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Trusted Domain SRv6
draft-raviolli-intarea-trusted-domain-srv6-00

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This is an older version of an Internet-Draft whose latest revision state is "Active".
Authors Andrew Alston , Tom Hill , Tony Przygienda
Last updated 2023-03-26
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draft-raviolli-intarea-trusted-domain-srv6-00
Network Working Group                                          A. Alston
Internet-Draft                           Liquid Intelligent Technologies
Intended status: Standards Track                                 T. Hill
Expires: 27 September 2023                               British Telecom
                                                           A. Przygienda
                                                                 Juniper
                                                           26 March 2023

                          Trusted Domain SRv6
             draft-raviolli-intarea-trusted-domain-srv6-00

Abstract

   SRv6 as designed has evoked interest from various parties, though its
   deployment is being limited by known security problems in its
   architecture.  This document specifies a standard to create a
   solution that closes some of the major security concerns, while
   retaining the basis of the SRv6 protocol.

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 27 September 2023.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Description . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Glossary  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  The SRv6 Security Problem . . . . . . . . . . . . . . . . . .   3
   4.  Characteristics of a Fail-Closed Protocol Domain  . . . . . .   3
   5.  SRv6 in the context of a trusted domain - an objective
           analysis  . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Trusted-Domain Implementation . . . . . . . . . . . . . . . .   5
     6.1.  Boundary routers  . . . . . . . . . . . . . . . . . . . .   5
     6.2.  Transit and egress routers  . . . . . . . . . . . . . . .   5
   7.  Registry Considerations . . . . . . . . . . . . . . . . . . .   5
     7.1.  IANA Considerations . . . . . . . . . . . . . . . . . . .   5
     7.2.  IEEE Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Informative References . . . . . . . . . . . . . . . . .   6
     10.2.  Normative References . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Description

   SRv6 as designed has evoked interest from various parties, though its
   deployment is being limited by known security problems in its
   architecture.  This document specifies a standard to create a
   solution that closes some of the major security concerns, while
   retaining the basis of the SRv6 protocol.

2.  Glossary

   Fail-Closed Domain:
      synonymous with a Trusted Domain.

   Trusted Domain (TD):
      A domain that prevents processing of a protocol without explicit
      configuration, defined in detail in Section 4.

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   Fail-Closed Protocol (FPC):
      A protocol that can be deployed by establishing a fail closed
      domain.

   TD-SRv6:
      SRv6 modified to become a FPC and with that allowing for easy
      deployment in a TD.

3.  The SRv6 Security Problem

   SRv6 relies in its architecture on the concept of limited domain
   which as a concept suffers from lack of security that is deployable
   in economical, scalable fashion easily.

   Limited domains without very careful deployment will invariably leak
   beyond the domain and allow untrusted traffic to enter the domain and
   terminate on any arbitrary node.

   As per RFC 8402 [RFC8402]RFC8402 Section 8, SRv6 that leaks beyond
   the border of a trusted domain creates a security violation.

   The proper solution is to create a trusted domain that has a default
   fail-closed approach and a well-defined trusted/untrusted boundary.

   Examples of fail closed protocols currently include:

   *  mpls

   *  clns

   *  lldp

   *  bier

4.  Characteristics of a Fail-Closed Protocol Domain

   A fail closed protocol domain is determined by following properties:

   Processing of the protocol packet on an interface requires explicit
   configuration with a default drop behavior.

   Leaking according protocol packets beyond the boundary of fail-closed
   domain requires explicit config.

   Fail closed protocols are easily identifiable by their top level
   (e.g. link layer) encoding early in the packet formats and often by
   fields at fixed offset.  In another words either their encoding or
   encapsulation allows to distinguish it easily from other traffic.

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   Classification of the protocol packets is completely deterministic.

   Confining the protocol to the trusted domaim does not require complex
   processing in either hardware or software to allow for scalability
   and economical deployment.

   The boundary of a trusted domain consists of a set of interfaces that
   exhibit default behavior.

5.  SRv6 in the context of a trusted domain - an objective analysis

   It is currently impossible to differentiate SRv6 and IPv6 at the
   link-layer or easily at network layer by e.g. a reserved protocol
   number as IPSec does.

   In the event of a packet being sent into a trusted domain, either
   accidentally or by a malicious actor, it is possible to send the
   frame to a node binding the specific SID, and have the packet
   processed, irrespective of the content of the underlying
   (encapsulated) packet.

   The current security proposals in RFC8402 section 8.2, security is
   based on the application of filters preventing ingress traffic at the
   boundary routers destined towards a SID within the domain.  Such
   filtering is prone to configuration errors and in addition, has
   significant impact on TCAM utilization on devices that have large
   numbers of ingress points into the domain.  The matching itself, due
   to the complexity and numerous possibilities of expressing a set of
   SIDs will likely necessitate a complete semantic parsing of such list
   to guarantee fully precise matching including wildcarding in
   different forms.

   In the context of a trusted domain, anything outside of the operators
   control should not be considered trusted.  This means applying
   filters to prevent leakage into the domain at every customer port,
   every server, and every cloud stack.  The scale and complexity of
   maintaining such a "shorewall" is daunting and at large scale will
   not be likely to keep up with the timing necessary in case of attacks
   mounted and metamorphosing in short time intervals.  An attack
   avoiding the filter wall may evade discovery for a long time in case
   of lack of sophisticated traffic analyis and analytics tools.

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6.  Trusted-Domain Implementation

   To implement SRv6 in the context of a trusted domain, it is necessary
   to modify it to allow deployment in a fail-closed boundary
   efficiently.  This requires changes to the protocol encapsulation at
   both the boundary routers and the transit nodes.  This document
   introduces a distinct ethertype to be used for td-srv6

6.1.  Boundary routers

   Trusted Domain boundary routers form the point at which the new
   ethertype is imposed.  Imposition of the ethertype happens on packet
   ingress, at the same point as SRv6 header imposition is performed.

   Boundary interfaces will, by default behavior, drop packets already
   containing the srv6-td ethertype.

6.2.  Transit and egress routers

   In the case of a transit or egress router, should a frame not be
   marked with the srv6-td ethertype, the frame will be treated as a
   standard IPv6 packet for the purposes of handling and forwarding.

   Only frames marked with the srv6-td ethertype will be processed as
   SRv6 packets.

   A router configured to process TD-SRv6 MUST drop packets containing
   an SRH if received on any ethertype except srv6-td.

7.  Registry Considerations

7.1.  IANA Considerations

   No IANA Considerations

7.2.  IEEE Considerations

   TD-SRv6 Ethertype: TBD0

8.  Security Considerations

   This draft enhances the security mechanisms required by section 8 of
   RFC8402, and does not impose any further security considerations of
   its own.

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9.  Contributors

   Weiqiang Cheng

   chengweiqiang@chinamobile.com

   Anthony Somerset

   anthony.somerset@liquid.tech

10.  References

10.1.  Informative References

10.2.  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>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

Authors' Addresses

   Andrew Alston
   Liquid Intelligent Technologies
   Email: andrew-ietf@liquid.tech

   Tom Hill
   British Telecom
   Email: tom@ninjabadger.net

   Tony Przygienda
   Juniper
   1137 Innovation Way
   Sunnyvale, CA
   United States of America
   Email: prz@juniper.net

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