section 2.21.
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1.1. Usage Scenarios
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IKE is expected to be used to negotiate ESP and/or AH SAs in a number
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of different scenarios, each with its own special requirements.
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1.1.1. Security Gateway to Security Gateway Tunnel
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+-+-+-+-+-+ +-+-+-+-+-+
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| | IPsec | |
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Protected |Tunnel | tunnel |Tunnel | Protected
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Subnet <-->|Endpoint |<---------->|Endpoint |<--> Subnet
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| | | |
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+-+-+-+-+-+ +-+-+-+-+-+
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Figure 1: Security Gateway to Security Gateway Tunnel
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In this scenario, neither endpoint of the IP connection implements
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IPsec, but network nodes between them protect traffic for part of the
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way. Protection is transparent to the endpoints, and depends on
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ordinary routing to send packets through the tunnel endpoints for
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processing. Each endpoint would announce the set of addresses
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"behind" it, and packets would be sent in tunnel mode where the inner
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IP header would contain the IP addresses of the actual endpoints.
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1.1.2. Endpoint-to-Endpoint Transport
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+-+-+-+-+-+ +-+-+-+-+-+
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| | IPsec transport | |
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|Protected| or tunnel mode SA |Protected|
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|Endpoint |<---------------------------------------->|Endpoint |
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| | | |
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+-+-+-+-+-+ +-+-+-+-+-+
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Figure 2: Endpoint to Endpoint
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In this scenario, both endpoints of the IP connection implement
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IPsec, as required of hosts in [IPSECARCH]. Transport mode will
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commonly be used with no inner IP header. If there is an inner IP
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header, the inner addresses will be the same as the outer addresses.
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A single pair of addresses will be negotiated for packets to be
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protected by this SA. These endpoints MAY implement application
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layer access controls based on the IPsec authenticated identities of
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the participants. This scenario enables the end-to-end security that
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has been a guiding principle for the Internet since [ARCHPRINC],
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[TRANSPARENCY], and a method of limiting the inherent problems with
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complexity in networks noted by [ARCHGUIDEPHIL]. Although this
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scenario may not be fully applicable to the IPv4 Internet, it has
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been deployed successfully in specific scenarios within intranets
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using IKEv1. It should be more broadly enabled during the transition
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to IPv6 and with the adoption of IKEv2.
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It is possible in this scenario that one or both of the protected
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endpoints will be behind a network address translation (NAT) node, in
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which case the tunneled packets will have to be UDP encapsulated so
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that port numbers in the UDP headers can be used to identify
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individual endpoints "behind" the NAT (see Section 2.23).
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Kaufman, et al. Expires August 28, 2008 [Page 7]
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Internet-Draft IKEv2bis February 2008
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1.1.3. Endpoint to Security Gateway Tunnel
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+-+-+-+-+-+ +-+-+-+-+-+
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| | IPsec | | Protected
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|Protected| tunnel |Tunnel | Subnet
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|Endpoint |<------------------------>|Endpoint |<--- and/or
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| | | | Internet
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+-+-+-+-+-+ +-+-+-+-+-+
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Figure 3: Endpoint to Security Gateway Tunnel
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In this scenario, a protected endpoint (typically a portable roaming
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computer) connects back to its corporate network through an IPsec-
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protected tunnel. It might use this tunnel only to access
|
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information on the corporate network, or it might tunnel all of its
|
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traffic back through the corporate network in order to take advantage
|
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of protection provided by a corporate firewall against Internet-based
|
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attacks. In either case, the protected endpoint will want an IP
|
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address associated with the security gateway so that packets returned
|
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to it will go to the security gateway and be tunneled back. This IP
|
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address may be static or may be dynamically allocated by the security
|
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gateway. {{ Clarif-6.1 }} In support of the latter case, IKEv2
|
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includes a mechanism (namely, configuration payloads) for the
|
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initiator to request an IP address owned by the security gateway for
|
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use for the duration of its SA.
|
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In this scenario, packets will use tunnel mode. On each packet from
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the protected endpoint, the outer IP header will contain the source
|
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IP address associated with its current location (i.e., the address
|
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that will get traffic routed to the endpoint directly), while the
|
||
inner IP header will contain the source IP address assigned by the
|
||
security gateway (i.e., the address that will get traffic routed to
|
||
the security gateway for forwarding to the endpoint). The outer
|
||
destination address will always be that of the security gateway,
|
||
while the inner destination address will be the ultimate destination
|
||
for the packet.
|
||
|
||
In this scenario, it is possible that the protected endpoint will be
|
||
behind a NAT. In that case, the IP address as seen by the security
|
||
gateway will not be the same as the IP address sent by the protected
|
||
endpoint, and packets will have to be UDP encapsulated in order to be
|
||
routed properly.
|
||
|
||
1.1.4. Other Scenarios
|
||
|
||
Other scenarios are possible, as are nested combinations of the
|
||
above. One notable example combines aspects of 1.1.1 and 1.1.3. A
|
||
subnet may make all external accesses through a remote security
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 8]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
gateway using an IPsec tunnel, where the addresses on the subnet are
|
||
routed to the security gateway by the rest of the Internet. An
|
||
example would be someone's home network being virtually on the
|
||
Internet with static IP addresses even though connectivity is
|
||
provided by an ISP that assigns a single dynamically assigned IP
|
||
address to the user's security gateway (where the static IP addresses
|
||
and an IPsec relay are provided by a third party located elsewhere).
|
||
|
||
1.2. The Initial Exchanges
|
||
|
||
Communication using IKE always begins with IKE_SA_INIT and IKE_AUTH
|
||
exchanges (known in IKEv1 as Phase 1). These initial exchanges
|
||
normally consist of four messages, though in some scenarios that
|
||
number can grow. All communications using IKE consist of request/
|
||
response pairs. We'll describe the base exchange first, followed by
|
||
variations. The first pair of messages (IKE_SA_INIT) negotiate
|
||
cryptographic algorithms, exchange nonces, and do a Diffie-Hellman
|
||
exchange [DH].
|
||
|
||
The second pair of messages (IKE_AUTH) authenticate the previous
|
||
messages, exchange identities and certificates, and establish the
|
||
first CHILD_SA. Parts of these messages are encrypted and integrity
|
||
protected with keys established through the IKE_SA_INIT exchange, so
|
||
the identities are hidden from eavesdroppers and all fields in all
|
||
the messages are authenticated.
|
||
|
||
In the following descriptions, the payloads contained in the message
|
||
are indicated by names as listed below.
|
||
|
||
Notation Payload
|
||
-----------------------------------------
|
||
AUTH Authentication
|
||
CERT Certificate
|
||
CERTREQ Certificate Request
|
||
CP Configuration
|
||
D Delete
|
||
E Encrypted
|
||
EAP Extensible Authentication
|
||
HDR IKE Header
|
||
IDi Identification - Initiator
|
||
IDr Identification - Responder
|
||
KE Key Exchange
|
||
Ni, Nr Nonce
|
||
N Notify
|
||
SA Security Association
|
||
TSi Traffic Selector - Initiator
|
||
TSr Traffic Selector - Responder
|
||
V Vendor ID
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 9]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
The details of the contents of each payload are described in section
|
||
3. Payloads that may optionally appear will be shown in brackets,
|
||
such as [CERTREQ], indicate that optionally a certificate request
|
||
payload can be included.
|
||
|
||
The initial exchanges are as follows:
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SAi1, KEi, Ni -->
|
||
|
||
HDR contains the Security Parameter Indexes (SPIs), version numbers,
|
||
and flags of various sorts. The SAi1 payload states the
|
||
cryptographic algorithms the initiator supports for the IKE_SA. The
|
||
KE payload sends the initiator's Diffie-Hellman value. Ni is the
|
||
initiator's nonce.
|
||
|
||
<-- HDR, SAr1, KEr, Nr, [CERTREQ]
|
||
|
||
The responder chooses a cryptographic suite from the initiator's
|
||
offered choices and expresses that choice in the SAr1 payload,
|
||
completes the Diffie-Hellman exchange with the KEr payload, and sends
|
||
its nonce in the Nr payload.
|
||
|
||
At this point in the negotiation, each party can generate SKEYSEED,
|
||
from which all keys are derived for that IKE_SA. All but the headers
|
||
of all the messages that follow are encrypted and integrity
|
||
protected. The keys used for the encryption and integrity protection
|
||
are derived from SKEYSEED and are known as SK_e (encryption) and SK_a
|
||
(authentication, a.k.a. integrity protection). A separate SK_e and
|
||
SK_a is computed for each direction. In addition to the keys SK_e
|
||
and SK_a derived from the DH value for protection of the IKE_SA,
|
||
another quantity SK_d is derived and used for derivation of further
|
||
keying material for CHILD_SAs. The notation SK { ... } indicates
|
||
that these payloads are encrypted and integrity protected using that
|
||
direction's SK_e and SK_a.
|
||
|
||
HDR, SK {IDi, [CERT,] [CERTREQ,]
|
||
[IDr,] AUTH, SAi2,
|
||
TSi, TSr} -->
|
||
|
||
The initiator asserts its identity with the IDi payload, proves
|
||
knowledge of the secret corresponding to IDi and integrity protects
|
||
the contents of the first message using the AUTH payload (see
|
||
Section 2.15). It might also send its certificate(s) in CERT
|
||
payload(s) and a list of its trust anchors in CERTREQ payload(s). If
|
||
any CERT payloads are included, the first certificate provided MUST
|
||
contain the public key used to verify the AUTH field. The optional
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 10]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
payload IDr enables the initiator to specify which of the responder's
|
||
identities it wants to talk to. This is useful when the machine on
|
||
which the responder is running is hosting multiple identities at the
|
||
same IP address. The initiator begins negotiation of a CHILD_SA
|
||
using the SAi2 payload. The final fields (starting with SAi2) are
|
||
described in the description of the CREATE_CHILD_SA exchange.
|
||
|
||
<-- HDR, SK {IDr, [CERT,] AUTH,
|
||
SAr2, TSi, TSr}
|
||
|
||
The responder asserts its identity with the IDr payload, optionally
|
||
sends one or more certificates (again with the certificate containing
|
||
the public key used to verify AUTH listed first), authenticates its
|
||
identity and protects the integrity of the second message with the
|
||
AUTH payload, and completes negotiation of a CHILD_SA with the
|
||
additional fields described below in the CREATE_CHILD_SA exchange.
|
||
|
||
The recipients of messages 3 and 4 MUST verify that all signatures
|
||
and MACs are computed correctly and that the names in the ID payloads
|
||
correspond to the keys used to generate the AUTH payload.
|
||
|
||
{{ Clarif-4.2}} If creating the CHILD_SA during the IKE_AUTH exchange
|
||
fails for some reason, the IKE_SA is still created as usual. The
|
||
list of responses in the IKE_AUTH exchange that do not prevent an
|
||
IKE_SA from being set up include at least the following:
|
||
NO_PROPOSAL_CHOSEN, TS_UNACCEPTABLE, SINGLE_PAIR_REQUIRED,
|
||
INTERNAL_ADDRESS_FAILURE, and FAILED_CP_REQUIRED.
|
||
|
||
{{ Clarif-4.3 }} Note that IKE_AUTH messages do not contain KEi/KEr
|
||
or Ni/Nr payloads. Thus, the SA payloads in the IKE_AUTH exchange
|
||
cannot contain Transform Type 4 (Diffie-Hellman Group) with any value
|
||
other than NONE. Implementations SHOULD omit the whole transform
|
||
substructure instead of sending value NONE.
|
||
|
||
1.3. The CREATE_CHILD_SA Exchange
|
||
|
||
{{ This is a heavy rewrite of most of this section. The major
|
||
organization changes are described in Clarif-4.1 and Clarif-5.1. }}
|
||
|
||
The CREATE_CHILD_SA exchange is used to create new CHILD_SAs and to
|
||
rekey both IKE_SAs and CHILD_SAs. This exchange consists of a single
|
||
request/response pair, and some of its function was referred to as a
|
||
phase 2 exchange in IKEv1. It MAY be initiated by either end of the
|
||
IKE_SA after the initial exchanges are completed.
|
||
|
||
All messages following the initial exchange are cryptographically
|
||
protected using the cryptographic algorithms and keys negotiated in
|
||
the first two messages of the IKE exchange. These subsequent
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 11]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
messages use the syntax of the Encrypted Payload described in
|
||
Section 3.14. All subsequent messages include an Encrypted Payload,
|
||
even if they are referred to in the text as "empty". For both
|
||
messages in the CREATE_CHILD_SA, the message following the header is
|
||
encrypted and the message including the header is integrity protected
|
||
using the cryptographic algorithms negotiated for the IKE_SA.
|
||
|
||
The CREATE_CHILD_SA is also used for rekeying IKE_SAs and CHILD_SAs.
|
||
An SA is rekeyed by creating a new SA and then deleting the old one.
|
||
This section describes the first part of rekeying, the creation of
|
||
new SAs; Section 2.8 covers the mechanics of rekeying, including
|
||
moving traffic from old to new SAs and the deletion of the old SAs.
|
||
The two sections must be read together to understand the entire
|
||
process of rekeying.
|
||
|
||
Either endpoint may initiate a CREATE_CHILD_SA exchange, so in this
|
||
section the term initiator refers to the endpoint initiating this
|
||
exchange. An implementation MAY refuse all CREATE_CHILD_SA requests
|
||
within an IKE_SA.
|
||
|
||
The CREATE_CHILD_SA request MAY optionally contain a KE payload for
|
||
an additional Diffie-Hellman exchange to enable stronger guarantees
|
||
of forward secrecy for the CHILD_SA. The keying material for the
|
||
CHILD_SA is a function of SK_d established during the establishment
|
||
of the IKE_SA, the nonces exchanged during the CREATE_CHILD_SA
|
||
exchange, and the Diffie-Hellman value (if KE payloads are included
|
||
in the CREATE_CHILD_SA exchange).
|
||
|
||
If a CREATE_CHILD_SA exchange includes a KEi payload, at least one of
|
||
the SA offers MUST include the Diffie-Hellman group of the KEi. The
|
||
Diffie-Hellman group of the KEi MUST be an element of the group the
|
||
initiator expects the responder to accept (additional Diffie-Hellman
|
||
groups can be proposed). If the responder selects a proposal using a
|
||
different Diffie-Hellman group (other than NONE), the responder MUST
|
||
reject the request and indicate its preferred Diffie-Hellman group in
|
||
the INVALID_KE_PAYLOAD Notification payload. {{ 3.10.1-17 }} There
|
||
are two octets of data associated with this notification: the
|
||
accepted D-H Group number in big endian order. In the case of such a
|
||
rejection, the CREATE_CHILD_SA exchange fails, and the initiator will
|
||
probably retry the exchange with a Diffie-Hellman proposal and KEi in
|
||
the group that the responder gave in the INVALID_KE_PAYLOAD.
|
||
|
||
{{ 3.10.1-35 }} The responder sends a NO_ADDITIONAL_SAS notification
|
||
to indicate that a CREATE_CHILD_SA request is unacceptable because
|
||
the responder is unwilling to accept any more CHILD_SAs on this
|
||
IKE_SA. Some minimal implementations may only accept a single
|
||
CHILD_SA setup in the context of an initial IKE exchange and reject
|
||
any subsequent attempts to add more.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 12]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1.3.1. Creating New CHILD_SAs with the CREATE_CHILD_SA Exchange
|
||
|
||
A CHILD_SA may be created by sending a CREATE_CHILD_SA request. The
|
||
CREATE_CHILD_SA request for creating a new CHILD_SA is:
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SK {SA, Ni, [KEi],
|
||
TSi, TSr} -->
|
||
|
||
The initiator sends SA offer(s) in the SA payload, a nonce in the Ni
|
||
payload, optionally a Diffie-Hellman value in the KEi payload, and
|
||
the proposed traffic selectors for the proposed CHILD_SA in the TSi
|
||
and TSr payloads.
|
||
|
||
The CREATE_CHILD_SA response for creating a new CHILD_SA is:
|
||
|
||
<-- HDR, SK {SA, Nr, [KEr],
|
||
TSi, TSr}
|
||
|
||
The responder replies (using the same Message ID to respond) with the
|
||
accepted offer in an SA payload, and a Diffie-Hellman value in the
|
||
KEr payload if KEi was included in the request and the selected
|
||
cryptographic suite includes that group.
|
||
|
||
The traffic selectors for traffic to be sent on that SA are specified
|
||
in the TS payloads in the response, which may be a subset of what the
|
||
initiator of the CHILD_SA proposed.
|
||
|
||
{{ 3.10.1-16391 }} The USE_TRANSPORT_MODE notification MAY be
|
||
included in a request message that also includes an SA payload
|
||
requesting a CHILD_SA. It requests that the CHILD_SA use transport
|
||
mode rather than tunnel mode for the SA created. If the request is
|
||
accepted, the response MUST also include a notification of type
|
||
USE_TRANSPORT_MODE. If the responder declines the request, the
|
||
CHILD_SA will be established in tunnel mode. If this is unacceptable
|
||
to the initiator, the initiator MUST delete the SA. Note: Except
|
||
when using this option to negotiate transport mode, all CHILD_SAs
|
||
will use tunnel mode.
|
||
|
||
{{ 3.10.1-16394 }} The ESP_TFC_PADDING_NOT_SUPPORTED notification
|
||
asserts that the sending endpoint will NOT accept packets that
|
||
contain Traffic Flow Confidentiality (TFC) padding over the CHILD_SA
|
||
being negotiated. {{ Clarif-4.5 }} If neither endpoint accepts TFC
|
||
padding, this notification is included in both the request and the
|
||
response. If this notification is included in only one of the
|
||
messages, TFC padding can still be sent in the other direction.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 13]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
{{ 3.10.1-16395 }} The NON_FIRST_FRAGMENTS_ALSO notification is used
|
||
for fragmentation control. See [IPSECARCH] for a fuller explanation.
|
||
{{ Clarif-4.6 }} Sending non-first fragments is enabled only if
|
||
NON_FIRST_FRAGMENTS_ALSO notification is included in both the request
|
||
proposing an SA and the response accepting it. If the peer rejects
|
||
the proposal of the SA, the peer only omits NON_FIRST_FRAGMENTS_ALSO
|
||
notification from the response, but does not reject the whole
|
||
CHILD_SA creation.
|
||
|
||
1.3.2. Rekeying IKE_SAs with the CREATE_CHILD_SA Exchange
|
||
|
||
The CREATE_CHILD_SA request for rekeying an IKE_SA is:
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SK {SA, Ni, [KEi]} -->
|
||
|
||
The initiator sends SA offer(s) in the SA payload, a nonce in the Ni
|
||
payload, and a Diffie-Hellman value in the KEi payload. The KEi
|
||
payload SHOULD be included. New initiator and responder SPIs are
|
||
supplied in the SPI fields.
|
||
|
||
The CREATE_CHILD_SA response for rekeying an IKE_SA is:
|
||
|
||
<-- HDR, SK {SA, Nr,[KEr]}
|
||
|
||
The responder replies (using the same Message ID to respond) with the
|
||
accepted offer in an SA payload, and a Diffie-Hellman value in the
|
||
KEr payload if the selected cryptographic suite includes that group.
|
||
|
||
The new IKE_SA has its message counters set to 0, regardless of what
|
||
they were in the earlier IKE_SA. The window size starts at 1 for any
|
||
new IKE_SA.
|
||
|
||
1.3.3. Rekeying CHILD_SAs with the CREATE_CHILD_SA Exchange
|
||
|
||
The CREATE_CHILD_SA request for rekeying a CHILD_SA is:
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SK {N, SA, Ni, [KEi],
|
||
TSi, TSr} -->
|
||
|
||
The initiator sends SA offer(s) in the SA payload, a nonce in the Ni
|
||
payload, optionally a Diffie-Hellman value in the KEi payload, and
|
||
the proposed traffic selectors for the proposed CHILD_SA in the TSi
|
||
and TSr payloads.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 14]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
{{ 3.10.1-16393 }} The REKEY_SA notification MUST be included in a
|
||
CREATE_CHILD_SA exchange if the purpose of the exchange is to replace
|
||
an existing ESP or AH SA. {{ Clarif-5.4 }} The SA being rekeyed is
|
||
identified by the SPI field in the Notify payload; this is the SPI
|
||
the exchange initiator would expect in inbound ESP or AH packets.
|
||
There is no data associated with this Notify type.
|
||
|
||
The CREATE_CHILD_SA response for rekeying a CHILD_SA is:
|
||
|
||
<-- HDR, SK {SA, Nr, [KEr],
|
||
Si, TSr}
|
||
|
||
The responder replies (using the same Message ID to respond) with the
|
||
accepted offer in an SA payload, and a Diffie-Hellman value in the
|
||
KEr payload if KEi was included in the request and the selected
|
||
cryptographic suite includes that group.
|
||
|
||
The traffic selectors for traffic to be sent on that SA are specified
|
||
in the TS payloads in the response, which may be a subset of what the
|
||
initiator of the CHILD_SA proposed.
|
||
|
||
1.4. The INFORMATIONAL Exchange
|
||
|
||
At various points during the operation of an IKE_SA, peers may desire
|
||
to convey control messages to each other regarding errors or
|
||
notifications of certain events. To accomplish this, IKE defines an
|
||
INFORMATIONAL exchange. INFORMATIONAL exchanges MUST ONLY occur
|
||
after the initial exchanges and are cryptographically protected with
|
||
the negotiated keys.
|
||
|
||
Control messages that pertain to an IKE_SA MUST be sent under that
|
||
IKE_SA. Control messages that pertain to CHILD_SAs MUST be sent
|
||
under the protection of the IKE_SA which generated them (or its
|
||
successor if the IKE_SA was replaced for the purpose of rekeying).
|
||
|
||
Messages in an INFORMATIONAL exchange contain zero or more
|
||
Notification, Delete, and Configuration payloads. The Recipient of
|
||
an INFORMATIONAL exchange request MUST send some response (else the
|
||
Sender will assume the message was lost in the network and will
|
||
retransmit it). That response MAY be a message with no payloads.
|
||
The request message in an INFORMATIONAL exchange MAY also contain no
|
||
payloads. This is the expected way an endpoint can ask the other
|
||
endpoint to verify that it is alive.
|
||
|
||
{{ Clarif-5.6 }} ESP and AH SAs always exist in pairs, with one SA in
|
||
each direction. When an SA is closed, both members of the pair MUST
|
||
be closed (that is, deleted). Each endpoint MUST close its incoming
|
||
SAs and allow the other endpoint to close the other SA in each pair.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 15]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
To delete an SA, an INFORMATIONAL exchange with one or more delete
|
||
payloads is sent listing the SPIs (as they would be expected in the
|
||
headers of inbound packets) of the SAs to be deleted. The recipient
|
||
MUST close the designated SAs. {{ Clarif-5.7 }} Note that one never
|
||
sends delete payloads for the two sides of an SA in a single message.
|
||
If there are many SAs to delete at the same time, one includes delete
|
||
payloads for in inbound half of each SA pair in your Informational
|
||
exchange.
|
||
|
||
Normally, the reply in the INFORMATIONAL exchange will contain delete
|
||
payloads for the paired SAs going in the other direction. There is
|
||
one exception. If by chance both ends of a set of SAs independently
|
||
decide to close them, each may send a delete payload and the two
|
||
requests may cross in the network. If a node receives a delete
|
||
request for SAs for which it has already issued a delete request, it
|
||
MUST delete the outgoing SAs while processing the request and the
|
||
incoming SAs while processing the response. In that case, the
|
||
responses MUST NOT include delete payloads for the deleted SAs, since
|
||
that would result in duplicate deletion and could in theory delete
|
||
the wrong SA.
|
||
|
||
{{ Demoted the SHOULD }} Half-closed ESP or AH connections are
|
||
anomalous, and a node with auditing capability should probably audit
|
||
their existence if they persist. Note that this specification
|
||
nowhere specifies time periods, so it is up to individual endpoints
|
||
to decide how long to wait. A node MAY refuse to accept incoming
|
||
data on half-closed connections but MUST NOT unilaterally close them
|
||
and reuse the SPIs. If connection state becomes sufficiently messed
|
||
up, a node MAY close the IKE_SA; doing so will implicitly close all
|
||
SAs negotiated under it. It can then rebuild the SAs it needs on a
|
||
clean base under a new IKE_SA. {{ Clarif-5.8 }} The response to a
|
||
request that deletes the IKE_SA is an empty Informational response.
|
||
|
||
The INFORMATIONAL exchange is defined as:
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SK {[N,] [D,]
|
||
[CP,] ...} -->
|
||
<-- HDR, SK {[N,] [D,]
|
||
[CP], ...}
|
||
|
||
The processing of an INFORMATIONAL exchange is determined by its
|
||
component payloads.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 16]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1.5. Informational Messages outside of an IKE_SA
|
||
|
||
If an encrypted IKE request packet arrives on port 500 or 4500 with
|
||
an unrecognized SPI, it could be because the receiving node has
|
||
recently crashed and lost state or because of some other system
|
||
malfunction or attack. If the receiving node has an active IKE_SA to
|
||
the IP address from whence the packet came, it MAY send a
|
||
notification of the wayward packet over that IKE_SA in an
|
||
INFORMATIONAL exchange. If it does not have such an IKE_SA, it MAY
|
||
send an Informational message without cryptographic protection to the
|
||
source IP address. Such a message is not part of an informational
|
||
exchange, and the receiving node MUST NOT respond to it. Doing so
|
||
could cause a message loop.
|
||
|
||
{{ 3.10.1-11 }} The INVALID_SPI notification MAY be sent in an IKE
|
||
INFORMATIONAL exchange when a node receives an ESP or AH packet with
|
||
an invalid SPI. The Notification Data contains the SPI of the
|
||
invalid packet. This usually indicates a node has rebooted and
|
||
forgotten an SA. If this Informational Message is sent outside the
|
||
context of an IKE_SA, it should only be used by the recipient as a
|
||
"hint" that something might be wrong (because it could easily be
|
||
forged).
|
||
|
||
{{ Clarif-7.7 }} There are two cases when such a one-way notification
|
||
is sent: INVALID_IKE_SPI and INVALID_SPI. These notifications are
|
||
sent outside of an IKE_SA. Note that such notifications are
|
||
explicitly not Informational exchanges; these are one-way messages
|
||
that must not be responded to. In case of INVALID_IKE_SPI, the
|
||
message sent is a response message, and thus it is sent to the IP
|
||
address and port from whence it came with the same IKE SPIs and the
|
||
Message ID copied. In case of INVALID_SPI, however, there are no IKE
|
||
SPI values that would be meaningful to the recipient of such a
|
||
notification. Using zero values or random values are both
|
||
acceptable.
|
||
|
||
1.6. Requirements Terminology
|
||
|
||
Definitions of the primitive terms in this document (such as Security
|
||
Association or SA) can be found in [IPSECARCH]. {{ Clarif-7.2 }} It
|
||
should be noted that parts of IKEv2 rely on some of the processing
|
||
rules in [IPSECARCH], as described in various sections of this
|
||
document.
|
||
|
||
Keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT" and
|
||
"MAY" that appear in this document are to be interpreted as described
|
||
in [MUSTSHOULD].
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 17]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1.7. Differences Between RFC 4306 and This Document
|
||
|
||
{{ Added this entire section, including this recursive remark. }}
|
||
|
||
This document contains clarifications and amplifications to IKEv2
|
||
[IKEV2]. The clarifications are mostly based on [Clarif]. The
|
||
changes listed in that document were discussed in the IPsec Working
|
||
Group and, after the Working Group was disbanded, on the IPsec
|
||
mailing list. That document contains detailed explanations of areas
|
||
that were unclear in IKEv2, and is thus useful to implementers of
|
||
IKEv2.
|
||
|
||
The protocol described in this document retains the same major
|
||
version number (2) and minor version number (0) as was used in RFC
|
||
4306.
|
||
|
||
This document makes the figures and references a bit more regular
|
||
than in [IKEV2].
|
||
|
||
IKEv2 developers have noted that the SHOULD-level requirements are
|
||
often unclear in that they don't say when it is OK to not obey the
|
||
requirements. They also have noted that there are MUST-level
|
||
requirements that are not related to interoperability. This document
|
||
has more explanation of some of these requirements. All non-
|
||
capitalized uses of the words SHOULD and MUST now mean their normal
|
||
English sense, not the interoperability sense of [MUSTSHOULD].
|
||
|
||
IKEv2 (and IKEv1) developers have noted that there is a great deal of
|
||
material in the tables of codes in Section 3.10.1. This leads to
|
||
implementers not having all the needed information in the main body
|
||
of the docment. Much of the material from those tables has been
|
||
moved into the associated parts of the main body of the document.
|
||
|
||
In the body of this document, notes that are enclosed in double curly
|
||
braces {{ such as this }} point out changes from IKEv2. Changes that
|
||
come from [Clarif] are marked with the section from that document,
|
||
such as "{{ Clarif-2.10 }}". Changes that come from moving
|
||
descriptive text out of the tables in Section 3.10.1 are marked with
|
||
that number and the message type that contained the text, such as "{{
|
||
3.10.1-16384 }}".
|
||
|
||
This document removes discussion of nesting AH and ESP. This was a
|
||
mistake in RFC 4306 caused by the lag between finishing RFC 4306 and
|
||
RFC 4301. Basically, IKEv2 is based on RFC 4301, which does not
|
||
include "SA bundles" that were part of RFC 2401. While a single
|
||
packet can go through IPsec processing multiple times, each of these
|
||
passes uses a separate SA, and the passes are coordinated by the
|
||
forwarding tables. In IKEv2, each of these SAs has to be created
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 18]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
using a separate CREATE_CHILD_SA exchange.
|
||
|
||
This document removes discussion of the INTERNAL_ADDRESS_EXPIRY
|
||
configuration attribute because its implementation was very
|
||
problematic. Implementations that conform to this document MUST
|
||
ignore proposals that have configuration attribute type 5, the old
|
||
value for INTERNAL_ADDRESS_EXPIRY.
|
||
|
||
This document adds the restriction in Section 2.13 that all PRFs used
|
||
with IKEv2 MUST take variable-sized keys. This should not affect any
|
||
implementations because there were no standardized PRFs that have
|
||
fixed-size keys.
|
||
|
||
A later version of this document may have all the {{ }} comments
|
||
removed from the body of the document and instead appear in an
|
||
appendix.
|
||
|
||
|
||
2. IKE Protocol Details and Variations
|
||
|
||
IKE normally listens and sends on UDP port 500, though IKE messages
|
||
may also be received on UDP port 4500 with a slightly different
|
||
format (see Section 2.23). Since UDP is a datagram (unreliable)
|
||
protocol, IKE includes in its definition recovery from transmission
|
||
errors, including packet loss, packet replay, and packet forgery.
|
||
IKE is designed to function so long as (1) at least one of a series
|
||
of retransmitted packets reaches its destination before timing out;
|
||
and (2) the channel is not so full of forged and replayed packets so
|
||
as to exhaust the network or CPU capacities of either endpoint. Even
|
||
in the absence of those minimum performance requirements, IKE is
|
||
designed to fail cleanly (as though the network were broken).
|
||
|
||
Although IKEv2 messages are intended to be short, they contain
|
||
structures with no hard upper bound on size (in particular, X.509
|
||
certificates), and IKEv2 itself does not have a mechanism for
|
||
fragmenting large messages. IP defines a mechanism for fragmentation
|
||
of oversize UDP messages, but implementations vary in the maximum
|
||
message size supported. Furthermore, use of IP fragmentation opens
|
||
an implementation to denial of service attacks [DOSUDPPROT].
|
||
Finally, some NAT and/or firewall implementations may block IP
|
||
fragments.
|
||
|
||
All IKEv2 implementations MUST be able to send, receive, and process
|
||
IKE messages that are up to 1280 octets long, and they SHOULD be able
|
||
to send, receive, and process messages that are up to 3000 octets
|
||
long. {{ Demoted the SHOULD }} IKEv2 implementations need to be aware
|
||
of the maximum UDP message size supported and MAY shorten messages by
|
||
leaving out some certificates or cryptographic suite proposals if
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 19]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
that will keep messages below the maximum. Use of the "Hash and URL"
|
||
formats rather than including certificates in exchanges where
|
||
possible can avoid most problems. {{ Demoted the SHOULD }}
|
||
Implementations and configuration need to keep in mind, however, that
|
||
if the URL lookups are possible only after the IPsec SA is
|
||
established, recursion issues could prevent this technique from
|
||
working.
|
||
|
||
{{ Clarif-7.5 }} The UDP payload of all packets containing IKE
|
||
messages sent on port 4500 MUST begin with the prefix of four zeros;
|
||
otherwise, the receiver won't know how to handle them.
|
||
|
||
2.1. Use of Retransmission Timers
|
||
|
||
All messages in IKE exist in pairs: a request and a response. The
|
||
setup of an IKE_SA normally consists of two request/response pairs.
|
||
Once the IKE_SA is set up, either end of the security association may
|
||
initiate requests at any time, and there can be many requests and
|
||
responses "in flight" at any given moment. But each message is
|
||
labeled as either a request or a response, and for each request/
|
||
response pair one end of the security association is the initiator
|
||
and the other is the responder.
|
||
|
||
For every pair of IKE messages, the initiator is responsible for
|
||
retransmission in the event of a timeout. The responder MUST never
|
||
retransmit a response unless it receives a retransmission of the
|
||
request. In that event, the responder MUST ignore the retransmitted
|
||
request except insofar as it triggers a retransmission of the
|
||
response. The initiator MUST remember each request until it receives
|
||
the corresponding response. The responder MUST remember each
|
||
response until it receives a request whose sequence number is larger
|
||
than or equal to the sequence number in the response plus its window
|
||
size (see Section 2.3).
|
||
|
||
IKE is a reliable protocol, in the sense that the initiator MUST
|
||
retransmit a request until either it receives a corresponding reply
|
||
OR it deems the IKE security association to have failed and it
|
||
discards all state associated with the IKE_SA and any CHILD_SAs
|
||
negotiated using that IKE_SA.
|
||
|
||
{{ Clarif-2.3 }} Retransmissions of the IKE_SA_INIT request require
|
||
some special handling. When a responder receives an IKE_SA_INIT
|
||
request, it has to determine whether the packet is retransmission
|
||
belonging to an existing "half-open" IKE_SA (in which case the
|
||
responder retransmits the same response), or a new request (in which
|
||
case the responder creates a new IKE_SA and sends a fresh response),
|
||
or it belongs to an existing IKE_SA where the IKE_AUTH request has
|
||
been already received (in which case the responder ignores it).
