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SACM                                                  D. Waltermire, Ed.
Internet-Draft                                                      NIST
Intended status: Informational                                 K. Watson
Expires: July 8, 2016                                                DHS
                                                                 C. Kahn
                                                             L. Lorenzin
                                                       Pulse Secure, LLC
                                                               D. Haynes
                                                   The MITRE Corporation
                                                         January 5, 2016


                         SACM Information Model
                  draft-ietf-sacm-information-model-03

Abstract

   This document proposes an information model for SACM.

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
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 8, 2016.

Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.1.  Problem Statement . . . . . . . . . . . . . . . . . . . .   6
       1.1.1.  Referring to an Endpoint  . . . . . . . . . . . . . .   7
       1.1.2.  Dealing with Uncertainty  . . . . . . . . . . . . . .   8
   2.  Conventions used in this document . . . . . . . . . . . . . .   8
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   9
   3.  Information Model Framework . . . . . . . . . . . . . . . . .   9
     3.1.  Containers  . . . . . . . . . . . . . . . . . . . . . . .   9
     3.2.  Attributes  . . . . . . . . . . . . . . . . . . . . . . .   9
     3.3.  Metadata  . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.4.  Relationships . . . . . . . . . . . . . . . . . . . . . .  10
     3.5.  Designation . . . . . . . . . . . . . . . . . . . . . . .  10
     3.6.  Conventions for Modeling Information Model Objects  . . .  10
   4.  Information Model Assets  . . . . . . . . . . . . . . . . . .  10
     4.1.  Asset . . . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.2.  Endpoint  . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.3.  Hardware Component  . . . . . . . . . . . . . . . . . . .  11
       4.3.1.  Hardware Instance . . . . . . . . . . . . . . . . . .  12
     4.4.  Software Component  . . . . . . . . . . . . . . . . . . .  12
       4.4.1.  Software Instance . . . . . . . . . . . . . . . . . .  14
     4.5.  Asset Identity  . . . . . . . . . . . . . . . . . . . . .  14
     4.6.  Relationships . . . . . . . . . . . . . . . . . . . . . .  14
   5.  Information Model Elements  . . . . . . . . . . . . . . . . .  14
     5.1.  Identifying Attributes  . . . . . . . . . . . . . . . . .  17
       5.1.1.  How Known . . . . . . . . . . . . . . . . . . . . . .  17
       5.1.2.  Whether to Include  . . . . . . . . . . . . . . . . .  18
       5.1.3.  IP Address  . . . . . . . . . . . . . . . . . . . . .  18
         5.1.3.1.  Range of Values . . . . . . . . . . . . . . . . .  18
         5.1.3.2.  Meaning . . . . . . . . . . . . . . . . . . . . .  19
         5.1.3.3.  Relationships . . . . . . . . . . . . . . . . . .  19
         5.1.3.4.  Multiplicity  . . . . . . . . . . . . . . . . . .  19
         5.1.3.5.  Stability . . . . . . . . . . . . . . . . . . . .  19
         5.1.3.6.  Accuracy  . . . . . . . . . . . . . . . . . . . .  19
         5.1.3.7.  Data Model Requirements . . . . . . . . . . . . .  20
       5.1.4.  MAC Address . . . . . . . . . . . . . . . . . . . . .  20
       5.1.5.  Hardware Serial Number  . . . . . . . . . . . . . . .  20
         5.1.5.1.  Range of Values . . . . . . . . . . . . . . . . .  20
         5.1.5.2.  Meaning . . . . . . . . . . . . . . . . . . . . .  20
         5.1.5.3.  Multiplicity  . . . . . . . . . . . . . . . . . .  20
         5.1.5.4.  Stability . . . . . . . . . . . . . . . . . . . .  21
         5.1.5.5.  Accuracy  . . . . . . . . . . . . . . . . . . . .  21
         5.1.5.6.  Data Model Requirements . . . . . . . . . . . . .  21
       5.1.6.  Certificate . . . . . . . . . . . . . . . . . . . . .  21



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         5.1.6.1.  Range of values . . . . . . . . . . . . . . . . .  21
         5.1.6.2.  Meaning . . . . . . . . . . . . . . . . . . . . .  21
         5.1.6.3.  Multiplicity  . . . . . . . . . . . . . . . . . .  21
         5.1.6.4.  Stability . . . . . . . . . . . . . . . . . . . .  21
         5.1.6.5.  Accuracy  . . . . . . . . . . . . . . . . . . . .  22
         5.1.6.6.  Data model requirements . . . . . . . . . . . . .  22
       5.1.7.  Public Key  . . . . . . . . . . . . . . . . . . . . .  22
       5.1.8.  Username? . . . . . . . . . . . . . . . . . . . . . .  22
       5.1.9.  Tool-Specific Identifier  . . . . . . . . . . . . . .  22
       5.1.10. Identification of Endpoints where SACM Components
               Reside  . . . . . . . . . . . . . . . . . . . . . . .  22
       5.1.11. Security Considerations . . . . . . . . . . . . . . .  23
     5.2.  Network Interface . . . . . . . . . . . . . . . . . . . .  23
     5.3.  Address . . . . . . . . . . . . . . . . . . . . . . . . .  23
     5.4.  Identity  . . . . . . . . . . . . . . . . . . . . . . . .  24
     5.5.  Location  . . . . . . . . . . . . . . . . . . . . . . . .  25
     5.6.  Endpoint Attribute Assertion  . . . . . . . . . . . . . .  26
       5.6.1.  Form and Precise Meaning  . . . . . . . . . . . . . .  26
       5.6.2.  Asserter  . . . . . . . . . . . . . . . . . . . . . .  26
       5.6.3.  Example . . . . . . . . . . . . . . . . . . . . . . .  27
       5.6.4.  A Use Case  . . . . . . . . . . . . . . . . . . . . .  27
       5.6.5.  Event . . . . . . . . . . . . . . . . . . . . . . . .  27
       5.6.6.  Difference between Attribute and Event  . . . . . . .  27
     5.7.  Attribute-Value Pair  . . . . . . . . . . . . . . . . . .  28
       5.7.1.  Unique Endpoint Identifier  . . . . . . . . . . . . .  29
       5.7.2.  Posture Attribute . . . . . . . . . . . . . . . . . .  29
     5.8.  Evaluation Result . . . . . . . . . . . . . . . . . . . .  30
     5.9.  Report  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     5.10. SACM Component  . . . . . . . . . . . . . . . . . . . . .  31
       5.10.1.  External Attribute Collector . . . . . . . . . . . .  31
       5.10.2.  Evaluator  . . . . . . . . . . . . . . . . . . . . .  32
       5.10.3.  Report Generator . . . . . . . . . . . . . . . . . .  32
     5.11. Organization? . . . . . . . . . . . . . . . . . . . . . .  32
     5.12. Guidance  . . . . . . . . . . . . . . . . . . . . . . . .  33
       5.12.1.  Internal Collection Guidance . . . . . . . . . . . .  33
       5.12.2.  External Collection Guidance . . . . . . . . . . . .  33
       5.12.3.  Evaluation Guidance  . . . . . . . . . . . . . . . .  33
       5.12.4.  Retention Guidance . . . . . . . . . . . . . . . . .  33
       5.12.5.  Reporting Guidance . . . . . . . . . . . . . . . . .  33
     5.13. Endpoint  . . . . . . . . . . . . . . . . . . . . . . . .  34
       5.13.1.  Endpoint Identity  . . . . . . . . . . . . . . . . .  34
       5.13.2.  Software Component . . . . . . . . . . . . . . . . .  34
         5.13.2.1.  Unique Software Identifier . . . . . . . . . . .  35
     5.14. User  . . . . . . . . . . . . . . . . . . . . . . . . . .  35
       5.14.1.  User Identity  . . . . . . . . . . . . . . . . . . .  35
   6.  SACM Usage Scenario Example . . . . . . . . . . . . . . . . .  36
     6.1.  Graph Model for Detection of Posture Deviation  . . . . .  36
       6.1.1.  Components  . . . . . . . . . . . . . . . . . . . . .  36



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       6.1.2.  Identifiers . . . . . . . . . . . . . . . . . . . . .  37
       6.1.3.  Metadata  . . . . . . . . . . . . . . . . . . . . . .  37
       6.1.4.  Relationships between Identifiers and Metadata  . . .  38
     6.2.  Workflow  . . . . . . . . . . . . . . . . . . . . . . . .  38
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  39
     7.1.  Contributors  . . . . . . . . . . . . . . . . . . . . . .  39
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  39
   9.  Operational Considerations  . . . . . . . . . . . . . . . . .  40
   10. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  40
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  40
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  41
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  41
     12.2.  Informative References . . . . . . . . . . . . . . . . .  41
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  47
     A.1.  Changes in Revision 01  . . . . . . . . . . . . . . . . .  47
     A.2.  Changes in Revision 02  . . . . . . . . . . . . . . . . .  48
     A.3.  Changes in Revision 03  . . . . . . . . . . . . . . . . .  48
   Appendix B.  Mapping to SACM Use Cases  . . . . . . . . . . . . .  48
   Appendix C.  Security Automation with TNC IF-MAP  . . . . . . . .  49
     C.1.  What is Trusted Network Connect?  . . . . . . . . . . . .  49
     C.2.  What is TNC IF-MAP? . . . . . . . . . . . . . . . . . . .  49
     C.3.  What is the TNC Information Model?  . . . . . . . . . . .  50
   Appendix D.  Text for Possible Inclusion in the Terminology Draft  51
     D.1.  Terms and Definitions . . . . . . . . . . . . . . . . . .  51
       D.1.1.  Pre-defined and Modified Terms  . . . . . . . . . . .  51
       D.1.2.  New Terms . . . . . . . . . . . . . . . . . . . . . .  51
   Appendix E.  Text for Possible Inclusion in the Architecture or
                Use Cases  . . . . . . . . . . . . . . . . . . . . .  52
     E.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .  52
     E.2.  Core Principles . . . . . . . . . . . . . . . . . . . . .  53
     E.3.  Architecture Assumptions  . . . . . . . . . . . . . . . .  53
   Appendix F.  Text for Possible Inclusion in the Requirements
                Draft  . . . . . . . . . . . . . . . . . . . . . . .  57
     F.1.  Problem Statement . . . . . . . . . . . . . . . . . . . .  57
     F.2.  Problem Scope . . . . . . . . . . . . . . . . . . . . . .  57
   Appendix G.  Text With No Clear Home Yet  . . . . . . . . . . . .  58
     G.1.  Operations  . . . . . . . . . . . . . . . . . . . . . . .  58
       G.1.1.  Generalized Workflow  . . . . . . . . . . . . . . . .  58
     G.2.  From Information Needs to Information Elements  . . . . .  59
     G.3.  Information Model Elements  . . . . . . . . . . . . . . .  59
       G.3.1.  Asset Identifiers . . . . . . . . . . . . . . . . . .  61
         G.3.1.2.  Endpoint Identification . . . . . . . . . . . . .  63
         G.3.1.3.  Software Identification . . . . . . . . . . . . .  64
         G.3.1.4.  Hardware Identification . . . . . . . . . . . . .  67
       G.3.2.  Other Identifiers . . . . . . . . . . . . . . . . . .  67
         G.3.2.1.  Platform Configuration Item Identifier  . . . . .  67
         G.3.2.2.  Configuration Item Identifier . . . . . . . . . .  73
         G.3.2.3.  Vulnerability Identifier  . . . . . . . . . . . .  75



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       G.3.3.  Endpoint characterization . . . . . . . . . . . . . .  75
       G.3.4.  Posture Attribute Expression  . . . . . . . . . . . .  79
         G.3.4.2.  Platform Configuration Attributes . . . . . . . .  79
       G.3.5.  Actual Value Representation . . . . . . . . . . . . .  81
         G.3.5.1.  Software Inventory  . . . . . . . . . . . . . . .  81
         G.3.5.2.  Collected Platform Configuration Posture
                   Attributes  . . . . . . . . . . . . . . . . . . .  82
       G.3.6.  Evaluation Guidance . . . . . . . . . . . . . . . . .  83
         G.3.6.1.  Configuration Evaluation Guidance . . . . . . . .  83
       G.3.7.  Evaluation Result Reporting . . . . . . . . . . . . .  85
         G.3.7.1.  Configuration Evaluation Results  . . . . . . . .  85
         G.3.7.2.  Software Inventory Evaluation Results . . . . . .  87
   Appendix H.  Graph Model  . . . . . . . . . . . . . . . . . . . .  87
     H.1.  Background: Graph Models  . . . . . . . . . . . . . . . .  88
     H.2.  Graph Model Overview  . . . . . . . . . . . . . . . . . .  89
     H.3.  Identifiers . . . . . . . . . . . . . . . . . . . . . . .  89
     H.4.  Links . . . . . . . . . . . . . . . . . . . . . . . . . .  90
     H.5.  Metadata  . . . . . . . . . . . . . . . . . . . . . . . .  90
     H.6.  Use for SACM  . . . . . . . . . . . . . . . . . . . . . .  91
     H.7.  Provenance  . . . . . . . . . . . . . . . . . . . . . . .  91
     H.8.  Extensibility . . . . . . . . . . . . . . . . . . . . . .  91
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  92

1.  Introduction

   This document defines a notional information model for endpoint
   posture assessment.  It describes the information needed to perform
   certain assessment activities.  The scope of the information model is
   to describe the structure of the information carried to realize the
   assessment.  It is meant to be a basis for the development of
   specific data models.  The terms information model and data model
   loosely align with the definitions in RFC3444 [RFC3444].

   The four primary activities to support this information model are:

   1.  Endpoint Identification

   2.  Endpoint Characterization

   3.  Endpoint Attribute Expression/Representation

   4.  Policy evaluation expression and results reporting

   These activities are aimed at the level of the technology that
   performs operations to support collection, evaluation, and reporting.

   Review of the SACM Use Case [RFC7632] usage scenarios show a common
   set of business process areas that are critical to understanding



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   endpoint posture such that appropriate policies, security
   capabilities, and decisions can be developed and implemented.

   For this information model we have chosen to focus on the following
   business process areas:

   o  Endpoint Management

   o  Software Management

   o  Configuration Management

   o  Vulnerability Management

   These management process areas are a way to connect the SACM use
   cases and building blocks [RFC7632] to the organizational needs such
   that the definition of information requirements has a clearly
   understood context. (/wandw).  For more information, Appendix B maps
   the SACM information model to the SACM use cases.

