Endpoint Compliance Profile
draft-ietf-sacm-ecp-00

SACM                                                           D. Haynes
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                     J. Fitzgerald-McKay
Expires: March 12, 2018                            Department of Defense
                                                             L. Lorenzin
                                                            Pulse Secure
                                                       September 8, 2017


                      Endpoint Compliance Profile
                         draft-ietf-sacm-ecp-00

Abstract

   This document specifies the Endpoint Compliance Profile, a high-level
   specification that describes a specific combination and application
   of IETF and TNC protocols and interfaces specifically designed to
   support ongoing assessment of endpoint posture and the controlled
   exposure of collected posture information to appropriate security
   applications.  This document is a subset of the Trusted Computing
   Group's Endpoint Compliance Profile Version 1.0 specification.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on March 12, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Preventative Posture Assessments  . . . . . . . . . . . .   4
     1.2.  Standardized Schema . . . . . . . . . . . . . . . . . . .   4
     1.3.  Secure Standardized Protocols . . . . . . . . . . . . . .   5
     1.4.  Keywords  . . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Endpoint Compliance Profile . . . . . . . . . . . . . . . . .   6
     3.1.  Posture Assessments . . . . . . . . . . . . . . . . . . .   7
     3.2.  Data Storage  . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Data Sharing  . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Purpose of the Endpoint Compliance Profile  . . . . . . .   7
     4.2.  Supported Use Cases . . . . . . . . . . . . . . . . . . .   8
       4.2.1.  Connected and Compliant . . . . . . . . . . . . . . .   8
       4.2.2.  Exposing Data to the Network  . . . . . . . . . . . .   9
         4.2.2.1.  Asset Management  . . . . . . . . . . . . . . . .  11
         4.2.2.2.  Vulnerability Searches  . . . . . . . . . . . . .  12
         4.2.2.3.  Threat Detection and Analysis . . . . . . . . . .  12
       4.2.3.  Non-supported Use Cases . . . . . . . . . . . . . . .  12
       4.2.4.  Profile Requirements  . . . . . . . . . . . . . . . .  13
       4.2.5.  Assumptions . . . . . . . . . . . . . . . . . . . . .  14
   5.  Endpoint Compliance Requirements  . . . . . . . . . . . . . .  16
     5.1.  Endpoint Pre-Provisioning . . . . . . . . . . . . . . . .  16
       5.1.1.  SWID Tags . . . . . . . . . . . . . . . . . . . . . .  17
       5.1.2.  Endpoint Identity and Machine Certificate . . . . . .  17
     5.2.  Posture Validators and Posture Collectors . . . . . . . .  17
       5.2.1.  SWID Posture Collectors and Posture Validators  . . .  18
         5.2.1.1.  The SWID Posture Collector  . . . . . . . . . . .  18
         5.2.1.2.  The SWID Posture Validator  . . . . . . . . . . .  18
     5.3.  NEA Client (NEAC) and NEA Server (NEAS) . . . . . . . . .  19
       5.3.1.  NEAC  . . . . . . . . . . . . . . . . . . . . . . . .  19
       5.3.2.  NEAS  . . . . . . . . . . . . . . . . . . . . . . . .  19
     5.4.  Repository  . . . . . . . . . . . . . . . . . . . . . . .  19
   6.  Posture Transport Client (PTC) and Posture Transport Server
       (PTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . .  20
   7.  Administrative Interface and API  . . . . . . . . . . . . . .  20
   8.  Endpoint Compliance Profile Examples  . . . . . . . . . . . .  21
     8.1.  Continuous Posture Assessment of an Endpoint  . . . . . .  21
       8.1.1.  Change on Endpoint Triggers Posture Assessment  . . .  21
     8.2.  Administrator Searches for Vulnerable Endpoints . . . . .  24



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   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  25
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  27
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  27
     11.1.  Security Benefits of Endpoint Compliance Profile . . . .  27
     11.2.  Threat Model . . . . . . . . . . . . . . . . . . . . . .  29
       11.2.1.  Endpoint Attacks . . . . . . . . . . . . . . . . . .  30
       11.2.2.  Network Attacks  . . . . . . . . . . . . . . . . . .  30
       11.2.3.  Server Attacks . . . . . . . . . . . . . . . . . . .  30
       11.2.4.  Repository Attacks . . . . . . . . . . . . . . . . .  31
     11.3.  Countermeasures  . . . . . . . . . . . . . . . . . . . .  31
       11.3.1.  Countermeasures for Endpoint Attacks . . . . . . . .  31
       11.3.2.  Countermeasures for Network Attacks  . . . . . . . .  32
       11.3.3.  Countermeasures for Server Attacks . . . . . . . . .  32
       11.3.4.  Countermeasures for Repository Attacks . . . . . . .  33
   12. Privacy-Considerations  . . . . . . . . . . . . . . . . . . .  34
   13. Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .  34
     13.1.  -00 to -01 . . . . . . . . . . . . . . . . . . . . . . .  34
     13.2.  -01 to -02 . . . . . . . . . . . . . . . . . . . . . . .  34
     13.3.  -02 to -00 . . . . . . . . . . . . . . . . . . . . . . .  34
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  35
     14.1.  Informative References . . . . . . . . . . . . . . . . .  35
     14.2.  Normative References . . . . . . . . . . . . . . . . . .  35
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  36

1.  Introduction

   The Endpoint Compliance Profile (ECP) builds on prior work from the
   IETF NEA WG, the Netmod WG, and the Trusted Network Communications
   (TNC) WG of the Trusted Computing Group [TNC], to standardize the
   collection, storage and sharing of posture information from network-
   connected endpointgs, including user endpoints, servers, and
   infrastructure.  The first generation of this specification focuses
   on reducing the security exposure of a network by enabling event-
   driven posture collection, as well as standardized querying for
   additional endpoint data as needed.  Standadrid collection improves
   network security by confirming that endpoints are known and
   authrosized, and are compliant with network policy.

   When ECP is used, posture information is gathered by collectors
   running on the endpoint and is forwarded to a posture server, which
   stores it in a repository.  This information is gathered while the
   endpoint is already connected to the network.  Administrators will
   query the repository to determine the posture status of an endpoint.
   For example, if a vulnerability is discovered in a product, an
   administrator may query the repository to determine which endpoints
   have the vulnerable software installed and thus require some follow-
   up action.




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   The ECP then describes how to expose information--such as endpoint
   purpose, the software that is supposed to be running on an endpoint,
   and the activities an endpoint is supposed to be performing--to
   sensors that are looking for indicators of attacks and malicious
   activity on the network.

1.1.  Preventative Posture Assessments

   The value of continuous endpoint posture assessment is well
   established.  Security experts have for years identified software
   updating and patching as a critical step for preventing intrusions.
   Application white listing, patching applications and operating
   systems, and using the latest versions of applications top the
   Defense Signals Directorate's "Top 4 Mitigations to Protect Your ICT
   System".  [DSD] "Inventory of Authorized and Unauthorized Endpoints",
   "Inventory of Authorized and Unauthorized Software", and "Continuous
   Vulnerability Assessment and Remediation" are Critical Controls 1, 2,
   and 4, respectively, of the CIS "20 Critical Security Controls".
   [CIS] While there are commercially available solutions that attempt
   to address these security controls, these solutions do not run on all
   types of endpoints; consistently interoperate with other tools that
   could make use of the data collected; collect posture information
   from all types of endpoints in a consistent, standardized schema; or
   require vetted, standardized protocols that have been evaluated by
   the international community for cryptographic soundness.

   As is true of most solutions offered today, the solution found in the
   ECP does not attempt to solve the lying endpoint problem.  An
   endpoint that has already been infected with malicious software can
   provide false information about its identity and the software it is
   running.  The primary purpose of the ECP is not to detect infected
   endpoints; rather, it focuses on ensuring that healthy endpoints
   remain healthy by keeping software up-to-date and patched.  The first
   goal of the ECP is to help an administrator be able to readily
   determine which endpoints require some follow-up action.  By sharing
   posture informatino with sensors on the network, ECP aids in the
   detection of attacks on endpoints and drives follow-up actions.