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 20]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
It is not sufficient to use the initiator's SPI and/or IP address to
|
||
differentiate between these three cases because two different peers
|
||
behind a single NAT could choose the same initiator SPI. Instead, a
|
||
robust responder will do the IKE_SA lookup using the whole packet,
|
||
its hash, or the Ni payload.
|
||
|
||
2.2. Use of Sequence Numbers for Message ID
|
||
|
||
Every IKE message contains a Message ID as part of its fixed header.
|
||
This Message ID is used to match up requests and responses, and to
|
||
identify retransmissions of messages.
|
||
|
||
The Message ID is a 32-bit quantity, which is zero for the
|
||
IKE_SA_INIT messages (including retries of the message due to
|
||
responses such as COOKIE and INVALID_KE_PAYLOAD {{ Clarif-2.2 }}),
|
||
and incremented for each subsequent exchange. Thus, the first pair
|
||
of IKE_AUTH messages will have ID of 1, the second (when EAP is used)
|
||
will be 2, and so on. {{ Clarif-3.10 }}
|
||
|
||
Each endpoint in the IKE Security Association maintains two "current"
|
||
Message IDs: the next one to be used for a request it initiates and
|
||
the next one it expects to see in a request from the other end.
|
||
These counters increment as requests are generated and received.
|
||
Responses always contain the same message ID as the corresponding
|
||
request. That means that after the initial exchange, each integer n
|
||
may appear as the message ID in four distinct messages: the nth
|
||
request from the original IKE initiator, the corresponding response,
|
||
the nth request from the original IKE responder, and the
|
||
corresponding response. If the two ends make very different numbers
|
||
of requests, the Message IDs in the two directions can be very
|
||
different. There is no ambiguity in the messages, however, because
|
||
the (I)nitiator and (R)esponse bits in the message header specify
|
||
which of the four messages a particular one is.
|
||
|
||
Note that Message IDs are cryptographically protected and provide
|
||
protection against message replays. In the unlikely event that
|
||
Message IDs grow too large to fit in 32 bits, the IKE_SA MUST be
|
||
closed. Rekeying an IKE_SA resets the sequence numbers.
|
||
|
||
2.3. Window Size for Overlapping Requests
|
||
|
||
In order to maximize IKE throughput, an IKE endpoint MAY issue
|
||
multiple requests before getting a response to any of them if the
|
||
other endpoint has indicated its ability to handle such requests.
|
||
For simplicity, an IKE implementation MAY choose to process requests
|
||
strictly in order and/or wait for a response to one request before
|
||
issuing another. Certain rules must be followed to ensure
|
||
interoperability between implementations using different strategies.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 21]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
After an IKE_SA is set up, either end can initiate one or more
|
||
requests. These requests may pass one another over the network. An
|
||
IKE endpoint MUST be prepared to accept and process a request while
|
||
it has a request outstanding in order to avoid a deadlock in this
|
||
situation. {{ Downgraded the SHOULD }} An IKE endpoint may also
|
||
accept and process multiple requests while it has a request
|
||
outstanding.
|
||
|
||
{{ 3.10.1-16385 }} The SET_WINDOW_SIZE notification asserts that the
|
||
sending endpoint is capable of keeping state for multiple outstanding
|
||
exchanges, permitting the recipient to send multiple requests before
|
||
getting a response to the first. The data associated with a
|
||
SET_WINDOW_SIZE notification MUST be 4 octets long and contain the
|
||
big endian representation of the number of messages the sender
|
||
promises to keep. The window size is always one until the initial
|
||
exchanges complete.
|
||
|
||
An IKE endpoint MUST wait for a response to each of its messages
|
||
before sending a subsequent message unless it has received a
|
||
SET_WINDOW_SIZE Notify message from its peer informing it that the
|
||
peer is prepared to maintain state for multiple outstanding messages
|
||
in order to allow greater throughput.
|
||
|
||
An IKE endpoint MUST NOT exceed the peer's stated window size for
|
||
transmitted IKE requests. In other words, if the responder stated
|
||
its window size is N, then when the initiator needs to make a request
|
||
X, it MUST wait until it has received responses to all requests up
|
||
through request X-N. An IKE endpoint MUST keep a copy of (or be able
|
||
to regenerate exactly) each request it has sent until it receives the
|
||
corresponding response. An IKE endpoint MUST keep a copy of (or be
|
||
able to regenerate exactly) the number of previous responses equal to
|
||
its declared window size in case its response was lost and the
|
||
initiator requests its retransmission by retransmitting the request.
|
||
|
||
An IKE endpoint supporting a window size greater than one ought to be
|
||
capable of processing incoming requests out of order to maximize
|
||
performance in the event of network failures or packet reordering.
|
||
|
||
{{ Clarif-7.3 }} The window size is normally a (possibly
|
||
configurable) property of a particular implementation, and is not
|
||
related to congestion control (unlike the window size in TCP, for
|
||
example). In particular, it is not defined what the responder should
|
||
do when it receives a SET_WINDOW_SIZE notification containing a
|
||
smaller value than is currently in effect. Thus, there is currently
|
||
no way to reduce the window size of an existing IKE_SA; you can only
|
||
increase it. When rekeying an IKE_SA, the new IKE_SA starts with
|
||
window size 1 until it is explicitly increased by sending a new
|
||
SET_WINDOW_SIZE notification.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 22]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
{{ 3.10.1-9 }}The INVALID_MESSAGE_ID notification is sent when an IKE
|
||
message ID outside the supported window is received. This Notify
|
||
MUST NOT be sent in a response; the invalid request MUST NOT be
|
||
acknowledged. Instead, inform the other side by initiating an
|
||
INFORMATIONAL exchange with Notification data containing the four
|
||
octet invalid message ID. Sending this notification is optional, and
|
||
notifications of this type MUST be rate limited.
|
||
|
||
2.4. State Synchronization and Connection Timeouts
|
||
|
||
An IKE endpoint is allowed to forget all of its state associated with
|
||
an IKE_SA and the collection of corresponding CHILD_SAs at any time.
|
||
This is the anticipated behavior in the event of an endpoint crash
|
||
and restart. It is important when an endpoint either fails or
|
||
reinitializes its state that the other endpoint detect those
|
||
conditions and not continue to waste network bandwidth by sending
|
||
packets over discarded SAs and having them fall into a black hole.
|
||
|
||
{{ 3.10.1-16384 }} The INITIAL_CONTACT notification asserts that this
|
||
IKE_SA is the only IKE_SA currently active between the authenticated
|
||
identities. It MAY be sent when an IKE_SA is established after a
|
||
crash, and the recipient MAY use this information to delete any other
|
||
IKE_SAs it has to the same authenticated identity without waiting for
|
||
a timeout. This notification MUST NOT be sent by an entity that may
|
||
be replicated (e.g., a roaming user's credentials where the user is
|
||
allowed to connect to the corporate firewall from two remote systems
|
||
at the same time). {{ Clarif-7.9 }} The INITIAL_CONTACT notification,
|
||
if sent, MUST be in the first IKE_AUTH request, not as a separate
|
||
exchange afterwards; however, receiving parties need to deal with it
|
||
in other requests.
|
||
|
||
Since IKE is designed to operate in spite of Denial of Service (DoS)
|
||
attacks from the network, an endpoint MUST NOT conclude that the
|
||
other endpoint has failed based on any routing information (e.g.,
|
||
ICMP messages) or IKE messages that arrive without cryptographic
|
||
protection (e.g., Notify messages complaining about unknown SPIs).
|
||
An endpoint MUST conclude that the other endpoint has failed only
|
||
when repeated attempts to contact it have gone unanswered for a
|
||
timeout period or when a cryptographically protected INITIAL_CONTACT
|
||
notification is received on a different IKE_SA to the same
|
||
authenticated identity. {{ Demoted the SHOULD }} An endpoint should
|
||
suspect that the other endpoint has failed based on routing
|
||
information and initiate a request to see whether the other endpoint
|
||
is alive. To check whether the other side is alive, IKE specifies an
|
||
empty INFORMATIONAL message that (like all IKE requests) requires an
|
||
acknowledgement (note that within the context of an IKE_SA, an
|
||
"empty" message consists of an IKE header followed by an Encrypted
|
||
payload that contains no payloads). If a cryptographically protected
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 23]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
message has been received from the other side recently, unprotected
|
||
notifications MAY be ignored. Implementations MUST limit the rate at
|
||
which they take actions based on unprotected messages.
|
||
|
||
Numbers of retries and lengths of timeouts are not covered in this
|
||
specification because they do not affect interoperability. It is
|
||
suggested that messages be retransmitted at least a dozen times over
|
||
a period of at least several minutes before giving up on an SA, but
|
||
different environments may require different rules. To be a good
|
||
network citizen, retranmission times MUST increase exponentially to
|
||
avoid flooding the network and making an existing congestion
|
||
situation worse. If there has only been outgoing traffic on all of
|
||
the SAs associated with an IKE_SA, it is essential to confirm
|
||
liveness of the other endpoint to avoid black holes. If no
|
||
cryptographically protected messages have been received on an IKE_SA
|
||
or any of its CHILD_SAs recently, the system needs to perform a
|
||
liveness check in order to prevent sending messages to a dead peer.
|
||
Receipt of a fresh cryptographically protected message on an IKE_SA
|
||
or any of its CHILD_SAs ensures liveness of the IKE_SA and all of its
|
||
CHILD_SAs. Note that this places requirements on the failure modes
|
||
of an IKE endpoint. An implementation MUST NOT continue sending on
|
||
any SA if some failure prevents it from receiving on all of the
|
||
associated SAs. If CHILD_SAs can fail independently from one another
|
||
without the associated IKE_SA being able to send a delete message,
|
||
then they MUST be negotiated by separate IKE_SAs.
|
||
|
||
There is a Denial of Service attack on the initiator of an IKE_SA
|
||
that can be avoided if the initiator takes the proper care. Since
|
||
the first two messages of an SA setup are not cryptographically
|
||
protected, an attacker could respond to the initiator's message
|
||
before the genuine responder and poison the connection setup attempt.
|
||
To prevent this, the initiator MAY be willing to accept multiple
|
||
responses to its first message, treat each as potentially legitimate,
|
||
respond to it, and then discard all the invalid half-open connections
|
||
when it receives a valid cryptographically protected response to any
|
||
one of its requests. Once a cryptographically valid response is
|
||
received, all subsequent responses should be ignored whether or not
|
||
they are cryptographically valid.
|
||
|
||
Note that with these rules, there is no reason to negotiate and agree
|
||
upon an SA lifetime. If IKE presumes the partner is dead, based on
|
||
repeated lack of acknowledgement to an IKE message, then the IKE SA
|
||
and all CHILD_SAs set up through that IKE_SA are deleted.
|
||
|
||
An IKE endpoint may at any time delete inactive CHILD_SAs to recover
|
||
resources used to hold their state. If an IKE endpoint chooses to
|
||
delete CHILD_SAs, it MUST send Delete payloads to the other end
|
||
notifying it of the deletion. It MAY similarly time out the IKE_SA.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 24]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
{{ Clarified the SHOULD }} Closing the IKE_SA implicitly closes all
|
||
associated CHILD_SAs. In this case, an IKE endpoint SHOULD send a
|
||
Delete payload indicating that it has closed the IKE_SA unless the
|
||
other endpoint is no longer responding.
|
||
|
||
2.5. Version Numbers and Forward Compatibility
|
||
|
||
This document describes version 2.0 of IKE, meaning the major version
|
||
number is 2 and the minor version number is 0. {{ Restated the
|
||
relationship to RFC 4306 }} This document is a clarification of
|
||
[IKEV2]. It is likely that some implementations will want to support
|
||
version 1.0 and version 2.0, and in the future, other versions.
|
||
|
||
The major version number should be incremented only if the packet
|
||
formats or required actions have changed so dramatically that an
|
||
older version node would not be able to interoperate with a newer
|
||
version node if it simply ignored the fields it did not understand
|
||
and took the actions specified in the older specification. The minor
|
||
version number indicates new capabilities, and MUST be ignored by a
|
||
node with a smaller minor version number, but used for informational
|
||
purposes by the node with the larger minor version number. For
|
||
example, it might indicate the ability to process a newly defined
|
||
notification message. The node with the larger minor version number
|
||
would simply note that its correspondent would not be able to
|
||
understand that message and therefore would not send it.
|
||
|
||
{{ 3.10.1-5 }} If an endpoint receives a message with a higher major
|
||
version number, it MUST drop the message and SHOULD send an
|
||
unauthenticated notification message of type INVALID_MAJOR_VERSION
|
||
containing the highest (closest) version number it supports. If an
|
||
endpoint supports major version n, and major version m, it MUST
|
||
support all versions between n and m. If it receives a message with
|
||
a major version that it supports, it MUST respond with that version
|
||
number. In order to prevent two nodes from being tricked into
|
||
corresponding with a lower major version number than the maximum that
|
||
they both support, IKE has a flag that indicates that the node is
|
||
capable of speaking a higher major version number.
|
||
|
||
Thus, the major version number in the IKE header indicates the
|
||
version number of the message, not the highest version number that
|
||
the transmitter supports. If the initiator is capable of speaking
|
||
versions n, n+1, and n+2, and the responder is capable of speaking
|
||
versions n and n+1, then they will negotiate speaking n+1, where the
|
||
initiator will set a flag indicating its ability to speak a higher
|
||
version. If they mistakenly (perhaps through an active attacker
|
||
sending error messages) negotiate to version n, then both will notice
|
||
that the other side can support a higher version number, and they
|
||
MUST break the connection and reconnect using version n+1.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 25]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Note that IKEv1 does not follow these rules, because there is no way
|
||
in v1 of noting that you are capable of speaking a higher version
|
||
number. So an active attacker can trick two v2-capable nodes into
|
||
speaking v1. {{ Demoted the SHOULD }} When a v2-capable node
|
||
negotiates down to v1, it should note that fact in its logs.
|
||
|
||
Also for forward compatibility, all fields marked RESERVED MUST be
|
||
set to zero by an implementation running version 2.0, and their
|
||
content MUST be ignored by an implementation running version 2.0 ("Be
|
||
conservative in what you send and liberal in what you receive"). In
|
||
this way, future versions of the protocol can use those fields in a
|
||
way that is guaranteed to be ignored by implementations that do not
|
||
understand them. Similarly, payload types that are not defined are
|
||
reserved for future use; implementations of a version where they are
|
||
undefined MUST skip over those payloads and ignore their contents.
|
||
|
||
IKEv2 adds a "critical" flag to each payload header for further
|
||
flexibility for forward compatibility. If the critical flag is set
|
||
and the payload type is unrecognized, the message MUST be rejected
|
||
and the response to the IKE request containing that payload MUST
|
||
include a Notify payload UNSUPPORTED_CRITICAL_PAYLOAD, indicating an
|
||
unsupported critical payload was included. {{ 3.10.1-1 }} In that
|
||
Notify payload, the notification data contains the one-octet payload
|
||
type. If the critical flag is not set and the payload type is
|
||
unsupported, that payload MUST be ignored. Payloads sent in IKE
|
||
response messages MUST NOT have the critical flag set. Note that the
|
||
critical flag applies only to the payload type, not the contents. If
|
||
the payload type is recognized, but the payload contains something
|
||
which is not (such as an unknown transform inside an SA payload, or
|
||
an unknown Notify Message Type inside a Notify payload), the critical
|
||
flag is ignored.
|
||
|
||
NOTE TO IMPLEMENTERS: Does anyone require that the payloads be in the
|
||
order shown in the figures in Section 2? Can we eliminate the
|
||
requirement in the following paragraph? If not, we will probably
|
||
have to add a new appendix with the order, but there is no reason to
|
||
do that if no one actually cares. {{ Remove this paragraph before the
|
||
document is finalized, of course. }}
|
||
|
||
{{ Demoted the SHOULD in the second clause }}Although new payload
|
||
types may be added in the future and may appear interleaved with the
|
||
fields defined in this specification, implementations MUST send the
|
||
payloads defined in this specification in the order shown in the
|
||
figures in Section 2; implementations are explicitly allowed to
|
||
reject as invalid a message with those payloads in any other order.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 26]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
2.6. Cookies
|
||
|
||
The term "cookies" originates with Karn and Simpson [PHOTURIS] in
|
||
Photuris, an early proposal for key management with IPsec, and it has
|
||
persisted. The Internet Security Association and Key Management
|
||
Protocol (ISAKMP) [ISAKMP] fixed message header includes two eight-
|
||
octet fields titled "cookies", and that syntax is used by both IKEv1
|
||
and IKEv2, although in IKEv2 they are referred to as the "IKE SPI"
|
||
and there is a new separate field in a Notify payload holding the
|
||
cookie. The initial two eight-octet fields in the header are used as
|
||
a connection identifier at the beginning of IKE packets. {{ Demoted
|
||
the SHOULD }} Each endpoint chooses one of the two SPIs and needs to
|
||
choose them so as to be unique identifiers of an IKE_SA. An SPI
|
||
value of zero is special and indicates that the remote SPI value is
|
||
not yet known by the sender.
|
||
|
||
Unlike ESP and AH where only the recipient's SPI appears in the
|
||
header of a message, in IKE the sender's SPI is also sent in every
|
||
message. Since the SPI chosen by the original initiator of the
|
||
IKE_SA is always sent first, an endpoint with multiple IKE_SAs open
|
||
that wants to find the appropriate IKE_SA using the SPI it assigned
|
||
must look at the I(nitiator) Flag bit in the header to determine
|
||
whether it assigned the first or the second eight octets.
|
||
|
||
In the first message of an initial IKE exchange, the initiator will
|
||
not know the responder's SPI value and will therefore set that field
|
||
to zero.
|
||
|
||
An expected attack against IKE is state and CPU exhaustion, where the
|
||
target is flooded with session initiation requests from forged IP
|
||
addresses. This attack can be made less effective if an
|
||
implementation of a responder uses minimal CPU and commits no state
|
||
to an SA until it knows the initiator can receive packets at the
|
||
address from which it claims to be sending them.
|
||
|
||
When a responder detects a large number of half-open IKE_SAs, it
|
||
SHOULD reply to IKE_SA_INIT requests with a response containing the
|
||
COOKIE notification. {{ 3.10.1-16390 }} The data associated with this
|
||
notification MUST be between 1 and 64 octets in length (inclusive),
|
||
and its generation is described later in this section. If the
|
||
IKE_SA_INIT response includes the COOKIE notification, the initiator
|
||
MUST then retry the IKE_SA_INIT request, and include the COOKIE
|
||
notification containing the received data as the first payload, and
|
||
all other payloads unchanged. The initial exchange will then be as
|
||
follows:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 27]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR(A,0), SAi1, KEi, Ni -->
|
||
<-- HDR(A,0), N(COOKIE)
|
||
HDR(A,0), N(COOKIE), SAi1,
|
||
KEi, Ni -->
|
||
<-- HDR(A,B), SAr1, KEr,
|
||
Nr, [CERTREQ]
|
||
HDR(A,B), SK {IDi, [CERT,]
|
||
[CERTREQ,] [IDr,] AUTH,
|
||
SAi2, TSi, TSr} -->
|
||
<-- HDR(A,B), SK {IDr, [CERT,]
|
||
AUTH, SAr2, TSi, TSr}
|
||
|
||
The first two messages do not affect any initiator or responder state
|
||
except for communicating the cookie. In particular, the message
|
||
sequence numbers in the first four messages will all be zero and the
|
||
message sequence numbers in the last two messages will be one. 'A'
|
||
is the SPI assigned by the initiator, while 'B' is the SPI assigned
|
||
by the responder.
|
||
|
||
{{ Demoted the SHOULD }} An IKE implementation should implement its
|
||
responder cookie generation in such a way as to not require any saved
|
||
state to recognize its valid cookie when the second IKE_SA_INIT
|
||
message arrives. The exact algorithms and syntax they use to
|
||
generate cookies do not affect interoperability and hence are not
|
||
specified here. The following is an example of how an endpoint could
|
||
use cookies to implement limited DOS protection.
|
||
|
||
A good way to do this is to set the responder cookie to be:
|
||
|
||
Cookie = <VersionIDofSecret> | Hash(Ni | IPi | SPIi | <secret>)
|
||
|
||
where <secret> is a randomly generated secret known only to the
|
||
responder and periodically changed and | indicates concatenation.
|
||
<VersionIDofSecret> should be changed whenever <secret> is
|
||
regenerated. The cookie can be recomputed when the IKE_SA_INIT
|
||
arrives the second time and compared to the cookie in the received
|
||
message. If it matches, the responder knows that the cookie was
|
||
generated since the last change to <secret> and that IPi must be the
|
||
same as the source address it saw the first time. Incorporating SPIi
|
||
into the calculation ensures that if multiple IKE_SAs are being set
|
||
up in parallel they will all get different cookies (assuming the
|
||
initiator chooses unique SPIi's). Incorporating Ni into the hash
|
||
ensures that an attacker who sees only message 2 can't successfully
|
||
forge a message 3.
|
||
|
||
If a new value for <secret> is chosen while there are connections in
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 28]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
the process of being initialized, an IKE_SA_INIT might be returned
|
||
with other than the current <VersionIDofSecret>. The responder in
|
||
that case MAY reject the message by sending another response with a
|
||
new cookie or it MAY keep the old value of <secret> around for a
|
||
short time and accept cookies computed from either one. {{ Demoted
|
||
the SHOULD NOT }} The responder should not accept cookies
|
||
indefinitely after <secret> is changed, since that would defeat part
|
||
of the denial of service protection. {{ Demoted the SHOULD }} The
|
||
responder should change the value of <secret> frequently, especially
|
||
if under attack.
|
||
|
||
{{ Clarif-2.1 }} In addition to cookies, there are several cases
|
||
where the IKE_SA_INIT exchange does not result in the creation of an
|
||
IKE_SA (such as INVALID_KE_PAYLOAD or NO_PROPOSAL_CHOSEN). In such a
|
||
case, sending a zero value for the Responder's SPI is correct. If
|
||
the responder sends a non-zero responder SPI, the initiator should
|
||
not reject the response for only that reason.
|
||
|
||
{{ Clarif-2.5 }} When one party receives an IKE_SA_INIT request
|
||
containing a cookie whose contents do not match the value expected,
|
||
that party MUST ignore the cookie and process the message as if no
|
||
cookie had been included; usually this means sending a response
|
||
containing a new cookie.
|
||
|
||
2.6.1. Interaction of COOKIE and INVALID_KE_PAYLOAD
|
||
|
||
{{ This section added by Clarif-2.4 }}
|
||
|
||
There are two common reasons why the initiator may have to retry the
|
||
IKE_SA_INIT exchange: the responder requests a cookie or wants a
|
||
different Diffie-Hellman group than was included in the KEi payload.
|
||
If the initiator receives a cookie from the responder, the initiator
|
||
needs to decide whether or not to include the cookie in only the next
|
||
retry of the IKE_SA_INIT request, or in all subsequent retries as
|
||
well.
|
||
|
||
If the initiator includes the cookie only in the next retry, one
|
||
additional roundtrip may be needed in some cases. An additional
|
||
roundtrip is needed also if the initiator includes the cookie in all
|
||
retries, but the responder does not support this. For instance, if
|
||
the responder includes the SAi1 and KEi payloads in cookie
|
||
calculation, it will reject the request by sending a new cookie.
|
||
|
||
If both peers support including the cookie in all retries, a slightly
|
||
shorter exchange can happen. Implementations SHOULD support this
|
||
shorter exchange, but MUST NOT fail if other implementations do not
|
||
support this shorter exchange.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 29]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
2.7. Cryptographic Algorithm Negotiation
|
||
|
||
The payload type known as "SA" indicates a proposal for a set of
|
||
choices of IPsec protocols (IKE, ESP, and/or AH) for the SA as well
|
||
as cryptographic algorithms associated with each protocol.
|
||
|
||
An SA payload consists of one or more proposals. {{ Clarif-7.13 }}
|
||
Each proposal includes one protocol. Each protocol contains one or
|
||
more transforms -- each specifying a cryptographic algorithm. Each
|
||
transform contains zero or more attributes (attributes are needed
|
||
only if the transform identifier does not completely specify the
|
||
cryptographic algorithm).
|
||
|
||
This hierarchical structure was designed to efficiently encode
|
||
proposals for cryptographic suites when the number of supported
|
||
suites is large because multiple values are acceptable for multiple
|
||
transforms. The responder MUST choose a single suite, which may be
|
||
any subset of the SA proposal following the rules below:
|
||
|
||
{{ Clarif-7.13 }} Each proposal contains one protocol. If a proposal
|
||
is accepted, the SA response MUST contain the same protocol. The
|
||
responder MUST accept a single proposal or reject them all and return
|
||
an error. {{ 3.10.1-14 }} The error is given in a notification of
|
||
type NO_PROPOSAL_CHOSEN.
|
||
|
||
Each IPsec protocol proposal contains one or more transforms. Each
|
||
transform contains a transform type. The accepted cryptographic
|
||
suite MUST contain exactly one transform of each type included in the
|
||
proposal. For example: if an ESP proposal includes transforms
|
||
ENCR_3DES, ENCR_AES w/keysize 128, ENCR_AES w/keysize 256,
|
||
AUTH_HMAC_MD5, and AUTH_HMAC_SHA, the accepted suite MUST contain one
|
||
of the ENCR_ transforms and one of the AUTH_ transforms. Thus, six
|
||
combinations are acceptable.
|
||
|
||
Since the initiator sends its Diffie-Hellman value in the
|
||
IKE_SA_INIT, it must guess the Diffie-Hellman group that the
|
||
responder will select from its list of supported groups. If the
|
||
initiator guesses wrong, the responder will respond with a Notify
|
||
payload of type INVALID_KE_PAYLOAD indicating the selected group. In
|
||
this case, the initiator MUST retry the IKE_SA_INIT with the
|
||
corrected Diffie-Hellman group. The initiator MUST again propose its
|
||
full set of acceptable cryptographic suites because the rejection
|
||
message was unauthenticated and otherwise an active attacker could
|
||
trick the endpoints into negotiating a weaker suite than a stronger
|
||
one that they both prefer.
|
||
|
||
{{ Clarif-2.1 }} When the IKE_SA_INIT exchange does not result in the
|
||
creation of an IKE_SA due to INVALID_KE_PAYLOAD, NO_PROPOSAL_CHOSEN,
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 30]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
or COOKIE (see Section 2.6), the responder's SPI will be zero.
|
||
However, if the responder sends a non-zero responder SPI, the
|
||
initiator should not reject the response for only that reason.
|
||
|
||
2.8. Rekeying
|
||
|
||
{{ Demoted the SHOULD }} IKE, ESP, and AH security associations use
|
||
secret keys that should be used only for a limited amount of time and
|
||
to protect a limited amount of data. This limits the lifetime of the
|
||
entire security association. When the lifetime of a security
|
||
association expires, the security association MUST NOT be used. If
|
||
there is demand, new security associations MAY be established.
|
||
Reestablishment of security associations to take the place of ones
|
||
that expire is referred to as "rekeying".
|
||
|
||
To allow for minimal IPsec implementations, the ability to rekey SAs
|
||
without restarting the entire IKE_SA is optional. An implementation
|
||
MAY refuse all CREATE_CHILD_SA requests within an IKE_SA. If an SA
|
||
has expired or is about to expire and rekeying attempts using the
|
||
mechanisms described here fail, an implementation MUST close the
|
||
IKE_SA and any associated CHILD_SAs and then MAY start new ones. {{
|
||
Demoted the SHOULD }} Implementations may wish to support in-place
|
||
rekeying of SAs, since doing so offers better performance and is
|
||
likely to reduce the number of packets lost during the transition.
|
||
|
||
To rekey a CHILD_SA within an existing IKE_SA, create a new,
|
||
equivalent SA (see Section 2.17 below), and when the new one is
|
||
established, delete the old one. To rekey an IKE_SA, establish a new
|
||
equivalent IKE_SA (see Section 2.18 below) with the peer to whom the
|
||
old IKE_SA is shared using a CREATE_CHILD_SA within the existing
|
||
IKE_SA. An IKE_SA so created inherits all of the original IKE_SA's
|
||
CHILD_SAs, and the new IKE_SA is used for all control messages needed
|
||
to maintain those CHILD_SAs. The old IKE_SA is then deleted, and the
|
||
Delete payload to delete itself MUST be the last request sent over
|
||
the old IKE_SA.
|
||
|
||
{{ Demoted the SHOULD }} SAs should be rekeyed proactively, i.e., the
|
||
new SA should be established before the old one expires and becomes
|
||
unusable. Enough time should elapse between the time the new SA is
|
||
established and the old one becomes unusable so that traffic can be
|
||
switched over to the new SA.
|
||
|
||
A difference between IKEv1 and IKEv2 is that in IKEv1 SA lifetimes
|
||
were negotiated. In IKEv2, each end of the SA is responsible for
|
||
enforcing its own lifetime policy on the SA and rekeying the SA when
|
||
necessary. If the two ends have different lifetime policies, the end
|
||
with the shorter lifetime will end up always being the one to request
|
||
the rekeying. If an SA has been inactive for a long time and if an
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 31]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
endpoint would not initiate the SA in the absence of traffic, the
|
||
endpoint MAY choose to close the SA instead of rekeying it when its
|
||
lifetime expires. {{ Demoted the SHOULD }} It should do so if there
|
||
has been no traffic since the last time the SA was rekeyed.
|
||
|
||
Note that IKEv2 deliberately allows parallel SAs with the same
|
||
traffic selectors between common endpoints. One of the purposes of
|
||
this is to support traffic quality of service (QoS) differences among
|
||
the SAs (see [DIFFSERVFIELD], [DIFFSERVARCH], and section 4.1 of
|
||
[DIFFTUNNEL]). Hence unlike IKEv1, the combination of the endpoints
|
||
and the traffic selectors may not uniquely identify an SA between
|
||
those endpoints, so the IKEv1 rekeying heuristic of deleting SAs on
|
||
the basis of duplicate traffic selectors SHOULD NOT be used.
|
||
|
||
{{ Demoted the SHOULD }} The node that initiated the surviving
|
||
rekeyed SA should delete the replaced SA after the new one is
|
||
established.
|
||
|
||
There are timing windows -- particularly in the presence of lost
|
||
packets -- where endpoints may not agree on the state of an SA. The
|
||
responder to a CREATE_CHILD_SA MUST be prepared to accept messages on
|
||
an SA before sending its response to the creation request, so there
|
||
is no ambiguity for the initiator. The initiator MAY begin sending
|
||
on an SA as soon as it processes the response. The initiator,
|
||
however, cannot receive on a newly created SA until it receives and
|
||
processes the response to its CREATE_CHILD_SA request. How, then, is
|
||
the responder to know when it is OK to send on the newly created SA?
|
||
|
||
From a technical correctness and interoperability perspective, the
|
||
responder MAY begin sending on an SA as soon as it sends its response
|
||
to the CREATE_CHILD_SA request. In some situations, however, this
|
||
could result in packets unnecessarily being dropped, so an
|
||
implementation MAY defer such sending.
|
||
|
||
The responder can be assured that the initiator is prepared to
|
||
receive messages on an SA if either (1) it has received a
|
||
cryptographically valid message on the new SA, or (2) the new SA
|
||
rekeys an existing SA and it receives an IKE request to close the
|
||
replaced SA. When rekeying an SA, the responder continues to send
|
||
traffic on the old SA until one of those events occurs. When
|
||
establishing a new SA, the responder MAY defer sending messages on a
|
||
new SA until either it receives one or a timeout has occurred. {{
|
||
Demoted the SHOULD }} If an initiator receives a message on an SA for
|
||
which it has not received a response to its CREATE_CHILD_SA request,
|
||
it interprets that as a likely packet loss and retransmits the
|
||
CREATE_CHILD_SA request. An initiator MAY send a dummy message on a
|
||
newly created SA if it has no messages queued in order to assure the
|
||
responder that the initiator is ready to receive messages.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 32]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
{{ Clarif-5.9 }} Throughout this document, "initiator" refers to the
|
||
party who initiated the exchange being described, and "original
|
||
initiator" refers to the party who initiated the whole IKE_SA. The
|
||
"original initiator" always refers to the party who initiated the
|
||
exchange which resulted in the current IKE_SA. In other words, if
|
||
the "original responder" starts rekeying the IKE_SA, that party
|
||
becomes the "original initiator" of the new IKE_SA.
|
||
|
||
2.8.1. Simultaneous CHILD_SA rekeying
|
||
|
||
{{ The first two paragraphs were moved, and the rest was added, based
|
||
on Clarif-5.11 }}
|
||
|
||
If the two ends have the same lifetime policies, it is possible that
|
||
both will initiate a rekeying at the same time (which will result in
|
||
redundant SAs). To reduce the probability of this happening, the
|
||
timing of rekeying requests SHOULD be jittered (delayed by a random
|
||
amount of time after the need for rekeying is noticed).
