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+Network Working Group C. Kaufman
+Internet-Draft Microsoft
+Obsoletes: 4306, 4718 P. Hoffman
+(if approved) VPN Consortium
+Intended status: Standards Track Y. Nir
+Expires: May 3, 2009 Check Point
+ P. Eronen
+ Nokia
+ October 30, 2008
+
+
+ Internet Key Exchange Protocol: IKEv2
+ draft-ietf-ipsecme-ikev2bis-01
+
+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 May 3, 2009.
+
+Copyright Notice
+
+ Copyright (C) The IETF Trust (2008).
+
+Abstract
+
+ This document describes version 2 of the Internet Key Exchange (IKE)
+ protocol. IKE is a component of IPsec used for performing mutual
+ authentication and establishing and maintaining security associations
+
+
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+ (SAs). It replaces and updates RFC 4306, and includes all of the
+ clarifications from RFC 4718.
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
+ 1.1. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . 6
+ 1.1.1. Security Gateway to Security Gateway Tunnel Mode . . 6
+ 1.1.2. Endpoint-to-Endpoint Transport Mode . . . . . . . . . 7
+ 1.1.3. Endpoint to Security Gateway Tunnel Mode . . . . . . 8
+ 1.1.4. Other Scenarios . . . . . . . . . . . . . . . . . . . 8
+ 1.2. The Initial Exchanges . . . . . . . . . . . . . . . . . . 9
+ 1.3. The CREATE_CHILD_SA Exchange . . . . . . . . . . . . . . 12
+ 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 . . . . . . . . . . . . . . . . . . . . . . 15
+ 1.4. The INFORMATIONAL Exchange . . . . . . . . . . . . . . . 16
+ 1.4.1. Deleting an SA with INFORMATIONAL Exchanges . . . . . 16
+ 1.5. Informational Messages outside of an IKE SA . . . . . . . 17
+ 1.6. Requirements Terminology . . . . . . . . . . . . . . . . 18
+ 1.7. Differences Between RFC 4306 and This Document . . . . . 18
+ 2. IKE Protocol Details and Variations . . . . . . . . . . . . . 20
+ 2.1. Use of Retransmission Timers . . . . . . . . . . . . . . 21
+ 2.2. Use of Sequence Numbers for Message ID . . . . . . . . . 22
+ 2.3. Window Size for Overlapping Requests . . . . . . . . . . 22
+ 2.4. State Synchronization and Connection Timeouts . . . . . . 24
+ 2.5. Version Numbers and Forward Compatibility . . . . . . . . 26
+ 2.6. IKE SA SPIs and Cookies . . . . . . . . . . . . . . . . . 28
+ 2.6.1. Interaction of COOKIE and INVALID_KE_PAYLOAD . . . . 30
+ 2.7. Cryptographic Algorithm Negotiation . . . . . . . . . . . 31
+ 2.8. Rekeying . . . . . . . . . . . . . . . . . . . . . . . . 32
+ 2.8.1. Simultaneous Child SA rekeying . . . . . . . . . . . 34
+ 2.8.2. Rekeying the IKE SA Versus Reauthentication . . . . . 36
+ 2.9. Traffic Selector Negotiation . . . . . . . . . . . . . . 37
+ 2.9.1. Traffic Selectors Violating Own Policy . . . . . . . 40
+ 2.10. Nonces . . . . . . . . . . . . . . . . . . . . . . . . . 40
+ 2.11. Address and Port Agility . . . . . . . . . . . . . . . . 41
+ 2.12. Reuse of Diffie-Hellman Exponentials . . . . . . . . . . 41
+ 2.13. Generating Keying Material . . . . . . . . . . . . . . . 42
+ 2.14. Generating Keying Material for the IKE SA . . . . . . . . 43
+ 2.15. Authentication of the IKE SA . . . . . . . . . . . . . . 44
+ 2.16. Extensible Authentication Protocol Methods . . . . . . . 46
+ 2.17. Generating Keying Material for Child SAs . . . . . . . . 48
+ 2.18. Rekeying IKE SAs Using a CREATE_CHILD_SA Exchange . . . . 49
+ 2.19. Requesting an Internal Address on a Remote Network . . . 50
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+ 2.19.1. Configuration Payloads . . . . . . . . . . . . . . . 51
+ 2.20. Requesting the Peer's Version . . . . . . . . . . . . . . 53
+ 2.21. Error Handling . . . . . . . . . . . . . . . . . . . . . 53
+ 2.22. IPComp . . . . . . . . . . . . . . . . . . . . . . . . . 54
+ 2.23. NAT Traversal . . . . . . . . . . . . . . . . . . . . . . 55
+ 2.24. Explicit Congestion Notification (ECN) . . . . . . . . . 59
+ 3. Header and Payload Formats . . . . . . . . . . . . . . . . . 59
+ 3.1. The IKE Header . . . . . . . . . . . . . . . . . . . . . 59
+ 3.2. Generic Payload Header . . . . . . . . . . . . . . . . . 62
+ 3.3. Security Association Payload . . . . . . . . . . . . . . 64
+ 3.3.1. Proposal Substructure . . . . . . . . . . . . . . . . 66
+ 3.3.2. Transform Substructure . . . . . . . . . . . . . . . 68
+ 3.3.3. Valid Transform Types by Protocol . . . . . . . . . . 71
+ 3.3.4. Mandatory Transform IDs . . . . . . . . . . . . . . . 71
+ 3.3.5. Transform Attributes . . . . . . . . . . . . . . . . 72
