[Nea] rev-00 of the Requirements draft
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[Nea] rev-00 of the Requirements draft



Hi All,

 

Here is the -00 rev of the Requirements draft that the Requirements team has produced in just a couple of weeks. It has been submitted to the IETF.

 

I would like to thank everyone on the Requirements team for their extraordinary effort in pulling this through in a short period of time!

 

The team will continue working on this draft and we plan to submit rev-01 of this draft by June 26th.

 

Comments from the mailing list are welcome!

 

Regards

Hormuzd

 

  Internet Draft                            Hormuzd Khosravi, Intel 
  Expires: November 2006                    Paul Sangster, Symantec          
                                         
  Working Group: NEA                               May 2006 
                                                  
   
   
   
                 Requirements for Network Endpoint Access (NEA) 
                    draft-khosravi-nea-requirements-00.txt 
   
   
   
  Status of this Memo 
    
   By submitting this Internet-Draft, each author represents that any 
   applicable patent or other IPR claims of which he or she is aware 
   have been or will be disclosed, and any of which he or she becomes 
   aware will be disclosed, in accordance with Section 6 of BCP 79. 
       
   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups.  Note that 
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   Internet-Drafts are draft documents valid for a maximum of six 
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   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 (2006). 
    
  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]. 
    
  Abstract 
    
   This document defines the interface requirements between the 
   components of the NEA (Network Endpoint Assessment) conceptual 
   architecture.  NEA provides owners of networks (e.g. an enterprise 



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Internet Draft             NEA Requirements                 May 2006 
   offering remote access) a mechanism to learn the operational state 
   or posture of a system requesting network access and then apply this 
   knowledge to the network admission decision.  In this case, 
   operational posture refers to information about the configuration 
   and use of hardware and software capabilities available or running 
   on the system.  This information is frequently useful for detecting 
   systems that are lacking (or have out of date) security protective 
   mechanisms (e.g. anti-virus, firewall.) 
 
   In order to provide context for the requirements, a conceptual 
   architecture and terminology is introduced.  This architecture is 
   provided for informational purposes but is based on the models used 
   by NAC[9], NAP[10] and TNC[8]. 
 
  Authors 
    
   The participants in the NEA Requirements Team who were instrumental 
   in the creation of this requirements draft are:  
    
   Kevin_Amorin, Diana Arroyo, Uri Blumenthal, Steve Hanna, Thomas 
   Hardjono, Hormuzd Khosravi, Ravi Sahita, Mauricio Sanchez, Paul 
   Sangster, Jeff Six, Joseph Tardo, Susan Thompson, John Vollbrecht, 
   Hao Zhou  
 
 
   1. Introduction....................................................2 
   2. Definitions.....................................................3 
   3. Architecture and Components.....................................4 
   4. Common Architectural Requirements...............................4 
   5. Interface Requirements..........................................5 
 5.1. Posture Attribute (PA) interface Requirements...................5 
 5.2. Posture Broker (PB) Interface Requirements......................6 
 5.3. Posture Transport (PT)Interface Requirements....................8 
   6. Security Analysis/Requirements..................................9 
   7. Operational Considerations.....................................10 
   8. Security Considerations........................................11 
 8.1. Scope and Overlap..............................................11 
 8.2. Interesting Attack Classes.....................................12 
  8.2.1. Man-in-the-Middle (MITM)....................................12 
  8.2.2. Message Modification........................................13 
  8.2.3. Message Replay or Theft.....................................13 
   9. References.....................................................14 
 9.1. Normative References...........................................14 
 9.2. Informative References.........................................14 
   Authors' Addresses & Acknowledgments..............................15
    
 1.Introduction 
    



  
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   Today, most network providers can leverage existing standards-based 
   technologies to restrict access to the network based upon the 
   requesting system's user or host-based identity, source IP address 
   or physical access point.  However these approaches still leave the 
   network prone to malware-based attack, when an authorized but 
   infected system is admitted and the malware is able to spread 
   throughout the internal network. 
    