|
||
|
||
This form of rekeying may temporarily result in multiple similar SAs
|
||
between the same pairs of nodes. When there are two SAs eligible to
|
||
receive packets, a node MUST accept incoming packets through either
|
||
SA. If redundant SAs are created though such a collision, the SA
|
||
created with the lowest of the four nonces used in the two exchanges
|
||
SHOULD be closed by the endpoint that created it. {{ Clarif-5.10 }}
|
||
"Lowest" means an octet-by-octet, lexicographical comparison (instead
|
||
of, for instance, comparing the nonces as large integers). In other
|
||
words, start by comparing the first octet; if they're equal, move to
|
||
the next octet, and so on. If you reach the end of one nonce, that
|
||
nonce is the lower one.
|
||
|
||
The following is an explanation on the impact this has on
|
||
implementations. Assume that hosts A and B have an existing IPsec SA
|
||
pair with SPIs (SPIa1,SPIb1), and both start rekeying it at the same
|
||
time:
|
||
|
||
Host A Host B
|
||
-------------------------------------------------------------------
|
||
send req1: N(REKEY_SA,SPIa1),
|
||
SA(..,SPIa2,..),Ni1,.. -->
|
||
<-- send req2: N(REKEY_SA,SPIb1),
|
||
SA(..,SPIb2,..),Ni2
|
||
recv req2 <--
|
||
|
||
At this point, A knows there is a simultaneous rekeying going on.
|
||
However, it cannot yet know which of the exchanges will have the
|
||
lowest nonce, so it will just note the situation and respond as
|
||
usual.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 33]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
send resp2: SA(..,SPIa3,..),
|
||
Nr1,.. -->
|
||
--> recv req1
|
||
|
||
Now B also knows that simultaneous rekeying is going on. It responds
|
||
as usual.
|
||
|
||
<-- send resp1: SA(..,SPIb3,..),
|
||
Nr2,..
|
||
recv resp1 <--
|
||
--> recv resp2
|
||
|
||
At this point, there are three CHILD_SA pairs between A and B (the
|
||
old one and two new ones). A and B can now compare the nonces.
|
||
Suppose that the lowest nonce was Nr1 in message resp2; in this case,
|
||
B (the sender of req2) deletes the redundant new SA, and A (the node
|
||
that initiated the surviving rekeyed SA), deletes the old one.
|
||
|
||
send req3: D(SPIa1) -->
|
||
<-- send req4: D(SPIb2)
|
||
--> recv req3
|
||
<-- send resp3: D(SPIb1)
|
||
recv req4 <--
|
||
send resp4: D(SPIa3) -->
|
||
|
||
The rekeying is now finished.
|
||
|
||
However, there is a second possible sequence of events that can
|
||
happen if some packets are lost in the network, resulting in
|
||
retransmissions. The rekeying begins as usual, but A's first packet
|
||
(req1) is lost.
|
||
|
||
Host A Host B
|
||
-------------------------------------------------------------------
|
||
send req1: N(REKEY_SA,SPIa1),
|
||
SA(..,SPIa2,..),
|
||
Ni1,.. --> (lost)
|
||
<-- send req2: N(REKEY_SA,SPIb1),
|
||
SA(..,SPIb2,..),Ni2
|
||
recv req2 <--
|
||
send resp2: SA(..,SPIa3,..),
|
||
Nr1,.. -->
|
||
--> recv resp2
|
||
<-- send req3: D(SPIb1)
|
||
recv req3 <--
|
||
send resp3: D(SPIa1) -->
|
||
--> recv resp3
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 34]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
From B's point of view, the rekeying is now completed, and since it
|
||
has not yet received A's req1, it does not even know that there was
|
||
simultaneous rekeying. However, A will continue retransmitting the
|
||
message, and eventually it will reach B.
|
||
|
||
resend req1 -->
|
||
--> recv req1
|
||
|
||
To B, it looks like A is trying to rekey an SA that no longer exists;
|
||
thus, B responds to the request with something non-fatal such as
|
||
NO_PROPOSAL_CHOSEN.
|
||
|
||
<-- send resp1: N(NO_PROPOSAL_CHOSEN)
|
||
recv resp1 <--
|
||
|
||
When A receives this error, it already knows there was simultaneous
|
||
rekeying, so it can ignore the error message.
|
||
|
||
2.8.2. Rekeying the IKE_SA Versus Reauthentication
|
||
|
||
{{ Added this section from Clarif-5.2 }}
|
||
|
||
Rekeying the IKE_SA and reauthentication are different concepts in
|
||
IKEv2. Rekeying the IKE_SA establishes new keys for the IKE_SA and
|
||
resets the Message ID counters, but it does not authenticate the
|
||
parties again (no AUTH or EAP payloads are involved).
|
||
|
||
Although rekeying the IKE_SA may be important in some environments,
|
||
reauthentication (the verification that the parties still have access
|
||
to the long-term credentials) is often more important.
|
||
|
||
IKEv2 does not have any special support for reauthentication.
|
||
Reauthentication is done by creating a new IKE_SA from scratch (using
|
||
IKE_SA_INIT/IKE_AUTH exchanges, without any REKEY_SA notify
|
||
payloads), creating new CHILD_SAs within the new IKE_SA (without
|
||
REKEY_SA notify payloads), and finally deleting the old IKE_SA (which
|
||
deletes the old CHILD_SAs as well).
|
||
|
||
This means that reauthentication also establishes new keys for the
|
||
IKE_SA and CHILD_SAs. Therefore, while rekeying can be performed
|
||
more often than reauthentication, the situation where "authentication
|
||
lifetime" is shorter than "key lifetime" does not make sense.
|
||
|
||
While creation of a new IKE_SA can be initiated by either party
|
||
(initiator or responder in the original IKE_SA), the use of EAP
|
||
authentication and/or configuration payloads means in practice that
|
||
reauthentication has to be initiated by the same party as the
|
||
original IKE_SA. IKEv2 does not currently allow the responder to
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 35]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
request reauthentication in this case; however, there are extensions
|
||
that add this functionality such as [REAUTH].
|
||
|
||
2.9. Traffic Selector Negotiation
|
||
|
||
{{ Clarif-7.2 }} When an RFC4301-compliant IPsec subsystem receives
|
||
an IP packet and matches a "protect" selector in its Security Policy
|
||
Database (SPD), the subsystem protects that packet with IPsec. When
|
||
no SA exists yet, it is the task of IKE to create it. Maintenance of
|
||
a system's SPD is outside the scope of IKE (see [PFKEY] for an
|
||
example protocol), though some implementations might update their SPD
|
||
in connection with the running of IKE (for an example scenario, see
|
||
Section 1.1.3).
|
||
|
||
Traffic Selector (TS) payloads allow endpoints to communicate some of
|
||
the information from their SPD to their peers. TS payloads specify
|
||
the selection criteria for packets that will be forwarded over the
|
||
newly set up SA. This can serve as a consistency check in some
|
||
scenarios to assure that the SPDs are consistent. In others, it
|
||
guides the dynamic update of the SPD.
|
||
|
||
Two TS payloads appear in each of the messages in the exchange that
|
||
creates a CHILD_SA pair. Each TS payload contains one or more
|
||
Traffic Selectors. Each Traffic Selector consists of an address
|
||
range (IPv4 or IPv6), a port range, and an IP protocol ID.
|
||
|
||
The first of the two TS payloads is known as TSi (Traffic Selector-
|
||
initiator). The second is known as TSr (Traffic Selector-responder).
|
||
TSi specifies the source address of traffic forwarded from (or the
|
||
destination address of traffic forwarded to) the initiator of the
|
||
CHILD_SA pair. TSr specifies the destination address of the traffic
|
||
forwarded to (or the source address of the traffic forwarded from)
|
||
the responder of the CHILD_SA pair. For example, if the original
|
||
initiator requests the creation of a CHILD_SA pair, and wishes to
|
||
tunnel all traffic from subnet 192.0.1.* on the initiator's side to
|
||
subnet 192.0.2.* on the responder's side, the initiator would include
|
||
a single traffic selector in each TS payload. TSi would specify the
|
||
address range (192.0.1.0 - 192.0.1.255) and TSr would specify the
|
||
address range (192.0.2.0 - 192.0.2.255). Assuming that proposal was
|
||
acceptable to the responder, it would send identical TS payloads
|
||
back. (Note: The IP address range 192.0.2.* has been reserved for
|
||
use in examples in RFCs and similar documents. This document needed
|
||
two such ranges, and so also used 192.0.1.*. This should not be
|
||
confused with any actual address.)
|
||
|
||
IKEv2 allows the responder to choose a subset of the traffic proposed
|
||
by the initiator. This could happen when the configurations of the
|
||
two endpoints are being updated but only one end has received the new
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 36]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
information. Since the two endpoints may be configured by different
|
||
people, the incompatibility may persist for an extended period even
|
||
in the absence of errors. It also allows for intentionally different
|
||
configurations, as when one end is configured to tunnel all addresses
|
||
and depends on the other end to have the up-to-date list.
|
||
|
||
When the responder chooses a subset of the traffic proposed by the
|
||
initiator, it narrows the traffic selectors to some subset of the
|
||
initiator's proposal (provided the set does not become the null set).
|
||
|
||
To enable the responder to choose the appropriate range in this case,
|
||
if the initiator has requested the SA due to a data packet, the
|
||
initiator SHOULD include as the first traffic selector in each of TSi
|
||
and TSr a very specific traffic selector including the addresses in
|
||
the packet triggering the request. In the example, the initiator
|
||
would include in TSi two traffic selectors: the first containing the
|
||
address range (192.0.1.43 - 192.0.1.43) and the source port and IP
|
||
protocol from the packet and the second containing (192.0.1.0 -
|
||
192.0.1.255) with all ports and IP protocols. The initiator would
|
||
similarly include two traffic selectors in TSr. If the initiator
|
||
creates the CHILD_SA pair not in response to an arriving packet, but
|
||
rather, say, upon startup, then there may be no specific addresses
|
||
the initiator prefers for the initial tunnel over any other. In that
|
||
case, the first values in TSi and TSr can be ranges rather than
|
||
specific values.
|
||
|
||
The responder performs the narrowing as follows: {{ Clarif-4.10 }}
|
||
|
||
o If the responder's policy does not allow it to accept any part of
|
||
the proposed traffic selectors, it responds with TS_UNACCEPTABLE.
|
||
|
||
o If the responder's policy allows the entire set of traffic covered
|
||
by TSi and TSr, no narrowing is necessary, and the responder can
|
||
return the same TSi and TSr values.
|
||
|
||
o If the responder's policy allows it to accept the first selector
|
||
of TSi and TSr, then the responder MUST narrow the traffic
|
||
selectors to a subset that includes the initiator's first choices.
|
||
In this example above, the responder might respond with TSi being
|
||
(192.0.1.43 - 192.0.1.43) with all ports and IP protocols.
|
||
|
||
o If the responder's policy does not allow it to accept the first
|
||
selector of TSi and TSr, the responder narrows to an acceptable
|
||
subset of TSi and TSr.
|
||
|
||
When narrowing is done, there may be several subsets that are
|
||
acceptable but their union is not. In this case, the responder
|
||
arbitrarily chooses one of them, and MAY include an
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 37]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
ADDITIONAL_TS_POSSIBLE notification in the response. {{ 3.10.1-16386
|
||
}} The ADDITIONAL_TS_POSSIBLE notification asserts that the responder
|
||
narrowed the proposed traffic selectors but that other traffic
|
||
selectors would also have been acceptable, though only in a separate
|
||
SA. There is no data associated with this Notify type. This case
|
||
will occur only when the initiator and responder are configured
|
||
differently from one another. If the initiator and responder agree
|
||
on the granularity of tunnels, the initiator will never request a
|
||
tunnel wider than the responder will accept. {{ Demoted the SHOULD }}
|
||
Such misconfigurations should be recorded in error logs.
|
||
|
||
It is possible for the responder's policy to contain multiple smaller
|
||
ranges, all encompassed by the initiator's traffic selector, and with
|
||
the responder's policy being that each of those ranges should be sent
|
||
over a different SA. Continuing the example above, the responder
|
||
might have a policy of being willing to tunnel those addresses to and
|
||
from the initiator, but might require that each address pair be on a
|
||
separately negotiated CHILD_SA. If the initiator generated its
|
||
request in response to an incoming packet from 192.0.1.43 to
|
||
192.0.2.123, there would be no way for the responder to determine
|
||
which pair of addresses should be included in this tunnel, and it
|
||
would have to make a guess or reject the request with a status of
|
||
SINGLE_PAIR_REQUIRED.
|
||
|
||
{{ 3.10.1-34 }} The SINGLE_PAIR_REQUIRED error indicates that a
|
||
CREATE_CHILD_SA request is unacceptable because its sender is only
|
||
willing to accept traffic selectors specifying a single pair of
|
||
addresses. The requestor is expected to respond by requesting an SA
|
||
for only the specific traffic it is trying to forward.
|
||
|
||
{{ Clarif-4.11 }} Few implementations will have policies that require
|
||
separate SAs for each address pair. Because of this, if only some
|
||
parts of the TSi and TSr proposed by the initiator are acceptable to
|
||
the responder, responders SHOULD narrow the selectors to an
|
||
acceptable subset rather than use SINGLE_PAIR_REQUIRED.
|
||
|
||
2.9.1. Traffic Selectors Violating Own Policy
|
||
|
||
{{ Clarif-4.12 }}
|
||
|
||
When creating a new SA, the initiator needs to avoid proposing
|
||
traffic selectors that violate its own policy. If this rule is not
|
||
followed, valid traffic may be dropped.
|
||
|
||
This is best illustrated by an example. Suppose that host A has a
|
||
policy whose effect is that traffic to 192.0.1.66 is sent via host B
|
||
encrypted using AES, and traffic to all other hosts in 192.0.1.0/24
|
||
is also sent via B, but must use 3DES. Suppose also that host B
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 38]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
accepts any combination of AES and 3DES.
|
||
|
||
If host A now proposes an SA that uses 3DES, and includes TSr
|
||
containing (192.0.1.0-192.0.1.255), this will be accepted by host B.
|
||
Now, host B can also use this SA to send traffic from 192.0.1.66, but
|
||
those packets will be dropped by A since it requires the use of AES
|
||
for those traffic. Even if host A creates a new SA only for
|
||
192.0.1.66 that uses AES, host B may freely continue to use the first
|
||
SA for the traffic. In this situation, when proposing the SA, host A
|
||
should have followed its own policy, and included a TSr containing
|
||
((192.0.1.0-192.0.1.65),(192.0.1.67-192.0.1.255)) instead.
|
||
|
||
In general, if (1) the initiator makes a proposal "for traffic X
|
||
(TSi/TSr), do SA", and (2) for some subset X' of X, the initiator
|
||
does not actually accept traffic X' with SA, and (3) the initiator
|
||
would be willing to accept traffic X' with some SA' (!=SA), valid
|
||
traffic can be unnecessarily dropped since the responder can apply
|
||
either SA or SA' to traffic X'.
|
||
|
||
2.10. Nonces
|
||
|
||
The IKE_SA_INIT messages each contain a nonce. These nonces are used
|
||
as inputs to cryptographic functions. The CREATE_CHILD_SA request
|
||
and the CREATE_CHILD_SA response also contain nonces. These nonces
|
||
are used to add freshness to the key derivation technique used to
|
||
obtain keys for CHILD_SA, and to ensure creation of strong pseudo-
|
||
random bits from the Diffie-Hellman key. Nonces used in IKEv2 MUST
|
||
be randomly chosen, MUST be at least 128 bits in size, and MUST be at
|
||
least half the key size of the negotiated prf. ("prf" refers to
|
||
"pseudo-random function", one of the cryptographic algorithms
|
||
negotiated in the IKE exchange.) {{ Clarif-7.4 }} However, the
|
||
initiator chooses the nonce before the outcome of the negotiation is
|
||
known. Because of that, the nonce has to be long enough for all the
|
||
PRFs being proposed. If the same random number source is used for
|
||
both keys and nonces, care must be taken to ensure that the latter
|
||
use does not compromise the former.
|
||
|
||
2.11. Address and Port Agility
|
||
|
||
IKE runs over UDP ports 500 and 4500, and implicitly sets up ESP and
|
||
AH associations for the same IP addresses it runs over. The IP
|
||
addresses and ports in the outer header are, however, not themselves
|
||
cryptographically protected, and IKE is designed to work even through
|
||
Network Address Translation (NAT) boxes. An implementation MUST
|
||
accept incoming requests even if the source port is not 500 or 4500,
|
||
and MUST respond to the address and port from which the request was
|
||
received. It MUST specify the address and port at which the request
|
||
was received as the source address and port in the response. IKE
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 39]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
functions identically over IPv4 or IPv6.
|
||
|
||
2.12. Reuse of Diffie-Hellman Exponentials
|
||
|
||
IKE generates keying material using an ephemeral Diffie-Hellman
|
||
exchange in order to gain the property of "perfect forward secrecy".
|
||
This means that once a connection is closed and its corresponding
|
||
keys are forgotten, even someone who has recorded all of the data
|
||
from the connection and gets access to all of the long-term keys of
|
||
the two endpoints cannot reconstruct the keys used to protect the
|
||
conversation without doing a brute force search of the session key
|
||
space.
|
||
|
||
Achieving perfect forward secrecy requires that when a connection is
|
||
closed, each endpoint MUST forget not only the keys used by the
|
||
connection but also any information that could be used to recompute
|
||
those keys. In particular, it MUST forget the secrets used in the
|
||
Diffie-Hellman calculation and any state that may persist in the
|
||
state of a pseudo-random number generator that could be used to
|
||
recompute the Diffie-Hellman secrets.
|
||
|
||
Since the computing of Diffie-Hellman exponentials is computationally
|
||
expensive, an endpoint may find it advantageous to reuse those
|
||
exponentials for multiple connection setups. There are several
|
||
reasonable strategies for doing this. An endpoint could choose a new
|
||
exponential only periodically though this could result in less-than-
|
||
perfect forward secrecy if some connection lasts for less than the
|
||
lifetime of the exponential. Or it could keep track of which
|
||
exponential was used for each connection and delete the information
|
||
associated with the exponential only when some corresponding
|
||
connection was closed. This would allow the exponential to be reused
|
||
without losing perfect forward secrecy at the cost of maintaining
|
||
more state.
|
||
|
||
Decisions as to whether and when to reuse Diffie-Hellman exponentials
|
||
is a private decision in the sense that it will not affect
|
||
interoperability. An implementation that reuses exponentials MAY
|
||
choose to remember the exponential used by the other endpoint on past
|
||
exchanges and if one is reused to avoid the second half of the
|
||
calculation.
|
||
|
||
2.13. Generating Keying Material
|
||
|
||
In the context of the IKE_SA, four cryptographic algorithms are
|
||
negotiated: an encryption algorithm, an integrity protection
|
||
algorithm, a Diffie-Hellman group, and a pseudo-random function
|
||
(prf). The pseudo-random function is used for the construction of
|
||
keying material for all of the cryptographic algorithms used in both
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 40]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
the IKE_SA and the CHILD_SAs.
|
||
|
||
We assume that each encryption algorithm and integrity protection
|
||
algorithm uses a fixed-size key and that any randomly chosen value of
|
||
that fixed size can serve as an appropriate key. For algorithms that
|
||
accept a variable length key, a fixed key size MUST be specified as
|
||
part of the cryptographic transform negotiated (see Section 3.3.5 for
|
||
the defintion of the Key Length transform attribute). For algorithms
|
||
for which not all values are valid keys (such as DES or 3DES with key
|
||
parity), the algorithm by which keys are derived from arbitrary
|
||
values MUST be specified by the cryptographic transform. For
|
||
integrity protection functions based on Hashed Message Authentication
|
||
Code (HMAC), the fixed key size is the size of the output of the
|
||
underlying hash function.
|
||
|
||
It is assumed that pseudo-random functions (PRFs) accept keys of any
|
||
length, but have a preferred key size. The preferred key size is
|
||
used as the length of SK_d, SK_pi, and SK_pr (see Section 2.14). For
|
||
PRFs based on the HMAC construction, the preferred key size is equal
|
||
to the length of the output of the underlying hash function. Other
|
||
types of PRFs MUST specify their preferred key size.
|
||
|
||
Keying material will always be derived as the output of the
|
||
negotiated prf algorithm. Since the amount of keying material needed
|
||
may be greater than the size of the output of the prf algorithm, we
|
||
will use the prf iteratively. We will use the terminology prf+ to
|
||
describe the function that outputs a pseudo-random stream based on
|
||
the inputs to a prf as follows: (where | indicates concatenation)
|
||
|
||
prf+ (K,S) = T1 | T2 | T3 | T4 | ...
|
||
|
||
where:
|
||
T1 = prf (K, S | 0x01)
|
||
T2 = prf (K, T1 | S | 0x02)
|
||
T3 = prf (K, T2 | S | 0x03)
|
||
T4 = prf (K, T3 | S | 0x04)
|
||
|
||
continuing as needed to compute all required keys. The keys are
|
||
taken from the output string without regard to boundaries (e.g., if
|
||
the required keys are a 256-bit Advanced Encryption Standard (AES)
|
||
key and a 160-bit HMAC key, and the prf function generates 160 bits,
|
||
the AES key will come from T1 and the beginning of T2, while the HMAC
|
||
key will come from the rest of T2 and the beginning of T3).
|
||
|
||
The constant concatenated to the end of each string feeding the prf
|
||
is a single octet. prf+ in this document is not defined beyond 255
|
||
times the size of the prf output.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 41]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
2.14. Generating Keying Material for the IKE_SA
|
||
|
||
The shared keys are computed as follows. A quantity called SKEYSEED
|
||
is calculated from the nonces exchanged during the IKE_SA_INIT
|
||
exchange and the Diffie-Hellman shared secret established during that
|
||
exchange. SKEYSEED is used to calculate seven other secrets: SK_d
|
||
used for deriving new keys for the CHILD_SAs established with this
|
||
IKE_SA; SK_ai and SK_ar used as a key to the integrity protection
|
||
algorithm for authenticating the component messages of subsequent
|
||
exchanges; SK_ei and SK_er used for encrypting (and of course
|
||
decrypting) all subsequent exchanges; and SK_pi and SK_pr, which are
|
||
used when generating an AUTH payload. The lengths of SK_d, SK_pi,
|
||
and SK_pr are the preferred key length of the agreed-to PRF.
|
||
|
||
SKEYSEED and its derivatives are computed as follows:
|
||
|
||
SKEYSEED = prf(Ni | Nr, g^ir)
|
||
|
||
{SK_d | SK_ai | SK_ar | SK_ei | SK_er | SK_pi | SK_pr }
|
||
= prf+ (SKEYSEED, Ni | Nr | SPIi | SPIr )
|
||
|
||
(indicating that the quantities SK_d, SK_ai, SK_ar, SK_ei, SK_er,
|
||
SK_pi, and SK_pr are taken in order from the generated bits of the
|
||
prf+). g^ir is the shared secret from the ephemeral Diffie-Hellman
|
||
exchange. g^ir is represented as a string of octets in big endian
|
||
order padded with zeros if necessary to make it the length of the
|
||
modulus. Ni and Nr are the nonces, stripped of any headers. For
|
||
historical backwards-compatibility reasons, there are two PRFs that
|
||
are treated specially in this calculation. If the negotiated PRF is
|
||
AES-XCBC-PRF-128 [RFC4434] or AES-CMAC-PRF-128 [RFC4615], only the
|
||
first 64 bits of Ni and the first 64 bits of Nr are used in the
|
||
calculation.
|
||
|
||
The two directions of traffic flow use different keys. The keys used
|
||
to protect messages from the original initiator are SK_ai and SK_ei.
|
||
The keys used to protect messages in the other direction are SK_ar
|
||
and SK_er.
|
||
|
||
2.15. Authentication of the IKE_SA
|
||
|
||
When not using extensible authentication (see Section 2.16), the
|
||
peers are authenticated by having each sign (or MAC using a shared
|
||
secret as the key) a block of data. For the responder, the octets to
|
||
be signed start with the first octet of the first SPI in the header
|
||
of the second message (IKE_SA_INIT response) and end with the last
|
||
octet of the last payload in the second message. Appended to this
|
||
(for purposes of computing the signature) are the initiator's nonce
|
||
Ni (just the value, not the payload containing it), and the value
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 42]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
prf(SK_pr,IDr') where IDr' is the responder's ID payload excluding
|
||
the fixed header. Note that neither the nonce Ni nor the value
|
||
prf(SK_pr,IDr') are transmitted. Similarly, the initiator signs the
|
||
first message (IKE_SA_INIT request), starting with the first octet of
|
||
the first SPI in the header and ending with the last octet of the
|
||
last payload. Appended to this (for purposes of computing the
|
||
signature) are the responder's nonce Nr, and the value
|
||
prf(SK_pi,IDi'). In the above calculation, IDi' and IDr' are the
|
||
entire ID payloads excluding the fixed header. It is critical to the
|
||
security of the exchange that each side sign the other side's nonce.
|
||
|
||
{{ Clarif-3.1 }}
|
||
|
||
The initiator's signed octets can be described as:
|
||
|
||
InitiatorSignedOctets = RealMessage1 | NonceRData | MACedIDForI
|
||
GenIKEHDR = [ four octets 0 if using port 4500 ] | RealIKEHDR
|
||
RealIKEHDR = SPIi | SPIr | . . . | Length
|
||
RealMessage1 = RealIKEHDR | RestOfMessage1
|
||
NonceRPayload = PayloadHeader | NonceRData
|
||
InitiatorIDPayload = PayloadHeader | RestOfIDPayload
|
||
RestOfInitIDPayload = IDType | RESERVED | InitIDData
|
||
MACedIDForI = prf(SK_pi, RestOfInitIDPayload)
|
||
|
||
The responder's signed octets can be described as:
|
||
|
||
ResponderSignedOctets = RealMessage2 | NonceIData | MACedIDForR
|
||
GenIKEHDR = [ four octets 0 if using port 4500 ] | RealIKEHDR
|
||
RealIKEHDR = SPIi | SPIr | . . . | Length
|
||
RealMessage2 = RealIKEHDR | RestOfMessage2
|
||
NonceIPayload = PayloadHeader | NonceIData
|
||
ResponderIDPayload = PayloadHeader | RestOfIDPayload
|
||
RestOfRespIDPayload = IDType | RESERVED | InitIDData
|
||
MACedIDForR = prf(SK_pr, RestOfRespIDPayload)
|
||
|
||
Note that all of the payloads are included under the signature,
|
||
including any payload types not defined in this document. If the
|
||
first message of the exchange is sent twice (the second time with a
|
||
responder cookie and/or a different Diffie-Hellman group), it is the
|
||
second version of the message that is signed.
|
||
|
||
Optionally, messages 3 and 4 MAY include a certificate, or
|
||
certificate chain providing evidence that the key used to compute a
|
||
digital signature belongs to the name in the ID payload. The
|
||
signature or MAC will be computed using algorithms dictated by the
|
||
type of key used by the signer, and specified by the Auth Method
|
||
field in the Authentication payload. There is no requirement that
|
||
the initiator and responder sign with the same cryptographic
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 43]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
algorithms. The choice of cryptographic algorithms depends on the
|
||
type of key each has. In particular, the initiator may be using a
|
||
shared key while the responder may have a public signature key and
|
||
certificate. It will commonly be the case (but it is not required)
|
||
that if a shared secret is used for authentication that the same key
|
||
is used in both directions.
|
||
|
||
Note that it is a common but typically insecure practice to have a
|
||
shared key derived solely from a user-chosen password without
|
||
incorporating another source of randomness. This is typically
|
||
insecure because user-chosen passwords are unlikely to have
|
||
sufficient unpredictability to resist dictionary attacks and these
|
||
attacks are not prevented in this authentication method.
|
||
(Applications using password-based authentication for bootstrapping
|
||
and IKE_SA should use the authentication method in Section 2.16,
|
||
which is designed to prevent off-line dictionary attacks.) {{ Demoted
|
||
the SHOULD }} The pre-shared key needs to contain as much
|
||
unpredictability as the strongest key being negotiated. In the case
|
||
of a pre-shared key, the AUTH value is computed as:
|
||
|
||
AUTH = prf(prf(Shared Secret,"Key Pad for IKEv2"), <msg octets>)
|
||
|
||
where the string "Key Pad for IKEv2" is 17 ASCII characters without
|
||
null termination. The shared secret can be variable length. The pad
|
||
string is added so that if the shared secret is derived from a
|
||
password, the IKE implementation need not store the password in
|
||
cleartext, but rather can store the value prf(Shared Secret,"Key Pad
|
||
for IKEv2"), which could not be used as a password equivalent for
|
||
protocols other than IKEv2. As noted above, deriving the shared
|
||
secret from a password is not secure. This construction is used
|
||
because it is anticipated that people will do it anyway. The
|
||
management interface by which the Shared Secret is provided MUST
|
||
accept ASCII strings of at least 64 octets and MUST NOT add a null
|
||
terminator before using them as shared secrets. It MUST also accept
|
||
a hex encoding of the Shared Secret. The management interface MAY
|
||
accept other encodings if the algorithm for translating the encoding
|
||
to a binary string is specified.
|
||
|
||
2.16. Extensible Authentication Protocol Methods
|
||
|
||
In addition to authentication using public key signatures and shared
|
||
secrets, IKE supports authentication using methods defined in RFC
|
||
3748 [EAP]. Typically, these methods are asymmetric (designed for a
|
||
user authenticating to a server), and they may not be mutual. {{ In
|
||
the next sentence, changed "public key signature based" to "strong"
|
||
}} For this reason, these protocols are typically used to
|
||
authenticate the initiator to the responder and MUST be used in
|
||
conjunction with a strong authentication of the responder to the
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 44]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
initiator. These methods are often associated with mechanisms
|
||
referred to as "Legacy Authentication" mechanisms.
|
||
|
||
While this memo references [EAP] with the intent that new methods can
|
||
be added in the future without updating this specification, some
|
||
simpler variations are documented here and in Section 3.16. [EAP]
|
||
defines an authentication protocol requiring a variable number of
|
||
messages. Extensible Authentication is implemented in IKE as
|
||
additional IKE_AUTH exchanges that MUST be completed in order to
|
||
initialize the IKE_SA.
|
||
|
||
An initiator indicates a desire to use extensible authentication by
|
||
leaving out the AUTH payload from message 3. By including an IDi
|
||
payload but not an AUTH payload, the initiator has declared an
|
||
identity but has not proven it. If the responder is willing to use
|
||
an extensible authentication method, it will place an Extensible
|
||
Authentication Protocol (EAP) payload in message 4 and defer sending
|
||
SAr2, TSi, and TSr until initiator authentication is complete in a
|
||
subsequent IKE_AUTH exchange. In the case of a minimal extensible
|
||
authentication, the initial SA establishment will appear as follows:
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SAi1, KEi, Ni -->
|
||
<-- HDR, SAr1, KEr, Nr, [CERTREQ]
|
||
HDR, SK {IDi, [CERTREQ,]
|
||
[IDr,] SAi2,
|
||
TSi, TSr} -->
|
||
<-- HDR, SK {IDr, [CERT,] AUTH,
|
||
EAP }
|
||
HDR, SK {EAP} -->
|
||
<-- HDR, SK {EAP (success)}
|
||
HDR, SK {AUTH} -->
|
||
<-- HDR, SK {AUTH, SAr2, TSi, TSr }
|
||
|
||
{{ Clarif-3.10 }} As described in Section 2.2, when EAP is used, each
|
||
pair of IKE_SA initial setup messages will have their message numbers
|
||
incremented; the first pair of AUTH messages will have an ID of 1,
|
||
the second will be 2, and so on.
|
||
|
||
For EAP methods that create a shared key as a side effect of
|
||
authentication, that shared key MUST be used by both the initiator
|
||
and responder to generate AUTH payloads in messages 7 and 8 using the
|
||
syntax for shared secrets specified in Section 2.15. The shared key
|
||
from EAP is the field from the EAP specification named MSK. The
|
||
shared key generated during an IKE exchange MUST NOT be used for any
|
||
other purpose.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 45]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
EAP methods that do not establish a shared key SHOULD NOT be used, as
|
||
they are subject to a number of man-in-the-middle attacks [EAPMITM]
|
||
if these EAP methods are used in other protocols that do not use a
|
||
server-authenticated tunnel. Please see the Security Considerations
|
||
section for more details. If EAP methods that do not generate a
|
||
shared key are used, the AUTH payloads in messages 7 and 8 MUST be
|
||
generated using SK_pi and SK_pr, respectively.
|
||
|
||
{{ Demoted the SHOULD }} The initiator of an IKE_SA using EAP needs
|
||
to be capable of extending the initial protocol exchange to at least
|
||
ten IKE_AUTH exchanges in the event the responder sends notification
|
||
messages and/or retries the authentication prompt. Once the protocol
|
||
exchange defined by the chosen EAP authentication method has
|
||
successfully terminated, the responder MUST send an EAP payload
|
||
containing the Success message. Similarly, if the authentication
|
||
method has failed, the responder MUST send an EAP payload containing
|
||
the Failure message. The responder MAY at any time terminate the IKE
|
||
exchange by sending an EAP payload containing the Failure message.
|
||
|
||
Following such an extended exchange, the EAP AUTH payloads MUST be
|
||
included in the two messages following the one containing the EAP
|
||
Success message.
|
||
|
||
{{ Clarif-3.5 }} When the initiator authentication uses EAP, it is
|
||
possible that the contents of the IDi payload is used only for AAA
|
||
routing purposes and selecting which EAP method to use. This value
|
||
may be different from the identity authenticated by the EAP method.
|
||
It is important that policy lookups and access control decisions use
|
||
the actual authenticated identity. Often the EAP server is
|
||
implemented in a separate AAA server that communicates with the IKEv2
|
||
responder. In this case, the authenticated identity has to be sent
|
||
from the AAA server to the IKEv2 responder.
|
||
|
||
2.17. Generating Keying Material for CHILD_SAs
|
||
|
||
A single CHILD_SA is created by the IKE_AUTH exchange, and additional
|
||
CHILD_SAs can optionally be created in CREATE_CHILD_SA exchanges.
|
||
Keying material for them is generated as follows:
|
||
|
||
KEYMAT = prf+(SK_d, Ni | Nr)
|
||
|
||
Where Ni and Nr are the nonces from the IKE_SA_INIT exchange if this
|
||
request is the first CHILD_SA created or the fresh Ni and Nr from the
|
||
CREATE_CHILD_SA exchange if this is a subsequent creation.
|
||
|
||
For CREATE_CHILD_SA exchanges including an optional Diffie-Hellman
|
||
exchange, the keying material is defined as:
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 46]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
KEYMAT = prf+(SK_d, g^ir (new) | Ni | Nr )
|
||
|
||
where g^ir (new) is the shared secret from the ephemeral Diffie-
|
||
Hellman exchange of this CREATE_CHILD_SA exchange (represented as an
|
||
octet string in big endian order padded with zeros in the high-order
|
||
bits if necessary to make it the length of the modulus).
|
||
|
||
For ESP and AH, a single CHILD_SA negotiation results in two security
|
||
associations (one in each direction). Keying material MUST be taken
|
||
from the expanded KEYMAT in the following order:
|
||
|
||
o The encryption key (if any) for the SA carrying data from the
|
||
initiator to the responder.
|
||
|
||
o The authentication key (if any) for the SA carrying data from the
|
||
initiator to the responder.
|
||
|
||
o The encryption key (if any) for the SA carrying data from the
|
||
responder to the initiator.
|
||
|
||
o The authentication key (if any) for the SA carrying data from the
|
||
responder to the initiator.
|
||
|
||
Each cryptographic algorithm takes a fixed number of bits of keying
|
||
material specified as part of the algorithm, or negotiated in SA
|
||
payloads (see Section 2.13 for description of key lengths, and
|
||
Section 3.3.5 for the definition of the Key Length transform
|
||
attribute).
|
||
|
||
2.18. Rekeying IKE_SAs Using a CREATE_CHILD_SA Exchange
|
||
|
||
The CREATE_CHILD_SA exchange can be used to rekey an existing IKE_SA
|
||
(see Section 2.8). {{ Clarif-5.3 }} New initiator and responder SPIs
|
||
are supplied in the SPI fields in the Proposal structures inside the
|
||
Security Association (SA) payloads (not the SPI fields in the IKE
|
||
header). The TS payloads are omitted when rekeying an IKE_SA.
|
||
SKEYSEED for the new IKE_SA is computed using SK_d from the existing
|
||
IKE_SA as follows:
|
||
|
||
SKEYSEED = prf(SK_d (old), [g^ir (new)] | Ni | Nr)
|
||
|
||
where g^ir (new) is the shared secret from the ephemeral Diffie-
|
||
Hellman exchange of this CREATE_CHILD_SA exchange (represented as an
|
||
octet string in big endian order padded with zeros if necessary to
|
||
make it the length of the modulus) and Ni and Nr are the two nonces
|
||
stripped of any headers.
|
||
|
||
{{ Clarif-5.5 }} The old and new IKE_SA may have selected a different
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 47]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
PRF. Because the rekeying exchange belongs to the old IKE_SA, it is
|
||
the old IKE_SA's PRF that is used.
|
||
|
||
{{ Clarif-5.12}} The main purpose of rekeying the IKE_SA is to ensure
|
||
that the compromise of old keying material does not provide
|
||
information about the current keys, or vice versa. Therefore,
|
||
implementations SHOULD perform a new Diffie-Hellman exchange when
|
||
rekeying the IKE_SA. In other words, an initiator SHOULD NOT propose
|
||
the value "NONE" for the D-H transform, and a responder SHOULD NOT
|
||
accept such a proposal. This means that a succesful exchange
|
||
rekeying the IKE_SA always includes the KEi/KEr payloads.
|
||
|
||
The new IKE_SA MUST reset its message counters to 0.
|
||
|
||
SK_d, SK_ai, SK_ar, SK_ei, and SK_er are computed from SKEYSEED as
|
||
specified in Section 2.14.
|
||
|
||
2.19. Requesting an Internal Address on a Remote Network
|
||
|
||
Most commonly occurring in the endpoint-to-security-gateway scenario,
|
||
an endpoint may need an IP address in the network protected by the
|
||
security gateway and may need to have that address dynamically
|
||
assigned. A request for such a temporary address can be included in
|
||
any request to create a CHILD_SA (including the implicit request in
|
||
message 3) by including a CP payload.
|
||
|
||
This function provides address allocation to an IPsec Remote Access
|
||
Client (IRAC) trying to tunnel into a network protected by an IPsec
|
||
Remote Access Server (IRAS). Since the IKE_AUTH exchange creates an
|
||
IKE_SA and a CHILD_SA, the IRAC MUST request the IRAS-controlled
|
||
address (and optionally other information concerning the protected
|
||
network) in the IKE_AUTH exchange. The IRAS may procure an address
|
||
for the IRAC from any number of sources such as a DHCP/BOOTP server
|
||
or its own address pool.
