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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 4282 (Obsoleted by RFC 7542) ** Obsolete normative reference: RFC 5996 (Obsoleted by RFC 7296) -- Obsolete informational reference (is this intentional?): RFC 3588 (Obsoleted by RFC 6733) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Y. Nir 3 Internet-Draft Check Point 4 Updates: 5996 (if approved) Q. Wu 5 Intended status: Experimental Huawei 6 Expires: June 7, 2013 December 4, 2012 8 An IKEv2 Extension for Supporting ERP 9 draft-nir-ipsecme-erx-08 11 Abstract 13 This document updates the IKEv2 protocol, described in RFC 5996. 14 This extension allows an IKE Security Association (SA) to be created 15 and authenticated using the EAP Re-authentication Protocol extension 16 as described in RFC 6696. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on June 7, 2013. 35 Copyright Notice 37 Copyright (c) 2012 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 1. Introduction 52 IKEv2, as specified in section 2.16 of [RFC5996], allows 53 authentication of the initiator using an EAP method. Using EAP 54 significantly increases the count of round-trips required to 55 establish the IPsec SA, and also may require user interaction. This 56 makes it inconvenient to allow a single remote access client to 57 create multiple IPsec tunnels with multiple IPsec gateways that 58 belong to the same domain. 60 The EAP Re-authentication Protocol (ERP), as described in [RFC6696], 61 allows an EAP peer to authenticate to multiple authenticators, while 62 performing the full EAP method only once. Subsequent authentications 63 require fewer round-trips and no user interaction. 65 Bringing these two technologies together allows a remote access IPsec 66 client to create multiple tunnels with different gateways that belong 67 to a single domain, as well as using the keys from other contexts of 68 using EAP, such as network access within the same domain, to 69 transparently connect to VPN gateways within this domain. 71 Additionally, it allows for faster setting up of new tunnels when 72 previous tunnels have been torn down due to things like network 73 outage, device suspension, or temporarily moving out of range. This 74 is similar to the session resumption mechanism described in 75 [RFC5723], except that instead of a ticket stored on the gateway, the 76 rMSK is used as the session key stored on the AAA server. 78 1.1. Conventions Used in This Document 80 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 81 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 82 document are to be interpreted as described in [RFC2119]. 84 2. Usage Scenarios 86 This work is motivated by the following scenarios: 87 o Multiple tunnels for a single remote access VPN client. Suppose a 88 company has offices in New York City, Paris, and Shanghai. For 89 historical reasons, the email server is located in the Paris 90 office, while most of the servers hosting the company's intranet 91 are located in Shanghai, and the finance department servers are in 92 NYC. An employee using remote access VPN may need to connect to 93 servers from all three locations. While it is possible to connect 94 to a single gateway, and have that gateway route the requests to 95 the other gateways (perhaps through site to site VPN), this is not 96 efficient, and it is more desirable to have the client initiate 97 three different tunnels. It is, however, not desirable to have 98 the user type in a password three times. 99 o Roaming. In these days of mobile phones and tablets, users often 100 move from the wireless LAN in their office, where access may be 101 granted through 802.1x, to a cellular network where VPN is 102 necessary and back again. Both the VPN server and the 802.1x 103 access point are authenticators that connect to the same 104 Authentication, Authorization and Accounting (AAA) servers. So it 105 makes sense to make the transition smooth, without requiring user 106 interaction. The device still needs to detect whether it is 107 within the protected network, in which case it should not use VPN, 108 but this process is beyond the scope of this document. 109 [SecureBeacon] is a now-abandoned attempt at this. 110 o Resumption. If a device gets disconnected from an IKE peer, ERP 111 can be used to reconnect to the same gateway without user 112 intervention. 114 3. Protocol Outline 116 Supporting ERX requires an EAP payload in the first IKE_AUTH request. 117 This is a deviation from the rules in RFC 5996, so support needs to 118 be indicated through a Notify payload in the IKE_SA_INIT response. 119 This Notify serves the same purpose as the EAP-Initiate/Re-auth-Start 120 message of ERX, as specified in section 5.3.1 of RFC 6696. The 121 domain name included in the Domain-Name TLV as specified in section 122 5.3.1.1 of the same document. 