+ 3.3.6. Attribute Negotiation . . . . . . . . . . . . . . . . 74
+ 3.4. Key Exchange Payload . . . . . . . . . . . . . . . . . . 75
+ 3.5. Identification Payloads . . . . . . . . . . . . . . . . . 75
+ 3.6. Certificate Payload . . . . . . . . . . . . . . . . . . . 78
+ 3.7. Certificate Request Payload . . . . . . . . . . . . . . . 80
+ 3.8. Authentication Payload . . . . . . . . . . . . . . . . . 82
+ 3.9. Nonce Payload . . . . . . . . . . . . . . . . . . . . . . 83
+ 3.10. Notify Payload . . . . . . . . . . . . . . . . . . . . . 84
+ 3.10.1. Notify Message Types . . . . . . . . . . . . . . . . 85
+ 3.11. Delete Payload . . . . . . . . . . . . . . . . . . . . . 88
+ 3.12. Vendor ID Payload . . . . . . . . . . . . . . . . . . . . 90
+ 3.13. Traffic Selector Payload . . . . . . . . . . . . . . . . 91
+ 3.13.1. Traffic Selector . . . . . . . . . . . . . . . . . . 92
+ 3.14. Encrypted Payload . . . . . . . . . . . . . . . . . . . . 94
+ 3.15. Configuration Payload . . . . . . . . . . . . . . . . . . 96
+ 3.15.1. Configuration Attributes . . . . . . . . . . . . . . 97
+ 3.15.2. Meaning of INTERNAL_IP4_SUBNET/INTERNAL_IP6_SUBNET . 100
+ 3.15.3. Configuration payloads for IPv6 . . . . . . . . . . . 102
+ 3.15.4. Address Assignment Failures . . . . . . . . . . . . . 103
+ 3.16. Extensible Authentication Protocol (EAP) Payload . . . . 103
+ 4. Conformance Requirements . . . . . . . . . . . . . . . . . . 105
+ 5. Security Considerations . . . . . . . . . . . . . . . . . . . 107
+ 5.1. Traffic selector authorization . . . . . . . . . . . . . 109
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 111
+ 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 111
+ 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 111
+ 8.1. Normative References . . . . . . . . . . . . . . . . . . 111
+ 8.2. Informative References . . . . . . . . . . . . . . . . . 113
+ Appendix A. Summary of changes from IKEv1 . . . . . . . . . . . 117
+ Appendix B. Diffie-Hellman Groups . . . . . . . . . . . . . . . 118
+ B.1. Group 1 - 768 Bit MODP . . . . . . . . . . . . . . . . . 118
+ B.2. Group 2 - 1024 Bit MODP . . . . . . . . . . . . . . . . . 118
+ Appendix C. Exchanges and Payloads . . . . . . . . . . . . . . . 119
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+ C.1. IKE_SA_INIT Exchange . . . . . . . . . . . . . . . . . . 119
+ C.2. IKE_AUTH Exchange without EAP . . . . . . . . . . . . . . 120
+ C.3. IKE_AUTH Exchange with EAP . . . . . . . . . . . . . . . 121
+ C.4. CREATE_CHILD_SA Exchange for Creating or Rekeying
+ Child SAs . . . . . . . . . . . . . . . . . . . . . . . . 122
+ C.5. CREATE_CHILD_SA Exchange for Rekeying the IKE SA . . . . 122
+ C.6. INFORMATIONAL Exchange . . . . . . . . . . . . . . . . . 122
+ Appendix D. Changes Between Internet Draft Versions . . . . . . 122
+ D.1. Changes from IKEv2 to draft -00 . . . . . . . . . . . . . 123
+ D.2. Changes from draft -00 to draft -01 . . . . . . . . . . . 123
+ D.3. Changes from draft -00 to draft -01 . . . . . . . . . . . 125
+ D.4. Changes from draft -01 to draft -02 . . . . . . . . . . . 126
+ D.5. Changes from draft -02 to draft -03 . . . . . . . . . . . 127
+ D.6. Changes from draft -03 to
+ draft-ietf-ipsecme-ikev2bis-00 . . . . . . . . . . . . . 128
+ D.7. Changes from draft-ietf-ipsecme-ikev2bis-00 to
+ draft-ietf-ipsecme-ikev2bis-01 . . . . . . . . . . . . . 129
+ Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 133
+ Intellectual Property and Copyright Statements . . . . . . . . . 134
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+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 replaced all of those RFCs.
+ IKEv2 was defined in [IKEV2] (RFC 4306) and was clarified in [Clarif]
+ (RFC 4718). This document replaces and updates RFC 4306 and RFC
+ 4718.
+
+ 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] 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) [IP-COMP] in connection with an ESP or AH SA.
+ The SAs for ESP 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
+
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+ in any order. In some scenarios, only a single Child SA is needed
+ 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 or ESP Child SA
+ (unless there is failure setting up the AH or ESP Child SA, in which
+ case the IKE SA is still established without IPsec 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 or AH SAs in a number of
+ different scenarios, each with its own special requirements.