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SK {IDi, [CERT,]
|
||
[CERTREQ,] [IDr,] AUTH,
|
||
CP(CFG_REQUEST), SAi2,
|
||
TSi, TSr} -->
|
||
<-- HDR, SK {IDr, [CERT,] AUTH,
|
||
CP(CFG_REPLY), SAr2,
|
||
TSi, TSr}
|
||
|
||
In all cases, the CP payload MUST be inserted before the SA payload.
|
||
In variations of the protocol where there are multiple IKE_AUTH
|
||
exchanges, the CP payloads MUST be inserted in the messages
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 48]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
containing the SA payloads.
|
||
|
||
CP(CFG_REQUEST) MUST contain at least an INTERNAL_ADDRESS attribute
|
||
(either IPv4 or IPv6) but MAY contain any number of additional
|
||
attributes the initiator wants returned in the response.
|
||
|
||
{{ 3.10.1-37 }} The FAILED_CP_REQUIRED notification is sent by
|
||
responder in the case where CP(CFG_REQUEST) was expected but not
|
||
received, and so is a conflict with locally configured policy. There
|
||
is no associated data.
|
||
|
||
For example, message from initiator to responder:
|
||
|
||
CP(CFG_REQUEST)=
|
||
INTERNAL_ADDRESS()
|
||
TSi = (0, 0-65535,0.0.0.0-255.255.255.255)
|
||
TSr = (0, 0-65535,0.0.0.0-255.255.255.255)
|
||
|
||
NOTE: Traffic Selectors contain (protocol, port range, address
|
||
range).
|
||
|
||
Message from responder to initiator:
|
||
|
||
CP(CFG_REPLY)=
|
||
INTERNAL_ADDRESS(192.0.2.202)
|
||
INTERNAL_NETMASK(255.255.255.0)
|
||
INTERNAL_SUBNET(192.0.2.0/255.255.255.0)
|
||
TSi = (0, 0-65535,192.0.2.202-192.0.2.202)
|
||
TSr = (0, 0-65535,192.0.2.0-192.0.2.255)
|
||
|
||
All returned values will be implementation dependent. As can be seen
|
||
in the above example, the IRAS MAY also send other attributes that
|
||
were not included in CP(CFG_REQUEST) and MAY ignore the non-
|
||
mandatory attributes that it does not support.
|
||
|
||
The responder MUST NOT send a CFG_REPLY without having first received
|
||
a CP(CFG_REQUEST) from the initiator, because we do not want the IRAS
|
||
to perform an unnecessary configuration lookup if the IRAC cannot
|
||
process the REPLY. In the case where the IRAS's configuration
|
||
requires that CP be used for a given identity IDi, but IRAC has
|
||
failed to send a CP(CFG_REQUEST), IRAS MUST fail the request, and
|
||
terminate the IKE exchange with a FAILED_CP_REQUIRED error.
|
||
|
||
2.19.1. Configuration Payloads
|
||
|
||
Editor's note: some of this sub-section is redundant and will go away
|
||
in the next version of the document.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 49]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
In support of the scenario described in Section 1.1.3, an initiator
|
||
may request that the responder assign an IP address and tell the
|
||
initiator what it is. {{ Clarif-6.1 }} That request is done using
|
||
configuration payloads, not traffic selectors. An address in a TSi
|
||
payload in a response does not mean that the responder has assigned
|
||
that address to the initiator: it only means that if packets matching
|
||
these traffic selectors are sent by the initiator, IPsec processing
|
||
can be performed as agreed for this SA.
|
||
|
||
Configuration payloads are of type CFG_REQUEST/CFG_REPLY or CFG_SET/
|
||
CFG_ACK (see CFG Type in the payload description below). CFG_REQUEST
|
||
and CFG_SET payloads may optionally be added to any IKE request. The
|
||
IKE response MUST include either a corresponding CFG_REPLY or CFG_ACK
|
||
or a Notify payload with an error type indicating why the request
|
||
could not be honored. An exception is that a minimal implementation
|
||
MAY ignore all CFG_REQUEST and CFG_SET payloads, so a response
|
||
message without a corresponding CFG_REPLY or CFG_ACK MUST be accepted
|
||
as an indication that the request was not supported.
|
||
|
||
"CFG_REQUEST/CFG_REPLY" allows an IKE endpoint to request information
|
||
from its peer. If an attribute in the CFG_REQUEST Configuration
|
||
Payload is not zero-length, it is taken as a suggestion for that
|
||
attribute. The CFG_REPLY Configuration Payload MAY return that
|
||
value, or a new one. It MAY also add new attributes and not include
|
||
some requested ones. Requestors MUST ignore returned attributes that
|
||
they do not recognize.
|
||
|
||
Some attributes MAY be multi-valued, in which case multiple attribute
|
||
values of the same type are sent and/or returned. Generally, all
|
||
values of an attribute are returned when the attribute is requested.
|
||
For some attributes (in this version of the specification only
|
||
internal addresses), multiple requests indicates a request that
|
||
multiple values be assigned. For these attributes, the number of
|
||
values returned SHOULD NOT exceed the number requested.
|
||
|
||
If the data type requested in a CFG_REQUEST is not recognized or not
|
||
supported, the responder MUST NOT return an error type but rather
|
||
MUST either send a CFG_REPLY that MAY be empty or a reply not
|
||
containing a CFG_REPLY payload at all. Error returns are reserved
|
||
for cases where the request is recognized but cannot be performed as
|
||
requested or the request is badly formatted.
|
||
|
||
"CFG_SET/CFG_ACK" allows an IKE endpoint to push configuration data
|
||
to its peer. In this case, the CFG_SET Configuration Payload
|
||
contains attributes the initiator wants its peer to alter. The
|
||
responder MUST return a Configuration Payload if it accepted any of
|
||
the configuration data and it MUST contain the attributes that the
|
||
responder accepted with zero-length data. Those attributes that it
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 50]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
did not accept MUST NOT be in the CFG_ACK Configuration Payload. If
|
||
no attributes were accepted, the responder MUST return either an
|
||
empty CFG_ACK payload or a response message without a CFG_ACK
|
||
payload. There are currently no defined uses for the CFG_SET/CFG_ACK
|
||
exchange, though they may be used in connection with extensions based
|
||
on Vendor IDs. An minimal implementation of this specification MAY
|
||
ignore CFG_SET payloads.
|
||
|
||
{{ Demoted the SHOULD }} Extensions via the CP payload should not be
|
||
used for general purpose management. Its main intent is to provide a
|
||
bootstrap mechanism to exchange information within IPsec from IRAS to
|
||
IRAC. While it MAY be useful to use such a method to exchange
|
||
information between some Security Gateways (SGW) or small networks,
|
||
existing management protocols such as DHCP [DHCP], RADIUS [RADIUS],
|
||
SNMP, or LDAP [LDAP] should be preferred for enterprise management as
|
||
well as subsequent information exchanges.
|
||
|
||
2.20. Requesting the Peer's Version
|
||
|
||
An IKE peer wishing to inquire about the other peer's IKE software
|
||
version information MAY use the method below. This is an example of
|
||
a configuration request within an INFORMATIONAL exchange, after the
|
||
IKE_SA and first CHILD_SA have been created.
|
||
|
||
An IKE implementation MAY decline to give out version information
|
||
prior to authentication or even after authentication to prevent
|
||
trolling in case some implementation is known to have some security
|
||
weakness. In that case, it MUST either return an empty string or no
|
||
CP payload if CP is not supported.
|
||
|
||
Initiator Responder
|
||
-------------------------------------------------------------------
|
||
HDR, SK{CP(CFG_REQUEST)} -->
|
||
<-- HDR, SK{CP(CFG_REPLY)}
|
||
|
||
CP(CFG_REQUEST)=
|
||
APPLICATION_VERSION("")
|
||
|
||
CP(CFG_REPLY) APPLICATION_VERSION("foobar v1.3beta, (c) Foo Bar
|
||
Inc.")
|
||
|
||
2.21. Error Handling
|
||
|
||
There are many kinds of errors that can occur during IKE processing.
|
||
If a request is received that is badly formatted or unacceptable for
|
||
reasons of policy (e.g., no matching cryptographic algorithms), the
|
||
response MUST contain a Notify payload indicating the error. If an
|
||
error occurs outside the context of an IKE request (e.g., the node is
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 51]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
getting ESP messages on a nonexistent SPI), the node SHOULD initiate
|
||
an INFORMATIONAL exchange with a Notify payload describing the
|
||
problem.
|
||
|
||
Errors that occur before a cryptographically protected IKE_SA is
|
||
established must be handled very carefully. There is a trade-off
|
||
between wanting to be helpful in diagnosing a problem and responding
|
||
to it and wanting to avoid being a dupe in a denial of service attack
|
||
based on forged messages.
|
||
|
||
If a node receives a message on UDP port 500 or 4500 outside the
|
||
context of an IKE_SA known to it (and not a request to start one), it
|
||
may be the result of a recent crash of the node. If the message is
|
||
marked as a response, the node MAY audit the suspicious event but
|
||
MUST NOT respond. If the message is marked as a request, the node
|
||
MAY audit the suspicious event and MAY send a response. If a
|
||
response is sent, the response MUST be sent to the IP address and
|
||
port from whence it came with the same IKE SPIs and the Message ID
|
||
copied. The response MUST NOT be cryptographically protected and
|
||
MUST contain a Notify payload indicating INVALID_IKE_SPI. {{ 3.10.1-4
|
||
}} The INVALID_IKE_SPI notification indicates an IKE message was
|
||
received with an unrecognized destination SPI; this usually indicates
|
||
that the recipient has rebooted and forgotten the existence of an
|
||
IKE_SA.
|
||
|
||
A node receiving such an unprotected Notify payload MUST NOT respond
|
||
and MUST NOT change the state of any existing SAs. The message might
|
||
be a forgery or might be a response the genuine correspondent was
|
||
tricked into sending. {{ Demoted two SHOULDs }} A node should treat
|
||
such a message (and also a network message like ICMP destination
|
||
unreachable) as a hint that there might be problems with SAs to that
|
||
IP address and should initiate a liveness test for any such IKE_SA.
|
||
An implementation SHOULD limit the frequency of such tests to avoid
|
||
being tricked into participating in a denial of service attack.
|
||
|
||
A node receiving a suspicious message from an IP address with which
|
||
it has an IKE_SA MAY send an IKE Notify payload in an IKE
|
||
INFORMATIONAL exchange over that SA. {{ Demoted the SHOULD }} The
|
||
recipient MUST NOT change the state of any SAs as a result, but may
|
||
wish to audit the event to aid in diagnosing malfunctions. A node
|
||
MUST limit the rate at which it will send messages in response to
|
||
unprotected messages.
|
||
|
||
2.22. IPComp
|
||
|
||
Use of IP compression [IPCOMP] can be negotiated as part of the setup
|
||
of a CHILD_SA. While IP compression involves an extra header in each
|
||
packet and a compression parameter index (CPI), the virtual
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 52]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
"compression association" has no life outside the ESP or AH SA that
|
||
contains it. Compression associations disappear when the
|
||
corresponding ESP or AH SA goes away. It is not explicitly mentioned
|
||
in any DELETE payload.
|
||
|
||
Negotiation of IP compression is separate from the negotiation of
|
||
cryptographic parameters associated with a CHILD_SA. A node
|
||
requesting a CHILD_SA MAY advertise its support for one or more
|
||
compression algorithms through one or more Notify payloads of type
|
||
IPCOMP_SUPPORTED. This notification may be included only in a
|
||
message containing an SA payload negotiating a CHILD_SA and indicates
|
||
a willingness by its sender to use IPComp on this SA. The response
|
||
MAY indicate acceptance of a single compression algorithm with a
|
||
Notify payload of type IPCOMP_SUPPORTED. These payloads MUST NOT
|
||
occur in messages that do not contain SA payloads.
|
||
|
||
{{ 3.10.1-16387 }}The data associated with this notification includes
|
||
a two-octet IPComp CPI followed by a one-octet transform ID
|
||
optionally followed by attributes whose length and format are defined
|
||
by that transform ID. A message proposing an SA may contain multiple
|
||
IPCOMP_SUPPORTED notifications to indicate multiple supported
|
||
algorithms. A message accepting an SA may contain at most one.
|
||
|
||
The transform IDs currently defined are:
|
||
|
||
Name Number Defined In
|
||
-------------------------------------
|
||
RESERVED 0
|
||
IPCOMP_OUI 1
|
||
IPCOMP_DEFLATE 2 RFC 2394
|
||
IPCOMP_LZS 3 RFC 2395
|
||
IPCOMP_LZJH 4 RFC 3051
|
||
RESERVED TO IANA 5-240
|
||
PRIVATE USE 241-255
|
||
|
||
Although there has been discussion of allowing multiple compression
|
||
algorithms to be accepted and to have different compression
|
||
algorithms available for the two directions of a CHILD_SA,
|
||
implementations of this specification MUST NOT accept an IPComp
|
||
algorithm that was not proposed, MUST NOT accept more than one, and
|
||
MUST NOT compress using an algorithm other than one proposed and
|
||
accepted in the setup of the CHILD_SA.
|
||
|
||
A side effect of separating the negotiation of IPComp from
|
||
cryptographic parameters is that it is not possible to propose
|
||
multiple cryptographic suites and propose IP compression with some of
|
||
them but not others.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 53]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
2.23. NAT Traversal
|
||
|
||
Network Address Translation (NAT) gateways are a controversial
|
||
subject. This section briefly describes what they are and how they
|
||
are likely to act on IKE traffic. Many people believe that NATs are
|
||
evil and that we should not design our protocols so as to make them
|
||
work better. IKEv2 does specify some unintuitive processing rules in
|
||
order that NATs are more likely to work.
|
||
|
||
NATs exist primarily because of the shortage of IPv4 addresses,
|
||
though there are other rationales. IP nodes that are "behind" a NAT
|
||
have IP addresses that are not globally unique, but rather are
|
||
assigned from some space that is unique within the network behind the
|
||
NAT but that are likely to be reused by nodes behind other NATs.
|
||
Generally, nodes behind NATs can communicate with other nodes behind
|
||
the same NAT and with nodes with globally unique addresses, but not
|
||
with nodes behind other NATs. There are exceptions to that rule.
|
||
When those nodes make connections to nodes on the real Internet, the
|
||
NAT gateway "translates" the IP source address to an address that
|
||
will be routed back to the gateway. Messages to the gateway from the
|
||
Internet have their destination addresses "translated" to the
|
||
internal address that will route the packet to the correct endnode.
|
||
|
||
NATs are designed to be "transparent" to endnodes. Neither software
|
||
on the node behind the NAT nor the node on the Internet requires
|
||
modification to communicate through the NAT. Achieving this
|
||
transparency is more difficult with some protocols than with others.
|
||
Protocols that include IP addresses of the endpoints within the
|
||
payloads of the packet will fail unless the NAT gateway understands
|
||
the protocol and modifies the internal references as well as those in
|
||
the headers. Such knowledge is inherently unreliable, is a network
|
||
layer violation, and often results in subtle problems.
|
||
|
||
Opening an IPsec connection through a NAT introduces special
|
||
problems. If the connection runs in transport mode, changing the IP
|
||
addresses on packets will cause the checksums to fail and the NAT
|
||
cannot correct the checksums because they are cryptographically
|
||
protected. Even in tunnel mode, there are routing problems because
|
||
transparently translating the addresses of AH and ESP packets
|
||
requires special logic in the NAT and that logic is heuristic and
|
||
unreliable in nature. For that reason, IKEv2 can negotiate UDP
|
||
encapsulation of IKE and ESP packets. This encoding is slightly less
|
||
efficient but is easier for NATs to process. In addition, firewalls
|
||
may be configured to pass IPsec traffic over UDP but not ESP/AH or
|
||
vice versa.
|
||
|
||
It is a common practice of NATs to translate TCP and UDP port numbers
|
||
as well as addresses and use the port numbers of inbound packets to
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 54]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
decide which internal node should get a given packet. For this
|
||
reason, even though IKE packets MUST be sent from and to UDP port
|
||
500, they MUST be accepted coming from any port and responses MUST be
|
||
sent to the port from whence they came. This is because the ports
|
||
may be modified as the packets pass through NATs. Similarly, IP
|
||
addresses of the IKE endpoints are generally not included in the IKE
|
||
payloads because the payloads are cryptographically protected and
|
||
could not be transparently modified by NATs.
|
||
|
||
Port 4500 is reserved for UDP-encapsulated ESP and IKE. When working
|
||
through a NAT, it is generally better to pass IKE packets over port
|
||
4500 because some older NATs handle IKE traffic on port 500 cleverly
|
||
in an attempt to transparently establish IPsec connections between
|
||
endpoints that don't handle NAT traversal themselves. Such NATs may
|
||
interfere with the straightforward NAT traversal envisioned by this
|
||
document. {{ Clarif-7.6 }} An IPsec endpoint that discovers a NAT
|
||
between it and its correspondent MUST send all subsequent traffic
|
||
from port 4500, which NATs should not treat specially (as they might
|
||
with port 500).
|
||
|
||
The specific requirements for supporting NAT traversal [NATREQ] are
|
||
listed below. Support for NAT traversal is optional. In this
|
||
section only, requirements listed as MUST apply only to
|
||
implementations supporting NAT traversal.
|
||
|
||
o IKE MUST listen on port 4500 as well as port 500. IKE MUST
|
||
respond to the IP address and port from which packets arrived.
|
||
|
||
o Both IKE initiator and responder MUST include in their IKE_SA_INIT
|
||
packets Notify payloads of type NAT_DETECTION_SOURCE_IP and
|
||
NAT_DETECTION_DESTINATION_IP. Those payloads can be used to
|
||
detect if there is NAT between the hosts, and which end is behind
|
||
the NAT. The location of the payloads in the IKE_SA_INIT packets
|
||
are just after the Ni and Nr payloads (before the optional CERTREQ
|
||
payload).
|
||
|
||
o {{ 3.10.1-16388 }} The data associated with the
|
||
NAT_DETECTION_SOURCE_IP notification is a SHA-1 digest of the SPIs
|
||
(in the order they appear in the header), IP address, and port on
|
||
which this packet was sent. There MAY be multiple
|
||
NAT_DETECTION_SOURCE_IP payloads in a message if the sender does
|
||
not know which of several network attachments will be used to send
|
||
the packet.
|
||
|
||
o {{ 3.10.1-16389 }} The data associated with the
|
||
NAT_DETECTION_DESTINATION_IP notification is a SHA-1 digest of the
|
||
SPIs (in the order they appear in the header), IP address, and
|
||
port to which this packet was sent.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 55]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
o {{ 3.10.1-16388 }} {{ 3.10.1-16389 }} The recipient of either the
|
||
NAT_DETECTION_SOURCE_IP or NAT_DETECTION_DESTINATION_IP
|
||
notification MAY compare the supplied value to a SHA-1 hash of the
|
||
SPIs, source IP address, and port, and if they don't match it
|
||
SHOULD enable NAT traversal. In the case of a mismatching
|
||
NAT_DETECTION_SOURCE_IP hash, the recipient MAY reject the
|
||
connection attempt if NAT traversal is not supported. In the case
|
||
of a mismatching NAT_DETECTION_DESTINATION_IP hash, it means that
|
||
the system receiving the NAT_DETECTION_DESTINATION_IP payload is
|
||
behind a NAT and that system SHOULD start sending keepalive
|
||
packets as defined in [UDPENCAPS]; alternately, it MAY reject the
|
||
connection attempt if NAT traversal is not supported.
|
||
|
||
o If none of the NAT_DETECTION_SOURCE_IP payload(s) received matches
|
||
the expected value of the source IP and port found from the IP
|
||
header of the packet containing the payload, it means that the
|
||
system sending those payloads is behind NAT (i.e., someone along
|
||
the route changed the source address of the original packet to
|
||
match the address of the NAT box). In this case, the system
|
||
receiving the payloads should allow dynamic update of the other
|
||
systems' IP address, as described later.
|
||
|
||
o If the NAT_DETECTION_DESTINATION_IP payload received does not
|
||
match the hash of the destination IP and port found from the IP
|
||
header of the packet containing the payload, it means that the
|
||
system receiving the NAT_DETECTION_DESTINATION_IP payload is
|
||
behind a NAT. In this case, that system SHOULD start sending
|
||
keepalive packets as explained in [UDPENCAPS].
|
||
|
||
o The IKE initiator MUST check these payloads if present and if they
|
||
do not match the addresses in the outer packet MUST tunnel all
|
||
future IKE and ESP packets associated with this IKE_SA over UDP
|
||
port 4500.
|
||
|
||
o To tunnel IKE packets over UDP port 4500, the IKE header has four
|
||
octets of zero prepended and the result immediately follows the
|
||
UDP header. To tunnel ESP packets over UDP port 4500, the ESP
|
||
header immediately follows the UDP header. Since the first four
|
||
octets of the ESP header contain the SPI, and the SPI cannot
|
||
validly be zero, it is always possible to distinguish ESP and IKE
|
||
messages.
|
||
|
||
o Implementations MUST process received UDP-encapsulated ESP packets
|
||
even when no NAT was detected.
|
||
|
||
o The original source and destination IP address required for the
|
||
transport mode TCP and UDP packet checksum fixup (see [UDPENCAPS])
|
||
are obtained from the Traffic Selectors associated with the
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 56]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
exchange. In the case of NAT traversal, the Traffic Selectors
|
||
MUST contain exactly one IP address, which is then used as the
|
||
original IP address.
|
||
|
||
o There are cases where a NAT box decides to remove mappings that
|
||
are still alive (for example, the keepalive interval is too long,
|
||
or the NAT box is rebooted). To recover in these cases, hosts
|
||
that are not behind a NAT SHOULD send all packets (including
|
||
retransmission packets) to the IP address and port from the last
|
||
valid authenticated packet from the other end (i.e., dynamically
|
||
update the address). A host behind a NAT SHOULD NOT do this
|
||
because it opens a DoS attack possibility. Any authenticated IKE
|
||
packet or any authenticated UDP-encapsulated ESP packet can be
|
||
used to detect that the IP address or the port has changed.
|
||
|
||
Note that similar but probably not identical actions will likely be
|
||
needed to make IKE work with Mobile IP, but such processing is not
|
||
addressed by this document.
|
||
|
||
2.24. Explicit Congestion Notification (ECN)
|
||
|
||
When IPsec tunnels behave as originally specified in [IPSECARCH-OLD],
|
||
ECN usage is not appropriate for the outer IP headers because tunnel
|
||
decapsulation processing discards ECN congestion indications to the
|
||
detriment of the network. ECN support for IPsec tunnels for IKEv1-
|
||
based IPsec requires multiple operating modes and negotiation (see
|
||
[ECN]). IKEv2 simplifies this situation by requiring that ECN be
|
||
usable in the outer IP headers of all tunnel-mode IPsec SAs created
|
||
by IKEv2. Specifically, tunnel encapsulators and decapsulators for
|
||
all tunnel-mode SAs created by IKEv2 MUST support the ECN full-
|
||
functionality option for tunnels specified in [ECN] and MUST
|
||
implement the tunnel encapsulation and decapsulation processing
|
||
specified in [IPSECARCH] to prevent discarding of ECN congestion
|
||
indications.
|
||
|
||
|
||
3. Header and Payload Formats
|
||
|
||
In the tables in this section, some cryptographic primitives and
|
||
configuation attributes are marked as "UNSPECIFIED". These are items
|
||
for which there are no known specifications and therefore
|
||
interoperability is currently impossible. A future specification may
|
||
describe their use, but until such specification is made,
|
||
implementations SHOULD NOT attempt to use items marked as
|
||
"UNSPECIFIED" in implementations that are meant to be interoperable.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 57]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
3.1. The IKE Header
|
||
|
||
IKE messages use UDP ports 500 and/or 4500, with one IKE message per
|
||
UDP datagram. Information from the beginning of the packet through
|
||
the UDP header is largely ignored except that the IP addresses and
|
||
UDP ports from the headers are reversed and used for return packets.
|
||
When sent on UDP port 500, IKE messages begin immediately following
|
||
the UDP header. When sent on UDP port 4500, IKE messages have
|
||
prepended four octets of zero. These four octets of zero are not
|
||
part of the IKE message and are not included in any of the length
|
||
fields or checksums defined by IKE. Each IKE message begins with the
|
||
IKE header, denoted HDR in this memo. Following the header are one
|
||
or more IKE payloads each identified by a "Next Payload" field in the
|
||
preceding payload. Payloads are processed in the order in which they
|
||
appear in an IKE message by invoking the appropriate processing
|
||
routine according to the "Next Payload" field in the IKE header and
|
||
subsequently according to the "Next Payload" field in the IKE payload
|
||
itself until a "Next Payload" field of zero indicates that no
|
||
payloads follow. If a payload of type "Encrypted" is found, that
|
||
payload is decrypted and its contents parsed as additional payloads.
|
||
An Encrypted payload MUST be the last payload in a packet and an
|
||
Encrypted payload MUST NOT contain another Encrypted payload.
|
||
|
||
The Recipient SPI in the header identifies an instance of an IKE
|
||
security association. It is therefore possible for a single instance
|
||
of IKE to multiplex distinct sessions with multiple peers.
|
||
|
||
All multi-octet fields representing integers are laid out in big
|
||
endian order (also known as "most significant byte first", or
|
||
"network byte order").
|
||
|
||
The format of the IKE header is shown in Figure 4.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 58]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| IKE_SA Initiator's SPI |
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| IKE_SA Responder's SPI |
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload | MjVer | MnVer | Exchange Type | Flags |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Message ID |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 4: IKE Header Format
|
||
|
||
o Initiator's SPI (8 octets) - A value chosen by the initiator to
|
||
identify a unique IKE security association. This value MUST NOT
|
||
be zero.
|
||
|
||
o Responder's SPI (8 octets) - A value chosen by the responder to
|
||
identify a unique IKE security association. This value MUST be
|
||
zero in the first message of an IKE Initial Exchange (including
|
||
repeats of that message including a cookie). {{ The phrase "and
|
||
MUST NOT be zero in any other message" was removed; Clarif-2.1 }}
|
||
|
||
o Next Payload (1 octet) - Indicates the type of payload that
|
||
immediately follows the header. The format and value of each
|
||
payload are defined below.
|
||
|
||
o Major Version (4 bits) - Indicates the major version of the IKE
|
||
protocol in use. Implementations based on this version of IKE
|
||
MUST set the Major Version to 2. Implementations based on
|
||
previous versions of IKE and ISAKMP MUST set the Major Version to
|
||
1. Implementations based on this version of IKE MUST reject or
|
||
ignore messages containing a version number greater than 2.
|
||
|
||
o Minor Version (4 bits) - Indicates the minor version of the IKE
|
||
protocol in use. Implementations based on this version of IKE
|
||
MUST set the Minor Version to 0. They MUST ignore the minor
|
||
version number of received messages.
|
||
|
||
o Exchange Type (1 octet) - Indicates the type of exchange being
|
||
used. This constrains the payloads sent in each message and
|
||
orderings of messages in an exchange.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 59]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Exchange Type Value
|
||
----------------------------------
|
||
RESERVED 0-33
|
||
IKE_SA_INIT 34
|
||
IKE_AUTH 35
|
||
CREATE_CHILD_SA 36
|
||
INFORMATIONAL 37
|
||
RESERVED TO IANA 38-239
|
||
PRIVATE USE 240-255
|
||
|
||
o Flags (1 octet) - Indicates specific options that are set for the
|
||
message. Presence of options are indicated by the appropriate bit
|
||
in the flags field being set. The bits are defined LSB first, so
|
||
bit 0 would be the least significant bit of the Flags octet. In
|
||
the description below, a bit being 'set' means its value is '1',
|
||
while 'cleared' means its value is '0'.
|
||
|
||
* X(reserved) (bits 0-2) - These bits MUST be cleared when
|
||
sending and MUST be ignored on receipt.
|
||
|
||
* I(nitiator) (bit 3 of Flags) - This bit MUST be set in messages
|
||
sent by the original initiator of the IKE_SA and MUST be
|
||
cleared in messages sent by the original responder. It is used
|
||
by the recipient to determine which eight octets of the SPI
|
||
were generated by the recipient.
|
||
|
||
* V(ersion) (bit 4 of Flags) - This bit indicates that the
|
||
transmitter is capable of speaking a higher major version
|
||
number of the protocol than the one indicated in the major
|
||
version number field. Implementations of IKEv2 must clear this
|
||
bit when sending and MUST ignore it in incoming messages.
|
||
|
||
* R(esponse) (bit 5 of Flags) - This bit indicates that this
|
||
message is a response to a message containing the same message
|
||
ID. This bit MUST be cleared in all request messages and MUST
|
||
be set in all responses. An IKE endpoint MUST NOT generate a
|
||
response to a message that is marked as being a response.
|
||
|
||
* X(reserved) (bits 6-7 of Flags) - These bits MUST be cleared
|
||
when sending and MUST be ignored on receipt.
|
||
|
||
o Message ID (4 octets) - Message identifier used to control
|
||
retransmission of lost packets and matching of requests and
|
||
responses. It is essential to the security of the protocol
|
||
because it is used to prevent message replay attacks. See
|
||
Section 2.1 and Section 2.2.