   As a result, network operators need the ability to preemptively 
   detect systems that are prone or already contain malware potentially 
   dangerous to the network.  If a system is determined to be prone to 
   attack by lacking proper defensive mechanisms such as the absence of 
   up to date firewall and anti-virus software, there should be a way 
   to safely repair (remediate) the system so that it can be 
   subsequently trusted to join and operate on the network. 
    
   The Network Endpoint Assessment (NEA) system is a complementary 
   technology to existing authentication and authorization approaches 
   allowing the network to have visibility into the contents of the 
   system (security posture) requesting access so that its risk profile 
   can be factored into the admission decision.  NEA typically involves 
   the use of trusted agents running on the requesting machine which 
   observe and report on the posture of the system to network 
   infrastructure.  The infrastructure has equivalent components which 
   are capable of evaluating the posture information and feeding the 
   result to an appropriate network admission decision maker.  Finally 
   the admission decision is provisioned to the enforcement mechanisms 
   on the network and/or system requesting access.  The decision might 
   allow for no access, limited access (possibly to allow for 
   remediation), or full access to the network. 
    
   Architectures, similar to NEA, have been defined in the industry 
   (e.g. TNC, NAP, NAC) to assess the software or hardware 
   configuration of endpoint devices for the purposes of monitoring or 
   enforcing compliance of endpoints to an organization's policy on 
   access to the network. These architectures are not interoperable 
   since most of the technologies used to implement the architecture 
   are not standards. 
    
   The NEA working group is working on defining standard interface 
   protocols so as to enable interoperability between devices from 
   different vendors allowing network owners to deploy truly 
   heterogeneous solutions. This document describes the requirements 
   for NEA candidate technologies and protocols.  
 
 2.Definitions 
    
   Please refer to [3] for the NEA terminology.   
 


  
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 3.Architecture and Components 
    
   The major components of NEA architecture are as follows. 
    
     |-------------|                          |----------------| 
     | Posture     |  <--------PA--------->   |   Posture      | 
     | Collectors  |                          |   Validators   | 
     | (1 ...N)    |                          |   (1 ...N)     | 
     |-------------|                          |----------------| 
           |                                          | 
           |                                         PV 
           |                                          | 
     |-------------|                          |----------------| 
     |   Client    |  <--------PB--------->   |     Server     | 
     |   Broker    |                          |     Broker     | 
     |--------- ---|                          |----------------| 
           |                                          | 
           |                                          | 
     |-------------|  <--------PT--------->   |----------------| 
     |             |                          |                | 
     | Network     |    |--------|            |   Network      | 
     | Access      |----|Network |------------|   Access       | 
     | Requestor   |    |Enforcer| <---NAE--> |   Authority    | 
     |-------------|    |--------|            |----------------| 
 
       NEA CLIENT                                  NEA SERVER 
 
 
              Figure 1: NEA Components and Interfaces 
    
 4.Common Architectural Requirements 
    
   The following are the common architectural requirements across all 
   NEA interfaces/protocols: 
    
   1. NEA protocols MUST be capable of performing a multi-round posture 
   exchange between the client (agent) and server.  This enables the 
   server to request additional information or updates to the posture 
   data already reported. The updates allow for detection of recent 
   changes in the client state (e.g. possibly due to a remediation.) 
    
   2. NEA protocols MUST allow the NEA server to initiate requests for 
   posture information prior to network access and at any time after 
   the client has established an identity on the network (e.g. IP 
   address.)  This enables the NEA server to evaluate posture prior to 
   allowing access and to periodically re-validate systems already 
   admitted to the network to assure they are still in compliance with 
   the current policies. 
    
   3. NEA protocols MUST provide a way for the NEA client to initiate a 
   posture re-evaluation request as needed.  This allows the client to 


  
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   proactively request a posture re-evaluation by the NEA Server after 
   detection of a potentially suspicious event. 
     