1.2.  Standardized Schema

   The ECP requires the use of standardized schema for the exchange of
   posture information.  This helps to ensure that the posture
   information sent from endpoints to the repository can be easily
   stored, due to their known format, and shared with authorized
   endpoints and users.  Standardized schema also enable collection from
   myriad types of endpoints.  Such standardization saves implementers
   time and money--time that does not have to be spent integrating new
   schema into the enterprise's reporting mechanisms, and money that



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   does not have to be spent on developing tools to parse information
   from each type of endpoint connected to the network.  Standardized
   schema also enable the development of standardized client software.
   This allows endpoint vendors to include their own client software
   that can interoperate with posture assessment infrastructure and thus
   not have to introduce third party code in their products.

1.3.  Secure Standardized Protocols

   Posture information must be sent over mature, standardized protocols
   to ensure the confidentiality and authenticity of this data while in
   transit.  Conformant implementations of the ECP include [RFC6876] for
   communication between the endpoint and the server.  This protocol
   allows networks that implement this solution to collect large amounts
   of posture information from an endpoint in order to make decisions
   about that endpoint's compliance to some policy.  This Profile offers
   a solution for all endpoints already connected to the network.
   Periodic assessments and automated reporting of changes to endpoint
   posture allow for instantaneous identification of connected endpoints
   that are no longer compliant to some policy.

   The IETF NEA WG has designed an architecture to support endpoint
   posture assessment.  Figure 1 illustrates the architectural
   components used in the Endpoint Compliance Profile:



























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   Endpoint                 Server
   +---------------+        +---------------+
   |               |        |               |
   | +-----------+ |        | +-----------+ |
   | |           | |        | |           | |
   | | Posture   | |        | | Posture   | |
   | | Collector | |        | | Validator | |
   | +-----------+ |        | +-----------+ |
   |      |        |        |      |        |
   |      |        |        |      |        |     Repository
   |      |        |        |      |        |     +--------+
   | +-----------+ |        | +-----------+ |     |        |
   | | Posture   | |        | | Posture   | |     |        |
   | | Client    | |        | | Server    | |---->|        |
   | +-----------+ |        | +-----------+ |     |        |
   |      |        |        |      |        |     |        |
   |      |        |        |      |        |     +--------+
   |      |        |        |      |        |
   | +-----------+ |        | +-----------+ |
   | | Comms     | |        | | Comms     | |
   | | Client    | |<------>| | Server    | |
   | +-----------+ |        | +-----------+ |
   |               |        |               |
   +---------------+        +---------------+

              Figure 1: The Endpoint Compliance Architecture

1.4.  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 [RFC2119].  This
   specification does not distinguish blocks of informative comments and
   normative requirements.  Therefore, for the sake of clarity, note
   that lower case instances of must, should, etc. do not indicate
   normative requirements.

2.  Terminology

   This document uses terms as defined in [I-D.ietf-sacm-terminology]
   unless otherwise specified.

3.  Endpoint Compliance Profile

   The Endpoint Compliance Profile describes how IETF and TNC data
   models and protocols can be used to support the posture assessment of
   endpoints on a network.  This profile does not generate new schema or
   protocols; rather, it offers a full end-to-end solution for posture



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   assessment, as well as a fresh perspective on how existing standards
   can be leveraged against vulnerabilities.

3.1.  Posture Assessments

   The Endpoint Compliance Profile 1.0 describes how IETF and TNC data
   modles and protocols make it possible to perform posture assessments
   against all network-connected endpoints by:

   1.  uniquely identifying the endpoint;

   2.  collecting and assessing posture based on data from the endpoint;

   3.  creating a secure, authenticated, confidential channel between
       the endpoint and the server;

   4.  enabling the endpoint to notify the server about changes to its
       configuration;

   5.  enabling the posture server to request information about the
       configuration of the endpoint; and

   6.  storing the posture information in a repository linked to the
       identifier for the endpoint.

3.2.  Data Storage

   The Endpoint Compliance Profile 1.0 focuses on being able to collect
   posture information from an endpoint and store it in a repository.
   This makes posture information from a network's endpoints available
   to authorized parties.  Uses of this data are innumerable--
   vulnerability management, asset management, software asset
   management, and configuration management solutions, analytics tools,
   endpoints that need to make connectivity decisions, and metrics
   reporting scripts, among others, are all able to reference the data
   stored in the repository to achieve their purposes.

3.3.  Data Sharing

   TBD

4.  Background

4.1.  Purpose of the Endpoint Compliance Profile

   The Endpoint Compliance Profile describes a standard way to collect
   endpoint posture information s and to make it available to other
   authorized parties.



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4.2.  Supported Use Cases

   The Endpoint Compliance Profile focuses on the posture assessment of
   enterprise endpoints on enterprise networks.  Use cases supported by
   the Endpoint Compliance Profile 1.0 are as follows:

4.2.1.  Connected and Compliant

   A network-connected endpoint sends posture information using standard
   schemas an protocols.

   Endpoint                     Server
   +-------------------+        +---------------+
   |                   |        |               |
   | +---------+       |        |               |
   | | Endpoint|       |        |               |
   | | Posture |       |        | +-----------+ |
   | | Data    |       |        | |           | |
   | +---------+       |        | | Validator | |
   |  |                |        | |           | |
   |  |                |        | +-----------+ |
   |  |  +-----------+ |        |      |        |
   |  +->|           | |        |      |        |
   |     | Collector | |        |      |        |
   |     |           | |        |      |        |
   |     +-----------+ |        |      |        |
   |          |        |        |      |        |
   |          |        |        |      |        |     Repository
   |          |        |        |      |        |     +--------+
   |     +-----------+ |        | +-----------+ |     |        |
   |     | Posture   | |        | | Posture   |       |        |
   |     | Client    | |        | |  Server   | |---->|        |
   |     +-----------+ |        | +-----------+ |     |        |
   |               |   |        |      |        |     |        |
   | +----------+  |   |        |      |        |     +--------+
   | | Endpoint |  |   |        |      |        |
   | | ID       |  |   |        |      |        |
   | +----------+  |   |        |      |        |
   |  |            |   |        |      |        |
   |  |  +-----------+ |        | +-----------+ |
   |  +->| Comms     | |        | | Comms     | |
   |     | Client    | |<------>| |  Server   | |
   |     +-----------+ |        | +-----------+ |
   |                   |        |               |
   +-------------------+        +---------------+

                Figure 2: Connected and Compliant Use Case




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   1.  If necessary, the endpoint finds and validates the server in
       compliance with [Server-Discovery].

   2.  The Posture Transport Client (PTC) on the endpoint and Posture
       Transport Server (PTS) on the server complete a TLS handshake,
       during which endpoint identity information is exchanged.

   3.  Either the NEA Server (NEAS) on the server or the NEA Client
       (NEAC) on the endpoint initiates a posture assessment.  Checks
       may be triggered for multiple reasons, including:

       (a)  policy states that a previous assessment has aged out and
            become invalid;

       (b)  the NEAC notices that the relevant posture information on
            the endpoint has changed, (for example, due to application
            updates, deletions or additions); or

       (c)  the NEAS is alerted by a sensor or an administrator (via the
            server's user interface) that an assessment must be
            completed.

       All information exchanges between the PCs and PVs are subject to
       the enterprise's policy, which may limit the content or size of
       information sent between the endpoint and the server.

   4.  The SWID Posture Collector on the endpoint collects from the SWID
       tag directory on the endpoint.  This data is sent via the NEAC
       and PTC to the server.

