[Docs] [txt|pdf] [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: August 11, 2011                                    D. Ward, Ed.
                                                        Juniper Networks
                                                            R. Bush, Ed.
                                         Internet Initiative Japan, Inc.
                                                         R. Austein, Ed.
                                             Internet Systems Consortium
                                                        February 7, 2011


                      BGP Prefix Origin Validation
                    draft-ietf-sidr-pfx-validate-01

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 August 11, 2011.

Copyright Notice

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




Mohapatra, et al.        Expires August 11, 2011                [Page 1]

Internet-Draft        BGP Prefix Origin Validation         February 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 August 11, 2011                [Page 2]

Internet-Draft        BGP Prefix Origin Validation         February 2011


Table of Contents

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



































Mohapatra, et al.        Expires August 11, 2011                [Page 3]

Internet-Draft        BGP Prefix Origin Validation         February 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.ymbk-rpki-rtr-protocol] for such a mechanism).  This document



Mohapatra, et al.        Expires August 11, 2011                [Page 4]

Internet-Draft        BGP Prefix Origin Validation         February 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

   In loading the validated objects from the local cache to the BGP
   speaker, the BGP speaker will store this data in the form of a
   database that maintains the relationship between prefixes and the
   corresponding set of authorized origin ASes.  The primary key for
   this database is a prefix set represented as (IP prefix)/[min.
   length, max. length].  The value stored against each prefix set is
   the set of AS numbers that is assigned or sub-allocated the
   corresponding IP address block.  An AS can originate more than one
   prefix set.  Thus, multiple prefix sets in the database may contain
   the same origin AS(es).

   Whenever UPDATEs are received from peers, a BGP speaker is expected
   to perform a lookup in this database for each of the prefixes in the
   UPDATE message.  To aid with better description, we define terms
   "UPDATE prefix" and "UPDATE origin AS number" to denote the values
   derived from the received UPDATE message, and "database prefix set"
   and "database origin AS number set" to mean the values derived from
   the database lookup.  Note that in the presence of overlapping
   prefixes, the database lookup against the "UPDATE prefix" may yield
   multiple matches.

   The following are the different types of results expected from such a
   lookup operation:

   o  If the "UPDATE prefix" finds no matching or covering prefixes in
      the database (i.e. the "UPDATE prefix" is not a sub-block of any



Mohapatra, et al.        Expires August 11, 2011                [Page 5]

Internet-Draft        BGP Prefix Origin Validation         February 2011


      of the database prefixes), the lookup result is returned as "not
      found".  Due to incremental deployment model of the RPKI
      repository, it is expected that a complete registry of all IP
      address blocks and their AS associations is not available at a
      given point of time.

   o  If there are "database prefix sets" that cover the "UPDATE
      prefix", and one of them has the "UPDATE origin AS number" in the
      "database origin AS number sets", then the lookup result is
      returned as "valid".

   o  If there are "database prefix sets" which cover the "UPDATE
      prefix", but none of them has the "UPDATE origin AS number" in the
      "database origin AS number set", then the lookup result is
      returned as "invalid".

   Depending on the lookup result, we define a property for each route,
   called the "validity state".  It can assume the values "valid", "not
   found", or "invalid".

   Note that all the routes, regardless of their "validity state" will
   be stored in the local BGP speaker's Adj-RIB-In.

   Following is a sample pseudo code for prefix validation function:


   //Input are the variables derived from a BGP UPDATE message
   //that need to be validated.
   //
   //origin_as is the rightmost AS in the final AS_SEQUENCE of
   //the AS_PATH attribute in the UPDATE message.
   //
   //origin_as is NONE if the AS_PATH contains an AS_SET
   //path segment type.
   input = {bgp_prefix, masklen, origin_as};

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

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

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



Mohapatra, et al.        Expires August 11, 2011                [Page 6]

Internet-Draft        BGP Prefix Origin Validation         February 2011


       //Each entry stores multiple records sorted by the ROA
       //maxLength field. i.e. there can be multiple ROA records
       //with the same IPaddress and minLength fields, but different
       //maxLength field. Iterate through all records of the entry
       //to check if there is one range that matches the input.
       record = next_in_entry_record_list(entry);
       while (record != NULL) {
           if (input.masklen <= record->max_length) {
               if (input.origin_as == record->origin_as) {
                   result = BGP_PFXV_STATE_VALID;
                   return (result);
               }
           }
       }
   }

   //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);



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.


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.ymbk-rpki-rtr-protocol]).  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



Mohapatra, et al.        Expires August 11, 2011                [Page 7]

Internet-Draft        BGP Prefix Origin Validation         February 2011


   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
   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






Mohapatra, et al.        Expires August 11, 2011                [Page 8]

Internet-Draft        BGP Prefix Origin Validation         February 2011


      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.


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



Mohapatra, et al.        Expires August 11, 2011                [Page 9]

Internet-Draft        BGP Prefix Origin Validation         February 2011


   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-arch]
              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch-09 (work in
              progress), October 2009.

   [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-06 (work in progress),
              October 2009.

   [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.

10.2.  Informational References

   [I-D.ymbk-rpki-rtr-protocol]
              Bush, R. and R. Austein, "The RPKI/Router Protocol",
              draft-ymbk-rpki-rtr-protocol-05 (work in progress),
              February 2010.


Authors' Addresses

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

   Email: pmohapat@cisco.com





Mohapatra, et al.        Expires August 11, 2011               [Page 10]

Internet-Draft        BGP Prefix Origin Validation         February 2011


   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


   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 August 11, 2011               [Page 11]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/