+
+1.1.1. Security Gateway to Security Gateway Tunnel Mode
+
+ +-+-+-+-+-+ +-+-+-+-+-+
+ | | IPsec | |
+ Protected |Tunnel | tunnel |Tunnel | Protected
+ Subnet <-->|Endpoint |<---------->|Endpoint |<--> Subnet
+ | | | |
+ +-+-+-+-+-+ +-+-+-+-+-+
+
+ Figure 1: Security Gateway to Security Gateway Tunnel
+
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+ In this scenario, neither endpoint of the IP connection implements
+ IPsec, but network nodes between them protect traffic for part of the
+ 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 Mode
+
+ +-+-+-+-+-+ +-+-+-+-+-+
+ | | 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. 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).
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+1.1.3. Endpoint to Security Gateway Tunnel Mode
+
+ +-+-+-+-+-+ +-+-+-+-+-+
+ | | 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
+
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+ 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. (See Section 2.14 for information on
+ how the encyrption keys are generated.)
+
+ All messages following the initial exchange are cryptographically
+ protected using the cryptographic algorithms and keys negotiated in
+ the the IKE_SA_INIT exchange. These subsequent messages use the
+ syntax of the Encrypted Payload described in Section 3.14, encrypted
+ with keys that are derived as described in Section 2.14. All
+ subsequent messages include an Encrypted Payload, even if they are
+ referred to in the text as "empty". For the CREATE_CHILD_SA,
+ IKE_AUTH, or IKE_INFORMATIONAL exchanges, 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.
+
+ In the following descriptions, the payloads contained in the message
+ are indicated by names as listed below.
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+ 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
+
+ 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. The messages that
+ follow are encrypted and integrity protected in their entirety, with
+ the exception of the message headers. The keys used for the
+
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+ 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 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. If the IDr proposed by the
+ initiator is not acceptable to the responder, the responder might use
+ some other IDr to finish the exchange. If the initiator then does
+ not accept that fact that responder used different IDr than the one
+ that was requested, the initiator can close the SA after noticing the
+ fact.
+
+ 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.
+
+
+
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+
+
+ {{ 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
+ messages use the syntax of the Encrypted Payload described in
+ Section 3.14, encrypted with keys that are derived as described in
+ Section 2.14. 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.
+
+
+
+
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+
+
+ 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.
+
+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}
+
+
+
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+
+ 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.
+
+ {{ 3.10.1-16395 }} The NON_FIRST_FRAGMENTS_ALSO notification is used
+ for fragmentation control. See [IPSECARCH] for a fuller explanation.
+ {{ Clarif-4.6 }} Both parties need to agree to sending non-first
+ fragments before either party does so. It 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 responder does
+ not want to send or receive non-first fragments, it only omits
+ NON_FIRST_FRAGMENTS_ALSO notification from its 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
+
+
+
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+
+
+ payload SHOULD be included. New initiator and responder SPIs are
+ supplied in the SPI fields of the SA payload.
+
+ 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.
+
+ {{ 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 Protocol ID
+ field of the REKEY_SA notification is set to match the protocol of
+ the SA we are rekeying, for example, 3 for ESP and 2 for AH.
+
+ The CREATE_CHILD_SA response for rekeying a 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.
+
+
+
+
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+
+
+ 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 rekeyed).
+
+ 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.
+
+ 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.
+
+1.4.1. Deleting an SA with INFORMATIONAL Exchanges
+
+ {{ 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.
+ 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
+
+
+
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+
+
+ 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 the 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.
+
+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
+
+
+
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+
+
+ 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 is copied. The Response
+ bit is set to 1, and the version flags are set in the normal fashion.
+
+ 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. The Initiator flag
+ is set, the Response bit is set to 0, and the version flags are set
+ in the normal fashion.
+
+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].
+
+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
+
+
+
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+
+
+ 4306. That is, the version number is *not* changed from 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 document. 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
+ 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
+
+
+
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+
+
+ 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
+ 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.
+
+
+
+
+
+
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+
+
+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. A retransmission from the initiator
+ MUST be bitwise identical to the original request. That is,
+ everything starting from the IKE Header (the IKE SA Initiator's SPI
+ onwards) must be bitwise identical; items before it (such as the IP
+ and UDP headers, and the zero non-ESP marker) do not have to be
+ identical.
+
+ {{ 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).
+
+ 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.
+
+
+
+
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+
+
+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. Rekeying an IKE SA
+ resets the sequence numbers. 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.
+
+ {{ 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.
+
+ 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 or rekeyed.
+
+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
+
+
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+ 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.
+
+ 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
+
+
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+
+ 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.
+
+ {{ 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
+
+
+
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+ 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
+ (fresh, i.e. not retransmitted) 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.
+ (This is sometimes called "dead peer detection" or "DPD", although it
+ is really detecting live peers, not dead ones.) 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
+
+
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+ 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.
+ {{ 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 replacement for
+ [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
+
+
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+ 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.
+
+ 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.
+
+ {{ 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.
+
+
+
+
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+
+2.6. IKE SA SPIs and 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. Each
+ endpoint chooses one of the two SPIs and MUST 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.
