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Network Working Group L. BergerRequest for Comments: 5566 LabNCategory: Standards Track R. White E. Rosen Cisco Systems June 2009BGP IPsec Tunnel Encapsulation AttributeStatus of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject toBCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document.Abstract The BGP Encapsulation Subsequent Address Family Identifier (SAFI) provides a method for the dynamic exchange of encapsulation information and for the indication of encapsulation protocol types to be used for different next hops. Currently, support for Generic Routing Encapsulation (GRE), Layer 2 Tunneling Protocol (L2TPv3), and IP in IP tunnel types are defined. This document defines support for IPsec tunnel types.Berger, et al. Standards Track [Page 1]

RFC 5566             BGP IPsec Tunnel Encapsulation            June 2009Table of Contents1. Introduction ....................................................21.1. Conventions Used in This Document ..........................22. Tunnel Encapsulation Types ......................................33. Use of IPsec Tunnel Types .......................................34. IPsec Tunnel Authenticator sub-TLV ..............................44.1. Use of the IPsec Tunnel Authenticator sub-TLV ..............55. Security Considerations .........................................56. IANA Considerations .............................................67. References ......................................................77.1. Normative References .......................................77.2. Informative References .....................................78. Acknowledgments .................................................81.  Introduction   The BGP [RFC4271] Encapsulation Subsequent Address Family Identifier   (SAFI) allows for the communication of tunnel information and for the   association of this information to a BGP next hop.  The Encapsulation   SAFI can be used to support the mapping of prefixes to next hops and   tunnels of the same address family, IPv6 prefixes to IPv4 next hops   and tunnels using [RFC4798], and IPv4 prefixes to IPv6 next hops and   tunnels using [RFC5549].  The Encapsulation SAFI can also be used to   support the mapping of VPN prefixes to tunnels when VPN prefixes are   advertised per [RFC4364] or [RFC4659].  [RFC5565] provides useful   context for the use of the Encapsulation SAFI.   The Encapsulation SAFI is defined in [RFC5512].  [RFC5512] also   defines support for the GRE [RFC2784], L2TPv3 [RFC3931], and IP in IP   [RFC2003] tunnel types.  This document builds on [RFC5512] and   defines support for IPsec tunnels.  Support is defined for IP   Authentication Header (AH) in tunnel mode [RFC4302] and for IP   Encapsulating Security Payload (ESP) in tunnel mode [RFC4303].  The   IPsec architecture is defined in [RFC4301].  Support for IP in IP   [RFC2003] and MPLS-in-IP [RFC4023] protected by IPsec Transport Mode   is also defined.   The Encapsulation Network Layer Reachability Information (NLRI)   Format is not modified by this document.1.1.  Conventions Used in This Document   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 [RFC2119].Berger, et al.              Standards Track                     [Page 2]

RFC 5566 BGP IPsec Tunnel Encapsulation June 20092. Tunnel Encapsulation Types Per [RFC5512], tunnel type is indicated in the Tunnel Encapsulation attribute. This document defines the following tunnel type values: - Transmit tunnel endpoint: Tunnel Type = 3 - IPsec in Tunnel-mode: Tunnel Type = 4 [RFC4302], [RFC4303] - IP in IP Tunnel with IPsec Transport Mode: Tunnel Type = 5 [RFC2003], [RFC4303] - MPLS-in-IP Tunnel with IPsec Transport Mode: Tunnel Type = 6 [RFC4023] Note, seeSection 4.3 of [RFC5512] for a discussion on the advertisement and use of multiple tunnel types. Note, the specification in [RFC4023] for MPLS-in-IP tunnels with IPsec Transport mode applies as well to IP in IP tunnels. This document does not specify the use of the sub-TLV types defined in [RFC5512] with these tunnel types. See below for the definition of a specific sub-TLV for use with the defined tunnel types.3. Use of IPsec Tunnel Types The IPsec tunnel types are defined above with the values 4, 5, and 6. If R1 is a BGP speaker that receives an Encapsulation SAFI update from another BGP speaker, R2, then if R1 has any data packets for which R2 is the BGP next hop, R1 MUST initiate an IPsec SA (security association) of the specified "tunnel type", and all such data packets MUST be sent through that SA. Let R1 and R2 be two BGP speakers that may send data packets through R3, such that the data packets from R1 and from R2 may be received by R3 over the same interface. In this case, when R3 sends an Encapsulation SAFI that indicates an IPsec tunnel type to R2, then R3 SHOULD also send an update specifying an Encapsulation SAFI with an IPsec tunnel type to R1. That is, on a given interface, if IPsec is required for any data packets, it SHOULD be required for all. This eliminates dependence on the IPsec selector mechanisms to correctly distinguish traffic that needs to be protected from traffic that does not. Security policy has the granularity of BGP speaker to BGP speaker. The required security policies must be configured into the BGP speakers. Policies for each SA will typically be established usingBerger, et al. Standards Track [Page 3]