   5.  Once the posture information is received by the PTS, it is
       forwarded to the SWID Posture Validator via the NEAS.  The SWID
       Posture Validator also forwards the posture information to the
       repository.  The posture information is stored along with past
       posture information collected about the endpoint.

4.2.2.  Exposing Data to the Network

   Because the endpoint posture information was sent in a standards-
   based schema (ISO/IEC 19770-2:2009) over secure, standardized
   protocols, and the SWID tags are stored in a centralized repository
   linked to unique endpoint identifiers, authorized parties are able to
   access the posture information.  Such authorized parties may include,
   but are not limited to, administrators or endpoint owners (via the
   server's administrative interface), and other pieces of
   infrastructure that can make use of this data (via the server's API).
   The server will provide:




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   o  a standard administrative interface that allows data sharing with
      authorized parties;

   o  a standard API that allows data sharing with authorized
      infrastructure and software;

   o  a persistent account of endpoints that have connected to the
      network over a period of time set by the administrator;

   o  the identities provided by those endpoints; and

   o  what SWIDs were reported by the endpoint.

   The endpoint will publish updates as its local SWID directory
   changes, as well as each time it disconnects and reconnects to the
   network.



































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   Endpoint                      Server
   +--------------------+        +---------------+
   |                    |        |               |
   | +-------+          |        | +-----------+ |
   | | SWIDs |          |        | | SWID      | |
   | +-------+          |        | | Posture   | |
   |  |                 |        | | Validator | |
   |  |                 |        | +-----------+ |
   |  |  +-----------+  |        |      |        |
   |  +->| SWID      |  |        |      |        |
   |     | Posture   |  |        |      |        |
   |     | Collector |  |        |      |        |
   |     +-----------+  |        |      |        |
   |          |         |        |      |        |
   |          | IF-IMC  |        |      | IF-IMV |     Repository
   |          |         |        |      |        |     +--------+
   |     +-----------+  |        | +-----------+ |     |        |
   |     | PB Client |  |        | | PB Server | |---->|        |
   |     +-----------+  |        | +-----------+ |     |        |
   |               |    |        |      |        |     |        |
   | +----------+  |    |        |      |        |     +--------+
   | | Endpoint |  |    |        |      |        |
   | | ID       |  |    |        |      |        |
   | +----------+  |    |        |      |        |
   |  |            |    |        |      |        |
   |  |  +-----------+  |        | +-----------+ |
   |  +->| PT Client |  |<------>| | PT Server | |
   |     +-----------+  | PT-TLS | +-----------+ |
   |                    |        |               |
   +--------------------+        +---------------+
                               +----------------------------------+
                               | Administrative Interface and API |
                               +----------------------------------+

                  Figure 3: Exposing Data to the Network

   It should be noted that the neither the Endpoint Compliance Profile
   nor the protocols, interfaces, and data models that it references
   provide solutions to the server capabilities listed above.  However,
   these capabilities are useful and solutions for them should be
   pursued in the future.

4.2.2.1.  Asset Management

   Using the administrative interface on the server, an authorized user
   can learn:

   o  what endpoints are connected to the network at any given time; and



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   o  what SWID tags were reported for the endpoints.

   The ability to answer these questions offers a standards-based
   approach to asset management, which is a vital part of enterprise
   processes such as compliance report generation for the Federal
   Information Security Modernization Act (FISMA), Payment Card Industry
   Data Security Standard (PCI DSS), Health Insurance Portability and
   Accountability Act (HIPAA), etc.

4.2.2.2.  Vulnerability Searches

   The administrative interface also provides the ability for authorized
   users or infrastructure to locate endpoints running software for
   which vulnerabilities have been announced.  Because of

   1.  the unique IDs assigned to each endpoint; and

   2.  the rich application data provided in the endpoints' posture
       information,

   the repository can be queried to find all endpoints running a
   vulnerable application.  Endpoints suspected of being vulnerable can
   be addressed by the administrator or flagged for further scrutiny.

4.2.2.3.  Threat Detection and Analysis

   The repository's standardized API allows authorized infrastructure
   endpoints and software to search endpoint posture assessment
   information for evidence that an endpoint's software inventory has
   changed, and can make endpoint software inventory data available to
   other endpoints.  This automates security data sharing in a way that
   expedites the correlation of relevant network data, allowing
   administrators and infrastructure endpoints to identify odd endpoint
   behavior and configuration using secure, standards-based schema and
   protocols.

4.2.3.  Non-supported Use Cases

   Several use cases, including but not limited to these, are not
   covered by the Endpoint Compliance Profile 1.0:

   o  Gathering other types of posture information: The Endpoint
      Compliance Profile does not prevent administrators from collecting
      other types of posture information other than SWIDs from the
      endpoint; however it does not set requirements for doing so.

   o  Solving the lying endpoint problem: The Endpoint Compliance
      Profile does not address the lying endpoint problem; the Profile



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      makes no assertions that it can catch an endpoint that is, either
      maliciously or accidentally, reporting false posture information
      to the server.  However, other solutions may be able to use the
      posture information collected using the capabilities described in
      this profile to catch an endpoint in a lie.  For example, a sensor
      may be able to compare the posture information it has collected on
      an endpoint's activity on the network to what the endpoint
      reported to the server and flag discrepancies.  However, these
      particular capabilities are not described in this profile.

   o  Publish/subscribe repository interface: Future versions of the
      Endpoint Compliance Profile may specify a publish/subscribe
      interface for the repository, so infrastructure endpoint can
      subscribe to and receive published posture assessment results from
      the repository regarding endpoint configuration changes.  However,
      the Endpoint Compliance Profile 1.0 includes no such requirements.

4.2.4.  Profile Requirements

   Here are the requirements that the Endpoint Compliance Profile
   protocol must meet in order to successfully fit in the SACM
   architecture.

   o  Meets the needs of the SACM architecture: The Endpoint Compliance
      Profile must support the use cases described in [RFC7632] as they
      apply to endpoint self-reporting and endpoint posture assessment.

   o  Efficient: To minimize user frustration, it is essential to
      minimize delays by making endpoint posture information collection,
      transmission, and assessment as brief and efficient as possible.

   o  Extensible: The Endpoint Compliance Profile needs to expand over
      time as new features are added to the SACM architecture.  The
      solution must allow new features to be added easily, providing for
      a smooth transition and allowing newer and older architectural
      components to continue to work together.  Further, the Endpoint
      Compliance Profile and the specifications referenced here must
      define safe extensibility mechanisms that enable innovation
      without breaking interoperability.

   o  Easy to implement: The Endpoint Compliance Profile should be easy
      for vendors to implement in their products, and should result in
      products that are easy for administrators to implement on their
      networks.  Products conformant to the Endpoint Compliance Profile
      should interoperate seamlessly, and be simple to integrate into
      existing network infrastructure.





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   o  Easy to use: The Endpoint Compliance Profile should describe a
      simple, integrated user interface that administrators can use to
      perform the activities listed in the profile's use cases.  The
      Endpoint Compliance Profile should not constrain innovation by
      specifying details of the user interface but rather functional
      requirements.

   o  Platform-independent: Since network environments may contain many
      different types of endpoints, the solution should operate
      independently of the endpoint platform.

   o  Scalable: The Endpoint Compliance Profile must be designed to
      scale to very large numbers of endpoints.

4.2.5.  Assumptions

   Here are the assumptions that the Endpoint Compliance Profile makes
   about other components in the SACM architecture.

   o  Existence of a server and repository: The Endpoint Compliance
      Profile assumes that a server and repository exist.

   o  Endpoint SWID installation: The Endpoint Compliance Profile
      assumes that an endpoint has been pre-provisioned with Software
      Identification Tags for its applications, and that these SWID tags
      are formatted and stored in conformance with [SWID].

   o  Certificate provisioning: In order to implement the most secure
      endpoint identification option, the Endpoint Compliance Profile
      assumes that the enterprise has set up a certificate root
      authority, and has provisioned each endpoint with an endpoint
      identification certificate.  This is not required if an enterprise
      chooses to use other endpoint authentication methods.

