One document matched: draft-ietf-pana-ipsec-03.txt

Differences from draft-ietf-pana-ipsec-02.txt


 

   PANA Working Group                                                    
   Internet Draft                                      M. Parthasarathy  
   Document: draft-ietf-pana-ipsec-03.txt                         Nokia  
   Expires: November 2004                                      May 2004  
  
  
                                        
                 PANA enabling IPsec based Access Control  
                                       
     
     
Status of this Memo  
     
   This document is an Internet-Draft and is in full conformance with  
   all provisions of Section 10 of RFC2026 [i].   
     
   This document is an Internet-Draft and is in full conformance with  
   all provisions of Section 10 of RFC2026 except that the right to  
   produce derivative works is not granted.   
  
   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.  
  
Copyright Notice  
  
   Copyright (C) The Internet Society (2003). All Rights Reserved.   
     
     
Abstract  
     
   The PANA (Protocol for carrying Authentication for Network Access)  
   working group is developing a protocol for authenticating clients to  
   the access network using IP based protocols.  The PANA protocol  
   authenticates the client and also establishes a PANA security  
   association between the PANA client and PANA authentication agent at  
   the end of a successful authentication. This document discusses the  
   details for establishing an IPsec security association using the PANA  
   security association for enabling IPsec based access control.  
  
  
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Table of Contents  
     
   1.0 Introduction..................................................2  
   2.0 Keywords......................................................3  
   3.0 Pre-requisites for IPsec SA establisment......................3  
   4.0 IP Address Configuration......................................3  
   5.0 IKE Pre-shared key derivation.................................4  
   6.0 IKE and IPsec details.........................................5  
   7.0 Packet Formats................................................6  
   8.0 IPsec SPD entries.............................................7  
   9.0 Dual Stack Operation.........................................10  
   10.0 Security considerations.....................................10  
   11.0 Normative References........................................11  
   12.0 Informative References......................................11  
   13.0 Acknowledgments.............................................12  
   14.0 Revision log................................................12  
   15.0 Appendix A..................................................13  
   16.0 Author's Addresses..........................................14  
   17.0 Full Copyright Statement....................................14  
     
     
1.0 Introduction  
     
   The PANA (Protocol for carrying Authentication for Network Access)  
   working group is developing a protocol for authenticating clients to  
   the access network using IP based protocols.  The PANA protocol  
   authenticates the client and also establishes a PANA security  
   association between the PANA client and PANA authentication agent at  
   the end of successful authentication. The PANA authentication agent  
   (PAA) indicates the results of the authentication using the PANA- 
   Bind-Request message wherein it can indicate the access control  
   method enforced by the access network. The PANA protocol [PANA-PROT]  
   does not discuss any details of IPsec [IPSEC] SA establishment, when  
   IPsec is used for access control. This document discusses the details  
   of establishing an IPsec security association between PANA client and  
   the enforcement point. When the IPsec SA is successfully established,  
   it can be used for access control and specifically used to prevent  
   the service theft mentioned in [PANA-THREATS].  
     
   Please refer to [PANAREQ] for terminology and definitions of terms  
   used in this document. The following picture illustrates what is  
   being protected with IPsec. As shown in Figure 1, Enforcement Point  
   (EP) and the Access Router (AR) are co-located. PAA is not shown in  
   the figure. It may or may not be co-located with EP. The IPsec  
   security association protects the traffic between PaC and EP. In  
   IPsec terms, EP is a security gateway (therefore a router) and  
   forwards packets coming from the PaC to other nodes.  
     
  
  
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                      PaC ----------------------+  
                      [D1]                      |  
                                                +------EP/AR  
                                                |  
                      PaC ----------------------+  
                      [D2]  
                      |-----------IPsec----------|  
     
                          Figure 1  
  
   First, this document discusses some of the pre-requisites for IPsec  
   SA establishment. Next, it gives details on what should be  
   communicated between PAA and EP. Then, it gives the details of  
   IKE/IPsec exchange with packet formats and SPD entries. Finally, it  
   discusses the issues when IPsec is used for remote access together  
   with local access.  
  
