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Versions: 00 01

idr                                                                J. Hu
Internet-Draft                                                     Nokia
Intended status: Standards Track                           March 4, 2019
Expires: September 5, 2019


                BGP Signaled IPsec Tunnel Configuration
                      draft-hujun-idr-bgp-ipsec-00

Abstract

   This document defines a method of using BGP to signal IPsec tunnel
   configuration along with NLRI, it uses and extends tunnel
   encapsulation attribute as specified in [I-D.ietf-idr-tunnel-encaps]
   for IPsec tunnel.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on September 5, 2019.

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

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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Tunnel Encapsulation Attribute for IPsec  . . . . . . . . . .   3
     2.1.  Local and Remote Prefix sub-TLV . . . . . . . . . . . . .   4
     2.2.  Public Routing Instance sub-TLV . . . . . . . . . . . . .   4
   3.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Semantics and Usage of IPsec Tunnel Encapsulation attribute .   8
     4.1.  Nested Tunnel . . . . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   IPsec is the standard for IP layer traffic protection, however in a
   big network where mesh connections are needed, configuring large
   number of IPsec tunnels is error prone and not scalable.  So instead
   of pre-provision IPsec tunnels on each router, this document defines
   a method to allow router to advertise the IPsec tunnel configurations
   it requires to reach a given NLRI via BGP.  This document does not
   intend to be one solution for all cases, the main use case is to
   simplify IPsec tunnel provision in networks under single
   administrative domain; it uses standard based components (IPsec/
   IKEv2[RFC7296] and BGP) with limited changes.  There is no change to
   IPsec/IKEv2, and only limited changes to BGP.

   IPsec tunnel configurations typically include following parts:

   o  tunnel endpoint address (local and remote)

   o  public routing instance, routing instance where IPsec packet is
      forwarded in

   o  private routing instance, routing instance where payload packet is
      forwarded in

   o  tunnel authentication method and credentials

   o  IKE SA and CHILD SA transform (a.k.a crypto algorithms)

   o  CHILD SA traffic selector

   o  other: like lifetime, DPD timer, use of PFS ..etc



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   In order to minimize amount configurations signal via BGP, only
   following configurations are explicit advertised:

   o  local tunnel endpoint address: BGP tunnel encapsulation attribute

   o  public routing instance: sub-TLV in tunnel encapsulation attribute

   o  CHILD SA traffic selector: NLRI and/or sub-TLV in tunnel
      encapsulation attribute

   Other configurations are either derived or via color mapping:

   o  remote tunnel endpoint address: dynamic learned when received
      IKEv2 IKE_SA_INIT request

   o  private routing instance: via route-target in same BGP UPDATE

   o  tunnel authentication and credentials: out of scope, could be PKI
      based authentication

   o  IKE SA and CHILD SA transform, lifetime, DPD timer, PFS ..etc: all
      these configurations are implicitly signaled via color sub-TLV in
      tunnel encapsulation attribute

   [I-D.ietf-idr-tunnel-encaps] defines a generic tunnel encapsulation
   attribute for BGP, however it needs to be extended to support IPsec
   tunnel.

1.1.  Terminology

   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.  Tunnel Encapsulation Attribute for IPsec

   This document extends tunnel encapsulation attribute specified in
   [I-D.ietf-idr-tunnel-encaps] by introducing following changes:

   o  A tunnel type for IPsec tunnel: ESP tunnel mode (AH tunnel mode is
      not included in this document).  Existing type 4 (IPsec in Tunnel-
      mode) in IANA "BGP Tunnel Encapsulation Attribute Tunnel Types"
      registry could be reused

   o  A new sub-TLV for public routing instance




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   o  A new sub-TLV for remote address prefix

   o  A new sub-TLV for local address prefix

   Following existing sub-TLVs apply to IPsec tunnel encapsulation
   attribute:

   o  Remote Endpoint: IPsec tunnel endpoint address

   o  Color: IPsec configuration attributes like ESP transform; the
      meaning of this sub-TLV is local to the administrative domain

   o  Embedded Label Handling: see Section 4 for detail

2.1.  Local and Remote Prefix sub-TLV

   Local prefix sub-TLV is an optional sub-TLV used to specify a list of
   address prefix that used as local traffic selector address ranges; if
   local prefix sub-TLV is not included, then prefixes in NLRI will be
   used; Remote prefix sub-TLV is a mandatory sub-TLV used to specify a
   list of address prefix that used as remote traffic selector address
   ranges; The IP version of local/remote prefix MUST be as same as IP
   version of prefix in NLRI.  A single all zero prefix means any prefix
   is allowed.  Local and remote prefix sub-TLV has same encoding as
   following:

                  +---------------------------------------+
                  |  list of prefixes (variable)          |
                  +---------------------------------------+

                      Figure 1: Source Prefix sub-TLV

   Each prefix is encoded as following:

                          +---------------------------+
                          |   prefix Length (1 octet) |
                          +---------------------------+
                          |   Prefix (4 or 16 octets) |
                          +---------------------------+

                             Figure 2: prefix

2.2.  Public Routing Instance sub-TLV

   Public routing instance sub-TLV is an optional sub-TLV used to
   specify the routing instance to which the remote point address
   belongs, if tunnel encapsulation attribute doesn't include this TLV,
   then the routing instance is the same to which BGP session belongs.