+
+ Incoming IKE packets are mapped to an IKE SA only using the packet's
+ SPI, not using (for example) the source IP address of the packet.
+
+ 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:
+
+
+
+
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+ 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 can 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
+
+
+
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+ 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. The initiator should limit the number of
+ cookie exchanges it tries before giving up. An attacker can forge
+ multiple cookie responses to the initiator's IKE_SA_INIT message, and
+ each of those forged cookie reply will trigger two packets: one
+ packet from the initiator to the responder (which will reject those
+ cookies), and one reply from responder to initiator that includes the
+ correct 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.
+
+
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+ If both peers support including the cookie in all retries, a slightly
+ shorter exchange can happen.
+
+ Initiator Responder
+ -----------------------------------------------------------
+ HDR(A,0), SAi1, KEi, Ni -->
+ <-- HDR(A,0), N(COOKIE)
+ HDR(A,0), N(COOKIE), SAi1, KEi, Ni -->
+ <-- HDR(A,0), N(INVALID_KE_PAYLOAD)
+ HDR(A,0), N(COOKIE), SAi1, KEi', Ni -->
+ <-- HDR(A,B), SAr1, KEr, Nr
+
+ Implementations SHOULD support this shorter exchange, but MUST NOT
+ fail if other implementations do not support this shorter exchange.
+
+2.7. Cryptographic Algorithm Negotiation
+
+ The payload type known as "SA" indicates a proposal for a set of
+ choices of IPsec protocols (IKE, ESP, 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.
+
+
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+ If an initiator proposes both normal ciphers with integrity
+ protection as well as combined-mode ciphers, then two proposals are
+ needed. One of the proposals includes the normal ciphers with the
+ integrity algoritms for them, and the other proposal includes all the
+ combined mode ciphers without the integrity algorithms (because
+ combined mode ciphers are not allowed to have any integrity algorithm
+ other than "none").
+
+ 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,
+ 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,
+
+
+
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+
+
+ 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. Note that, when rekeying, the new Child SA MAY have
+ different traffic selectors and algorithms than the old one.
+
+ {{ 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
+ 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
+
+
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+ 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.
+
+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
+
+
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+ 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.
+
+ 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.
+
+
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+ 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
+
+ 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.
+
+
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+ 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
+ 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 that 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, although it only applies to IKEv1), 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)
+
+
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+ 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
+ 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).
+ If the type of traffic selector proposed is unknown, the responder
+ ignores that traffic selector, so that the unknown type is not be
+ returned in the narrowed 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 }}
+
+
+
+
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+ 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
+ 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
+
+
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+ 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. If you use decorrelated
+ policies from [IPSECARCH], this kind of policy violations cannot
+ happen.
+
+ 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
+ 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-
+
+
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+ 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
+ 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.
+
+ 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
+
+
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+ 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
+ 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)
+
+
+
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+ 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.
+
+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
+
+
+
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+
+
+ 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
+ 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:
+
+
+
+
+
+
+
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+
+ 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 | RespIDData
+ 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 multiple times (such as with a
+ responder cookie and/or a different Diffie-Hellman group), it is the
+ latest 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
+ 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
+
+
+
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+
+ 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. For
+ this reason, these protocols are typically used to authenticate the
+ initiator to the responder and MUST be used in conjunction with a
+ public key signature based authentication of the responder to the
+ 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:
+
+
+
+
+
+
+
+
+
+
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+
+ 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. This
+ shared key generated during an IKE exchange MUST NOT be used for any
+ other purpose.
+
+ 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
+
+
+
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+
+ 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:
+
+ 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.
+
+
+
+
+
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+
+ 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
+ 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 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.
+
+
+
+
+
+
+
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+
+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
+ 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.
+
+ 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:
+
+
+
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+
+ 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.
+
+ {{ 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.
+
+ 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. The
+ FAILED_CP_REQUIRED is not fatal to the IKE SA; it simply causes the
+ Child SA creation fail. The initiator can fix this by later starting
+ a new configuration payload request.
+
+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.
+
+ 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
+
+
+
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+
+ 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
+ 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
+
+
+
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+
+ 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
+ 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
+
+
+
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+
+ 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 [IP-COMP] 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
+ "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.
+
+
+
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+
+
+ {{ 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.
+
+ In some cases, Robust Header Compression (ROHC) may be more
+ appropriate than IP Compression. [ROHCV2] defines the use of ROHC
+ with IKEv2 and IPsec.
+
+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
+
+
+
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+
+
+ 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 will use 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
+ 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
+ or 4500, 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. {{ Clarif-7.6
+ }} An IPsec endpoint that discovers a NAT between it and its
+ correspondent MUST send all subsequent traffic from port 4500, which
+
+
+
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+
+
+ 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
+ is 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.
+
+ 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
+
+
+
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+
+
+ 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
+ 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.
+
+
+
+
+
+
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+
+
+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.
+
+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
+
+
+
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+
+ 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.
+
+ 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
+
+
+
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+
+ 1. Implementations based on this version of IKE MUST reject or
+ ignore messages containing a version number greater than 2 with an
+ INVALID_MAJOR_VERSION notification message as described in Section
+ 2.5.
+
+ 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 in an
+ exchange.
+
+ 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 is 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. This bit changes to reflect
+ who initiated the last rekey of the IKE SA.
