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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-04) exists of draft-kivinen-ipsecme-ikev2-rfc5996bis-00 -- Possible downref: Normative reference to a draft: ref. 'RFC5996bis' Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPsecME Working Group Y. Nir 3 Internet-Draft Check Point 4 Intended status: Standards Track August 22, 2013 5 Expires: February 23, 2014 7 Handing Over Child SAs Following Re-Authentication in IKEv2 8 draft-nir-ipsecme-cafr-01 10 Abstract 12 This document describes an extension to the IKEv2 protocol whereby 13 Child SAs are moved to the new IKE SA following re-authentication. 14 This allows for a smoother transition with no loss of connectivity. 16 Status of this Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on February 23, 2014. 33 Copyright Notice 35 Copyright (c) 2013 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 1.1. Conventions Used in This Document . . . . . . . . . . . . . 3 52 2. Handing Over Child SAs . . . . . . . . . . . . . . . . . . . . 4 53 2.1. The HAND_OVER_CHILD_SAS Notification . . . . . . . . . . . 4 54 2.2. Verifying the HAND_OVER_CHILD_SAS Notification . . . . . . 5 55 3. The Illustrated Protocol . . . . . . . . . . . . . . . . . . . 5 56 4. Interaction with Other Standards . . . . . . . . . . . . . . . 5 57 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 58 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 59 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 60 8. Changes from Previous Versions . . . . . . . . . . . . . . . . 6 61 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 62 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 63 9.2. Informative References . . . . . . . . . . . . . . . . . . 7 64 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 66 1. Introduction 68 The Internet Key Exchange version 2 (IKEv2) protocol, as specified in 69 [RFC5996bis] associates Child SAs with the IKE SAs under which the 70 exchange that created them took place. With the deletion of the IKE 71 SA due to expiry, policy change, or an explicit message from the 72 peer, the child SAs associated with it are implicitly closed as 73 described in section 1.4.1 of the IKEv2 document. This behavior is 74 not desired when IKE SAs are replaced rather than deleted, because 75 those child SAs could still be valid and there is no security reason 76 to create new ones prematurely. 78 There are two cases where an IKE SA is replaced. 79 1. Rekeying, where new keys are generated. This is described in 80 section 2.18 of RFC 5996. This is done mainly for key freshness. 81 2. Re-Authentication, where both sides authenticate, and new keys 82 are generated. This is done as part of a risk management policy, 83 to limit the time that compromised IKE SA keys can be used to 84 provide the attacker access to the network. No reauthentication 85 exchange is specified in the RFC. Instead, it's simply the 86 Initial and Authentication exchanges done as if from scratch. 87 This is described in section 2.8.3 of RFC 5996. 89 For rekeying, RFC 5996 provides a way to avoid having to re-create 90 all child SAs. When an IKE SA is rekeyed, all the Child SAs under 91 the old IKE SA are inherited by the new IKE SA, so that the 92 subsequent deletion of the old IKE SA does not affect the Child SAs. 93 This behavior is described in section 2.8 paragraph 4 of RFC 5996. 95 For reauthentication, RFC 5996 does not provide a similar mechanism, 96 and section 2.8.3 explicitly says that Child SAs need to be created 97 from scratch. This is often inconvenient, as IPsec systems usually 98 create Child SAs only in response to traffic and multiple Child SAs 99 may exist for a single IKE SA. The protocol extension in this draft 100 closes this gap. 102 1.1. Conventions Used in This Document 104 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 105 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 106 document are to be interpreted as described in [RFC2119]. 108 The terms IKE SA, Child SA, Rekeying, and Reauthentication are as 109 described in the RFC 5996. 111 2. Handing Over Child SAs 113 This document defines a new notification that can be sent over an old 114 IKE SA, just after an IKE_AUTH exchange has been used to re- 115 authenticate. The notification tells the peer to transfer all Child 116 SAs that belong to the current (old) IKE SA to be owned by the new 117 IKE SA, so that when the old IKE SA is deleted, those Child SAs are 118 not. If both peers send this notification, all Child SAs belonging 119 to the old IKE SA are immediately inherited by the new IKE SA. 121 In addition to the Child SAs, any IP address assigned to either peer 122 through the use of the CFG payload (as described in section 2.19 of 123 RFC 5996), is also associated with the new IKE SA. 125 The new notification MAY be accompanied by a DELETE payload, so as to 126 transfer the Child SAs and delete the old IKE SA at the same time. 128 2.1. The HAND_OVER_CHILD_SAS Notification 130 The HAND_OVER_CHILD_SA notification is formatted as follows: 132 1 2 3 133 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 1 134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 ! Next Payload !C! RESERVED ! Payload Length ! 