   4. NEA protocols MUST provide protection against active and passive 
   attacks by intermediaries (e.g. man-in-the-middle.)  Such protection 
   might come from a strong (e.g. cryptographic) binding between the 
   authenticated identity of the requesting system and the reported 
   posture information.  This protection MUST prevent replay based 
   attacks (preventing a malicious machine from later replaying a 
   healthy posture report.) 
    
   5. The PA, PB & PV interfaces defined by NEA MUST be agnostic of the 
   transport i.e. PT interface. For example, the PB protocol must 
   provide a transport (PT) independent interface allowing the PA 
   protocol to operate without change across a variety of network 
   protocol environments (e.g. EAP/802.1X, PANA, and IKE/IPsec.)  
    
   6. NEA protocols MUST reuse existing open standards for its 
   interfaces before defining new ones. 
    
   7. NEA protocols MUST be highly scalable in terms of adding multiple 
   servers, clients, Posture Collectors, Posture Validators, etc.  
    
    
 5.Interface Requirements 
    
5.1.Posture Attribute (PA) interface Requirements 
    
   The PA protocol defines the control and data model to carry posture 
   and validation information between a particular Posture Collector 
   associated with a NEA client and a Posture Validator associated with 
   a NEA Server. The Posture Attribute protocol consists of core 
   attributes and vendor defined attributes. The PA protocol will be 
   carried inside the Posture Broker (PB) protocol. 
    
   1. The PA protocol MUST support transport of the required (core) 
   attributes defined in the data model to report information received 
   by a Posture Collector. Examples of core attributes include Vendor 
   id, Application version, and Operational status. 
    
   2. The PA protocol MUST support the transport of vendor defined 
   attributes. 
    
   3. The PA protocol MUST support the transport of core (required) 
   attributes between a Posture Collector and a Posture Validator. 
   Example of such control messages are timestamp, transaction id, 
   reset, (re)start evaluation, validation results and (re)start 
   remediation. 
    


  
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   4. The PA protocol MAY support control attributes that group sub 
   attributes for a collector, for example, attributes that report 
   health of all sub-components including vendor, application, version, 
   and operational status. 
    
   5. The PA protocol MUST use open standards as far as possible for 
   example, structured formats such as XML. 
    
   6. The PA protocol SHOULD support expression of core attributes to 
   describe remediation state of components for example, last update 
   time, remediation server used. These attributes are used after 
   remediation so that a Posture Validator can synchronize with a 
   Posture Collector and continue remediation. 
    
   7. The PA protocol SHOULD support returning validation and 
   remediation parameters from a Posture Validator to a Posture 
   Collector, for example, remediation server URL.  
    
   8. The PA protocol MUST support authentication, integrity and 
   confidentiality of attributes sent between a Posture Collector and 
   Validator. Deployers of Posture Collectors and Posture Validators 
   should use at least authentication and integrity protection for 
   their messages, and may also employ confidentiality protection if 
   necessary for their environment. 
    
   9. The PA protocol SHOULD optimize transport of messages and 
   minimize Posture Broker protocol round trips. To achieve this, the 
   PA protocol should support configuration/negotiation of the maximum 
   size and timeout period for interaction of a Posture Collector with 
   a Posture Validator. 
    
     
5.2.Posture Broker (PB) Interface Requirements 
    
   The PB protocol supports multiplexing of Posture Attributes (based 
   on PA protocol) from multiple Posture Collectors associated with a 
   NEA client and de-multiplexing these messages to multiple Posture 
   Validators associated with a NEA server. The PB protocol supports 
   multiplexing of posture assessment results from multiple Posture 
   Validators associated with a NEA server and de-multiplexing results 
   to multiple Posture Collectors associated with a NEA client. The PB 
   protocol also aggregates remediation attributes from one or more 
   Posture Validators. 
    
   1. The PB protocol SHOULD allow carrying decisions identified as 
   global decisions from the NEA server along with Posture Validator 
   specific information reported by multiple Posture Validators. 
    




