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| author | Tobias Brunner <tobias@strongswan.org> | 2011-07-20 15:57:29 +0200 |
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| committer | Tobias Brunner <tobias@strongswan.org> | 2011-07-20 15:57:29 +0200 |
| commit | 20a44a5c66960db55803e8a24a3f855a7462adf1 (patch) | |
| tree | 21f54be88fb5d06dedf69e2cb9f55794d4905c54 /doc | |
| parent | 355728110a0f319bc38673cea0fc9e95de1b106e (diff) | |
| download | strongswan-20a44a5c66960db55803e8a24a3f855a7462adf1.tar.bz2 strongswan-20a44a5c66960db55803e8a24a3f855a7462adf1.tar.xz | |
Removed old ikev2bis draft.
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/standards/draft-hoffman-ikev2bis-03.txt | 7224 |
1 files changed, 0 insertions, 7224 deletions
diff --git a/doc/standards/draft-hoffman-ikev2bis-03.txt b/doc/standards/draft-hoffman-ikev2bis-03.txt deleted file mode 100644 index 4cf8bf1b6..000000000 --- a/doc/standards/draft-hoffman-ikev2bis-03.txt +++ /dev/null @@ -1,7224 +0,0 @@ - - - -Network Working Group C. Kaufman -Internet-Draft Microsoft -Obsoletes: 4306, 4718 P. Hoffman -(if approved) VPN Consortium -Intended status: Standards Track P. Eronen -Expires: August 28, 2008 Nokia - February 25, 2008 - - - Internet Key Exchange Protocol: IKEv2 - draft-hoffman-ikev2bis-03 - -Status of this Memo - - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on August 28, 2008. - -Copyright Notice - - Copyright (C) The IETF Trust (2008). - -Abstract - - This document describes version 2 of the Internet Key Exchange (IKE) - protocol. It is a restatement of RFC 4306, and includes all of the - clarifications from RFC 4718. - - - - - -Kaufman, et al. Expires August 28, 2008 [Page 1] - -Internet-Draft IKEv2bis February 2008 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 - 1.1. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . 6 - 1.1.1. Security Gateway to Security Gateway Tunnel . . . . . 6 - 1.1.2. Endpoint-to-Endpoint Transport . . . . . . . . . . . 7 - 1.1.3. Endpoint to Security Gateway Tunnel . . . . . . . . . 8 - 1.1.4. Other Scenarios . . . . . . . . . . . . . . . . . . . 8 - 1.2. The Initial Exchanges . . . . . . . . . . . . . . . . . . 9 - 1.3. The CREATE_CHILD_SA Exchange . . . . . . . . . . . . . . 11 - 1.3.1. Creating New CHILD_SAs with the CREATE_CHILD_SA - Exchange . . . . . . . . . . . . . . . . . . . . . . 13 - 1.3.2. Rekeying IKE_SAs with the CREATE_CHILD_SA Exchange . 14 - 1.3.3. Rekeying CHILD_SAs with the CREATE_CHILD_SA - Exchange . . . . . . . . . . . . . . . . . . . . . . 14 - 1.4. The INFORMATIONAL Exchange . . . . . . . . . . . . . . . 15 - 1.5. Informational Messages outside of an IKE_SA . . . . . . . 17 - 1.6. Requirements Terminology . . . . . . . . . . . . . . . . 17 - 1.7. Differences Between RFC 4306 and This Document . . . . . 18 - 2. IKE Protocol Details and Variations . . . . . . . . . . . . . 19 - 2.1. Use of Retransmission Timers . . . . . . . . . . . . . . 20 - 2.2. Use of Sequence Numbers for Message ID . . . . . . . . . 21 - 2.3. Window Size for Overlapping Requests . . . . . . . . . . 21 - 2.4. State Synchronization and Connection Timeouts . . . . . . 23 - 2.5. Version Numbers and Forward Compatibility . . . . . . . . 25 - 2.6. Cookies . . . . . . . . . . . . . . . . . . . . . . . . . 27 - 2.6.1. Interaction of COOKIE and INVALID_KE_PAYLOAD . . . . 29 - 2.7. Cryptographic Algorithm Negotiation . . . . . . . . . . . 30 - 2.8. Rekeying . . . . . . . . . . . . . . . . . . . . . . . . 31 - 2.8.1. Simultaneous CHILD_SA rekeying . . . . . . . . . . . 33 - 2.8.2. Rekeying the IKE_SA Versus Reauthentication . . . . . 35 - 2.9. Traffic Selector Negotiation . . . . . . . . . . . . . . 36 - 2.9.1. Traffic Selectors Violating Own Policy . . . . . . . 38 - 2.10. Nonces . . . . . . . . . . . . . . . . . . . . . . . . . 39 - 2.11. Address and Port Agility . . . . . . . . . . . . . . . . 39 - 2.12. Reuse of Diffie-Hellman Exponentials . . . . . . . . . . 40 - 2.13. Generating Keying Material . . . . . . . . . . . . . . . 40 - 2.14. Generating Keying Material for the IKE_SA . . . . . . . . 42 - 2.15. Authentication of the IKE_SA . . . . . . . . . . . . . . 42 - 2.16. Extensible Authentication Protocol Methods . . . . . . . 44 - 2.17. Generating Keying Material for CHILD_SAs . . . . . . . . 46 - 2.18. Rekeying IKE_SAs Using a CREATE_CHILD_SA Exchange . . . . 47 - 2.19. Requesting an Internal Address on a Remote Network . . . 