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Versions: (draft-varjonen-hip-cert) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 6253

Host Identity Protocol                                              Heer
Internet-Draft                           Distributed Systems Group, RWTH
Intended status: Informational                         Aachen University
Expires: April 29, 2010                                         Varjonen
                                      Helsinki Institute for Information
                                                              Technology
                                                        October 26, 2009


                            HIP Certificates
                         draft-ietf-hip-cert-02

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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Abstract

   This document specifies a certificate parameter called CERT for the
   Host Identity Protocol (HIP).  The CERT parameter is a container for
   X.509.v3 certificates and for Simple Public Key Infrastructure (SPKI)
   certificates.  It is used for carrying these certificates in HIP
   control packets.  Additionally, this document specifies the
   representations of Host Identity Tags in X.509.v3 and 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)[RFC5201] 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 a CERT parameter that is
   used to transmit digital signatures in HIP.  It fills the placeholder
   specified in Section 5.2 of [RFC5201].


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 some organizational parameters that help HIP
   hosts to transmit semantically grouped parameters in a more
   systematic way.

   The CERT parameter may be covered by the HIP SIGNATURE field and is a
   non-critical parameter.

   The CERT parameter can be used in R1, I2, R2, UPDATE and NOTIFY
   control packets.  Each allowed HIP control packet may contain
   multiple CERT parameters.  These parameters may be related or
   unrelated.  Related certificates are managed in Cert groups.  A Cert
   group specifies a group of related CERT parameters that should be
   interpreted in a certain order (e.g. for expressing certificate



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   chains).  For grouping CERT parameters, 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 CERT
   parameters in the group.

   CERT parameters that belong to the same Cert group may be contained
   in multiple sequential HIP control packets.  This is indicated by a
   higher Cert count than the amount of CERT parameters with matching
   Cert group fields in a HIP control packet.  The CERT parameters must
   be placed in ascending order, within a HIP control packet, according
   to 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.


     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:






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             +--------------------------------+-------------+
             |           Cert format          | Type number |
             +--------------------------------+-------------+
             |            X.509.v3            |      1      |
             |              SPKI              |      2      |
             |         URL of X.509.v3        |      3      |
             |           URL of SPKI          |      4      |
             |        Hash of X.509.v3        |      5      |
             |          Hash of SPKI          |      6      |
             |      LDAP URL of X.509.v3      |      7      |
             |        LDAP URL of SPKI        |      8      |
             | Distinguished Name of X.509.v3 |      9      |
             |   Distinguished Name of SPKI   |      10     |
             +--------------------------------+-------------+

   Next sections outline the use of HITs in X.509.v3 and in SPKI
   certificates.  X.509.v3 certificates are defined in [RFC3280].  The
   Wire format for X.509.v3 is Distinguished Encoding Rules format as
   defined in [X.690].  The SPKI and its formats are defined in
   [RFC2693].

   Hash and URL encodings (3 to 6) are used as defined in [RFC4306].
   Using hash and URL encodings results in smaller HIP control packets,
   but requires the receiver to resolve the URL or check local cache
   against the hash.

   LDAP URL encoding (7 and 8) is used as defined in [RFC2255].  Using
   LDAP URL encoding results in smaller HIP control packets, but
   requires the receiver to retrieve the certificate or check local
   cache against the URL.

   Distinguished name (DN) encoding (9 and 10) is used as defined in
   [RFC1779].  Using LDAP URL encoding results in smaller HIP control
   packets, but requires the receiver to retrieve the certificate or
   check local cache against the DN.


3.  X.509.v3 Certificate Object and Host Identities

   HITs need to be enclosed within the certificates, when using X.509.v3
   certificates to transmit information related to HIP hosts.  HITs can
   represent an issuer, a subject, or both.  In X.509.v3 HITs are
   represented as issuer and subject alternative name extensions as
   defined in [RFC2459].  If only HIP information is presented as either
   the issuer or the subject the HIT is also placed into the respective
   entity's DNs Common Name (CN) section in a colon delimited
   presentation format.  Inclusion of CN is not necessary if DN contains
   any other information.  It is RECOMMENDED to use FQDN/NAI from the



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   hosts HOST_ID parameter in DN if one exists.  Full HIs are presented
   in the public key entries of X.509.v3 certificates.