  
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   2. The PB protocol MUST contain information used by the Brokers to 
   route messages between particular types of Posture Collectors and 
   Posture Validators. Such message routing information should support 
   dynamic (de)registration of Posture Collectors and Validators 
   receive appropriate messages.  For example, a dynamically registered 
   Anti-Virus Posture Validator should be able subscribe to receive 
   messages from its peer Anti-Virus Posture Collector. 
    
   3. The PB protocol MUST support subscription messages on the NEA 
   server so that Posture Validators can receive asynchronous 
   information from Posture Collectors, for example, events or posture 
   attributes. 
    
   4. The PB protocol MUST support subscription messages on the NEA 
   client so that Posture Collectors can receive asynchronous 
   information from Posture Validators, for example, validation 
   reports. 
    
   5. The PB protocol MUST support multiple rounds of posture 
   collection within a transaction between a Posture Collector and a 
   Posture Validator. 
    
   6. The PB protocol MUST support asynchronous pull of posture 
   information from Posture Collectors on an event from a Posture 
   Validators or a NEA server. The NEA server may override the pull 
   request of a Posture Validator. 
    
   7. The PB protocol MUST support ranking/priority ordering of Posture 
   Collector reports and Posture Validator reports to resolve conflicts 
   or dependency issues at the NEA client and/or NEA server. 
    
   8. The PB protocol MUST support reporting of error codes and sub-
   codes back to the NEA client, for example, to avoid multiplexing 
   attributes for a misbehaving Posture Collector or to repeat the 
   attributes for a specific Posture Collector only.  
    
   9. The PB protocol MUST support authentication, integrity and 
   confidentiality of multiplexed Posture attributes and Validation 
   attributes. Implementers of Posture Brokers should use 
   authentication and integrity of messages, and may support 
   confidentiality of messages. 
    
   10. The PB protocol SHOULD support grouping of attributes to 
   optimize transport of messages and minimize round trips. The PB 
   protocol should support configuration/negotiation of the maximum 
   size and timeout period for interaction between a NEA server and 
   client. 
    
     



  
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5.3.Posture Transport (PT) Interface Requirements 
    
   The PT is the transport protocol between the Network Access 
   Requestor (NAR) in the NEA Client and the Network Access Authority 
   (NAA) within the NEA Server present on the network owner?s 
   infrastructure.  PT is responsible for providing a protected 
   transport (frequently using a tunnel) for the PB protocol. The PT 
   protocol may in turn be transported by a lower layer protocol such 
   as: 802.1x, RADIUS, TLS, IKE/IPsec or TCP,UDP/IP.  This section 
   defines the requirements which candidate PT protocols must be 
   capable of supporting.  The deployer?s policy will dictate how these 
   apply to a particular environment. 
    
   1. The PT protocol SHOULD use existing standard based protocols 
   whenever possible.  If no standard exists to support the target use 
   cases, NEA WG will request appropriate standards groups develop 
   necessary standard protocols. 
    
   2. The PT protocol SHOULD incur low overhead to accommodate for use 
   on low bandwidth links. 
    
   3. The PT protocol SHOULD be capable of supporting a half duplex 
   communication environment. 
    
   4. The PT protocol MUST NOT attempt to interpret the contents of the 
   PB messages being transported, i.e. the data it is carrying must be 
   opaque to it. 
    
   5. The PT protocol MUST be capable of protecting the integrity and 
   confidentiality of the PB messages being transported between the NAR 
   and NAA. 
      
   6. The PT protocol MUST provide reliable delivery of PB messages.  
   This includes the ability to perform fragmentation, detect 
   duplicates, and reorder data, if necessary.    
    
   7. The PT protocol MUST be capable of supporting mutual 
   authentication of the communicating parties.  This MAY occur by 
   initially authenticating the NEA Server and leveraging byproducts 
   (e.g. keys) associated with this authentication to construct a 
   confidential channel where the NEA Client can authenticate.   
    