   The SACM information model offers a loose coupling between providers
   and consumers of security information.  A provider can relay what it
   observes or infers, without knowing which consumers will use the
   information, or how they will use it.  A consumer need not know
   exactly which provider generated a piece of information, or by what
   method.

   At the same time, a consumer *can* know these things, if necessary.

   As things evolve, a provider can relay supplemental information.
   Some consumers will understand and benefit from the supplemental
   information; other consumers will not understand and will disregard
   it.

1.1.  Problem Statement

   TODO: revise

   (wandw)SACM requires a large and broad set of mission and business
   processes, and to make the most effective of use of technology, the
   same data must support multiple processes.  The activities and
   processes described within this document tend to build off of each
   other to enable more complex characterization and assessment.  In an
   effort to create an information model that serves a common set of
   management processes represented by the usage scenarios in the SACM
   Use Cases document, we have narrowed down the scope of this
   model.(/wandw) [What does "narrowed down the scope of this model"
   mean? - LL]



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   Administrators can't get technology from disparate sources to work
   together; they need information to make decisions, but the
   information is not available.  Everyone is collecting the same data,
   but storing it as different information.  Administrators therefore
   need to collect data and craft their own information, which may not
   be accurate or interoperable because it's customized by each
   administrator, not shared.  A standard information model enables
   flexibility in collecting, storing, and sharing information despite
   platform differences.

   A way is needed to exchange information that (a) has breadth, meaning
   the pieces of the notation are useful about a variety of endpoints
   and software components, and (b) has longevity, meaning that the
   pieces of the notation will stay useful over time.

   When creating standards, it's not sufficient to go from requirements
   directly to protocol; the standards must eliminate ambiguity in the
   information transported.  This is the purpose of information models
   generally.  The SACM problem space is about integrating many
   information sources.  This information model addresses the need to
   integrate security components, support multiple data models, and
   provide interoperability in a way that is platform agnostic, scales,
   and works over time.

1.1.1.  Referring to an Endpoint

   How to refer to an endpoint is problematic.  Ideally, an endpoint
   would have a unique identifier.  These identifiers would have a one-
   to-one relationship with endpoints.  Every observation of an
   endpoint, or inference about an endpoint would be labeled with its
   identifier.

   However:

   o  An external posture attribute collector typically cannot observe
      the unique identifier directly.  An external posture attribute
      collector should be able to report exactly what it has observed,
      unembellished.  It should not have to *infer* which endpoint it
      has observed; that inference should be leavable to other SACM
      components.  So, SACM cannot require that every observation
      include the unique endpoint identifier.

   o  Internal posture attribute collectors are not present on all
      endpoints.  They are not present on "dumb" devices such as
      Internet of Things (IoT) devices, or on Bring Your Own Device
      (BYOD) devices.  In these cases, *no* observers have direct access
      to the unique endpoint identifier.




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   o  An endpoint identifier is generally subject to cloning, when a
      system image is cloned.  Then it is no longer unique.

   o  Suppose the endpoint identifier is highly clone resistant -- such
      a unique certificate within a trusted platform module TPM.  Even
      so, it is possible to replace all of the software -- for example,
      changing a Windows machine to a Linux machine.  Is it still the
      same endpoint?  For SACM purposes, it isn't really the same
      endpoint.

   So SACM components must be able to put disparate observations
   together and form a picture of an endpoint -- somewhat like a
   detective.  The SACM information model must facilitate this.

1.1.2.  Dealing with Uncertainty

   With many information models, the information is considered certain.
   In SACM, information is not certain.  Attackers may develop
   countermeasures to fool some SACM components.  Attackers may
   compromise some SACM components.

   So the model must let SACM components and humans reason with
   uncertainty.  There are no facts, only assertions.

   SACM components must be able to cross check observations and
   inferences against each other.  They should be able to give weight if
   an observation or inference is corroborated by more than one method.
   Although SACM will probably not prescribe *how* to do this cross
   checking, SACM should provide the components with provenance
   information.

   SACM components must be able to consider the reputation of the
   observer or inferrer.  That reputation should account for the method
   of observing or inferring, the implementer of the SACM component that
   made the observation or inference, and the compliance status of the
   endpoint on which the observation or inference was made.  For
   example, if some observers are found to be vulnerable to a Day 1
   exploit, observations from those observers deserve less weight.  The
   details of reputation technology may be out of scope for SACM.
   However, again, SACM should provide components with provenance
   information.

2.  Conventions used in this document








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2.1.  Requirements Language

   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 [RFC2119].

3.  Information Model Framework

   The SACM information model is structured around a core framework that
   can be easily extended to support the modeling needs for endpoint
   posture assessment.  This section describes the key concepts that
   make up this framework as well as the conventions used to model the
   different information model objects in the following sections.

3.1.  Containers

   TODO: Explain containers at a conceptual level and how they are the
   mechanism by which attributes and/or other containers can be
   logically grouped together to create more complex models.  Additional
   information about containers can be modeled using metadata.
   QUESTION: We are not sure "container" is the correct term to use here
   as it implies a hierarchy.  Alternative terms might be "construct",
   "object", or "class".  This is something that needs to be decided.

3.2.  Attributes

   TODO: Explain attributes at a conceptual level and how they are used
   to model posture attribute information on an endpoint.  At a minimum,
   an attribute must have a name and a value.  However, there is work
   currently being done in the Endpoint ID Design Team to prepare a
   proposal for the working group to explain how triples (subject,
   predicate, object) could be used to model attributes in the
   information model.  Additional information about attributes can be
   modeled using metadata.

3.3.  Metadata

   TODO: Explain metadata at a conceptual level and how it can be used
   to provide additional information about containers and attributes.
   We should be providing enough information so that SACM users can
   determine provenance (e.g. source of origin, time of collection,
   observation, reporting, etc.) and use it when sharing and evaluating
   posture attribute information.








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3.4.  Relationships

   TODO: Define what a relationship is.  At the end of the day, we want
   to be able to describe the relationships between assets, endpoints,
   and attributes.  QUESTION: Are relationships just metadata?  Lisa's
   notes have some information on relationships:
   https://mailarchive.ietf.org/arch/msg/sacm/
   kWxlnboHAXD87cned9WavwPZy5w

3.5.  Designation

   TODO: In the IETF, there are privacy concerns with respect to
   endpoint identity and monitoring.  As a result, the Endpoint ID
   Design Team proposes that "endpoint identity" be changed to "endpoint
   designation".  Designation attributes can be used to correlate
   endpoints, information about endpoints, events, etc.  NOTE:
   Designation attributes are just those that are mandatory-to-
   implement.  In practice, organizations may need to select additional
   attributes beyond the mandatory-to-implement attributes to
   successfully identify an endpoint on their network.  Operational and
   privacy concerns will be covered in Operational Considerations and
   Privacy Considerations sections respectively.

3.6.  Conventions for Modeling Information Model Objects

   TODO: The working group needs to select the conventions that will be
   used to model the different objects defined in the information model.
   Members of the Endpoint ID Design Team are looking into different
   examples of how other working groups have modeled the objects in
   their information models so that the working can select one that
   makes the most sense for SACM.  Once conventions have been selected,
   they should be documented here for future reference.

4.  Information Model Assets

   TODO: Explain the different SACM assets.  Right now, we have
   distilled this down to an endpoint, hardware, software, and identity.
   Previously, this diagram also included account, location, address,
   and network inteface, but, these things are not assets and can either
   be consolidated into one of the existing asset types (e.g. network
   interface => hardware, account => identity, etc.) or are just
   metadata about the assets (e.g. location => endpoint).  We should
   also explain the types of assets below rather than just referencing
   out to the Terminology draft.

   TODO: The figure below needs to be updated to show the relationships
   between the different types of assets.




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           +---------+*______in>_______*+-----+
           |Hardware |                  |!   !|
           |Component|   +---------+    |!   !|
           +---------+   |Software |in> |!   !|
               1|        |Component|____|!   !|
                |        +---------+*  *|!   !|
                |            1|         |!   !|
                |            *|         |     |       +----------+
                |        +---------+    |End- |*_____*| Identity |
               *|        |Software |in> |point| acts  +----------+
           +---------+   |Instance |____|     | for>
           |Hardware |   +---------+*  1|!   !|
           |Instance |__________________|!   !|
           +---------+*      in>       1|!   !|
                                        |!   !|
                                        |!   !|____
                                        |!   !|0..1|
                                        +-----+    |
                                           |*      |
                                           |_______|
                                              in>


                      Figure 1: Model of an Endpoint

4.1.  Asset

   TODO: Define Asset here in the context of the information model.

4.2.  Endpoint

   TODO: Define an Endpoint asset.  Explain how it is made up of HW
   components, SW components, asset identity, etc.  Take relevant
   information from the

   An endpoint is the hollow center of the model.  An endpoint is an
   abstract ideal.  Any endpoint attribute assertion that mentions an
   endpoint mentions it by specifying identifying attributes.  Even if
   there is one preferred endpoint identity, that is modeled as an
   identity.  We do not anticipate any AVP whose attribute type is
   "endpoint".

4.3.  Hardware Component

   TODO: Define a Hardware Component asset.  Explain how it is things
   like motherboards, network cards, etc.





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   Hardware components may also be assets and/or harmful.  For example,
   a USB port on a system may be disabled to prevent information flow
   into our out of a particular system; this provides an additional
   layer of protection that can complement software based protections.
   Other such assets may include access to or modification of storage
   media, hardware key stores, microphones and cameras.  Like software
   assets, we can consider these hardware components both from the
   perspective of (a) an asset that needs protection and (b) an asset
   that can be compromised in some way to do harm.

   A data model MAY designate a hardware component by its manufacturer
   and a part number.

4.3.1.  Hardware Instance

   A hardware instance is just an instance of a particular component.

   A data model MUST support the following relationships:

   o  A hardware instance is an "instance of" a hardware component.

   o  A hardware instance is "in" an endpoint.

   Hardware instances may need to be modeled because (a) an endpoint may
   have multiple instances of a hardware component, (b) a hardware
   instance may be compromised, whereas other instances may remain
   intact.

   A data model MAY designate a hardware instance by its component and a
   unique serial number.

4.4.  Software Component

   TODO: Define a Software Component asset.  Explain how it is the
   software installed on the endpoint including the operating system.

   An endpoint contains and runs software components.

   Relationship:

   o  If an endpoint has an instance of a software component, we say
      that the software component is "in" the endpoint.  This is a
      shorthand.

   Some software components are assets.  "Asset" is defined in RFC4949
   [RFC4949] as "a system resource that is (a) required to be protected
   by an information system's security policy, (b) intended to be




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   protected by a countermeasure, or (c) required for a system's
   mission."

   An examination of software needs to consider both (a) software assets
   and (b) software that may do harm.  A posture attribute collector may
   not know (a) from (b).  It is useful to define Software Component as
   the union of (a) and (b).

   Examples of Software Assets:

   o  An application

   o  A patch

   o  The operating system kernel

   o  A boot loader

   o  Firmware that controls a disk drive

   o  A piece of JavaScript found in a web page the user visits

   Examples of harmful software components:

   o  A malicious entertainment app

   o  A malicious executable

   o  A web page that contains malicious JavaScript

   o  A business application that shipped with a virus

   Software components SHOULD be disjoint from each other.  In other
   words, software componennts SHOULD be so defined that a given byte of
   software on an endpoint belongs to only one software component.

   Different versions of the same piece of software MUST be modeled as
   different components.  Software versioning is not built into the
   information model.

   Each separately installable piece of software SHOULD be modeled as a
   component.  Sometimes it may be better to divide more finely: what an
   installer installs MAY be modeled as several components.

   A data model MAY identify a software component by parts of an ISO
   SWID tag.





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4.4.1.  Software Instance

   Each copy of a piece of software is called a software instance.  The
   configuration of a software instance is regarded as part of the
   software instance.  Configuration can strongly affect security
   posture.

   A data model MUST support the following relationships:

   o  A software instance is an "instance of" a software component.

   o  A software instance is "in" an endpoint.

   A data model MAY use ISO SWID tags to describe software instances.

4.5.  Asset Identity

   TODO: Define an Asset Identity asset.  Explain how it is things like
   user, device, etc.  where certificates, usernames, etc. come into
   place since they are not really hardware or software.  NOTE: Make
   sure it is clear that this is not identity in the sense of what we
   have been saying endpoint identity (now designation).

4.6.  Relationships

   TODO: Define the relationships between assets (endpoints, hardware,
   software, etc.).  These will depicted in the overview diagram.

5.  Information Model Elements

   TODO: Define specific containers, attributes, and metadata.  We may
   want to consider adding small diagrams showing the relationships
   between each (see Lisa's notes:
   https://mailarchive.ietf.org/arch/msg/sacm/
   kWxlnboHAXD87cned9WavwPZy5w).  This may be too much work, but, not
   sure yet.

   The SACM Information Model contains several elements of the
   architecture, including:

   o  SACM Components, which may be Collectors, Evaluators, etc.
      Collectors may be internal (performed within the endpoint itself)
      or external (performed outside of the endpoint, such as by a
      hypervisor or remote sensor)

   o  Guidance, which tells SACM components what to do

   o  Posture, in the form of posture attributes and evaluation results



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   o  Additional information about the endpoint, such as a
      representation of a software component, endpoint identity, user
      identity, address, location, and authorization constraining the
      endpoint

   The SACM Information Model does not (in this draft) specify how long
   information is retained.  Historical information is modeled the same
   way as current information.  Historical information may be
   represented differently in an implementation, but that difference
   would be in data models, not in the information model.

   Figure 2 introduces the endpoint attributes and their relationships.


   +---------+*____in>______*+-----+
   |Hardware |               |!   !|
   |Component| +---------+   |!   !|      +--------+*______________
   +---------+ |Software |in>|!   !|*____*|Location|_________   <in|
       1|      |Component|___|!   !|  in> +--------+*  <in  *|     |
        |      +---------+* *|!   !|                    +-------+  |
        |          1|        |!   !|                    |Account|  |
        |          *|        |     |      +----------+  +-------+  |
        |     +--------+     |End- |*____*| Identity |______|0..1  |
       *|     |Software|in>  |point| acts +----------+* belongs    |
   +--------+ |Instance|_____|     | for>   0..1|^        to>      |
   |Hardware| +--------+*   1|!   !|            |acts              |
   |Instance|________________|!   !|           *|for               |*
   +--------+*    in>       1|!   !|______+---------+          +-------+
                             |!   !|1 <in *|Network  |1_______*|Address|
                             |!   !|____  |Interface| <bound   +-------+
                             |!   !|0..1| +---------+   to
                             +-----+    |   *|   |0..1
                                |*      |    |___|
                                |_______|     in>
                                    in>


                      Figure 2: Model of an Endpoint

   ISSUE (CEK): we agreed to remove location and account from the model,
   did we not?  TODO: Remove Network Interface, Location, Address, and
   Account from this diagram if we end up removing the corresponding
   sections from the information model.