136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 137 ! Protocol ID ! SPI Size ! HAND_OVER_CHILD_SAS Type ! 138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 | | 140 ~ Security Parameter Index (SPI) ~ 141 | | 142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 144 Figure 1 146 o Protocol ID (1 octet) MUST be 1, denoting an IKE SA. Note that 147 previous versions of RFC 5996 explicitly mentioned the 148 possibility, but the current version omits this as prior to this 149 specification there were no cases where the value 1 should have 150 been used. 151 o SPI Size (1 octet) MUST be 16, as that is the size of the 152 concatenation of the IKE SPIs. 153 o Security Parameter Index (16 octets) - contains the concatenated 154 SPIs of the old IKE SA. The Initiator SPI comes first, similar to 155 the first 16 bytes of the IKE header. 156 o HAND_OVER_CHILD_SAS Notify Message Type (2 octets) - MUST be 157 xxxxx, the value assigned for HAND_OVER_CHILD_SAS. TBA by IANA. 159 2.2. Verifying the HAND_OVER_CHILD_SAS Notification 161 To go through with the new IKE SA inheriting the SAs of the old IKE 162 SA, all of the following MUST apply: 163 o Both sides have to be successfully authenticated, and the new IKE 164 SA has to be established. 165 o The authenticated identities of both sides under the new IKE SA 166 are the same as those under the old IKE SA. If the authenticated 167 identity of one peer differs from the authenticated identity that 168 it had in the previous IKE SA, the other side MUST respond with an 169 INVALID_SYNTAX notification. 171 If either of the above conditions does not apply, a conformant 172 implementation MUST NOT send the HAND_OVER_CHILD_SAS Notification. 173 Additionally, an implementation MUST NOT hand over the child SAs if 174 the other side has not sent the notification, and MUST hand them over 175 if both it and the other side had sent the notification. 177 3. The Illustrated Protocol 179 The Informational exchange after creating a new IKE SA: 181 Initiator Responder 182 ----------------------------------------------------------------- 183 HDR, SK { 184 N(HAND_OVER_IKE_SAS, new IKE SA SPIs), 185 DELETE 186 } --> 187 HDR, SK { 188 N(HAND_OVER_IKE_SAS, new IKE SA SPIs) 189 <-- } 191 Figure 2 193 Note that in the above figure, the HDR has the IKE SPIs of the old 194 IKE SAs, and the SK payload uses the keys of the old IKE SA, because 195 this message is sent over the old IKE SA. 197 4. Interaction with Other Standards 199 This document changes things so that there is often no need to create 200 new Child SAs along with the new IKE SA when reauthenticating. This 201 makes the full IKE_AUTH exchange with the piggy-backed Child SA 202 exchange (as described in RFC 5996) superfluous. Implementations 203 should consider implementing the childless extension of IKEv2 204 ([RFC6023]) in addition to this specification. 206 5. Acknowledgements 208 The author would like to thank Valery Smyslov for the suggestion of 209 moving the hand-over from the IKE_AUTH to an Informational under the 210 old IKE SA. This changed (in version -01) simplified the protocol 211 significantly. 213 6. IANA Considerations 215 IANA is requested to assign a notify message type from the status 216 types range (16418-40959) of the "IKEv2 Notify Message Types" 217 registry with name "HAND_OVER_CHILD_SAS" 219 7. Security Considerations 221 The HAND_OVER_CHILD_SAS notification is sent protected by the old IKE 222 SA. This protects against stealing child SAs. The requirement for 223 sameness of authenticated identity protects against errors by one 224 peer transferring child SAs to some other peer, although we cannot 225 think of any attack that would exploit this. 227 8. Changes from Previous Versions 229 [NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION] 231 Version -01 moved the sending of the notification from the IKE_AUTH 232 exchange that is part of reauthentication to the Informational 233 exchange that is part of closing the old IKE SA. This made 234 cryptographic binding to the old IKE SA unnecessary. 236 9. References 238 9.1. Normative References 240 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 241 Requirement Levels", BCP 14, RFC 2119, March 1997. 243 [RFC5996bis] 244 Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 245 Kivinen, "Internet Key Exchange Protocol Version 2 246 (IKEv2)", draft-kivinen-ipsecme-ikev2-rfc5996bis-00 (work 247 in progress), August 2013. 249 9.2. Informative References 251 [RFC6023] Nir, Y., Tschofenig, H., Deng, H., and R. Singh, "A 252 Childless Initiation of the Internet Key Exchange Version 253 2 (IKEv2) Security Association (SA)", RFC 6023, 254 October 2010. 256 Author's Address 258 Yoav Nir 259 Check Point Software Technologies Ltd. 260 5 Hasolelim st. 261 Tel Aviv 6789735 262 Israel 264 Email: ynir@checkpoint.com