NETWORK WORKING GROUP N. Williams Internet-Draft Sun Intended status: Standards Track March 21, 2008 Expires: September 22, 2008 Channel Bindings for IPsec Using IKEv2 and Public Keys draft-williams-ipsec-channel-binding-00.txt 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 September 22, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Williams Expires September 22, 2008 [Page 1] Internet-Draft IPsec Pubkey Channel Bindings March 2008 Abstract This document specifies the channel bindings for "IPsec channels" where the peers used the Internet Key Exchange protocol version 2 (IKEv2) and where they used public keys and/or certificates to authenticate each other Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . . 3 2. IPsec Channel Bindings . . . . . . . . . . . . . . . . . . . 4 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . 6 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. Normative References . . . . . . . . . . . . . . . . . . . . 7 5.2. Informative References . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . 10 Williams Expires September 22, 2008 [Page 2] Internet-Draft IPsec Pubkey Channel Bindings March 2008 1. Introduction Given the ability to construct IPsec channels [I-D.ietf-btns-connection-latching] and the ability to bind authentication at application layers to such secure channels [RFC5056] the only missing components are: a definition of IPsec channel bindings, and Application Programming Interfaces (APIs) by which applications can obtain them. Here we specify the "end-point channel bindings" [RFC5056] for IPsec channels when peers use IKev2 [RFC4306] and public keys and/or certificates. IPsec APIs [I-D.ietf-btns-ipsec-apireq] are out of scope for this document. IPsec channels where the peers were authenticated by methods other than public key cryptography, such as EAP [RFC3748] or pre-shared keys (PSK), or where IKEv2 was not used (e.g., manual keying), are out of scope for this document. Channel bindings for such IPsec channels should be specified elsewhere, if at all. 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]. Williams Expires September 22, 2008 [Page 3] Internet-Draft IPsec Pubkey Channel Bindings March 2008 2. IPsec Channel Bindings The channel bindings for IPsec channels established via connection latching [I-D.ietf-btns-connection-latching] between peers that use IKEv2 [RFC4306] and public keys (with or without PKIX certificates [RFC3280]) SHALL be: the octet-string that results from the concatenation of the two peers' raw public keys as they appear in the subjectPublicKey field of their corresponding certificates' subjectPublicKeyInfo, or as they appear in their IKEv2 CERT payload when the "Raw RSA Key" CERT payload type has been used (see section 3.6 of [RFC4306]. The order of concatenation SHALL be the binary collation order of the two public keys, in increasing order. The "binary collation order" is the "i;octet" collation registered in the "Collation Registry for Internet Application Protocols" [RFC4790]. Because public keys in certificates are bit strings but the i;octet collation operates on octet strings, public keys appearing in certificates MUST be padded with zero bits to a number of bits that is divisible by eight. We provide end-point channel bindings (the peers' public keys) as the IPsec channel binding because the construction of IPsec channels by connection latching [I-D.ietf-btns-connection-latching] does not unambiguously identify a single IKE_SA or CHILD SA pair from which "unique channel bindings" could be derived. We use a binary collation to determine the order of concatenation because connection latching does not unambiguously identify the initiator of the channel (besides, even TCP supports a notion of simultaneous connections, in which case both peers are the initiators). By using a collation to pick which key follows the other we obtain an encoding of the end-point channel bindings that both peers can agree on without negotiation. Williams Expires September 22, 2008 [Page 4] Internet-Draft IPsec Pubkey Channel Bindings March 2008 3. IANA Considerations This document creates a type of channel binding, and so requires registration in the IANA channel binding registry (set out by [RFC5056]). The registration procedure will be followed when this document enters the RFC-Editor queue. The registration will be as follows: o Channel binding unique prefix (name): IPsec-end-point-IKEv2-pubkey o Channel binding type: end-point o Channel type: IPsec o Published specification: o Channel binding is secret: no o Description: see Section 2 o Intended usage: COMMON o Contact: this document's author/editor o Owner/Change controller: IETF Williams Expires September 22, 2008 [Page 5] Internet-Draft IPsec Pubkey Channel Bindings March 2008 4. Security Considerations The security considerations of [RFC5056], [I-D.ietf-btns-connection-latching], and IPsec generally [RFC4301] apply. The security of an application using channel binding to IPsec channels depends critically on the overall security of each of these components: IPsec [RFC4301], including the IPsec key exchange protocol [RFC4306], ESP/AH [RFC4303] [RFC4302], IPsec connection latching, and the application's authentication and channel binding mechanism. A compromise of any one of those components may compromise the application to varying degrees. This document describes end-point channel bindings for some IPsec channels. End-point channel bindings do not uniquely identify a connection, but, in this case, a pair of peers. There are no additional security considerations, relating to the type of this channel binding, beyond those described in [RFC5056]. The construction of IPsec end-point channel bindings described herein depends on the strength of the public keys and public key algorithms used by the IPsec peers to authenticate each other, as well as on IKEv2. As such is adds no weakness beyond any weaknesses in the those cryptosystems. And because these are _public_ keys this construction does not require confidentiality protection of the channel bindings. Williams Expires September 22, 2008 [Page 6] Internet-Draft IPsec Pubkey Channel Bindings March 2008 5. References 5.1. Normative References [I-D.ietf-btns-connection-latching] Williams, N., "IPsec Channels: Connection Latching", draft-ietf-btns-connection-latching-04 (work in progress), December 2007. [I-D.ietf-btns-ipsec-apireq] Richardson, M. and B. Sommerfeld, "Requirements for an IPsec API", draft-ietf-btns-ipsec-apireq-00 (work in progress), April 2006. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3280] 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. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, December 2005. [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [RFC4790] Newman, C., Duerst, M., and A. Gulbrandsen, "Internet Application Protocol Collation Registry", RFC 4790, March 2007. [RFC5056] Williams, N., "On the Use of Channel Bindings to Secure Channels", RFC 5056, November 2007. 5.2. Informative References [I-D.ietf-btns-core] Williams, N. and M. Richardson, "Better-Than-Nothing- Security: An Unauthenticated Mode of IPsec", draft-ietf-btns-core-06 (work in progress), January 2008. Williams Expires September 22, 2008 [Page 7] Internet-Draft IPsec Pubkey Channel Bindings March 2008 [I-D.ietf-btns-prob-and-applic] Touch, J., Black, D., and Y. Wang, "Problem and Applicability Statement for Better Than Nothing Security (BTNS)", draft-ietf-btns-prob-and-applic-06 (work in progress), October 2007. [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748, June 2004. Williams Expires September 22, 2008 [Page 8] Internet-Draft IPsec Pubkey Channel Bindings March 2008 Author's Address Nicolas Williams Sun Microsystems 5300 Riata Trace Ct Austin, TX 78727 US Email: Nicolas.Williams@sun.com Williams Expires September 22, 2008 [Page 9] Internet-Draft IPsec Pubkey Channel Bindings March 2008 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. 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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 rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Williams Expires September 22, 2008 [Page 10]