   Figure 3 is the core of the information model.  It represents the
   information elements and their relationships.





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            +-----+            +---------+
            | AVP |____________|Endpoint |
            +-----+1..*       1|Attribute|
                               |Assertion|
                               +---------+
                                 |*                     +-------+
                                 |                      |Summary|
                                 |                      +-------+
                                 |produced-by               *|
                                 |V                          |
                                1|                           |
    +--------+              +-----------+                    |
    |        |              | SACM      |____________________|
    |Guidance|              | Component |1      <produced-by
    +--------+*____________1+-----------+
               <produced-by


                      Figure 3: Information Elements

   Figure 4 is a potential alternative structure for assertions.  It is
   inspired by triple stores.  See http://www.w3.org/TR/2014/REC-rdf11-
   concepts-20140225/.

    +-----+______________+---------+                +---------+
    | AVP |1  <subject  *|assertion|________________|predicate|
    |     |______________|         |*  predicate>  1+---------+
    +-----+1  <object   *+---------+
       1^                     |*
        |_____________________|
               <asserter

                  Figure 4: Information Elements, Take 2

   Note: UML 2 is specified by [UML].

   TODO: update text to match new figure:

   Need to be clear in the description that ???

   For some of the relationships, will need some language and guidance
   to the interfaces and relationships we expect to have happen, MUSTs
   and SHOULDs, as well as explaining the extensibility that other
   relationships can exist, show examples of how that can happen.
   Others that we haven't thought of yet, might be added by another RFC
   or in another way





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5.1.  Identifying Attributes

   TODO: Need to rename this section to align with new "designation"
   term.

   Identifying attributes let a consumer identify an endpoint, for two
   purposes:

   o  To tell whether two endpoint attribute assertions concern the same
      endpoint (This is not simple, as Section 1.1.1 explains.)

   o  To respond to compliance measurements, for example by reporting,
      remediating, and quarantining (SACM does not specify these
      responses, but SACM exists to enable them.)

   Out of scope of this section: *classifying* an endpoint so as to
   apply appropriate collection guidance to it.  We don't call this
   "identification".

5.1.1.  How Known

   Each attribute-value pair or triple MUST be marked with how the
   provider knows.  There MUST be at least one marking.  The possible
   markings follow.

      "Self" means that the endpoint furnished the information: it is
      self-reported.  "Self" does not (necessarily) mean that the
      provider runs on the the monitored endpoint.  Self-reported
      information is generally subject to the Lying Endpoint Problem.
      (TODO: citation)

      "Authority" means that the provider got the information, directly
      or indirectly, from an authority that assigned it.  For example,
      the producer got an IP-MAC association from a DHCP server (or was
      itself the DHCP server).

      "Observation" means that the provider got the information from
      observations of network traffic.  For example, the producer saw
      the source address in an IP packet.

      "Verification" means that the provider has verified the
      information.  For example:

      *  The provider does IP communication with the endpoint and knows
         the IP address with which it communicates.

      *  The provider makes an SSH connection to the endpoint and knows
         the endpoint's public key by virtue of authenticating it.



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      *  The monitored endpoint is a virtual machine and the provider
         knows by peeking into it.

   TODO: Explain security considerations and how consumers are meant to
   use these markings.

5.1.2.  Whether to Include

   When publishing an endpoint attribute assertion, the provider MUST
   publish at least all common identifying AVPs that it knows through
   verification.  If the provider knows none through verification but it
   knows at least one in another way, it MUST publish at least one.  The
   provider SHOULD publish all common identifying AVPs it knows.

5.1.3.  IP Address

5.1.3.1.  Range of Values

   MUST be an IPv4 or IPv6 address, and optionally a scope string.  MUST
   NOT be a broadcast, multicast, or loopback address.

   An IPv4 address MUST conform to [RFC0791], section 3.2.

   An IPv6 address MUST conform to [RFC3587].  SHOULD NOT be a link-
   local address.

   Scope string: an administratively assigned string denoting the IP
   routing domain.  Implementations MUST support this.  Administrators
   may use it to avoid ambiguity, for example if network address
   translation (NAT) is in use.

   ISSUE (Jim Schaad): Scope strings are interesting.  However does this
   imply a potential need to create a new DHCP item so that it can be
   sent out to a device for reporting back?  Is there such a string
   already?

   (Cliff): Scope strings are like administrative-domain in IF-MAP.  It
   would solve many problems if DHCP servers could provide this string
   to endpoints and to observers.  I am not sure whether there is a
   standard DHCP option that fills the bill or not.  I am not sure how
   easily application software can get the DHCP options from the
   underlying OS.  But this is worth exploring.

   (Jim): We may need to look at what happens if a scope identifier is
   either not set or not available.  I am thinking of the virtual
   network that is NATed on my machine.  If those VMs reported [on
   themselves] then the network configuring systems may not know about




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   that VM and there would not necessarily be a reasonable scope string
   to report for it.

5.1.3.2.  Meaning

   Throughout the time interval of the AVP, the endpoint had the right
   to use, or was communicating using, the specified IP address.

5.1.3.3.  Relationships

   A network profiler might know an endpoint's address and something
   about the software running on the endpoint.  The profiler might know
   nothing else.  So data models MUST support an endpoint attribute
   assertion relating the IP address to a set of software components.

   A data model MUST support the following relationships:

   o  An address is "bound to" a network interface.

   o  An address is considered "bound to" an endpoint just if the
      address is "bound to" an interface that is "in" the endpoint.

   o  An address may be "in" one or more locations.  (DELETE?)

5.1.3.4.  Multiplicity

   An endpoint attribute assertion MAY contain one or more IP addresses.

   An IP address may be used by more than one endpoint at a time,
   largely because of Network Address Translation (NAT).  Where
   practical, a scope string SHOULD be included, to disambiguate.

   In practice, an IP address can be used by only one endpoint in an IP
   routing domain at a time.

5.1.3.5.  Stability

   The stability of IP address assignments varies widely.  Some
   assignments are persistent, some volatile.  The time interval of the
   AVP MUST NOT reach into the future, not even if (for example) the
   DHCP lease is infinite.

5.1.3.6.  Accuracy

   For IP addresses that a provider knows by observation or
   verification:

   o  Network Address Translation (NAT, RFC2663) is a pitfall.



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   o  The provider MUST NOT include an IP address that the provider
      knows to be a translated address.

   o  The provider SHOULD be configurable with a set of IP address
      blocks to be excluded.  Address blocks set aside for NAT devices
      SHOULD be excluded, by administrators for example.

   o  ISSUE: In a later SACM version, it would be good to overcome this,
      by publishing the association between the internal and external
      address-port combinations.

   For IP addresses that a provider knows by observation or
   verification, IP address spoofing is a pitfall.  Network
   administrators SHOULD take countermeasures.  Ingress filtering
   (RFC3704) is one.  DHCP snooping is another: many Network Access
   Devices can confine endpoints to IP addresses assigned by authorized
   DHCP servers.

5.1.3.7.  Data Model Requirements

   All SACM data models MUST support this entire subsection.

5.1.4.  MAC Address

   TODO

5.1.5.  Hardware Serial Number

5.1.5.1.  Range of Values

   MUST be a vendor ID string and a serial number string string.  The
   vendor ID string MAY be empty, a URI, or a vendor number.

5.1.5.2.  Meaning

   Throughout the time interval of the AVP, the endpoint had a hardware
   component by the indicated manufacturer and having the specified
   serial number.

5.1.5.3.  Multiplicity

   An endpoint may have any number of hardware instances, each with a
   different serial number.  An endpoint attribute assertion may contain
   AVPs for any subset of the hardware instances.

   Vendors generally ensure that each serial number goes to only one
   hardware instance.




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5.1.5.4.  Stability

   Each hardware component is immutably associated with a hardware
   serial number.  But hardware can be replaced or removed.  As endpoint
   attributes, hardware serial numbers are *persistent* but not
   *immutable*.

5.1.5.5.  Accuracy

5.1.5.6.  Data Model Requirements

   All SACM data models MUST support this entire subsection.

5.1.6.  Certificate

5.1.6.1.  Range of values

   MUST be X.509 certificate, per [RFC5280].

5.1.6.2.  Meaning

   Throughout the time interval of the AVP, the endpoint had the private
   key corresponding to the specified certificate.

   Throughout the time interval, the certificate was valid: it had a
   valid certificate chain from a CA certificate that the asserter
   trusted; every certificate in the chain was time-valid; no
   certificate in in the chain (excluding the CA certificate) was
   revoked.  ISSUE (CEK): Do we want to get this PKI-ish?  If so, would
   we include the CA certificate as well?

5.1.6.3.  Multiplicity

   An endpoint may use, or have the right to use, one or more
   certificates.

   Some certificates may be used on more than one endpoint.  Other
   certificates are (by intent) bound to a single endpoint.  ISSUE
   (CEK): Is there a standard way to distinguish the two?  We could
   perhaps provide a configurable criterion, as an information element.
   Should we?

5.1.6.4.  Stability

   Certificates are replaced, due to expiration and other reasons.  By
   and large, they are not replaced often.  A year is a typical
   interval.  In sum, they are persistent.




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   A private key is baked into hardware is almost immutable.  But again,
   hardware can be replaced.

5.1.6.5.  Accuracy

   If a certificate is known by verification, the attribute is highly
   accurate.

5.1.6.6.  Data model requirements

   All SACM data models MUST support this entire subsection.

5.1.7.  Public Key

   TODO

5.1.8.  Username?

   ISSUE (CEK): If a user certificate can be an identifying attribute,
   why not a username also?  At an earlier stage of our discussions,
   usernames were considered common identifying attributes.  Did we
   decide they should not be?  Or just forget them?

   Many endpoints do not have client certificates.  An authenticated
   username is a useful clue for identifying such an endpoint.  I log in
   only to a handful of personal endpoints.  I also present my username
   and password to many multi-user servers.  We would have to
   distinguish personal endpoints from server endpoints somehow.

5.1.9.  Tool-Specific Identifier

   TODO

   TODO: "Tool-specific identifier" suggests that two tools could never
   agree on a tool-specific identifier.  But a community may agree on an
   identifier notation, and might even create a formal standard.  All
   that's important is that each of these attributes has a type and
   meaning *not* specified by the SACM internet drafts.  "Vendor-
   specific identifier?"  "Custom identifier?"

5.1.10.  Identification of Endpoints where SACM Components Reside

   Every information element needs identifying attributes of its
   producer's endpoint.  (TODO: Provide normative language.  SHOULD?
   MUST?)

   Specifically, in an endpoint attribute assertion, we need identifying
   attributes of the asserter's endpoint.  If the asserter is external,



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   the assertion will contain identifying attributes of two endpoints.
   (TODO: Discuss what this information is for.)

5.1.11.  Security Considerations

   Effects of misidentification

   Things that can cause misidentification

   How minimize misidentification

5.2.  Network Interface

   An endpoint generally has at least one network interface.

   Interfaces nest.  A virtual interface can nest in a physical
   interface.

   A data model MUST support the following relationships:

   o  A network interface is "in" an endpoint.

   o  A network interface is "in" another network interface; this is for
      a nested interface.  CEK: And this allows representing compliance
      policies that are worthwhile.  But is this too advanced for the
      initial set of SACM RFCs?

   o  A network interface "acts for" an identity.  This occurs, for
      example, when the network interface is online because of
      successful 802.1X.  An internal collector may be aware of the
      identity.  An external collector (such as a RADIUS server
      [RFC3580]) will be aware of the identity.

5.3.  Address

   TODO: DELETE THIS SECTION.  ISSUE (CEK): Do we still want to model
   layer 4 addresses?

   An address SHALL BE any of:

   o  A layer 2 address; a data model MUST support MAC addresses, and
      MAY support others

   o  A layer 3 address; a data model MUST support IPv4 and IPv6
      addresses, and MAY support others






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   o  A layer 4 address; a data model MUST support an IP-address-
      protocol-port combination, where protocol is TCP or UDP.  It MAY
      support others

   Addresses from other layers may be added in the future.

   These addresses are not necessarily globally unique.  Therefore, a
   data model SHOULD allow an address to be qualified with a scope.

   o  A data model SHOULD allow qualifying a MAC address with its
      layer-2 broadcast domain.  This MAY take the form of a VLAN ID and
      an administratively assigned string denoting the LAN.

   o  A data model SHOULD allow qualifying an IP address with an
      administratively assigned string denoting the IP routing domain.

   A data model MUST support the following relationships:

   o  An address is "bound to" a network interface.

   o  An address is considered "bound to" an endpoint just if the
      address is "bound to" an interface that is "in" the endpoint.

   o  An address may be "in" one or more locations.

5.4.  Identity

   TODO: Delete this section?

   An identity is the non-secret part of a credential.  Examples are a
   username, an X.500 distinguished name, and a public key.  Passwords,
   private keys, and other secrets are not considered part of an
   identity.

   A data model MUST support the following relationships:

   o  An endpoint may "act for" an identity.  This SHALL mean that the
      endpoint claims or proves that it has this identity.  For example,
      if the endpoint is part of an Active Directory domain and Alice
      logs into the endpoint with her AD username (alice) and password,
      the endpoint "acts for" alice.  An endpoint MAY "act for" more
      than one identity, such as a machine identity and a user identity.

   o  A identity may "belong to" an account.  For example, an enterprise
      may have a database that maps identities to accounts.  CEK: Is
      this relevant?  I don't see how we'd use the notion of an account
      in identifying an endpoint or in specifying compliance
      measurements to be taken.



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5.5.  Location

   TODO: Delete this section?

   Location can be logical or physical.  Location can be a clue to an
   endpoint's identity.

