[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-pmohapat-sidr-pfx-validate) 00 01 02 03 04 05 06 07 08 09 10 RFC 6811

Network Working Group                                  P. Mohapatra, Ed.
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                         J. Scudder, Ed.
Expires: May 3, 2012                                        D. Ward, Ed.
                                                        Juniper Networks
                                                            R. Bush, Ed.
                                         Internet Initiative Japan, Inc.
                                                         R. Austein, Ed.
                                             Internet Systems Consortium
                                                        October 31, 2011


                      BGP Prefix Origin Validation
                    draft-ietf-sidr-pfx-validate-03

Abstract

   To help reduce well-known threats against BGP including prefix mis-
   announcing and monkey-in-the-middle attacks, one of the security
   requirements is the ability to validate the origination AS of BGP
   routes.  More specifically, one needs to validate that the AS number
   claiming to originate an address prefix (as derived from the AS_PATH
   attribute of the BGP route) is in fact authorized by the prefix
   holder to do so.  This document describes a simple validation
   mechanism to partially satisfy this requirement.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on May 3, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




Mohapatra, et al.          Expires May 3, 2012                  [Page 1]

Internet-Draft        BGP Prefix Origin Validation          October 2011


   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.






























Mohapatra, et al.          Expires May 3, 2012                  [Page 2]

Internet-Draft        BGP Prefix Origin Validation          October 2011


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  5
   2.  Prefix-to-AS Mapping Database  . . . . . . . . . . . . . . . .  5
     2.1.  Pseudo-Code  . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Policy Control . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  Interaction with Local Cache . . . . . . . . . . . . . . . . .  9
   5.  Deployment Considerations  . . . . . . . . . . . . . . . . . .  9
   6.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
     10.2. Informational References . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12


































Mohapatra, et al.          Expires May 3, 2012                  [Page 3]

Internet-Draft        BGP Prefix Origin Validation          October 2011


1.  Introduction

   A BGP route associates an address prefix with a set of autonomous
   systems (AS) that identify the interdomain path the prefix has
   traversed in the form of BGP announcements.  This set is represented
   as the AS_PATH attribute in BGP [RFC4271] and starts with the AS that
   originated the prefix.  To help reduce well-known threats against BGP
   including prefix mis-announcing and monkey-in-the-middle attacks, one
   of the security requirements is the ability to validate the
   origination AS of BGP routes.  More specifically, one needs to
   validate that the AS number claiming to originate an address prefix
   (as derived from the AS_PATH attribute of the BGP route) is in fact
   authorized by the prefix holder to do so.  This document describes a
   simple validation mechanism to partially satisfy this requirement.

   The Resource Public Key Infrastructure (RPKI) describes an approach
   to build a formally verifyable database of IP addresses and AS
   numbers as resources.  The overall architecture of RPKI as defined in
   [I-D.ietf-sidr-arch] consists of three main components:

   o  A public key infrastructure (PKI) with the necessary certificate
      objects,

   o  Digitally signed routing objects,

   o  A distributed repository system to hold the objects that would
      also support periodic retrieval.

   The RPKI system is based on resource certificates that define
   extensions to X.509 to represent IP addresses and AS identifiers
   [RFC3779], thus the name RPKI.  Route Origin Authorizations (ROA)
   [I-D.ietf-sidr-roa-format] are separate digitally signed objects that
   define associations between ASes and IP address blocks.  Finally the
   repository system is operated in a distributed fashion through the
   IANA, RIR hierarchy, and ISPs.

   In order to benefit from the RPKI system, it is envisioned that
   relying parties either at AS or organization level obtain a local
   copy of the signed object collection, verify the signatures, and
   process them.  The cache must also be refreshed periodically.  The
   exact access mechanism used to retrieve the local cache is beyond the
   scope of this document.

   Individual BGP speakers can utilize the processed data contained in
   the local cache to validate BGP announcements.  The protocol details
   to retrieve the processed data from the local cache to the BGP
   speakers is beyond the scope of this document (refer to
   [I-D.ietf-sidr-rpki-rtr] for such a mechanism).  This document



Mohapatra, et al.          Expires May 3, 2012                  [Page 4]

Internet-Draft        BGP Prefix Origin Validation          October 2011


   proposes a means by which a BGP speaker can make use of the processed
   data in order to assign a "validity state" to each prefix in a
   received BGP UPDATE message.