   In addition, the Endpoint Compliance Profile makes the following
   assumptions about the SACM ecosystem:

   o  All network-connected endpoints are endpoints: As defined by
      [I-D.ietf-sacm-terminology], an endpoint is any physical or
      virtual computing endpoint that can be connected to a network.
      Posture assessment against policy is equally, if not more,
      important for continuously connected endpoints, such as enterprise
      workstations and infrastructure endpoints, as it is for
      sporadically connected endpoints.  Continuously connected
      endpoints are just as likely to fall out of compliance with
      policy, and a standardized posture assessment method is necessary
      to ensure they can be properly handled.




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   o  All endpoints on the network must be uniquely identified: Many
      administrators struggle to identify what endpoints are connected
      at any given time.  By requiring a standardized method of endpoint
      identity, the Endpoint Compliance Profile will enable
      administrators to answer the basic question, "What is on my
      network?"  Unique endpoint identification also enables the
      comparison of current and past endpoint posture assessments, by
      allowing administrators to correlate assessments from the same
      endpoint.  This makes it easier to flag suspicious changes in
      endpoint posture for manual or automatic review, and helps to
      swiftly identify malicious changes to endpoint applications.

   o  Posture assessments must occur over secure, standardized
      protocols: Endpoint identity and application information is very
      valuable, both to administrators and to attackers.  Therefore, it
      must be kept confidential, using secure protocols to transport it
      from the endpoint to network infrastructure endpoints.
      Additionally, it is critical that only authorized parties be
      capable of requesting information, receiving information, or
      taking action to change an endpoint's connectivity status.
      Relying on standardized protocols to provide this security enables
      greater interoperability and compatibility between endpoints, and
      allows for the development of compliance testing to ensure that
      each endpoint operates securely and in conformance with
      appropriate specifications.  A standards body provides a process
      for experts in protocols and cryptography to evaluate the
      soundness of protocols and security management procedures; a set
      of security standards allows an enterprise to make the most
      effective use of their investment in a security management
      infrastructure.

   o  Posture assessment results must be formatted using standardized
      schema: Well-known, standard schema allow for a universal language
      for generating compliance reports.  With each endpoint speaking
      the same language, the Endpoint Compliance Profile enables
      information sharing between user endpoints and infrastructure
      endpoints, and between infrastructure endpoints that perform
      different security tasks.

   o  Posture information must be stored by the repository and must be
      exposed to an interface at the server: A standard schema enables
      standard queries from an interface exposed to an administrator at
      the server console.  A repository must retain any current posture
      information retrieved from the endpoint and store it indexed by
      the unique identifier for the endpoint.  Any PV specified by this
      profile must be able to ascertain from its corresponding PC
      whether the posture information is up to date.  An interface on
      the server must support a request to the PV to obtain up-to-date



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      information when an endpoint is connected.  This interface must
      also support the ability to make a standard set of queries about
      the posture information stored by the repository.  In the future,
      some forms of posture information might be retained at the
      endpoint.  The interface on the server must accommodate the
      ability to make a request through the PV to the corresponding PC
      about the posture of the endpoint.  Standard schema and protocols
      also enable the security of posture assessment results.  By
      storing these results indexed under the endpoint's unique
      identification, secure storage itself enables endpoint posture
      information correlation, and ensures that the enterprise's
      Repositories always offer the freshest, most up-to-date view of
      the enterprise's endpoint posture information possible.

   o  Posture information can be shared: By exposing posture information
      using a standard interface and API, other security and operational
      components have a high level of insight into the enterprise's
      endpoints and the software installed on them.  This will support
      innovation in the areas of asset management, vulnerability
      scanning, and administrative interfaces, as any authorized
      infrastructure endpoint can interact with the posture information.

   o  Owners and administrators must have complete control of posture
      information, policy, and endpoint mitigation: Enterprise asset
      posture information belongs to the enterprise.  Standardized
      schema, protocols and interfaces help to ensure that this posture
      information is not locked in proprietary databases, but is made
      available to its owners.  This enables administrators to develop
      as nuanced a policy as necessary to keep their networks secure.

5.  Endpoint Compliance Requirements

   These requirements are written with a view to performing a posture
   assessment on an endpoint; as the Endpoint Compliance Profile grows
   and evolves, these requirements will be expanded to address issues
   that arise.  Note that these requirements refer to defined components
   of the NEA architecture.  As with the NEA architecture, implementers
   have discretion as to how these NEA components map to separate pieces
   of software or endpoints.

5.1.  Endpoint Pre-Provisioning

   The following requirements assume that the platform or OS vendor
   supports the use of SWID tags and has identified a standard directory
   location for the SWID tags to be located as specified by [SWID].






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5.1.1.  SWID Tags

   The primary content for the Endpoint Compliance Profile 1.0 is the
   information conveyed in the elements of a SWID tag.

   The endpoint MUST have SWID tags stored in a directory specified in
   [SWID].  The tags SHOULD be provided by the software vendor; they MAY
   also be generated by:

   o  the software installer; or

   o  third-party software that creates tags based on the applications
      it sees installed on the endpoint.

   The elements in the SWID tag MUST be populated as specified in
   [SWID].  These tags, and the directory in which they are stored, MUST
   be updated as software is added, removed, or updated.

5.1.2.  Endpoint Identity and Machine Certificate

   The endpoint SHOULD authenticate to the server using a machine
   certificate during the establishment of the outer tunnel achieved
   with PT.  [IF-IMV] specifies how to pull an endpoint ID out of a
   machine certificate.  An endpoint ID SHOULD be created in conformance
   with [IF-IMV] from a machine certificate sent via [RFC6876].

   In the future, the identity could be a hardware certificate compliant
   with [IEEE-802-1ar]; ideally, this ID SHOULD be associated with the
   identity of a hardware cryptographic module, in accordance with
   [IEEE-802-1ar], if present on the endpoint.  The enterprise SHOULD
   stand up a certificate root authority; install its root certificate
   on endpoints and on the server; and provision the endpoints and the
   server with machine certificates.  The endpoint MAY authenticate to
   the server using a combination of the machine account and password;
   however, this is less secure and not recommended.

5.2.  Posture Validators and Posture Collectors

   Any PC used in an Endpoint Compliance Profile solution MUST be
   conformant with [IF-IMC]; an Internet-Draft, under development, that
   is a subset of the TCG TNC Integrity Measurement Collector interface
   [IF-IMC] and will be submitted in the near future.  Any Posture
   Validator used in an Endpoint Compliance Profile solution MUST be
   conformant with [IF-IMV].







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5.2.1.  SWID Posture Collectors and Posture Validators

5.2.1.1.  The SWID Posture Collector

   For the Endpoint Compliance Profile, the SWID Posture Collector MUST
   be conformant with [I-D.ietf-sacm-nea-swid-patnc], which includes
   requirements for:

   1.  Collecting SWID tags from the SWID directory

   2.  Monitoring the SWID directory for changes

   3.  Initiating a session with the server to report changes to the
       directory

   4.  Maintaining a list of changes to the SWID directory when updates
       take place and no PT-TLS connection can be created with the
       server

   5.  Responding to a request for SWID tags from the SWID Posture
       Validator on the server

   6.  Responding to a query from the SWID Posture Validator as to
       whether all updates have been sent

   The SWID Posture Collector is not responsible for detecting that the
   SWID directory was not updated when an application was either
   installed or uninstalled.