   8. The PT protocol MUST be able to establish a restricted session 
   between the NAR and the NAA prior to the NAR granting general 
   network access. 
    
   9. The PT protocol MUST allow the NAR or NAA to initiate the 
   establishment of a restricted session for use by NEA when both 
   parties have necessary network addresses established. 



  
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 6.Security Analysis/Requirements 
   There are several entities that comprise the described NEA 
   conceptual architecture. From security viewpoint, their relations 
   and communications should adhere to the following requirements. 
    
   End-points must be able to authenticate their peers (i.e. Posture 
   Collector and Posture Validator), for without that no meaningful 
   posture information exchange is possible. 
    
   1. PA interface 
       - Posture Validator MUST be able to ascertain that the traffic 
   (posture) it received is "fresh". This freshness prevents a third 
   party from replaying the posture information produced by an earlier 
   Posture Collector use without detection. 
       - It may be necessary (especially in case of multiple exchanges 
   between Posture Collector and Posture Validator) that Posture 
   Collector "recognizes" and trusts the given Posture Validator. This 
   ensures that Posture Collector is doing work on behalf of authentic 
   Posture Validator. 
    
   2. PB interface 
       - Communications between Client Broker and Server Broker MAY 
   need to be protected at least from active attacker (integrity, 
   confidentiality, timeliness). Integrity and timeliness are of the 
   utmost importance, to prevent third parties (any parties - including 
   Network Enforcer) from interfering with posture validation and 
   affecting PDP decisions. Confidentiality may be useful here, for 
   example to prevent attackers from determining which host would be 
   the most vulnerable target based on its posture information.   
   However there is privacy concern that the host should be able to 
   "see" what potentially privacy sensitive information about it is 
   being sent out.  This concern may prevent encryption from being used 
   or force a pre-screening of the posture information against a 
   privacy policy before allowing it to be sent over the network. 
    
   3. PT interface 
       - This communication channel MUST be protected: endpoint mutual 
   authentication with subsequent secure pipe establishment. Otherwise 
   third parties could launch a variety of attacks. 
    
   4. PV interface 
       - Communications between Server Broker and Posture Validators 
   SHOULD be protected because the Validators are likely running on 
   different systems on the network. Unless the Server Broker is able 
   to securely determine that each the Posture Validator is authentic 
   and authoritative, validation decisions could be forged and allow 
   bypassing the entire network access policy. 
    



  
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   5. Interfaces/communications between Posture Collector(s) and Client 
   Broker MAY need protection, especially if those are different 
   software entities. It is important that a Client Broker be allowed 
   to communicate with only the authorized Posture Collectors because 
   of the trust issue. Denial of Service is the most obvious threat 
   here. Forging a posture should not be feasible because of PA 
   interface. 
    
   6. Interface/communication between Client Broker and Network Access 
   Requestor MAY need protection. 
    
   7. Interface/communication between Server Broker and Network Access 
   Authority MAY be protected. 
 
 7.Operational Considerations 
    
   The NEA technology intends to address a major issue for owners of 
   networks by extending their existing ability to limit admission to 
   the network by inspection of the security posture of the system.  In 
   order to offer a solution to this issue, NEA needs to provide a 
   scalable solution addressing a vast majority of the systems deployed 
   while remaining manageable.  This introduces several issues which 
   should be considered during the definition of the protocols, 
   interfaces, architecture and their policies. 
    
   1. Some network devices (e.g. printers, legacy systems) will not 
   have support for NEA agents present.  In this situation, the NEA 
   server must be able to detect that the system requesting access is 
   incapable of responding to NEA protocols and thus will not be able 
   to report its security posture.  The NEA architecture should allow 
   for this event to be detected and reported to other components which 
   might be able to evaluate risk via other mechanisms (e.g. using 
   scanning techniques) and report back a suggested action. 
    
