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Versions: (draft-huston-sidr-roa-validation) 00 01 02 03 04 05 06 07 08 09 10 RFC 6483

Secure Inter-Domain Routing (SIDR)                             G. Huston
Internet-Draft                                             G. Michaelson
Intended status: Informational                                     APNIC
Expires: September 4, 2010                                 March 3, 2010


 Validation of Route Origination using the Resource Certificate PKI and
                                  ROAs
                 draft-ietf-sidr-roa-validation-04.txt

Abstract

   This document defines the semantics of a Route Origin Authorization
   in terms of the context of an application of the Resource Public Key
   Infrastructure to validate the origination of routes advertised in
   the Border Gateway Protocol.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 4, 2010.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  ROA Validation Outcomes for a Route Object  . . . . . . . . . . 3
   3.  Applying Validation Outcomes to Route Selection . . . . . . . . 5
   4.  Disavowal of Routing Origination  . . . . . . . . . . . . . . . 6
   5.  Route Object Validation Lifetime  . . . . . . . . . . . . . . . 7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8






























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1.  Introduction

   This document defines the semantics of a Route Origin Authorization
   (ROA) in terms of the context of an application of the Resource
   Public Key Infrastructure (RPKI) [I-D.ietf-sidr-arch] to validate the
   origination of routes advertised in the Border Gateway Protocol (BGP)
   [RFC4271].

   The RPKI is based on a hierarchy of Resource Certificates that are
   aligned to the Internet number resource allocation structure.
   Resource Certificates are X.509 certificates that conform to the PKIX
   profile [RFC5280], and to the extensions for IP addresses and AS
   identifiers [RFC3779].  A Resource Certificate describes an action by
   an issuer that binds a list of IP address blocks and Autonomous
   System (AS) numbers to the Subject of a certificate, identified by
   the unique association of the Subject's private key with the public
   key contained in the Resource Certificate.  The RPKI is structured
   such that each current Resource Certificate matches a current
   resource allocation or assignment.  This is further described in
   [I-D.ietf-sidr-arch].

   ROAs are digitally signed objects that bind an address to an AS
   number, signed by the address holder.  A ROA provides a means of
   verifying that an IP address block holder has authorized a particular
   AS to originate route objects in the inter-domain routing environment
   for that address block.  ROAs are described in
   [I-D.ietf-sidr-roa-format].  ROAs are intended to fit within the
   requirements for adding security to inter-domain routing.

   This document describes the semantic interpretation of a ROA, with
   particular reference to application in inter-domain routing relating
   to the origination of route objects, and the intended scope of the
   authority that is conveyed in the ROA.


2.  ROA Validation Outcomes for a Route Object

   A "route object" is an address prefix and an associated set of
   routing attributes.  In terms of validation of the route object in
   the context of BGP [RFC4271]the address prefix value and the "origin
   AS" are used in the ROA validation operation.  The route object's
   origin AS is the final element of the route object's AS_PATH
   attribute.  If the final AS_PATH element is an AS Set, indicating
   that the route object is an aggregate, then the origin AS is taken as
   the AS component of the AGGREGATOR attribute [RFC4271].

   It is assumed here that a Relying Party (RP) has access to a local
   cache of the complete set of valid ROAs when performing validation of



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   a route object.  (Valid ROAs are defined as ROAs that are determined
   to be syntactically correct and are signed using a signature that can
   be verified using the RPKI, as described in
   [I-D.ietf-sidr-roa-format].)  The RP needs to match a route object to
   one or more candidate valid ROAs in order to determine a validation
   outcome, which, in turn, can be used to determine the appropriate
   local actions to perform on the route object.