5.2.1.2.  The SWID Posture Validator

   Conformance to [I-D.ietf-sacm-nea-swid-patnc] enables the SWID
   Posture Validator to:

   1.  Send messages to the SWID Posture Collector (at the behest of the
       administrator at the server console) requesting updates for SWID
       tags located on endpoint

   2.  Ask the SWID Posture Collector whether all updates to the SWID
       directory located at the server have been sent

   3.  Compare an endpoint's SWID posture information to policy, and
       make a recommendation to the NEAS about the endpoint

   In addition to these requirements, a SWID Posture Validator used in
   conformance with this profile MUST be capable of passing information
   from the posture assessment results and the endpoint identity
   associated with those results to the repository for storage.



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5.3.  NEA Client (NEAC) and NEA Server (NEAS)

   [RFC5793] describes a standard way for the NEAC and the NEAS to
   exchange messages.

5.3.1.  NEAC

   The NEAC MUST conform to [RFC5793], which levies a number of
   requirements against the NEAC.  A NEAC that complies with these
   requirements will be able to:

   1.  attempt to initiate a session with the NEAS if the SWID Posture
       Collector makes a request to send an update to the SWID directory
       to the server;

   2.  notify the SWID Posture Collector if no PT-TLS session with the
       server can be created;

   3.  notify the SWID Posture Collector when a PT-TLS session is
       established; and

   4.  receive information from the PCs, forward this information to the
       server via the PTC.

   The NEAC MUST also conform to [IF-IMC] to enable communications with
   the SWID Posture Collector.

5.3.2.  NEAS

   The NEAS MUST conform to all requirements in the [RFC5793] and
   [IF-IMV] specifications.  Conformance to [IF-IMV] enables the NEAS to
   obtain endpoint identity information from the PTS, and pass this
   information to any IMVs on the server.

5.4.  Repository

   ECP 1.0 requires a simple administrative interface for the
   repository.  PVs on the server receive the endpoint data via PA-TNC
   [RFC5792] messages sent from corresponding PCs on an endpoint and
   store this information in the repository linked to the identity of
   the endpoint where the PCs are located.

   The administrative interface SHOULD enable an administrator to:

   1.  Query which endpoints have reported SWID tags for a particular
       application

   2.  Query which SWID tags are installed on a particular endpoint



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   3.  Query tags based on characteristics, such as vendor, publisher,
       etc.

   In the future, if SACM decides to develop an interface to the
   repository server, it should consider requirements for:

   1.  Creating a secure channel between a publisher and the repository

   2.  Creating a secure channel between a subscriber and the repository

   3.  The types of interactions that must be supported between
       publishers and subscribers to a repository

6.  Posture Transport Client (PTC) and Posture Transport Server (PTS)

   The PT-TLS protocol provides a transport service for carrying the PB-
   TNC protocol messages between the endpoint and the server.

   The PTC and PTS MUST implement PT-TLS, since a connection is needed
   that:

   o  Can handle large volumes of data, which might require multiple
      roundtrips, to be sent while the endpoint is connected

   o  Allows either the NEAC or NEAS to initiate a connection

   o  Supports secure transport based on machine certificates at both
      ends of the connection

   The PTC and PTS MUST support the use of machine certificates for TLS
   at each endpoint consistent with the requirements stipulated in
   [RFC6876] and [Server-Discovery].

   The PTC MUST be able to locate an authorized server, and switch to a
   new server when required by the network, in conformance with
   [Server-Discovery].

7.  Administrative Interface and API

   An interface is necessary to allow administrators to manage the
   endpoints and software used in the Endpoint Compliance Profile.  This
   interface SHOULD be accessible either on or through (as in the case
   of a remotely hosted interface) the server.  Using this interface, an
   authorized user or administrator SHOULD be able to:

   o  Query the repository





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   o  Send commands to the PVs, requesting information from the
      associated PCs residing on network endpoints

   o  Update the policy that resides on the server

   An API is necessary to allow infrastructure endpoints and software
   access to the information stored in the repository.  Using this API,
   an authorized endpoint SHOULD be able to:

   o  Query the repository

8.  Endpoint Compliance Profile Examples

8.1.  Continuous Posture Assessment of an Endpoint

   Endpoint                 Server
   +---------------+        +---------------+
   |               |        |               |
   | +-----------+ |        | +-----------+ |
   | | SWID      | |        | | SWID      | |
   | | Posture   | |        | | Posture   | |
   | | Collector | |        | | Validator | |
   | +-----------+ |        | +-----------+ |
   |      |        |        |      |        |
   |      | IF-IMC |        |      | IF-IMV |
   |      |        |        |      |        |
   | +-----------+ |        | +-----------+ |
   | | PB Client | |        | | PB Server | |
   | +-----------+ |        | +-----------+ |
   |      |        |        |      |        |
   |      |        |        |      |        |
   |      |        |        |      |        |
   | +-----------+ |        | +-----------+ |
   | | PT Client | |<------>| | PT Server | |
   | +-----------+ | PT-TLS | +-----------+ |
   |               |        |               |
   +---------------+        +---------------+

          Figure 4: Continuous Posture Assessment of an Endpoint

8.1.1.  Change on Endpoint Triggers Posture Assessment

   A new application is installed on the endpoint, and the SWID
   directory is updated.  This triggers an update from the SWID Posture
   Collector to the SWID Posture Validator.  The message is sent down
   the NEA stack, encapsulated by NEA protocols until it is sent by the
   PTC to the PTS.  The PTS then forwards it up through the stack, where




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   the layers of encapsulation are removed until the SWID Message
   arrives at the SWID Posture Validator.

   Endpoint                         Server
   +---------------+                +---------------+
   |               |                |               |
   | +-----------+ |                | +-----------+ |
   | | SWID      | |                | | SWID      | |
   | | Posture   | |                | | Posture   | |
   | | Collector | |                | | Validator | |
   | +-----------+ |                | +-----------+ |
   |      |        | SWID Message   |      |        |
   |      | IF-IMC | for PA-TNC     |      | IF-IMV |
   |      |        |                |      |        |
   | +-----------+ |                | +-----------+ |
   | | PB Client | |                | | PB Server | |
   | +-----------+ |                | +-----------+ |
   |      |        |                |      |        |
   |      |        | PB-TNC {SWID   |      |        |
   |      |        | Message for    |      |        |
   |      |        | PA-TNC}        |      |        |
   | +-----------+ |                | +-----------+ |
   | | PT Client | |<-------------->| | PT Server | |
   | +-----------+ | PT-TLS {PB-TNC | +-----------+ |
   |               | {SWID Message  |               |
   +---------------+ for PA-TNC}}   +---------------+

                Figure 5: Compliance Protocol Encapsulation

   The SWID Posture Validator stores the new tag information in the
   repository.  If the tag indicates that the endpoint is compliant to
   the policy, then the process is complete until the next time an
   update is needed (either because policy states that the endpoint must
   submit posture assessment results periodically or because an
   install/uninstall/update on the endpoint triggers a posture
   assessment).















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   Endpoint                 Server
   +---------------+        +---------------+
   |               |        |               |
   | +-----------+ |        | +-----------+ |
   | | SWID      | |        | | SWID      |-|-+
   | | Posture   | |        | | Posture   | | |
   | | Collector | |        | | Validator | | |
   | +-----------+ |        | +-----------+ | |
   |      |        |        |      |        | |     Repository
   |      | IF-IMC |        |      | IF-IMV | |     +--------+
   |      |        |        |      |        | |     |        |
   | +-----------+ |        | +-----------+ | |     |        |
   | | PB Client | |        | | PB Server | | +---->|        |
   | +-----------+ |        | +-----------+ |       |        |
   |      |        |        |      |        |       +--------+
   |      |        |        |      |        |
   |      |        |        |      |        |
   | +-----------+ |        | +-----------+ |
   | | PT Client | |<------>| | PT Server | |
   | +-----------+ | PT-TLS | +-----------+ |
   |               |        |               |
   +---------------+        +---------------+

                 Figure 6: Storing SWIDs in the Repository

   If the endpoint has fallen out of compliance with a policy, the
   server can alert the administrator via the server's administrative
   interface.  The administrator can then take steps to address the
   problem.  If the administrator has already established a policy for
   automatically addressing this problem, that policy will be followed.





















