Network Working Group V. Smyslov Internet-Draft ELVIS-PLUS Intended status: Informational December 24, 2013 Expires: June 27, 2014 The NULL Authentication Method in IKEv2 Protocol draft-smyslov-ipsecme-ikev2-null-auth-00 Abstract This document defines the NULL Authentication Method for IKEv2 Protocol. This method provides a way to omit peer authentication in IKEv2 and to explicitely indicate it in the protocol run. This method may be used to preserve anonymity or in situations, where no trust relationship exists between the parties. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Smyslov Expires June 27, 2014 [Page 1] Internet-Draft NULL Auth in IKEv2 December 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . . 3 2. Using NULL Authentication Method . . . . . . . . . . . . . . . 4 2.1. Authentication Payload . . . . . . . . . . . . . . . . . . 4 2.2. Identity Payload . . . . . . . . . . . . . . . . . . . . . 4 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. Normative References . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 Smyslov Expires June 27, 2014 [Page 2] Internet-Draft NULL Auth in IKEv2 December 2013 1. Introduction The Internet Key Exchange Protocol version 2 (IKEv2), specified in [RFC5996], provides a way for two parties to perform authenticated key exchange. Mutual authentication is mandatory in the IKEv2, so that each party must be authenticated by the other, but authentication methods, used by the peers, need not be the same. In some situations mutual authentication is undesirable or impossible. For example: o User wants to get anonymous access to some resource. In this situation he/she should be able to authenticate server, but to leave out his/her own authentication to prevent anonymity. In this case one-way authentication is desirable. o Two peers without any trust relationship want to get some level of security in their communications. Without trust relationship they cannot prevent active Man-in-the-Middle attacks, but it is still possible to prevent passive eavesdropping with opportunistic encryption. In this case they have to perform unauthenticated key exchange. To meet this needs the document introduces NULL Authentication Method, which is effectively a "dummy" method, that provides no authentication. This allows peer to explicitely indicate to the other side that he is unwilling or unable to certify his identity. 1.1. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Smyslov Expires June 27, 2014 [Page 3] Internet-Draft NULL Auth in IKEv2 December 2013 2. Using NULL Authentication Method NULL Authentication Method affects how Authentication and Identity Payloads are formed in IKE_AUTH Exchange. 2.1. Authentication Payload Even when peer uses NULL Authentication, the AUTH Payload must still be present in IKE_AUTH Exchange and must be properly formed, as it cryptographically links IKE_SA_INIT Messages with the other Messages sent over IKE SA. With NULL Authentication Method the content of AUTH Payload MUST be computed using the syntax for pre-shared secret authentication, described in Section 2.15 of [RFC5996]. The values SK_pi and SK_pr MUST be used as shared secrets for AUTH Payloads generated by Initiator and Responder respectively. Note, that this is exactly how content of the two last AUTH Payloads is calculated in case of using non-key generating EAP Method (see Section 2.16 of [RFC5996] for details). The field Auth Method MUST be set to . 2.2. Identity Payload NULL Authentication Method provides no authentication of the party using it. For that reason Identity Payload content cannot be verified by the other party and SHOULD be ignored. It MAY be used for the purpose of audit, but it MUST NOT be used for any authorization decisions. As peer identity is meaningless in this case, Identification Data MAY be omited from ID Payload, in which case ID Type MAY be set to any value. Implementations supporting NULL Authentication Method MUST NOT fail if they receive such "empty" ID Payload. Smyslov Expires June 27, 2014 [Page 4] Internet-Draft NULL Auth in IKEv2 December 2013 3. Security Considerations IKEv2 protocol provides mutual authentication of the peers. If one peer uses NULL Authentication Method, then this peer cannot be authenticated by the other side, and it makes authentication in IKEv2 to become one-way. If both peers use NULL Authentication method, key exchange becomes unauthenticated, that makes it subject to the Man- in-the-Middle attack. The identity of the peer using NULL Authenticated Method cannot be verified by the other side and, therefore, MUST NOT be used neither for authorization purposes, nor for policy decisions. All peers who use NULL Authenticated Method should be considered by the other party as "guests" and get the least possible privileges. Smyslov Expires June 27, 2014 [Page 5] Internet-Draft NULL Auth in IKEv2 December 2013 4. IANA Considerations This document defines new value in the "IKEv2 Authentication Method" registry: NULL Authentication Method Smyslov Expires June 27, 2014 [Page 6] Internet-Draft NULL Auth in IKEv2 December 2013 5. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010. Smyslov Expires June 27, 2014 [Page 7] Internet-Draft NULL Auth in IKEv2 December 2013 Author's Address Valery Smyslov ELVIS-PLUS PO Box 81 Moscow (Zelenograd) 124460 RU Phone: +7 495 276 0211 Email: svan@elvis.ru Smyslov Expires June 27, 2014 [Page 8]