   2. Admission policy should be capable of being combined with 
   authentication policy so differentiated posture evaluation is 
   possible based on the identity and other factors about the 
   requesting system.  For example, in many cases customers may wish to 
   allow certain individuals (e.g. executives) to always be allowed 
   access to the network even if NEA detects a problem.  Similarly, 
   different posture checking profiles might be applied depending on 
   the requesting system or user?s identity. 
    
   3. Due to the potentially large number of systems offering and/or 
   evaluating posture information and the quantity of enforcement 
   devices, this presents a distributed policy issue for NEA deployers.  
   The NEA components should be manageable using data model definitions 
   associated within existing management protocol environments (e.g. 
   SNMP, CIM.) 



  
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   4. Because the NEA infrastructure is involved in making decisions 
   about every system?s request to join and remain on the network, NEA 
   deployments should have mechanisms that protect it from direct 
   attack or operational situations where it might be unavailable.  
   Highly available, distributed deployment architectures should help 
   minimize downtown and avoid single point of failure scenarios.  
   However NEA solutions may need to offer deployers some policy-driven 
   flexibility in how the NEA components respond when faced with an 
   unavailable NEA Server component. 
    
    
 8.Security Considerations 
    
   This document defines the requirements for the interfaces 
   (protocols) for a security mechanism assessment and enforcement 
   scheme.  As such, it does not define a specific solution or set of 
   technologies, so this section will highlight security issues that 
   may apply to NEA in general or to particular aspects of the eventual 
   technical architecture. 
    
 
8.1. Scope and Overlap 
    
   Inherent in the requirements is a desire for NEA candidate protocols 
   throughout the architecture to accommodate the use of strong 
   security mechanisms as dictated by the deployer.  In some cases, 
   these mechanisms may appear to provide overlapping protections.  The 
   overlaps may be desired by deployer to offer a defense in depth 
   approach; however because of the layering of the protocols each 
   mechanism offers slightly different protection benefits and levels 
   of granularity.  
    
   For example, a deployer may wish to encrypt traffic at the PT layer 
   to protect against some forms of traffic analysis or interception by 
   an eavesdropper. Additionally, the deployer may also selectively 
   encrypt a Posture Collector's set of reported attributes at the PA 
   layer to allow the peer Posture Verifier to achieve end to end 
   confidentiality.  In particular, this might be desired when the NEA 
   Server side decision point spans several systems so the NAA is on a 
   different system from the Verifier. 
    
   In general, the NEA architecture's protocols are intending to 
   provide to the Posture Collector the ability to safely send its 
   measurement attributes across an untrustworthy network to a peer 
   Posture Validator and receive protected requests/responses.  The 
   architecture is not intending to provide local integrity protection 
   for the proper operation of the Posture Collector itself.  For 
   example, NEA technologies do not claim to prevent a carefully 


  
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   crafted piece of malware (e.g. rootkit) from tricking the Posture 
   Collector into inaccurately reporting the state of the system so it 
   can remain undetected.  Such integrity protection of the Collector 
   and other aspects of the system might be offered by orthogonal 
   security mechanisms leveraging security hardware and/or protected 
   trusted software. 
    
   Different use cases and environments for the NEA technologies will 
   likely influence the selection of the strength and security 
   mechanisms employed during an assessment.  The goal of the NEA 
   requirements is to encourage the selection of technologies and 
   protocols that are capable of enforcing the necessary protections 
   for a wide variety of assessment use cases. 
    
8.2. Interesting Attack Classes 
    
   A variety of attacks are possible against current assessment 
   technologies. This section does not include a full threat analysis, 
   but wishes to highlight a few attacks which influenced the 
   requirement definition and should be considered by deployers 
   selecting use of protective mechanisms within the conceptual 
   architecture. 
    
   The following types of attacks are possible against each of the 
   network protocols defined in the conceptual architecture and thus 
   should be considered by deployers. 
    
8.2.1. Man-in-the-Middle (MITM) 
    
   MITM attacks against a network protocol exist when a 3rd party can 
   sit between two legitimate communicating parties without detection.  
   For example, a malware infested machine might wish to join the 
   network using measurements collected by a clean system by inserting 
   itself into and proxying an assessment message exchange. The impact 
   of the damage caused by the MITM can be limited or prevented by 
   selection of appropriate protective mechanisms. 
    