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                                                 (")
                                                __|__
                                              +-->|
   Endpoint                 Server            |  / \
   +---------------+        +---------------+ |
   |               |        |               | |
   | +-----------+ |        | +-----------+ | |
   | | SWID      | |        | | SWID      |-|-+
   | | Posture   | |        | | Posture   | |
   | | Collector | |        | | Validator | |
   | +-----------+ |        | +-----------+ |
   |      |        |        |      |        |       Repository
   |      | IF-IMC |        |      | IF-IMV |       +--------+
   |      |        |        |      |        |       |        |
   | +-----------+ |        | +-----------+ |       |        |
   | | PB Client | |        | | PB Server | |       |        |
   | +-----------+ |        | +-----------+ |       |        |
   |      |        |        |      |        |       +--------+
   |      |        |        |      |        |
   |      |        |        |      |        |
   | +-----------+ |        | +-----------+ |
   | | PT Client | |<------>| | PT Server | |
   | +-----------+ | PT-TLS | +-----------+ |
   |               |        |               |
   +---------------+        +---------------+

                   Figure 7: Server Alerts Network Admin

8.2.  Administrator Searches for Vulnerable Endpoints

   An announcement is made that a particular version of a piece of
   software has a vulnerability.  The administrator uses the
   Administrative Interface on the server to search the repository for
   endpoints that reported the SWID tag for the vulnerable software.

















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                                                 (")
                                                __|__
                                              +-->|
   Endpoint                 Server            |  / \
   +---------------+        +---------------+ |
   |               |        |               | |
   | +-----------+ |        | +-----------+ | |
   | | SWID      | |        | | SWID      |-|-+
   | | Posture   | |        | | Posture   | |
   | | Collector | |        | | Validator | |
   | +-----------+ |        | +-----------+ |
   |      |        |        |      |        |       Repository
   |      | IF-IMC |        |      | IF-IMV |       +--------+
   |      |        |        |      |        |       |        |
   | +-----------+ |        | +-----------+ |       |        |
   | | PB Client | |        | | PB Server | |------>|        |
   | +-----------+ |        | +-----------+ |       |        |
   |      |        |        |      |        |       +--------+
   |      |        |        |      |        |
   |      |        |        |      |        |
   | +-----------+ |        | +-----------+ |
   | | PT Client | |<------>| | PT Server | |
   | +-----------+ | PT-TLS | +-----------+ |
   |               |        |               |
   +---------------+        +---------------+

             Figure 8: Admin Searches for Vulnerable Endpoints

   The repository returns a list of entries in the matching the
   administrator's search.  The administrator can then address the
   vulnerable endpoints by taking some follow-up action such as removing
   it from the network, quarantining it, or updating the vulnerable
   software.

9.  Acknowledgements

   The authors wish to thank all of those in the TCG TNC work group who
   contributed to development of the TNC ECP specification upon which
   this document is based.

   +-----------------------+-------------------------------------------+
   | Member                | Organization                              |
   +-----------------------+-------------------------------------------+
   | Padma Krishnaswamy    | Battelle Memorial Institute               |
   |                       |                                           |
   | Eric Fleischman       | Boeing                                    |
   |                       |                                           |
   | Richard Hill          | Boeing                                    |



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   |                       |                                           |
   | Steven Venema         | Boeing                                    |
   |                       |                                           |
   | Nancy Cam-Winget      | Cisco Systems                             |
   |                       |                                           |
   | Scott Pope            | Cisco Systems                             |
   |                       |                                           |
   | Max Pritikin          | Cisco Systems                             |
   |                       |                                           |
   | Allan Thompson        | Cisco Systems                             |
   |                       |                                           |
   | Nicolai Kuntze        | Fraunhofer Institute for Secure           |
   |                       | Information Technology (SIT)              |
   |                       |                                           |
   | Ira McDonald          | High North                                |
   |                       |                                           |
   | Dr. Andreas Steffen   | HSR University of Applied Sciences        |
   |                       | Rapperswil                                |
   |                       |                                           |
   | Josef von Helden      | Hochschule Hannover                       |
   |                       |                                           |
   | James Tan             | Infoblox                                  |
   |                       |                                           |
   | Steve Hanna (TNC-WG   | Juniper Networks                          |
   | Co-Chair)             |                                           |
   |                       |                                           |
   | Cliff Kahn            | Juniper Networks                          |
   |                       |                                           |
   | Lisa Lorenzin         | Juniper Networks                          |
   |                       |                                           |
   | Atul Shah (TNC-WG Co- | Microsoft                                 |
   | Chair)                |                                           |
   |                       |                                           |
   | Jon Baker             | MITRE                                     |
   |                       |                                           |
   | Charles Schmidt       | MITRE                                     |
   |                       |                                           |
   | Rainer Enders         | NCP Engineering                           |
   |                       |                                           |
   | Dick Wilkins          | Phoenix Technologies                      |
   |                       |                                           |
   | David Waltermire      | NIST                                      |
   |                       |                                           |
   | Mike Boyle            | U.S. Government                           |
   |                       |                                           |
   | Emily Doll            | U.S. Government                           |
   |                       |                                           |
   | Jessica Fitzgerald-   | U.S. Government                           |



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   | McKay                 |                                           |
   |                       |                                           |
   | Mary Lessels          | U.S. Government                           |
   |                       |                                           |
   | Chris Salter          | U.S. Government                           |
   +-----------------------+-------------------------------------------+

      Table 1: Members of the TNC Work Group that Contributed to the
                                 Document

10.  IANA Considerations

   This document does not define any new IANA registries.  However, this
   document does reference other documents that do define IANA
   registries.  As a result, the IANA Considerations section of the
   referenced documents should be consulted.

11.  Security Considerations

   The Endpoint Compliance Profile offers substantial improvements in
   endpoint security, as evidenced by the Australian Defense Signals
   Directorate's analysis that 85% of targeted cyber intrusions can be
   prevented through application white listing, patching applications
   and operating systems, and using the latest versions of applications.
   [DSD] Despite these gains, some security risks continue to exist and
   must be considered.

   To ensure that these benefits and risks are properly understood, this
   Security Considerations section includes an analysis of the benefits
   provided by the Endpoint Compliance Profile (Section 11.1), the
   attacks that may be mounted against systems that implement the
   Endpoint Compliance Profile (Section 11.2), and the countermeasures
   that may be used to prevent or mitigate these attacks (Section 11.3).
   Overall, a substantial reduction in cyber risk can be achieved.

11.1.  Security Benefits of Endpoint Compliance Profile

   Security weaknesses of the components for this profile should be
   considered in light of the practical considerations that must be
   addressed to have a viable solution.

   Posture assessment has two parts: assessment and follow-up actions.
   The point of posture assessment is to ensure that authorized users
   are using authorized software configured to be as resilient as
   possible against an attack.

   Posture assessment answers the question whether the endpoint is
   healthy.  Our goal for posture assessment is to make it harder for an



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   adversary to execute code on one of our endpoints.  This profile
   represents an important first step in reaching that goal.  If we keep
   our endpoints healthier, we are able to prevent more attacks on our
   endpoints and thus on our information systems.

   The goal of ECP is to address posture assessment in stages.  Stage 1
   is the ability to ascertain whether all endpoints are authorized and
   whether all applications are authorized and up to date.  Stage 2 will
   attempt to address the harder problem of whether all software is
   configured safely.  Eventually, the goal is to also address
   remediation which is currently out-of-scope for the SACM WG; that
   presents a far greater security challenge than reporting, since
   remediation implies the ability of a remote party to modify software
   or its settings on endpoints.

