One document matched: draft-ietf-pana-threats-eval-04.txt

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   PANA Working Group                                                    
   Internet Draft                                      M. Parthasarathy  
   Category: Informational                               Tahoe Networks
   Document: draft-ietf-pana-threats-eval-04.txt               May 2003 
   Expires: November 2003
  
  
                                        
              PANA Threat Analysis and Security Requirements  
                                       
     
     
Status of this Memo  
     
   This document is an Internet-Draft and is in full conformance with  
   all provisions of Section 10 of RFC2026.   
     
   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 methods for authenticating clients to the  
   access network using IP based protocols. This document discusses the  
   threats to such protocols. The security requirements arising out of  
   these threats will be used as additional input to the PANA WG for  
   designing the IP based network access authentication protocol.  
  
  
  
  
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Table of Contents  
     
   1.0 Introduction..................................................2  
   2.0 Keywords......................................................2  
   3.0 Terminology and Definitions...................................3  
   4.0 Usage Scenarios...............................................4  
   5.0 Trust Relationships...........................................4  
   6.0 Threat Scenarios..............................................5  
      6.1 PAA Discovery..............................................6  
      6.2 Authentication.............................................7  
      6.3 PaC leaving the network...................................10  
      6.4 Service theft.............................................11  
      6.5 PAA-EP communication......................................11  
      6.6 Miscellaneous attacks.....................................12  
   7.0 Summary of Requirements......................................13  
   8.0 Security Considerations......................................14  
   9.0 Normative References.........................................14  
   10.0 Informative References......................................14  
   11.0 Acknowledgments.............................................15  
   12.0 Revision Log................................................15  
   13.0 Author's Address............................................16  
   14.0 Full Copyright Statement....................................16  
     
1.0 Introduction  
     
   The PANA (Protocol for carrying authentication for Network Access)  
   working group is developing methods for authenticating clients to the  
   access network using IP based protocols. This document discusses the  
   threats to such IP based protocols.    
     
   A client wishing to get access to the network must carry on multiple  
   steps. First, it needs to discover the IP address of the PANA  
   authentication agent (PAA) and then execute an authentication  
   protocol to authenticate itself to the network. Once the client is  
   authenticated, there might be other messages exchanged during the  
   lifetime of the network access. This document discusses the threats  
   in these steps without discussing any solutions. The requirements  
   arising out of these threats will be used as input to the PANA  
   working group.  
  
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].   
     
     

  
  
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3.0 Terminology and Definitions  
  
   Client Access Device  
     
      A network element (e.g., notebook computer, PDA, etc.) that  
      requires access to a provider's network.  
     
   Network Access Server (NAS)  
     
      Network device that provides access to the network.  
        
   PANA Client (PaC)  
     
      An entity in the edge subnet, who is wishing to obtain network  
      access from a PANA authentication agent within a network. A PANA  
      client is associated with a device and a set of credentials to  
      prove its identity within the scope of PANA.  
     
   PANA Authentication Agent (PAA)  
     
      An entity whose responsibility is to authenticate the PANA client  
      and grant network access service to the client's device.  
     
   Authentication Server (AS)  
     
      An entity that authenticates the PANA client. It may be co-located  
      with PANA authentication agent or part of the back-end  
      infrastructure.  
        
   Device Identifier (DI)  
     
      The identifier used by the network as a handle to control and  
      police the network access of a client. Depending on the access  
      technology, identifier might contain any of IP address, link-layer  
      address, switch port number, etc. of a device. PANA authentication  
      agent keeps a table for binding device identifiers to the PANA  
      clients. At most one PANA client should be associated with a DI on  
      a PANA authentication agent.  
        
   Enforcement Point (EP)  
     
      A node that is capable of filtering packets sent by the PANA  
      client using the DI information authorized by PANA authentication  
      agent.  
  
   Compound methods  
     


  
  
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      Authentication protocol where, sequence of methods are used one  
      after an other or where methods are tunneled inside an another  
      independently established tunnel between the client and server  
      [TUN-EAP].  
     
