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Versions: 00 01 draft-ietf-hip-cert

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

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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



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   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



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   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



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   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 <capability-name_1> (arg <arg_1>)
         ...
        (tag <capability-name_n> (arg <arg_n>)
        (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.







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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",
              <http://theory.lcs.mit.edu/~rivest/sexp.html>.

   [SPKI.structure]
              Ellison, C., "Simple Public Key Certificate",
              <draft-ietf-spki-cert-structure-06.txt>.






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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





























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Acknowledgment

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