   A second security consideration is how to gain visibility over every
   type of endpoint and every piece of software installed on the
   endpoint.  This is a problem of scaling and observation.  A solution
   is needed that can report from every type of endpoint.  All software
   on the endpoint has to be discovered.  Information about the software
   has to be up to date and accurate.  The information that is
   discovered has to be reported in a consistent format, so
   administrators do not have to squander time deciphering proprietary
   systems and the information can be made readily useful for other
   security automation purposes.

   ECP is based on a model of a standards-based schema, a standards-
   based set of protocols and interfaces, and the existence of an
   oversight group, the IETF, that can update the schemas and protocols
   to meet new use cases and security issues that may be discovered.

   The data elements in the schema determine what work can be done
   consistently for every endpoint and every piece of software.  How the
   data gets populated is an important consideration.  ECP leverages the
   SWID tags from ISO 19770-2 because the tag originates with a single
   authoritative source, the application vendor itself.  Moreover, there
   is a natural incentive for the vendor to create this content, since
   it makes it easier for enterprises and vendors to track whether
   software is licensed.  Practical considerations are security
   considerations.  A sustainable business model for obtaining all the
   necessary content is a fundamental requirement.

   The NEA model is based on having a NEAC run on an endpoint that
   publishes posture information to a server.  The advantages are easy
   to list.  A platform vendor can implement its own NEAC and have it be
   compatible with the NEAS from a different vendor.  The interfaces are
   layered on top of mature protocols such as TLS.  TLS is the protocol
   of choice for ECP, since:



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   o  it has proven secure properties,

   o  it can be implemented on most types of endpoints,

   o  it allows the gathering of large amounts of information when a
      endpoint is connected, and

   o  it enables use of a mechanism to ensure that the client is
      authenticated (authorized) - a client certificate - which also
      provides a consistent identifier.

   Mature protocols that can be implemented on most types of endpoints
   and a standards-based schema with a sustainable business model are
   both critical security considerations for compliance.

   Additionally, it is important to consider the future stages for ECP
   such as a posture assessment being followed up by some action (e.g.
   remediation, alert, etc.).  Ensuring that clients are taking
   instructions only from authorized parties will be critical.  Inasmuch
   as it is practical, enterprises will want to use the same
   infrastructure and investment in PKI to send those instructions to a
   client.

   Likewise, as more information with more value is gathered from
   endpoints, we will also want to ensure that this information is only
   released to authorized applications and parties.  For the next stage
   of ECP, SACM may want to define an interface on the repository that
   can be queried by other security automation applications to make it
   easier to detect attacks and for other security automation
   applications.  This interface has to be standards-based for
   enterprises to reap the benefits of innovation that can be achieved
   by making the enterprise's data available to other tools and
   services.

11.2.  Threat Model

   This section lists the attacks that can be mounted on an Endpoint
   Compliance Profile environment.  The following section (Section 11.3)
   describes countermeasures.

   Because the Endpoint Compliance Profile describes a specific use case
   for NEA components, many security considerations for these components
   are addressed in more detail in the technical specifications:
   [I-D.ietf-sacm-nea-swid-patnc], [IF-IMC], [RFC5793],
   [Server-Discovery], [RFC6876], [IF-IMV].






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11.2.1.  Endpoint Attacks

   While the Endpoint Compliance Profile provides substantial
   improvements in endpoint security as described in Section 11.1, a
   certain percentage of endpoints will always get compromised.  For
   this reason, all parties must regard data coming from endpoints as
   potentially unreliable or even malicious.  An analogy can be drawn
   with human testimony in an investigation or trial.  Human testimony
   is essential but must be regarded with suspicion.

   o  Compromise of endpoint: A compromised endpoint may report false
      information to confuse or even provide maliciously crafted
      information with a goal of infecting others.

   o  Putting bad information in SWID directory: Even if an endpoint is
      not completely compromised, some of the software running on it may
      be unreliable or even malicious.  This software, potentially
      including the SWID generation or discovery tool, or malicious
      software pretending to be a SWID generation or discovery tool, can
      place incorrect or maliciously crafted information into the SWID
      directory.  Endpoint users may even place such information in the
      directory, whether motivated by curiosity or confusion or a desire
      to bypass restrictions on their use of the endpoint.

   o  Identity spoofing (impersonation): A compromised endpoint may
      attempt to impersonate another endpoint to gain its privileges or
      to besmirch the reputation of that other endpoint.

11.2.2.  Network Attacks

   A variety of attacks can be mounted using the network.  Generally,
   the network cannot be trusted.

   o  Eavesdropping, modification, injection, replay, deletion

   o  Traffic analysis

   o  Denial of service and blocking traffic

11.2.3.  Server Attacks

   The server is a critical security element and therefore merits
   considerable scrutiny.

   o  Compromised trusted server: A compromised server or a malicious
      party that is able to impersonate a server can incorrectly grant
      or deny access to endpoints, place incorrect information into the
      repository, or send malicious messages to endpoints



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   o  Misconfiguration of trusted server: Accidental or purposeful
      misconfiguration of a trusted server can cause effects that are
      similar to those listed for compromised trusted server.

   o  Malicious untrusted server: An untrusted server cannot mount any
      significant attacks because all properly implemented endpoints
      will refuse to engage in any meaningful dialog with such a server.

11.2.4.  Repository Attacks

   The repository is also an important security element and therefore
   merits careful scrutiny.

   o  Putting bad information into trusted repository: An authorized
      repository client such as a server may be able to put incorrect
      information into a trusted repository or delete or modify
      historical information, causing incorrect decisions about endpoint
      security.  Placing maliciously crafted data in the repository
      could even lead to compromise of repository clients, if they fail
      to carefully check such data.

   o  Compromised trusted repository: A compromised trusted repository
      or a malicious untrusted repository that is able to impersonate a
      trusted repository can lead to effects similar to those listed for
      "Putting bad information into trusted repository".  Further, a
      compromised trusted repository can report different results to
      different repository clients or deny access to the repository for
      selected repository clients.

   o  Misconfiguration of trusted repository: Accidental or purposeful
      misconfiguration of a trusted repository can deny access to the
      repository or result in loss of historical data.

   o  Malicious untrusted repository: An untrusted repository cannot
      mount any significant attacks because all properly implemented
      repository clients will refuse to engage in any meaningful dialog
      with such a repository.

11.3.  Countermeasures

   This section lists the countermeasures that can be used in an
   Endpoint Compliance Profile environment.

11.3.1.  Countermeasures for Endpoint Attacks

   This profile is in and of itself a countermeasure for a compromised
   endpoint.  A primary defense for an endpoint is to run up to date
   software configured to be run as safely as possible.



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   Ensuring that anti-virus signatures are up to date and that a
   firewall is configured are also protections for an endpoint that are
   supported by the current NEA specifications.

   Endpoints that have hardware cryptographic modules that are
   provisioned by the enterprise, in accordance with [IEEE-802-1ar], can
   protect the private keys used for authentication and help prevent
   adversaries from stealing credentials that can be used for
   impersonation.  Future versions of the Endpoint Compliance Profile
   may want to discuss in greater detail how to use a hardware
   cryptographic module, in accordance with [IEEE-802-1ar], to protect
   credentials and to protect the integrity of the code that executes
   during the bootstrap process.

11.3.2.  Countermeasures for Network Attacks

   To address network attacks, [RFC6876] includes required encryption,
   authentication, integrity protection, and replay protection.
   [Server-Discovery] also includes authorization checks to ensure that
   only authorized servers are trusted by endpoints.  Any unspecified or
   not yet specified network protocols employed in the Endpoint
   Compliance Profile (e.g. the protocol used to interface with the
   repository) should include similar protections.

   These protections reduce the scope of the network threat to traffic
   analysis and denial of service.  Countermeasures for traffic analysis
   (e.g. masking) are usually impractical but may be employed.
   Countermeasures for denial of service (e.g. detecting and blocking
   particular sources) SHOULD be used when appropriate to detect and
   block denial of service attacks.  These are routine practices in
   network security.