2.0 Keywords  
      
   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 [KEYWORDS].   
  
     
3.0 Pre-requisites for IPsec SA establisment  
  
   This document assumes that the following have already happened before  
   the IKE exchange starts.  
     
     1) PANA client (PaC) and PAA mutually authenticate each other using  
        EAP methods that derive AAA-key [EAP-KEY].  
       
     2) PaC learns the IP address of the Enforcement point (EP) during  
        the PANA exchange.  
     
     3) PaC learns that the network uses IPsec [IPSEC] for securing the  
        link between PaC and EP during the PANA exchange.  
  
4.0 IP Address Configuration  
  
   The IP address configuration is explained in [PANA-FRAME]. Some of  
   the details relevant to IPsec are briefly repeated here for clarity.   
  
  
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   PaC configures an IP address before the PANA protocol exchange  
   begins. This address is called a pre-PANA address (PRPA). After a  
   successful authentication, the client may have to configure a post- 
   PANA address (POPA) for communication with other nodes, if PRPA is a  
   local-use (e.g., link-local or private address) or a temporarily  
   allocated IP address.  
     
   The PRPA of the PaC may be a link-local address [IPV4-LINK] or a  
   private address [IPv4-PRIV] or a routable address. Please refer to  
   [PANA-FRAME] for more details on how these addresses may be  
   configured. PaC would use the PRPA as the outer address of IPsec  
   tunnel mode SA (IPsec-TOA). PaC also needs to configure an inner  
   address (IPsec-TIA). There are different ways to configure IPsec-TIA.  
     
     1) Some IPv4 IPsec implementations are known to work properly when  
        the same address is configured as both the IPsec-TIA and IPsec- 
        TOA. When PRPA is a routable address, PRPA may be used as both  
        IPsec-TIA and IPsec-TOA and POPA may not be configured.  
  
     2) In IPv4, an IPsec-TIA can be obtained via the configuration  
        method available within [RFC3456]. The minor difference from the  
        original usage of RFC 3456 is that the IPsec-TOA does not need  
        to be a routable address when [RFC3456] is used between PaC and  
        EP.  
  
     3) When [IKEV2] is used for security association negotiation, the  
        address configuration method available in [IKEV2] can be used  
        for configuring the IPsec-TIA for both IPv4 and IPv6.  
     
   There are other address configuration methods possible. They have  
   some implementation issues, which are described in the Appendix A.  
  
5.0 IKE Pre-shared key derivation  
     
   If the network chooses IPsec to secure the link between PaC and EP,  
   PAA should communicate the IKE pre-shared key, Key-Id, PRPA of the  
   PaC, and the session-Id to EP before the IKE exchange begins.  
   Whenever the IKE pre-shared key changes due to re-authentication as  
   described below, the new value is computed by the PAA and  
   communicated to the EP with all the other parameters.  
     
   The IKE exchange between PaC and PAA is equivalent to the 4-way  
   handshake in [IEEE80211i] following the EAP exchange. The IKE  
   exchange establishes the IPsec SA similar to the pair-wise transient  
   keys (PTK) established in [IEEE80211i]. The IKE exchange provides  
   both key confirmation and protected cipher-suite negotiation.  
     
   IKE pre-shared key is derived as follows.  
     
  
  
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   IKE Pre-shared Key = HMAC-SHA-1 (AAA-key, "IKE-preshared key" |  
                           Session ID | Key-ID | EP-address)  
     
   The values have the following meaning:    
     
   AAA-key: A key derived by the peer and EAP server and transported to  
   the authenticator [EAP-KEY].  
     
   Session ID: The value as defined in the PANA protocol [PANA-PROT],  
   identifies a particular session of a client.  
     