   A data model MUST support the following relationships:

   o  One or more endpoints may be "in" a location

   o  A location may be "in" one or more locations

   o  A network address may be "in" a location

   o  An account may be "in" a location; this would happen if the
      account represents a user, and a physical access control system
      reports on the user's location

   Examples of location:

   o  The switch, access point, VPN gateway, or cell tower to which the
      endpoint is linked

   o  The switch port where the endpoint is plugged in

   o  The location of the endpoint's IP address in the network topology

   o  The geographic location of the endpoint (which is often self-
      reported)

   o  A user location (may be reported by a physical access control
      system)

   CEK: The last three examples seem too advanced for the first set of
   SACM RFCs.  I do not know a notation that would be interoperable and
   useful for endpoint identification.  Should we drop them?

   CEK: If we do drop them, all we have left is the device and port at
   which the endpoint is linked to the network.  Maybe we should regard
   that as a kind of address.

   A data model MUST support switch + port number, access point, and VPN
   gateway as locations.  The other examples are optional.

   More than one of kind of location may pertain to an endpoint.
   Endpoint has a many-to-many relationship with Location.




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5.6.  Endpoint Attribute Assertion

   TODO: Integrate into the Section 3 as appropriate.

5.6.1.  Form and Precise Meaning

   An endpoint attribute assertion has:

   o  One or more attribute-value pairs (AVPs)

   o  Time intervals over which the AVPs hold

   o  Endpoint uniquely identified?  True or false

   o  Provenance, including:

      *  The SACM component that made the assertion

      *  Information about the method used to derive the assertion

   It means that over the specified time interval, there was an endpoint
   for which all of the listed attribute-value pairs were true.

   If the "Endpoint uniquely identified" is true, the set of attributes-
   value pairs together make this assertion apply to only one endpoint.

   The attributes can include posture attributes and identification
   attributes.  The model does not make a rigid distinction between the
   two uses of attributes.

   Some of the attributes may be multi-valued.

   One of the AVPs may be a unique endpoint identifier.  Not every
   endpoint will have one.  If there is one, the SACM component that
   produces the Endpoint Attribute Assertion will not necessarily know
   what it is.

5.6.2.  Asserter

   An Endpoint Attribute Assertion may come from an attribute collector
   or an evaluator.  It may come from a SACM component that derives it
   from out-of-band sources, such as a physical inventory system.  A
   SACM component may derive it from other Endpoint Attribute
   Assertions.







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5.6.3.  Example

   For example, an attribute assertion might have these attribute-value
   pairs:

      mac-address = 01:23:45:67:89:ab

      os = OS X

      os-version = 10.6.8

   This asserts that an endpoint with MAC address 01:23:45:67:89:ab ran
   OS X 10.6.8 throughout the specified time interval.  A profiler might
   have provided this assertion.

5.6.4.  A Use Case

   For example, Endpoint Attribute Assertions should help SACM
   components to track an endpoint as it roams or stays stationary.
   They must track endpoints because they must track endpoints' postures
   over time.  Tracking of an endpoint can employ many clues, such as:

      The endpoint's MAC address

      The authenticated identity (even if it identifies a user)

      The location of the endpoint and the user

5.6.5.  Event

   An event is represented as a Posture Attribute Assertion whose time
   interval has length zero.

   Some potential kinds of events are:

   o  A structured syslog message [RFC5424]

   o  IF-MAP event metadata [TNC-IF-MAP-NETSEC-METADATA]

   o  A NetFlow message [RFC3954]

5.6.6.  Difference between Attribute and Event

   Author: Henk Birkholz

   "Attribute" and "event" are often used fairly interchangeably.  A
   clear distinction makes the words more useful.




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   An *attribute* tends not to change until something causes a change.
   In contrast, an *event* occurs at a moment in time.

   For a nontechnical example, let us consider "openness" as an
   attribute of a door, with two values, "open" and "closed".  A closed
   door tends to stay closed until something opens it (a breeze, a
   person, or a dog).

   The door's opening or closing is an event.

   Similarly, "Host firewall enabled" may be modeled as a true/false
   attribute of an endpoint.  Enabling or disabling the host firewall
   may be modeled as an event.  An endpoint's crashing also may be
   modeled as an event.

   Although events are not attributes, we use one kind of information
   element, the "Endpoint Attribute Assertion", to describe both
   attributes and events.

5.7.  Attribute-Value Pair

   TODO: Integrate into the Section 3 as appropriate.

   The set of attribute types must be extensible, by other IETF
   standards, by other standards groups, and by vendors.  How to express
   attribute types is not defined here, but is left to data models.

   The value may be structured.  For example, it may something like XML.

   The information model requires a standard attribute type (or possibly
   more than one) for each box in Figure 2:

   o  Hardware Component: the value identifies the hardware type.  For
      example, it may consist of the make and model number.

   o  Hardware Instance: the value, together with the Hardware Component
      value, uniquely identifies the hardware instance.  For example, it
      may be a manufacturer-assigned serial number.  This notion might
      not apply to all virtual hardware components.

   o  Software Component: the value identifies a unit of software.  Each
      installable piece of software should be separately identifiable.
      For example, this might be a Software Identifier (SWID).
      Therefore, a software inventory for an endpoint should be
      expressed as an Endpoint Attribute Assertion.

   o  Software Instance: the value describes how the software component
      is installed and configured.



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   o  Endpoint: The value is a unique endpoint identifier.

   o  Location

   o  Identity: The value is the non-secret part of a credential.  For
      example, it may be a certificate, or just a subject Distinguished
      Name extracted from a certificate.  It may be a username.

   o  Network Interface: TBD

   o  User: [cek: Do we want this?  If one user uses different
      credentials at different times, do we think SACM components will
      need know that it's the same user?]

   o  Address: The value is an IP, MAC, or other network address,
      possibly qualified with its scope.

5.7.1.  Unique Endpoint Identifier

   An organization should try to uniquely identify and label an
   endpoint, whether the endpoint is enrolled or is discovered in the
   operational environment.  The identifier should be assigned by or
   used in the enrollment process.

   Here "unique" means one-to-one.  In practice, uniqueness is not
   always attainable.  Even if an endpoint has a unique identifier, an
   attribute collector may not always know it.

   If the attribute type of an AVP is "endpoint", the value is a unique
   identifier of the endpoint.

5.7.2.  Posture Attribute

   Some AVPs will be posture attributes.

   See the definition in the SACM Terminology for Security Assessment
   [I-D.ietf-sacm-terminology].

   Some potential kinds of posture attributes are:

   o  A NEA posture attribute (PA) [RFC5209]

   o  A YANG model [RFC6020]

   o  An IF-MAP device-characteristics metadata item
      [TNC-IF-MAP-NETSEC-METADATA]





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5.8.  Evaluation Result

   Evaluation Results (see [I-D.ietf-sacm-terminology]) are modeled as
   Endpoint Attribute Assertions.

   An Evaluation Result derives from one or more other Endpoint
   Attribute Assertions.

   An example is: a NEA access recommendation [RFC5793]

   An evaluator may be able to evaluate better if history is available.
   This is a use case for retaining Endpoint Attribute Assertions for a
   time.

   An Evaluation Result may be retained longer than the Endpoint
   Attribute Assertions from which it derives.  (Figure 2 does not show
   this.)  In the limiting case, Endpoint Attribute Assertions are not
   retained.  When as an Endpoint Attribute Assertion arrives, an
   evaluator produces an Evaluation Result.  These mechanics are out of
   the scope of the Information Model.

5.9.  Report

   ISSUE (CEK): Should we take modeling of reports out of scope?  It is
   clear that reports are needed.  But is a *standard* for reports
   needed, and does it deserve our priority?  Endpoint ID Design Team:
   Yes, it should be removed.

   TODO: This should be removed if the working group decides that
   reports are out of scope for SACM.

   An Endpoint Attribute Assertion concerns a single endpoint.
   Assertions about a set of endpoints are also needed -- for example,
   for trend analysis and for reports read by humans.  These assertions
   are termed "reports".  SACM components will consume Endpoint
   Attribute Assertions and generate reports.

   A report contains its provenance, with the same form and meaning as
   the provenance of an Endpoint Attribute Assertion.

   A Report summarizes:

   o  Endpoint Attribute Assertions, which may include Evaluation
      Results

   o  Other Reports

   A Report may routine or ad hoc.



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   Some reports may be machine readable.  Machine readable reports may
   be consumable by SACM components and by automatic response systems
   (not specified by SACM).

5.10.  SACM Component

   Although SACM components are mainly covered by the SACM architecture,
   we have some remarks.  TODO: Move them to the architecture document?

   ISSUE (CEK): Why do we need information elements that model SACM
   compoments?

5.10.1.  External Attribute Collector

   An external collector is a collector that observes endpoints from
   outside. [kkw-many of these [collectors] are actually configured and
   operated to manage assets for reasons other than posture assessments.
   it is critical to bring them into this, so i like it...but does it
   matter if the [collector] isn't intended to support posture
   assessment, but happens to have information that can be used by
   posture assessment collection consumers? do we lump them together
   with collectors that are intended to support posture assessment but
   run external to the endpoint?] [jmf: ditto.  The exampled below are
   of things that would perform external collection].

   [cek-to kkw's comment, I think the purpose here is to capture their
   contribution to continuous monitoring.  I don't see the need to
   separate things whose primary job is monitoring from things whose
   primary job is something else.  Is there a need?]

   [cek-to jmf's comment, that is what they are examples of; is a text
   change needed?]

   Examples:

   o  A RADIUS server [RFC3580] whereby an endpoint has logged onto the
      network

   o  A network profiling system, which discovers and classifies network
      nodes

   o  A Network Intrusion Detection System (NIDS) sensor

   o  A vulnerability scanner

   o  A hypervisor that peeks into the endpoint, the endpoint being a
      virtual machine




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   o  A management system that configures and installs software on the
      endpoint

5.10.2.  Evaluator

   An evaluator can consume endpoint attribute assertions, previous
   evaluations of posture attributes, or previous reports of evaluation
   results. [kkw-i don't think this conflicts with the definition in the
   terminology doc re: that evaluation tasks evaluate posture
   attributes.]

   [cek-I like the change.  I think it *does* require a change in the
   terminology doc, though.]

   Example: a NEA posture validator [RFC5209]

   [jmf- a NEA posture validator is not an example of this definition.
   A NEA posture assessment is, maybe?]

   [cek-Why isn't a NEA posture validator an example?]

5.10.3.  Report Generator

   A report generator makes reports based on:

   o  Endpoint Attribute Assertions, including Evaluation Results

   o  Other Reports (a weekly report may be created from daily reports)

   It may summarize data continually, as the data arrives.  It also may
   summarize data in response to an ad hoc query.

   TODO: This should be removed if the working group decides that
   reports are out of scope for SACM.

5.11.  Organization?

   [kkw-from a reporting standpoint there needs to be some concept like
   organization or system. without this, there is no way to produce
   result reports that can be acted upon to provide the insight or
   accountability that almost all continuous monitoring instances are
   trying to achieve. from a scoring or grading standpoint, an endpoint
   needs to be associated with exactly one organization or system. it
   can have a many to many relationship with other types of results
   reporting "bins". is this important to include here? we had
   organization as a core asset type for this reason, so i think it is a
   key information element. but i also know that i do not want to define
   all the different reporting types, so i am unsure.]



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   [cek-I had not thought of this at all.  Would it make sense to treat
   the organization and the bins as part of the guidance for creating
   reports?  Maybe not.  We should discuss.]

5.12.  Guidance

   [jmf- the guidance sections need more detail. . .]

   [cek - What is missing?  We would welcome a critique or text.]

   Guidance is generally configurable by human administrators.

5.12.1.  Internal Collection Guidance

   An internal collector may need guidance to govern what it collects
   and when.

5.12.2.  External Collection Guidance

   An external collector may need guidance to govern what it collects
   and when.

5.12.3.  Evaluation Guidance

   An evaluator typically needs Evaluation Guidance to govern what it
   considers to be a good or bad security posture.

5.12.4.  Retention Guidance

   A SACM deployment may retain posture attributes, events, or
   evaluation results for some time.  Retention supports ad hoc
   reporting and other use cases.

   If information is retained, retention guidance controls what is
   retained and for how long.

   If two or more pieces of retention guidance apply to a piece of
   information, the guidance calling for the longest retention should
   take precedence.

5.12.5.  Reporting Guidance

   A Report Generator typically needs Reporting Guidance to govern the
   reports it generates.  TODO: This should be removed if the working
   group decides that reports are out of scope for SACM.






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5.13.  Endpoint

   See the definition in the SACM Terminology for Security Assessment
   [I-D.ietf-sacm-terminology].

   In the model, an endpoint can be part of another endpoint.  This
   covers cases where multiple physical endpoints act as one endpoint.
   The constituent endpoints may not be distinguishable by external
   observation of network behavior.

   For example, a hosting center may maintain a redundant set
   (redundancy group) of multi-chassis setups to provide active
   redundancy and load distribution on network paths to WAN gateways.
   Multi-chassis link aggregation groups make the chassis appear as one
   endpoint.  Traditional security controls must be applied either to
   physical endpoints or the redundancy groups they compose (and
   occasionally both).  Loss of redundancy is difficult to detect or
   mitigate without specific posture information about the current state
   of redundancy groups.  Even if a physical endpoint (e.g. router) that
   is part of a redundancy group is replaced, the redundancy group can
   remain the same.

5.13.1.  Endpoint Identity

   An endpoint identity provides both identification and authentication
   of the endpoint.  For example, an identity may be an X.509
   certificate [RFC5280] and corresponding private key.  [jmf- this
   example should be formatted like the other examples in this section]

   Not all kinds of identities are guaranteed to be unique.

5.13.2.  Software Component

   An endpoint contains and runs software components.

   Some of the software components are assets.  "Asset" is defined in
   RFC4949 [RFC4949] as "a system resource that is (a) required to be
   protected by an information system's security policy, (b) intended to
   be protected by a countermeasure, or (c) required for a system's
   mission."

   An examination of software needs to consider both (a) software assets
   and (b) software that may do harm.  A posture attribute collector may
   not know (a) from (b).  It is useful to define Software Component as
   the union of (a) and (b).