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 60]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
o Length (4 octets) - Length of total message (header + payloads) in
|
||
octets.
|
||
|
||
3.2. Generic Payload Header
|
||
|
||
Each IKE payload defined in Section 3.3 through Section 3.16 begins
|
||
with a generic payload header, shown in Figure 5. Figures for each
|
||
payload below will include the generic payload header, but for
|
||
brevity the description of each field will be omitted.
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 5: Generic Payload Header
|
||
|
||
The Generic Payload Header fields are defined as follows:
|
||
|
||
o Next Payload (1 octet) - Identifier for the payload type of the
|
||
next payload in the message. If the current payload is the last
|
||
in the message, then this field will be 0. This field provides a
|
||
"chaining" capability whereby additional payloads can be added to
|
||
a message by appending it to the end of the message and setting
|
||
the "Next Payload" field of the preceding payload to indicate the
|
||
new payload's type. An Encrypted payload, which must always be
|
||
the last payload of a message, is an exception. It contains data
|
||
structures in the format of additional payloads. In the header of
|
||
an Encrypted payload, the Next Payload field is set to the payload
|
||
type of the first contained payload (instead of 0). The payload
|
||
type values are:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 61]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Next Payload Type Notation Value
|
||
--------------------------------------------------
|
||
No Next Payload 0
|
||
RESERVED 1-32
|
||
Security Association SA 33
|
||
Key Exchange KE 34
|
||
Identification - Initiator IDi 35
|
||
Identification - Responder IDr 36
|
||
Certificate CERT 37
|
||
Certificate Request CERTREQ 38
|
||
Authentication AUTH 39
|
||
Nonce Ni, Nr 40
|
||
Notify N 41
|
||
Delete D 42
|
||
Vendor ID V 43
|
||
Traffic Selector - Initiator TSi 44
|
||
Traffic Selector - Responder TSr 45
|
||
Encrypted E 46
|
||
Configuration CP 47
|
||
Extensible Authentication EAP 48
|
||
RESERVED TO IANA 49-127
|
||
PRIVATE USE 128-255
|
||
|
||
(Payload type values 1-32 should not be assigned in the
|
||
future so that there is no overlap with the code assignments
|
||
for IKEv1.)
|
||
|
||
o Critical (1 bit) - MUST be set to zero if the sender wants the
|
||
recipient to skip this payload if it does not understand the
|
||
payload type code in the Next Payload field of the previous
|
||
payload. MUST be set to one if the sender wants the recipient to
|
||
reject this entire message if it does not understand the payload
|
||
type. MUST be ignored by the recipient if the recipient
|
||
understands the payload type code. MUST be set to zero for
|
||
payload types defined in this document. Note that the critical
|
||
bit applies to the current payload rather than the "next" payload
|
||
whose type code appears in the first octet. The reasoning behind
|
||
not setting the critical bit for payloads defined in this document
|
||
is that all implementations MUST understand all payload types
|
||
defined in this document and therefore must ignore the Critical
|
||
bit's value. Skipped payloads are expected to have valid Next
|
||
Payload and Payload Length fields.
|
||
|
||
o RESERVED (7 bits) - MUST be sent as zero; MUST be ignored on
|
||
receipt.
|
||
|
||
o Payload Length (2 octets) - Length in octets of the current
|
||
payload, including the generic payload header.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 62]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
{{ Clarif-7.10 }} Many payloads contain fields marked as "RESERVED".
|
||
Some payloads in IKEv2 (and historically in IKEv1) are not aligned to
|
||
4-octet boundaries.
|
||
|
||
3.3. Security Association Payload
|
||
|
||
The Security Association Payload, denoted SA in this memo, is used to
|
||
negotiate attributes of a security association. Assembly of Security
|
||
Association Payloads requires great peace of mind. An SA payload MAY
|
||
contain multiple proposals. If there is more than one, they MUST be
|
||
ordered from most preferred to least preferred. Each proposal
|
||
contains a single IPsec protocol (where a protocol is IKE, ESP, or
|
||
AH), each protocol MAY contain multiple transforms, and each
|
||
transform MAY contain multiple attributes. When parsing an SA, an
|
||
implementation MUST check that the total Payload Length is consistent
|
||
with the payload's internal lengths and counts. Proposals,
|
||
Transforms, and Attributes each have their own variable length
|
||
encodings. They are nested such that the Payload Length of an SA
|
||
includes the combined contents of the SA, Proposal, Transform, and
|
||
Attribute information. The length of a Proposal includes the lengths
|
||
of all Transforms and Attributes it contains. The length of a
|
||
Transform includes the lengths of all Attributes it contains.
|
||
|
||
The syntax of Security Associations, Proposals, Transforms, and
|
||
Attributes is based on ISAKMP; however the semantics are somewhat
|
||
different. The reason for the complexity and the hierarchy is to
|
||
allow for multiple possible combinations of algorithms to be encoded
|
||
in a single SA. Sometimes there is a choice of multiple algorithms,
|
||
whereas other times there is a combination of algorithms. For
|
||
example, an initiator might want to propose using ESP with either
|
||
(3DES and HMAC_MD5) or (AES and HMAC_SHA1).
|
||
|
||
One of the reasons the semantics of the SA payload has changed from
|
||
ISAKMP and IKEv1 is to make the encodings more compact in common
|
||
cases.
|
||
|
||
The Proposal structure contains within it a Proposal # and an IPsec
|
||
protocol ID. Each structure MUST have a proposal number one (1)
|
||
greater than the previous structure. The first Proposal in the
|
||
initiator's SA payload MUST have a Proposal # of one (1). A proposal
|
||
of AH or ESP would have two proposal structures, one for AH with
|
||
Proposal #1 and one for ESP with Proposal #2.
|
||
|
||
Each Proposal/Protocol structure is followed by one or more transform
|
||
structures. The number of different transforms is generally
|
||
determined by the Protocol. AH generally has two transforms:
|
||
Extended Sequence Numbers (ESN) and an integrity check algorithm.
|
||
ESP generally has three: ESN, an encryption algorithm and an
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 63]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
integrity check algorithm. IKE generally has four transforms: a
|
||
Diffie-Hellman group, an integrity check algorithm, a prf algorithm,
|
||
and an encryption algorithm. If an algorithm that combines
|
||
encryption and integrity protection is proposed, it MUST be proposed
|
||
as an encryption algorithm and an integrity protection algorithm MUST
|
||
NOT be proposed. For each Protocol, the set of permissible
|
||
transforms is assigned transform ID numbers, which appear in the
|
||
header of each transform.
|
||
|
||
If there are multiple transforms with the same Transform Type, the
|
||
proposal is an OR of those transforms. If there are multiple
|
||
Transforms with different Transform Types, the proposal is an AND of
|
||
the different groups. For example, to propose ESP with (3DES or AES-
|
||
CBC) and (HMAC_MD5 or HMAC_SHA), the ESP proposal would contain two
|
||
Transform Type 1 candidates (one for 3DES and one for AEC-CBC) and
|
||
two Transform Type 3 candidates (one for HMAC_MD5 and one for
|
||
HMAC_SHA). This effectively proposes four combinations of
|
||
algorithms. If the initiator wanted to propose only a subset of
|
||
those, for example (3DES and HMAC_MD5) or (IDEA and HMAC_SHA), there
|
||
is no way to encode that as multiple transforms within a single
|
||
Proposal. Instead, the initiator would have to construct two
|
||
different Proposals, each with two transforms.
|
||
|
||
A given transform MAY have one or more Attributes. Attributes are
|
||
necessary when the transform can be used in more than one way, as
|
||
when an encryption algorithm has a variable key size. The transform
|
||
would specify the algorithm and the attribute would specify the key
|
||
size. Most transforms do not have attributes. A transform MUST NOT
|
||
have multiple attributes of the same type. To propose alternate
|
||
values for an attribute (for example, multiple key sizes for the AES
|
||
encryption algorithm), and implementation MUST include multiple
|
||
Transforms with the same Transform Type each with a single Attribute.
|
||
|
||
Note that the semantics of Transforms and Attributes are quite
|
||
different from those in IKEv1. In IKEv1, a single Transform carried
|
||
multiple algorithms for a protocol with one carried in the Transform
|
||
and the others carried in the Attributes.
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ <Proposals> ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 64]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Figure 6: Security Association Payload
|
||
|
||
o Proposals (variable) - One or more proposal substructures.
|
||
|
||
The payload type for the Security Association Payload is thirty three
|
||
(33).
|
||
|
||
3.3.1. Proposal Substructure
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| 0 (last) or 2 | RESERVED | Proposal Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Proposal # | Protocol ID | SPI Size |# of Transforms|
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
~ SPI (variable) ~
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ <Transforms> ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 7: Proposal Substructure
|
||
|
||
o 0 (last) or 2 (more) (1 octet) - Specifies whether this is the
|
||
last Proposal Substructure in the SA. This syntax is inherited
|
||
from ISAKMP, but is unnecessary because the last Proposal could be
|
||
identified from the length of the SA. The value (2) corresponds
|
||
to a Payload Type of Proposal in IKEv1, and the first four octets
|
||
of the Proposal structure are designed to look somewhat like the
|
||
header of a Payload.
|
||
|
||
o RESERVED (1 octet) - MUST be sent as zero; MUST be ignored on
|
||
receipt.
|
||
|
||
o Proposal Length (2 octets) - Length of this proposal, including
|
||
all transforms and attributes that follow.
|
||
|
||
o Proposal # (1 octet) - When a proposal is made, the first proposal
|
||
in an SA payload MUST be #1, and subsequent proposals MUST be one
|
||
more than the previous proposal (indicating an OR of the two
|
||
proposals). When a proposal is accepted, the proposal number in
|
||
the SA payload MUST match the number on the proposal sent that was
|
||
accepted.
|
||
|
||
o Protocol ID (1 octet) - Specifies the IPsec protocol identifier
|
||
for the current negotiation. The defined values are:
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 65]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Protocol Protocol ID
|
||
-----------------------------------
|
||
RESERVED 0
|
||
IKE 1
|
||
AH 2
|
||
ESP 3
|
||
RESERVED TO IANA 4-200
|
||
PRIVATE USE 201-255
|
||
|
||
o SPI Size (1 octet) - For an initial IKE_SA negotiation, this field
|
||
MUST be zero; the SPI is obtained from the outer header. During
|
||
subsequent negotiations, it is equal to the size, in octets, of
|
||
the SPI of the corresponding protocol (8 for IKE, 4 for ESP and
|
||
AH).
|
||
|
||
o # of Transforms (1 octet) - Specifies the number of transforms in
|
||
this proposal.
|
||
|
||
o SPI (variable) - The sending entity's SPI. Even if the SPI Size
|
||
is not a multiple of 4 octets, there is no padding applied to the
|
||
payload. When the SPI Size field is zero, this field is not
|
||
present in the Security Association payload.
|
||
|
||
o Transforms (variable) - One or more transform substructures.
|
||
|
||
3.3.2. Transform Substructure
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| 0 (last) or 3 | RESERVED | Transform Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|Transform Type | RESERVED | Transform ID |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Transform Attributes ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 8: Transform Substructure
|
||
|
||
o 0 (last) or 3 (more) (1 octet) - Specifies whether this is the
|
||
last Transform Substructure in the Proposal. This syntax is
|
||
inherited from ISAKMP, but is unnecessary because the last
|
||
Proposal could be identified from the length of the SA. The value
|
||
(3) corresponds to a Payload Type of Transform in IKEv1, and the
|
||
first four octets of the Transform structure are designed to look
|
||
somewhat like the header of a Payload.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 66]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
o RESERVED - MUST be sent as zero; MUST be ignored on receipt.
|
||
|
||
o Transform Length - The length (in octets) of the Transform
|
||
Substructure including Header and Attributes.
|
||
|
||
o Transform Type (1 octet) - The type of transform being specified
|
||
in this transform. Different protocols support different
|
||
transform types. For some protocols, some of the transforms may
|
||
be optional. If a transform is optional and the initiator wishes
|
||
to propose that the transform be omitted, no transform of the
|
||
given type is included in the proposal. If the initiator wishes
|
||
to make use of the transform optional to the responder, it
|
||
includes a transform substructure with transform ID = 0 as one of
|
||
the options.
|
||
|
||
o Transform ID (2 octets) - The specific instance of the transform
|
||
type being proposed.
|
||
|
||
The tranform type values are:
|
||
|
||
Description Trans. Used In
|
||
Type
|
||
------------------------------------------------------------------
|
||
RESERVED 0
|
||
Encryption Algorithm (ENCR) 1 IKE and ESP
|
||
Pseudo-random Function (PRF) 2 IKE
|
||
Integrity Algorithm (INTEG) 3 IKE*, AH, optional in ESP
|
||
Diffie-Hellman Group (D-H) 4 IKE, optional in AH & ESP
|
||
Extended Sequence Numbers (ESN) 5 AH and ESP
|
||
RESERVED TO IANA 6-240
|
||
PRIVATE USE 241-255
|
||
|
||
(*) Negotiating an integrity algorithm is mandatory for the
|
||
Encrypted payload format specified in this document. Future
|
||
documents may specify additional formats based on authenticated
|
||
encryption, in which case a separate integrity algorithm is not
|
||
negotiated.
|
||
|
||
For Transform Type 1 (Encryption Algorithm), defined Transform IDs
|
||
are:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 67]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Name Number Defined In
|
||
---------------------------------------------------
|
||
RESERVED 0
|
||
ENCR_DES_IV64 1 (UNSPECIFIED)
|
||
ENCR_DES 2 (RFC2405), [DES]
|
||
ENCR_3DES 3 (RFC2451)
|
||
ENCR_RC5 4 (RFC2451)
|
||
ENCR_IDEA 5 (RFC2451), [IDEA]
|
||
ENCR_CAST 6 (RFC2451)
|
||
ENCR_BLOWFISH 7 (RFC2451)
|
||
ENCR_3IDEA 8 (UNSPECIFIED)
|
||
ENCR_DES_IV32 9 (UNSPECIFIED)
|
||
RESERVED 10
|
||
ENCR_NULL 11 (RFC2410)
|
||
ENCR_AES_CBC 12 (RFC3602)
|
||
ENCR_AES_CTR 13 (RFC3686)
|
||
RESERVED TO IANA 14-1023
|
||
PRIVATE USE 1024-65535
|
||
|
||
For Transform Type 2 (Pseudo-random Function), defined Transform IDs
|
||
are:
|
||
|
||
Name Number Defined In
|
||
------------------------------------------------------
|
||
RESERVED 0
|
||
PRF_HMAC_MD5 1 (RFC2104), [MD5]
|
||
PRF_HMAC_SHA1 2 (RFC2104), [SHA]
|
||
PRF_HMAC_TIGER 3 (UNSPECIFIED)
|
||
PRF_AES128_XCBC 4 (RFC4434)
|
||
RESERVED TO IANA 5-1023
|
||
PRIVATE USE 1024-65535
|
||
|
||
For Transform Type 3 (Integrity Algorithm), defined Transform IDs
|
||
are:
|
||
|
||
Name Number Defined In
|
||
----------------------------------------
|
||
NONE 0
|
||
AUTH_HMAC_MD5_96 1 (RFC2403)
|
||
AUTH_HMAC_SHA1_96 2 (RFC2404)
|
||
AUTH_DES_MAC 3 (UNSPECIFIED)
|
||
AUTH_KPDK_MD5 4 (UNSPECIFIED)
|
||
AUTH_AES_XCBC_96 5 (RFC3566)
|
||
RESERVED TO IANA 6-1023
|
||
PRIVATE USE 1024-65535
|
||
|
||
For Transform Type 4 (Diffie-Hellman Group), defined Transform IDs
|
||
are:
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 68]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Name Number Defined in
|
||
----------------------------------------
|
||
NONE 0
|
||
768 Bit MODP 1 Appendix B
|
||
1024 Bit MODP 2 Appendix B
|
||
RESERVED TO IANA 3-4
|
||
1536-bit MODP 5 [ADDGROUP]
|
||
RESERVED TO IANA 6-13
|
||
2048-bit MODP 14 [ADDGROUP]
|
||
3072-bit MODP 15 [ADDGROUP]
|
||
4096-bit MODP 16 [ADDGROUP]
|
||
6144-bit MODP 17 [ADDGROUP]
|
||
8192-bit MODP 18 [ADDGROUP]
|
||
RESERVED TO IANA 19-1023
|
||
PRIVATE USE 1024-65535
|
||
|
||
For Transform Type 5 (Extended Sequence Numbers), defined Transform
|
||
IDs are:
|
||
|
||
Name Number
|
||
--------------------------------------------
|
||
No Extended Sequence Numbers 0
|
||
Extended Sequence Numbers 1
|
||
RESERVED 2 - 65535
|
||
|
||
{{ Clarif-4.4 }} Note that an initiator who supports ESNs will
|
||
usually include two ESN transforms, with values "0" and "1", in its
|
||
proposals. A proposal containing a single ESN transform with value
|
||
"1" means that using normal (non-extended) sequence numbers is not
|
||
acceptable.
|
||
|
||
3.3.3. Valid Transform Types by Protocol
|
||
|
||
The number and type of transforms that accompany an SA payload are
|
||
dependent on the protocol in the SA itself. An SA payload proposing
|
||
the establishment of an SA has the following mandatory and optional
|
||
transform types. A compliant implementation MUST understand all
|
||
mandatory and optional types for each protocol it supports (though it
|
||
need not accept proposals with unacceptable suites). A proposal MAY
|
||
omit the optional types if the only value for them it will accept is
|
||
NONE.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 69]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Protocol Mandatory Types Optional Types
|
||
---------------------------------------------------
|
||
IKE ENCR, PRF, INTEG*, D-H
|
||
ESP ENCR, ESN INTEG, D-H
|
||
AH INTEG, ESN D-H
|
||
|
||
(*) Negotiating an integrity algorithm is mandatory for the
|
||
Encrypted payload format specified in this document. Future
|
||
documents may specify additional formats based on authenticated
|
||
encryption, in which case a separate integrity algorithm is not
|
||
negotiated.
|
||
|
||
3.3.4. Mandatory Transform IDs
|
||
|
||
The specification of suites that MUST and SHOULD be supported for
|
||
interoperability has been removed from this document because they are
|
||
likely to change more rapidly than this document evolves.
|
||
|
||
An important lesson learned from IKEv1 is that no system should only
|
||
implement the mandatory algorithms and expect them to be the best
|
||
choice for all customers. For example, at the time that this
|
||
document was written, many IKEv1 implementers were starting to
|
||
migrate to AES in Cipher Block Chaining (CBC) mode for Virtual
|
||
Private Network (VPN) applications. Many IPsec systems based on
|
||
IKEv2 will implement AES, additional Diffie-Hellman groups, and
|
||
additional hash algorithms, and some IPsec customers already require
|
||
these algorithms in addition to the ones listed above.
|
||
|
||
It is likely that IANA will add additional transforms in the future,
|
||
and some users may want to use private suites, especially for IKE
|
||
where implementations should be capable of supporting different
|
||
parameters, up to certain size limits. In support of this goal, all
|
||
implementations of IKEv2 SHOULD include a management facility that
|
||
allows specification (by a user or system administrator) of Diffie-
|
||
Hellman (DH) parameters (the generator, modulus, and exponent lengths
|
||
and values) for new DH groups. Implementations SHOULD provide a
|
||
management interface through which these parameters and the
|
||
associated transform IDs may be entered (by a user or system
|
||
administrator), to enable negotiating such groups.
|
||
|
||
All implementations of IKEv2 MUST include a management facility that
|
||
enables a user or system administrator to specify the suites that are
|
||
acceptable for use with IKE. Upon receipt of a payload with a set of
|
||
transform IDs, the implementation MUST compare the transmitted
|
||
transform IDs against those locally configured via the management
|
||
controls, to verify that the proposed suite is acceptable based on
|
||
local policy. The implementation MUST reject SA proposals that are
|
||
not authorized by these IKE suite controls. Note that cryptographic
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 70]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
suites that MUST be implemented need not be configured as acceptable
|
||
to local policy.
|
||
|
||
3.3.5. Transform Attributes
|
||
|
||
Each transform in a Security Association payload may include
|
||
attributes that modify or complete the specification of the
|
||
transform. The set of valid attributes depends on the transform.
|
||
Currently, only a single attribute type is defined: the Key Length
|
||
attribute is used by certain encryption transforms with variable-
|
||
length keys (see below for details).
|
||
|
||
The attributes are type/value pairs and are defined below.
|
||
Attributes can have a value with a fixed two-octet length or a
|
||
variable-length value. For the latter, the attribute is encoded as
|
||
type/length/value.
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|A| Attribute Type | AF=0 Attribute Length |
|
||
|F| | AF=1 Attribute Value |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| AF=0 Attribute Value |
|
||
| AF=1 Not Transmitted |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 9: Data Attributes
|
||
|
||
o Attribute Format (AF) (1 bit) - Indicates whether the data
|
||
attribute follow the Type/Length/Value (TLV) format or a shortened
|
||
Type/Value (TV) format. If the AF bit is zero (0), then the
|
||
attribute uses TLV format; if the AF bit is one (1), the TV format
|
||
(with two-byte value) is used.
|
||
|
||
o Attribute Type (15 bits) - Unique identifier for each type of
|
||
attribute (see below).
|
||
|
||
o Attribute Value (variable length) - Value of the Attribute
|
||
associated with the Attribute Type. If the AF bit is a zero (0),
|
||
this field has a variable length defined by the Attribute Length
|
||
field. If the AF bit is a one (1), the Attribute Value has a
|
||
length of 2 octets.
|
||
|
||
Note that the only currently defined attribute type (Key Length) is
|
||
fixed length; the variable-length encoding specification is included
|
||
only for future extensions. Attributes described as fixed length
|
||
MUST NOT be encoded using the variable-length encoding. Variable-
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 71]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
length attributes MUST NOT be encoded as fixed-length even if their
|
||
value can fit into two octets. NOTE: This is a change from IKEv1,
|
||
where increased flexibility may have simplified the composer of
|
||
messages but certainly complicated the parser.
|
||
|
||
Attribute Type Value Attribute Format
|
||
------------------------------------------------------------
|
||
RESERVED 0-13
|
||
Key Length (in bits) 14 TV
|
||
RESERVED 15-17
|
||
RESERVED TO IANA 18-16383
|
||
PRIVATE USE 16384-32767
|
||
|
||
Values 0-13 and 15-17 were used in a similar context in IKEv1, and
|
||
should not be assigned except to matching values.
|
||
|
||
The Key Length attribute specifies the key length in bits (MUST use
|
||
network byte order) for certain transforms as follows: {{ Clarif-7.11
|
||
}}
|
||
|
||
o The Key Length attribute MUST NOT be used with transforms that use
|
||
a fixed length key. This includes, e.g., ENCR_DES, ENCR_IDEA, and
|
||
all the Type 2 (Pseudo-random function) and Type 3 (Integrity
|
||
Algorithm) transforms specified in this document. It is
|
||
recommended that future Type 2 or 3 transforms do not use this
|
||
attribute.
|
||
|
||
o Some transforms specify that the Key Length attribute MUST be
|
||
always included (omitting the attribute is not allowed, and
|
||
proposals not containing it MUST be rejected). This includes,
|
||
e.g., ENCR_AES_CBC and ENCR_AES_CTR.
|
||
|
||
o Some transforms allow variable-length keys, but also specify a
|
||
default key length if the attribute is not included. These
|
||
transforms include, e.g., ENCR_RC5 and ENCR_BLOWFISH.
|
||
|
||
Implementation note: To further interoperability and to support
|
||
upgrading endpoints independently, implementers of this protocol
|
||
SHOULD accept values that they deem to supply greater security. For
|
||
instance, if a peer is configured to accept a variable-length cipher
|
||
with a key length of X bits and is offered that cipher with a larger
|
||
key length, the implementation SHOULD accept the offer if it supports
|
||
use of the longer key.
|
||
|
||
Support of this capability allows a responder to express a concept of
|
||
"at least" a certain level of security -- "a key length of _at least_
|
||
X bits for cipher Y". However, as the attribute is always returned
|
||
unchanged (see Section 3.3.6), an initiator willing to accept
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 72]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
multiple key lengths has to include multiple transforms with the same
|
||
Transform Type, each with different Key Length attribute.
|
||
|
||
3.3.6. Attribute Negotiation
|
||
|
||
During security association negotiation initiators present offers to
|
||
responders. Responders MUST select a single complete set of
|
||
parameters from the offers (or reject all offers if none are
|
||
acceptable). If there are multiple proposals, the responder MUST
|
||
choose a single proposal. If the selected proposal has multiple
|
||
Transforms with the same type, the responder MUST choose a single
|
||
one. Any attributes of a selected transform MUST be returned
|
||
unmodified. The initiator of an exchange MUST check that the
|
||
accepted offer is consistent with one of its proposals, and if not
|
||
that response MUST be rejected.
|
||
|
||
If the responder receives a proposal that contains a Transform Type
|
||
it does not understand, or a proposal that is missing a mandatory
|
||
Transform Type, it MUST consider this proposal unacceptable; however,
|
||
other proposals in the same SA payload are processed as usual.
|
||
Similarly, if the responder receives a transform that contains a
|
||
Transform Attribute it does not understand, it MUST consider this
|
||
transform unacceptable; other transforms with the same Transform Type
|
||
are processed as usual. This allows new Transform Types and
|
||
Transform Attributes to be defined in the future.
|
||
|
||
Negotiating Diffie-Hellman groups presents some special challenges.
|
||
SA offers include proposed attributes and a Diffie-Hellman public
|
||
number (KE) in the same message. If in the initial exchange the
|
||
initiator offers to use one of several Diffie-Hellman groups, it
|
||
SHOULD pick the one the responder is most likely to accept and
|
||
include a KE corresponding to that group. If the guess turns out to
|
||
be wrong, the responder will indicate the correct group in the
|
||
response and the initiator SHOULD pick an element of that group for
|
||
its KE value when retrying the first message. It SHOULD, however,
|
||
continue to propose its full supported set of groups in order to
|
||
prevent a man-in-the-middle downgrade attack.
|
||
|
||
3.4. Key Exchange Payload
|
||
|
||
The Key Exchange Payload, denoted KE in this memo, is used to
|
||
exchange Diffie-Hellman public numbers as part of a Diffie-Hellman
|
||
key exchange. The Key Exchange Payload consists of the IKE generic
|
||
payload header followed by the Diffie-Hellman public value itself.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 73]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| DH Group # | RESERVED |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Key Exchange Data ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 10: Key Exchange Payload Format
|
||
|
||
A key exchange payload is constructed by copying one's Diffie-Hellman
|
||
public value into the "Key Exchange Data" portion of the payload.
|
||
The length of the Diffie-Hellman public value MUST be equal to the
|
||
length of the prime modulus over which the exponentiation was
|
||
performed, prepending zero bits to the value if necessary.
|
||
|
||
The DH Group # identifies the Diffie-Hellman group in which the Key
|
||
Exchange Data was computed (see Section 3.3.2). If the selected
|
||
proposal uses a different Diffie-Hellman group (other than NONE), the
|
||
message MUST be rejected with a Notify payload of type
|
||
INVALID_KE_PAYLOAD.
|
||
|
||
The payload type for the Key Exchange payload is thirty four (34).
|
||
|
||
3.5. Identification Payloads
|
||
|
||
The Identification Payloads, denoted IDi and IDr in this memo, allow
|
||
peers to assert an identity to one another. This identity may be
|
||
used for policy lookup, but does not necessarily have to match
|
||
anything in the CERT payload; both fields may be used by an
|
||
implementation to perform access control decisions. {{ Clarif-7.1 }}
|
||
When using the ID_IPV4_ADDR/ID_IPV6_ADDR identity types in IDi/IDr
|
||
payloads, IKEv2 does not require this address to match the address in
|
||
the IP header of IKEv2 packets, or anything in the TSi/TSr payloads.
|
||
The contents of IDi/IDr is used purely to fetch the policy and
|
||
authentication data related to the other party.
|
||
|
||
NOTE: In IKEv1, two ID payloads were used in each direction to hold
|
||
Traffic Selector (TS) information for data passing over the SA. In
|
||
IKEv2, this information is carried in TS payloads (see Section 3.13).
|
||
|
||
The Identification Payload consists of the IKE generic payload header
|
||
followed by identification fields as follows:
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 74]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| ID Type | RESERVED |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Identification Data ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 11: Identification Payload Format
|
||
|
||
o ID Type (1 octet) - Specifies the type of Identification being
|
||
used.
|
||
|
||
o RESERVED - MUST be sent as zero; MUST be ignored on receipt.
|
||
|
||
o Identification Data (variable length) - Value, as indicated by the
|
||
Identification Type. The length of the Identification Data is
|
||
computed from the size in the ID payload header.
|
||
|
||
The payload types for the Identification Payload are thirty five (35)
|
||
for IDi and thirty six (36) for IDr.
|
||
|
||
The following table lists the assigned values for the Identification
|
||
Type field:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 75]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
ID Type Value
|
||
-------------------------------------------------------------------
|
||
RESERVED 0
|
||
|
||
ID_IPV4_ADDR 1
|
||
A single four (4) octet IPv4 address.
|
||
|
||
ID_FQDN 2
|
||
A fully-qualified domain name string. An example of a ID_FQDN
|
||
is, "example.com". The string MUST not contain any terminators
|
||
(e.g., NULL, CR, etc.). All characters in the ID_FQDN are ASCII;
|
||
for an "internationalized domain name", the syntax is as defined
|
||
in [IDNA], for example "xn--tmonesimerkki-bfbb.example.net".
|
||
|
||
ID_RFC822_ADDR 3
|
||
A fully-qualified RFC822 email address string, An example of a
|
||
ID_RFC822_ADDR is, "jsmith@example.com". The string MUST not
|
||
contain any terminators.
|
||
|
||
RESERVED TO IANA 4
|
||
|
||
ID_IPV6_ADDR 5
|
||
A single sixteen (16) octet IPv6 address.
|
||
|
||
RESERVED TO IANA 6 - 8
|
||
|
||
ID_DER_ASN1_DN 9
|
||
The binary Distinguished Encoding Rules (DER) encoding of an
|
||
ASN.1 X.500 Distinguished Name [X.501].
|
||
|
||
ID_DER_ASN1_GN 10
|
||
The binary DER encoding of an ASN.1 X.500 GeneralName [X.509].
|
||
|
||
ID_KEY_ID 11
|
||
An opaque octet stream which may be used to pass vendor-
|
||
specific information necessary to do certain proprietary
|
||
types of identification.
|
||
|
||
RESERVED TO IANA 12-200
|
||
|
||
PRIVATE USE 201-255
|
||
|
||
Two implementations will interoperate only if each can generate a
|
||
type of ID acceptable to the other. To assure maximum
|
||
interoperability, implementations MUST be configurable to send at
|
||
least one of ID_IPV4_ADDR, ID_FQDN, ID_RFC822_ADDR, or ID_KEY_ID, and
|
||
MUST be configurable to accept all of these types. Implementations
|
||
SHOULD be capable of generating and accepting all of these types.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 76]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
IPv6-capable implementations MUST additionally be configurable to
|
||
accept ID_IPV6_ADDR. IPv6-only implementations MAY be configurable
|
||
to send only ID_IPV6_ADDR.
|
||
|
||
{{ Clarif-3.4 }} EAP [EAP] does not mandate the use of any particular
|
||
type of identifier, but often EAP is used with Network Access
|
||
Identifiers (NAIs) defined in [NAI]. Although NAIs look a bit like
|
||
email addresses (e.g., "joe@example.com"), the syntax is not exactly
|
||
the same as the syntax of email address in [MAILFORMAT]. For those
|
||
NAIs that include the realm component, the ID_RFC822_ADDR
|
||
identification type SHOULD be used. Responder implementations should
|
||
not attempt to verify that the contents actually conform to the exact
|
||
syntax given in [MAILFORMAT], but instead should accept any
|
||
reasonable-looking NAI. For NAIs that do not include the realm
|
||
component,the ID_KEY_ID identification type SHOULD be used.
|
||
|
||
3.6. Certificate Payload
|
||
|
||
The Certificate Payload, denoted CERT in this memo, provides a means
|
||
to transport certificates or other authentication-related information
|
||
via IKE. Certificate payloads SHOULD be included in an exchange if
|
||
certificates are available to the sender unless the peer has
|
||
indicated an ability to retrieve this information from elsewhere
|
||
using an HTTP_CERT_LOOKUP_SUPPORTED Notify payload. Note that the
|
||
term "Certificate Payload" is somewhat misleading, because not all
|
||
authentication mechanisms use certificates and data other than
|
||
certificates may be passed in this payload.
|
||
|
||
The Certificate Payload is defined as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Cert Encoding | |
|
||
+-+-+-+-+-+-+-+-+ |
|
||
~ Certificate Data ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 12: Certificate Payload Format
|
||
|
||
o Certificate Encoding (1 octet) - This field indicates the type of
|
||
certificate or certificate-related information contained in the
|
||
Certificate Data field.