11.3.3.  Countermeasures for Server Attacks

   Because of the serious consequences of server compromise, servers
   SHOULD be especially well hardened against attack and minimized to
   reduce their attack surface.  They SHOULD be monitored using the NEA
   protocols to ensure the integrity of the behavior and analysis data
   stored on the server and SHOULD utilize a [IEEE-802-1ar] compliant
   hardware cryptographic module for identity and/or integrity
   measurements of the server.  They should be well managed to minimize
   vulnerabilities in the underlying platform and in systems upon which
   the server depends.  Network security measures such as firewalls or
   intrusion detection systems may be used to monitor and limit traffic
   to and from the server.  Personnel with administrative access to the
   server should be carefully screened and monitored to detect problems
   as soon as possible.  Server administrators should not use password-
   based authentication but should instead use non-reusable credentials



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   and multi-factor authentication (where available).  Physical security
   measures should be employed to prevent physical attacks on servers.

   To ease detection of server compromise should it occur, server
   behavior should be monitored to detect unusual behavior (such as a
   server reboot, unusual traffic patterns, or other odd behavior).
   Endpoints should log and/or notify users and/or administrators when
   peculiar server behavior is detected.  To aid forensic investigation,
   permanent read-only audit logs of security-relevant information
   pertaining to servers (especially administrative actions) should be
   maintained.  If server compromise is detected, the server's
   certificate should be revoked and careful analysis should be
   performed of the source and impact of this compromise.  Any reusable
   credentials that may have been compromised should be reissued.

   Endpoints can reduce the threat of server compromise by minimizing
   the number of trusted servers, using the mechanisms described in
   [Server-Discovery].

11.3.4.  Countermeasures for Repository Attacks

   If the host for the repository is located on its own endpoint, it
   should be protected with the same measures taken to protect the
   server.  In this circumstance, all messages between the server and
   repository should be protected with a mature security protocol such
   as TLS or IPsec.

   The repository can aid in the detection of compromised endpoints if
   an adversary cannot tamper with its contents.  For instance, if an
   endpoint reports that it does not have an application with a known
   vulnerability installed, an administrator can check whether the
   endpoint might be lying by querying the repository for the history of
   what applications were installed on the endpoint.

   To help prevent tampering with the information in the repository:

   1.  Only authorized parties should have privilege to run code on the
       endpoint and to change the repository.

   2.  If a separate endpoint hosts the repository, then the
       functionality of that endpoint should be limited to hosting the
       repository.  The firewall on the repository should only allow
       access to the server and to any endpoint authorized for
       administration.

   3.  The repository should ideally use "write once" media to archive
       the history of what was placed in the repository, to include a
       snapshot of the current status of applications on endpoints.



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12.  Privacy-Considerations

   The Endpoint Compliance Profile specifically addresses the collection
   of posture data from enterprise endpoints by an enterprise network.
   As such, privacy is not going to often arise as a concern for those
   deploying this solution.

   A possible exception may be the concerns a user may have when
   attempting to connect a personal endpoint (such as a phone or mobile
   endpoint) to an enterprise network.  The user may not want to share
   certain details, such as an endpoint identifier or SWID tags, with
   the enterprise.  The user can configure their NEAC to reject requests
   for this information; however, it is possible that the enterprise
   policy will not allow the user's endpoint to connect to the network
   without providing the requested data.

13.  Change Log

13.1.  -00 to -01

   There are no textual changes associated with this revision.  This
   revision simply reflects a resubmission of the document so that it
   remains in active status.

13.2.  -01 to -02

   Added references to the Software Inventory Message and Attributes
   (SWIMA) for PA-TNC I-D.

   Replaced references to PC-TNC with IF-IMC.

   Removed erroneous hyphens from a couple of section titles.

   Made a few minor editorial changes.

13.3.  -02 to -00

   Edited Absrtact through Figure 2 to remove references to SWIMA, and
   uplevel draft to describe SACM collection over multiple different
   protocols

   Replaced references to SANS with CIS.

   Made a few minor editorial changes.







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14.  References

14.1.  Informative References

   [CIS]      http://www.cisecurity.org/controls/, "CIS Critical
              Security Controls".

   [DSD]      http://www.dsd.gov.au/publications/csocprotect/
              top_4_mitigations.htm, "Top 4 Mitigation Strategies to
              Protect Your ICT System", November 2012.

   [IEEE-802-1ar]
              Institute of Electrical and Electronics Engineers, "IEEE
              802.1ar", December 2009.

   [RFC5209]  Sangster, P., Khosravi, H., Mani, M., Narayan, K., and J.
              Tardo, "Network Endpoint Assessment (NEA): Overview and
              Requirements", RFC 5209, DOI 10.17487/RFC5209, June 2008,
              <https://www.rfc-editor.org/info/rfc5209>.

   [TNC]      Trusted Computing Group, "TCG Trusted Network Connect TNC
              Architecture for Interoperability, Version 1.5", February
              2012.

14.2.  Normative References

   [I-D.ietf-sacm-nea-swid-patnc]
              Schmidt, C., Haynes, D., Coffin, C., and J. Fitzgerald-
              McKay, "Software Inventory Message and Attributes (SWIMA)
              for PA-TNC", draft-ietf-sacm-nea-swid-patnc-00 (work in
              progress), January 2017.

   [I-D.ietf-sacm-terminology]
              Waltermire, D., Montville, A., Harrington, D., and N. Cam-
              Winget, "Terminology for Security Assessment", draft-ietf-
              sacm-terminology-05 (work in progress), August 2014.

   [IF-IMC]   Trusted Computing Group, "TCG Trusted Network Connect TNC
              IF-IMC, Version 1.3", February 2013.

   [IF-IMV]   Trusted Computing Group, "TCG Trusted Network Connect TNC
              IF-IMV, Version 1.4", December 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.




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   [RFC5792]  Sangster, P. and K. Narayan, "PA-TNC: A Posture Attribute
              (PA) Protocol Compatible with Trusted Network Connect
              (TNC)", RFC 5792, DOI 10.17487/RFC5792, March 2010,
              <https://www.rfc-editor.org/info/rfc5792>.

   [RFC5793]  Sahita, R., Hanna, S., Hurst, R., and K. Narayan, "PB-TNC:
              A Posture Broker (PB) Protocol Compatible with Trusted
              Network Connect (TNC)", RFC 5793, DOI 10.17487/RFC5793,
              March 2010, <https://www.rfc-editor.org/info/rfc5793>.

   [RFC6876]  Sangster, P., Cam-Winget, N., and J. Salowey, "A Posture
              Transport Protocol over TLS (PT-TLS)", RFC 6876,
              DOI 10.17487/RFC6876, February 2013,
              <https://www.rfc-editor.org/info/rfc6876>.

   [RFC7632]  Waltermire, D. and D. Harrington, "Endpoint Security
              Posture Assessment: Enterprise Use Cases", RFC 7632,
              DOI 10.17487/RFC7632, September 2015,
              <https://www.rfc-editor.org/info/rfc7632>.

   [Server-Discovery]
              Trusted Computing Group, "DRAFT: TCG Trusted Network
              Connect PDP Discovery and Validation, Version 1.0",
              October 2015.

   [SWID]     "Information technology--Software asset management--Part
              2: Software identification tag", ISO/IEC 9899:1999, 2009.

Authors' Addresses

   Danny Haynes
   The MITRE Corporation
   202 Burlington Road
   Bedford, MA  01730
   USA

   Email: dhaynes@mitre.org


   Jessica Fitzgerald-McKay
   Department of Defense
   9800 Savage Road
   Ft. Meade, Maryland
   USA

   Email: jmfitz2@nsa.gov





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   Lisa Lorenzin
   Pulse Secure
   2700 Zanker Rd., Suite 200
   San Jose, CA  95134
   US

   Email: llorenzin@pulsesecure.net












































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