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Network Working Group                                            H. Chen
Internet-Draft                                             China Telecom
Intended status: Best Current Practice                             D. Ma
Expires: May 7, 2020                                                ZDNS
                                                                   Y. Gu
                                                               S. Zhuang
                                                                 H. Wang
                                                                  Huawei
                                                        November 4, 2019


                   Enhanced AS Loop Detection for BGP
             draft-chen-grow-enhanced-as-loop-detection-03

Abstract

   Misconfiguration and malicious manipulation of BGP AS_Path may lead
   to route hijack.  This document proposes to enhance the BGP Inbound/
   Outbound route processing in the case of detecting an AS loop.  Two
   options are proposed for the enhancement, a) a local check at the
   device; b) data collection/analysis at the remote network controller/
   server.  Both approaches are beneficial for route hijack detection.

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].

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 https://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 7, 2020.






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Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Forged AS_PATH Examples . . . . . . . . . . . . . . . . . . .   3
     3.1.  AS Loop Detected at Inbound Processing  . . . . . . . . .   3
     3.2.  AS Loop Detected at Outbound Processing . . . . . . . . .   4
   4.  Enhancement to BGP Inbound/Outbound Processing  . . . . . . .   5
     4.1.  Enhancement for AS Loop Detected at Inbound Process . . .   5
     4.2.  Enhancement for AS Loop Detected at Outbound Process  . .   5
   5.  BMP extension for AS Loop Detection . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The Border Gateway Protocol (BGP) [RFC4271], as an inter-Autonomous
   (AS) routing protocol, is used to exchange network reachability
   information between BGP systems.  As a distance-vector based
   protocol, special mechanism is designed for BGP to avoid routing
   loop.  As stated in Section 9.1.2. of RFC4271:

      ...

      If the AS_PATH attribute of a BGP route contains an AS loop, the
      BGP route should be excluded from the Phase 2 decision function.
      AS loop detection is done by scanning the full AS path (as
      specified in the AS_PATH attribute), and checking that the
      autonomous system number of the local system does not appear in
      the AS path.  Operations of a BGP speaker that is configured to



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      accept routes with its own autonomous system number in the AS path
      are outside the scope of this document.

      ...

   Conventionally, upon receiving an BGP Update route with as loop
   detection, the route is simply discarded.  In the case of forged-AS-
   type BGP hijacks, which can be generated by configuration errors or
   malicious attacks, the simple discard action can lead to large-scale
   network connectivity issues.

   This document proposes enhancements to BGP inbound and outbound
   processing when detecting AS loop in order to identify possible BGP
   hijacks.

2.  Terminology

   The following terminology is used in this document.

   AS: Autonomous System

   BGP: Border Gateway Protocol

   ROA: Route Origin Authorization

   ASPA: Autonomous System Provider Authorization

   ISP: Internet Service Provider

   BMP: BGP Monitoring Protocol

3.  Forged AS_PATH Examples

3.1.  AS Loop Detected at Inbound Processing

   o  Forged Case 1: AS shown in Figure 1, an upstream AS of AS64596
      forged a route with the ASN 64596 as the origin ASN in the AS-
      Path.

   o  Forged Case 2: AS shown in Figure 1, an upstream AS of AS64596
      forged a route with the ASN 64596 as the transit ASN in the AS-
      Path.









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            AS Loop Detection enhancement point
                             |
                             |                     x.y.z.0/24
                             |                Origin AS 64600
                             v               <----------------
   AS64595---AS64596---AS64597---AS64598---AS64599----AS64600
                       Normal Case:
                       x.y.z.0/24, AS-Path: 64598 64599 64600

                       Forged Case 1:
                       x.y.z.0/24, AS-Path: 64598 64597

                       Forged Case 2:
                       x.y.z.0/24, AS-Path: 64598 64597 64600

              Figure 1: BGP Inbound Route Processing

3.2.  AS Loop Detected at Outbound Processing

   o  Forged Case 3: AS shown in Figure 2, an upstream AS of AS64597
      forged a route with the ASN 64596 as the origin ASN in the AS-
      Path.

   o  Forged Case 4: AS shown in Figure 2, an upstream AS of AS64597
      forged a route with the ASN 64596 as the transit ASN in the AS-
      Path.