4.0 Usage Scenarios  
     
   PANA is intended to be used in an environment where there is no a  
   priori trust relationship or security association between the PaC and  
   other nodes like PAA and EP. In these environments, one may observe  
   the following.  
      
       o The link between PaC and PAA may be a shared medium       
          (e.g., Ethernet) or may not be a shared medium (e.g., DSL  
          network).  
  
       o All the PaCs may be authenticated to the access network at  
          layer 2 (e.g., 3GPP2 CDMA network) and share a security  
          association with layer 2 authentication agent (e.g., 802.11  
          [IEEE-802.11] Access point), but still do not trust each  
          other.  
  
   The scenarios mentioned above affect the threat model of PANA. This  
   document discusses the various threats in the context of the above  
   network access scenarios for a better understanding of the threats.  
   In the following discussion, any reference to link that is not shared  
   (or non-shared) is assumed to be physically secure. If such an  
   assumption cannot be made about the link, then it becomes the same as  
   the link that is being shared by more than one node.  
  
5.0 Trust Relationships  
     
   PANA authentication involves a client (PaC), PANA agent (PAA),  
   Authentication server (AS) and an Enforcement point (EP).   
     
   The entities that have a priori trust relationships before PANA  
   begins are as follows.  
     
     1) PAA and AS: PaC belonging to the same administrative domain as  
        the AS, often needs to use resources provided by PAA that  
        belongs to another administrative domain. PAA authenticates the  
        PaC before providing local network access. The credentials  
        provided by PaC for authentication may or may not be understood  
        by PAA. If PAA does not understand the credentials, it needs to  
        communicate with the AS in a different domain to verify the  
        credentials. The threats in the communication path between PAA  
        and AS are already covered in [RAD-EAP]. To counter these  
        threats, the communication between PAA and AS are secured using  
        a static or dynamic security association.  
  
  
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     2) PAA and EP: PAA and EP belong to the same administrative domain.  
        Hence, the network operator can setup a security association to  
        protect the traffic exchanged between them. This document  
        discusses the threats in this path.  
  
     3) PaC and AS: PaC and AS belong to the same administrative domain  
        and share a trust relationship. When PaC uses a different domain  
        than its home for network access, it provides its credentials to  
        the PAA in the visited network for authentication. The  
        information provided by PaC traverses the PaC-PAA path and    
        PAA-AS path. The threats in PAA-AS path are already discussed in  
        [RAD-EAP]. This document discusses the threats in PaC-PAA path.  
  
   It is possible that some of the entities like PAA, AS and EP are    
   co-located. In those cases, it can be safely assumed that there are  
   no significant external threats.  
  
   The entities that do not have any trust relationship before PANA  
   begins are as follows.  
     
     1) PaC and PAA: PaC and PAA normally belong to two different  
        administrative domains. They do not necessarily share a trust  
        relationship initially. They establish a security association in  
        the process of authentication. All messages exchanged between  
        PaC and PAA are subject to various threats, which are discussed  
        in this document.  
  
     2) PaC and EP: EP belongs to the same administrative domain as PAA  
        and hence PaC and EP do not necessarily share a trust  
        relationship initially. When PaC is successfully authenticated,  
        it may result in key establishment between PaC and PAA, which  
        can be further used to secure the link between PaC and EP. For  
        example, EAP keying framework [EAP-KEY], defines a three party  
        EAP exchange where the clients derive the transient sessions  
        keys to secure the link between the peer and NAS in their final  
        step. Similarly, PANA will provide the ability to establish keys  
        between PaC and EP that can be used to secure the link further.  
        This is further discussed in section 6.4 below.  
     
6.0 Threat Scenarios  
     
   The PANA authentication client (PaC) needs to discover the PAA first.  
   This involves either sending solicitations or waiting for  
   advertisements. Once it has discovered the PAA, it will lead to  
   authentication exchange with PAA. Once the access is granted, PaC  
   will most likely exchange data with other nodes in the Internet. All  
   of these are vulnerable to denial of service (DoS), man-in-the-middle  
   (MITM) and service theft attacks.  
  
  
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   The threats are grouped by the various stages the client goes through  
   to gain access to the network. Section 6.1 discusses the threats  
   related to PAA discovery. Section 6.2 discusses the threats related  
   to authentication itself. Section 6.3 discusses the threats involved  
   while leaving the network. Section 6.4 discusses service theft.  
   Section 6.5 discusses the threats in PAA-EP path. Section 6.6  
   discusses the miscellaneous threats.  
     