RFC 5566             BGP IPsec Tunnel Encapsulation            June 2009   IKEv2 (Internet Key Exchange) [RFC4306], with either public-key or   pre-shared key authentication.  The SA MAY also be configured via   manual techniques.  Manual configuration specification and   considerations are defined in [RFC4301], [RFC4302], and [RFC4303]   (and includes keys, Security Parameter Index (SPI) numbers, IPsec   protocol, integrity/encryption algorithms, and sequence number mode).4.  IPsec Tunnel Authenticator sub-TLV   This document defines a new sub-TLV for use with the Tunnel   Encapsulation attribute defined in [RFC5512].  The new sub-TLV is   referred to as the "IPsec Tunnel Authenticator sub-TLV", and one or   more of the sub-TLVs MAY be included in any Encapsulation SAFI NLRI   [RFC5512] indicating a tunnel type defined in this document.  Support   for the IPsec Tunnel Authenticator sub-TLV MUST be implemented   whenever the tunnel types defined in this document are implemented.   However, its use is OPTIONAL, and is a matter of policy.   The sub-TLV type of the IPsec Tunnel Authenticator sub-TLV is 3.  The   sub-TLV length is variable.  The structure of the sub-TLV is as   follows:     - Authenticator Type: two octets       This document defines authenticator type 1, "SHA-1 hash of public       key", as defined inSection 3.7 of RFC 4306.     - Value: (variable)       A value used to authenticate the BGP speaker that generated this       NLRI.  The length of this field is not encoded explicitly, but       can be calculated as (sub-TLV length - 2).       In the case of authenticator type 1, this field contains the       20-octet value of the hash.   A BGP speaker that sends the IPsec Tunnel Authenticator sub-TLV with   authenticator type 1 MUST be configured with a private key / public   key pair, the public key being the key whose hash is sent in the   value field of the sub-TLV.  The BGP speaker MUST either (a) be able   to generate a self-signed certificate for the public key, or else (b)   be configured with a certificate for the public key.   When the IPsec Tunnel Authenticator sub-TLV is used, it is highly   RECOMMENDED that the integrity of the BGP session itself be   protected.  This is usually done by using the TCP MD5 option   [RFC2385].Berger, et al.              Standards Track                     [Page 4]

RFC 5566             BGP IPsec Tunnel Encapsulation            June 20094.1.  Use of the IPsec Tunnel Authenticator sub-TLV   If an IPsec Tunnel Authenticator sub-TLV with authenticator type 1 is   present in the Encapsulation SAFI update, then R1 (as defined above   inSection 3) MUST use IKEv2 [RFC4306] to obtain a certificate from   R2 (as defined above inSection 3), and R2 MUST send a certificate   for the public key whose hash occurred in the value field of the   IPsec Tunnel Authenticator sub-TLV.  R1 MUST NOT attempt to establish   an SA to R2 UNLESS the public key in the certificate hashes to the   same value that occurs in one of the IPsec Tunnel Authenticator sub-   TLVs.   R2 MUST also perform the reciprocal processing.  Specifically, when   establishing an SA from R1 and R1 has advertised the IPsec Tunnel   Authenticator sub-TLV with authenticator type 1, R2 MUST use IKEv2   [RFC4306] to obtain a certificate from R1, and R1 MUST send a   certificate for the public key whose hash occurred in the value field   of the IPsec Tunnel Authenticator sub-TLV.  R2 MUST NOT attempt to   establish an SA to R1 UNLESS the public key in the certificate hashes   to the same value that occurs in one of the IPsec Tunnel   Authenticator sub-TLVs.   Note that the "Transmit tunnel endpoint" tunnel type (value = 3) may   be used by a BGP speaker that does not want to be the receiving   endpoint of an IPsec tunnel but only the transmitting endpoint.5.  Security Considerations   This document uses IP-based tunnel technologies to support data plane   transport.  Consequently, the security considerations of those tunnel   technologies apply.  This document defines support for IPsec AH   [RFC4302] and ESP [RFC4303].  The security considerations from those   documents as well as [RFC4301] apply to the data plane aspects of   this document.   As with [RFC5512], any modification of the information that is used   to form encapsulation headers, to choose a tunnel type, or to choose   a particular tunnel for a particular payload type may lead to user   data packets getting misrouted, misdelivered, and/or dropped.   Misdelivery is less of an issue when IPsec is used, as such   misdelivery is likely to result in a failure of authentication or   decryption at the receiver.  Furthermore, in environments where   authentication of BGP speakers is desired, the IPsec Tunnel   Authenticator sub-TLV defined inSection 4 may be used.Berger, et al.              Standards Track                     [Page 5]