+
+ * 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.
+
+
+
+
+
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+
+ * 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.
+
+ 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:
+
+
+
+
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+
+ 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.
+
+
+
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+
+
+ {{ 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). One reason
+ to use multiple proposals is to propose both standard crypto ciphers
+ and combined-mode ciphers. Combined-mode ciphers include both
+ integrity and encryption in a single encryption algorithm, and are
+ not allowed to be offered with a separate integrity algorithm other
+ than "none". If an initiator wants to propose both combined-mode
+ ciphers and normal ciphers, it must include two proposals: one will
+ have all the combined-mode ciphers, and the other will have all the
+ normal ciphers with the integrity algorithms. For example, one such
+
+
+
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+
+ proposal would have two proposal structures: ESP with ENCR_AES-CCM_8,
+ ENCR_AES-CCM_12, and ENCR_AES-CCM_16 as Proposal #1, and ESP with
+ ENCR_AES_CBC, ENCR_3DES, AUTH_AES_XCBC_96, and AUTH_HMAC_SHA1_96 as
+ 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
+ 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.
+
+
+
+
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+
+ 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> ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ 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.
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 66]
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+
+
+ 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:
+
+ 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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+\f
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+
+
+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
+ transform could be identified from the length of the proposal.
+ 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.
+
+ 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 transform type values are:
+
+
+
+
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 68]
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+
+
+ 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. For example,
+ [AEAD] specifies additional formats based on authenticated
+ encryption, in which a separate integrity algorithm is not
+ negotiated.
+
+ For Transform Type 1 (Encryption Algorithm), defined Transform IDs
+ are:
+
+ 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:
+
+
+
+
+
+
+
+
+
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+
+
+ Name Number Defined In
+ ------------------------------------------------------
+ RESERVED 0
+ PRF_HMAC_MD5 1 (RFC2104), [MD5]
+ PRF_HMAC_SHA1 2 (RFC2104), [SHA]
+ PRF_HMAC_TIGER 3 (RFC2104)
+ 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:
+
+ 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:
+
+
+
+
+
+
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+
+
+ 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.
+
+ Numerous additional transform types have been defined since the
+ publication of RFC 4306. Please refer to the IANA IKEv2 registry for
+ details.
+
+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.
+
+ 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. For example,
+ [AEAD] specifies additional formats based on authenticated
+ encryption, in which 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.
+
+
+
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+
+
+ 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
+ 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
+
+
+
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+
+
+ 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-
+ 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
+
+
+
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+
+
+ 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
+ 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
+
+
+
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+
+
+ 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.
+
+ 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
+
+
+
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+
+
+ 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:
+
+ 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:
+
+
+
+
+
+
+
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+
+
+ 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. Because of [EAI], implementations would
+ be wise to treat this field as UTF-8 encoded text, not as
+ pure ASCII.
+
+ 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
+
+
+
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+
+
+ MUST be configurable to accept all of these types. Implementations
+ SHOULD be capable of generating and accepting all of these types.
+ 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.
+
+
+
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+
+
+ 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 UNSPECIFIED
+ SPKI Certificate 9 UNSPECIFIED
+ X.509 Certificate - Attribute 10 UNSPECIFIED
+ 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 May 3, 2009 [Page 79]
+\f
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+
+
+ 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 certificate encoding does not allow a list, then
+ multiple Certificate Request payloads would need to be transmitted.
+
+ The Certificate Request Payload is defined as follows:
+
+
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 80]
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+
+
+ 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"
+
+
+
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+
+
+ 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 May 3, 2009 [Page 82]
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+
+
+ 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 May 3, 2009 [Page 83]
+\f
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+
+
+ 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 May 3, 2009 [Page 84]
+\f
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+
+
+ 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 and
+ the field must be empty.
+
+ 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
+
+
+
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+
+
+ managing an SA database wishes to communicate with a peer process.
+ 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
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 86]
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+
+
+ See Section 1.5.
+
+ 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
+
+
+
+
+
+
+
+
+
+
+
+
+
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+\f
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+
+
+ 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
+
+
+
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+
+
+ 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).
+
+
+
+
+
+
+
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+\f
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+
+
+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 May 3, 2009 [Page 90]
+\f
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+
+
+ 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.
+
+
+
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+
+
+ 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.
+
+
+
+
+
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+
+ 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 (including protocol 0), 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 (including protocol 0), 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.
+
+
+
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+
+
+ 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.
+
+
+
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+
+
+ 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 - For CBC mode ciphers, 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. For other modes than CBC, the IV format and processing is
+ specified in the document specifying the encryption algorithm and
+ mode. 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.
+
+
+
+
+
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+
+
+ 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.
+ 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.
+
+
+
+
+
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+
+
+ 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:
+
+
+
+
+
+
+
+
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+
+ 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. This is described in more detail in
+ Section 3.15.3.
+
+ 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
+
+
+
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+
+
+ as INTERNAL_IP4_SUBNET containing the same information ("send
+ 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. This is discussed in
+ more detail in Section 3.15.2.
+
+ 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.
+
+
+
+
+
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+
+
+ 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
+ prefix-length as defined in [ADDRIPV6]. Multiple sub-networks MAY
+ be requested. The responder MAY respond with zero or more sub-
+ network attributes. This is discussed in more detail in Section
+ 3.15.2.