   Examples of Software Assets:




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   o  An application

   o  A patch

   o  The operating system kernel

   o  A boot loader

   o  Firmware that controls a disk drive

   o  A piece of JavaScript found in a web page the user visits

   Examples of harmful software components:

   o  A malicious entertainment app

   o  A malicious executable

   o  A web page that contains malicious JavaScript

   o  A business application that shipped with a virus

5.13.2.1.  Unique Software Identifier

   Organizations need to be able to uniquely identify and label software
   installed or run on an endpoint.  Specifically, they need to know the
   name, publisher, unique ID, and version; and any related patches.  In
   some cases the software's identity might be known a priori by the
   organization; in other cases, a software identity might be first
   detected by an organization when the software is first inventoried in
   an operational environment.  Due to this, it is important that an
   organization have a stable and consistent means to identify software
   found during collection.

   A piece of software may have a unique identifier, such as a SWID tag
   (ISO/IEC 19770).

5.14.  User

5.14.1.  User Identity

   An endpoint is often - but not always - associated with one or more
   users.

   A user's identity provides both identification and authentication of
   the user. @@@ Eh?





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6.  SACM Usage Scenario Example

   TODO: this section needs to refer out to wherever the operations /
   generalized workflow content ends up

   TODO: revise to eliminate graph references

   This section illustrates the proposed SACM Information Model as
   applied to SACM Usage Scenario 2.2.3, Detection of Posture Deviations
   [RFC7632].  The following subsections describe the elements
   (components and elements), graph model, and operations (sample
   workflow) required to support the Detection of Posture Deviations
   scenario.

   The Detection of Posture Deviations scenario involves multiple
   elements interacting to accomplish the goals of the scenario.
   Figure 2 illustrates those elements along with their major
   communication paths.

6.1.  Graph Model for Detection of Posture Deviation

   The following subsections contain examples of identifiers and
   metadata which would enable detection of posture deviation.  These
   lists are by no means exhaustive - many other types of metadata would
   be enumerated in a data model that fully addressed this usage
   scenario.

6.1.1.  Components

   The proposed SACM Information Model contains three components, as
   defined in the SACM Architecture [I-D.ietf-sacm-architecture]:
   Posture Attribute Information Provider, Posture Attribute Information
   Consumer, and Control Plane.

   In this example, the components are instantiated as follows:

   o  The Posture Attribute Information Provider is an endpoint security
      service which monitors the compliance state of the endpoint and
      reports any deviations for the expected posture.

   o  The Posture Attribute Information Consumer is an analytics engine
      which absorbs information from around the network and generates a
      "heat map" of which areas in the network are seeing unusually high
      rates of posture deviations.

   o  The Control Plane is a security automation broker which receives
      subscription requests from the analytics engine and authorizes




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      access to appropriate information from the endpoint security
      service.

6.1.2.  Identifiers

   To represent the elements listed above, the set of identifiers might
   include (but is not limited to):

   o  Identity - a device itself, or a user operating a device,
      categorized by type of identity (e.g. username or X.509
      certificate [RFC5280])

   o  Software asset

   o  Network Session

   o  Address - categorized by type of address (e.g.  MAC address, IP
      address, Host Identity Protocol (HIP) Host Identity Tag (HIT)
      [RFC5201], etc.)

   o  Task - categorized by type of task (e.g. internal collector,
      external collector, evaluator, or reporting task)

   o  Result - categorized by type of result (e.g. evaluation result or
      report)

   o  Guidance

6.1.3.  Metadata

   To characterize the elements listed above, the set of metadata types
   might include (but is not limited to):

   o  Authorization metadata attached to an identity identifier, or to a
      link between a network session identifier and an identity
      identifier, or to a link between a network session identifier and
      an address identifier.

   o  Location metadata attached to a link between a network session
      identifier and an address identifier.

   o  Event metadata attached to an address identifier or an identity
      identifier of an endpoint, which would be made available to
      interested parties at the time of publication, but not stored
      long-term.  For example, when a user disables required security
      software, an internal collector associated with an endpoint
      security service might publish guidance violation event metadata




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      attached to the identity identifier of the endpoint, to notify
      consumers of the change in endpoint state.

   o  Posture attribute metadata attached to an identity identifier of
      an endpoint.  For example, when required security software is not
      running, an internal collector associated with an endpoint
      security service might publish posture attribute metadata attached
      to the identity identifier of the endpoint, to notify consumers of
      the current state of the endpoint.

6.1.4.  Relationships between Identifiers and Metadata

   Interaction between multiple sets of identifiers and metadata lead to
   some fairly common patterns, or "constellations", of metadata.  For
   example, an authenticated-session metadata constellation might
   include a central network session with authorizations and location
   attached, and links to a user identity, an endpoint identity, a MAC
   address, an IP address, and the identity of the policy server that
   authorized the session, for the duration of the network session.

   These constellations may be independent of each other, or one
   constellation may be connected to another.  For example, an
   authenticated-session metadata constellation may be created when a
   user connects an endpoint to the network; separately, an endpoint-
   posture metadata constellation may be created when an endpoint
   security system and other collectors gather and publish posture
   information related to an endpoint.  These two constellations are not
   necessarily connected to each other, but may be joined if the
   component publishing the authenticated-session metadata constellation
   is able to link the network session identifier to the identity
   identifier of the endpoint.

6.2.  Workflow

   The workflow for exchange of information supporting detection of
   posture deviation, using a standard publish/subscribe/query transport
   model such as available with IF-MAP [TNC-IF-MAP-SOAP-Binding] or
   XMPP-Grid [I-D.salowey-sacm-xmpp-grid], is as follows:

   1.  The analytics engine (Posture Assessment Information Consumer)
       establishes connectivity and authorization with the transport
       fabric, and subscribes to updates on posture deviations.

   2.  The endpoint security service (Posture Assessment Information
       Provider) requests connection to the transport fabric.






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   3.  Transport fabric authenticates and establishes authorized
       privileges (e.g. privilege to publish and/or subscribe to
       security data) for the requesting components.

   4.  The endpoint security service evaluates the endpoint, detects
       posture deviation, and publishes information on the posture
       deviation.

   5.  The transport fabric notifies the analytics engine, based on its
       subscription of the new posture deviation information.

   Other components, such as access control policy servers or
   remediation systems, may also consume the posture deviation
   information provided by the endpoint security service.

7.  Acknowledgements

   Many of the specifications in this document have been developed in a
   public-private partnership with vendors and end-users.  The hard work
   of the SCAP community is appreciated in advancing these efforts to
   their current level of adoption.

   Over the course of developing the initial draft, Brant Cheikes, Matt
   Hansbury, Daniel Haynes, Scott Pope, Charles Schmidt, and Steve
   Venema have contributed text to many sections of this document.

7.1.  Contributors

   The RFC guidelines no longer allow RFCs to be published with a large
   number of authors.  Some additional authors contributed to specific
   sections of this document; their names are listed in the individual
   section headings as well as alphabetically listed with their
   affiliations below.

   +---------------+----------------+---------------------------------+
   | Name          | Affiliation    | Contact                         |
   +---------------+----------------+---------------------------------+
   | Henk Birkholz | Fraunhofer SIT | henk.birkholz@sit.fraunhofer.de |
   +---------------+----------------+---------------------------------+

8.  IANA Considerations

   This memo includes no request to IANA.








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9.  Operational Considerations

   TODO: Need to include various operational considerations here.
   Proposed sections include timestamp accuracy and which attributes
   attributes designate an endpoint.

10.  Privacy Considerations

   TODO: Need to include various privacy considerations here.

11.  Security Considerations

   Posture Assessments need to be performed in a safe and secure manner.
   In that regard, there are multiple aspects of security that apply to
   the communications between components as well as the capabilities
   themselves.  Due to time constraints, this information model only
   contains an initial listing of items that need to be considered with
   respect to security.  This list is not exhaustive, and will need to
   be augmented as the model continues to be developed/refined.

   Initial list of security considerations include:

   Authentication:  Every component and asset needs to be able to
           identify itself and verify the identity of other components
           and assets.

   Confidentiality:  Communications between components need to be
           protected from eavesdropping or unauthorized collection.
           Some communications between components and assets may need to
           be protected as well.

   Integrity:  The information exchanged between components needs to be
           protected from modification. some exchanges between assets
           and components will also have this requirement.

   Restricted Access:  Access to the information collected, evaluated,
           reported, and stored should only be viewable/consumable to
           authenticated and authorized entities.

   The TNC IF-MAP Binding for SOAP [TNC-IF-MAP-SOAP-Binding] and TNC IF-
   MAP Metadata for Network Security [TNC-IF-MAP-NETSEC-METADATA]
   document security considerations for sharing information via security
   automation.  Most, and possibly all, of these considerations also
   apply to information shared via this proposed information model.







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12.  References

12.1.  Normative References

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791, DOI
              10.17487/RFC0791, September 1981,
              <http://www.rfc-editor.org/info/rfc791>.

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

   [RFC3587]  Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global
              Unicast Address Format", RFC 3587, DOI 10.17487/RFC3587,
              August 2003, <http://www.rfc-editor.org/info/rfc3587>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

12.2.  Informative References

   [CCE]      The National Institute of Standards and Technology,
              "Common Configuration Enumeration", 2014,
              <http://nvd.nist.gov/CCE/>.

   [CCI]      United States Department of Defense Defense Information
              Systems Agency, "Control Correlation Identifier", 2014,
              <http://iase.disa.mil/cci/>.

   [CPE-WEBSITE]
              The National Institute of Standards and Technology,
              "Common Platform Enumeration", 2014,
              <http://scap.nist.gov/specifications/cpe/>.

   [CVE-WEBSITE]
              The MITRE Corporation, "Common Vulnerabilities and
              Exposures", 2014, <http://cve.mitre.org/about/>.

   [I-D.ietf-sacm-architecture]
              Cam-Winget, N., Ford, B., Lorenzin, L., McDonald, I., and
              l. loxx@cisco.com, "Secure Automation and Continuous
              Monitoring (SACM) Architecture", draft-ietf-sacm-
              architecture-00 (work in progress), October 2014.




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   [I-D.ietf-sacm-requirements]
              Cam-Winget, N. and L. Lorenzin, "Secure Automation and
              Continuous Monitoring (SACM) Requirements", draft-ietf-
              sacm-requirements-01 (work in progress), October 2014.

   [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.

   [I-D.salowey-sacm-xmpp-grid]
              Salowey, J., Lorenzin, L., Kahn, C., Pope, S., Appala, S.,
              Woland, A., and N. Cam-Winget, "XMPP Protocol Extensions
              for Use in SACM Information Transport", draft-salowey-
              sacm-xmpp-grid-00 (work in progress), July 2014.

   [IM-LIAISON-STATEMENT-NIST]
              Montville, A., "Liaison Statement: Call for Contributions
              for the SACM Information Model to NIST", May 2014,
              <http://datatracker.ietf.org/liaison/1329/>.

   [ISO.18180]
              "Information technology -- Specification for the
              Extensible Configuration Checklist Description Format
              (XCCDF) Version 1.2", ISO/IEC 18180, 2013,
              <http://standards.iso.org/ittf/PubliclyAvailableStandards/
              c061713_ISO_IEC_18180_2013.zip>.

   [ISO.19770-2]
              "Information technology -- Software asset management --
              Part 2: Software identification tag", ISO/IEC 19770-2,
              2009.

   [NISTIR-7275]
              Waltermire, D., Schmidt, C., Scarfone, K., and N. Ziring,
              "Specification for the Extensible Configuration Checklist
              Description Format (XCCDF) Version 1.2", NISTIR 7275r4,
              March 2013, <http://csrc.nist.gov/publications/nistir/
              ir7275-rev4/nistir-7275r4_updated-march-2012_clean.pdf>.

   [NISTIR-7693]
              Wunder, J., Halbardier, A., and D. Waltermire,
              "Specification for Asset Identification 1.1", NISTIR 7693,
              June 2011,
              <http://csrc.nist.gov/publications/nistir/ir7693/
              NISTIR-7693.pdf>.





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   [NISTIR-7694]
              Halbardier, A., Waltermire, D., and M. Johnson,
              "Specification for the Asset Reporting Format 1.1", NISTIR
              7694, June 2011,
              <http://csrc.nist.gov/publications/nistir/ir7694/
              NISTIR-7694.pdf>.

   [NISTIR-7695]
              Cheikes, B., Waltermire, D., and K. Scarfone, "Common
              Platform Enumeration: Naming Specification Version 2.3",
              NISTIR 7695, August 2011,
              <http://csrc.nist.gov/publications/nistir/ir7695/
              NISTIR-7695-CPE-Naming.pdf>.

   [NISTIR-7696]
              Parmelee, M., Booth, H., Waltermire, D., and K. Scarfone,
              "Common Platform Enumeration: Name Matching Specification
              Version 2.3", NISTIR 7696, August 2011,
              <http://csrc.nist.gov/publications/nistir/ir7696/
              NISTIR-7696-CPE-Matching.pdf>.

   [NISTIR-7697]
              Cichonski, P., Waltermire, D., and K. Scarfone, "Common
              Platform Enumeration: Dictionary Specification Version
              2.3", NISTIR 7697, August 2011,
              <http://csrc.nist.gov/publications/nistir/ir7697/
              NISTIR-7697-CPE-Dictionary.pdf>.

   [NISTIR-7698]
              Waltermire, D., Cichonski, P., and K. Scarfone, "Common
              Platform Enumeration: Applicability Language Specification
              Version 2.3", NISTIR 7698, August 2011,
              <http://csrc.nist.gov/publications/nistir/ir7698/
              NISTIR-7698-CPE-Language.pdf>.

   [NISTIR-7848]
              Davidson, M., Halbardier, A., and D. Waltermire,
              "Specification for the Asset Summary Reporting Format
              1.0", NISTIR 7848, May 2012,
              <http://csrc.nist.gov/publications/drafts/nistir-7848/
              draft_nistir_7848.pdf>.

   [OVAL-LANGUAGE]
              Baker, J., Hansbury, M., and D. Haynes, "The OVAL Language
              Specification version 5.10.1", January 2012,
              <https://oval.mitre.org/language/version5.10.1/>.





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   [RFC3411]  Harrington, D., Presuhn, R., and B. Wijnen, "An
              Architecture for Describing Simple Network Management
              Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
              DOI 10.17487/RFC3411, December 2002,
              <http://www.rfc-editor.org/info/rfc3411>.

   [RFC3416]  Presuhn, R., Ed., "Version 2 of the Protocol Operations
              for the Simple Network Management Protocol (SNMP)", STD
              62, RFC 3416, DOI 10.17487/RFC3416, December 2002,
              <http://www.rfc-editor.org/info/rfc3416>.