   As an example, in a case where the issuer and the subject are both
   HIP enabled, the HITs are expressed as follows:


       Format:
           Issuer: CN=hit-of-host
           Subject: CN=hit-of-host

           X509v3 extensions:
               X509v3 Issuer Alternative Name:
                   IP Address:HIT-OF-HOST
               X509v3 Subject Alternative Name:
                   IP Address:HIT-OF-HOST

       Example:
           Issuer: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056
           Subject: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056

           X509v3 extensions:
               X509v3 Issuer Alternative Name:
                   IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056
               X509v3 Subject Alternative Name:
                   IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056

   Appendix B shows a full example X.509.v3 certificate with HIP
   content.


4.  SPKI Cert Object and Host Identities

   HITs need to be enclosed within the certificates, when using SPKI
   certificates to transmit information related to HIP hosts.  HITs can
   represent an issuer, a subject, or both.  In the following we define
   the representation of those identifiers for SPKI given as
   S-expressions.  Note that the S-expressions are only the human-
   readable representation of SPKI certificates.  Full HIs are presented
   in the public key sequences of SPKI certificates.

   As an example 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)




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   Appendix A shows a full example SPKI certificate with HIP content.


5.  Revocation of Certificates

   Revocation of SPKI certificates is handled as defined in Section 5.
   in [RFC2693] Revocation of X.509.v3 certificates is handled as
   defined in Section 5 in [RFC2459].


6.  Signaling

   HIP end-hosts and HIP-aware middleboxes need to inform, the initiator
   or the responder, of the need for a certificate or need for a chain
   of certificates.  They also need a way to inform about failing to
   meet required conditions.  HIP services [HIP.service] describes the
   signaling.  Signaling for the requirements and failures with
   certificates is described in Section 4.1 of [HIP.service].


7.  IANA Considerations

   This document defines the CERT parameter for the Host Identity
   Protocol [RFC5201].  This parameter is defined in Section 2 with type
   768.  The parameter type number is also defined in [RFC5201].  The
   Cert Group and Cert ID namespaces are managed locally by each host
   that sends CERT parameters in HIP control packets.


8.  Security Considerations

   Certificate grouping allows the certificates to be sent in multiple
   consecutive packets.  This might allow similar attacks as IP-layer
   fragmentation allows, i.e. sending of fragments in wrong order and
   skipping some fragments to delay or stall packet processing by the
   victim in order to use resources (e.g.  CPU or memory).

   It is not recommended to use grouping or hash and URL encodings when
   HIP-aware middleboxes are anticipated to be present on the
   communication path between peers because fetching remote certificates
   require the middlebox to buffer the packets and to request remote
   data.  This makes these devices prone to denial of service (DoS)
   attacks.  Moreover, middleboxes and responders that request remote
   certificates can be used as deflectors for distributed denial of
   service attacks.






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9.  Acknowledgements

   The authors would like to thank M. Komu and T. Henderson of fruitful
   conversations on the subject.


10.  References

10.1.  Normative References

   [HIP.service]
              Heer, T., Wirtz, H., and S. Varjonen, "Service Identifiers
              for HIP", <draft-heer-hip-service-00.txt>.

   [RFC1779]  Kille, S., "A String Representation of Distinguished
              Names", RFC 1779, March 1995.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2255]  Howes, T. and M. Smith, "The LDAP URL Format", RFC 2255,
              December 1997.

   [RFC2459]  Housley, R., Ford, W., Polk, T., and D. Solo, "Internet
              X.509 Public Key Infrastructure Certificate and CRL
              Profile", RFC 2459, January 1999.

   [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.

   [RFC4306]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.

   [RFC5201]  Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
              "Host Identity Protocol", RFC 5201, April 2008.

10.2.  Informative References

   [X.690]    ITU-T, "Recommendation X.690 Information Technology -
              ASN.1 encoding rules: Specification of Basic Encoding
              Rules (BER), Canonical Encoding Rules (CER) and
              Distinguished Encoding Rules (DER)", July 2002, <http://



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              www.itu.int/ITU-T/studygroups/com17/languages/
              X.690-0207.pdf>.


Appendix A.  SPKI certificate example

   This section shows a self-signed SPKI certificate of HIT 2001:14:6cf:
   fae7:bb79:bf78:7d64:c056.  The example has been indented for
   readability.