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 77]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Certificate Encoding Value
|
||
----------------------------------------------------
|
||
RESERVED 0
|
||
PKCS #7 wrapped X.509 certificate 1 UNSPECIFIED
|
||
PGP Certificate 2 UNSPECIFIED
|
||
DNS Signed Key 3 UNSPECIFIED
|
||
X.509 Certificate - Signature 4
|
||
Kerberos Token 6 UNSPECIFIED
|
||
Certificate Revocation List (CRL) 7
|
||
Authority Revocation List (ARL) 8
|
||
SPKI Certificate 9 UNSPECIFIED
|
||
X.509 Certificate - Attribute 10
|
||
Raw RSA Key 11
|
||
Hash and URL of X.509 certificate 12
|
||
Hash and URL of X.509 bundle 13
|
||
RESERVED to IANA 14 - 200
|
||
PRIVATE USE 201 - 255
|
||
|
||
o Certificate Data (variable length) - Actual encoding of
|
||
certificate data. The type of certificate is indicated by the
|
||
Certificate Encoding field.
|
||
|
||
The payload type for the Certificate Payload is thirty seven (37).
|
||
|
||
Specific syntax for some of the certificate type codes above is not
|
||
defined in this document. The types whose syntax is defined in this
|
||
document are:
|
||
|
||
o X.509 Certificate - Signature (4) contains a DER encoded X.509
|
||
certificate whose public key is used to validate the sender's AUTH
|
||
payload.
|
||
|
||
o Certificate Revocation List (7) contains a DER encoded X.509
|
||
certificate revocation list.
|
||
|
||
o {{ Added "DER-encoded RSAPublicKey structure" from Clarif-3.6 }}
|
||
Raw RSA Key (11) contains a PKCS #1 encoded RSA key, that is, a
|
||
DER-encoded RSAPublicKey structure (see [RSA] and [PKCS1]).
|
||
|
||
o Hash and URL encodings (12-13) allow IKE messages to remain short
|
||
by replacing long data structures with a 20 octet SHA-1 hash (see
|
||
[SHA]) of the replaced value followed by a variable-length URL
|
||
that resolves to the DER encoded data structure itself. This
|
||
improves efficiency when the endpoints have certificate data
|
||
cached and makes IKE less subject to denial of service attacks
|
||
that become easier to mount when IKE messages are large enough to
|
||
require IP fragmentation [DOSUDPPROT].
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 78]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Use the following ASN.1 definition for an X.509 bundle:
|
||
|
||
CertBundle
|
||
{ iso(1) identified-organization(3) dod(6) internet(1)
|
||
security(5) mechanisms(5) pkix(7) id-mod(0)
|
||
id-mod-cert-bundle(34) }
|
||
|
||
DEFINITIONS EXPLICIT TAGS ::=
|
||
BEGIN
|
||
|
||
IMPORTS
|
||
Certificate, CertificateList
|
||
FROM PKIX1Explicit88
|
||
{ iso(1) identified-organization(3) dod(6)
|
||
internet(1) security(5) mechanisms(5) pkix(7)
|
||
id-mod(0) id-pkix1-explicit(18) } ;
|
||
|
||
CertificateOrCRL ::= CHOICE {
|
||
cert [0] Certificate,
|
||
crl [1] CertificateList }
|
||
|
||
CertificateBundle ::= SEQUENCE OF CertificateOrCRL
|
||
|
||
END
|
||
|
||
Implementations MUST be capable of being configured to send and
|
||
accept up to four X.509 certificates in support of authentication,
|
||
and also MUST be capable of being configured to send and accept the
|
||
two Hash and URL formats (with HTTP URLs). Implementations SHOULD be
|
||
capable of being configured to send and accept Raw RSA keys. If
|
||
multiple certificates are sent, the first certificate MUST contain
|
||
the public key used to sign the AUTH payload. The other certificates
|
||
may be sent in any order.
|
||
|
||
3.7. Certificate Request Payload
|
||
|
||
The Certificate Request Payload, denoted CERTREQ in this memo,
|
||
provides a means to request preferred certificates via IKE and can
|
||
appear in the IKE_INIT_SA response and/or the IKE_AUTH request.
|
||
Certificate Request payloads MAY be included in an exchange when the
|
||
sender needs to get the certificate of the receiver. If multiple CAs
|
||
are trusted and the cert encoding does not allow a list, then
|
||
multiple Certificate Request payloads SHOULD be transmitted.
|
||
|
||
The Certificate Request Payload is defined as follows:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 79]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Cert Encoding | |
|
||
+-+-+-+-+-+-+-+-+ |
|
||
~ Certification Authority ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 13: Certificate Request Payload Format
|
||
|
||
o Certificate Encoding (1 octet) - Contains an encoding of the type
|
||
or format of certificate requested. Values are listed in
|
||
Section 3.6.
|
||
|
||
o Certification Authority (variable length) - Contains an encoding
|
||
of an acceptable certification authority for the type of
|
||
certificate requested.
|
||
|
||
The payload type for the Certificate Request Payload is thirty eight
|
||
(38).
|
||
|
||
The Certificate Encoding field has the same values as those defined
|
||
in Section 3.6. The Certification Authority field contains an
|
||
indicator of trusted authorities for this certificate type. The
|
||
Certification Authority value is a concatenated list of SHA-1 hashes
|
||
of the public keys of trusted Certification Authorities (CAs). Each
|
||
is encoded as the SHA-1 hash of the Subject Public Key Info element
|
||
(see section 4.1.2.7 of [PKIX]) from each Trust Anchor certificate.
|
||
The twenty-octet hashes are concatenated and included with no other
|
||
formatting.
|
||
|
||
{{ Clarif-3.6 }} The contents of the "Certification Authority" field
|
||
are defined only for X.509 certificates, which are types 4, 10, 12,
|
||
and 13. Other values SHOULD NOT be used until standards-track
|
||
specifications that specify their use are published.
|
||
|
||
Note that the term "Certificate Request" is somewhat misleading, in
|
||
that values other than certificates are defined in a "Certificate"
|
||
payload and requests for those values can be present in a Certificate
|
||
Request Payload. The syntax of the Certificate Request payload in
|
||
such cases is not defined in this document.
|
||
|
||
The Certificate Request Payload is processed by inspecting the "Cert
|
||
Encoding" field to determine whether the processor has any
|
||
certificates of this type. If so, the "Certification Authority"
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 80]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
field is inspected to determine if the processor has any certificates
|
||
that can be validated up to one of the specified certification
|
||
authorities. This can be a chain of certificates.
|
||
|
||
If an end-entity certificate exists that satisfies the criteria
|
||
specified in the CERTREQ, a certificate or certificate chain SHOULD
|
||
be sent back to the certificate requestor if the recipient of the
|
||
CERTREQ:
|
||
|
||
o is configured to use certificate authentication,
|
||
|
||
o is allowed to send a CERT payload,
|
||
|
||
o has matching CA trust policy governing the current negotiation,
|
||
and
|
||
|
||
o has at least one time-wise and usage appropriate end-entity
|
||
certificate chaining to a CA provided in the CERTREQ.
|
||
|
||
Certificate revocation checking must be considered during the
|
||
chaining process used to select a certificate. Note that even if two
|
||
peers are configured to use two different CAs, cross-certification
|
||
relationships should be supported by appropriate selection logic.
|
||
|
||
The intent is not to prevent communication through the strict
|
||
adherence of selection of a certificate based on CERTREQ, when an
|
||
alternate certificate could be selected by the sender that would
|
||
still enable the recipient to successfully validate and trust it
|
||
through trust conveyed by cross-certification, CRLs, or other out-of-
|
||
band configured means. Thus, the processing of a CERTREQ should be
|
||
seen as a suggestion for a certificate to select, not a mandated one.
|
||
If no certificates exist, then the CERTREQ is ignored. This is not
|
||
an error condition of the protocol. There may be cases where there
|
||
is a preferred CA sent in the CERTREQ, but an alternate might be
|
||
acceptable (perhaps after prompting a human operator).
|
||
|
||
{{ 3.10.1-16392 }} The HTTP_CERT_LOOKUP_SUPPORTED notification MAY be
|
||
included in any message that can include a CERTREQ payload and
|
||
indicates that the sender is capable of looking up certificates based
|
||
on an HTTP-based URL (and hence presumably would prefer to receive
|
||
certificate specifications in that format).
|
||
|
||
3.8. Authentication Payload
|
||
|
||
The Authentication Payload, denoted AUTH in this memo, contains data
|
||
used for authentication purposes. The syntax of the Authentication
|
||
data varies according to the Auth Method as specified below.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 81]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
The Authentication Payload is defined as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Auth Method | RESERVED |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Authentication Data ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 14: Authentication Payload Format
|
||
|
||
o Auth Method (1 octet) - Specifies the method of authentication
|
||
used. Values defined are:
|
||
|
||
* RSA Digital Signature (1) - Computed as specified in
|
||
Section 2.15 using an RSA private key with RSASSA-PKCS1-v1_5
|
||
signature scheme specified in [PKCS1] (implementors should note
|
||
that IKEv1 used a different method for RSA signatures) {{
|
||
Clarif-3.3 }}. {{ Clarif-3.2 }} To promote interoperability,
|
||
implementations that support this type SHOULD support
|
||
signatures that use SHA-1 as the hash function and SHOULD use
|
||
SHA-1 as the default hash function when generating signatures.
|
||
|
||
* Shared Key Message Integrity Code (2) - Computed as specified
|
||
in Section 2.15 using the shared key associated with the
|
||
identity in the ID payload and the negotiated prf function
|
||
|
||
* DSS Digital Signature (3) - Computed as specified in
|
||
Section 2.15 using a DSS private key (see [DSS]) over a SHA-1
|
||
hash.
|
||
|
||
* The values 0 and 4-200 are reserved to IANA. The values 201-
|
||
255 are available for private use.
|
||
|
||
o Authentication Data (variable length) - see Section 2.15.
|
||
|
||
The payload type for the Authentication Payload is thirty nine (39).
|
||
|
||
3.9. Nonce Payload
|
||
|
||
The Nonce Payload, denoted Ni and Nr in this memo for the initiator's
|
||
and responder's nonce respectively, contains random data used to
|
||
guarantee liveness during an exchange and protect against replay
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 82]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
attacks.
|
||
|
||
The Nonce Payload is defined as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Nonce Data ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 15: Nonce Payload Format
|
||
|
||
o Nonce Data (variable length) - Contains the random data generated
|
||
by the transmitting entity.
|
||
|
||
The payload type for the Nonce Payload is forty (40).
|
||
|
||
The size of a Nonce MUST be between 16 and 256 octets inclusive.
|
||
Nonce values MUST NOT be reused.
|
||
|
||
3.10. Notify Payload
|
||
|
||
The Notify Payload, denoted N in this document, is used to transmit
|
||
informational data, such as error conditions and state transitions,
|
||
to an IKE peer. A Notify Payload may appear in a response message
|
||
(usually specifying why a request was rejected), in an INFORMATIONAL
|
||
Exchange (to report an error not in an IKE request), or in any other
|
||
message to indicate sender capabilities or to modify the meaning of
|
||
the request.
|
||
|
||
The Notify Payload is defined as follows:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 83]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Protocol ID | SPI Size | Notify Message Type |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Security Parameter Index (SPI) ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Notification Data ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 16: Notify Payload Format
|
||
|
||
o Protocol ID (1 octet) - If this notification concerns an existing
|
||
SA whose SPI is given the SPI field, this field indicates the type
|
||
of that SA. For notifications concerning IPsec SAs this field
|
||
MUST contain either (2) to indicate AH or (3) to indicate ESP. {{
|
||
Clarif-7.8 }} Of the notifications defined in this document, the
|
||
SPI is included only with INVALID_SELECTORS and REKEY_SA. If the
|
||
SPI field is empty, this field MUST be sent as zero and MUST be
|
||
ignored on receipt. All other values for this field are reserved
|
||
to IANA for future assignment.
|
||
|
||
o SPI Size (1 octet) - Length in octets of the SPI as defined by the
|
||
IPsec protocol ID or zero if no SPI is applicable. For a
|
||
notification concerning the IKE_SA, the SPI Size MUST be zero.
|
||
|
||
o Notify Message Type (2 octets) - Specifies the type of
|
||
notification message.
|
||
|
||
o SPI (variable length) - Security Parameter Index.
|
||
|
||
o Notification Data (variable length) - Informational or error data
|
||
transmitted in addition to the Notify Message Type. Values for
|
||
this field are type specific (see below).
|
||
|
||
The payload type for the Notify Payload is forty one (41).
|
||
|
||
3.10.1. Notify Message Types
|
||
|
||
Notification information can be error messages specifying why an SA
|
||
could not be established. It can also be status data that a process
|
||
managing an SA database wishes to communicate with a peer process.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 84]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
The table below lists the Notification messages and their
|
||
corresponding values. The number of different error statuses was
|
||
greatly reduced from IKEv1 both for simplification and to avoid
|
||
giving configuration information to probers.
|
||
|
||
Types in the range 0 - 16383 are intended for reporting errors. An
|
||
implementation receiving a Notify payload with one of these types
|
||
that it does not recognize in a response MUST assume that the
|
||
corresponding request has failed entirely. {{ Demoted the SHOULD }}
|
||
Unrecognized error types in a request and status types in a request
|
||
or response MUST be ignored, and they should be logged.
|
||
|
||
Notify payloads with status types MAY be added to any message and
|
||
MUST be ignored if not recognized. They are intended to indicate
|
||
capabilities, and as part of SA negotiation are used to negotiate
|
||
non-cryptographic parameters.
|
||
|
||
NOTIFY messages: error types Value
|
||
-------------------------------------------------------------------
|
||
|
||
RESERVED 0
|
||
|
||
UNSUPPORTED_CRITICAL_PAYLOAD 1
|
||
See Section 2.5.
|
||
|
||
INVALID_IKE_SPI 4
|
||
See Section 2.21.
|
||
|
||
INVALID_MAJOR_VERSION 5
|
||
See Section 2.5.
|
||
|
||
INVALID_SYNTAX 7
|
||
Indicates the IKE message that was received was invalid because
|
||
some type, length, or value was out of range or because the
|
||
request was rejected for policy reasons. To avoid a denial of
|
||
service attack using forged messages, this status may only be
|
||
returned for and in an encrypted packet if the message ID and
|
||
cryptographic checksum were valid. To avoid leaking information
|
||
to someone probing a node, this status MUST be sent in response
|
||
to any error not covered by one of the other status types.
|
||
{{ Demoted the SHOULD }} To aid debugging, more detailed error
|
||
information should be written to a console or log.
|
||
|
||
INVALID_MESSAGE_ID 9
|
||
See Section 2.3.
|
||
|
||
INVALID_SPI 11
|
||
See Section 1.5.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 85]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
NO_PROPOSAL_CHOSEN 14
|
||
See Section 2.7.
|
||
|
||
INVALID_KE_PAYLOAD 17
|
||
See Section 1.3.
|
||
|
||
AUTHENTICATION_FAILED 24
|
||
Sent in the response to an IKE_AUTH message when for some reason
|
||
the authentication failed. There is no associated data.
|
||
|
||
SINGLE_PAIR_REQUIRED 34
|
||
See Section 2.9.
|
||
|
||
NO_ADDITIONAL_SAS 35
|
||
See Section 1.3.
|
||
|
||
INTERNAL_ADDRESS_FAILURE 36
|
||
See Section 3.15.4.
|
||
|
||
FAILED_CP_REQUIRED 37
|
||
See Section 2.19.
|
||
|
||
TS_UNACCEPTABLE 38
|
||
See Section 2.9.
|
||
|
||
INVALID_SELECTORS 39
|
||
MAY be sent in an IKE INFORMATIONAL exchange when a node receives
|
||
an ESP or AH packet whose selectors do not match those of the SA
|
||
on which it was delivered (and that caused the packet to be
|
||
dropped). The Notification Data contains the start of the
|
||
offending packet (as in ICMP messages) and the SPI field of the
|
||
notification is set to match the SPI of the IPsec SA.
|
||
|
||
RESERVED TO IANA 40-8191
|
||
|
||
PRIVATE USE 8192-16383
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 86]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
NOTIFY messages: status types Value
|
||
-------------------------------------------------------------------
|
||
|
||
INITIAL_CONTACT 16384
|
||
See Section 2.4.
|
||
|
||
SET_WINDOW_SIZE 16385
|
||
See Section 2.3.
|
||
|
||
ADDITIONAL_TS_POSSIBLE 16386
|
||
See Section 2.9.
|
||
|
||
IPCOMP_SUPPORTED 16387
|
||
See Section 2.22.
|
||
|
||
NAT_DETECTION_SOURCE_IP 16388
|
||
See Section 2.23.
|
||
|
||
NAT_DETECTION_DESTINATION_IP 16389
|
||
See Section 2.23.
|
||
|
||
COOKIE 16390
|
||
See Section 2.6.
|
||
|
||
USE_TRANSPORT_MODE 16391
|
||
See Section 1.3.1.
|
||
|
||
HTTP_CERT_LOOKUP_SUPPORTED 16392
|
||
See Section 3.6.
|
||
|
||
REKEY_SA 16393
|
||
See Section 1.3.3.
|
||
|
||
ESP_TFC_PADDING_NOT_SUPPORTED 16394
|
||
See Section 1.3.1.
|
||
|
||
NON_FIRST_FRAGMENTS_ALSO 16395
|
||
See Section 1.3.1.
|
||
|
||
RESERVED TO IANA 16396-40959
|
||
|
||
PRIVATE USE 40960-65535
|
||
|
||
3.11. Delete Payload
|
||
|
||
The Delete Payload, denoted D in this memo, contains a protocol
|
||
specific security association identifier that the sender has removed
|
||
from its security association database and is, therefore, no longer
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 87]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
valid. Figure 17 shows the format of the Delete Payload. It is
|
||
possible to send multiple SPIs in a Delete payload; however, each SPI
|
||
MUST be for the same protocol. Mixing of protocol identifiers MUST
|
||
NOT be performed in the Delete payload. It is permitted, however, to
|
||
include multiple Delete payloads in a single INFORMATIONAL exchange
|
||
where each Delete payload lists SPIs for a different protocol.
|
||
|
||
Deletion of the IKE_SA is indicated by a protocol ID of 1 (IKE) but
|
||
no SPIs. Deletion of a CHILD_SA, such as ESP or AH, will contain the
|
||
IPsec protocol ID of that protocol (2 for AH, 3 for ESP), and the SPI
|
||
is the SPI the sending endpoint would expect in inbound ESP or AH
|
||
packets.
|
||
|
||
The Delete Payload is defined as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Protocol ID | SPI Size | # of SPIs |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Security Parameter Index(es) (SPI) ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 17: Delete Payload Format
|
||
|
||
o Protocol ID (1 octet) - Must be 1 for an IKE_SA, 2 for AH, or 3
|
||
for ESP.
|
||
|
||
o SPI Size (1 octet) - Length in octets of the SPI as defined by the
|
||
protocol ID. It MUST be zero for IKE (SPI is in message header)
|
||
or four for AH and ESP.
|
||
|
||
o # of SPIs (2 octets) - The number of SPIs contained in the Delete
|
||
payload. The size of each SPI is defined by the SPI Size field.
|
||
|
||
o Security Parameter Index(es) (variable length) - Identifies the
|
||
specific security association(s) to delete. The length of this
|
||
field is determined by the SPI Size and # of SPIs fields.
|
||
|
||
The payload type for the Delete Payload is forty two (42).
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 88]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
3.12. Vendor ID Payload
|
||
|
||
The Vendor ID Payload, denoted V in this memo, contains a vendor
|
||
defined constant. The constant is used by vendors to identify and
|
||
recognize remote instances of their implementations. This mechanism
|
||
allows a vendor to experiment with new features while maintaining
|
||
backward compatibility.
|
||
|
||
A Vendor ID payload MAY announce that the sender is capable of
|
||
accepting certain extensions to the protocol, or it MAY simply
|
||
identify the implementation as an aid in debugging. A Vendor ID
|
||
payload MUST NOT change the interpretation of any information defined
|
||
in this specification (i.e., the critical bit MUST be set to 0).
|
||
Multiple Vendor ID payloads MAY be sent. An implementation is NOT
|
||
REQUIRED to send any Vendor ID payload at all.
|
||
|
||
A Vendor ID payload may be sent as part of any message. Reception of
|
||
a familiar Vendor ID payload allows an implementation to make use of
|
||
Private USE numbers described throughout this memo-- private
|
||
payloads, private exchanges, private notifications, etc. Unfamiliar
|
||
Vendor IDs MUST be ignored.
|
||
|
||
Writers of Internet-Drafts who wish to extend this protocol MUST
|
||
define a Vendor ID payload to announce the ability to implement the
|
||
extension in the Internet-Draft. It is expected that Internet-Drafts
|
||
that gain acceptance and are standardized will be given "magic
|
||
numbers" out of the Future Use range by IANA, and the requirement to
|
||
use a Vendor ID will go away.
|
||
|
||
The Vendor ID Payload fields are defined as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Vendor ID (VID) ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 18: Vendor ID Payload Format
|
||
|
||
o Vendor ID (variable length) - It is the responsibility of the
|
||
person choosing the Vendor ID to assure its uniqueness in spite of
|
||
the absence of any central registry for IDs. Good practice is to
|
||
include a company name, a person name, or some such. If you want
|
||
to show off, you might include the latitude and longitude and time
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 89]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
where you were when you chose the ID and some random input. A
|
||
message digest of a long unique string is preferable to the long
|
||
unique string itself.
|
||
|
||
The payload type for the Vendor ID Payload is forty three (43).
|
||
|
||
3.13. Traffic Selector Payload
|
||
|
||
The Traffic Selector Payload, denoted TS in this memo, allows peers
|
||
to identify packet flows for processing by IPsec security services.
|
||
The Traffic Selector Payload consists of the IKE generic payload
|
||
header followed by individual traffic selectors as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Number of TSs | RESERVED |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ <Traffic Selectors> ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 19: Traffic Selectors Payload Format
|
||
|
||
o Number of TSs (1 octet) - Number of traffic selectors being
|
||
provided.
|
||
|
||
o RESERVED - This field MUST be sent as zero and MUST be ignored on
|
||
receipt.
|
||
|
||
o Traffic Selectors (variable length) - One or more individual
|
||
traffic selectors.
|
||
|
||
The length of the Traffic Selector payload includes the TS header and
|
||
all the traffic selectors.
|
||
|
||
The payload type for the Traffic Selector payload is forty four (44)
|
||
for addresses at the initiator's end of the SA and forty five (45)
|
||
for addresses at the responder's end.
|
||
|
||
{{ Clarif-4.7 }} There is no requirement that TSi and TSr contain the
|
||
same number of individual traffic selectors. Thus, they are
|
||
interpreted as follows: a packet matches a given TSi/TSr if it
|
||
matches at least one of the individual selectors in TSi, and at least
|
||
one of the individual selectors in TSr.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 90]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
For instance, the following traffic selectors:
|
||
|
||
TSi = ((17, 100, 192.0.1.66-192.0.1.66),
|
||
(17, 200, 192.0.1.66-192.0.1.66))
|
||
TSr = ((17, 300, 0.0.0.0-255.255.255.255),
|
||
(17, 400, 0.0.0.0-255.255.255.255))
|
||
|
||
would match UDP packets from 192.0.1.66 to anywhere, with any of the
|
||
four combinations of source/destination ports (100,300), (100,400),
|
||
(200,300), and (200, 400).
|
||
|
||
Thus, some types of policies may require several CHILD_SA pairs. For
|
||
instance, a policy matching only source/destination ports (100,300)
|
||
and (200,400), but not the other two combinations, cannot be
|
||
negotiated as a single CHILD_SA pair.
|
||
|
||
3.13.1. Traffic Selector
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| TS Type |IP Protocol ID*| Selector Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Start Port* | End Port* |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Starting Address* ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Ending Address* ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 20: Traffic Selector
|
||
|
||
*Note: All fields other than TS Type and Selector Length depend on
|
||
the TS Type. The fields shown are for TS Types 7 and 8, the only two
|
||
values currently defined.
|
||
|
||
o TS Type (one octet) - Specifies the type of traffic selector.
|
||
|
||
o IP protocol ID (1 octet) - Value specifying an associated IP
|
||
protocol ID (e.g., UDP/TCP/ICMP). A value of zero means that the
|
||
protocol ID is not relevant to this traffic selector-- the SA can
|
||
carry all protocols.
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 91]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
o Selector Length - Specifies the length of this Traffic Selector
|
||
Substructure including the header.
|
||
|
||
o Start Port (2 octets) - Value specifying the smallest port number
|
||
allowed by this Traffic Selector. For protocols for which port is
|
||
undefined, or if all ports are allowed, this field MUST be zero.
|
||
For the ICMP protocol, the two one-octet fields Type and Code are
|
||
treated as a single 16-bit integer (with Type in the most
|
||
significant eight bits and Code in the least significant eight
|
||
bits) port number for the purposes of filtering based on this
|
||
field.
|
||
|
||
o End Port (2 octets) - Value specifying the largest port number
|
||
allowed by this Traffic Selector. For protocols for which port is
|
||
undefined, or if all ports are allowed, this field MUST be 65535.
|
||
For the ICMP protocol, the two one-octet fields Type and Code are
|
||
treated as a single 16-bit integer (with Type in the most
|
||
significant eight bits and Code in the least significant eight
|
||
bits) port number for the purposed of filtering based on this
|
||
field.
|
||
|
||
o Starting Address - The smallest address included in this Traffic
|
||
Selector (length determined by TS type).
|
||
|
||
o Ending Address - The largest address included in this Traffic
|
||
Selector (length determined by TS type).
|
||
|
||
Systems that are complying with [IPSECARCH] that wish to indicate
|
||
"ANY" ports MUST set the start port to 0 and the end port to 65535;
|
||
note that according to [IPSECARCH], "ANY" includes "OPAQUE". Systems
|
||
working with [IPSECARCH] that wish to indicate "OPAQUE" ports, but
|
||
not "ANY" ports, MUST set the start port to 65535 and the end port to
|
||
0.
|
||
|
||
{{ Added from Clarif-4.8 }} The traffic selector types 7 and 8 can
|
||
also refer to ICMP type and code fields. Note, however, that ICMP
|
||
packets do not have separate source and destination port fields. The
|
||
method for specifying the traffic selectors for ICMP is shown by
|
||
example in Section 4.4.1.3 of [IPSECARCH].
|
||
|
||
{{ Added from Clarif-4.9 }} Traffic selectors can use IP Protocol ID
|
||
135 to match the IPv6 mobility header [MIPV6]. This document does
|
||
not specify how to represent the "MH Type" field in traffic
|
||
selectors, although it is likely that a different document will
|
||
specify this in the future. Note that [IPSECARCH] says that the IPv6
|
||
mobility header (MH) message type is placed in the most significant
|
||
eight bits of the 16-bit local port selector. The direction
|
||
semantics of TSi/TSr port fields are the same as for ICMP.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 92]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
The following table lists the assigned values for the Traffic
|
||
Selector Type field and the corresponding Address Selector Data.
|
||
|
||
TS Type Value
|
||
-------------------------------------------------------------------
|
||
RESERVED 0-6
|
||
|
||
TS_IPV4_ADDR_RANGE 7
|
||
|
||
A range of IPv4 addresses, represented by two four-octet
|
||
values. The first value is the beginning IPv4 address
|
||
(inclusive) and the second value is the ending IPv4 address
|
||
(inclusive). All addresses falling between the two specified
|
||
addresses are considered to be within the list.
|
||
|
||
TS_IPV6_ADDR_RANGE 8
|
||
|
||
A range of IPv6 addresses, represented by two sixteen-octet
|
||
values. The first value is the beginning IPv6 address
|
||
(inclusive) and the second value is the ending IPv6 address
|
||
(inclusive). All addresses falling between the two specified
|
||
addresses are considered to be within the list.
|
||
|
||
RESERVED TO IANA 9-240
|
||
PRIVATE USE 241-255
|
||
|
||
3.14. Encrypted Payload
|
||
|
||
The Encrypted Payload, denoted SK{...} or E in this memo, contains
|
||
other payloads in encrypted form. The Encrypted Payload, if present
|
||
in a message, MUST be the last payload in the message. Often, it is
|
||
the only payload in the message.
|
||
|
||
The algorithms for encryption and integrity protection are negotiated
|
||
during IKE_SA setup, and the keys are computed as specified in
|
||
Section 2.14 and Section 2.18.
|
||
|
||
This document specifies the cryptographic processing of Encrypted
|
||
payloads using a block cipher in CBC mode and an integrity check
|
||
algorithm that computes a fixed-length checksum over a variable size
|
||
message. The design is modeled after the ESP algorithms described in
|
||
RFCs 2104 [HMAC], 4303 [ESP], and 2451 [ESPCBC]. This document
|
||
completely specifies the cryptographic processing of IKE data, but
|
||
those documents should be consulted for design rationale. Future
|
||
documents may specify the processing of Encrypted payloads for other
|
||
types of transforms, such as counter mode encryption and
|
||
authenticated encryption algorithms. Peers MUST NOT negotiate
|
||
transforms for which no such specification exists.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 93]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
The payload type for an Encrypted payload is forty six (46). The
|
||
Encrypted Payload consists of the IKE generic payload header followed
|
||
by individual fields as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Initialization Vector |
|
||
| (length is block size for encryption algorithm) |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
~ Encrypted IKE Payloads ~
|
||
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| | Padding (0-255 octets) |
|
||
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|
||
| | Pad Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
~ Integrity Checksum Data ~
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 21: Encrypted Payload Format
|
||
|
||
o Next Payload - The payload type of the first embedded payload.
|
||
Note that this is an exception in the standard header format,
|
||
since the Encrypted payload is the last payload in the message and
|
||
therefore the Next Payload field would normally be zero. But
|
||
because the content of this payload is embedded payloads and there
|
||
was no natural place to put the type of the first one, that type
|
||
is placed here.
|
||
|
||
o Payload Length - Includes the lengths of the header, IV, Encrypted
|
||
IKE Payloads, Padding, Pad Length, and Integrity Checksum Data.
|
||
|
||
o Initialization Vector - The length of the initialization vector
|
||
(IV) is equal to the block length of the underlying encryption
|
||
algorithm. Senders MUST select a new unpredictable IV for every
|
||
message; recipients MUST accept any value. The reader is
|
||
encouraged to consult [MODES] for advice on IV generation. In
|
||
particular, using the final ciphertext block of the previous
|
||
message is not considered unpredictable.
|
||
|
||
o IKE Payloads are as specified earlier in this section. This field
|
||
is encrypted with the negotiated cipher.
|
||
|
||
o Padding MAY contain any value chosen by the sender, and MUST have
|
||
a length that makes the combination of the Payloads, the Padding,
|
||
and the Pad Length to be a multiple of the encryption block size.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 94]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
This field is encrypted with the negotiated cipher.
|
||
|
||
o Pad Length is the length of the Padding field. The sender SHOULD
|
||
set the Pad Length to the minimum value that makes the combination
|
||
of the Payloads, the Padding, and the Pad Length a multiple of the
|
||
block size, but the recipient MUST accept any length that results
|
||
in proper alignment. This field is encrypted with the negotiated
|
||
cipher.
|
||
|
||
o Integrity Checksum Data is the cryptographic checksum of the
|
||
entire message starting with the Fixed IKE Header through the Pad
|
||
Length. The checksum MUST be computed over the encrypted message.
|
||
Its length is determined by the integrity algorithm negotiated.
|
||
|
||
3.15. Configuration Payload
|
||
|
||
The Configuration payload, denoted CP in this document, is used to
|
||
exchange configuration information between IKE peers. The exchange
|
||
is for an IRAC to request an internal IP address from an IRAS and to
|
||
exchange other information of the sort that one would acquire with
|
||
Dynamic Host Configuration Protocol (DHCP) if the IRAC were directly
|
||
connected to a LAN.
|
||
|
||
The Configuration Payload is defined as follows:
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| CFG Type | RESERVED |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Configuration Attributes ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 22: Configuration Payload Format
|
||
|
||
The payload type for the Configuration Payload is forty seven (47).
|
||
|
||
o CFG Type (1 octet) - The type of exchange represented by the
|
||
Configuration Attributes.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 95]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
CFG Type Value
|
||
--------------------------
|
||
RESERVED 0
|
||
CFG_REQUEST 1
|
||
CFG_REPLY 2
|
||
CFG_SET 3
|
||
CFG_ACK 4
|
||
RESERVED TO IANA 5-127
|
||
PRIVATE USE 128-255
|
||
|
||
o RESERVED (3 octets) - MUST be sent as zero; MUST be ignored on
|
||
receipt.
|
||
|
||
o Configuration Attributes (variable length) - These are type length
|
||
values specific to the Configuration Payload and are defined
|
||
below. There may be zero or more Configuration Attributes in this
|
||
payload.
|
||
|
||
3.15.1. Configuration Attributes
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|R| Attribute Type | Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ Value ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 23: Configuration Attribute Format
|
||
|
||
o Reserved (1 bit) - This bit MUST be set to zero and MUST be
|
||
ignored on receipt.
|
||
|
||
o Attribute Type (15 bits) - A unique identifier for each of the
|
||
Configuration Attribute Types.
|
||
|
||
o Length (2 octets) - Length in octets of Value.
|
||
|
||
o Value (0 or more octets) - The variable-length value of this
|
||
Configuration Attribute. The following attribute types have been
|
||
defined:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 96]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Multi-
|
||
Attribute Type Value Valued Length
|
||
-------------------------------------------------------
|
||
RESERVED 0
|
||
INTERNAL_IP4_ADDRESS 1 YES* 0 or 4 octets
|
||
INTERNAL_IP4_NETMASK 2 NO 0 or 4 octets
|
||
INTERNAL_IP4_DNS 3 YES 0 or 4 octets
|
||
INTERNAL_IP4_NBNS 4 YES 0 or 4 octets
|
||
RESERVED 5
|
||
INTERNAL_IP4_DHCP 6 YES 0 or 4 octets
|
||
APPLICATION_VERSION 7 NO 0 or more
|
||
INTERNAL_IP6_ADDRESS 8 YES* 0 or 17 octets
|
||
RESERVED 9
|
||
INTERNAL_IP6_DNS 10 YES 0 or 16 octets
|
||
INTERNAL_IP6_NBNS 11 YES 0 or 16 octets
|
||
INTERNAL_IP6_DHCP 12 YES 0 or 16 octets
|
||
INTERNAL_IP4_SUBNET 13 YES 0 or 8 octets
|
||
SUPPORTED_ATTRIBUTES 14 NO Multiple of 2
|
||
INTERNAL_IP6_SUBNET 15 YES 17 octets
|
||
RESERVED TO IANA 16-16383
|
||
PRIVATE USE 16384-32767
|
||
|
||
* These attributes may be multi-valued on return only if
|
||
multiple values were requested.