   [RFC3418]  Presuhn, R., Ed., "Management Information Base (MIB) for
              the Simple Network Management Protocol (SNMP)", STD 62,
              RFC 3418, DOI 10.17487/RFC3418, December 2002,
              <http://www.rfc-editor.org/info/rfc3418>.

   [RFC3444]  Pras, A. and J. Schoenwaelder, "On the Difference between
              Information Models and Data Models", RFC 3444, DOI
              10.17487/RFC3444, January 2003,
              <http://www.rfc-editor.org/info/rfc3444>.

   [RFC3580]  Congdon, P., Aboba, B., Smith, A., Zorn, G., and J. Roese,
              "IEEE 802.1X Remote Authentication Dial In User Service
              (RADIUS) Usage Guidelines", RFC 3580, DOI 10.17487/
              RFC3580, September 2003,
              <http://www.rfc-editor.org/info/rfc3580>.

   [RFC3954]  Claise, B., Ed., "Cisco Systems NetFlow Services Export
              Version 9", RFC 3954, DOI 10.17487/RFC3954, October 2004,
              <http://www.rfc-editor.org/info/rfc3954>.

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, DOI 10.17487/RFC4287,
              December 2005, <http://www.rfc-editor.org/info/rfc4287>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2", FYI
              36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <http://www.rfc-editor.org/info/rfc4949>.

   [RFC5201]  Moskowitz, R., Nikander, P., Jokela, P., Ed., and T.
              Henderson, "Host Identity Protocol", RFC 5201, DOI
              10.17487/RFC5201, April 2008,
              <http://www.rfc-editor.org/info/rfc5201>.

   [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,
              <http://www.rfc-editor.org/info/rfc5209>.



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   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424, DOI
              10.17487/RFC5424, March 2009,
              <http://www.rfc-editor.org/info/rfc5424>.

   [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,
              <http://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, <http://www.rfc-editor.org/info/rfc5793>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <http://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <http://www.rfc-editor.org/info/rfc6241>.

   [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,
              <http://www.rfc-editor.org/info/rfc6876>.

   [RFC7171]  Cam-Winget, N. and P. Sangster, "PT-EAP: Posture Transport
              (PT) Protocol for Extensible Authentication Protocol (EAP)
              Tunnel Methods", RFC 7171, DOI 10.17487/RFC7171, May 2014,
              <http://www.rfc-editor.org/info/rfc7171>.

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

   [SP800-117]
              Quinn, S., Scarfone, K., and D. Waltermire, "Guide to
              Adopting and Using the Security Content Automation
              Protocol (SCAP) Version 1.2", SP 800-117, January 2012,
              <http://csrc.nist.gov/publications/drafts/800-117-R1/
              Draft-SP800-117-r1.pdf>.






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   [SP800-126]
              Waltermire, D., Quinn, S., Scarfone, K., and A.
              Halbardier, "The Technical Specification for the Security
              Content Automation Protocol (SCAP): SCAP Version 1.2", SP
              800-126, September 2011,
              <http://csrc.nist.gov/publications/nistpubs/800-126-rev2/
              SP800-126r2.pdf>.

   [TNC-Architecture]
              Trusted Computing Group, ""TNC Architecture",
              Specification Version 1.5", May 2012.

   [TNC-IF-M-TLV-Binding]
              Trusted Computing Group, ""TNC IF-M: TLV Binding",
              Specification Version 1.0", May 2014.

   [TNC-IF-MAP-ICS-METADATA]
              Trusted Computing Group, ""TNC IF-MAP Metadata for ICS
              Security", Specification Version 1.0", May 2014.

   [TNC-IF-MAP-NETSEC-METADATA]
              Trusted Computing Group, ""TNC IF-MAP Metadata for Network
              Security", Specification Version 1.1", May 2012.

   [TNC-IF-MAP-SOAP-Binding]
              Trusted Computing Group, ""TNC IF-MAP Binding for SOAP",
              Specification Version 2.2", March 2014.

   [TNC-IF-T-TLS]
              Trusted Computing Group, ""TNC IF-T: Binding to TLS",
              Specification Version 2.0", February 2013.

   [TNC-IF-T-Tunneled-EAP]
              Trusted Computing Group, ""TNC IF-T: Protocol Bindings for
              Tunneled EAP Methods", Specification Version 2.0", May
              2014.

   [TNC-IF-TNCCS-TLV-Binding]
              Trusted Computing Group, ""TNC IF-TNCCS: TLV Binding",
              Specification Version 2.0", May 2014.

   [UML]      Object Management Group, ""Unified Modeling Language TM
              (UML (R))", Version 2.4.1", August 2011.








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   [W3C.REC-rdf11-concepts-20140225]
              Cyganiak, R., Wood, D., and M. Lanthaler, "RDF 1.1
              Concepts and Abstract Syntax", World Wide Web Consortium
              Recommendation REC-rdf11-concepts-20140225, February 2014,
              <http://www.w3.org/TR/2014/REC-rdf11-concepts-20140225>.

   [W3C.REC-soap12-part1-20070427]
              Gudgin, M., Hadley, M., Mendelsohn, N., Moreau, J.,
              Nielsen, H., Karmarkar, A., and Y. Lafon, "SOAP Version
              1.2 Part 1: Messaging Framework (Second Edition)", World
              Wide Web Consortium Recommendation REC-
              soap12-part1-20070427, April 2007,
              <http://www.w3.org/TR/2007/REC-soap12-part1-20070427>.

Appendix A.  Change Log

A.1.  Changes in Revision 01

   Renamed "credential" to "identity", following industry usage.  A
   credential includes proof, such as a key or password.  A username or
   a distinguished name is called an "identity".

   Removed Session, because an endpoint's network activity is not SACM's
   initial focus

   Removed Authorization, for the same reason

   Added many-to-many relationship between Hardware Component and
   Endpoint, for clarity

   Added many-to-many relationship between Software Component and
   Endpoint, for clarity

   Added "contains" relationship between Network Interface and Network
   Interface

   Removed relationship between Network Interface and Account.  The
   endpoint knows the identity it used to gain network access.  The PDP
   also knows that.  But they probably do not know the account.

   Added relationship between Network Interface and Identity.  The
   endpoint and the PDP will typically know the identity.

   Made identity-to-account a many-to-one relationship.







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A.2.  Changes in Revision 02

   Added Section 5.1, Identifying Attributes.

   Split the figure into Figure 2 and Figure 3.

   Added Figure 4, proposing a triple-store model.

   Some editorial cleanup

A.3.  Changes in Revision 03

   Moved Appendix A.1, Appendix A.2, and Appendix B into the Appendix.
   Added a reference to it in Section 1

   Added the Section 3 section.  Provided notes for the type of
   information we need to add in this section.

   Added the Section 4 section.  Moved sections on Endpoint, Hardware
   Component, Software Component, Hardware Instance, and Software
   Instance there.  Provided notes for the type of information we need
   to add in this section.

   Removed the Provenance of Information Section.  SACM is not going to
   solve provenance rather give organizations enough information to
   figure it out.

   Updated references to the Endpoint Security Posture Assessment:
   Enterprise Use Cases document to reflect that it was published as an
   RFC.

   Fixed the formatting of a few figures.

   Included references to [RFC3580] where RADIUS is mentioned.

Appendix B.  Mapping to SACM Use Cases

   TODO: revise

   (wandw)This information model directly corresponds to all four use
   cases defined in the SACM Use Cases draft [RFC7632].  It uses these
   use cases in coordination to achieve a small set of well-defined
   tasks.

   Sections [removed] thru [removed] address each of the process areas.
   For each process area, a "Process Area Description" sub-section
   represent an end state that is consistent with all the General




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   Requirements and many of the Use Case Requirements identified in the
   requirements draft [I-D.ietf-sacm-requirements].

   The management process areas and supporting operations defined in
   this memo directly support REQ004 Endpoint Discovery; REQ005-006
   Attribute and Information Based Queries, and REQ0007 Asynchronous
   Publication.

   In addition, the operations that defined for each business process in
   this memo directly correlate with the typical workflow identified in
   the SACM Use Case document.(/wandw)

Appendix C.  Security Automation with TNC IF-MAP

C.1.  What is Trusted Network Connect?

   Trusted Network Connect (TNC) is a vendor-neutral open architecture
   [TNC-Architecture] and a set of open standards for network security
   developed by the Trusted Computing Group (TCG).  TNC standards
   integrate security components across end user systems, servers, and
   network infrastructure devices into an intelligent, responsive,
   coordinated defense.  TNC standards have been widely adopted by
   vendors and customers; the TNC endpoint assessment protocols [TNC-IF-
   M-TLV-Binding][TNC-IF-TNCCS-TLV-Binding][TNC-IF-T-Tunneled-EAP][TNC-I
   F-T-TLS] were used as the base for the IETF NEA RFCs
   [RFC5792][RFC5793][RFC7171][RFC6876].

   Traditional information security architectures have separate silos
   for endpoint security, network security, server security, physical
   security, etc.  The TNC architecture enables the integration and
   categorization of security telemetry sources via the information
   model contained in its Interface for Metadata Access Points (IF-MAP)
   [TNC-IF-MAP-SOAP-Binding].  IF-MAP provides a query-able repository
   of security telemetry that may be used for storage or retrieval of
   such data by multiple types of security systems and endpoints on a
   vendor-neutral basis.  The information model underlying the IF-MAP
   repository covers, directly or indirectly, all of the security
   information types required to serve SACM use-cases.

C.2.  What is TNC IF-MAP?

   IF-MAP provides a standard client-server protocol for MAP clients to
   exchange security-relevant information via database server known as
   the Metadata Access Point or MAP.  The data (known as "metadata")
   stored in the MAP is XML data.  Each piece of metadata is tagged with
   a metadata type that indicates the meaning of the metadata and
   identifies an XML schema for it.  Due to the XML language, the set of
   metadata types is easily extensible.



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   The MAP is a graph database, not a relational database.  Metadata can
   be associated with an identifier (e.g. the email address
   "user@example.com") or with a link between two identifiers (e.g. the
   link between MAC address 00:11:22:33:44:55 and IPv4 address
   192.0.2.1) where the link defines an association (for example: a
   relation or state) between the identifiers.  These links between
   pairs of identifiers create an ad hoc graph of relationships between
   identifiers.  The emergent structure of this graph reflects a
   continuously evolving knowledge base of security-related metadata
   that is shared between various providers and consumers.

C.3.  What is the TNC Information Model?

   The TNC Information Model underlying IF-MAP relies on the graph
   database architecture to enable a (potentially distributed) MAP
   service to act as a shared clearinghouse for information that
   infrastructure devices can act upon.  The IF-MAP operations and
   metadata schema specifications (TNC IF-MAP Binding for SOAP
   [TNC-IF-MAP-SOAP-Binding], TNC IF-MAP Metadata for Network Security
   [TNC-IF-MAP-NETSEC-METADATA], and TNC IF-MAP Metadata for ICS
   Security [TNC-IF-MAP-ICS-METADATA]) define an extensible set of
   identifiers and data types.

   Each IF-MAP client may interact with the IF-MAP graph data store
   through three fundamental types of operation requests:

   o  Publish, which may create, modify, or delete metadata associated
      with one or more identifiers and/or links in the graph

   o  Search, which retrieves a selected sub-graph according to a set of
      search criteria

   o  Subscribe, which allows a client to manage a set of search
      commands which asynchronously return selected sub-graphs when
      changes to that sub-graph are made by other IF-MAP clients

   The reader is invited to review the existing IF-MAP specification
   [TNC-IF-MAP-SOAP-Binding] for more details on the above graph data
   store operation requests and their associated arguments.

   The current IF-MAP specification provides a SOAP
   [W3C.REC-soap12-part1-20070427] binding for the above operations, as
   well as associated SOAP operations for managing sessions, error
   handling, etc.







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Appendix D.  Text for Possible Inclusion in the Terminology Draft

D.1.  Terms and Definitions

   This section describes terms that have been defined by other RFCs and
   Internet Drafts, as well as new terms introduced in this document.

D.1.1.  Pre-defined and Modified Terms

   This section contains pre-defined terms that are sourced from other
   IETF RFCs and Internet Drafts.  Descriptions of terms in this section
   will reference the original source of the term and will provide
   additional specific context for the use of each term in SACM.  For
   sake of brevity, terms from [I-D.ietf-sacm-terminology] are not
   repeated here unless the original meaning has been changed in this
   document.

   Asset   For this Information Model it is necessary to change the
           scope of the definition of asset from the one provided in
           [I-D.ietf-sacm-terminology].  Originally defined in [RFC4949]
           and referenced in [I-D.ietf-sacm-terminology] as "a system
           resource that is (a) required to be protected by an
           information system's security policy, (b) intended to be
           protected by a countermeasure, or (c) required for a system's
           mission."  This definition generally relates to an "IT
           Asset", which in the context of this document is overly
           limiting.  For use in this document, a broader definition of
           the term is needed to represent non-IT asset types as well.

           In [NISTIR-7693] an asset is defined as "anything that has
           value to an organization, including, but not limited to,
           another organization, person, computing device, information
           technology (IT) system, IT network, IT circuit, software
           (both an installed instance and a physical instance), virtual
           computing platform (common in cloud and virtualized
           computing), and related hardware (e.g., locks, cabinets,
           keyboards)."  This definition aligns better with common
           dictionary definitions of the term and better fits the needs
           of this document.



D.1.2.  New Terms

   IT Asset  Originally defined in [RFC4949] as "a system resource that
           is (a) required to be protected by an information system's
           security policy, (b) intended to be protected by a
           countermeasure, or (c) required for a system's mission."



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   Security Content Automation Protocol (SCAP)  According to SP800-126,
           SCAP, pronounced "ess-cap", is "a suite of specifications
           that standardize the format and nomenclature by which
           software flaw and security configuration information is
           communicated, both to machines and humans."  SP800-117
           revision 1 [SP800-117] provides a general overview of SCAP
           1.2.  The 11 specifications that comprise SCAP 1.2 are
           synthesized by a master specification, SP800-126 revision 2
           [SP800-126], that addresses integration of the specifications
           into a coherent whole.  The use of "protocol" in its name is
           a misnomer, as SCAP defines only data models.  SCAP has been
           adopted by a number of operating system and security tool
           vendors.

