R. Bonica WorldCom Internet Draft Y. Rekhter Expiration Date: May 2002 Juniper Networks R. Raszuk E. Rosen D. Tappan Cisco Systems November 2001 CE-to-CE Authentication for RFC 2547 VPNs draft-bonica-l3vpn-auth-01.txt 1. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of [RFC-2026]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 2. Abstract This document describes a magic cookie approach to VPN authentication. In order to support authentication, each VPN site sends the PE router that supports it a magic cookie. Only after the PE has received the magic cookie will it accept traffic from the customer interface that supports the VPN site. In many cases, the Customer Edge (CE) router originates the magic cookie. In configurations where the service provider manages the CE, the customer may designate another device contained by the VPN site to originate the magic cookie. Having received the magic cookie, the PE router distributes it throughout the provider network. All PE's that support the VPN receive the magic cookie and relay it to each attached CE router that participates in the VPN. CE routers use the magic cookie to authenticate their VPN peers. If a CE receives a magic cookie that it cannot authenticate, it issues an alarm requesting operator intervention. The CE may also withdraw from the VPN, neither sending traffic to the VPN nor accepting traffic from the VPN until an operator clears the security condition. 3. Overview RFC 2547 VPNs [2547bis] support routing privacy among customer interfaces. In order to support routing privacy, Provider Edge (PE) routers maintain multiple forwarding table instances, with each forwarding table instance representing a VPN. Service providers assign customer interfaces to these VPN specific routing table instances. In doing so, the service provider assigns the customer interface to a VPN. The service provider assures VPN customers that all VPN traffic will remain within the VPN. Conversely, the service provider assures VPN customers that VPN interfaces will never receive datagrams that originated outside of the VPN. In order to provide these assurances, the service provider must configure its PE routers correctly. If the service provider assigns a customer interface to the wrong forwarding table instance, or commits some other configuration error, unauthorized parties might join a VPN, while legitimate VPN members are unaware of the security breach. Therefore, some VPN customers may require a CE-based authentication mechanism. VPN customers could use the CE-based authentication mechanism to protect themselves from security breaches caused by misconfiguration of the provider network. This document describes such a mechanism. Specifically, this document describes a magic cookie approach to VPN authentication. In order to support authentication, each VPN site sends the PE router that supports it a magic cookie. Only after the PE has received the magic cookie will it accept traffic from the customer interface that supports the VPN site. In many cases, the Customer Edge (CE) router originates the magic cookie. In configurations where the service provider manages the CE, the customer may designate another device contained by the VPN site to originate the magic cookie. Having received the magic cookie, the PE router distributes it throughout the provider network. All PE's that support the VPN receive the magic cookie and relay it to each attached CE router that participates in the VPN. CE routers use the magic cookie to authenticate their VPN peers. If a CE receives a magic cookie that it cannot authenticate, it issues an alarm requesting operator intervention. The CE may also withdraw from the VPN, neither sending traffic to the VPN nor accepting traffic from the VPN until an operator clears the security condition. Note that the PE will not accept any traffic from a VPN site until it has received a magic cookie from that VPN site. Furthermore, the PE will not distribute any VPN routes representing a VPN site until it has received a magic cookie from that VPN site. Note also that the PE will not reveal any magic cookie information to the CE until it has received a magic cookie from the customer site that the CE supports. The magic cookie approach described by this document contains three components. These are 1) Customer-to-PE signaling, 2) PE-to-PE signaling and 3) PE-to-CE signaling. This document dedicates a section to each component. 4. 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 [RFC-2119]. 5. Customer-to-PE Signaling In order to support CE-based authentication, each VPN site must send one or more magic cookies to the PE router that supports it. In many cases, the CE will originate the magic cookie. In configurations where the service provider manages the CE, the customer may designate another device contained by the VPN site to originate the magic cookie. If the device that originates the magic cookie also maintains a BGP peering session with the PE, the originating device can piggyback magic cookie information on this BGP peering session. Section 6 of this document describes an extended BGP community attribute that supports this purpose. Section 8 of this document specifies an alternative protocol that can be used to propagate magic cookies. This protocol can be used in any VPN configuration, including the configuration mentioned above. 