124 A supporting initiator that has unexpired keys for this domain will 125 send the EAP_Initiate/Re-auth message in an EAP payload in the first 126 IKE_AUTH request. 128 The responder sends the EAP payload content to a backend AAA server. 129 If that server has a valid rMSK for that session, it sends those 130 along with an EAP-Finish/Re-auth message. The responder then 131 forwards the EAP-Finish/Re-auth message to the Initiator in an EAP 132 payload within the first IKE_AUTH response. 134 The initiator then sends an additional IKE_AUTH request, that 135 includes the AUTH payload which has been calculated using the rMSK in 136 the role of the MSK as described in sections 2.15 and 2.16 of RFC 137 5996. The responder replies similarly, and the IKE_AUTH exchange is 138 finished. 140 If the backend AAA server does not have valid keys for the Re-auth- 141 Start message, it sends back a normal EAP request, and no rMSK key. 142 EAP flow continues as in RFC 5996. 144 The following figure is adapted from appendixes C.1 and C.3 of RFC 145 5996, with most of the optional payloads removed. Note that the 146 EAP_Initiate/Re-auth message is added. 148 IKE_SA_INIT Exchange: 149 | init request --> SA, KE, Ni, 150 | 151 | init response <-- SA, KE, Nr, 152 | N[ERX_SUPPORTED] 154 IKE_AUTH Exchanges: 155 | first request --> EAP(EAP_Initiate/Re-auth), 156 | IDi, 157 | SA, TSi, TSr 158 | 159 | first response <-- IDr, [CERT+], AUTH, 160 | EAP(EAP-Finish/Re-auth) 161 | 162 | last request --> AUTH 163 | 164 | last response <-- AUTH, 165 | SA, TSi, TSr 167 The IDi payload MUST have ID Type ID_RFC822_ADDR and the data field 168 MUST contain the same value as the KeyName-NAI TLV in the 169 EAP_Initiate/Re-auth message. See Section 3.2 for details. 171 3.1. Clarification About EAP Codes 173 Section 3.16 of RFC 5996 enumerates the EAP codes in EAP messages 174 which are carried in EAP payloads. The enumeration goes only to 4. 175 It is not clear whether that list is supposed to be exhaustive or 176 not. 178 To clarify, an implementation conforming to this specification MUST 179 accept and transmit EAP messages with at least the codes for Initiate 180 and Finish (5 and 6) from RFC 6696, in addition to the four codes 181 enumerated in RFC 5996. This document is intentionally silent about 182 other EAP codes that are neither enumerated in RFC 5996 nor in that 183 document. 185 3.2. User Name in the Protocol 187 The authors, as well as participants of the HOKEY and IPsecME working 188 groups believe that all use cases for this extension to IKE have a 189 single backend AAA server doing both the authentication and the re- 190 authentication. The reasoning behind this is that IKE runs over the 191 Internet, and would naturally connect to the user's home network. 193 This section addresses instances where this is not the case. 195 Section 5.3.2 of RFC 6696 describes the EAP-Initiate/Re-auth packet, 196 which in the case of IKEv2 is carried in the first IKE_AUTH request. 197 This packet contains the KeyName-NAI TLV. This TLV contains the 198 username used in authentication. It is relayed to the AAA server in 199 the AccessRequest message, and is returned from the AAA server in the 200 AccessAccept message. 202 The username part of the NAI within the TLV is the EMSKName 203 ([RFC5295] encoded in hexadecimal digits. The domain part is the 204 domain name of the home domain of the user. The username part is 205 ephemeral in the sense that a new one is generated for each full 206 authentication. This ephemeral value is not a good basis for making 207 policy decisions, and they are also a poor source of user 208 identification for the purposes of logging. 210 Instead, it is up to the implementation in the IPsec gateway to make 211 policy decisions based on other factors. The following list is by no 212 means exhaustive: 213 o In some cases the home domain name may be enough to make policy 214 decisions. If all users with a particular home domain get the 215 same authorization, then policy does not depend on the real user 216 name. Meaningful logs can still be issued by correlating VPN 217 gateway IKE events with AAA servers access records. 218 o Sometimes users receive different authorizations based on groups 219 they belong to. The AAA server can communicate such information 220 to the VPN gateway, for example using the CLASS attribute 221 ([RFC2865]) in RADIUS and Diameter ([RFC3588]). Logging again 222 depends on correlation with AAA servers. 223 o AAA servers may support extensions that allow them to communicate 224 with their clients (in our case - the VPN gateway) to push user 225 information. For example, a certain product integrates a RADIUS 226 server with the Lightweight Directory Access Protocol (LDAP - 227 [RFC4511]), so a client could query the server using LDAP and 228 receive the real record for this user. Others may provide this 229 data through vendor-specific extensions to RADIUS or DIAMETER. 