48 - 2.19.1. Configuration Payloads . . . . . . . . . . . . . . . 49 - 2.20. Requesting the Peer's Version . . . . . . . . . . . . . . 51 - 2.21. Error Handling . . . . . . . . . . . . . . . . . . . . . 51 - 2.22. IPComp . . . . . . . . . . . . . . . . . . . . . . . . . 52 - 2.23. NAT Traversal . . . . . . . . . . . . . . . . . . . . . . 54 - - - -Kaufman, et al. Expires August 28, 2008 [Page 2] - -Internet-Draft IKEv2bis February 2008 - - - 2.24. Explicit Congestion Notification (ECN) . . . . . . . . . 57 - 3. Header and Payload Formats . . . . . . . . . . . . . . . . . 57 - 3.1. The IKE Header . . . . . . . . . . . . . . . . . . . . . 58 - 3.2. Generic Payload Header . . . . . . . . . . . . . . . . . 61 - 3.3. Security Association Payload . . . . . . . . . . . . . . 63 - 3.3.1. Proposal Substructure . . . . . . . . . . . . . . . . 65 - 3.3.2. Transform Substructure . . . . . . . . . . . . . . . 66 - 3.3.3. Valid Transform Types by Protocol . . . . . . . . . . 69 - 3.3.4. Mandatory Transform IDs . . . . . . . . . . . . . . . 70 - 3.3.5. Transform Attributes . . . . . . . . . . . . . . . . 71 - 3.3.6. Attribute Negotiation . . . . . . . . . . . . . . . . 73 - 3.4. Key Exchange Payload . . . . . . . . . . . . . . . . . . 73 - 3.5. Identification Payloads . . . . . . . . . . . . . . . . . 74 - 3.6. Certificate Payload . . . . . . . . . . . . . . . . . . . 77 - 3.7. Certificate Request Payload . . . . . . . . . . . . . . . 79 - 3.8. Authentication Payload . . . . . . . . . . . . . . . . . 81 - 3.9. Nonce Payload . . . . . . . . . . . . . . . . . . . . . . 82 - 3.10. Notify Payload . . . . . . . . . . . . . . . . . . . . . 83 - 3.10.1. Notify Message Types . . . . . . . . . . . . . . . . 84 - 3.11. Delete Payload . . . . . . . . . . . . . . . . . . . . . 87 - 3.12. Vendor ID Payload . . . . . . . . . . . . . . . . . . . . 89 - 3.13. Traffic Selector Payload . . . . . . . . . . . . . . . . 90 - 3.13.1. Traffic Selector . . . . . . . . . . . . . . . . . . 91 - 3.14. Encrypted Payload . . . . . . . . . . . . . . . . . . . . 93 - 3.15. Configuration Payload . . . . . . . . . . . . . . . . . . 95 - 3.15.1. Configuration Attributes . . . . . . . . . . . . . . 96 - 3.15.2. Meaning of INTERNAL_IP4_SUBNET/INTERNAL_IP6_SUBNET . 99 - 3.15.3. Configuration payloads for IPv6 . . . . . . . . . . . 101 - 3.15.4. Address Assignment Failures . . . . . . . . . . . . . 101 - 3.16. Extensible Authentication Protocol (EAP) Payload . . . . 102 - 4. Conformance Requirements . . . . . . . . . . . . . . . . . . 104 - 5. Security Considerations . . . . . . . . . . . . . . . . . . . 106 - 5.1. Traffic selector authorization . . . . . . . . . . . . . 108 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 109 - 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 110 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 110 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 110 - 8.2. Informative References . . . . . . . . . . . . . . . . . 112 - Appendix A. Summary of changes from IKEv1 . . . . . . . . . . . 115 - Appendix B. Diffie-Hellman Groups . . . . . . . . . . . . . . . 117 - B.1. Group 1 - 768 Bit MODP . . . . . . . . . . . . . . . . . 117 - B.2. Group 2 - 1024 Bit MODP . . . . . . . . . . . . . . . . . 117 - Appendix C. Exchanges and Payloads . . . . . . . . . . . . . . . 118 - C.1. IKE_SA_INIT Exchange . . . . . . . . . . . . . . . . . . 118 - C.2. IKE_AUTH Exchange without EAP . . . . . . . . . . . . . . 119 - C.3. IKE_AUTH Exchange with EAP . . . . . . . . . . . . . . . 120 - C.4. CREATE_CHILD_SA Exchange for Creating or Rekeying - CHILD_SAs . . . . . . . . . . . . . . . . . . . . . . . . 121 - - - -Kaufman, et al. Expires August 28, 2008 [Page 3] - -Internet-Draft IKEv2bis February 2008 - - - C.5. CREATE_CHILD_SA Exchange for Rekeying the IKE_SA . . . . 121 - C.6. INFORMATIONAL Exchange . . . . . . . . . . . . . . . . . 121 - Appendix D. Changes Between Internet Draft Versions . . . . . . 121 - D.1. Changes from IKEv2 to draft -00 . . . . . . . . . . . . . 121 - D.2. Changes from draft -00 to draft -01 . . . . . . . . . . . 122 - D.3. Changes from draft -00 to draft -01 . . . . . . . . . . . 124 - D.4. Changes from draft -01 to draft -02 . . . . . . . . . . . 124 - D.5. Changes from draft -02 to draft -03 . . . . . . . . . . . 125 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 127 - Intellectual Property and Copyright Statements . . . . . . . . . 