6. PE-to-PE Signaling In order to support CE-based authentication, the PE router must not activate routes to destinations that are contained by a directly connected VPN site until it has received a magic cookie from the VPN site. When the PE has received a magic cookie, it will activate those routes and advertise them to its iBGP peers. (That is, the PE will advertise those routes to remote PE routers that support the VPN.) As the PE advertises those routes, it appends the magic cookie to each BGP update. To support this purpose, this document defines a new extended community attribute type, called CE-to-CE Authentication Token. The extended community attribute [EXTBGP] is data structure that contains eight octets. The first two octets represent a community type and the remaining six octets represent a value. The high-order octet of the Type field is set to 0x03. The low-order octet of the Type field is TBD (to be assigned by the IANA). The Value field carries the magic cookie. This extended community will be transitive and optional. 7. PE-to-CE Signaling Previous sections of this document describe how the PE router acquires a magic cookie to be associated with each route that is active in its forwarding table. Section 5 describes how the PE acquires magic cookies to be associated with routes to destinations that are contained by directly connected VPN sites. Section 6 describes how the PE acuires magic cookies to be associated with routes to destinations that are contained by remote VPN sites. In order to support CE-based authentication, the PE router must relay these magic cookies to directly connected CE routers. If the PE and CE routers maintain a BGP peering session with one another, the PE can use this BGP peering session to send magic cookies to the CE. Section 6 of this document describes a BGP extended community attribute that supports this purpose. Section 8 of this document describes an alternative protocol that the PE can use to send magic cookies to the CE. This protocol can be used in any VPN configuration, including the configuration mentioned above. The PE must relay every magic cookie that it has acquired regarding a VPN to each CE router that participates in the VPN. When the CE router receives a new magic cookie, it must relay it to the appropriate CE routers immediately. Furthermore, the PE router MUST not reveal any magic cookie information to CE routers that are contained by sites from which a magic cookie has not yet been received. 8. Protocol Support This section describes a protocol that PE and CE routers use to exchange magic cookies with one another. The protocol can obtain transport services from TCP or SSH. IANA will assign a TCP port to support this protocol. The protocol supports the following message types: UPDATE KEEPALIVE The format of these messages is TBD. Protocol partners exchange magic cookie information using the UPDATE message. Protocol partners must send each other KEEPALIVE messages every 90 seconds. Having missed four consecutive KEEPALIVE messages, the protocol partner will reset the peering session. When the peering session terminates, all magic cookies that were distributed through the peering session are withdrawn. 9. Security Considerations If VPN customer receives a magic cookie that it cannot authenticate, the VPN customer should contact his/her service provider immediately. The VPN customer should also consider changing its magic cookie value, as the service provider may have revealed that value to an unauthorized party. If the VPN customer maintains backdoor interfaces outside of the VPN, the VPN customer MUST ensure that parties outside of the VPN cannot sends signaling traffic to PE-CE interfaces. 10. IANA Considerations IANA will assign a new extended BGP community sub-type, with the high-order octet of the Type field equal to 0x03. This BGP extended community type will represent the CE-to-CE Authentication Token. IANA will also assign a TCP port to support the CE-based- Authentication Protocol. 11. Acknowledgements Thanks to Beth Alwin, Eduard Metz and Richard Morgan for their comments on this draft. 12. References [2547bis], Rosen, E. et al., "BGP/MPLS VPSs", July, 2001, draft- ietf-ppvpn-rfc2547bis-00. [RFC-1771], Rekhter, Y., Li, T., "A Border Gateway Protocol (BGP- 4)", RFC 1771, March 1995. [RFC-2026], Bradner, S., "Internet Standards Process Revision 3", RFC 2026, Harvard University, October 1996. [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, Harvard University, March 1997 [EXTBGP], "BGP Extended Communities Attribute", Ramachandra, S., Tappan, D., Rekhter, Y., June 2001, draft-ietf-idr-bgp-ext- communities-02.txt 13. Author's Addresses Ronald P. Bonica WorldCom 22001 Loudoun County Pkwy Ashburn, Virginia, 20147 Phone: 703 886 1681 Email: ronald.p.bonica@wcom.com Yakov Rekhter Juniper Networks, Inc. 1194 N. Mathilda Ave. Sunnyvale, California 94089 Email: yakov@juniper.net Eric C. Rosen Cisco Systems, Inc. 250 Apollo Drive Chelmsford, MA, 01824 Email: erosen@cisco.com Robert Raszuk Cisco Systems, Inc. 250 Apollo Drive Chelmsford, MA, 01824 Email: raszuk@cisco.com Dan Tappan Cisco Systems, Inc. 250 Apollo Drive Chelmsford, MA 01824 Email: tappan@cisco.com 14. Full Copyright Statement Copyright (C) The Internet Society (2000). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 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