Appendix E.  Text for Possible Inclusion in the Architecture or Use
             Cases

E.1.  Introduction

   The posture of an endpoint is the status of the endpoint with respect
   to the security policies and risk models of the organization.

   A system administrator needs to be able to determine which elements
   of an endpoint have a security problem and which do not conform the
   organization's security policies.  The CIO needs to be able to
   determine whether endpoints have security postures that conform to
   the organization's policies to ensure that the organization is
   complying with its fiduciary and regulatory responsibilities.  The
   regulator or auditor needs to be able to assess the level of due
   diligence being achieved by an organization to ensure that all
   regulations and due diligence expectations are being met.  The
   operator needs to understand which assets have deviated from
   organizational policies so that those assets can be remedied.

   Operators will focus on which endpoints are composed of specific
   assets with problems.  CIO and auditors need a characterization of
   how an organization is performing as a whole to manage the posture of
   its endpoints.  All of these actors need deployed capabilities that
   implement security automation standards in the form of data formats,
   interfaces, and protocols to be able to assess, in a timely and
   secure fashion, all assets on all endpoints within their enterprise.
   This information model provides a basis to identify the desirable
   characteristics of data models to support these scenarios.  Other
   SACM specifications, such as the SACM Architecture, will describe the
   potential components of an interoperable system solution based on the
   SACM information model to address the requirements for scalability,
   timeliness, and security.




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E.2.  Core Principles

   This information model is built on the following core principles:

   o  Collection and Evaluation are separate tasks.

   o  Collection and Evaluation can be performed on the endpoint, at a
      local server that communicates directly with the endpoint, or
      based on data queried from a back end data store that does not
      communicate directly with any endpoints.

   o  Every entity (human or machine) that notifies, queries, or
      responds to any guidance, collection, or evaluator must have a way
      of identifying itself and/or presenting credentials.
      Authentication is a key step in all of the processes, and while
      needed to support the business processes, information needs to
      support authentication are not highlighted in this information
      model.  There is already a large amount of existing work that
      defines information needs for authentication.

   o  Policies are reflected in guidance for collection, evaluation, and
      reporting.

   o  Guidance will often be generated by humans or through the use of
      transformations on existing automation data.  In some cases,
      guidance will be generated dynamically based on shared information
      or current operational needs.  As guidance is created it will be
      published to an appropriate guidance data store allowing guidance
      to be managed in and retrieved from convenient locations.

   o  Operators of a continuous monitoring or security automation system
      will need to make decisions when defining policies about what
      guidance to use or reference.  The guidance used may be directly
      associated with policy or may be queried dynamically based on
      associated metadata.

   o  Guidance can be gathered from multiple data stores.  It may be
      retrieved at the point of use or may be packaged and forwarded for
      later use.  Guidance may be retrieved in event of a collection or
      evaluation trigger or it may be gathered ahead of time and stored
      locally for use/reference during collection and evaluation
      activities.

E.3.  Architecture Assumptions

   This information model will focus on WHAT information needs to be
   exchanged to support the business process areas.  The architecture
   document is the best place to represent the HOW and the WHERE this



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   information is used.  In an effort to ensure that the data models
   derived from this information model scale to the architecture, four
   core architectural components need to be defined.  They are
   producers, consumers, capabilities, and repositories.  These elements
   are defined as follows:

   o  Producers (e.g., Evaluation Producer) collect, aggregate, and/or
      derive information items and provide them to consumers.  For this
      model there are Collection, Evaluation, and Results Producers.
      There may or may not be Guidance Producers.

   o  Consumers (e.g., Collection Consumer) request and/or receive
      information items from producers for their own use.  For this
      model there are Collection, Evaluation, and Results Consumers.
      There may or may not be Guidance Consumers.

   o  Capabilities (e.g., Posture Evaluation Capability) take the input
      from one or more producers and perform some function on or with
      that information.  For this model there are Collection Guidance,
      Collection, Evaluation Guidance, Evaluation, Reporting Guidance,
      and Results Reporting Capabilities.

   o  Repositories (e.g., Enterprise Repository) store information items
      that are input to or output from Capabilities, Producers, and
      Consumers.  For this model we refer to generic Enterprise and
      Guidance Repositories.

   Information that needs to be communicated by or made available to any
   of these components will be specified in each of the business process
   areas.

   In the most trivial example, illustrated in Figure 5, Consumers
   either request information from, or are notified by, Producers.

   +----------+     Request     +----------+
   |          <-----------------+          |
   | Producer |                 | Consumer |
   |          +----------------->          |
   +----------+    Response     +----------+

   +----------+                 +----------+
   |          |     Notify      |          |
   | Producer +-----------------> Consumer |
   |          |                 |          |
   +----------+                 +----------+

             Figure 5: Example Producer/Consumer Interactions




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   As illustrated in Figure 6, writing and querying from data
   repositories are a way in which this interaction can occur in an
   asynchronous fashion.

   +----------+                +----------+
   |          |                |          |
   | Producer |                | Consumer |
   |          |                |          |
   +-----+----+                +----^-----+
         |                          |
   Write |     +------------+       | Query
         |     |            |       |
         +-----> Repository +-------+
               |            |
               +------------+

            Figure 6: Producer/Consumer Repository Interaction

   To perform an assessment, these elements are chained together.  The
   diagram below is illustrative of this and process, and is meant to
   demonstrate WHAT basic information exchanges need to occur, while
   trying to maintain flexibility in HOW and WHERE they occur.

   For example:

   o  the collection capability can reside on the endpoint or not.

   o  the collection producer can be part of the collection capability
      or not.

   o  a repository can be directly associated with a producer and/or an
      evaluator or stand on its own.

   o  there can be multiple "levels" of producers and consumers.

















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                               +-------------+
                               |Evaluation   |
              +-------------+  |Guidance     +--+
              |Endpoint     |  |Capability   |  |
      +-------+             |  +-------------+  |
      |       |             |                   |
      |       +-------+-----+             +-----v-------+
      | Collection    |                   |Evaluation   |
    +-> Capability +--+--------+          |Capability   |
    | |            |Collection |    +-----------+   +----------+
    | +------------+Producer   |    |           |---|          |
    |              |           |    |Collection |   |Evaluation|
    |              |           |    |Consumer   |   |Producer  |
    |              +----+------+    +----^------+   +---+------+
   ++---------+         |                |              |
   |Collection|   +-----v------+     +---+--------+     |
   |Guidance  |   |            |     |Collection  |     |
   |Capability|   |Collection  |     |Producer    |     |
   |          |   |Consumer    |-----|            |     |
   +----------+   +------------+     +------------+     |
                             | Collection |             |
                             | Repository |             |
                             +------------+             |
                                                        |
       +--------------+           +---------------+     |
       |Evaluation    |           |Evaluation     |     |
       |Results       |           |Consumer       <-----+
       |Producer      |-----------|               |
       +-----+--------+           +---------------+
             |     |Results Reporting|
             |     |Capability       |
             |     +------------^----+
             |                  |
       +-----v--------+    +----+------+
       |Evaluation    |    |Reporting  |
       |Results       |    |Guidance   |
       |Consumer      |    |Repository |
       +---+----------+    +-----------+ +-------------+
           |                             | Results     |
           +-----------------------------> Repository  |
                                         |             |
                                         +-------------+

                Figure 7: Producer/Consumer Complex Example

   This illustrative example in Figure 7 provides a set of information
   exchanges that need to occur to perform a posture assessment.  The
   rest of this information model is using this set of exchanges based



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   on these core architectural components as the basis for determining
   information elements.

Appendix F.  Text for Possible Inclusion in the Requirements Draft

F.1.  Problem Statement

   Scalable and sustainable collection, expression, and evaluation of
   endpoint information is foundational to SACM's objectives.  To secure
   and defend one's network one must reliably determine what devices are
   on the network, how those devices are configured from a hardware
   perspective, what software products are installed on those devices,
   and how those products are configured.  We need to be able to
   determine, share, and use this information in a secure, timely,
   consistent, and automated manner to perform endpoint posture
   assessments.

F.2.  Problem Scope

   The goal of this iteration of the information model is to define the
   information needs for an organization to effectively monitor the
   endpoints operating on their network, the software installed on those
   endpoints, and the configuration of that software.  Once we have
   those three business processes in place, we can identify vulnerable
   endpoints in a very efficient manner.

   The four business process areas represent a large set of tasks that
   support endpoint posture assessment.  In an effort to address the
   most basic and foundational needs, we have also narrowed down the
   scope inside of each of the business processes to a set of defined
   tasks that strive to achieve specific results in the operational
   environment and the organization.  These tasks are:

   1.  Define the assets.  This is what we want to know about an asset.
       For instance, organizations will want to know what software is
       installed and its many critical security attributes such as patch
       level.

   2.  Resolve what assets compose an endpoint.  This requires
       populating the data elements and attributes needed to exchange
       information pertaining to the assets composing an endpoint.

   3.  Express what expected values for the data elements and attributes
       need to be evaluated against the actual collected instances of
       asset data.  This is how an organization can express its policy
       for an acceptable data element or attribute value.  A system
       administrator can also identify specific data elements and




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       attributes that represent problems, such as vulnerabilities, that
       need to be detected on an endpoint.

   4.  Evaluate the collected instances of the asset data against those
       expressed in the policy.

   5.  Report the results of the evaluation.

Appendix G.  Text With No Clear Home Yet

G.1.  Operations

   Operations that may be carried out the proposed SACM Information
   Model are:

   o  Publish data: Security information is made available in the
      information model when a component publishes data to it.

   o  Subscribe to data: A component seeking to consume an on-going
      stream of security information "subscribes" to such data from the
      information model.

   o  Query: This operation enables a component to request a specific
      set of security data regarding a specific asset (such as a
      specific user endpoint).

   The subscribe capability will allow SACM components to monitor for
   selected security-related changes in the graph data store without
   incurring the performance penalties associated with polling for such
   changes.

G.1.1.  Generalized Workflow

   The proposed SACM Information Model would be most commonly used with
   a suitable transport protocol for collecting and distributing
   security data across appropriate network platforms and endpoints.
   The information model is transport agnostic and can be used with its
   native transport provided by IF-MAP or by other data transport
   protocols such as the recently proposed XMPP-Grid.

   1.  A Posture Assessment Information Consumer (Consumer) establishes
       connectivity and authorization with the transport fabric.

   2.  A Posture Assessment Information Provider (Provider) with a
       source of security data requests connection to the transport
       fabric.





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   3.  Transport fabric authenticates and establishes authorized
       privileges (e.g. privilege to publish and/or subscribe to
       security data) for the requesting components.

   4.  Components may either publish security data, subscribe to
       security data, query for security data, or any combination of
       these operations.

   Any component sharing information - either as Provider or Consumer -
   may do so on a one-to-one, one-to-many and/or many-to-many meshed
   basis.

G.2.  From Information Needs to Information Elements

   The previous sections highlighted information needs for a set of
   management process areas that use posture assessment to achieve
   organizational security goals.  A single information need may be made
   up of multiple information elements.  Some information elements may
   be required for two different process areas, resulting in two
   different requirements.  In an effort to support the main idea of
   collect once and reuse the data to support multiple processes, we try
   to define a singular set of information elements that will support
   all the associated information needs.

G.3.  Information Model Elements

   TODO: Kim to pull up relevant content into section 4 / Elements

   Traditionally, one would use the SACM architecture to define
   interfaces that required information exchanges.  Identified
   information elements would then be based on those exchanges.  Because
   the SACM architecture document is still in the personal draft stage,
   this information model uses a different approach to the
   identification of information elements.  First it lists the four main
   endpoint posture assessment activities.  Then it identifies
   management process areas that use endpoint posture assessment to
   achieve organizational security objectives.  These process areas were
   then broken down into operations that mirrored the typical workflow
   from the SACM Use Cases draft [RFC7632].  These operations identify
   architectural components and their information needs.  In this
   section, information elements derived from those information needs
   are mapped back to the four main activities listed above.

   The original liaison statement [IM-LIAISON-STATEMENT-NIST] requested
   contributions for the SACM information model in the four areas
   described below.  Based on the capabilities defined previously in
   this document, the requested areas alone do not provide a sufficient
   enough categorization of the necessary information model elements.



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   The following sub-sections directly address the requested areas as
   follows:

   1.  Endpoint Identification

       A.  Appendix G.3.1 Asset Identifiers: Describes identification of
           many different asset types including endpoints.

   2.  Endpoint Characterization

       A.  Appendix G.3.3 Endpoint characterization: This directly maps
           to the requested area.

   3.  Endpoint Attribute Expression/Representation

       A.  Appendix G.3.4 Posture Attribute Expression: This corresponds
           to the first part of "Endpoint Attribute Expression/
           Representation."

       B.  Appendix G.3.5 Actual Value Representation: This corresponds
           to the second part of "Endpoint Attribute Expression/
           Representation."

   4.  Policy evaluation expression and results reporting

       A.  Appendix G.3.6 Evaluation Guidance: This corresponds to the
           first part of "Policy evaluation expression and results
           reporting."

       B.  Appendix G.3.7 Evaluation Result Reporting: corresponds to
           the second part of "Policy evaluation expression and results
           reporting."

   Additionally, Appendix G.3.2 Other Identifiers: describes other
   important identification concepts that were not directly requested by
   the liaison statement.

   Per the liaison statement, each subsection references related work
   that provides a basis for potential data models.  Some analysis is
   also included for each area of related work on how directly
   applicable the work is to the SACM efforts.  In general, much of the
   related work does not fully address the general or use case-based
   requirements for SACM, but they do contain some parts that can be
   used as the basis for data models that correspond to the information
   model elements.  In these cases additional work will be required by
   the WG to adapt the specification.  In some cases, existing work can
   largely be used in an unmodified fashion.  This is also indicated in
   the analysis.  Due to time constraints, the work in this section is



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   very biased to previous work supported by the authors and does not
   reflect a comprehensive listing.  An attempt has been made where
   possible to reference existing IETF work.  Additional research and
   discussion is needed to include other related work in standards and
   technology communities that could and should be listed here.  The
   authors intend to continue this work in subsequent revisions of this
   draft.

   Where possible when selecting and developing data models in support
   of these information model elements, extension points and IANA
   registries SHOULD be used to provide for extensibility which will
   allow for future data models to be addressed.