   Key-ID: This identifies the AAA-key within a given session [PANA- 
   PROT]. During the lifetime of the PANA session, there could be  
   multiple EAP re-authentications. As EAP re-authentication changes the  
   AAA-key, key-ID is used to identify the right AAA-key. This is  
   contained in the Key-Id AVP [PANA-PROT].  
     
   EP-address: This is the address of the enforcement point with which  
   the IKE exchange is being performed. When PAA is controlling multiple  
   EPs, this provides a different pre-shared key for each of the EPs.  
     
   The character "|" denotes concatenation as defined in [IKE].  
     
   During EAP re-authentication, the AAA-key changes. Whenever the AAA- 
   key changes, a new value of Key-ID is established between the PaC and  
   PAA/EP as defined in [PANA-PROT]. If there is already an IKE SA or  
   IPsec SA established, it MUST continue to be used till it expires. A  
   change in the value of AAA-key MUST NOT result in re-negotiating a  
   new IKE SA or IPsec SA immediately. But any new negotiation of IKE SA  
   or IPsec SA MUST use the new pre-shared key derived from the latest  
   AAA-key and is indicated by the Key-ID in the above equation.  
     
  
6.0 IKE and IPsec details  
     
   IKE [IKE] MUST be used for establishing the IPsec SA. The details  
   specified in this document would work with IKEv2 [IKEV2] also. Any  
   difference between them would be explicitly noted. PANA authenticates  
   the client and derives the keys to protect the traffic. Hence, manual  
   keying cannot be used. Aggressive mode with pre-shared key MUST be  
   supported. PaC and EP SHOULD use the following value in the payload  
   of the ID_KEY_ID to identify the pre-shared key.  
     
           ID_KEY_ID data = (Session-Id | Key-Id)  
     
   The Session-Id and Key-Id are the values contained in the data  
   portion of the Session-Id and Key-Id AVP respectively [PANA-PROT].  
   They are concatenated to form the content of ID_KEY_ID data. IP  
   addresses cannot be used as identifier as the PaC may be re- 
  
  
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   authenticated multiple times and hence may not uniquely identify the  
   pre-shared key. For the same reason, main mode of IKE cannot be used,  
   as it requires addresses to be used as identifiers.  
     
   After Phase I SA is established, quick mode exchange is performed to  
   establish an ESP tunnel mode IPsec SA for protecting the traffic  
   between PaC and EP. The identities used during Phase II are explained  
   in the next section. As mentioned in section 4.0, and address (POPA)  
   may also have to be configured. The address configuration method to  
   be used by the PaC is indicated in the PANA-Bind-Request message at  
   the end of the successful PANA authentication. The PaC chooses the  
   appropriate method and replies back in PANA-Bind-Answer message.  
  
7.0 Packet Formats  
  
   Following acronyms are used throughout this document.  
  
   PAC-TIA denotes the IPsec-TIA used by the PaC. PAC-TIA may be set to  
   a PRPA when the same PRPA is used as IPsec-TIA and IPsec-TOA on the  
   PaC. Otherwise, PAC-TIA is set to POPA.  
     
   PAC-TOA denotes the IPsec-TOA used by the PaC.  
     
   EP-ADDR denotes the address of the EP.  
     
   The node with which the PaC is communicating is denoted by END-ADDR.  
  
   Following is the IPv4 packet format on the wire for packets sent from  
   PaC to EP:  
     
         IPv4 header      (source = PAC-TOA,  
                           destination = EP-ADDR)  
         ESP  header  
         IPv4 header      (source = PAC-TIA,  
                           destination = END-ADDR)  
     
   Following is the IPv6 packet format on the wire for packets sent from  
   PaC to EP:  
     
         IPv6 header      (source = PAC-TOA,  
                           destination = EP-ADDR)  
         ESP  header  
         IPv6 header      (source = PAC-TIA,  
                           destination = END-ADDR)  
     
   Following is the IPv4 packet format on the wire for packets sent from  
   EP to PaC:  
  
         IPv4 header      (source = EP-ADDR,  
  
  
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                           destination = PAC-TOA)  
         ESP  header  
         IPv4 header      (source = END-ADDR,  
                           destination = PAC-TIA)  
     