   The requirement for PT to be capable of supporting bi-directional 
   authentication prevents the attacker from inserting themselves as an 
   active participant (proxy) within the communications without 
   detection (assuming attacker lacks credentials convincing either 
   party it is legitimate.) Re-usable credentials should not be exposed 
   on the network to assure the MITM doesn't have a way to impersonate 
   either party. 
    
   However the MITM might still act as a message relay between the 
   parties and change, eavesdrop, or steal and replay the 
   communications.  These forms of attack require additional 
   protections discussed below. 



  
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8.2.2. Message Modification 
    
   Without message protection, an attacker capable of interception of 
   an assessment message would be capable of modifying the contents and 
   causing an incorrect action to occur.  For example, the attacker 
   might change the measurement attributes to always reflect incorrect 
   values and thus prevent a system from joining the network.  Unless 
   the NEA Server could detect this change, the attacker could prevent 
   network admission to large numbers of clean systems. Conversely, the 
   attacker could allow malware infested machine to be admitted by 
   changing the attributes. 
    
   In order to protect against such attacks, the PT includes a 
   requirement for strong integrity protection (e.g. including a 
   protected hash of the message) so this change will be detected.  PA 
   includes a similar requirement to enable end to end integrity 
   protection of the message.   
    
   It is important that integrity protection schemes leverage secret 
   information (not known by the attacker) that are bound to the 
   transaction such as an encrypted message hash or HMAC [REF] linked 
   to the authentication. Message hash keys from prior transactions 
   possibly involving other systems must not be re-usable without 
   detection. 
    
8.2.3. Message Replay or Theft 
    
   A passive attacker might listen to the network recording messages 
   from a healthy client for later re-use to the same NEA Server or 
   just to build an inventory of software running on other systems.  
   The NEA Server needs to be capable of detecting the replay or the 
   architecture must assure that the eavesdropper can not obtain the 
   attribute values in the first place. 
    
   The protection of the PT, PB or PA messages using encryption 
   prevents the passive listener from learning the exchanged attribute 
   values for theft or replay.  By linking the encrypted transaction to 
   the authentication event and leveraging a per-transaction freshness 
   exchange, this prevents a replay of the encrypted transaction. 
    
   As discussed, there are a variety of protective mechanisms included 
   in the requirements for candidate NEA protocols. Different use cases 
   and environments may cause deployers to decide not to use some of 
   these mechanisms; however this should be done with an understanding 
   that the architecture may become vulnerable to some classes of 
   attack.  As always a balance of risk vs. performance, usability, 
   manageability and other factors should be taken into account. 
    



  
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Internet Draft             NEA Requirements                 May 2006 
    
 9.References 
9.1.Normative References 
    
  1. S. Bradner, "The Internet Standards Process -Revision 3", RFC 2026, 
     October 1996.  
 
  2. S. Bradner, "Keywords for use in RFCs to Indicate Requirement 
     Levels", RFC2119 (BCP), IETF, March 1997. 
    
  3. S. Hanna, et. al., "Network Endpoint Assessment (NEA) Problem 
     Statement", draft-thomson-nea-problem-statement-01.txt, March 2006. 
 
  4.  Aboba,  B.,  Blunk,  L.,  Vollbrecht,  J.,  Carlson,  J.,  and  H. 
     Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748, 
     June 2004. 
 
  5. Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote 
     Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. 
 
  6. T.  Dierks,  E.  Rescorla, ??The Transport  Layer  Security  (TLS) 
     Protocol Version 1.1??, RFC 4346, April 2006. 
 
  7. S. Kent, R. Atkinson, ??Security Architecture for the Internet 
     Protocol??, RFC 2401, November 1998. (IPSec) 
 
    
9.2.Informative References 
    
  8. ??TCG Trusted Network Connect (TNC) Architecture for 
     Interoperability??, 
     https://www.trustedcomputinggroup.org/specs/TNC/TNC_Architecture_v1
     _1_r2.pdf, May 2006. 
 