RFC 5566 BGP IPsec Tunnel Encapsulation June 2009 More broadly, the security considerations for the transport of IP reachability information using BGP are discussed in [RFC4271] and [RFC4272], and are equally applicable for the extensions described in this document. If the integrity of the BGP session is not itself protected, then an imposter could mount a denial-of-service attack by establishing numerous BGP sessions and forcing an IPsec SA to be created for each one. However, as such an imposter could wreak havoc on the entire routing system, this particular sort of attack is probably not of any special importance. It should be noted that a BGP session may itself be transported over an IPsec tunnel. Such IPsec tunnels can provide additional security to a BGP session. The management of such IPsec tunnels is outside the scope of this document.6. IANA Considerations IANA administers the assignment of new namespaces and new values for namespaces defined in this document and reviewed in this section. IANA has made the following assignments in the "BGP Tunnel Encapsulation Attribute Tunnel Types" registry. Value Name Reference ----- ---- --------- 3 Transmit tunnel endpoint [RFC5566] 4 IPsec in Tunnel-mode [RFC5566] 5 IP in IP tunnel with IPsec Transport Mode [RFC5566] 6 MPLS-in-IP tunnel with IPsec Transport Mode [RFC5566] IANA has made the following assignment in the "BGP Tunnel Encapsulation Attribute Sub-TLVs" registry. Value Name Reference ----- ---- --------- 3 IPsec Tunnel Authenticator [RFC5566]Berger, et al. Standards Track [Page 6]

RFC 5566             BGP IPsec Tunnel Encapsulation            June 20097.  References7.1.  Normative References   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate               Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC4271]   Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A               Border Gateway Protocol 4 (BGP-4)",RFC 4271, January               2006.   [RFC4301]   Kent, S. and K. Seo, "Security Architecture for the               Internet Protocol",RFC 4301, December 2005.   [RFC4302]   Kent, S., "IP Authentication Header",RFC 4302, December               2005.   [RFC4303]   Kent, S., "IP Encapsulating Security Payload (ESP)",RFC4303, December 2005.   [RFC4306]   Kaufman, C., Ed., "Internet Key Exchange (IKEv2)               Protocol",RFC 4306, December 2005.   [RFC5512]   Mohapatra, P. and E. Rosen, "The BGP Encapsulation               Subsequent Address Family Identifier (SAFI) and the BGP               Tunnel Encapsulation Attribute",RFC 5512, April 2009.7.2.  Informative References   [RFC2003]   Perkins, C., "IP Encapsulation within IP",RFC 2003,               October 1996.   [RFC2385]   Heffernan, A., "Protection of BGP Sessions via the TCP               MD5 Signature Option",RFC 2385, August 1998.   [RFC2784]   Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.               Traina, "Generic Routing Encapsulation (GRE)",RFC 2784,               March 2000.   [RFC3931]   Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,               "Layer Two Tunneling Protocol - Version 3 (L2TPv3)",RFC3931, March 2005.   [RFC4023]   Worster, T., Rekhter, Y., and E. Rosen, Ed.,               "Encapsulating MPLS in IP or Generic Routing               Encapsulation (GRE)",RFC 4023, March 2005.Berger, et al.              Standards Track                     [Page 7]

RFC 5566             BGP IPsec Tunnel Encapsulation            June 2009   [RFC4272]   Murphy, S., "BGP Security Vulnerabilities Analysis",RFC4272, January 2006.   [RFC4364]   Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private               Networks (VPNs)",RFC 4364, February 2006.   [RFC4659]   De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur,               "BGP-MPLS IP Virtual Private Network (VPN) Extension for               IPv6 VPN",RFC 4659, September 2006.   [RFC4798]   De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,               "Connecting IPv6 Islands over IPv4 MPLS Using IPv6               Provider Edge Routers (6PE)",RFC 4798, February 2007.   [RFC5549]   Le Faucheur, F. and E. Rosen, "Advertising IPv4 Network               Layer Reachability Information with an IPv6 Next Hop",RFC 5549, May 2009.   [RFC5565]   Wu, J., Cui, Y., Metz, C. and E. Rosen, "Softwire Mesh               Framework",RFC 5565, June 2009.8.  Acknowledgments   The authors wish to thank Sam Hartman and Tero Kivinen for their help   with the security-related issues.Authors' Addresses   Lou Berger   LabN Consulting, L.L.C.   Phone: +1-301-468-9228   EMail: lberger@labn.net   Russ White   Cisco Systems   EMail: riw@cisco.com   Eric C. Rosen   Cisco Systems, Inc.   1414 Massachusetts Avenue   Boxborough, MA, 01719   EMail: erosen@cisco.comBerger, et al.              Standards Track                     [Page 8]

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