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   the value field of the sub-TLV consist a route target community as
   defined in [RFC4360].

3.  Operation

   Following are the rules of operation:

   1.  All routers are in same administrative domain

   2.  All routers are pre-provisioned with following:

       *  Authentication credential like PKI certificates and key

       *  Mapping between color and IPsec configurations

   3.  If a given NLRI need IPsec protection, then advertising router
       need to include an IPsec tunnel encapsulation attribute, along
       with the NLRI in BGP UPDATE U;

   4.  When a router need to forward a packet along a path is determined
       by a BGP UPDATE which has a tunnel encapsulation attribute that
       contains one or more IPsec TLV, and router decides use IPsec
       based on local policy, then the router need to check if there is
       an existing CHILD SA could be used, a CHILD SA could be used when
       it meets all following conditions:

       *  its private routing instance is same as routing instance to
          which the packet to be forwarded belongs

       *  its public routing instance is same as indicated by the Public
          Routing Instance sub-TLV; if the sub-TLV doesn't exist, then
          it is same as routing instance to which BGP session belongs


       *  its peer tunnel address is same as indicated by Remote
          Endpoint sub-TLV

       *  the source and destination address of the packet to be
          forwarded falls in the range of CHILD SA's traffic selector

       *  its transform and other configuration maps to the color
          indicated in the Color sub-TLV

   5.  If router can't find such CHILD SA, then it will use IKEv2 to
       create one; if there are multiple IPsec TLVs in U, then it need
       to select one from feasible TLVs, a IPsec TLV is considered as
       feasible when it meets all following requirements:




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       *  the source address of the packet must fall in one of Remote
          Prefixes

       *  the destination address of the packet must fall one of Source
          Prefixes

       *  the Remote Endpoint, along with Public Routing Instance sub-
          TLV identifies an IP address that is reachable

   6.  After an IPsec TLV is selected, router uses IKEv2 to create the
       CHILD_SA:

       *  public/private routing instance, peer's tunnel address are
          chosen based on above rules

       *  Traffic Selector:

       *  For each TS in TSi:

          +  address range: the prefix specified in Remote Prefix sub-
             TLV

          +  protocol: any

          +  port range: any

       *  for each TS in TSr:

          +  address range: prefixes specified by Local Prefix sub-TLV
             if it exists; otherwise use the prefix specified by the
             NLRI


          +  protocol: any

          +  port range: any

   The operation of BGP signaling IPsec configuration is illustrated
   with following example:












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                           +--------+
                  +--------+ BGP RR +---------+
                  |        +--------+         |
                  |                           |
                  |     CHILDSA1: Red         |
               +--+---+ <----------------> +--+---+
 subetA -------+  R1  |      IKEv2         |  R2  +----- subnetB/subnetC
               +------+ <----------------> +------+
                         CHILDSA2: Yellow

                        Figure 3: Operation Example

   There are following traffic protection requirements:

   o  subnetA - subnetB: ESP tunnel, AES-CBC-256 with SHA-384, mapping
      to color red

   o  subnetA - subnetC: ESP tunnel, null encryption with only integrity
      protection, SHA-256, mapping to color yellow

   Both R1 and R2 are provisioned with PKI key and certificate from same
   CA.

   o  R1 advertise subnetA in BGP UPDATE, which has a tunnel
      encapsulation attribute that contains two IPsec tunnel TLVs:

      *  TLV-1: endpoint R1TunnelAddr, color sub-TLV red and subnetB in
         Remote Prefix sub-TLV.

      *  TLV-2: endpoint R1TunnelAddr, color sub-TLV yellow and subnetC
         in Remote Prefix sub-TLV.

   o  R2 advertise subnetB in BGP UPDATE, which has a tunnel
      encapsulation attribute that contains one IPsec tunnel TLV:
      R2TunnelAddr, color sub-TLV red and subnetA in Remote Prefix sub-
      TLV.

   o  R2 advertise subnetC in BGP UPDATE, which has a tunnel
      encapsulation attribute that contains one IPsec tunnel TLV:
      R2TunnelAddr, color sub-TLV yellow and subnetA in Remote Prefix
      sub-TLV.

   o  R1 received a packet from subnetA destined to subnetB, since BGP
      UPDATE contain subnetB also contains an IPsec tunnel encapsulation
      attribute, there is no existing CHILD SA could be used, based on
      the rules described in this section, R1 select TLV-1 and uses
      IKEv2 to establish an IPsec tunnel to R2TunnelAddr, using
      certificate authentication, create 1st CHILD SA CHILDSA1:



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      *  ESP transform: AES-CBC-256 and SHA-384

      *  Traffic Selector:

