Host Identity Protocol Heer Internet-Draft Distributed Systems Group, RWTH Intended status: Informational Aachen University Expires: August 21, 2008 Varjonen Helsinki Institute for Information Technology February 18, 2008 HIP Certificates draft-varjonen-hip-cert-00 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. This document may not be modified, and derivative works of it may not be created, except to publish it as an RFC and to translate it into languages other than English. 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 August 21, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document specifies a certificate parameter called CERT for the Host Identity Protocol (HIP). The CERT parameter is a container for Heer & Varjonen Expires August 21, 2008 [Page 1] Internet-Draft HIP CERT February 2008 Simple Public Key Infrastructure (SPKI) and X.509 certificates. It is used for carrying these certificates in HIP control messages. Additionally, this document specifies the representations of Host Identity Tags in SPKI certificates. Requirements Language 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 RFC 2119 [RFC2119]. 1. Introduction Digital certificates bind a piece of information to a public key by means of a digital signature, and thus, enable the holder of a private key to generate cryptographically verifiable statements. The Host Identity Protocol (HIP)[I-D.ietf-hip-base] defines a new cryptographic namespace based on asymmetric cryptography. Each host's identity is derived from a public key, allowing hosts to digitally sign data with their private key. This document specifies the CERT parameter that is used to transmit digital signatures in HIP. It corresponds to the placeholder specified in [I-D.ietf-hip-base]. 2. CERT Parameter The CERT parameter is a container for a certain types of digital certificates. It may either carry SPKI certificates or X.509.v3 certificates. It does not specify any certificate semantics. However, it defines organizational parameters that help HIP hosts to transmit semantically grouped parameters. The CERT parameter may be covered by the HIP SIGNATURE field and is a non-critical parameter. Each HIP packet may contain multiple CERT parameters. If these parameters are related in a way that requires several parameters to be handled in sequence, the Cert group and the Cert count field must be set. Ungrouped certificates exhibit a unique Cert group field and set the Cert count to 1. CERT parameters with the same Cert group number in the group field indicate a logical grouping. The Cert count field indicates the number of grouped CERT parameters. CERT parameters that belong to the same CERT group may be contained in multiple sequential packets. This is indicated by a higher Cert count than the amount of CERT parameters with matching Cert group Heer & Varjonen Expires August 21, 2008 [Page 2] Internet-Draft HIP CERT February 2008 fields in a packet. Within a HIP packet, CERT parameters must be placed in ascending order of their Cert group field. Cert groups may only span multiple packets if the cert group does not fit the packet. Only one Cert group may span two subsequent packets. The Cert ID acts as a sequence number to identify the certificates in a Cert group. The numbers in the Cert ID field must start from 1 up to Cert count. The CERT parameter can be used in I1, R1, I2, R2, and UPDATE messages. 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cert group | Cert count | Cert ID | Cert type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Certificate / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 768 Length Length in octets, excluding Type, Length, and Padding Cert group Group ID grouping multiple related CERT parameters Cert count Total count of certificates that are sent, possibly in several consecutive HIP control packets. Cert ID The sequence number for this certificate Cert Type Describes the type of the certificate Padding Any Padding, if necessary, to make the TLV a multiple of 8 bytes. The following certificate types are defined: +-------------+-------------+ | Cert format | Type number | +-------------+-------------+ | SPKI | 1 | | X.509.v3 | 2 | +-------------+-------------+ All implementations MUST support SPKI. The next section outlines the use of HITs in SPKI. The wire formats for SPKI are defined in [SEXP].The encoding format for X.509.v3 certificate is defined Heer & Varjonen Expires August 21, 2008 [Page 3] Internet-Draft HIP CERT February 2008 elsewhere [RFC3280]. 3. SPKI cert object and Host Identities When using SPKI certificates to transmit information relating to HIP hosts, HITs need to be enclosed within the certificates. In the following we define the representation of those identifiers for SPKI given as S-expressions. Note that S-expressions are only the human- readable representation of SPKI certificates. The Host Identity Tag of a host is expressed as follows: Format: (hash hit hit-of-host) Example: (hash hit 2001:13:724d:f3c0:6ff0:33c2:15d8:5f50) Below is a simple example of SPKI cert object with HIP content. (cert (issuer (hash hit 2001:14:fd64:ca3b:9ef2:8374:ec80:4f20)) (subject (hash hit 2001:13:724d:f3c0:6ff0:33c2:15d8:5f50)) (tag (arg ) ... (tag (arg ) (propagate) (online crl http://www.issuersdomain.net/crl) (not before 1/1/2008) (not after 12/31/2008) ) The certificate object has HITs encoded into issuer and subject fields. Otherwise it is as defined in [SPKI.structure] and [RFC2693] 4. IANA Considerations This document defines the CERT parameter for the Host Identity Protocol [I-D.ietf-hip-base]. This parameter is defined in Section 2 with type 768. The parameter type number is also defined in [I-D.ietf-hip-base]. The Cert Group and Cert ID namespaces are managed locally by each peer that sends CERT parameters in HIP packets. Heer & Varjonen Expires August 21, 2008 [Page 4] Internet-Draft HIP CERT February 2008 5. Security Considerations Certificate grouping allows the certificates to be sent in multiple consecutive packets. This might allow similar attacks that fragmentation allows, i.e. sending of fragments in wrong order and skipping some fragments in order to leave the recipient waiting something that never comes. This problem can be alleviated by rate limiting HIP control packets Using CERT parameter in I1 is not recommended, because it may lead to workload on the responder. This workload may lead to a denial-of- service attack. 6. Acknowledgements The authors would like to thank M. Komu and T. Henderson of fruitful conversations on the subject. 7. Normative References [I-D.ietf-hip-base] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson, "Host Identity Protocol", draft-ietf-hip-base-10 (work in progress), October 2007. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2693] Ellison, C., Frantz, B., Lampson, B., Rivest, R., Thomas, B., and T. Ylonen, "SPKI Certificate Theory", RFC 2693, September 1999. [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. [SEXP] Rivest, R., "Code and description of S-expressions", . [SPKI.structure] Ellison, C., "Simple Public Key Certificate", . Heer & Varjonen Expires August 21, 2008 [Page 5] Internet-Draft HIP CERT February 2008 Authors' Addresses Tobias Heer Distributed Systems Group, RWTH Aachen University Ahornstrasse 55 Aachen Germany Phone: +49 241 80 214 36 Email: heer@cs.rwth-aachem.de URI: http://ds.cs.rwth-aachen.de/members/heer Samu Varjonen Helsinki Institute for Information Technology Metsnneidonkuja 4 Helsinki Finland Fax: +35896949768 Email: samu.varjonen@hiit.fi URI: http://www.hiit.fi Heer & Varjonen Expires August 21, 2008 [Page 6] Internet-Draft HIP CERT February 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). Heer & Varjonen Expires August 21, 2008 [Page 7]