  9. Cisco Network Admission Control (NAC), http://www.cisco.com/go/nac  
 
  10.  Microsoft Network Access Protection (NAP), 
     http://www.microsoft.com/technet/itsolutions/network/nap/default.ms
     px  
 
  11.  IEEE, "Local and Metropolitan Area Networks: Port-based Network 
     Access Control", 2004. (802.1x) 
 




  
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Internet Draft             NEA Requirements                 May 2006 
  12.  Forsberg, D., "Protocol for Carrying Authentication for Network 
     Access (PANA)", draft-ietf-pana-pana-11 (work in progress), March 
     2006. 
 
    
 Authors' Addresses & Acknowledgments 
    
   Hormuzd Khosravi (co-editor) 
   Intel 
   2111 NE 25th Avenue 
   Hillsboro, OR 97124 USA 
   Phone: +1 503 264 0334 
   Email: hormuzd.m.khosravi at intel.com 
    
   Paul Sangster (co-editor) 
   Symantec Corporation 
   6825 Citrine Dr 
   Carlsbad, CA 92009 USA 
   Email: paul_sangster at symantec.com 
    
   Kevin Amorin 
   Harvard University 
   79 JFK St. 
   Cambridge, MA 02138 
   Phone: +1 617-384-6699 
   Email: Kevin_Amorin at Harvard.edu 
    
   Diana Arroyo  
   IBM  
   11501 Burnet Road  
   Austin, Tx  78758  
   Phone: +1 512-838-0088  
   Email: darroyo at us.ibm.com 
    
   Uri Blumenthal 
   Intel Corporation 
   1515 Route 10, 
   Parsippany, NJ 07054 
   Phone: +1 973-967-6446 
   Email: uri.blumenthal at intel.com 
    
   Steve Hanna 
   Juniper Networks, Inc. 
   35 Forest Ridge Road 
   Concord, MA 01742 
   Phone: +1 978-371-3980 
   Email: shanna at juniper.net 
    
   Thomas Hardjono 


  
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Internet Draft             NEA Requirements                 May 2006 
   SignaCert, Inc. 
   707 SW Washington St./Suite 700,  
   Portland, OR 97205 
   Phone: +1 503-227-2207 
   Email: thardjono at signacert.com 
    
   Ravi Sahita 
   Intel Corporation 
   2111 NE 25th Ave 
   Hillsboro OR 97124 
   Email: Ravi.sahita at intel.com 
    
   Mauricio Sanchez 
   Email: mauricio.sanchez at hp.com 
    
   Jeff Six 
   Email: jeffsix at thematrix.ncsc.mil 
    
   Joseph Tardo 
   Nevis Networks 
   500 N. Bernardo Ave. 
   Mountain View, CA 94043 
   Email: joseph.tardo at nevisnetworks.com 
    
   Susan Thomson 
   Cisco Systems 
   499 Thornall Street, 8th floor 
   Edison, NJ  08837 
   U.S.A 
   Email: sethomso at cisco.com 
    
   John Vollbrecht 
   9682 Alice Hill Drive 
   Dexter, Mi. 48130 
   Email: jrv at merit.edu 
    
   Hao Zhou 
   Cisco Systems 
   4125 Highlander Parkway 
   Richfield, OH  44286 
   U.S.A. 
   Email: hzhou at cisco.com 
    
   Copyright Statement 
    
   Copyright (C) The Internet Society (2006).  This document is subject 
   to the rights, licenses and restrictions contained in BCP 78, and 
   except as set forth therein, the authors retain all their rights. 
    



  
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Internet Draft             NEA Requirements                 May 2006 
   This document and the information contained herein are provided on 
   an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE 
   REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE 
   INTERNET ENGINEERING TASK FORCE DISCLAIM 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. 
    
    











































  
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