+
+ 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))
+
+
+
+
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+
+
+ In these cases, the INTERNAL_IP4_SUBNET does not really carry any
+ useful information.
+
+ A different possible reply would have been this:
+
+ 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)
+
+
+
+
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+
+
+ Because the meaning of INTERNAL_IP4_SUBNET/INTERNAL_IP6_SUBNET is in
+ CFG_REQUESTs is unclear, they cannot be used reliably in
+ CFG_REQUESTs.
+
+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].
+
+
+
+
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+
+
+3.15.4. Address Assignment Failures
+
+ {{ Added this section from Clarif-6.8 }}
+
+ 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.
+ The IKE SA is still created even if the initial Child SA cannot be
+ created because of this failure. {{ 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 ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+
+
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+
+
+ Figure 24: EAP Payload Format
+
+ The payload type for an EAP Payload is forty eight (48).
+
+ 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
+
+
+
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+
+
+ responder should not send EAP Identity requests. The initiator may,
+ however, respond to such requests if it receives them.
+
+
+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 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 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
+
+
+
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+
+
+ 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 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.
+
+
+
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+
+
+ o Authentication where the responder is authenticated using PKIX
+ Certificates and the initiator is authenticated using shared key
+ authentication.
+
+
+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
+
+
+
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+
+
+ 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.
+
+ It is assumed that all Diffie-Hellman exponents are erased from
+ memory 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
+
+
+
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+
+
+ 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-
+ 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 authentication. {{ 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 authentication 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
+
+
+
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+
+
+ selectors.
+
+ For example, the PAD might be configured so that authenticated
+ identity "sgw23.example.com" is allowed to create IPsec SAs for
+ 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.
+
+
+
+
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+
+
+6. IANA Considerations
+
+ {{ This section was changed to not re-define any new IANA registries.
+ }}
+
+ [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. The RFC Editor will
+ remove it before publication. [AEAD] [EAI] [DES] [IDEA] [MD5]
+ [X.501] [X.509]
+
+
+8. References
+
+8.1. Normative References
+
+ [ADDGROUP]
+ Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 111]
+\f
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+
+
+ Diffie-Hellman groups for Internet Key Exchange (IKE)",
+ RFC 3526, May 2003.
+
+ [ADDRIPV6]
+ 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",
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 112]
+\f
+Internet-Draft IKEv2bis October 2008
+
+
+ RFC 3948, January 2005.
+
+8.2. Informative References
+
+ [AEAD] McGrew, D., "An Interface and Algorithms for Authenticated
+ Encryption", RFC 5116, January 2008.
+
+ [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
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 113]
+\f
+Internet-Draft IKEv2bis October 2008
+
+
+ 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
+ Communications Security , October 2003.
+
+ [DSS] National Institute of Standards and Technology, U.S.
+ Department of Commerce, "Digital Signature Standard",
+ Draft FIPS 186-3, June 2008.
+
+ [EAI] Abel, Y., "Internationalized Email Headers", RFC 5335,
+ September 2008.
+
+ [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",
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 114]
+\f
+Internet-Draft IKEv2bis October 2008
+
+
+ RFC 4306, December 2005.
+
+ [IP-COMP] 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
+ Internet Protocol", RFC 2401, November 1998.
+
+ [IPV6ADDR]
+ Hinden, R. and S. Deering, "Internet Protocol Version 6
+ (IPv6) Addressing Architecture", RFC 4291, February 2006.
+
+ [ISAKMP] Maughan, D., Schneider, M., and M. Schertler, "Internet
+ Security Association and Key Management Protocol
+ (ISAKMP)", RFC 2408, November 1998.
+
+ [LDAP] Sermersheim, J., "Lightweight Directory Access Protocol
+ (v3)", RFC 4511, June 2006.
+
+ [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., Beadles, M., Eronen, P., and J. Arkko, "The
+ Network Access Identifier", RFC 4282, December 2005.
+
+ [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
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 115]
+\f
+Internet-Draft IKEv2bis October 2008
+
+
+ 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)",
+ 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.
+
+ [ROHCV2] Ertekin, et. al., E., "IKEv2 Extensions to Support Robust
+ Header Compression over IPsec (ROHCoIPsec)",
+ draft-ietf-rohc-ikev2-extensions-hcoipsec (work in
+ progress), October 2008.
+
+ [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 180-3, October 2008.
+
+ [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",
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 116]
+\f
+Internet-Draft IKEv2bis October 2008
+
+
+ 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:
+
+ 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;
+
+
+
+
+
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+\f
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+
+
+ 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
+
+ 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).
+
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 118]
+\f
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+
+
+ 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.
+
+
+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+]
+
+ cookie response <-- N(COOKIE),
+ [V+]
+
+ different D-H <-- N(INVALID_KE_PAYLOAD),
+ group wanted [V+]
+
+
+
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 119]
+\f
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+
+
+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+]
+
+ error in Child SA <-- IDr, [CERT+],
+ creation AUTH,
+ N(error),
+ [V+]
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 120]
+\f
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+
+
+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 May 3, 2009 [Page 121]
+\f
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+
+
+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
+ [V+]
+
+ normal <-- [CP(CFG_REPLY)],
+ response [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)]
+ [V+]
+
+ error case <-- N(error)
+
+ different D-H <-- N(INVALID_KE_PAYLOAD),
+ group wanted [V+]
+
+C.5. CREATE_CHILD_SA Exchange for Rekeying the IKE SA
+
+ request --> SA, Ni, [KEi]
+ [V+]
+
+ response <-- SA, Nr, [KEr]
+ [V+]
+
+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
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 122]
+\f
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+
+
+ 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
+ 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
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 123]
+\f
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+
+
+ 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
+ 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.
