Updated BGP Operations and Security
draft-ietf-grow-bgpopsecupd-04

Global Routing Operations                                      T. Fiebig
Internet-Draft                                                   MPI-INF
Obsoletes: 7454 (if approved)                                N. Hilliard
Intended status: Best Current Practice                              INEX
Expires: 3 April 2025                                  30 September 2024

                  Updated BGP Operations and Security
                     draft-ietf-grow-bgpopsecupd-04

Abstract

   The Border Gateway Protocol (BGP) is a critical component in the
   Internet to exchange routing information between network domains.
   Due to this central nature, it is important to understand the
   security and reliability requirements that can and should be ensured
   to prevent accidental or intentional routing disturbances.

   Previously, security considerations for BGP have been described in
   RFC7454 / BCP194.  Since the publications of RFC7454 / BCP194,
   several developments and changes in operational practice took place
   that warrant an update of these best current practices.  This
   document replaces RFC7454 / BCP194, focusing on the overall goals,
   and providing a less implementation centric set of best practices.

   To this end, the document describes the security requirements and
   goals when operating BGP for exchanging routing information with
   other networks.  The document explicitly does not focus on specific
   technical implementations and requirements.  Operators are advised to
   consult documentation and contemporary informational documents
   concerning methods to ensure that these properties are sufficiently
   ensured in their network.

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
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

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   This Internet-Draft will expire on 3 April 2025.

Copyright Notice

   Copyright (c) 2024 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
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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Scope of the Document . . . . . . . . . . . . . . . . . . . .   3
   3.  Protection of the BGP Speaker and Session . . . . . . . . . .   3
     3.1.  BGP Session Protection  . . . . . . . . . . . . . . . . .   3
     3.2.  BGP Speaker Management Interface Protection . . . . . . .   4
   4.  NLRI Filtering  . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Importing NLRI  . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Originating and Redistributing NLRI . . . . . . . . . . .   5
     4.3.  Altering NLRI . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The Border Gateway Protocol (BGP), specified in [RFC4271], is the
   protocol used in the Internet to exchange routing information between
   network domains.  BGP does not directly include mechanisms that
   control whether the routes exchanged conform to the various
   guidelines defined by the Internet community.  Furthermore, the BGP
   protocol itself, by its design, does not have any direct way to
   protect itself against threats to confidentiality, integrity, and
   availability.  This document summarizes security properties and
   requirements when operating BGP for securing the infrastructure as
   well as for security considerations regarding the exchanged routing

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   information.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Scope of the Document

   The guidelines defined in this document are intended for BGP when
   used to exchange generic Internet routing information within the DFZ.
   It specifically does not cover other uses of BGP, e.g., when using
   BGP for NLRI exchange in a data-center context.  This document does
   not specify how the outlined requirements and properties can be
   technically realized at a specific point in time.  Instead, operators
   are advised to consult applicable documentation and contemporary
   informational documents describing implementation specifics.

3.  Protection of the BGP Speaker and Session

   The BGP speaker, i.e., the host running BGP to exchange routing
   information, needs to be protected from external attempts to taint
   integrity or availability of the BGP session and host alike.

3.1.  BGP Session Protection

   To protect a BGP speaker on the network layer, an operator MUST
   ensure the following properties using technical or organizational
   measures:

   *  Prevent off-path attackers from injecting BGP messages into
      existing sessions.

   *  Prevent off-path attackers from interrupting existing sessions.

   *  Prevent off-path attackers from preventing the establishment of
      new sessions.

   *  Prevent remote systems from overwhelming the BGP speaker by
      sending large volumes of unsolicited packets or BGP messages.

   *  Ensure that unstable sessions do not threaten the availability of
      BGP speakers within the network.

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3.2.  BGP Speaker Management Interface Protection

   In addition to the control plane / exchange of BGP protocol messages,
   the management plane of BGP speakers must be appropriately secured.
   Hence, operators MUST ensure that:

   *  No unauthorized third-parties can obtain access or connect to the
      management interface of a BGP speaker in a way that allows
      tainting confidentiality, integrity, or availability.

   *  External activity towards the management interface do not
      interfere with the integrity or availability of BGP sessions.

4.  NLRI Filtering

   The purpose of BGP is exchanging routing information, i.e., NLRI.
   Importing or exporting incorrect or malicious NLRI is a security risk
   for networks themselves, but may also form a threat for connected
   and/or remote networks.  As such, operators MUST ensure the following
   properties when importing or exporting routing information from their
   neighbors.

4.1.  Importing NLRI

   When importing NLRI from a neighbor, an operator MUST ensure that all
   imported NLRI conform to the following properties by implementing
   technical or organizational measures:

   *  The AS originating NLRI for a prefix MUST be globally authorized
      to originate that prefix.  Operators MAY deviate from this for
      default routes (::/0 and 0.0.0.0/0), if they granted the specific
      neighbor permission to announce default routes towards them.

   *  All ASes left of the originating AS in the AS_PATH MUST be
      authorized to advertise the NLRI to the AS directly to their left,
      and the neighbor from which an NLRI is received MUST be authorized
      to advertise it to the importing AS.

   *  The AS_PATH MUST NOT contain AS numbers reserved for private
      [RFC6996] or special-use cases, except for those AS numbers
      explicitly dedicated to a special-use that requires their presence
      in the global routing table [IANAASNSpec].

   *  The number of NLRI received from a neighbor MUST NOT exceed the
      resources of the local router.