   This approach to route object origination validation uses a model of
   "positive" attestations, where route objects that cannot be validated
   within the RPKI framework would conventionally be treated by a RP as
   "invalid".  However, the considerations of accommodating environments
   of partial adoption of the use of ROAs, where only a subset of
   validly advertised address prefixes have associated published ROAs
   within the structure of the RPKI, imply some modification to this
   model of positive attestation.  In the context of route object
   validation it is assumed that once an address prefix is described in
   a ROA, then this ROA speifically encompasses all address prefixes
   that are more specific than that described in the ROA.  Thus, any
   route object for more specific address prefix than that described by
   any valid ROA that does not itself have a matching valid ROA is
   considered to be "invalid".  However, routes objects for address
   prefixes that are not fully described by any single ROA, i.e., those
   route objects whose address prefixes may be an aggregate of address
   prefixes described in a valid ROA, or have address prefixes where
   there is no intersection with any ROA, and are not matched by any ROA
   and are not a more specific of any ROA cannot be reliably classified
   as "invalid" in a partial deployment scenario.  Such route objects
   have a validation outcome of "unknown".

   The validation condition of a route object with a prefix and an
   origin AS when using single ROA for validation is summarized in the
   following table:


   Prefix      matching   non-matching
               AS         AS
              +---------+-------------+
   Covering   | unknown | unknown     |
   Aggregate  |         |             |
              +---------+-------------+
   match ROA  | valid   | invalid     |
   prefix     |         |             |
              +---------+-------------+
   More       | invalid | invalid     |
   Specific   |         |             |
   than ROA   |         |             |
              +---------+-------------+



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   In an environment of a collection of ROAs, a route object is
   considered to be "valid" if any ROA provides a "valid" outcome.  It
   is considered to be "invalid" if one (or more) ROAs provide an
   "invalid" outcome and no ROAs provide a "valid" outcome.  It is
   considered to be "unknown" when no ROA produces either a "valid" or
   an "invalid" outcome.

   Route object validation is defined by the following procedure:


      1.  Select all valid ROAs that include a ROAIPAddress value that
          either matches, or is a covering aggregate of, the address
          prefix in the route object.

      2.  If the set of candidate ROAs is empty then the validation
          procedure stops with an outcome of "unknown".

      3.  If any of the selected ROAs has an asID value that matches the
          origin AS in the route object, and either the route object's
          address prefix precisely matches a ROAIPAddress in the ROA, or
          the route object's address prefix is a more specific prefix of
          a ROAIPAddress, and the route object's prefix length value is
          less than or equal to the ROAIPAddress' maxLength value, then
          the validation procedure stops with an outcome of "valid".

      4.  Otherwise, the validation procedure stops with an outcome of
          "invalid".


3.  Applying Validation Outcomes to Route Selection

   Within the framework of the abstract model of the operation of inter-
   domain routing using BGP [RFC4271], a received prefix announcement
   from a routing peer is compared to all announcements for this prefix
   received from other routing peers and a route selection procedure is
   used to select the "best" route object from this candidate set.

   The route object validation outcome, described in Section 2, of
   "unknown", "valid" or "invalid" may be used as part of the
   determination of the local degree of preference, in which case the
   local order of preference is as follows:
      "valid" is to be preferred over
      "unknown", which itself is to be preferred over
      "invalid".

   It is a matter of local routing policy as to the actions to be
   undertaken by a routing entity in processing route objects with
   "unknown" validation outcomes.  Due to considerations of partial use



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   of ROAs in heterogeneous environments, such as in the public
   Internet, it is advised that local policy settings should not result
   in "unknown" validation outcomes being considered as sufficient
   grounds to reject a route object outright from further consideration
   as a local "best" route.

   It is a matter of local routing policy as to whether "invalid" route
   objects are considered to be ineligible for further consideration in
   a route selection process.  A possible consideration here is one of
   potential circularity of dependence.  If the authoritative
   publication point of the repository of ROAs, or that of any
   certificate used in relation to an address prefix, is located at an
   address that lies within the address prefix described in a ROA, then
   the repository can only be accessed by the RP once a route for the
   prefix has been accepted by the RP's local routing domain.  It is
   also noted that the propagation time of RPKI objects may be different
   to the propagation time of route objects, and that route objects may
   be received before the RP's local repository cache picks up the
   associated ROAs and recognises them as valid within the RPKI.