   Some of the threats discussed in the following sections may be  
   specific to shared links. The threat may be absent on non-shared  
   links. Hence, it is only required to prevent the threat on shared  
   links. Instead of specifying a separate set of requirements for  
   shared links and non-shared links, this document just specifies one  
   set of requirements with the following wording: "PANA MUST be able to  
   prevent threat X". This means that the PANA protocol should be  
   capable of preventing threat X. The feature that prevents threat X  
   may or may not be used depending on the deployment.  
  
6.1 PAA Discovery  
  
   PaC is in the process of discovering the PAA. The PAA is discovered  
   by sending solicitations or receiving advertisements. Following are  
   the possible threats.  
     
   T6.1.1: A malicious node can pretend to be a PAA by sending a spoofed  
   advertisement.  
  
   In existing dial-up networks, the clients authenticate to the network  
   but generally do not verify the authenticity of the messages coming  
   from Network Access Server (NAS). This mostly works because the link  
   between the device and the NAS is not shared with other nodes  
   (assuming that nobody tampers with the physical link), and clients  
   trust the NAS and the phone network to provide the service. Spoofing  
   attacks are not present in this environment because the PaC may  
   assume that the other end of the link is the PAA.  
     
   In environments where the link is shared, this threat is present as  
   any node can pretend to be a PAA. Even if the nodes are authenticated  
   at layer 2, this threat is present. It is difficult to protect the  
   discovery process, as there is no a priori trust relationship between  
   PAA and PaC. It might be possible for the EP to filter out the  
   packets coming from PaC that resembles PAA packets and hence this  
   threat can be prevented in such environments.  
     
   The advertisement may be used to include other information like  
   supported authentication methods etc., besides the discovery of the  
   PAA itself. This can lead to a bidding down attack, as a malicious  
   node can send a spoofed advertisement with capabilities that indicate  
  
  
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   less secure authentication methods than what the real PAA supports,  
   thereby fooling the PaC into negotiating a less secure authentication  
   method than what would otherwise be available. This is best avoided  
   by limiting the amount of security-critical information sent during  
   the PAA discovery process.  
     
   Requirement 1  
     
   PANA MUST not assume that the discovery process is protected. Since,  
   it is difficult to protect the discovery process, the security-  
   critical information exchanged during the discovery process SHOULD be  
   limited.  
     
6.2 Authentication  
  
   This section discusses the threats specific to the authentication  
   protocol. Section 6.2.1 discusses the possible threat associated with  
   success/failure indications that are transmitted to PaC at the end of  
   the authentication. Section 6.2.2 discusses the man-in-the-middle  
   attack when compound methods are used. Section 6.2.3 discusses the  
   replay attack and section 6.2.4 discusses about the device identifier  
   attack.  
     
6.2.1 Success or Failure Indications  
  
   Some authentication protocols e.g., EAP, has a special message to  
   indicate success or failure. An attacker can send false  
   authentication success or failure message to the PaC. By sending  
   false failure message, the attacker can prevent the client from  
   accessing the network. By sending false success message, the attacker  
   can prematurely end the authentication exchange effectively denying  
   service for the PaC.  
     
   If the link is not shared, then this threat is absent as ingress  
   filtering can prevent the attacker from impersonating as the PAA.  
     
   If the link is shared, it is easy to spoof these packets. If layer 2  
   provides per-packet encryption with pair-wise keys, it might make it  
   hard for the attacker to guess the success or failure packet that the  
   client would accept. Even if the node is already authenticated at  
   layer 2, it can still pretend to be a PAA and spoof the success or  
   failure.  
     
   This attack is possible if the success or failure indication is not  
   protected using a security association between PaC and PAA. In order  
   to avoid this attack, PaC and PAA should mutually authenticate each  
   other. In the process of mutually authenticating each other, they  
   should be able to establish keys to protect the success or failure  
   indications. It may not be possible to protect the success or failure  
  
  
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   indication always as the keys may not be established prior to  
   transmitting the success or failure packet. If the client is re- 
   authenticating to the network, it can use the previously established  
   security association to protect the success or failure indications.  
   Similarly, all PANA messages that are exchanged during the  
   authentication prior to key establishment may not be protected.  
     