         +  TSi: address subnetA, protocol any, port any

         +  TSr: address subnetB, protocol any, port any

   o  after tunnel is created, R1 and R2 could forward traffic between
      subnetA and subnetB over CHILDSA1

   o  R1 received a packet from subnetA destined to subnetC, CHILDSA1
      can't be used for this packet, R1 select TLV-2 to create 2nd CHILD
      SA, and given there is already an IKE SA between R1 and R2, R1
      uses existing IKESA to create CHILDSA2:

      *  ESP transform: Null encryption with SHA-256

      *  Traffic Selector:

         +  TSi: address subnetA, protocol any, port any

         +  TSr: address subnetC, protocol any, port any

   o  R1 and R2 could forward traffic between subnetA and subnetC over
      CHILDSA2

4.  Semantics and Usage of IPsec Tunnel Encapsulation attribute

   IPsec tunnel encapsulation TLV has same usage and semantics as
   defined in [I-D.ietf-idr-tunnel-encaps] with following differences:

   o  Due to nature of IPsec, the payload packet could only be IPv4 or
      IPv6 packet, so it MAY be carried in any BGP UPDATE message whose
      AFI/SAFI is 1/1 (IPv4 Unicast), 2/1 (IPv6 Unicast).

   o  For 1/128 (VPN-IPv4 Labeled Unicast), 2/128 (VPN-IPv6 Labeled
      Unicast), these NLRI has embedded label, which cause the payload
      packet can't be encapsulated in ESP packet, however with IPsec
      tunnel encapsulation, the label could be ignored during
      encapsulation since CHILD SA itself could be used to identify the
      private routing instance; so an UPDATE that include IPsec tunnel
      encapsulation attribute, which contains value 2 of Embedded Label
      Handling Sub-TLV, could be used to signal this type of setup.

   o  For other types of AFI/SAFI, a nested tunnel setup could be used
      to get IPsec protection, for example, an 25/70 (EVPN) payload




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      packet could be encapsulated in VXLAN over IPsec tunnel.  See
      Section 4.1 for further detail.

4.1.  Nested Tunnel

   A nested tunnel could be used for payload packet type that can't be
   encapsulated in IPsec tunnel directly, e.g. an Ethernet packet of
   EVPN service.  Following is an example of using VXLAN over IPsec
   tunnel for EVPN service:

   o  R1 need to forward an Ethernet packet P

   o  the path along which P is to be forwarded is determined by BGP
      UPDATE U1, which has a VXLAN tunnel encapsulation attribute and
      the next-hop is router R2

   o  the best path to R2 is a BGP route that was advertised in BGP
      UPDATE U2, which has an IPsec tunnel encapsulation TLV.

   o  R1 will encapsulate P in a VXLAN tunnel as indicated in U1, then
      encapsulate VXLAN packet into IPsec tunnel as indicated in U2

   o  if color sub-TLV is used, then both U1 and U2 MUST have matching
      color sub-TLV, otherwise the VXLAN packet will not be sent through
      IPsec tunnels identified in U2


5.  IANA Considerations

   This document reuses "IPsec in Tunnel-mode"(4) as BGP Tunnel
   Encapsulation Attribute Tunnel Types.

   This document will request new values in IANA "BGP Tunnel
   Encapsulation Attribute Sub-TLVs" registry for following sub-TLV:

   o  public routing instance

   o  remote address prefix

   o  local address prefix

6.  Security Considerations

   IKEv2 is used to create IPsec tunnel, which ensures following:

   o  Traffic protection keys are generated dynamically during IKEv2
      negotiation, only known by participating peer of the IPsec tunnel;
      there is no central node to manage and distribute all keys.



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   o  IKEv2 rekey mechanism refresh keys regularly; PFS(Perfect Forward
      Secrecy) provides additional protection;

   o  Secure authentication mechanism that only allow authenticated peer
      to create tunnel

   o  Traffic Selector guarantee that only agreed traffic is allowed to
      be forwarded within the IPsec tunnel;

   o  Using a separate, dedicate protocol(IKEv2) for key management/
      authentication ensure they are not tied to BGP, all existing and
      future IKEv2 features could be used without changing BGP;

   There is concern that malicious party might manipulate IPsec tunnel
   encapsulation attribute to divert traffic, however this risk could be
   mitigated by IKEv2 mutual authentication.

   BGP Origin Validation [RFC6811] and BGPSec [RFC8205] could be used to
   further secure BGP UPDATE message.

7.  References

7.1.  Normative References

   [I-D.ietf-idr-tunnel-encaps]
              Rosen, E., Patel, K., and G. Velde, "The BGP Tunnel
              Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-11
              (work in progress), February 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>.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
              February 2006, <https://www.rfc-editor.org/info/rfc4360>.

   [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>.

7.2.  Informative References

   [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>.



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   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <https://www.rfc-editor.org/info/rfc7296>.

   [RFC8205]  Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
              Specification", RFC 8205, DOI 10.17487/RFC8205, September
              2017, <https://www.rfc-editor.org/info/rfc8205>.

Author's Address

   Hu Jun
   Nokia
   777 East Middlefield Road
   Mountain View  CA 95148
   United States

   Email: jun.hu@nokia.com

































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