|
||
|
||
o INTERNAL_IP4_ADDRESS, INTERNAL_IP6_ADDRESS - An address on the
|
||
internal network, sometimes called a red node address or private
|
||
address and MAY be a private address on the Internet. {{
|
||
Clarif-6.2}} In a request message, the address specified is a
|
||
requested address (or a zero-length address if no specific address
|
||
is requested). If a specific address is requested, it likely
|
||
indicates that a previous connection existed with this address and
|
||
the requestor would like to reuse that address. With IPv6, a
|
||
requestor MAY supply the low-order address octets it wants to use.
|
||
Multiple internal addresses MAY be requested by requesting
|
||
multiple internal address attributes. The responder MAY only send
|
||
up to the number of addresses requested. The INTERNAL_IP6_ADDRESS
|
||
is made up of two fields: the first is a 16-octet IPv6 address,
|
||
and the second is a one-octet prefix-length as defined in
|
||
[ADDRIPV6]. The requested address is valid until there are no
|
||
IKE_SAs between the peers.
|
||
|
||
o INTERNAL_IP4_NETMASK - The internal network's netmask. Only one
|
||
netmask is allowed in the request and reply messages (e.g.,
|
||
255.255.255.0), and it MUST be used only with an
|
||
INTERNAL_IP4_ADDRESS attribute. {{ Clarif-6.4 }}
|
||
INTERNAL_IP4_NETMASK in a CFG_REPLY means roughly the same thing
|
||
as INTERNAL_IP4_SUBNET containing the same information ("send
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 97]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
traffic to these addresses through me"), but also implies a link
|
||
boundary. For instance, the client could use its own address and
|
||
the netmask to calculate the broadcast address of the link. An
|
||
empty INTERNAL_IP4_NETMASK attribute can be included in a
|
||
CFG_REQUEST to request this information (although the gateway can
|
||
send the information even when not requested). Non-empty values
|
||
for this attribute in a CFG_REQUEST do not make sense and thus
|
||
MUST NOT be included.
|
||
|
||
o INTERNAL_IP4_DNS, INTERNAL_IP6_DNS - Specifies an address of a DNS
|
||
server within the network. Multiple DNS servers MAY be requested.
|
||
The responder MAY respond with zero or more DNS server attributes.
|
||
|
||
o INTERNAL_IP4_NBNS - Specifies an address of a NetBios Name Server
|
||
(WINS) within the network. Multiple NBNS servers MAY be
|
||
requested. The responder MAY respond with zero or more NBNS
|
||
server attributes.
|
||
|
||
o INTERNAL_IP6_NBNS - {{ Clarif-6.6 }} NetBIOS is not defined for
|
||
IPv6; therefore, INTERNAL_IP6_NBNS is also unspecified and is only
|
||
retained for compatibility with RFC 4306.
|
||
|
||
o INTERNAL_IP4_DHCP, INTERNAL_IP6_DHCP - Instructs the host to send
|
||
any internal DHCP requests to the address contained within the
|
||
attribute. Multiple DHCP servers MAY be requested. The responder
|
||
MAY respond with zero or more DHCP server attributes.
|
||
|
||
o APPLICATION_VERSION - The version or application information of
|
||
the IPsec host. This is a string of printable ASCII characters
|
||
that is NOT null terminated.
|
||
|
||
o INTERNAL_IP4_SUBNET - The protected sub-networks that this edge-
|
||
device protects. This attribute is made up of two fields: the
|
||
first being an IP address and the second being a netmask.
|
||
Multiple sub-networks MAY be requested. The responder MAY respond
|
||
with zero or more sub-network attributes.
|
||
|
||
o SUPPORTED_ATTRIBUTES - When used within a Request, this attribute
|
||
MUST be zero-length and specifies a query to the responder to
|
||
reply back with all of the attributes that it supports. The
|
||
response contains an attribute that contains a set of attribute
|
||
identifiers each in 2 octets. The length divided by 2 (octets)
|
||
would state the number of supported attributes contained in the
|
||
response.
|
||
|
||
o INTERNAL_IP6_SUBNET - The protected sub-networks that this edge-
|
||
device protects. This attribute is made up of two fields: the
|
||
first is a 16-octet IPv6 address, and the second is a one-octet
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 98]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
prefix-length as defined in [ADDRIPV6]. Multiple sub-networks MAY
|
||
be requested. The responder MAY respond with zero or more sub-
|
||
network attributes.
|
||
|
||
Note that no recommendations are made in this document as to how an
|
||
implementation actually figures out what information to send in a
|
||
reply. That is, we do not recommend any specific method of an IRAS
|
||
determining which DNS server should be returned to a requesting IRAC.
|
||
|
||
3.15.2. Meaning of INTERNAL_IP4_SUBNET/INTERNAL_IP6_SUBNET
|
||
|
||
{{ Section added based on Clarif-6.3 }}
|
||
|
||
INTERNAL_IP4/6_SUBNET attributes can indicate additional subnets,
|
||
ones that need one or more separate SAs, that can be reached through
|
||
the gateway that announces the attributes. INTERNAL_IP4/6_SUBNET
|
||
attributes may also express the gateway's policy about what traffic
|
||
should be sent through the gateway; the client can choose whether
|
||
other traffic (covered by TSr, but not in INTERNAL_IP4/6_SUBNET) is
|
||
sent through the gateway or directly to the destination. Thus,
|
||
traffic to the addresses listed in the INTERNAL_IP4/6_SUBNET
|
||
attributes should be sent through the gateway that announces the
|
||
attributes. If there are no existing IPsec SAs whose traffic
|
||
selectors cover the address in question, new SAs need to be created.
|
||
|
||
For instance, if there are two subnets, 192.0.1.0/26 and
|
||
192.0.2.0/24, and the client's request contains the following:
|
||
|
||
CP(CFG_REQUEST) =
|
||
INTERNAL_IP4_ADDRESS()
|
||
TSi = (0, 0-65535, 0.0.0.0-255.255.255.255)
|
||
TSr = (0, 0-65535, 0.0.0.0-255.255.255.255)
|
||
|
||
then a valid response could be the following (in which TSr and
|
||
INTERNAL_IP4_SUBNET contain the same information):
|
||
|
||
CP(CFG_REPLY) =
|
||
INTERNAL_IP4_ADDRESS(192.0.1.234)
|
||
INTERNAL_IP4_SUBNET(192.0.1.0/255.255.255.192)
|
||
INTERNAL_IP4_SUBNET(192.0.2.0/255.255.255.0)
|
||
TSi = (0, 0-65535, 192.0.1.234-192.0.1.234)
|
||
TSr = ((0, 0-65535, 192.0.1.0-192.0.1.63),
|
||
(0, 0-65535, 192.0.2.0-192.0.2.255))
|
||
|
||
In these cases, the INTERNAL_IP4_SUBNET does not really carry any
|
||
useful information.
|
||
|
||
A different possible reply would have been this:
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 99]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
CP(CFG_REPLY) =
|
||
INTERNAL_IP4_ADDRESS(192.0.1.234)
|
||
INTERNAL_IP4_SUBNET(192.0.1.0/255.255.255.192)
|
||
INTERNAL_IP4_SUBNET(192.0.2.0/255.255.255.0)
|
||
TSi = (0, 0-65535, 192.0.1.234-192.0.1.234)
|
||
TSr = (0, 0-65535, 0.0.0.0-255.255.255.255)
|
||
|
||
That reply would mean that the client can send all its traffic
|
||
through the gateway, but the gateway does not mind if the client
|
||
sends traffic not included by INTERNAL_IP4_SUBNET directly to the
|
||
destination (without going through the gateway).
|
||
|
||
A different situation arises if the gateway has a policy that
|
||
requires the traffic for the two subnets to be carried in separate
|
||
SAs. Then a response like this would indicate to the client that if
|
||
it wants access to the second subnet, it needs to create a separate
|
||
SA:
|
||
|
||
CP(CFG_REPLY) =
|
||
INTERNAL_IP4_ADDRESS(192.0.1.234)
|
||
INTERNAL_IP4_SUBNET(192.0.1.0/255.255.255.192)
|
||
INTERNAL_IP4_SUBNET(192.0.2.0/255.255.255.0)
|
||
TSi = (0, 0-65535, 192.0.1.234-192.0.1.234)
|
||
TSr = (0, 0-65535, 192.0.1.0-192.0.1.63)
|
||
|
||
INTERNAL_IP4_SUBNET can also be useful if the client's TSr included
|
||
only part of the address space. For instance, if the client requests
|
||
the following:
|
||
|
||
CP(CFG_REQUEST) =
|
||
INTERNAL_IP4_ADDRESS()
|
||
TSi = (0, 0-65535, 0.0.0.0-255.255.255.255)
|
||
TSr = (0, 0-65535, 192.0.2.155-192.0.2.155)
|
||
|
||
then the gateway's reply might be:
|
||
|
||
CP(CFG_REPLY) =
|
||
INTERNAL_IP4_ADDRESS(192.0.1.234)
|
||
INTERNAL_IP4_SUBNET(192.0.1.0/255.255.255.192)
|
||
INTERNAL_IP4_SUBNET(192.0.2.0/255.255.255.0)
|
||
TSi = (0, 0-65535, 192.0.1.234-192.0.1.234)
|
||
TSr = (0, 0-65535, 192.0.2.155-192.0.2.155)
|
||
|
||
Because the meaning of INTERNAL_IP4_SUBNET/INTERNAL_IP6_SUBNET is in
|
||
CFG_REQUESTs is unclear, they cannot be used reliably in
|
||
CFG_REQUESTs.
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 100]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
3.15.3. Configuration payloads for IPv6
|
||
|
||
{{ Added this section from Clarif-6.5 }}
|
||
|
||
The configuration payloads for IPv6 are based on the corresponding
|
||
IPv4 payloads, and do not fully follow the "normal IPv6 way of doing
|
||
things". In particular, IPv6 stateless autoconfiguration or router
|
||
advertisement messages are not used; neither is neighbor discovery.
|
||
|
||
A client can be assigned an IPv6 address using the
|
||
INTERNAL_IP6_ADDRESS configuration payload. A minimal exchange might
|
||
look like this:
|
||
|
||
CP(CFG_REQUEST) =
|
||
INTERNAL_IP6_ADDRESS()
|
||
INTERNAL_IP6_DNS()
|
||
TSi = (0, 0-65535, :: - FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF)
|
||
TSr = (0, 0-65535, :: - FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF)
|
||
|
||
CP(CFG_REPLY) =
|
||
INTERNAL_IP6_ADDRESS(2001:DB8:0:1:2:3:4:5/64)
|
||
INTERNAL_IP6_DNS(2001:DB8:99:88:77:66:55:44)
|
||
TSi = (0, 0-65535, 2001:DB8:0:1:2:3:4:5 - 2001:DB8:0:1:2:3:4:5)
|
||
TSr = (0, 0-65535, :: - FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF)
|
||
|
||
The client MAY send a non-empty INTERNAL_IP6_ADDRESS attribute in the
|
||
CFG_REQUEST to request a specific address or interface identifier.
|
||
The gateway first checks if the specified address is acceptable, and
|
||
if it is, returns that one. If the address was not acceptable, the
|
||
gateway attempts to use the interface identifier with some other
|
||
prefix; if even that fails, the gateway selects another interface
|
||
identifier.
|
||
|
||
The INTERNAL_IP6_ADDRESS attribute also contains a prefix length
|
||
field. When used in a CFG_REPLY, this corresponds to the
|
||
INTERNAL_IP4_NETMASK attribute in the IPv4 case.
|
||
|
||
Although this approach to configuring IPv6 addresses is reasonably
|
||
simple, it has some limitations. IPsec tunnels configured using
|
||
IKEv2 are not fully-featured "interfaces" in the IPv6 addressing
|
||
architecture sense [IPV6ADDR]. In particular, they do not
|
||
necessarily have link-local addresses, and this may complicate the
|
||
use of protocols that assume them, such as [MLDV2].
|
||
|
||
3.15.4. Address Assignment Failures
|
||
|
||
{{ Added this section from Clarif-6.8 }}
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 101]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
If the responder encounters an error while attempting to assign an IP
|
||
address to the initiator during the processing of a Configuration
|
||
Payload, it responds with an INTERNAL_ADDRESS_FAILURE notification.
|
||
{{ 3.10.1-36 }} If this error is generated within an IKE_AUTH
|
||
exchange, no CHILD_SA will be created. However, there are some more
|
||
complex error cases.
|
||
|
||
If the responder does not support configuration payloads at all, it
|
||
can simply ignore all configuration payloads. This type of
|
||
implementation never sends INTERNAL_ADDRESS_FAILURE notifications.
|
||
If the initiator requires the assignment of an IP address, it will
|
||
treat a response without CFG_REPLY as an error.
|
||
|
||
The initiator may request a particular type of address (IPv4 or IPv6)
|
||
that the responder does not support, even though the responder
|
||
supports configuration payloads. In this case, the responder simply
|
||
ignores the type of address it does not support and processes the
|
||
rest of the request as usual.
|
||
|
||
If the initiator requests multiple addresses of a type that the
|
||
responder supports, and some (but not all) of the requests fail, the
|
||
responder replies with the successful addresses only. The responder
|
||
sends INTERNAL_ADDRESS_FAILURE only if no addresses can be assigned.
|
||
|
||
3.16. Extensible Authentication Protocol (EAP) Payload
|
||
|
||
The Extensible Authentication Protocol Payload, denoted EAP in this
|
||
memo, allows IKE_SAs to be authenticated using the protocol defined
|
||
in RFC 3748 [EAP] and subsequent extensions to that protocol. The
|
||
full set of acceptable values for the payload is defined elsewhere,
|
||
but a short summary of RFC 3748 is included here to make this
|
||
document stand alone in the common cases.
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Next Payload |C| RESERVED | Payload Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| |
|
||
~ EAP Message ~
|
||
| |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
Figure 24: EAP Payload Format
|
||
|
||
The payload type for an EAP Payload is forty eight (48).
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 102]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1 2 3
|
||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Code | Identifier | Length |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Type | Type_Data...
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|
||
|
||
Figure 25: EAP Message Format
|
||
|
||
o Code (1 octet) indicates whether this message is a Request (1),
|
||
Response (2), Success (3), or Failure (4).
|
||
|
||
o Identifier (1 octet) is used in PPP to distinguish replayed
|
||
messages from repeated ones. Since in IKE, EAP runs over a
|
||
reliable protocol, it serves no function here. In a response
|
||
message, this octet MUST be set to match the identifier in the
|
||
corresponding request. In other messages, this field MAY be set
|
||
to any value.
|
||
|
||
o Length (2 octets) is the length of the EAP message and MUST be
|
||
four less than the Payload Length of the encapsulating payload.
|
||
|
||
o Type (1 octet) is present only if the Code field is Request (1) or
|
||
Response (2). For other codes, the EAP message length MUST be
|
||
four octets and the Type and Type_Data fields MUST NOT be present.
|
||
In a Request (1) message, Type indicates the data being requested.
|
||
In a Response (2) message, Type MUST either be Nak or match the
|
||
type of the data requested. The following types are defined in
|
||
RFC 3748:
|
||
|
||
1 Identity
|
||
2 Notification
|
||
3 Nak (Response Only)
|
||
4 MD5-Challenge
|
||
5 One-Time Password (OTP)
|
||
6 Generic Token Card
|
||
|
||
o Type_Data (Variable Length) varies with the Type of Request and
|
||
the associated Response. For the documentation of the EAP
|
||
methods, see [EAP].
|
||
|
||
{{ Demoted the SHOULD NOT and SHOULD }} Note that since IKE passes an
|
||
indication of initiator identity in message 3 of the protocol, the
|
||
responder should not send EAP Identity requests. The initiator may,
|
||
however, respond to such requests if it receives them.
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 103]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
4. Conformance Requirements
|
||
|
||
In order to assure that all implementations of IKEv2 can
|
||
interoperate, there are "MUST support" requirements in addition to
|
||
those listed elsewhere. Of course, IKEv2 is a security protocol, and
|
||
one of its major functions is to allow only authorized parties to
|
||
successfully complete establishment of SAs. So a particular
|
||
implementation may be configured with any of a number of restrictions
|
||
concerning algorithms and trusted authorities that will prevent
|
||
universal interoperability.
|
||
|
||
IKEv2 is designed to permit minimal implementations that can
|
||
interoperate with all compliant implementations. There are a series
|
||
of optional features that can easily be ignored by a particular
|
||
implementation if it does not support that feature. Those features
|
||
include:
|
||
|
||
o Ability to negotiate SAs through a NAT and tunnel the resulting
|
||
ESP SA over UDP.
|
||
|
||
o Ability to request (and respond to a request for) a temporary IP
|
||
address on the remote end of a tunnel.
|
||
|
||
o Ability to support various types of legacy authentication.
|
||
|
||
o Ability to support window sizes greater than one.
|
||
|
||
o Ability to establish multiple ESP and/or AH SAs within a single
|
||
IKE_SA.
|
||
|
||
o Ability to rekey SAs.
|
||
|
||
To assure interoperability, all implementations MUST be capable of
|
||
parsing all payload types (if only to skip over them) and to ignore
|
||
payload types that it does not support unless the critical bit is set
|
||
in the payload header. If the critical bit is set in an unsupported
|
||
payload header, all implementations MUST reject the messages
|
||
containing those payloads.
|
||
|
||
Every implementation MUST be capable of doing four-message
|
||
IKE_SA_INIT and IKE_AUTH exchanges establishing two SAs (one for IKE,
|
||
one for ESP and/or AH). Implementations MAY be initiate-only or
|
||
respond-only if appropriate for their platform. Every implementation
|
||
MUST be capable of responding to an INFORMATIONAL exchange, but a
|
||
minimal implementation MAY respond to any INFORMATIONAL message with
|
||
an empty INFORMATIONAL reply (note that within the context of an
|
||
IKE_SA, an "empty" message consists of an IKE header followed by an
|
||
Encrypted payload with no payloads contained in it). A minimal
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 104]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
implementation MAY support the CREATE_CHILD_SA exchange only in so
|
||
far as to recognize requests and reject them with a Notify payload of
|
||
type NO_ADDITIONAL_SAS. A minimal implementation need not be able to
|
||
initiate CREATE_CHILD_SA or INFORMATIONAL exchanges. When an SA
|
||
expires (based on locally configured values of either lifetime or
|
||
octets passed), and implementation MAY either try to renew it with a
|
||
CREATE_CHILD_SA exchange or it MAY delete (close) the old SA and
|
||
create a new one. If the responder rejects the CREATE_CHILD_SA
|
||
request with a NO_ADDITIONAL_SAS notification, the implementation
|
||
MUST be capable of instead deleting the old SA and creating a new
|
||
one.
|
||
|
||
Implementations are not required to support requesting temporary IP
|
||
addresses or responding to such requests. If an implementation does
|
||
support issuing such requests, it MUST include a CP payload in
|
||
message 3 containing at least a field of type INTERNAL_IP4_ADDRESS or
|
||
INTERNAL_IP6_ADDRESS. All other fields are optional. If an
|
||
implementation supports responding to such requests, it MUST parse
|
||
the CP payload of type CFG_REQUEST in message 3 and recognize a field
|
||
of type INTERNAL_IP4_ADDRESS or INTERNAL_IP6_ADDRESS. If it supports
|
||
leasing an address of the appropriate type, it MUST return a CP
|
||
payload of type CFG_REPLY containing an address of the requested
|
||
type. {{ Demoted the SHOULD }} The responder may include any other
|
||
related attributes.
|
||
|
||
A minimal IPv4 responder implementation will ignore the contents of
|
||
the CP payload except to determine that it includes an
|
||
INTERNAL_IP4_ADDRESS attribute and will respond with the address and
|
||
other related attributes regardless of whether the initiator
|
||
requested them.
|
||
|
||
A minimal IPv4 initiator will generate a CP payload containing only
|
||
an INTERNAL_IP4_ADDRESS attribute and will parse the response
|
||
ignoring attributes it does not know how to use.
|
||
|
||
For an implementation to be called conforming to this specification,
|
||
it MUST be possible to configure it to accept the following:
|
||
|
||
o PKIX Certificates containing and signed by RSA keys of size 1024
|
||
or 2048 bits, where the ID passed is any of ID_KEY_ID, ID_FQDN,
|
||
ID_RFC822_ADDR, or ID_DER_ASN1_DN.
|
||
|
||
o Shared key authentication where the ID passed is any of ID_KEY_ID,
|
||
ID_FQDN, or ID_RFC822_ADDR.
|
||
|
||
o Authentication where the responder is authenticated using PKIX
|
||
Certificates and the initiator is authenticated using shared key
|
||
authentication.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 105]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
5. Security Considerations
|
||
|
||
While this protocol is designed to minimize disclosure of
|
||
configuration information to unauthenticated peers, some such
|
||
disclosure is unavoidable. One peer or the other must identify
|
||
itself first and prove its identity first. To avoid probing, the
|
||
initiator of an exchange is required to identify itself first, and
|
||
usually is required to authenticate itself first. The initiator can,
|
||
however, learn that the responder supports IKE and what cryptographic
|
||
protocols it supports. The responder (or someone impersonating the
|
||
responder) can probe the initiator not only for its identity, but
|
||
using CERTREQ payloads may be able to determine what certificates the
|
||
initiator is willing to use.
|
||
|
||
Use of EAP authentication changes the probing possibilities somewhat.
|
||
When EAP authentication is used, the responder proves its identity
|
||
before the initiator does, so an initiator that knew the name of a
|
||
valid initiator could probe the responder for both its name and
|
||
certificates.
|
||
|
||
Repeated rekeying using CREATE_CHILD_SA without additional Diffie-
|
||
Hellman exchanges leaves all SAs vulnerable to cryptanalysis of a
|
||
single key or overrun of either endpoint. Implementers should take
|
||
note of this fact and set a limit on CREATE_CHILD_SA exchanges
|
||
between exponentiations. This memo does not prescribe such a limit.
|
||
|
||
The strength of a key derived from a Diffie-Hellman exchange using
|
||
any of the groups defined here depends on the inherent strength of
|
||
the group, the size of the exponent used, and the entropy provided by
|
||
the random number generator used. Due to these inputs, it is
|
||
difficult to determine the strength of a key for any of the defined
|
||
groups. Diffie-Hellman group number two, when used with a strong
|
||
random number generator and an exponent no less than 200 bits, is
|
||
common for use with 3DES. Group five provides greater security than
|
||
group two. Group one is for historic purposes only and does not
|
||
provide sufficient strength except for use with DES, which is also
|
||
for historic use only. Implementations should make note of these
|
||
estimates when establishing policy and negotiating security
|
||
parameters.
|
||
|
||
Note that these limitations are on the Diffie-Hellman groups
|
||
themselves. There is nothing in IKE that prohibits using stronger
|
||
groups nor is there anything that will dilute the strength obtained
|
||
from stronger groups (limited by the strength of the other algorithms
|
||
negotiated including the prf function). In fact, the extensible
|
||
framework of IKE encourages the definition of more groups; use of
|
||
elliptical curve groups may greatly increase strength using much
|
||
smaller numbers.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 106]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
It is assumed that all Diffie-Hellman exponents are erased from
|
||
memory after use. In particular, these exponents MUST NOT be derived
|
||
from long-lived secrets like the seed to a pseudo-random generator
|
||
that is not erased after use.
|
||
|
||
The strength of all keys is limited by the size of the output of the
|
||
negotiated prf function. For this reason, a prf function whose
|
||
output is less than 128 bits (e.g., 3DES-CBC) MUST NOT be used with
|
||
this protocol.
|
||
|
||
The security of this protocol is critically dependent on the
|
||
randomness of the randomly chosen parameters. These should be
|
||
generated by a strong random or properly seeded pseudo-random source
|
||
(see [RANDOMNESS]). Implementers should take care to ensure that use
|
||
of random numbers for both keys and nonces is engineered in a fashion
|
||
that does not undermine the security of the keys.
|
||
|
||
For information on the rationale of many of the cryptographic design
|
||
choices in this protocol, see [SIGMA] and [SKEME]. Though the
|
||
security of negotiated CHILD_SAs does not depend on the strength of
|
||
the encryption and integrity protection negotiated in the IKE_SA,
|
||
implementations MUST NOT negotiate NONE as the IKE integrity
|
||
protection algorithm or ENCR_NULL as the IKE encryption algorithm.
|
||
|
||
When using pre-shared keys, a critical consideration is how to assure
|
||
the randomness of these secrets. The strongest practice is to ensure
|
||
that any pre-shared key contain as much randomness as the strongest
|
||
key being negotiated. Deriving a shared secret from a password,
|
||
name, or other low-entropy source is not secure. These sources are
|
||
subject to dictionary and social engineering attacks, among others.
|
||
|
||
The NAT_DETECTION_*_IP notifications contain a hash of the addresses
|
||
and ports in an attempt to hide internal IP addresses behind a NAT.
|
||
Since the IPv4 address space is only 32 bits, and it is usually very
|
||
sparse, it would be possible for an attacker to find out the internal
|
||
address used behind the NAT box by trying all possible IP addresses
|
||
and trying to find the matching hash. The port numbers are normally
|
||
fixed to 500, and the SPIs can be extracted from the packet. This
|
||
reduces the number of hash calculations to 2^32. With an educated
|
||
guess of the use of private address space, the number of hash
|
||
calculations is much smaller. Designers should therefore not assume
|
||
that use of IKE will not leak internal address information.
|
||
|
||
When using an EAP authentication method that does not generate a
|
||
shared key for protecting a subsequent AUTH payload, certain man-in-
|
||
the-middle and server impersonation attacks are possible [EAPMITM].
|
||
These vulnerabilities occur when EAP is also used in protocols that
|
||
are not protected with a secure tunnel. Since EAP is a general-
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 107]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
purpose authentication protocol, which is often used to provide
|
||
single-signon facilities, a deployed IPsec solution that relies on an
|
||
EAP authentication method that does not generate a shared key (also
|
||
known as a non-key-generating EAP method) can become compromised due
|
||
to the deployment of an entirely unrelated application that also
|
||
happens to use the same non-key-generating EAP method, but in an
|
||
unprotected fashion. Note that this vulnerability is not limited to
|
||
just EAP, but can occur in other scenarios where an authentication
|
||
infrastructure is reused. For example, if the EAP mechanism used by
|
||
IKEv2 utilizes a token authenticator, a man-in-the-middle attacker
|
||
could impersonate the web server, intercept the token authentication
|
||
exchange, and use it to initiate an IKEv2 connection. For this
|
||
reason, use of non-key-generating EAP methods SHOULD be avoided where
|
||
possible. Where they are used, it is extremely important that all
|
||
usages of these EAP methods SHOULD utilize a protected tunnel, where
|
||
the initiator validates the responder's certificate before initiating
|
||
the EAP exchange. {{ Demoted the SHOULD }} Implementers should
|
||
describe the vulnerabilities of using non-key-generating EAP methods
|
||
in the documentation of their implementations so that the
|
||
administrators deploying IPsec solutions are aware of these dangers.
|
||
|
||
An implementation using EAP MUST also use strong authentication of
|
||
the server to the client before the EAP exchange begins, even if the
|
||
EAP method offers mutual authentication. This avoids having
|
||
additional IKEv2 protocol variations and protects the EAP data from
|
||
active attackers.
|
||
|
||
If the messages of IKEv2 are long enough that IP-level fragmentation
|
||
is necessary, it is possible that attackers could prevent the
|
||
exchange from completing by exhausting the reassembly buffers. The
|
||
chances of this can be minimized by using the Hash and URL encodings
|
||
instead of sending certificates (see Section 3.6). Additional
|
||
mitigations are discussed in [DOSUDPPROT].
|
||
|
||
5.1. Traffic selector authorization
|
||
|
||
{{ Added this section from Clarif-4.13 }}
|
||
|
||
IKEv2 relies on information in the Peer Authorization Database (PAD)
|
||
when determining what kind of IPsec SAs a peer is allowed to create.
|
||
This process is described in [IPSECARCH] Section 4.4.3. When a peer
|
||
requests the creation of an IPsec SA with some traffic selectors, the
|
||
PAD must contain "Child SA Authorization Data" linking the identity
|
||
authenticated by IKEv2 and the addresses permitted for traffic
|
||
selectors.
|
||
|
||
For example, the PAD might be configured so that authenticated
|
||
identity "sgw23.example.com" is allowed to create IPsec SAs for
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 108]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
192.0.2.0/24, meaning this security gateway is a valid
|
||
"representative" for these addresses. Host-to-host IPsec requires
|
||
similar entries, linking, for example, "fooserver4.example.com" with
|
||
192.0.1.66/32, meaning this identity a valid "owner" or
|
||
"representative" of the address in question.
|
||
|
||
As noted in [IPSECARCH], "It is necessary to impose these constraints
|
||
on creation of child SAs to prevent an authenticated peer from
|
||
spoofing IDs associated with other, legitimate peers." In the
|
||
example given above, a correct configuration of the PAD prevents
|
||
sgw23 from creating IPsec SAs with address 192.0.1.66, and prevents
|
||
fooserver4 from creating IPsec SAs with addresses from 192.0.2.0/24.
|
||
|
||
It is important to note that simply sending IKEv2 packets using some
|
||
particular address does not imply a permission to create IPsec SAs
|
||
with that address in the traffic selectors. For example, even if
|
||
sgw23 would be able to spoof its IP address as 192.0.1.66, it could
|
||
not create IPsec SAs matching fooserver4's traffic.
|
||
|
||
The IKEv2 specification does not specify how exactly IP address
|
||
assignment using configuration payloads interacts with the PAD. Our
|
||
interpretation is that when a security gateway assigns an address
|
||
using configuration payloads, it also creates a temporary PAD entry
|
||
linking the authenticated peer identity and the newly allocated inner
|
||
address.
|
||
|
||
It has been recognized that configuring the PAD correctly may be
|
||
difficult in some environments. For instance, if IPsec is used
|
||
between a pair of hosts whose addresses are allocated dynamically
|
||
using DHCP, it is extremely difficult to ensure that the PAD
|
||
specifies the correct "owner" for each IP address. This would
|
||
require a mechanism to securely convey address assignments from the
|
||
DHCP server, and link them to identities authenticated using IKEv2.
|
||
|
||
Due to this limitation, some vendors have been known to configure
|
||
their PADs to allow an authenticated peer to create IPsec SAs with
|
||
traffic selectors containing the same address that was used for the
|
||
IKEv2 packets. In environments where IP spoofing is possible (i.e.,
|
||
almost everywhere) this essentially allows any peer to create IPsec
|
||
SAs with any traffic selectors. This is not an appropriate or secure
|
||
configuration in most circumstances. See [H2HIPSEC] for an extensive
|
||
discussion about this issue, and the limitations of host-to-host
|
||
IPsec in general.
|
||
|
||
|
||
6. IANA Considerations
|
||
|
||
{{ This section was changed to not re-define any new IANA registries.