   Requirement 2  
     
   PANA MUST be able to mutually authenticate PaC and PAA. PANA MUST be  
   able to establish keys between PaC and PAA to protect the PANA  
   messages.  
     
6.2.2 MITM attack  
     
   A malicious node can claim to be PAA to the real PaC and claim to be  
   PaC to the real PAA. This is a man in the middle (MITM) attack where  
   the PaC is fooled to think that it is communicating with real PAA and  
   the real PAA is fooled to think that it is communicating with real  
   PaC.  
     
   If the link is not shared, this threat is absent as ingress filtering  
   can prevent the attacker from acting as man in the middle.  
     
   If the link is shared, this threat is present. Even if the layer 2  
   provides per-packet protection, the attacker can act as man in the  
   middle and launch this attack. An instance of MITM attack, when  
   compound authentication methods are used is described in [TUN-EAP].  
   In these attacks, the server first authenticates to the client. As  
   the client has not proven its identity yet, the server acts as the  
   man-in-the-middle, tunneling the identity of the legitimate client to  
   gain access to the network. The attack is possible because there is  
   no verification that the same entities participated among the  
   compound methods. It is not possible to do such verification if  
   compound methods are used without being able to create cryptographic  
   binding among them. This implies that PANA will be vulnerable to such  
   attacks if compound methods are used without being able to  
   cryptographically bind them. Note that the attack does not exist if  
   the keys derived during the tunnel establishment are not used for  
   authenticating the client e.g., tunnel keys are used for just  
   protecting the identity of the client.  
     
   Requirement 3  
     
   When compound authentication methods are used in PANA, the methods  
   MUST be cryptographically bound.  
     
     
6.2.3 Replay Attack  
  
  
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   A malicious node can replay the messages that caused authentication  
   failure or success at a later time to create false failures or  
   success. The attacker can also potentially replay other messages of  
   the PANA protocol to deny service to the PaC.  
     
   If the link is not shared, this threat is absent as ingress filtering  
   can prevent the attacker from impersonating as PAA and replay the  
   packets.  
     
   If the link is shared, this threat is present. If the packets are  
   encrypted at layer 2 using pair-wise keys, it will make it hard for  
   the attacker to learn the unencrypted (i.e., original) packet that  
   needs to be replayed. Even if layer 2 provides replay protection, the  
   attacker can still replay the PANA messages (layer 3) for denying  
   service to the client.  
     
   Requirement 4  
     
   PANA MUST be able to protect itself against replay attacks.  
     
6.2.4 Device Identifier Attack  
  
   When the client is successfully authenticated, PAA sends access  
   control information to EP for granting access to the network. The  
   access control information typically contains the device identifier  
   of the PaC, which is obtained from the IP headers and MAC headers of  
   the packets exchanged during the authentication process. The attacker  
   can gain unauthorized access into the network using the following  
   steps.  
     
     . An attacker pretends to be a PAA and sends advertisements. PaC  
        gets fooled and starts exchanging packets with the attacker.  
     . The attacker modifies the IP source address on the packet,  
        adjusts the UDP/TCP checksum and forwards the packet to the real  
        PAA. It does the same on return packets also.  
     . When the real PaC is successfully authenticated, the attacker  
        gains access to the network as the packets contained the IP  
        address (and potentially the MAC address also) of the attacker.  
     
   If the link is not shared, this threat is absent, as the attacker  
   cannot impersonate as PAA and intercept the packets from PaC.  
     
   If the link is shared, this threat is present. If the layer 2  
   provides per-packet protection, it is not possible to change the MAC  
   address and hence this threat may be absent in such cases if EP  
   filters both on IP and MAC address.  
     
   Requirement 5  
  
  
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   PANA MUST be able to protect the device identifier against spoofing  
   when it is exchanged between the PaC and PAA.  
     
     
6.3 PaC leaving the network  
     
   When the PaC leaves the network, it can inform the PAA before  
   disconnecting from the network so that the resources used by PaC can  
   be accounted properly. PAA may also choose to revoke the access any  
   time if it deems necessary. Following are the possible threats.    
     