   (sequence
     (public_key
       (rsa-pkcs1-sha1
         (e #010001#)
         (n |n1CheoELqYRSkHYMQddub2TpILl+6H9wC/as6zFCZqOY43hsZgAjG0F
             GoQwtyOyQjzO2Ykb2TmUCZemTYui/sR0zIbdwg1xafKl7ggZDkhk5an
             PtGDxJxFalTYo6/A5ZQv8uatbaJgB/G7VM8G+O9HLucadad2zQUXpQf
             gbK3S8=|
         )
       )
     )
     (cert
       (issuer
         (hash hit 2001:0014:06cf:fae7:bb79:bf78:7d64:c056)
       )
       (subject
         (hash hit 2001:0014:06cf:fae7:bb79:bf78:7d64:c056)
       )
       (not-before "2008-07-12_22:11:07")
       (not-after "2008-07-22_22:11:07")
     )
     (signature
       (hash sha1 |kfElDhagiK0Bsqtj32Gq3t/1mxgA|)
       |HiIqjjZIUzypvoxQyO0UovPm5uC4Xte0scEcBnENDIfn2DNy/bAtxGEdKq4O
        dW80vTCmkF8/HXclgXLLVch3DxRNdSbYiiks000HpQt/OKqlTH+uUHBcHOAo
        E42LmDskM9T5KQJoC/CH7871zfvojPnpkl2dUngOWv4q0r/wSJ0=|
     )
   )


Appendix B.  X.509.v3 certificate example

   This section shows a self-signed X.509.v3 certificate of HIT 2001:14:
   6cf:fae7:bb79:bf78:7d64:c056.






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   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 0 (0x0)
           Signature Algorithm: sha1WithRSAEncryption
           Issuer: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056
           Validity
               Not Before: Jul 12 18:58:38 2008 GMT
               Not After : Jul 22 18:58:38 2008 GMT
           Subject: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056
           Subject Public Key Info:
               Public Key Algorithm: rsaEncryption
               RSA Public Key: (1024 bit)
                   Modulus (1024 bit):
                       00:9f:50:a1:7a:81:0b:a9:84:52:90:76:0c:41:d7:
                       6e:6f:64:e9:20:b9:7e:e8:7f:70:0b:f6:ac:eb:31:
                       42:66:a3:98:e3:78:6c:66:00:23:1b:41:46:a1:0c:
                       2d:c8:ec:90:8f:33:b6:62:46:f6:4e:65:02:65:e9:
                       93:62:e8:bf:b1:1d:33:21:b7:70:83:5c:5a:7c:a9:
                       7b:82:06:43:92:19:39:6a:73:ed:18:3c:49:c4:56:
                       a5:4d:8a:3a:fc:0e:59:42:ff:2e:6a:d6:da:26:00:
                       7f:1b:b5:4c:f0:6f:8e:f4:72:ee:71:a7:5a:77:6c:
                       d0:51:7a:50:7e:06:ca:dd:2f
                   Exponent: 65537 (0x10001)
           X509v3 extensions:
               X509v3 Basic Constraints:
                   CA:TRUE
               X509v3 Issuer Alternative Name:
                   IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056
               X509v3 Subject Alternative Name:
                   IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056
       Signature Algorithm: sha1WithRSAEncryption
           19:32:0b:72:a8:6c:f9:65:20:5b:1d:9a:e1:c7:39:97:c7:8a:
           4d:d1:01:f9:7d:0b:0d:6f:61:a2:e3:2c:62:30:28:f6:36:db:
           62:bc:7f:d1:9b:6d:cc:da:e3:9b:90:e7:53:9e:55:28:51:7e:
           39:de:23:24:f5:a9:97:7a:ba:ce:54:3e:cf:8b:68:04:f6:be:
           78:94:9f:d3:20:62:96:14:84:51:af:c7:ba:30:ae:b1:d6:7e:
           7f:32:42:9c:f6:f5:76:27:0a:28:58:8b:b5:85:e7:e9:5a:ff:
           aa:4c:57:55:95:09:33:ac:0b:8c:fd:05:4a:5e:60:e7:7f:d7:
           42:f0


Appendix C.  Change log

   Changes from version 00 to 01:

   o  Revised text about DN usage.




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   o  Revised text about Cert group usage.


Authors' Addresses

   Tobias Heer
   Distributed Systems Group, RWTH Aachen University
   Ahornstrasse 55
   Aachen
   Germany

   Phone: +49 241 80 214 36
   Email: heer@cs.rwth-aachen.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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