129 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Kaufman, et al. Expires August 28, 2008 [Page 4] - -Internet-Draft IKEv2bis February 2008 - - -1. Introduction - - {{ An introduction to the differences between RFC 4306 [IKEV2] and - this document is given at the end of Section 1. It is put there - (instead of here) to preserve the section numbering of RFC 4306. }} - - IP Security (IPsec) provides confidentiality, data integrity, access - control, and data source authentication to IP datagrams. These - services are provided by maintaining shared state between the source - and the sink of an IP datagram. This state defines, among other - things, the specific services provided to the datagram, which - cryptographic algorithms will be used to provide the services, and - the keys used as input to the cryptographic algorithms. - - Establishing this shared state in a manual fashion does not scale - well. Therefore, a protocol to establish this state dynamically is - needed. This memo describes such a protocol -- the Internet Key - Exchange (IKE). Version 1 of IKE was defined in RFCs 2407 [DOI], - 2408 [ISAKMP], and 2409 [IKEV1]. IKEv2 was defined in [IKEV2] and - clarified in [Clarif]. This single document is intended to replace - all of those RFCs. - - IKE performs mutual authentication between two parties and - establishes an IKE security association (SA) that includes shared - secret information that can be used to efficiently establish SAs for - Encapsulating Security Payload (ESP) [ESP] and/or Authentication - Header (AH) [AH] and a set of cryptographic algorithms to be used by - the SAs to protect the traffic that they carry. In this document, - the term "suite" or "cryptographic suite" refers to a complete set of - algorithms used to protect an SA. An initiator proposes one or more - suites by listing supported algorithms that can be combined into - suites in a mix-and-match fashion. IKE can also negotiate use of IP - Compression (IPComp) [IPCOMP] in connection with an ESP and/or AH SA. - We call the IKE SA an "IKE_SA". The SAs for ESP and/or AH that get - set up through that IKE_SA we call "CHILD_SAs". - - All IKE communications consist of pairs of messages: a request and a - response. The pair is called an "exchange". We call the first - messages establishing an IKE_SA IKE_SA_INIT and IKE_AUTH exchanges - and subsequent IKE exchanges CREATE_CHILD_SA or INFORMATIONAL - exchanges. In the common case, there is a single IKE_SA_INIT - exchange and a single IKE_AUTH exchange (a total of four messages) to - establish the IKE_SA and the first CHILD_SA. In exceptional cases, - there may be more than one of each of these exchanges. In all cases, - all IKE_SA_INIT exchanges MUST complete before any other exchange - type, then all IKE_AUTH exchanges MUST complete, and following that - any number of CREATE_CHILD_SA and INFORMATIONAL exchanges may occur - in any order. In some scenarios, only a single CHILD_SA is needed - - - -Kaufman, et al. Expires August 28, 2008 [Page 5] - -Internet-Draft IKEv2bis February 2008 - - - between the IPsec endpoints, and therefore there would be no - additional exchanges. Subsequent exchanges MAY be used to establish - additional CHILD_SAs between the same authenticated pair of endpoints - and to perform housekeeping functions. - - IKE message flow always consists of a request followed by a response. - It is the responsibility of the requester to ensure reliability. If - the response is not received within a timeout interval, the requester - needs to retransmit the request (or abandon the connection). - - The first request/response of an IKE session (IKE_SA_INIT) negotiates - security parameters for the IKE_SA, sends nonces, and sends Diffie- - Hellman values. - - The second request/response (IKE_AUTH) transmits identities, proves - knowledge of the secrets corresponding to the two identities, and - sets up an SA for the first (and often only) AH and/or ESP CHILD_SA. - - The types of subsequent exchanges are CREATE_CHILD_SA (which creates - a CHILD_SA) and INFORMATIONAL (which deletes an SA, reports error - conditions, or does other housekeeping). Every request requires a - response. An INFORMATIONAL request with no payloads (other than the - empty Encrypted payload required by the syntax) is commonly used as a - check for liveness. These subsequent exchanges cannot be used until - the initial exchanges have completed. - - In the description that