   T6.3.1: A malicious node can pretend to be a PAA and revoke the  
   access to PaC.  
     
   T6.3.2: A malicious node can pretend to be a real PaC and transmit a  
   disconnect message.  
     
   T6.3.3: PaC can leave the network without notifying the PAA or EP  
   e.g., the Ethernet cable is unplugged, system crash. An attacker can  
   pretend to be the PaC and start using the network.  
     
   If the link is not shared, threats T6.3.1 and T6.3.2 are absent.  
   Threat T6.3.3 may still be present. If there is no layer 2 indication  
   or the layer 2 indication cannot be relied up on, then the threat  
   T6.3.3 is still present on non-shared links.  
     
   If the link is shared, all of the above threats are present as any  
   node on the link can spoof the disconnect message. Even if the layer  
   2 has per-packet authentication, the attacker can pretend to be a PaC  
   e.g. by spoofing the IP address, and disconnect from the network.  
   Similarly, any node can pretend to be a PAA and revoke the access to  
   the PaC. Hence, T6.3.1 and T6.3.2 are possible even on links where  
   layer 2 is secured. Threat T6.3.3 can be prevented if layer 2  
   provides per-packet authentication. The attacker cannot subsume the  
   PaC that left the network without knowing the keys that protect the  
   packet at layer 2.  
     
   In some link layers, e.g., 802.11 [IEEE-802.11], disassociate and   
   de-authenticate messages are not protected (even with [IEEE- 
   802.11i]). In such link layers, protecting PANA messages may not be  
   very useful as the attacker can attack using the link layer  
   mechanisms rather than PANA.   
     
   Requirement 6  
     
   PANA MUST be able to protect disconnect and revocation messages. PANA  
   MUST NOT depend on PaC sending a disconnect message.  
     
  
  
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6.4 Service theft  
     
   An attacker can gain unauthorized access into the network by stealing  
   the service from another client. Once the PaC is successfully  
   authenticated, EP will have filters in place to prevent unauthorized  
   access into the network. The filters will be based on something that  
   will be carried on every packet. For example, the filter could be  
   based on IP and MAC address where the packets will be dropped unless  
   the packets coming with certain IP address match the MAC address  
   also. Following are the possible threats.  
     
   T6.4.1: Attacker can spoof both the IP and MAC address of an  
   authorized client to gain unauthorized access. Attacker can launch  
   this attack easily by just sniffing the wire for IP and MAC address.  
   This lets the attacker use the network without any authorization,  
   getting a free service.  
     
   If the link is not shared, this threat is absent as ingress filtering  
   can prevent one node from impersonating as another node.  
     
   If the link is shared, this threat is present. If layer 2 provides  
   per-packet protection using pair-wise keys, it can prevent the  
   attacker from gaining unauthorized access.  
     
   PANA MUST be able to prevent service theft. In some cases e.g. non- 
   shared links, it is sufficient to provide access control information  
   like IP address, MAC address, etc., to EP, which in turn can prevent  
   unauthorized users from gaining access to the network by policing the  
   packets for matching addresses. In the case of shared links, this  
   information is not sufficient to prevent service theft. PANA MUST be  
   able to bootstrap a shared secret between the PaC and PAA which can  
   be further used to setup a security association (e.g., IPsec) between  
   PaC and EP to prevent service theft on shared links.   
     
   Requirement 7  
     
   PANA MUST securely bind the authenticated session to the device  
   identifier of the client, to prevent service theft. PANA MUST be able  
   to bootstrap a shared secret between the PaC and PAA which can be  
   further used to setup a security association between PaC and EP to  
   provide cryptographic protection against service theft on shared  
   links.  
     
6.5 PAA-EP communication  
     
   After a successful authentication, PAA needs to communicate the  
   access control information of the PaC to EP so that PaC will be  
   allowed to access the network. The information communicated would  
  
  
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   contain at least the device identifier of the PaC. If strong security  
   is needed, PAA will communicate a shared secret known only to PaC and  
   PAA, for setting up a security association between PaC and EP.  
   Following are the possible threats.  
     