   Note that the complete path attestation against the AS_PATH attribute
   of a route is outside the scope of this document.

   Although RPKI provides the context for this draft, it is equally
   possible to use any other database which is able to map prefixes to
   their authorized origin ASes.  Each distinct database will have its
   own particular operational and security characteristics; such
   characteristics are beyond the scope of this document.

1.1.  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].


2.  Prefix-to-AS Mapping Database

   The BGP speaker loads validated objects from the cache into local
   storage.  The objects loaded have the content (IP address, prefix
   length, maximum length, origin AS number).  We refer to such a
   locally stored object colloquially as a "ROA" in the discussion below
   although we note that this is not a strictly accurate use of the
   term.

   We define several terms in addition to "ROA".  Where these terms are
   used, they are capitalized:

   o  Prefix: (IP address, prefix length), interpreted as is customary
      (see [RFC4632]).

   o  Route: Data derived from a received BGP UPDATE, as defined in
      [RFC4271], Section 1.1.  The Route includes one Prefix and an
      AS_PATH, among other things.

   o  ROA Prefix: The Prefix from a ROA.

   o  ROA ASN: The origin ASN from a ROA.

   o  Route Prefix: A Prefix derived from a route.

   o  Route Origin ASN: The origin AS number derived from a Route.  The
      origin AS number is the rightmost AS in the final segment of the
      AS_PATH attribute in the Route if that segment is of type



Mohapatra, et al.          Expires May 3, 2012                  [Page 5]

Internet-Draft        BGP Prefix Origin Validation          October 2011


      AS_SEQUENCE, or NONE if the final segment of the AS_PATH attribute
      is of any type other than AS_SEQUENCE.  No ROA can match an origin
      AS number of "NONE".  No Route can match a ROA whose origin AS
      number is zero.

   o  Covered: A Route Prefix is said to be Covered by a ROA when the
      ROA prefix length is less than or equal to the Route prefix length
      and the ROA prefix address matches the Route prefix address for
      all bits specified by the ROA prefix length.  (This is simply a
      statement of the well-known concept of determining a prefix
      match.)

   o  Matched: A Route Prefix is said to be Matched by a ROA when the
      Route Prefix is Covered by that ROA and in addition, the Route
      prefix length is less than or equal to the ROA maximum length and
      the Route Origin ASN is equal to the ROA ASN, keeping in mind that
      a ROA ASN of zero can never be matched, nor can a route origin AS
      number of "NONE".

   Given these definitions, any given BGP Route learned from an EBGP
   peer will be found to have one of the following "validation states":

   o  Not found: No ROA Covers the Route Prefix.

   o  Valid: At least one ROA Matches the Route Prefix.

   o  Invalid: At least one ROA Covers the Route Prefix, but no ROA
      Matches it.

   When a BGP speaker receives an UPDATE from one of its EBGP peers, it
   SHOULD perform a lookup as described above for each of the Routes in
   the UPDATE message.  The "validation state" of the Route SHOULD be
   set to reflect the result of the lookup.  Note that the validation
   state of the Route does not determine whether the Route is stored in
   the local BGP speaker's Adj-RIB-In.  This procedure SHOULD NOT be
   performed for Routes learned from peers of types other than EBGP.
   (Any of these MAY be overridden by configuration.)

   Use of the validation state is discussed in Section 3 and Section 5.

   We observe that a Route can be Matched or Covered by more than one
   ROA.  This procedure does not mandate an order in which ROAs must be
   visited; however, the "validation state" output is fully determined.

