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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 24, 2009                                         Varjonen
                                      Helsinki Institute for Information
                                                              Technology
                                                        October 21, 2008


                            HIP Certificates
                         draft-ietf-hip-cert-00

Status of this Memo

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   This Internet-Draft will expire on April 24, 2009.

Abstract

   This document specifies a certificate parameter called CERT for the
   Host Identity Protocol (HIP).  The CERT parameter is a container for
   Simple Public Key Infrastructure (SPKI) and X.509.v3 certificates.
   It is used for carrying these certificates in HIP control messages.
   Additionally, this document specifies the representations of Host
   Identity Tags in SPKI and X.509.v3 certificates.



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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 the CERT parameter that
   is used to transmit digital signatures in HIP.  It corresponds to the
   placeholder specified in Section 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.

   Each HIP packet may contain multiple CERT parameters.  If these
   parameters must be handled in certain 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
   fields in a packet.  Within a HIP packet, CERT parameters must be
   placed in ascending order 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.




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   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 R1, I2, R2, UPDATE and NOTIFY
   messages.  When CERT parameter is used in R1 message it is NOT
   recommended to use grouping or hash and URL encodings.  Initiator and
   Responder can detect middleboxes on the path after R1 message is sent
   by checking if control packets contain ECHO_REQUEST_M parameters as
   defined in [HIP.middle_auth].


     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 |
                +--------------------------+-------------+
                |           SPKI           |      1      |
                |         X.509.v3         |      2      |
                |   Hash and URL of SPKI   |      3      |
                | Hash and URL of X.509.v3 |      4      |
                +--------------------------+-------------+

   All implementations MUST support SPKI.  The next section outlines the
   use of HITs in SPKI.  The SPKI and its formats are defined in
   [RFC2693].  X.509.v3 certificates are defined in [RFC3280].  Wire
   format for X.509.v3 is Distinguished Encoding Rules format as defined
   in [X.690].

   Hash and URL encodings (3 and 4) 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.

   It is not recommended to use hash and URL encodings when HIP-aware
   middleboxes are present on the communication path between peers
   because fetching remote certificates requires 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.


3.  SPKI Cert Object and Host Identities

   When using SPKI certificates to transmit information related 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 the S-expressions are only the
   human-readable representation 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)

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






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

   When using X.509.v3 certificates to transmit information related to
   HIP hosts, HITs need to be enclosed within the certificates.  HITs
   are represented as issuer and subject alternative name X.509.v3
   extensions as defined in [RFC2459].  Because the Distinguished Name
   (DN) in X.509.v3 certificate cannot be empty HITs are also placed
   into the Common Name (CN) in a colon delimited presentation format.

   As an example the HIT of a host is 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.


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.  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



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   Cert Group and Cert ID namespaces are managed locally by each peer
   that sends CERT parameters in HIP packets.


7.  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).


8.  Acknowledgements

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


9.  References

9.1.  Normative References

   [HIP.middle_auth]
              Heer, T., "End-Host Authentication for HIP Middleboxes",
              <draft-heer-hip-middle-auth-00.txt>.

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



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9.2.  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://
              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=|
     )
   )






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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.


   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





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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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