   T6.5.1: Attacker can eavesdrop to learn the information communicated  
   between PAA and EP. The attacker can further use this information to  
   spoof the real PaC and also setup an security association for gaining  
   access to the network. This threat is absent, if the attacker cannot  
   eavesdrop the link e.g., PAA and EP are communicating on a separate  
   link from that of visiting PaCs.  
     
   T6.5.2: Attacker can pretend to be PAA and send false information to  
   EP for gaining access to the network. The attacker has to send its  
   own device identifier and also a shared secret in the case of  
   stronger security so that EP will let the attacker access the  
   network.  
     
   If the communication between PAA and EP is protected, these threats  
   are absent.  
     
   Requirement 8  
     
   The communication between PAA and EP MUST be protected against  
   eavesdropping and spoofing attacks.   
     
6.6 Miscellaneous attacks  
     
   T6.5.1: There are various forms of DoS attacks that can be launched  
   on the PAA or AS. A few are mentioned below. As it is hard to defend  
   against some of the DoS attacks, the protocol should be designed  
   carefully to mitigate or prevent such attacks.  
  
     . Attacker can bombard the PAA with lots of authentication  
        requests. If PAA and AS are not collocated, PAA may have to  
        allocate resources to store some state about PaC locally before  
        it receives the response from the backend AS. This can deplete  
        memory resources on PAA.  
     . The attacker can force the PAA or AS to make computationally  
        intensive operations with minimal effort, that can deplete the  
        CPU resources of the PAA or AS.  
     
   T6.5.2: PaC acquires IP address before PANA authentication begins  
   using methods like e.g., DHCP in IPv4 and auto-configuration in IPv6  
   [PANAREQ]. If IP addresses are assigned before authentication, it  
   opens up the possibility of DoS attack where malicious nodes can  
   deplete the IP addresses by assigning multiple IP addresses. If  
   stateless auto-configuration [ADDRCONF] is used, the attacker can  
   respond to duplicate address detection probes sent by any node on the  
  
  
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   network effectively not allowing the node to configure a link local  
   address. If stateful mechanism is used in IPv6 e.g., DHCPv6, then  
   this attack is still possible. Address depletion attack is not  
   specific to PANA, but a known attack in DHCP [DHCP-AUTH]. If PANA  
   assumes that the client has an IP address already, it opens up the  
   network to the DoS attack.  
     
   Requirement 9  
     
   PANA SHOULD not assume that the PaC has acquired an IP address before  
   PANA begins.   
     
     
7.0 Summary of Requirements  
  
        1. PANA MUST not assume that the discovery process is protected.  
          Since, it is difficult to protect the discovery process, the  
          security-critical information exchanged during the discovery  
          process SHOULD be limited.  
     
        2. PANA MUST be able to mutually authenticate PaC and PAA. PANA  
          MUST be able to establish keys between PaC and PAA to protect  
          the PANA messages.  
  
        3. When compound authentication methods are used in PANA, the  
          methods MUST be cryptographically bound.  
  
        4. PANA MUST be able to protect itself against replay attacks.  
  
        5. PANA MUST be able to protect the device identifier against  
          spoofing when it is exchanged between the PaC and PAA.  
  
        6. PANA MUST be able to protect disconnect and revocation  
          messages. PANA MUST NOT depend on PaC sending a disconnect  
          message.  
  
        7. PANA MUST securely bind the authenticated session to the  
          device identifier of the client, to prevent service theft.  
          PANA MUST be able to bootstrap a shared secret between the  
          PaC and PAA which can be further used to setup a security  
          association between PaC and EP to provide cryptographic  
          protection against service theft on shared links.  
  
        8. The communication between PAA and EP MUST be protected  
          against eavesdropping and spoofing attacks.  
  
        9. PANA SHOULD not assume that the PaC has acquired an IP  
          address before PANA begins.  

  
  
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8.0 Security Considerations  
     
   This document discusses various threats with IP based network access  
   protocol.  
  
9.0 Normative References  
     
   [PANAUS] Y. Ohba et. al, "Problem Space and Usage Scenarios for  
   PANA", draft-ietf-pana-usage-scenarios-03.txt   
     
   [KEYWORDS] S. Bradner, "Key words for use in RFCS to indicate  
   requirement levels", RFC 2119, March 1997.  
     