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 124]
+\f
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+
+
+ 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
+ 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.
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 125]
+\f
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+
+
+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.
+
+ 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 end 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.
+
+
+
+
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+\f
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+
+
+ 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
+ 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 transform 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
+
+
+
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+\f
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+
+
+ in an interoperable fashion:
+
+ 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.
+
+D.6. Changes from draft -03 to draft-ietf-ipsecme-ikev2bis-00
+
+ Changed the document's filename to draft-ietf-ipsecme-ikev2bis-00.
+ Added Yoav Nir as a co-author.
+
+ In many places in the document, changed "and/or" to "or" when talking
+ about combinations of ESP and AH SAs. For example, in the intro, it
+ said "can be used to efficiently establish SAs for Encapsulating
+ Security Payload (ESP) and/or Authentication Header (AH)". This is
+ changed to "or" to indicate that you can only establish one type of
+ SA at a time.
+
+ In Section 1, clarified that RFC 4306 already replaced IKEv1, and
+ that this document replaces RFC 4306. Also fixed Section 2.5 for
+ similar issue. Also updated the Abstract to cover this.
+
+ In Section 2.15, in the responder's signed octets, changed:
+
+ RestOfRespIDPayload = IDType | RESERVED | InitIDData
+ to
+ RestOfRespIDPayload = IDType | RESERVED | RespIDData
+
+
+
+
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+
+
+ In 2.16, changed "strong" back to "public key signature based" to
+ make it the same as 4306.
+
+ In section 3.10, added "and the field must be empty" to make it clear
+ that a zero-length SPI is really empty.
+
+D.7. Changes from draft-ietf-ipsecme-ikev2bis-00 to
+ draft-ietf-ipsecme-ikev2bis-01
+
+ Throughout, changed "IKE_SA" to "IKE SA", and changed "CHILD_SA" to
+ "Child SA" (except left "CREATE_CHILD_SA" alone).
+
+ Added the middle sentence in the Abstract to say what IKE actually
+ does.
+
+ Added in section 1 "(unless there is failure setting up the AH or ESP
+ Child SA, in which case the IKE SA is still established without IPsec
+ SA)".
+
+ Clarified the titles of 1.1.1, 1.1.2, and 1.1.3.
+
+ In 1.1.2, changed "If there is an inner IP header, the inner
+ addresses will be the same as the outer addresses." because we are
+ talking about transport mode here.
+
+ Added reference to section 2.14 to setion 1.2 and 1.3.
+
+ In 1.2, clarified what is and isn't encrypted in a message.
+
+ Added the following to 1.2: "If the IDr proposed by the initiator is
+ not acceptable to the responder, the responder might use some other
+ IDr to finish the exchange. If the initiator then does not accept
+ that fact that responder used different IDr than the one that was
+ requested, the initiator can close the SA after noticing the fact."
+
+ Moved the paragraph beginning "All messages following..." from 1.3 up
+ to 1.2, and reworded it to apply to all the cases it covers.
+
+ At the end of section 1.3.1, clarified that the responder is the one
+ who controls whether non-first-fragments will be sent, and reworded
+ the paragraph.
+
+ In section 1.3.3, added "The Protocol ID field of the REKEY_SA
+ notification is set to match the protocol of the SA we are rekeying,
+ for example, 3 for ESP and 2 for AH." [Issue #10]
+
+ In 1.3.2, added "of the SA payload" to "New initiator and responder
+ SPIs are supplied in the SPI fields."
+
+
+
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+
+
+ In 1.3.3, fixed the art.
+
+ <-- HDR, SK {SA, Nr, [KEr],
+ Si, TSr}
+ becomes
+ <-- HDR, SK {SA, Nr, [KEr],
+ TSi, TSr}
+
+
+ In 1.4 and 2.18, changed "replaced for the purpose of rekeying" to
+ "rekeyed".
+
+ Split out the SA deletion material from section 1.4 into its own
+ subsection, 1.4.1.
+
+ Clarified which bits are set at the end of Section 1.5.
+
+ In 1.7, added "That is, the version number is *not* changed from RFC
+ 4306.".
+
+ In 2.1, added wording about retransmissions needing to be identical.
+
+ In 2.2, added "or rekeyed" to "In the unlikely event that Message IDs
+ grow too large to fit in 32 bits, the IKE SA MUST be closed"
+
+ In 2.2, moved the sentence "Rekeying an IKE SA resets the sequence
+ numbers." up higher so it would be more likely to be seen. [Issue
+ #15]
+
+ Moved the definition of "original initiator" from 2.8 into 2.2
+ because that is where it is first used.
+
+ In 2.4, added "fresh (i.e., not retransmitted)" to "If a
+ cryptographically protected message has been received from the other
+ side recently". Also added the sentence saying that liveness checks
+ are sometimes call dead peer detection.