follows, we assume that no errors occur. - Modifications to the flow should errors occur are described in - Section 2.21. - -1.1. Usage Scenarios - - IKE is expected to be used to negotiate ESP and/or AH SAs in a number - of different scenarios, each with its own special requirements. - -1.1.1. Security Gateway to Security Gateway Tunnel - - +-+-+-+-+-+ +-+-+-+-+-+ - | | IPsec | | - Protected |Tunnel | tunnel |Tunnel | Protected - Subnet <-->|Endpoint |<---------->|Endpoint |<--> Subnet - | | | | - +-+-+-+-+-+ +-+-+-+-+-+ - - Figure 1: Security Gateway to Security Gateway Tunnel - - In this scenario, neither endpoint of the IP connection implements - IPsec, but network nodes between them protect traffic for part of the - - - -Kaufman, et al. Expires August 28, 2008 [Page 6] - -Internet-Draft IKEv2bis February 2008 - - - way. Protection is transparent to the endpoints, and depends on - ordinary routing to send packets through the tunnel endpoints for - processing. Each endpoint would announce the set of addresses - "behind" it, and packets would be sent in tunnel mode where the inner - IP header would contain the IP addresses of the actual endpoints. - -1.1.2. Endpoint-to-Endpoint Transport - - +-+-+-+-+-+ +-+-+-+-+-+ - | | IPsec transport | | - |Protected| or tunnel mode SA |Protected| - |Endpoint |<---------------------------------------->|Endpoint | - | | | | - +-+-+-+-+-+ +-+-+-+-+-+ - - Figure 2: Endpoint to Endpoint - - In this scenario, both endpoints of the IP connection implement - IPsec, as required of hosts in [IPSECARCH]. Transport mode will - commonly be used with no inner IP header. If there is an inner IP - header, the inner addresses will be the same as the outer addresses. - A single pair of addresses will be negotiated for packets to be - protected by this SA. These endpoints MAY implement application - layer access controls based on the IPsec authenticated identities of - the participants. This scenario enables the end-to-end security that - has been a guiding principle for the Internet since [ARCHPRINC], - [TRANSPARENCY], and a method of limiting the inherent problems with - complexity in networks noted by [ARCHGUIDEPHIL]. Although this - scenario may not be fully applicable to the IPv4 Internet, it has - been deployed successfully in specific scenarios within intranets - using IKEv1. It should be more broadly enabled during the transition - to IPv6 and with the adoption of IKEv2. - - It is possible in this scenario that one or both of the protected - endpoints will be behind a network address translation (NAT) node, in - which case the tunneled packets will have to be UDP encapsulated so - that port numbers in the UDP headers can be used to identify - individual endpoints "behind" the NAT (see Section 2.23). - - - - - - - - - - - - - -Kaufman, et al. Expires August 28, 2008 [Page 7] - -Internet-Draft IKEv2bis February 2008 - - -1.1.3. Endpoint to Security Gateway Tunnel - - +-+-+-+-+-+ +-+-+-+-+-+ - | | IPsec | | Protected - |Protected| tunnel |Tunnel | Subnet - |Endpoint |<------------------------>|Endpoint |<--- and/or - | | | | Internet - +-+-+-+-+-+ +-+-+-+-+-+ - - Figure 3: Endpoint to Security Gateway Tunnel - - In this scenario, a protected endpoint (typically a portable roaming - computer) connects back to its corporate network through an IPsec- - protected tunnel. It might use this tunnel only to access - information on the corporate network, or it might tunnel all of its - traffic back through the corporate network in order to take advantage - of protection provided by a corporate firewall against Internet-based - attacks. In either case, the protected endpoint will want an IP - address associated with the security gateway so that packets returned - to it will go to the security gateway and be tunneled back. This IP - address may be static or may be dynamically allocated by the security - gateway. {{ Clarif-6.1 }} In support of the latter case, IKEv2 - includes a mechanism (namely, configuration payloads) for the - initiator to request an IP address owned by the security gateway for - use for the duration of its SA. - - In this scenario, packets will use tunnel mode. On each packet from - the protected endpoint, the outer IP header will contain the source - IP address associated with its current location (i.e., the address - 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. 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