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 109]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
}}
|
||
|
||
[IKEV2] defined many field types and values. IANA has already
|
||
registered those types and values, so the are not listed here again.
|
||
No new types or values are registered in this document. However,
|
||
IANA should update all references to RFC 4306 to point to this
|
||
document.
|
||
|
||
|
||
7. Acknowledgements
|
||
|
||
The individuals on the IPsec mailing list was very helpful in both
|
||
pointing out where clarifications and changes were needed, as well as
|
||
in reviewing the clarifications suggested by others.
|
||
|
||
The acknowledgements from the IKEv2 document were:
|
||
|
||
This document is a collaborative effort of the entire IPsec WG. If
|
||
there were no limit to the number of authors that could appear on an
|
||
RFC, the following, in alphabetical order, would have been listed:
|
||
Bill Aiello, Stephane Beaulieu, Steve Bellovin, Sara Bitan, Matt
|
||
Blaze, Ran Canetti, Darren Dukes, Dan Harkins, Paul Hoffman, John
|
||
Ioannidis, Charlie Kaufman, Steve Kent, Angelos Keromytis, Tero
|
||
Kivinen, Hugo Krawczyk, Andrew Krywaniuk, Radia Perlman, Omer
|
||
Reingold, and Michael Richardson. Many other people contributed to
|
||
the design. It is an evolution of IKEv1, ISAKMP, and the IPsec DOI,
|
||
each of which has its own list of authors. Hugh Daniel suggested the
|
||
feature of having the initiator, in message 3, specify a name for the
|
||
responder, and gave the feature the cute name "You Tarzan, Me Jane".
|
||
David Faucher and Valery Smyzlov helped refine the design of the
|
||
traffic selector negotiation.
|
||
|
||
This paragraph lists references that appear only in figures. The
|
||
section is only here to keep the 'xml2rfc' program happy, and needs
|
||
to be removed when the document is published. Feel free to ignore
|
||
it. [DES] [IDEA] [MD5] [X.501] [X.509]
|
||
|
||
|
||
8. References
|
||
|
||
8.1. Normative References
|
||
|
||
[ADDGROUP]
|
||
Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
|
||
Diffie-Hellman groups for Internet Key Exchange (IKE)",
|
||
RFC 3526, May 2003.
|
||
|
||
[ADDRIPV6]
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 110]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Hinden, R. and S. Deering, "Internet Protocol Version 6
|
||
(IPv6) Addressing Architecture", RFC 4291, February 2006.
|
||
|
||
[EAP] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
|
||
Levkowetz, "Extensible Authentication Protocol (EAP)",
|
||
RFC 3748, June 2004.
|
||
|
||
[ECN] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
|
||
of Explicit Congestion Notification (ECN) to IP",
|
||
RFC 3168, September 2001.
|
||
|
||
[ESPCBC] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher
|
||
Algorithms", RFC 2451, November 1998.
|
||
|
||
[IPSECARCH]
|
||
Kent, S. and K. Seo, "Security Architecture for the
|
||
Internet Protocol", RFC 4301, December 2005.
|
||
|
||
[MUSTSHOULD]
|
||
Bradner, S., "Key Words for use in RFCs to indicate
|
||
Requirement Levels", BCP 14, RFC 2119, March 1997.
|
||
|
||
[PKCS1] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
|
||
Standards (PKCS) #1: RSA Cryptography Specifications
|
||
Version 2.1", RFC 3447, February 2003.
|
||
|
||
[PKIX] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
|
||
X.509 Public Key Infrastructure Certificate and
|
||
Certificate Revocation List (CRL) Profile", RFC 3280,
|
||
April 2002.
|
||
|
||
[RFC4434] Hoffman, P., "The AES-XCBC-PRF-128 Algorithm for the
|
||
Internet Key Exchange Protocol (IKE)", RFC 4434,
|
||
February 2006.
|
||
|
||
[RFC4615] Song, J., Poovendran, R., Lee, J., and T. Iwata, "The
|
||
Advanced Encryption Standard-Cipher-based Message
|
||
Authentication Code-Pseudo-Random Function-128 (AES-CMAC-
|
||
PRF-128) Algorithm for the Internet Key Exchange Protocol
|
||
(IKE)", RFC 4615, August 2006.
|
||
|
||
[UDPENCAPS]
|
||
Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
|
||
Stenberg, "UDP Encapsulation of IPsec ESP Packets",
|
||
RFC 3948, January 2005.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 111]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
8.2. Informative References
|
||
|
||
[AH] Kent, S., "IP Authentication Header", RFC 4302,
|
||
December 2005.
|
||
|
||
[ARCHGUIDEPHIL]
|
||
Bush, R. and D. Meyer, "Some Internet Architectural
|
||
Guidelines and Philosophy", RFC 3439, December 2002.
|
||
|
||
[ARCHPRINC]
|
||
Carpenter, B., "Architectural Principles of the Internet",
|
||
RFC 1958, June 1996.
|
||
|
||
[Clarif] Eronen, P. and P. Hoffman, "IKEv2 Clarifications and
|
||
Implementation Guidelines", RFC 4718, October 2006.
|
||
|
||
[DES] American National Standards Institute, "American National
|
||
Standard for Information Systems-Data Link Encryption",
|
||
ANSI X3.106, 1983.
|
||
|
||
[DH] Diffie, W. and M. Hellman, "New Directions in
|
||
Cryptography", IEEE Transactions on Information Theory,
|
||
V.IT-22 n. 6, June 1977.
|
||
|
||
[DHCP] Droms, R., "Dynamic Host Configuration Protocol",
|
||
RFC 2131, March 1997.
|
||
|
||
[DIFFSERVARCH]
|
||
Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
|
||
and W. Weiss, "An Architecture for Differentiated
|
||
Services", RFC 2475.
|
||
|
||
[DIFFSERVFIELD]
|
||
Nichols, K., Blake, S., Baker, F., and D. Black,
|
||
"Definition of the Differentiated Services Field (DS
|
||
Field) in the IPv4 and IPv6 Headers", RFC 2474,
|
||
December 1998.
|
||
|
||
[DIFFTUNNEL]
|
||
Black, D., "Differentiated Services and Tunnels",
|
||
RFC 2983, October 2000.
|
||
|
||
[DOI] Piper, D., "The Internet IP Security Domain of
|
||
Interpretation for ISAKMP", RFC 2407, November 1998.
|
||
|
||
[DOSUDPPROT]
|
||
C. Kaufman, R. Perlman, and B. Sommerfeld, "DoS protection
|
||
for UDP-based protocols", ACM Conference on Computer and
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 112]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Communications Security , October 2003.
|
||
|
||
[DSS] National Institute of Standards and Technology, U.S.
|
||
Department of Commerce, "Digital Signature Standard",
|
||
FIPS 186, May 1994.
|
||
|
||
[EAPMITM] N. Asokan, V. Nierni, and K. Nyberg, "Man-in-the-Middle in
|
||
Tunneled Authentication Protocols", November 2002,
|
||
<http://eprint.iacr.org/2002/163>.
|
||
|
||
[ESP] Kent, S., "IP Encapsulating Security Payload (ESP)",
|
||
RFC 4303, December 2005.
|
||
|
||
[EXCHANGEANALYSIS]
|
||
R. Perlman and C. Kaufman, "Analysis of the IPsec key
|
||
exchange Standard", WET-ICE Security Conference, MIT ,
|
||
2001,
|
||
<http://sec.femto.org/wetice-2001/papers/radia-paper.pdf>.
|
||
|
||
[H2HIPSEC]
|
||
Aura, T., Roe, M., and A. Mohammed, "Experiences with
|
||
Host-to-Host IPsec", 13th International Workshop on
|
||
Security Protocols, Cambridge, UK, April 2005.
|
||
|
||
[HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
|
||
Hashing for Message Authentication", RFC 2104,
|
||
February 1997.
|
||
|
||
[IDEA] X. Lai, "On the Design and Security of Block Ciphers", ETH
|
||
Series in Information Processing, v. 1, Konstanz: Hartung-
|
||
Gorre Verlag, 1992.
|
||
|
||
[IDNA] Faltstrom, P., Hoffman, P., and A. Costello,
|
||
"Internationalizing Domain Names in Applications (IDNA)",
|
||
RFC 3490, March 2003.
|
||
|
||
[IKEV1] Harkins, D. and D. Carrel, "The Internet Key Exchange
|
||
(IKE)", RFC 2409, November 1998.
|
||
|
||
[IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
|
||
RFC 4306, December 2005.
|
||
|
||
[IPCOMP] Shacham, A., Monsour, B., Pereira, R., and M. Thomas, "IP
|
||
Payload Compression Protocol (IPComp)", RFC 3173,
|
||
September 2001.
|
||
|
||
[IPSECARCH-OLD]
|
||
Kent, S. and R. Atkinson, "Security Architecture for the
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 113]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Internet Protocol", RFC 2401, November 1998.
|
||
|
||
[IPV6ADDR]
|
||
Hinden, R. and S. Deering, "Internet Protocol Version 6
|
||
(IPv6) Addressing Architecture", RFC 3513, April 2003.
|
||
|
||
[ISAKMP] Maughan, D., Schneider, M., and M. Schertler, "Internet
|
||
Security Association and Key Management Protocol
|
||
(ISAKMP)", RFC 2408, November 1998.
|
||
|
||
[LDAP] Wahl, M., Howes, T., and S. Kille, "Lightweight Directory
|
||
Access Protocol (v3)", RFC 2251, December 1997.
|
||
|
||
[MAILFORMAT]
|
||
Resnick, P., "Internet Message Format", RFC 2822,
|
||
April 2001.
|
||
|
||
[MD5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
|
||
April 1992.
|
||
|
||
[MIPV6] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
|
||
in IPv6", RFC 3775, June 2004.
|
||
|
||
[MLDV2] Vida, R. and L. Costa, "Multicast Listener Discovery
|
||
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
|
||
|
||
[MODES] National Institute of Standards and Technology, U.S.
|
||
Department of Commerce, "Recommendation for Block Cipher
|
||
Modes of Operation", SP 800-38A, 2001.
|
||
|
||
[NAI] Aboba, B. and M. Beadles, "The Network Access Identifier",
|
||
RFC 2486, January 1999.
|
||
|
||
[NATREQ] Aboba, B. and W. Dixon, "IPsec-Network Address Translation
|
||
(NAT) Compatibility Requirements", RFC 3715, March 2004.
|
||
|
||
[OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
|
||
RFC 2412, November 1998.
|
||
|
||
[PFKEY] McDonald, D., Metz, C., and B. Phan, "PF_KEY Key
|
||
Management API, Version 2", RFC 2367, July 1998.
|
||
|
||
[PHOTURIS]
|
||
Karn, P. and W. Simpson, "Photuris: Session-Key Management
|
||
Protocol", RFC 2522, March 1999.
|
||
|
||
[RADIUS] Rigney, C., Rubens, A., Simpson, W., and S. Willens,
|
||
"Remote Authentication Dial In User Service (RADIUS)",
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 114]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
RFC 2138, April 1997.
|
||
|
||
[RANDOMNESS]
|
||
Eastlake, D., Schiller, J., and S. Crocker, "Randomness
|
||
Requirements for Security", BCP 106, RFC 4086, June 2005.
|
||
|
||
[REAUTH] Nir, Y., "Repeated Authentication in Internet Key Exchange
|
||
(IKEv2) Protocol", RFC 4478, April 2006.
|
||
|
||
[RSA] R. Rivest, A. Shamir, and L. Adleman, "A Method for
|
||
Obtaining Digital Signatures and Public-Key
|
||
Cryptosystems", February 1978.
|
||
|
||
[SHA] National Institute of Standards and Technology, U.S.
|
||
Department of Commerce, "Secure Hash Standard",
|
||
FIPS 180-1, May 1994.
|
||
|
||
[SIGMA] H. Krawczyk, "SIGMA: the `SIGn-and-MAc' Approach to
|
||
Authenticated Diffie-Hellman and its Use in the IKE
|
||
Protocols", Advances in Cryptography - CRYPTO 2003
|
||
Proceedings LNCS 2729, 2003, <http://
|
||
www.informatik.uni-trier.de/~ley/db/conf/crypto/
|
||
crypto2003.html>.
|
||
|
||
[SKEME] H. Krawczyk, "SKEME: A Versatile Secure Key Exchange
|
||
Mechanism for Internet", IEEE Proceedings of the 1996
|
||
Symposium on Network and Distributed Systems Security ,
|
||
1996.
|
||
|
||
[TRANSPARENCY]
|
||
Carpenter, B., "Internet Transparency", RFC 2775,
|
||
February 2000.
|
||
|
||
[X.501] ITU-T, "Recommendation X.501: Information Technology -
|
||
Open Systems Interconnection - The Directory: Models",
|
||
1993.
|
||
|
||
[X.509] ITU-T, "Recommendation X.509 (1997 E): Information
|
||
Technology - Open Systems Interconnection - The Directory:
|
||
Authentication Framework", 1997.
|
||
|
||
|
||
Appendix A. Summary of changes from IKEv1
|
||
|
||
The goals of this revision to IKE are:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 115]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
1. To define the entire IKE protocol in a single document,
|
||
replacing RFCs 2407, 2408, and 2409 and incorporating subsequent
|
||
changes to support NAT Traversal, Extensible Authentication, and
|
||
Remote Address acquisition;
|
||
|
||
2. To simplify IKE by replacing the eight different initial
|
||
exchanges with a single four-message exchange (with changes in
|
||
authentication mechanisms affecting only a single AUTH payload
|
||
rather than restructuring the entire exchange) see
|
||
[EXCHANGEANALYSIS];
|
||
|
||
3. To remove the Domain of Interpretation (DOI), Situation (SIT),
|
||
and Labeled Domain Identifier fields, and the Commit and
|
||
Authentication only bits;
|
||
|
||
4. To decrease IKE's latency in the common case by making the
|
||
initial exchange be 2 round trips (4 messages), and allowing the
|
||
ability to piggyback setup of a CHILD_SA on that exchange;
|
||
|
||
5. To replace the cryptographic syntax for protecting the IKE
|
||
messages themselves with one based closely on ESP to simplify
|
||
implementation and security analysis;
|
||
|
||
6. To reduce the number of possible error states by making the
|
||
protocol reliable (all messages are acknowledged) and sequenced.
|
||
This allows shortening CREATE_CHILD_SA exchanges from 3 messages
|
||
to 2;
|
||
|
||
7. To increase robustness by allowing the responder to not do
|
||
significant processing until it receives a message proving that
|
||
the initiator can receive messages at its claimed IP address;
|
||
|
||
8. To fix cryptographic weaknesses such as the problem with
|
||
symmetries in hashes used for authentication documented by Tero
|
||
Kivinen;
|
||
|
||
9. To specify Traffic Selectors in their own payloads type rather
|
||
than overloading ID payloads, and making more flexible the
|
||
Traffic Selectors that may be specified;
|
||
|
||
10. To specify required behavior under certain error conditions or
|
||
when data that is not understood is received in order to make it
|
||
easier to make future revisions in a way that does not break
|
||
backwards compatibility;
|
||
|
||
11. To simplify and clarify how shared state is maintained in the
|
||
presence of network failures and Denial of Service attacks; and
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 116]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
12. To maintain existing syntax and magic numbers to the extent
|
||
possible to make it likely that implementations of IKEv1 can be
|
||
enhanced to support IKEv2 with minimum effort.
|
||
|
||
|
||
Appendix B. Diffie-Hellman Groups
|
||
|
||
There are two Diffie-Hellman groups defined here for use in IKE.
|
||
These groups were generated by Richard Schroeppel at the University
|
||
of Arizona. Properties of these primes are described in [OAKLEY].
|
||
|
||
The strength supplied by group one may not be sufficient for the
|
||
mandatory-to-implement encryption algorithm and is here for historic
|
||
reasons.
|
||
|
||
Additional Diffie-Hellman groups have been defined in [ADDGROUP].
|
||
|
||
B.1. Group 1 - 768 Bit MODP
|
||
|
||
This group is assigned id 1 (one).
|
||
|
||
The prime is: 2^768 - 2 ^704 - 1 + 2^64 * { [2^638 pi] + 149686 }
|
||
Its hexadecimal value is:
|
||
|
||
FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
|
||
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
|
||
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
|
||
E485B576 625E7EC6 F44C42E9 A63A3620 FFFFFFFF FFFFFFFF
|
||
|
||
The generator is 2.
|
||
|
||
B.2. Group 2 - 1024 Bit MODP
|
||
|
||
This group is assigned id 2 (two).
|
||
|
||
The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
|
||
Its hexadecimal value is:
|
||
|
||
FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
|
||
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
|
||
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
|
||
E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
|
||
EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381
|
||
FFFFFFFF FFFFFFFF
|
||
|
||
The generator is 2.
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 117]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Appendix C. Exchanges and Payloads
|
||
|
||
{{ Clarif-AppA }}
|
||
|
||
This appendix contains a short summary of the IKEv2 exchanges, and
|
||
what payloads can appear in which message. This appendix is purely
|
||
informative; if it disagrees with the body of this document, the
|
||
other text is considered correct.
|
||
|
||
Vendor-ID (V) payloads may be included in any place in any message.
|
||
This sequence here shows what are the most logical places for them.
|
||
|
||
C.1. IKE_SA_INIT Exchange
|
||
|
||
request --> [N(COOKIE)],
|
||
SA, KE, Ni,
|
||
[N(NAT_DETECTION_SOURCE_IP)+,
|
||
N(NAT_DETECTION_DESTINATION_IP)],
|
||
[V+]
|
||
|
||
normal response <-- SA, KE, Nr,
|
||
(no cookie) [N(NAT_DETECTION_SOURCE_IP),
|
||
N(NAT_DETECTION_DESTINATION_IP)],
|
||
[[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],
|
||
[V+]
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 118]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
C.2. IKE_AUTH Exchange without EAP
|
||
|
||
request --> IDi, [CERT+],
|
||
[N(INITIAL_CONTACT)],
|
||
[[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],
|
||
[IDr],
|
||
AUTH,
|
||
[CP(CFG_REQUEST)],
|
||
[N(IPCOMP_SUPPORTED)+],
|
||
[N(USE_TRANSPORT_MODE)],
|
||
[N(ESP_TFC_PADDING_NOT_SUPPORTED)],
|
||
[N(NON_FIRST_FRAGMENTS_ALSO)],
|
||
SA, TSi, TSr,
|
||
[V+]
|
||
|
||
response <-- IDr, [CERT+],
|
||
AUTH,
|
||
[CP(CFG_REPLY)],
|
||
[N(IPCOMP_SUPPORTED)],
|
||
[N(USE_TRANSPORT_MODE)],
|
||
[N(ESP_TFC_PADDING_NOT_SUPPORTED)],
|
||
[N(NON_FIRST_FRAGMENTS_ALSO)],
|
||
SA, TSi, TSr,
|
||
[N(ADDITIONAL_TS_POSSIBLE)],
|
||
[V+]
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 119]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
C.3. IKE_AUTH Exchange with EAP
|
||
|
||
first request --> IDi,
|
||
[N(INITIAL_CONTACT)],
|
||
[[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],
|
||
[IDr],
|
||
[CP(CFG_REQUEST)],
|
||
[N(IPCOMP_SUPPORTED)+],
|
||
[N(USE_TRANSPORT_MODE)],
|
||
[N(ESP_TFC_PADDING_NOT_SUPPORTED)],
|
||
[N(NON_FIRST_FRAGMENTS_ALSO)],
|
||
SA, TSi, TSr,
|
||
[V+]
|
||
|
||
first response <-- IDr, [CERT+], AUTH,
|
||
EAP,
|
||
[V+]
|
||
|
||
/ --> EAP
|
||
repeat 1..N times |
|
||
\ <-- EAP
|
||
|
||
last request --> AUTH
|
||
|
||
last response <-- AUTH,
|
||
[CP(CFG_REPLY)],
|
||
[N(IPCOMP_SUPPORTED)],
|
||
[N(USE_TRANSPORT_MODE)],
|
||
[N(ESP_TFC_PADDING_NOT_SUPPORTED)],
|
||
[N(NON_FIRST_FRAGMENTS_ALSO)],
|
||
SA, TSi, TSr,
|
||
[N(ADDITIONAL_TS_POSSIBLE)],
|
||
[V+]
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 120]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
C.4. CREATE_CHILD_SA Exchange for Creating or Rekeying CHILD_SAs
|
||
|
||
request --> [N(REKEY_SA)],
|
||
[CP(CFG_REQUEST)],
|
||
[N(IPCOMP_SUPPORTED)+],
|
||
[N(USE_TRANSPORT_MODE)],
|
||
[N(ESP_TFC_PADDING_NOT_SUPPORTED)],
|
||
[N(NON_FIRST_FRAGMENTS_ALSO)],
|
||
SA, Ni, [KEi], TSi, TSr
|
||
|
||
response <-- [CP(CFG_REPLY)],
|
||
[N(IPCOMP_SUPPORTED)],
|
||
[N(USE_TRANSPORT_MODE)],
|
||
[N(ESP_TFC_PADDING_NOT_SUPPORTED)],
|
||
[N(NON_FIRST_FRAGMENTS_ALSO)],
|
||
SA, Nr, [KEr], TSi, TSr,
|
||
[N(ADDITIONAL_TS_POSSIBLE)]
|
||
|
||
C.5. CREATE_CHILD_SA Exchange for Rekeying the IKE_SA
|
||
|
||
request --> SA, Ni, [KEi]
|
||
|
||
response <-- SA, Nr, [KEr]
|
||
|
||
C.6. INFORMATIONAL Exchange
|
||
|
||
request --> [N+],
|
||
[D+],
|
||
[CP(CFG_REQUEST)]
|
||
|
||
response <-- [N+],
|
||
[D+],
|
||
[CP(CFG_REPLY)]
|
||
|
||
|
||
Appendix D. Changes Between Internet Draft Versions
|
||
|
||
This section will be removed before publication as an RFC, but should
|
||
be left intact until then so that reviewers can follow what has
|
||
changed.
|
||
|
||
D.1. Changes from IKEv2 to draft -00
|
||
|
||
There were a zillion additions from RFC 4718. These are noted with
|
||
"{{ Clarif-nn }}".
|
||
|
||
Cleaned up many of the figures. Made the table headings consistent.
|
||
Made some tables easier to read by removing blank spaces. Removed
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 121]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
the "reserved to IANA" and "private use" text wording and moved it
|
||
into the tables.
|
||
|
||
Changed many SHOULD requirements to better match RFC 2119. These are
|
||
also marked with comments such as "{{ Demoted the SHOULD }}".
|
||
|
||
In Section 2.16, changed the MUST requirement of authenticating the
|
||
responder from "public key signature based" to "strong" because that
|
||
is what most current IKEv2 implementations do, and it better matches
|
||
the actual security requirement.
|
||
|
||
D.2. Changes from draft -00 to draft -01
|
||
|
||
The most significant technical change was to make KE optional but
|
||
strongly recommended in Section 1.3.2.
|
||
|
||
Updated all references to the IKEv2 Clarifications document to RFC
|
||
4718.
|
||
|
||
Moved a lot of the protocol description out of the long tables in
|
||
Section 3.10.1 into the body of the document. These are noted with
|
||
"{{ 3.10.1-nnnn }}", where "nnnn" is the notification type number.
|
||
|
||
Made some table changes based on suggestions from Alfred Hoenes.
|
||
|
||
Changed "byte" to "octet" in many places.
|
||
|
||
Removed discussion of ESP+AH bundles in many places, and added a
|
||
paragraph about it in Section 1.7.
|
||
|
||
Removed the discussion of INTERNAL_ADDRESS_EXPIRY in many places, and
|
||
added a paragraph about it in Section 1.7.
|
||
|
||
Moved Clarif-7.10 from Section 1.2 to Section 3.2.
|
||
|
||
In the figure in Section 1.3.2, made KEi optional, and added text
|
||
saying "The KEi payload SHOULD be included."
|
||
|
||
In the figure in Section 1.3.2, maked KEr optional, and removed text
|
||
saying "KEi and KEr are required for rekeying an IKE_SA."
|
||
|
||
In Section 1.4, clarified that the half-closed connections being
|
||
discussed are AH and ESP.
|
||
|
||
Rearranged the end of Section 1.7, and added the new notation for
|
||
moving text out of 3.10.1.
|
||
|
||
Clarified the wording in the second paragraph of Section 2.2. This
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 122]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
allowd the removal of the fourth paragraph, which previously had
|
||
Clarif-2.2 in it.
|
||
|
||
In section 2.5, removed "or later" from "version 2.0".
|
||
|
||
Added the question for implementers about payload order at the end of
|
||
Section 2.5.
|
||
|
||
Corrected Section 2.7 based on Clarif-7-13 to say that you can't do
|
||
ESP and AH at one time.
|
||
|
||
In Section 2.8, clarified the wording about how to replace an IKE_SA.
|
||
|
||
Clarified the text in the last many paragraphs in Section 2.9. Also
|
||
moved some text from near the beginning of 2.9 to the beginning of
|
||
2.9.1.
|
||
|
||
Removed some redundant text in Section 2.9 concerning creating a
|
||
CHILD_SA pair not in response to an arriving packet.
|
||
|
||
Added the following to the end of the first paragraph of Section
|
||
2.14: "The lengths of SK_d, SK_pi, and SK_pr are the key length of
|
||
the agreed-to PRF."
|
||
|
||
Added the restriction in Section 2.15 that all PRFs used with IKEv2
|
||
MUST take variable-sized keys.
|
||
|
||
In Section 2.17, removed "If multiple IPsec protocols are negotiated,
|
||
keying material is taken in the order in which the protocol headers
|
||
will appear in the encapsulated packet" because multiple IPsec
|
||
protocols cannot be negotiated at one time.
|
||
|
||
Added the material from Clarif-5.12 to Section 2.18.
|
||
|
||
Changed "hash of" to "expected value of" in Section 2.23.
|
||
|
||
In the bulleted list in Section 2.23, replaced "this end" with a
|
||
clearer description of which system is being discussed.
|
||
|
||
Added the paragraph at the beginning of Section 3 about
|
||
interoperability and UNSPECIFIED values ("In the tables in this
|
||
section...").
|
||
|
||
Fixed Section 3.3 to not include proposal that include both AH and
|
||
ESP. Ditto for the "Proposal #" bullet in Section 3.3.1.
|
||
|
||
In the description of ID_FQDN in Section 3.5, added "All characters
|
||
in the ID_FQDN are ASCII; this follows that for an "internationalized
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 123]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
domain name" as defined in [IDNA]."
|
||
|
||
In Section 3.8, shortened and clarified the description of "RSA
|
||
Digital Signature".
|
||
|
||
In Section 3.10, shortened and clarified the description of "Protocol
|
||
ID".
|
||
|
||
In Section 3.15, "The requested address is valid until the expiry
|
||
time defined with the INTERNAL_ADDRESS_EXPIRY attribute or there are
|
||
no IKE_SAs between the peers" is shortened to just "The requested
|
||
address is valid until there are no IKE_SAs between the peers."
|
||
|
||
In Section 3.15.1, changed "INTERNAL_IP6_NBNS" to unspecified.
|
||
|
||
Made [ADDRIPV6] an informative reference instead of a normative
|
||
reference and updated it.
|
||
|
||
Made [PKCS1] a normative reference instead of an informative
|
||
reference and changed the pointer to RFC 3447.
|
||
|
||
D.3. Changes from draft -00 to draft -01
|
||
|
||
In Section 1.5, added "request" to first sentence to make it "If an
|
||
encrypted IKE request packet arrives on port 500 or 4500 with an
|
||
unrecognized SPI...".
|
||
|
||
In Section 3.3, fifth paragraph, upped the number of transforms for
|
||
AH and ESP by one each to account for ESN, which is now mandatory.
|
||
|
||
In Section 2.1, added "or equal to" in "The responder MUST remember
|
||
each response until it receives a request whose sequence number is
|
||
larger than or equal to the sequence number in the response plus its
|
||
window size."
|
||
|
||
In Section 2.18, removed " Note that this may not work if the new
|
||
IKE_SA's PRF has a fixed key size because the output of the PRF may
|
||
not be of the correct size." because it is no longer relevant.
|
||
|
||
D.4. Changes from draft -01 to draft -02
|
||
|
||
Many grammatical fixes.
|
||
|
||
In Section 1.2, reworded Clarif-4.3 to be clearer.
|
||
|
||
In Section 1.3.3, reworded 3.10.1-16393 and Clarif-5.4 to remove
|
||
redundant text.
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 124]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
In Section 2.13, replaced text about variable length keys with
|
||
clearer explanation and requirement on non-HMAC PRFs. Also added
|
||
"preferred" to Section 2.14 for the key length, and removed redundant
|
||
text.
|
||
|
||
In Section 2.14, removed the "half and half" description and replaced
|
||
it with exceptions for RFC4434 and RFC4615.
|
||
|
||
Removed the now-redundant "All PRFs used with IKEv2 MUST take
|
||
variable-sized keys" from Section 2.15.
|
||
|
||
In Section 2.15, added "(IKE_SA_INIT response)" after "of the second
|
||
message" and "(IKE_SA_INIT request)" after "the first message".
|
||
|
||
In Section 2.17, simplified because there are no more bundles. "A
|
||
single CHILD_SA negotiation may result in multiple security
|
||
associations. ESP and AH SAs exist in pairs (one in each
|
||
direction)." becomes "For ESP and AH, a single CHILD_SA negotiation
|
||
results in two security associations (one in each direction)."
|
||
|
||
In section 3.3, made the example of combinations of algorithms and
|
||
the contents of the first proposal clearer.
|
||
|
||
Added Clarif-4.4 to the ned of Section 3.3.2.
|
||
|
||
Reordered Section 3.3.5 and added Clarif-7.11.
|
||
|
||
Clarified Section 3.3.6 about choosing a single proposal. Also added
|
||
second paragraph about transforms not understood, and clarified third
|
||
paragraph about picking D-H groups.
|
||
|
||
Moved 3.10.1-16392 from Section 3.6 to 3.7.
|
||
|
||
In Section 3.10, clarified 3.10.1-16394.
|
||
|
||
Updated Section 6 to indicate that there is nothing new for IANA in
|
||
this spec. Also removed the definition of "Expert Review" from
|
||
Section 1.6 for the same reason.
|
||
|
||
In Appendix A, removed "and not commit any state to an exchange until
|
||
the initiator can be cryptographically authenticated" because that
|
||
was only true in an earlier version of IKEv2.
|
||
|
||
D.5. Changes from draft -02 to draft -03
|
||
|
||
In Section 1.3, changed "If the responder rejects the Diffie-Hellman
|
||
group of the KEi payload, the responder MUST reject the request and
|
||
indicate its preferred Diffie-Hellman group in the INVALID_KE_PAYLOAD
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 125]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Notification payload." to "If the responder selects a proposal using
|
||
a different Diffie-Hellman group (other than NONE), the responder
|
||
MUST reject the request and indicate its preferred Diffie-Hellman
|
||
group in the INVALID_KE_PAYLOAD Notification payload.
|
||
|
||
In Section 2.3, added the last two paragraphs covering why you
|
||
initiator's SPI and/or IP to differentiate if this is a "half-open"
|
||
IKE_SA or a new request. Also removed similar text from Section 2.2.
|
||
|
||
In Section 2.5, added "Payloads sent in IKE response messages MUST
|
||
NOT have the critical flag set. Note that the critical flag applies
|
||
only to the payload type, not the contents. If the payload type is
|
||
recognized, but the payload contains something which is not (such as
|
||
an unknown transform inside an SA payload, or an unknown Notify
|
||
Message Type inside a Notify payload), the critical flag is ignored."
|
||
|
||
In Section 2.6, moved the text about {{ 3.10.1-16390 }} later in the
|
||
section. Also reworded the text to make it clearer what the COOKIE
|
||
is for.
|
||
|
||
Moved text from {{ Clarif-2.1 }} from Section 2.6 to Section 2.7.
|
||
|
||
In Section 2.13, added "(see Section 3.3.5 for the defintion of the
|
||
Key Length transform attribute)".
|
||
|
||
In Section 2.17, change the description of the keying material from
|
||
the list with two bullets to a clearer list.
|
||
|
||
In Section 2.23, added "Implementations MUST process received UDP-
|
||
encapsulated ESP packets even when no NAT was detected."
|
||
|
||
In Section 3.3, changed "Each proposal may contain a" to "Each
|
||
proposal contains a".
|
||
|
||
Added the asterisks to the tranform type table in Section 3.3.2 and
|
||
the types table in 3.3.3 to foreshadow future developments.
|
||
|
||
In Section 3.3.2, changed the following algorithms to (UNSPECIFIED)
|
||
because the RFCs listed didn't really specify how to implement them
|
||
in an interoperable fashion:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 126]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Encryption Algorithms
|
||
ENCR_DES_IV64 1 (RFC1827)
|
||
ENCR_3IDEA 8 (RFC2451)
|
||
ENCR_DES_IV32 9
|
||
Pseudo-random Functions
|
||
PRF_HMAC_TIGER 3 (RFC2104)
|
||
Integrity Algorithms
|
||
AUTH_DES_MAC 3
|
||
AUTH_KPDK_MD5 4 (RFC1826)
|
||
|
||
In Section 3.4, added "(other than NONE)" to the second-to-last
|
||
paragraph.
|
||
|
||
Rewrote the third paragraph of Section 3.14 to talk about other
|
||
modes, and to clarify which encryption and integrity protection we
|
||
are talking about.
|
||
|
||
Changed the "Initialization Vector" bullet in Section 3.14 to specify
|
||
better what is needed for the IV. Upgraded the SHOULDs to MUSTs.
|
||
Also added the reference for [MODES].
|
||
|
||
In Section 5, in the second-to-last paragraph, changed "a public-key-
|
||
based" to "strong" to match the wording in Section 2.16.
|
||
|
||
|
||
Authors' Addresses
|
||
|
||
Charlie Kaufman
|
||
Microsoft
|
||
1 Microsoft Way
|
||
Redmond, WA 98052
|
||
US
|
||
|
||
Phone: 1-425-707-3335
|
||
Email: charliek@microsoft.com
|
||
|
||
|
||
Paul Hoffman
|
||
VPN Consortium
|
||
127 Segre Place
|
||
Santa Cruz, CA 95060
|
||
US
|
||
|
||
Phone: 1-831-426-9827
|
||
Email: paul.hoffman@vpnc.org
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 127]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Pasi Eronen
|
||
Nokia Research Center
|
||
P.O. Box 407
|
||
FIN-00045 Nokia Group
|
||
Finland
|
||
|
||
Email: pasi.eronen@nokia.com
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 128]
|
||
|
||
Internet-Draft IKEv2bis February 2008
|
||
|
||
|
||
Full Copyright Statement
|
||
|
||
Copyright (C) The IETF Trust (2008).
|
||
|
||
This document is subject to the rights, licenses and restrictions
|
||
contained in BCP 78, and except as set forth therein, the authors
|
||
retain all their rights.
|
||
|
||
This document and the information contained herein are provided on an
|
||
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
|
||
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
|
||
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
|
||
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
|
||
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
|
||
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
|
||
|
||
|
||
Intellectual Property
|
||
|
||
The IETF takes no position regarding the validity or scope of any
|
||
Intellectual Property Rights or other rights that might be claimed to
|
||
pertain to the implementation or use of the technology described in
|
||
this document or the extent to which any license under such rights
|
||
might or might not be available; nor does it represent that it has
|
||
made any independent effort to identify any such rights. Information
|
||
on the procedures with respect to rights in RFC documents can be
|
||
found in BCP 78 and BCP 79.
|
||
|
||
Copies of IPR disclosures made to the IETF Secretariat and any
|
||
assurances of licenses to be made available, or the result of an
|
||
attempt made to obtain a general license or permission for the use of
|
||
such proprietary rights by implementers or users of this
|
||
specification can be obtained from the IETF on-line IPR repository at
|
||
http://www.ietf.org/ipr.
|
||
|
||
The IETF invites any interested party to bring to its attention any
|
||
copyrights, patents or patent applications, or other proprietary
|
||
rights that may cover technology that may be required to implement
|
||
this standard. Please address the information to the IETF at
|
||
ietf-ipr@ietf.org.
|
||
|
||
|
||
Acknowledgment
|
||
|
||
Funding for the RFC Editor function is provided by the IETF
|
||
Administrative Support Activity (IASA).
|
||
|
||
|
||
|
||
|
||
|
||
Kaufman, et al. Expires August 28, 2008 [Page 129]
|
||
|