+
+ Removed the question to implementers about payload order in 2.5.
+
+ Changed the title of 2.6 to "IKE SA SPIs and Cookies". Also, in the
+ paragraph that describes how to implement the responder, changed the
+ lower-case "should" to "can" to emphasize that this is a choice.
+
+ Added the second paragraph in 2.6 to make it clear that the SPI is
+ used for mapping.
+
+ In section 2.6, upgraded "needs to choose them so as to be unique
+ identifiers of an IKE_SA" to a MUST.
+
+
+
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+
+
+ Added sentences at the end of 2.6 eplaining wny the initiator should
+ limit the number of responses it sends out.
+
+ In 2.6.1, added the example of the shorter exchange; this is copied
+ from RFC 4718 but was dropped in early drafts of this document.
+
+ Added the paragraph to 2.7 that describes needing two proposals if
+ you are having both normal ciphers and combined-mode ciphers. [Issue
+ #20].
+
+ In section 2.8, added "Note that, when rekeying, the new Child SA MAY
+ have different traffic selectors and algorithms than the old one."
+
+ Added a note in 2.9 that PFKEY applies only to IKEv1. Also added
+ that unknown traffic selector types are not returned in narrowed
+ responses.
+
+ Added note in the first paragraph of Setion 2.9.1 about decorrelated
+ policies preventing the problem mentioned.
+
+ In 2.12, removed "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."
+
+ In 2.15, noted that the retry could happen multiple times for
+ different reasons.
+
+ In section 2.16, changed "This shared key generated during an IKE
+ exchange" to "This key".
+
+ At the end of 2.19, added statement that FAILED_CP_REQUIRED is not
+ fatal to the IKE SA.
+
+ Added the reference to ROHCV2 to the end of 2.22.
+
+ In 2.23, changed "can negotiate" to "will use". for UDP
+ encapsulation. Added "or 4500" to "...MUST be sent from and to UDP
+ port 500". Also removed the text about why not to do NAT-traversal
+ over port 500 because we later say you can't do that anyway. [Issue
+ #27] Also removed the last paragraph, which obliquely pointed to
+ MOBIKE. More will be added later on MOBIKE.
+
+ In 3.1, removed "and orderings of messages" from "Exchange type".
+ [Issue #29]
+
+ In 3.1, added "This bit changes to reflect who initiated the last
+ rekey of the IKE SA." to the description of the Initiator bit.
+
+
+
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+
+
+ In 3.3, added a long example of why you might use a Proposal
+ structure because of combined-mode algorithms. [Issue #42]
+
+ In 3.3.2, changed "is unnecessary because the last Proposal could be
+ identified from the length of the SA" to "is unnecessary because the
+ last transform could be identified from the length of the proposal."
+
+ Added reference to AEAD to 3.3.2 and 3.3.3.
+
+ Added the reference to RFC 2104 back for PRF_HMAC_TIGER in 3.3.2.
+ [Issue #33]
+
+ Added note at the bottom of 3.3.2 to see the IANA registry.
+
+ In 3.3.4, removed all the "this could happen in the future" stuff
+ because it already happened.
+
+ Added a reference to email address internationalization to 3.5,
+ making the address binary (not ASCII).
+
+ In the table in 3.6, made "Authority Revocation List (ARL) 8" and
+ "X.509 Certificate - Attribute 10" unspecified.
+
+ In 3.7, changed the last sentence of the first paragraph to eliminate
+ the non-protocol SHOULD.
+
+ In 3.13.1, added "(including protocol 0)" for the start port and end
+ port.
+
+ In 3.14, updated the discussion of initialization modes to reflect
+ that it is only about CBC, and that other specs have to specify their
+ own IVs.
+
+ In 3.15.1, added a pointer to 3.15.3. In the entries for
+ INTERNAL_IP4_SUBNET and INTERNAL_IP6_SUBNET, added a pointer to
+ 3.15.2.
+
+ In 3.15.4, added "The IKE SA is still created even if the initial
+ Child SA cannot be created because of this failure."
+
+ Changed "EAP exchange" to "EAP authentication" in 5.
+
+ Removed "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." from section 5 because it is not possible in
+ most implementations to do so.
+
+ Updated a bunch of reference to their newer versions.
+
+
+
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+
+
+ Added "[V+]" to the end of the exchanges in C.4 and C.5.
+
+ Added two more response templates to Appendix C.1. Added another
+ response template in Appendix C.2. Added two more responses in
+ Appendix C.4.
+
+
+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
+
+
+ Yoav Nir
+ Check Point Software Technologies Ltd.
+ 5 Hasolelim St.
+ Tel Aviv 67897
+ Israel
+
+ Email: ynir@checkpoint.com
+
+
+ Pasi Eronen
+ Nokia Research Center
+ P.O. Box 407
+ FIN-00045 Nokia Group
+ Finland
+
+ Email: pasi.eronen@nokia.com
+
+
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 133]
+\f
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+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
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+ this standard. Please address the information to the IETF at
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+
+
+Acknowledgment
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+Kaufman, et al. Expires May 3, 2009 [Page 134]
+\f
projects / thirdparty / strongswan.git / commitdiff