231 In any case authorization is a major issue in deployments, if the 232 backend AAA server supporting the re-authentication is different from 233 the AAA server that had supported the original authentication. It is 234 up to the re-authenticating AAA server to provide the necessary 235 information for authorization. A conforming implementation of this 236 protocol MAY reject initiators for which it is unable to make policy 237 decisions because of these reasons. 239 4. ERX_SUPPORTED Notification 241 The Notify payload is as described in RFC 5996: 243 1 2 3 244 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 1 245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 246 ! Next Payload !C! RESERVED ! Payload Length ! 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 ! Protocol ID ! SPI Size ! ERX Notify Message Type ! 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 ! Domain Name ! 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 o Protocol ID (1 octet) MUST be zero, as this message is related to 254 an IKE SA. 255 o SPI Size (1 octet) MUST be zero, in conformance with section 3.10 256 of RFC 5996. 257 o ERX Notify Message Type (2 octets) - MUST be xxxxx, the value 258 assigned for ERX. TBA by IANA. 259 o Domain Name (variable) - contains the domain name or realm, as 260 these terms are used in RFC 6696, and encoded as ASCII, as 261 specified in [RFC4282]. 263 5. Security Considerations 265 The protocol extension described in this document extends the 266 authentication from one EAP context, which may or may not be part of 267 IKEv2, to an IKEv2 context. Successful completion of the protocol 268 proves to the authenticator, which in our case is a VPN gateway, that 269 the supplicant, or VPN client, has authenticated in some other EAP 270 context. 272 The protocol supplies the authenticator with the domain name with 273 which the supplicant has authenticated, but does not supply it with a 274 specific identity. Instead, the gateway receives an EMSKName, which 275 is an ephemeral ID. With this variant of the IKEv2 protocol, the 276 initiator never sends its real identity on the wire, while the server 277 does. This is different from the usual IKEv2 practice of the 278 initiator revealing its identity first. 280 If the domain name is sufficient to make access control decisions, 281 this is enough. If not, then the gateway needs to find out either 282 the real name or authorization information for that particular user. 283 This may be done using the AAA protocol or by some other federation 284 protocol, which is out of scope for this specification. 286 6. IANA Considerations 288 IANA is requested to assign a notify message type from the status 289 types range (16418-40959) of the "IKEv2 Notify Message Types" 290 registry with name "ERX_SUPPORTED". 292 7. Acknowledgements 294 The authors would like to thank Yaron Sheffer for comments and 295 suggested text that have contributed to this document. 297 8. References 299 8.1. Normative References 301 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 302 Requirement Levels", BCP 14, RFC 2119, March 1997. 304 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The 305 Network Access Identifier", RFC 4282, December 2005. 307 [RFC5295] Salowey, J., Dondeti, L., Narayanan, V., and M. Nakhjiri, 308 "Specification for the Derivation of Root Keys from an 309 Extended Master Session Key (EMSK)", RFC 5295, 310 August 2008. 312 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 313 "Internet Key Exchange Protocol: IKEv2", RFC 5996, 314 September 2010. 316 [RFC6696] Cao, Z., He, B., Shi, Y., Wu, Q., and G. Zorn, "EAP 317 Extensions for the EAP Re-authentication Protocol (ERP)", 318 RFC 6696, July 2012. 320 8.2. Informative References 322 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 323 "Remote Authentication Dial In User Service (RADIUS)", 324 RFC 2865, June 2000. 326 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 327 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 329 [RFC4511] Sermersheim, J., "Lightweight Directory Access Protocol 330 (LDAP): The Protocol", RFC 4511, June 2006. 332 [RFC5723] Sheffer, Y. and H. Tschofenig, "Internet Key Exchange 333 Protocol Version 2 (IKEv2) Session Resumption", RFC 5273, 334 January 2010. 336 [SecureBeacon] 337 Sheffer, Y. and Y. Nir, "Secure Beacon: Securely Detecting 338 a Trusted Network", draft-sheffer-ipsecme-secure-beacon 339 (work in progress), June 2009. 341 Authors' Addresses 343 Yoav Nir 344 Check Point Software Technologies Ltd. 345 5 Hasolelim st. 346 Tel Aviv 67897 347 Israel 349 Email: ynir@checkpoint.com 351 Qin Wu 352 Huawei Technologies Co., Ltd. 353 101 Software Avenue, Yuhua District 354 Nanjing, JiangSu 210012 355 China 357 Email: sunseawq@huawei.com