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4.2.  Originating and Redistributing NLRI

   When originating NLRI or redistributing NLRI received from a
   neighbor, an operator MUST ensure that all NLRI they export conform
   to the following properties by implementing technical or
   organizational measures:

   *  The redistributing AS MUST be authorized to redistribute NLRI for
      the specific prefix when received from the AS directly to its
      right in the AS_PATH.  Additionally, each AS in the AS_PATH not
      originating the prefix MUST be authorized to redistribute the
      prefix when receiving it from the next AS to its right.

   *  The AS originating NLRI for a prefix MUST be globally authorized
      to originate that prefix.  Operators MAY deviate from this for
      default routes (::/0 and 0.0.0.0/0), if they originate the default
      route and the specific neighbor granted them permission to
      announce default routes towards them.

   *  The AS_PATH MUST NOT contain AS numbers reserved for private
      [RFC6996] or special-use cases, except for those AS numbers
      explicitly dedicated to a special-use that requires their presence
      in the global routing table [IANAASNSpec].

4.3.  Altering NLRI

   When processing NLRI, an operator MUST ensure that basic properties
   of these NLRI are not altered:

   *  An operator MUST NOT change or remove transitive BGP attributes,
      if the attribute is unknown to the operator.  In selected cases,
      if a specific attribute is known to be malicious, an operator MAY
      temporarily remove that specific attribute from NLRI when
      importing them or filter NLRI carrying the attribute.

   *  NLRI carried on BGP MUST NOT be enriched with transitive
      attributes subject to change independent of the underlying NLRI,
      e.g., encoding RPKI validation state in transitive attributes
      [I-D.draft-ietf-sidrops-avoid-rpki-state-in-bgp].

5.  IANA Considerations

   This document does not require any IANA actions.

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6.  Security Considerations

   This document is entirely about BGP operational security.  It lists
   requirements and properties operators MUST ensure using technical or
   organizational measures when operating BGP routers in the DFZ.

   However, it does not detail how the outlined properties and security
   requirements can be implemented and enforced in practice.  This is a
   conscious choice given that available techniques and methods to
   ensure these properties will change over time, while the underlying
   principles remain the same.

   Instead, readers MAY refer to the most recent non expired draft of
   [I-D.draft-fiebig-grow-routing-ops-sec-inform] for an updated list of
   currently available technology to ensure the above principles, and
   the most recent non expired draft of
   [I-D.draft-fiebig-grow-routing-ops-terms] for information on
   currently used terms and definitions in the context of global routing
   operations.  Readers MUST NOT rely on expired versions of these I-Ds.
   If no most recent non-expired version of either I-D is available, the
   document MUST be considered to be non-existent.

7.  References

7.1.  Normative References

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.

   [RFC6996]  Mitchell, J., "Autonomous System (AS) Reservation for
              Private Use", BCP 6, RFC 6996, DOI 10.17487/RFC6996, July
              2013, <https://www.rfc-editor.org/info/rfc6996>.

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   [I-D.draft-fiebig-grow-routing-ops-sec-inform]
              Fiebig, T., "Current Options for Securing Global Routing",
              Work in Progress, Internet-Draft, draft-fiebig-grow-
              routing-ops-sec-inform, 3 July 2024,
              <https://datatracker.ietf.org/doc/draft-fiebig-grow-
              routing-ops-sec-inform/>.

   [I-D.draft-fiebig-grow-routing-ops-terms]
              Fiebig, T., "Currently Used Terminology in Global Routing
              Operations", Work in Progress, Internet-Draft, draft-
              fiebig-grow-routing-ops-terms, 3 July 2024,
              <https://datatracker.ietf.org/doc/draft-fiebig-grow-
              routing-ops-terms/>.

   [I-D.draft-ietf-sidrops-avoid-rpki-state-in-bgp]
              Snijders, J., Fiebig, T., and M. A. Stucchi, "Guidance to
              Avoid Carrying RPKI Validation States in Transitive BGP
              Path Attributes", Work in Progress, Internet-Draft, draft-
              draft-ietf-sidrops-avoid-rpki-state-in-bgp-00, 9 April
              2024, <https://datatracker.ietf.org/doc/draft-draft-ietf-
              sidrops-avoid-rpki-state-in-bgp/>.

   [IANAASNSpec]
              IANA, "Special-Purpose Autonomous System (AS) Numbers",
              <https://www.iana.org/assignments/iana-as-numbers-special-
              registry/iana-as-numbers-special-registry.xhtml>.

7.2.  Informative References

   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
              and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
              February 2015, <https://www.rfc-editor.org/info/rfc7454>.

Acknowledgements

   This document has been originally based on [RFC7454] and we thank the
   original authors for their work.

   We thank the following people for reviewing this draft and suggesting
   changes:

   *  Gert Doerring

   *  Jeff Haas

   *  Geng Nan

   *  Martin Pels

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   *  Job Snijders

   *  Berislav Todorovic

   *  Martin Pels

   *  Wolfgang Tremmel

   *  Ben Maddison

Authors' Addresses

   Tobias Fiebig
   Max-Planck-Institut fuer Informatik
   Campus E14
   66123 Saarbruecken
   Germany
   Phone: +49 681 9325 3527
   Email: tfiebig@mpi-inf.mpg.de

   Nick Hilliard
   Internet Neutral Exchange Association
   4027 Kingswood Road
   Citywest, Dublin
   D24 AX96
   Ireland
   Phone: +353 1 433 205 2
   Email: nick@inex.ie

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