4.  Disavowal of Routing Origination

   A ROA is a positive attestation that a prefix holder has authorized
   an AS to originate a route for this prefix into the inter-domain
   routing system.  It is possible for a prefix holder to construct an
   authorization where no valid AS has been granted any such authority
   to originate a route object for an address prefix.  This is acheived
   by using a ROA where the ROA's subject AS is one that must never be
   used in any routing context.  Specifically, AS 0 is reserved by the
   IANA such that it "may be use [sic] to identify non-routed networks"
   [IANA.AS-Registry].

   A ROA with a subject of AS 0 is an attestation by the holder of a
   prefix that the prefix described in the ROA, and any more specific
   prefix, SHOULD NOT be used in a routing context.

   The route object validation procedure, described in Section 2, will
   provide a "valid" outcome if any ROA matches the address prefix and
   origin AS, even if other valid ROAs would provide an "invalid"
   validation outcome if used in isolation.  Consequently, an AS 0 ROA
   has a lower preference than any other ROA that has a routeable AS as
   its subject.  This allows a prefix holder to use an AS 0 ROA to
   declare a default condition that any route object that is equal to,
   or more specific than the prefix to be considered to be invalid,
   while also allowing other concurrently issued ROAs to describe valid
   origination authorizations for more specific prefixes.




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   By convention, an AS 0 ROA SHOULD have a maxLength value of 32 for
   IPv4 addresses and 128 for IPv6 addresses, although in terms of route
   object validation the same outcome would be achieved with any valid
   maxLength value, or even if the maxLength element were to be omitted
   from the ROA.

   Also by convention, an AS 0 ROA SHOULD be the only ROA issued for a
   given address prefix, although again this is not a strict
   requirement.  An AS 0 ROA can coexist with ROAs that have different
   subject AS values, although in such cases the presence of the AS 0
   ROA does not alter the route object validation outcome in any way.


5.  Route Object Validation Lifetime

   The "lifetime" of a validation outcome refers to the time period
   during which the original validation outcome can be still applied.
   The implicit assumption here is that when the validation lifetime
   expires the routing object SHOULD be re-tested for validity.

   The validation lifetime for a ROA is controlled by the Valid times
   specified in the End Entity (EE) Certificate used to sign the ROA,
   and the valid times of those certificates in the certification path
   used to validate the EE Certificate.  A ROA validation "expires" at
   the Validity To field of the signing EE certificate, or at such a
   time when there is no certification path that can validate the ROA.
   A ROA issuer may prematurely invalidate a ROA by revoking the EE
   certificate that was used to sign the ROA.


6.  Security Considerations

   ROA issuers should be aware of the validation implication in issuing
   a ROA, in that a ROA implicitly invalidates all route objects that
   have more specific prefixes with a prefix length greater than
   maxLength, and all originating AS's other than the AS listed in the
   collection of ROAs for this prefix.

   A conservative operational practice would be to ensure the issuing of
   ROAs for all more specific prefixes with distinct origination AS's
   prior to the issuing of ROAs for larger encompassing address blocks,
   in order to avoid inadvertent invalidation of valid route objects
   during ROA generation.

   ROA issuers should also be aware that if they generate a ROA for one
   origin AS, then if the prefix holder authorises multiple AS's to
   originate route objects it is necessary for a ROA be generated for
   every such authorized AS.



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7.  IANA Considerations

   [There are no IANA Considerations.]


8.  References

8.1.  Normative References

   [I-D.ietf-sidr-arch]
              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch (work in
              progress), October 2009.

   [I-D.ietf-sidr-roa-format]
              Lepinski, M., Kent, S., and D. Kong, "An Infrastructure to
              Support Secure Internet Routing",
              draft-ietf-sidr-roa-format (work in progress),
              October 2009.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 2004.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

8.2.  Informative References

   [IANA.AS-Registry]
              IANA, "IANA Autonomous System Number Registry",
              March 2010.


Authors' Addresses

   Geoff Huston
   Asia Pacific Network Information Centre

   Email: gih@apnic.net







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   George Michaelson
   Asia Pacific Network Information Centre

   Email: ggm@apnic.net















































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