10.0 Informative References  
     
   [PANAREQ] A. Yegin et al., "Protocol for Carrying Authentication for  
   Network Access (PANA) Requirements and Terminology", draft-ietf-pana- 
   requirements-04.txt  
     
   [RADIUS] C. Rigney et. al, "Remote Authentication Dial In User  
   Service", RFC2865, June 2000.  
          
   [EAP-KEY] B. Aboba et. al, "EAP keying framework", draft- aboba- 
   pppext-key-problem-06.txt     
          
   [ADDRCONF] S. Thomson et. al, "IPv6 Stateless Address  
   Autoconfiguration", RFC2462, December 1998.    
          
   [DHCP-AUTH] R. Droms, et. al "Authentication for DHCP messages",   
   RFC3118, June 2001.    
       
   [RAD-EAP] B. Aboba, et. al, "Radius support for Extensible  
   authentication protocol", draft-aboba-radius-rfc2869bis-21.txt    
          
   [TUN-EAP] J. Puthenkulam et. al, "The compound authentication   
   binding problem", draft-puthenkulam-eap-binding-02.txt    
          
   [IPSEC] S. Kent et. al, "Security architecture for the Internet   
   Protocol", RFC 2401, November 1998.  
          
   [IEEE-802.11i] Institute of Electrical and Electronics Engineers  
   "Unapproved Draft Supplement to Standard for Telecommunications and  
   Information Exchange Between systems - LAN/MAN Specific Requirements  
   - Part 11: Wireless LAN Medium Access Control (MAC) and Physical  
   Layer (PHY) Specifications: Specification for Enhanced Security",  
   IEEE Draft 802.11i (work in progress), 2003.  
     

  
  
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   [IEEE-802.11] Institute of Electrical and Electronics Engineers,   
   "Information Technology - Telecommunications and Information Exchange  
   between Systems - Local and Metropolitan Area Network - Specific  
   Requirements - Part 11: Wireless LAN Medium Access  Control (MAC) and  
   Physical Layer (PHY) Specifications", IEEE Standard 802.11, 1999.  
     
11.0 Acknowledgments  
     
   The author would like to thank the following people (in no specific  
   order) for providing valuable comments: Alper Yegin, Basavaraj Patil,  
   Pekka Nikander, Bernard Aboba, Francis Dupont, Michael Thomas,  
   Yoshihiro Ohba, Gabriel Montenegro, Tschofenig Hannes, Bill  
   Sommerfeld, N. Asokan, Pete McCan and Derek Atkins.  
  
12.0 Revision Log  
     
   Changes between 03 and 04  
     
   -Added a new requirement for the disconnect notification.  
   -Trust relationship section was rewritten.  
   -Device identifier attack requirements was rewritten.  
   -Service theft requirement was rewritten.  
   -Added a new section for PAA-EP threats.  
  
   Changes between revision 02 and 03  
     
  -Changed Requirement 1 to include text about weak authentication             
  suites.  
  -Rearranged the order of definitions in terminology section.  
  -Removed some confusing text with respect to IPsec from the Service  
  theft section.  
       
   Changes between revision 01 and 02  
     
  -Renamed the section "Assumptions" to "Trust relationships" and added  
  more text to clarify the relationship between PaC and EP.  
  -Added more text for threats in PAA – AS path.  
  -Merged the "Type of Attacks" section into "Threat Scenarios"  
  -Removed the requirement on DoS attack.  
  -Reworded most of the requirements.  
    
  Changes between revision 00 and 01  
          
  -Removed unused terms from section 3.0.  
  -Removed identity protection as a threat after feedback from Atlanta  
  IETF55 meeting.  
  -Renamed the section "Attacks on Normal Data communication" to  
  "Service theft". Removed confidentiality as a requirement from that  
  section.  
  
  
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  -Added a new threat "Device Identifier attack".  
  
13.0 Author's Address  
     
   Mohan Parthasarathy  
   Tahoe Networks  
   3052 Orchard Drive  
   San Jose, CA 95134  
     
   Phone: 408-944-8220  
   Email: mohanp@tahoenetworks.com  
  
14.0 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 18:49:42