   Following is the IPv6 packet format on the wire for packets sent from  
   EP to PaC:  
  
         IPv6 header      (source = EP-ADDR,  
                           destination = PAC-TOA)  
         ESP  header  
         IPv6 header      (source = END-ADDR,  
                           destination = PAC-TIA)  
     
8.0 IPsec SPD entries  
     
   The SPD entries for IPv4 and IPv6 are specified separately as they  
   are different. All the SPD entries are dynamically created. When the  
   same address is used as IPsec-TIA and IPsec-TOA, EP can add the entry  
   to the SPD before the IKE exchange starts, as it knows the address a  
   priori. When [IKEV2] or [RFC3456] is used for address configuration,  
   the SPD entry cannot be created until the IPsec SA is successfully  
   negotiated as the address is not known a priori. This is very similar  
   to the road warrior case described in [IPSEC-BIS]. In this case, an  
   SPD entry with a name selector is used to start with and later  
   changed with the appropriate addresses. The name used here could be  
   the contents of ID_KEY_ID payload. The entries shown below are the  
   entries that are added after the successful IPsec SA negotiation.  
     
   The SPD entries shown here affect the flow of data traffic, which  
   includes neighbor discovery messages for IPv6. When PAA and EP are  
   not co-located, any traffic destined to PAA is forwarded to PAA after  
   decrementing the TTL in the IP header. PAA would drop the packet if  
   the TTL is not 255. PaC also would drop the packets coming from PAA  
   if the TTL is not 255. Hence, we need the following SPD entry on PaC  
   and EP for bypassing IPsec protection for PANA traffic.  
     
      If source_port = PANA_PORT OR dest_port = PANA_PORT  
          THEN BYPASS  
     
   PANA_PORT is the IANA assigned (TBD) PANA protocol number [PANA- 
   PROT]. There may be other protocols that expect the TTL to be 255  
   whose SPD entries are not shown here. Also, when the PaC is using  
   IPsec for remote access, there may be additional SPD entries and  
   IPsec security associations, which are not discussed in this  
   document.  
     
     

  
  
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8.1 IPv4 SPD entries  
  
   PaC's SPD OUT:  
             IF source = PAC-TIA & destination = any  
              THEN USE ESP TUNNEL MODE SA:  
              outer source = PAC-TOA  
              outer destination = EP-ADDR  
     
   PaC's SPD IN:  
            IF source = any & destination = PAC-TIA  
             THEN USE ESP TUNNEL MODE SA:  
             outer source = EP-ADDR  
             outer destination = PAC-TOA  
              
   EP's SPD OUT:  
            IF source = any & destination = PAC-TIA  
             THEN USE ESP TUNEL MODE SA:  
             outer source = EP-ADDR  
             outer destination = PAC-TOA  
     
   EP's SPD IN:  
            IF source = PAC-TIA & destination = any  
             THEN USE ESP TUNNEL MODE SA:  
              outer source = PAC-TOA  
              outer destination = EP-ADDR  
     
   During the IPsec SA setup, PaC uses PAC-TIA as its phase 2 identity  
   (IDci) and EP uses ID_IPV4_ADDR_RANGE or ID_IPV4_ADDR_SUBNET as its  
   phase 2 identity. The starting address is zero IP address and the end  
   address is all ones for ID_IPV4_ADDR_RANGE. The starting address is  
   zero IP address and the end address is all zeroes for  
   ID_IPV4_ADDR_SUBNET.  
     
8.2 IPv6 SPD entries  
     
   The IPv6 SPD entries are slightly different from IPv4 to prevent the  
   neighbor and router discovery [IPV6-ND] packets from being protected  
   with IPsec. The first three entries of the following SPD entries  
   bypass IPsec protection for neighbor and router discovery packets.  
   The latest version of the IPsec [IPSEC-BIS] document allows traffic  
   selectors to be based on ICMPv6 type and code values. In that case,  
   the first three entries can be based on ICMPv6 type and code values.  
     
