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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) -- Possible downref: Normative reference to a draft: ref. 'IKEv2' Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group V. Smyslov 3 Internet-Draft ELVIS-PLUS 4 Intended status: Standards Track September 2, 2014 5 Expires: March 6, 2015 7 The NULL Authentication Method in IKEv2 Protocol 8 draft-smyslov-ipsecme-ikev2-null-auth-03 10 Abstract 12 This document introduces the NULL Authentication Method for the IKEv2 13 Protocol. This method provides a way to omit peer authentication in 14 the IKEv2. It may be used to preserve anonymity of or in the 15 situations, where no trust relationship exists between the parties. 17 Status of this Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on March 6, 2015. 34 Copyright Notice 36 Copyright (c) 2014 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 1.1. Conventions Used in This Document . . . . . . . . . . . . . 3 53 2. Using the NULL Authentication Method . . . . . . . . . . . . . 4 54 2.1. Authentication Payload . . . . . . . . . . . . . . . . . . 4 55 2.2. Identity Payload . . . . . . . . . . . . . . . . . . . . . 4 56 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 57 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 58 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 59 6. Normative References . . . . . . . . . . . . . . . . . . . . . 8 60 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 62 1. Introduction 64 The Internet Key Exchange Protocol version 2 (IKEv2), specified in 65 [IKEv2], provides a way for two parties to perform authenticated key 66 exchange. Mutual authentication is mandatory in the IKEv2, so that 67 each party must be authenticated by the other. However the 68 authentication methods, used by the peers, need not be the same. 70 In some situations mutual authentication is undesirable, superfluous 71 or impossible. For example: 73 o User wants to get anonymous access to some server. In this 74 situation he/she should be able to authenticate the server, but to 75 leave out his/her own authentication to preserve anonymity. In 76 this case one-way authentication of the responder is desirable. 78 o Sensor, that sleeps most of the time, but periodically wakes up, 79 makes some measurment (e.g. temperature) and sends the results to 80 some server. The senser must be authenticated by the server to 81 ensure authenticity of the measurment, but the server need not be 82 authenticated by the senser. In this case one-way authentication 83 of the initiator is sufficient. 85 o Two peers without any trust relationship want to get some level of 86 security in their communications. Without trust relationship they 87 cannot prevent active Man-in-the-Middle attacks, but it is still 88 possible to prevent passive eavesdropping with opportunistic 89 encryption. In this case they can use unauthenticated key 90 exchange. 92 To meet these needs the document introduces the NULL Authentication 93 Method, which is a "dummy" method, that provides no authentication. 94 This allows peer to explicitly indicate to the other side that it is 95 unwilling or unable to certify its identity. 97 1.1. Conventions Used in This Document 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 101 document are to be interpreted as described in [RFC2119]. 103 2. Using the NULL Authentication Method 105 In IKEv2 each peer independently selects the method to authenticate 106 itself to the other side. It means that any of the peers may choose 107 to omit its authentication by using the NULL Authentication Method. 108 If it is not acceptable for the other peer, it MUST return 109 AUTHENTICATION_FAILED Notification. Note, that when the Initiator 110 uses EAP, the Responder MUST NOT use the NULL Authentication Method 111 (in conformance with the section 2.16 of [IKEv2]). 113 The NULL Authentication Method affects how the Authentication and the 114 Identity payloads are formed in the IKE_AUTH Exchange. 116 2.1. Authentication Payload 118 Despite the fact that the NULL Authentication Method provides no 119 authentication, the AUTH Payload must still be present in the 120 IKE_AUTH Exchange messages and must be properly formed, as it 121 cryptographically links the IKE_SA_INIT Exchange messages with the 122 other messages sent over the IKE SA. 124 With the NULL Authentication Method the content of the AUTH Payload 125 MUST be computed using the syntax for pre-shared secret 126 authentication, described in Section 2.15 of [IKEv2]. The values 127 SK_pi and SK_pr MUST be used as shared secrets for the content of the 128 AUTH Payloads generated by Initiator and Responder respectively. 129 Note, that this is exactly how the content of the two last AUTH 130 Payloads is calculated for non-key generating EAP Method (see Section 131 2.16 of [IKEv2] for details). The value for the the NULL 132 Authentication Method is . 134 2.2. Identity Payload 136 The NULL Authentication Method provides no authentication of the 137 party using it. For that reason the Identity Payload content cannot 138 be verified by the peer and MUST be ignored by the IKE. 140 This specification defines new ID Type - ID_NULL, which is intended 141 to be used with the NULL Authentication Method to explicitely 142 indicate anonymity of the peer. This ID Type SHOULD NOT be used with 143 other authentication methods. The Identification Data in Identity 144 Payload for the ID_NULL type MUST be absent and the ID Type is set to 145 . 147 3. Security Considerations 149 IKEv2 protocol provides mutual authentication of the peers. If one 150 peer uses the NULL Authentication Method, then this peer cannot be 151 authenticated by the other side, and it makes authentication in IKEv2 152 to be one-way. If both peers use the NULL Authentication method, key 153 exchange becomes unauthenticated, that makes it subject to the Man- 154 in-the-Middle attack. 156 The identity of the peer using the NULL Authenticated Method cannot 157 be verified by the other side and, therefore, MUST NOT be used 158 neither for authorization purposes, nor for policy decisions. All 159 peers who use the NULL Authenticated Method should be considered by 160 the other party as "guests" and get the least possible privileges. 162 If endpoint receives a request to create an unauthenticated IKE SA 163 from the IP address, which is configured on the endpoint to be 164 authenticated, the request SHOULD be rejected. 166 If the peer uses the NULL Authenticated Method, then the content of 167 its Traffic Selector Payloads must be treated with care. In 168 particular, implementations are advised not to trust blindly that the 169 public IP addresses the peer put into TS Payload are really belong to 170 it. It is RECOMMENDED for security gateways to always assign 171 internal IP addresses to unauthenticated clients as described in 172 Section 2.19 of [IKEv2]. 174 4. Acknowledgments 176 The author would like to thank Paul Wouters, Yaron Sheffer and Tero 177 Kivinen for their reviews and valuable comments. 179 5. IANA Considerations 181 This document defines new value in the "IKEv2 Authentication Method" 182 registry: 184 NULL Authentication Method 186 It also defines new value in the "IKEv2 Identification Payload ID 187 Types" registry: 189 ID_NULL 191 6. Normative References 193 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 194 Requirement Levels", BCP 14, RFC 2119, March 1997. 196 [IKEv2] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 197 Kivinen, "Internet Key Exchange Protocol Version 2 198 (IKEv2)", draft-kivinen-ipsecme-ikev2-rfc5996bis-04 (work 199 in progress), June 2014. 201 Author's Address 203 Valery Smyslov 204 ELVIS-PLUS 205 PO Box 81 206 Moscow (Zelenograd) 124460 207 Russian Federation 209 Phone: +7 495 276 0211 210 Email: svan@elvis.ru