         AS Loop Detection enhancement point
                       |
                       |                         x.y.z.0/24
                       |                     Origin AS 64600
                       v                   <----------------
   AS64595---AS64596---AS64597---AS64598---AS64599----AS64600
                       Normal Case:
                       <-- x.y.z.0/24, AS-Path: 64597 64598 64599 64600

                       Forged Case 3:
                       <-- x.y.z.0/24, AS-Path: 64597 64598 64596

                       Forged Case 4:
                       <-- x.y.z.0/24, AS-Path: 64597 64596 64600

                Figure 2: BGP Outbound Route Processing








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4.  Enhancement to BGP Inbound/Outbound Processing

4.1.  Enhancement for AS Loop Detected at Inbound Process

   Currently, ROV [RFC6811] and ASPA verification
   [I-D.ietf-sidrops-aspa-verification]can be adopted for BGP leak/
   hijack detection.  However, for the forged case 1&2, the conventional
   BGP inbound process would simply discard the routes with AS loop
   before any further leak/hajack detection.

   This document suggests further analysis of such routes.  The analysis
   may include mechanisms that apply to normal routes for hijack
   detection, such as ROV, ASPA and so on.  The detailed analyzing
   mechanisms as well as the corresponding actions w.r.t. the analysis
   are outside the scope of this document.

   Two options of where the analysis of the inbound processing
   enhancement takes place is proposed.

   o  Option 1: Analyze the routes with AS loop based on local database.

   o  Option 2: Collect the routes with AS loop with BMP and analyze
      them at the remote controller/server.

4.2.  Enhancement for AS Loop Detected at Outbound Process

   Currently, the egress ROV can be adopted for BGP hijack detection.
   However, for forged case 3&4, when eBGP Split-Horizon is enabled, the
   routes with AS loop could possibly be discarded before any hijack
   detection.

   This document suggests further analysis of such routes.  The analysis
   may include mechanisms that apply to normal routes for hijack
   detection, such as egress ROV, ASPA and so on.  The detailed
   analyzing mechanisms as well as the corresponding actions w.r.t. the
   analysis are outside the scope of this document.

   Two options of where the analysis of the outbound processing
   enhancement takes place is proposed.

   o  Option 1: Analyze the routes with AS loop based on local database.

   o  Option 2: Collect the routes with AS loop with BMP and analyze
      them at the remote controller/server.







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5.  BMP extension for AS Loop Detection

   This document extends the BMP Route Mirroring message to mirror
   routes with AS loop to the BMP Server.

   Per RFC7854, Route Mirroring messages can be used to mirror the
   messages that have been treated-as-withdraw [RFC7606], for debugging
   purposes.  This document defines a new code type for Type 1
   Information TLV:

   o  Code = TBD: AS Loop Detected.  An AS loop is detected for the BGP
      route.  A BGP Message TLV MUST also occur in the TLV list.

6.  Acknowledgements

   The authors would like to acknowledge the review and inputs from Gang
   Yan, Zhenbin Li, Aijun Wang, Jeff Haas, Robert Raszuk, Chris Morrow,
   Alexander Asimov, Ruediger Volk, Jescia Chen and the working group.

7.  IANA Considerations

   This document defines one type for information carried in the Route
   Mirroring Information (Section 4.7 of RFC7854) code:

   o  Code = TBD: AS Path Looped.

8.  Security Considerations

   This document does not change the underlying security issues in the
   BGP protocol.  It however, does provide an additional mechanism to
   protect against attacks based on the forged AS-Path in the BGP
   routes.

9.  Normative References

   [I-D.ietf-sidrops-aspa-verification]
              Azimov, A., Bogomazov, E., Patel, K., and J. Snijders,
              "Verification of AS_PATH Using the Resource Certificate
              Public Key Infrastructure and Autonomous System Provider
              Authorization", draft-ietf-sidrops-aspa-verification-01
              (work in progress), July 2019.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.





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   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

   [RFC6811]  Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation", RFC 6811,
              DOI 10.17487/RFC6811, January 2013,
              <https://www.rfc-editor.org/info/rfc6811>.

   [RFC7854]  Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
              Monitoring Protocol (BMP)", RFC 7854,
              DOI 10.17487/RFC7854, June 2016,
              <https://www.rfc-editor.org/info/rfc7854>.

Authors' Addresses

   Huanan Chen
   China Telecom
   109, West Zhongshan Road, Tianhe District
   Guangzhou  510000
   China

   Email: chenhn8.gd@chinatelecom.cn


   Di Ma
   ZDNS
   4 South 4th St. Zhongguancun
   Beijing, Haidian
   China

   Email: madi@zdns.cn


   Yunan Gu
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: guyunan@huawei.com




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   Shunwan Zhuang
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: zhuangshunwan@huawei.com


   Haibo Wang
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: rainsword.wang@huawei.com



































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