   Pac's SPD OUT:  
     
             IF source = ::/128  & destination = any  
              THEN BYPASS  
     
  
  
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             IF source = fe80::/10 & destination = any  
             THEN BYPASS  
            
             IF source = any & destination = fe80::/10  
              THEN BYPASS  
  
             IF source = PAC-TIA & destination = any  
              THEN USE ESP TUNNEL MODE SA:  
                 outer source = PAC-TOA  
                 outer destination = EP-ADDR  
     
   PaC's SPD IN:  
     
             IF source = ::/128 & destination = any  
              THEN BYPASS  
     
             IF source = fe80::/10 & destination = any  
             THEN BYPASS  
            
             IF source = any & destination = fe80::/10  
              THEN BYPASS  
     
             IF source = any & destination = PAC-TIA  
                 THEN USE ESP TUNNEL MODE SA:   
                    outer source = EP-ADDR  
                    outer destination = PAC-TOA  
               
   EP's SPD OUT:  
     
             IF source = ::/128 & destination = any  
              THEN BYPASS  
     
             IF source = fe80::/10 & destination = any  
             THEN BYPASS  
            
             IF source = any & destination = fe80::/10  
              THEN BYPASS  
  
             IF source = any & destination = PAC-TIA  
                 THEN USE ESP TUNNEL MODE SA:  
                    outer source = EP-ADDR  
                    outer destination = PAC-TOA  
     
   EP's SPD IN:  
     
             IF source = ::/128 & destination = any  
              THEN BYPASS  
     
             IF source = fe80::/10 & destination = any  
  
  
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             THEN BYPASS  
            
             IF source = any & destination = fe80::/10  
              THEN BYPASS  
  
             IF source = PAC-TIA & destination = any  
              THEN USE ESP TUNNEL MODE SA:  
                 outer source = PAC-TOA  
                 outer destination = EP-ADDR  
     
     
   During the IPsec SA setup, PaC uses PAC-TIA as its phase 2 identity  
   (IDci) and EP uses ID_IPV6_ADDR_RANGE or ID_IPV6_ADDR_SUBNET as its  
   phase 2 identity. The starting address is zero IP address and the end  
   address is all ones for ID_IPV6_ADDR_RANGE. The starting address is  
   zero IP address and the end address is all zeroes for  
   ID_IPV6_ADDR_SUBNET.  
     
9.0 Dual Stack Operation  
  
   [IKEV2] can enable configuration of IPsec-TIA for both IPv4 and IPv6  
   TIAs by sending both IPv4 and IPv6 configuration attributes in the  
   configuration request (CFG-REQUEST). This enables use of single IPsec  
   tunnel mode SA for sending both IPv4 and IPv6 traffic. Therefore,  
   IKEv2 is recommended for handling dual-stack PaCs where single  
   execution of IKE is desired.  
  
10.0 Security considerations  
     
   This document discusses the use of IPsec for access control when PANA  
   is used for authenticating the clients to the access network.  
     
   If the EP does not verify whether PaC is authorized to use an IP  
   address, it is possible for the PaC to steal the traffic destined to  
   some other PaC. When [IKEV2] and [RFC3456] is used for address  
   configuration, the address is assigned by the EP and hence this  
   attack is not present in such cases. When the same address is used as  
   both IPsec-TIA and IPsec-TOA, EP creates the SPD entry with the  
   appropriate address for the PaC and hence the address is verified  
   implicitly by the virtue of successful IPsec SA negotiation.  
     
   When IPv6 is used, the SPD entries bypass all link-local traffic  
   without applying IPsec. This should not be a limitation as the link- 
   local address is used only by link-local services e.g.  
   neighbor/router discovery, which uses a [SEND] to protect their  
   traffic. Moreover, this limitation may not be there in the future if  
   IPsec extends the SPD selectors to specify ICMP types.  