2.1.  Pseudo-Code

   The following pseudo-code illustrates the procedure above.  In case
   of ambiguity, the procedure above, rather than the pseudo-code,



Mohapatra, et al.          Expires May 3, 2012                  [Page 6]

Internet-Draft        BGP Prefix Origin Validation          October 2011


   should be taken as authoritative.


















































Mohapatra, et al.          Expires May 3, 2012                  [Page 7]

Internet-Draft        BGP Prefix Origin Validation          October 2011


   //Input are the variables derived from a BGP UPDATE message
   //that need to be validated.
   //
   //The input prefix is comprised of prefix.address and
   //prefix.length.
   //
   //origin_as is the rightmost AS in the final segment of the
   //AS_PATH attribute in the UPDATE message if that segment is
   //AS_SEQUENCE.  If the final segment of AS_PATH is not an
   //AS_SEQUENCE, origin_as is NONE.
   //
   //Collectively, the prefix and origin_as correspond to the
   //Route defined in the preceding section.
   input = {prefix, origin_as};

   //Initialize result to "not found" state
   result = BGP_PFXV_STATE_NOT_FOUND;

   //pfx_validate_table organizes all the ROA entries retrieved
   //from the RPKI cache based on the IP address and the prefix
   //length field. There can be multiple such entries that match
   //the input. Iterate through all of them.
   entry = next_lookup_result(pfx_validate_table, input.prefix);

   while (entry != NULL) {
       prefix_exists = TRUE;

       if (input.prefix.length <= entry->max_length) {
           if (input.origin_as != NONE
               && entry->origin_as != 0
               && input.origin_as == entry->origin_as) {
               result = BGP_PFXV_STATE_VALID;
               return (result);
           }
       }
       entry = next_lookup_result(pfx_validate_table, input.prefix);
   }

   //If pfx_validate_table contains one or more prefixes that
   //match the input, but none of them resulted in a "valid"
   //outcome since the origin_as did not match, return the
   //result state as "invalid". Else the initialized state of
   //"not found" applies to this validation operation.
   if (prefix_exists == TRUE) {
       result = BGP_PFXV_STATE_INVALID;
   }

   return (result);



Mohapatra, et al.          Expires May 3, 2012                  [Page 8]

Internet-Draft        BGP Prefix Origin Validation          October 2011


3.  Policy Control

   An implementation MUST provide the ability to match and set the
   validation state of routes as part of its route policy filtering
   function.  Use of validation state in route policy is elaborated in
   Section 5.  For more details on operational policy considerations,
   see [I-D.ietf-sidr-origin-ops].


4.  Interaction with Local Cache

   Each BGP speaker supporting prefix validation as described in this
   document is expected to communicate with one or multiple local caches
   that store a database of RPKI signed objects.  The protocol
   mechanisms used to fetch the data and store them locally at the BGP
   speaker is beyond the scope of this document (please refer
   [I-D.ietf-sidr-rpki-rtr]).  Irrespective of the protocol, the prefix
   validation algorithm as outlined in this document is expected to
   function correctly in the event of failures and other timing
   conditions that may result in an empty and/or partial prefix-to-AS
   mapping database.  Indeed, if the (in-PoP) cache is not available and
   the mapping database is empty on the BGP speaker, all the lookups
   will result in "not found" state and the prefixes will be advertised
   to rest of the network (unless restricted by policy configuration).
   Similarly, if BGP UPDATEs arrive at the speaker while the fetch
   operation from the cache is in progress, some prefix lookups will
   also result in "not found" state.  The implementation is expected to
   handle these timing conditions and MUST re-validate affected prefixes
   once the fetch operation is complete.  The same applies during any
   subsequent incremental updates of the validation database.

   In the event that connectivity to the cache is lost, the router
   should make a reasonable effort to fetch a new validation database
   (either from the same, or a different cache), and SHOULD wait until
   the new validation database has been fetched before purging the
   previous one.  A configurable timer MUST be provided to bound the
   length of time the router will wait before purging the previous
   validation database.


5.  Deployment Considerations

   Once a route is received from an EBGP peer it is categorized
   according the procedure given in Section 2.  Subsequently, routing
   policy as discussed in Section 3 can be used to take action based on
   the validation state.

   Policies which could be implemented include filtering routes based on



Mohapatra, et al.          Expires May 3, 2012                  [Page 9]

Internet-Draft        BGP Prefix Origin Validation          October 2011


   validation state (for example, rejecting all "invalid" routes) or
   adjusting a route's degree of preference in the selection algorithm
   based on its validation state.  The latter could be accomplished by
   adjusting the value of such attributes as LOCAL_PREF.  Considering
   invalid routes for BGP decision process is a pure local policy matter
   and should be done with utmost care.