  
  
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11.0 Normative References  
  
   Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9,  
      RFC 2026, October 1996.  
     
   [IPSEC] S. Kent et al., "Security Architecture for the Internet  
      Protocol", RFC 2401, November 1998  
     
   [PANA-PROT] D. Fosberg et al., "Protocol for Carrying Authentication  
      for Network Access", draft-ietf-pana-03.txt  
     
   [PANA-THREATS] M. Parthasarathy, "PANA Threat analysis and security  
      requirements", draft-ietf-pana-threats-eval-04.txt  
  
12.0 Informative References  
  
   [PANAREQ] A. Yegin et al., "Protocol for Carrying Authentication for  
      Network Access (PANA) Requirements and Terminology", draft-ietf- 
      pana-requirements-04.txt  
     
   [PANA-FRAME] P. Jayaraman et al., "PANA Framework", draft-ohba-pana- 
      framework-00.txt   
     
   [KEYWORDS] S. Bradner, "Key words for use in RFCS to indicate  
      requirement levels", RFC 2119, March 1997  
     
   [IKE] D. Harkins et al., "Internet Key Exchange", RFC 2409, November  
      1998  
     
   [IKEV2] C. Kauffman et al., "Internet Key Exchange(IKEv2) Protocol",  
      draft-ietf-ipsec-ikev2-11.txt  
     
   [IPSEC-BIS] S. Kent, "Security Architecture for the Internet  
      Protocol", draft-ietf-ipsec-rfc2401bis-00.txt  
     
   [DHCP] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131,  
      March 1997  
     
   [RFC3456] B. Patel et al., "Dynamic Host Configuration Protocol  
      (DHCPv4) Configuration of IPsec Tunnel Mode", RFC 3456, January  
      2003  
     
   [DHCPV6] R. Droms et. al, "Dynamic Host Configuration Protocol for  
      IPv6", RFC 3315, July 2003  
      
   [IPV6-ND] T. Narten et al., "Neighbor Discovery for IP version 6  
      (IPv6) ", RFC 2461, December 1998  
     
  
  
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   [IPV6-CONF] S. Thomson et. al, "IPv6 Stateless Address  
      Autoconfiguration", RFC 2462, December 1998  
     
   [PRIV] T. Narten et al., "Privacy Extensions for Stateless Address  
      Autoconfiguration in IPv6", RFC 3041, January 2001  
     
   [EAP-KEY] D. Simon et al., "EAP Key Management Framework", draft- 
      ietf-eap-keying-01.txt  
     
   [SEND] J. Arkko et al., "Secure Neighbor Discovery", draft-ietf-send- 
      ndopt-03.txt  
     
   [IPV4-LINK] B. Aboba et al., "Dynamic configuration of Link-local  
      IPv4 addresses", draft-ietf-zeroconf-ipv4-linklocal-12.txt  
     
   [IPV4-PRIV] Y. Rekhter et al., "Address Allocation for Private  
      Internets", BCP 5, RFC 1918, February 1996  
     
   [IEEE80211i] IEEE Draft 802.11I/D5.0, "Draft Supplement to STANDARD  
      FOR Telecommunications and Information Exchange between Systems –  
      LAN/MAN Specific Requirements - Part 11: Wireless Medium Access  
      Control (MAC) and physical layer specifications: Specification for  
      Enhanced Security", August 2003.  
  
13.0 Acknowledgments  
     
   The author would like to thank Francis Dupont, Pasi Eronen, Yoshihiro  
   Ohba, Jari Arkko, Hannes Tschofenig, Alper Yegin and other PANA WG  
   members for their valuable comments and discussions.  
     
14.0 Revision log  
  
   Changes between revision 02 and 03  
     
   -Clarified the use of key-Id in ID_KEY_ID payload  
   -Clarified the address configuration issues.  
   -Added an Appendix to clarify implementation issues.  
     