   In some cases (particularly when the selection algorithm is
   influenced by the adjustment of a route property that is not
   propagated into IBGP) it could be necessary for routing correctness
   to propagate the validation state to the IBGP peer.  This can be
   accomplished on the sending side by setting a community or extended
   community based on the validation state, and on the receiving side by
   matching the (extended) community and setting the validation state.


6.  Contributors

      Rex Fernando rex@cisco.com
      Keyur Patel keyupate@cisco.com
      Cisco Systems

      Miya Kohno mkohno@juniper.net
      Juniper Networks

      Shin Miyakawa miyakawa@nttv6.jp
      Taka Mizuguchi
      Tomoya Yoshida
      NTT Communications

      Russ Housley housley@vigilsec.com
      Vigil Security

      Junaid Israr jisra052@uottawa.ca
      Mouhcine Guennoun mguennou@uottawa.ca
      Hussein Mouftah mouftah@site.uottawa.ca
      University of Ottawa School of Information Technology and
      Engineering(SITE) 800 King Edward Avenue, Ottawa, Ontario, Canada,
      K1N 6N5


7.  Acknowledgements

   Junaid Israr's contribution to this specification is part of his PhD
   research work and thesis at University of Ottawa, Canada.  Hannes
   Gredler provided valuable feedback.





Mohapatra, et al.          Expires May 3, 2012                 [Page 10]

Internet-Draft        BGP Prefix Origin Validation          October 2011


8.  IANA Considerations


9.  Security Considerations

   Although this specification discusses one portion of a system to
   validate BGP routes, it should be noted that it relies on a database
   (RPKI or other) to provide validation information.  As such, the
   security properties of that database must be considered in order to
   determine the security provided by the overall solution.  If
   "invalid" routes are blocked as this specification suggests, the
   overall system provides a possible denial-of-service vector, for
   example if an attacker is able to inject one or more spoofed records
   into the validation database which lead a good route to be declared
   invalid.  In addition, this system is only able to provide limited
   protection against a determined attacker -- the attacker need only
   prepend the "valid" source AS to a forged BGP route announcement in
   order to defeat the protection provided by this system.  This
   mechanism does not protect against "AS in the middle attacks" or
   provide any path validation.  It only attempts to verify the origin.
   In general, this system should be thought of more as a protection
   against misconfiguration than as true "security" in the strong sense.


10.  References

10.1.  Normative References

   [I-D.ietf-sidr-roa-format]
              Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
              Origin Authorizations (ROAs)",
              draft-ietf-sidr-roa-format-12 (work in progress),
              May 2011.

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

   [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.

   [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
              (CIDR): The Internet Address Assignment and Aggregation
              Plan", BCP 122, RFC 4632, August 2006.





Mohapatra, et al.          Expires May 3, 2012                 [Page 11]

Internet-Draft        BGP Prefix Origin Validation          October 2011


10.2.  Informational References

   [I-D.ietf-sidr-arch]
              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch-13 (work in
              progress), May 2011.

   [I-D.ietf-sidr-origin-ops]
              Bush, R., "RPKI-Based Origin Validation Operation",
              draft-ietf-sidr-origin-ops-12 (work in progress),
              October 2011.

   [I-D.ietf-sidr-rpki-rtr]
              Bush, R. and R. Austein, "The RPKI/Router Protocol",
              draft-ietf-sidr-rpki-rtr-19 (work in progress),
              October 2011.


Authors' Addresses

   Pradosh Mohapatra (editor)
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: pmohapat@cisco.com


   John Scudder (editor)
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   USA

   Email: jgs@juniper.net


   David Ward (editor)
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   USA

   Email: dward@juniper.net






Mohapatra, et al.          Expires May 3, 2012                 [Page 12]

Internet-Draft        BGP Prefix Origin Validation          October 2011


   Randy Bush (editor)
   Internet Initiative Japan, Inc.
   5147 Crystral Springs
   Bainbridge Island, Washington  98110
   USA

   Email: randy@psg.com


   Rob Austein (editor)
   Internet Systems Consortium
   950 Charter Street
   Redwood City, CA  94063
   USA

   Email: sra@isc.org



































Mohapatra, et al.          Expires May 3, 2012                 [Page 13]


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/