   Changes between revision 01 and 02  
     
   -Updated the draft with the fixes for all open issues  
   -Added the IP configuration section  
   -Modified the IKE pre-shared key derivation to handle PAA controlling  
   multiple EPs  
   -Clarification regarding DHCP usage and RFC3456 usage.  
   -Only aggressive mode to be supported. Main mode not needed anymore.  
  
   Changes between revision 00 and 01  
     
  
  
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   -Specified the use of ESP tunnel mode SA instead of IP-IP transport  
   mode SA after working group discussion.  
   -Specified the IKE pre-shared key derivation.  
  
15.0 Appendix A  
  
   This section describes the alternate address configuration methods  
   for Post-PANA address (POPA) and the issues associated with it. As  
   mentioned in section 4, there are multiple ways by which the PaC may  
   configure the POPA address. Only [IKEV2] and [RFC3456] address  
   configuration methods were described in section 4. Other  
   possibilities and the issues are as follows.  
     
     1) Some IKEv1 implementations support IKEv1 MODECFG for configuring  
        IP address. There is no RFC describing MODECFG feature of IKEv1.  
        Also, there is not much information on its widespread support  
        among the implementations. Hence, this document does not  
        recommend it.  
  
     2) The address may also be obtained using [DHCP] [DHCPV6] before  
        the IKE exchange starts. Normally the implementations associate  
        the address and other configuration information (e.g. default  
        router) with the interface on which the DHCP is performed. This  
        can cause problems with implementations if they attempt to use  
        an IP address that is configured via [DHCP] [DHCPV6] on the  
        physical interface and use it as IPsec-TIA on the IPsec tunnel  
        interface. This may work without problems when IPsec-TIA and  
        IPsec-TOA are same as the IPv4 PRPA that was obtained using  
        DHCP, as the source address selection has to deal with just one  
        address. But using an IPv4 IPsec-TOA different than IPsec-TIA on  
        a single interface may cause source address selection problem,  
        as there is more than one address to be dealt with. Similarly,  
        an IPv6 address obtained and maintained through a physical link  
        but used on a tunnel interface requires additional  
        implementation considerations. Therefore, this document does not  
        handle the case where DHCP is used to acquire an address for  
        IPsec-TIA that is different from IPsec-TOA.  
  
     3) The address may also be obtained using auto-configuration [IPV6- 
        ND] including the privacy addresses described in [PRIV]. The  
        problem described above for DHCP applies to this also. The  
        implementations would associate the auto-configured addresses  
        and the default router with the interface on which the router  
        advertisement was received. As we configure the SPD to bypass  
        IPsec for router discovery and neighbor discovery messages, the  
        address would be associated with the physical interface and not  
        with the IPsec interface. There is also an additional issue, as  
        the address configured by the PaC is not known to the EP. It  
        needs to trust whatever PaC provides in its traffic selector  
  
  
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        during the IPsec SA negotiation. This leads to DoS attack where  
        the PaC can steal some other PaC's address, which cannot be  
        prevented unless [SEND] is deployed.  
  
16.0 Author's Addresses  
     
   Mohan Parthasarathy  
   313 Fairchild Drive  
   Mountain View CA-94043  
     
   Phone: 408-734-8820  
   Email: mohanp@sbcglobal.net  
  
17.0 Full Copyright Statement  
     
   Copyright (C) The Internet Society (2003).  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.  However, this  
   document itself may not be modified in any way, such as by removing  
   the copyright notice or references to the Internet Society or other  
   Internet organizations, except as needed for the purpose of  
   developing Internet standards in which case the procedures for  
   copyrights defined in the Internet Standards process must be  
   followed, or as required to translate it into languages other than  
   English.  
     
   The limited permissions granted above are perpetual and will not be  
   revoked by the Internet Society or its successors or assigns.  
     
        
   This document and the information contained herein is provided on an  
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING  
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING  
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION  
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF  
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
     
   Acknowledgement  
     
   Funding for the RFC Editor function is currently provided by the  
   Internet Society.  
     
     

  
  
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PAFTECH AB 2003-20262026-04-21 19:43:50