G.3.1.  Asset Identifiers

   In this context an "asset" refers to "anything that has value to an
   organization" (see [NISTIR-7693]).  This use of the term "asset" is
   broader than the current definition in [I-D.ietf-sacm-terminology].
   To support SACM use cases, a number of different asset types will
   need to be addressed.  For each type of asset, one or more type of
   asset identifier will be needed for use in establishing contextual
   relationships within the SACM information model.  The following asset
   types are referenced or implied by the SACM use cases:

   Endpoint:  Identifies an individual endpoint for which posture is
           collected and evaluated.

   Hardware:  Identifies a given type of hardware that may be installed
           within an endpoint.

   Software:  Identifies a given type of software that may be installed
           within an endpoint.

   Network:  Identifies a network for which a given endpoint may be
           connected or request a connection to.

   Organization:  Identifies an organizational unit.

   Person: Identifies an individual, often within an organizational
           context.

G.3.1.1.  Related Work

G.3.1.1.1.  Asset Identification

   The Asset Identification specification [NISTIR-7693] is an XML-based
   data model that "provides the necessary constructs to uniquely
   identify assets based on known identifiers and/or known information



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   about the assets."  Asset identification plays an important role in
   an organization's ability to quickly correlate different sets of
   information about assets.  The Asset Identification specification
   provides the necessary constructs to uniquely identify assets based
   on known identifiers and/or known information about the assets.
   Asset Identification provides a relatively flat and extensible model
   for capturing the identifying information about a one or more assets,
   and also provides a way to represent relationships between assets.

   The model is organized using an inheritance hierarchy of specialized
   asset types/classes (see Figure 8), providing for extension at any
   level of abstraction.  For a given asset type, a number of properties
   are defined that provide for capturing identifying characteristics
   and the referencing of namespace qualified asset identifiers, called
   "synthetic IDs."

   The following figure illustrates the class hierarchy defined by the
   Asset Identification specification.

         asset
          +-it-asset
          | +-circuit
          | +-computing-device
          | +-database
          | +-network
          | +-service
          | +-software
          | +-system
          | +-website
          +-data
          +-organization
          +-person

              Figure 8: Asset Identification Class Hierarchy

















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    This table presents a mapping of notional SACM asset types to those
      asset types provided by the Asset Identification specification.

   +--------------+------------------+---------------------------------+
   | SACM Asset   | Asset            | Notes                           |
   | Type         | Identification   |                                 |
   |              | Type             |                                 |
   +--------------+------------------+---------------------------------+
   | Endpoint     | computing-device | This is not a direct mapping    |
   |              |                  | since a computing device is not |
   |              |                  | required to have network-       |
   |              |                  | connectivity. Extension will be |
   |              |                  | needed to define a directly     |
   |              |                  | aligned endpoint asset type.    |
   +--------------+------------------+---------------------------------+
   | Hardware     | Not Applicable   | The concept of hardware is not  |
   |              |                  | addressed by the asset          |
   |              |                  | identification specification.   |
   |              |                  | An extension can be created     |
   |              |                  | based on the it-asset class to  |
   |              |                  | address this concept.           |
   +--------------+------------------+---------------------------------+
   | Software     | software         | Direct mapping.                 |
   +--------------+------------------+---------------------------------+
   | Network      | network          | Direct mapping.                 |
   +--------------+------------------+---------------------------------+
   | Organization | organization     | Direct mapping.                 |
   +--------------+------------------+---------------------------------+
   | Person       | person           | Direct mapping.                 |
   +--------------+------------------+---------------------------------+

       Table 1: Mapping of SACM to Asset Identification Asset Types

   This specification has been adopted by a number of SCAP validated
   products.  It can be used to address asset identification and
   categorization needs within SACM with minor modification.

G.3.1.2.  Endpoint Identification

   An unique name for an endpoint.  This is a foundational piece of
   information that will enable collected posture attributes to be
   related to the endpoint from which they were collected.  It is
   important that this name either be created from, provide, or be
   associated with operational information (e.g., MAC address, hardware
   certificate) that is discoverable from the endpoint or its
   communications on the network.  It is also important to have a method
   of endpoint identification that can persist across network sessions
   to allow for correlation of collected data over time.



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G.3.1.2.1.  Related Work

   The previously introduced asset identification specification (see
   Appendix G.3.1.1.1 provides a basis for endpoint identification using
   the "computing-device" class.  While the meaning of this class is
   broader than the current definition of an endpoint in the SACM
   terminology [I-D.ietf-sacm-terminology], either that class or an
   appropriate sub-class extension can be used to capture identification
   information for various endpoint types.

G.3.1.3.  Software Identification

   A unique name for a unit of installable software.  Software names
   should generally represent a unique release or installable version of
   software.  Identification approaches should allow for identification
   of commercially available, open source, and organizationally
   developed custom software.  As new software releases are created, a
   new software identifier should be created by the releasing party
   (e.g., software creator, publisher, licensor).  Such an identifier is
   useful to:

   o  Relate metadata that describes the characteristics of the unit of
      software, potentially stored in a repository of software
      information.  Typically, the software identifier would be used as
      an index into such a repository.

   o  Indicate the presence of the software unit on a given endpoint.

   o  To determine what endpoints are the targets for an assessment
      based on what software is installed on that endpoint.

   o  Define guidance related to a software unit that represents
      collection, evaluation, or other automatable policies.

   In general, an extensible method of software identification is needed
   to provide for adequate coverage and to address legacy identification
   approaches.  Use of an IANA registry supporting multiple software
   identification methods would be an ideal way forward.

G.3.1.3.1.  Related Work

   While we are not aware of a one-size-fits-all solution for software
   identification, there are two existing specifications that should be
   considered as part of the solution set.  They are described in the
   following subsections.






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G.3.1.3.1.1.  Common Platform Enumeration

G.3.1.3.1.1.1.  Background

   The Common Platform Enumeration (CPE) [CPE-WEBSITE] is composed of a
   family of four specification that are layered to build on lower-level
   functionality.  The following describes each specification:

   1.  CPE Naming: A standard machine-readable format [NISTIR-7695] for
       encoding names of IT products and platforms.  This defines the
       notation used to encode the vendor, software name, edition,
       version and other related information for each platform or
       product.  With the 2.3 version of CPE, a second, more advanced
       notation was added to the original colon-delimited notation for
       CPE naming.

   2.  CPE Matching: A set of procedures [NISTIR-7696] for comparing
       names.  This describes how to compare two CPE names to one
       another.  It describes a logical method that ensures that
       automated systems comparing two CPE names would arrive at the
       same conclusion.

   3.  CPE Applicability Language: An XML-based language [NISTIR-7698]
       for constructing "applicability statements" that combine CPE
       names with simple logical operators.

   4.  CPE Dictionary: An XML-based catalog format [NISTIR-7697] that
       enumerates CPE Names and associated metadata.  It details how to
       encode the information found in a CPE Dictionary, thereby
       allowing multiple organizations to maintain compatible CPE
       Dictionaries.

   The primary use case of CPE is for exchanging software inventory
   data, as it allows the usage of unique names to identify software
   platforms and products present on an endpoint.  The NIST currently
   maintains and updates a dictionary of all agreed upon CPE names, and
   is responsible for ongoing maintenance of the standard.  Many of the
   names in the CPE dictionary have been provided by vendors and other
   3rd-parties.

   While the effort has seen wide adoption, most notably within the US
   Government, a number of critical flaws have been identified.  The
   most critical issues associated with the effort are:

   o  Because there is no requirement for vendors to publish their own,
      official CPE names, CPE necessarily requires one or more
      organizations for curation.  This centralized curation requirement
      ensures that the effort has difficulty scaling.



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   o  Not enough primary source vendors provide platform and product
      naming information.  As a result, this pushes too much of the
      effort out onto third-party groups and non-authoritative
      organizations.  This exacerbates the ambiguity in names used for
      identical platforms and products and further reduces the utility
      of the effort.

G.3.1.3.1.1.2.  Applicability to Software Identification

   The Common Platform Enumeration (CPE) Naming specification version
   2.3 defines a scheme for human-readable standardized identifiers of
   hardware and software products.

   CPE names are the identifier format for software and hardware
   products used in SCAP 1.2 and is currently adopted by a number of
   SCAP product vendors.

   CPE names can be directly referenced in the asset identification
   software class (see Appendix G.3.1.1.1.)

   Although relevant, CPE has an unsustainable maintenance "tail" due to
   the need for centralized curation and naming-consistency enforcement.
   Its mention in this document is to support the historic inclusion of
   CPE as part of SCAP and implementation of this specification in a
   number of security processes and products.  Going forward, software
   identification (SWID) tags are recommended as a replacement for CPE.
   To this end, work has been started to align both efforts to provide
   translation for software units identified using SWID tags to CPE
   Names.  This translation would allow tools that currently use CPE-
   based identifiers to map to SWID identifiers during a transition
   period.

G.3.1.3.1.2.  Software Identification (SWID) Tags

   The software identification tag specification [ISO.19770-2] is an
   XML-based data model that is used to describe a unit of installable
   software.  A SWID tag contains data elements that:

   o  Identify a specific unit of installable software,

   o  Enable categorization of the software (e.g., edition, bundle),

   o  Identification and hashing of software artifacts (e.g.,
      executables, shared libraries),

   o  References to related software and dependencies, and

   o  Inclusion of extensible metadata.



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   SWID tags can be associated with software installation media,
   installed software, software updates (e.g., service packs, patches,
   hotfixes), and redistributable components.  SWID tags also provide
   for a mechanism to relate these concepts to each other.  For example,
   installed software can be related back to the original installation
   media, patches can be related to the software that they patch, and
   software dependencies can be described for required redistributable
   components.  SWID tags are ideally created at build-time by the
   software creator, publisher or licensor; are bundled with software
   installers; and are deployed to an endpoint during software
   installation.

   SWID tags should be considered for two primary uses:

   1.  As the data format for exchanging descriptive information about
       software products, and

   2.  As the source of unique identifiers for installed software.

   In addition to usage for software identification, a SWID tag can
   provide the necessary data needed to target guidance based on
   included metadata, and to support verification of installed software
   and software media using cryptographic hashes.  This added
   information increases the value of using SWID tags as part of the
   larger security automation and continuous monitoring solution space.

G.3.1.4.  Hardware Identification

   Due to the time constraints, research into information elements and
   related work for identifying hardware is not included in this
   revision of the information model.

G.3.2.  Other Identifiers

   In addition to identifying core asset types, it is also necessary to
   have stable, globally unique identifiers to represent other core
   concepts pertaining to posture attribute collection and evaluation.
   The concept of "global uniqueness" ensures that identifiers provided
   by multiple organization do not collide.  This may be handled by a
   number of different mechanisms (e.g., use of namespaces).

G.3.2.1.  Platform Configuration Item Identifier

   A name for a low-level, platform-dependent configuration mechanism as
   determined by the authoritative primary source vendor.  New
   identifiers will be created when the source vendor makes changes to
   the underlying platform capabilities (e.g., adding new settings,
   replacing old settings with new settings).  When created each



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   identifier should remain consistent with regards to what it
   represents.  Generally, a change in meaning would constitute the
   creation of a new identifier.

   For example, if the configuration item is for "automatic execution of
   code", then the platform vendor would name the low-level mechanism
   for their platform (e.g., autorun for mounted media).

G.3.2.1.1.  Related Work

G.3.2.1.1.1.  Common Configuration Enumeration

   The Common Configuration Enumeration (CCE) [CCE] is an effort managed
   by NIST.  CCE provides a unique identifier for platform-specific
   configuration items that facilitates fast and accurate correlation of
   configuration items across multiple information sources and tools.
   CCE does this by providing an identifier, a human readable
   description of the configuration control, parameters needed to
   implement the configuration control, various technical mechanisms
   that can be used to implement the configuration control, and
   references to documentation that describe the configuration control
   in more detail.

   By vendor request, NIST issues new blocks of CCE identifiers.
   Vendors then populate the required fields and provided the details
   back to NIST for publication in the "CCE List", a consolidated
   listing of assigned CCE identifiers and associated data.  Many
   vendors also include references to these identifiers in web pages,
   SCAP content, and prose configuration guides they produce.

   CCE the identifier format for platform specific configuration items
   in SCAP and is currently adopted by a number of SCAP product vendors.

   While CCE is largely supported as a crowd-sourced effort, it does
   rely on a central point of coordination for assignment of new CCE
   identifiers.  This approach to assignment requires a single
   organization, currently NIST, to manage allocations of CCE
   identifiers which doesn't scale well and introduces sustainability
   challenges for large volumes of identifier assignment.  If this
   approach is used going forward by SACM, a namespaced approach is
   recommended for identifier assignment that allows vendors to manage
   their own namespace of CCE identifiers.  This change would require
   additional work to specify and implement.








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G.3.2.1.1.2.  Open Vulnerability and Assessment Language

G.3.2.1.1.2.1.  Background

   The Open Vulnerability and Assessment Language (OVAL(R)) is an XML
   schema-based data model developed as part of a public-private
   information security community effort to standardize how to assess
   and report upon the security posture of endpoints.  OVAL provides an
   established framework for making assertions about an endpoint's
   posture by standardizing the three main steps of the assessment
   process:

   1.  representing the current endpoint posture;

   2.  analyzing the endpoint for the presence of the specified posture;
       and

   3.  representing the results of the assessment.

   OVAL facilitates collaboration and information sharing among the
   information security community and interoperability among tools.
   OVAL is used internationally and has been implemented by a number of
   operating system and security tools vendors.




























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   The following figure illustrates the OVAL data model.

                                             +------------+
                       +-----------------+   | Variables  |
                       | Common          <---+            |
              +-------->                 |   +------------+
              |        |                 |   +------------+
              |        |                 <---+ Directives |
              |        +--------^----^---+   |            |
              |                 |    |       +--------+---+
              |                 |    +-----+          |
              |                 |          |          |
              |        +--------+--------+ |          |
              |        | System          | |          |
              |        | Characteristics | |          |
       +------+------+ |                 | | +--------v---+
       | Definitions | |                 | | | Results    |
       |             | +--------^--------+ +-+            |
       |             |          |            |            |
       |             |          +------------+            |
       +------^------+                       +-------+----+
              |                                      |
              +--------------------------------------+

   Note: The direction of the arrows indicate a model dependency

                       Figure 9: The OVAL Data Model

   The OVAL data model [OVAL-LANGUAGE], visualized in Figure 9, is
   composed of a number of different components.  The components are:

   o  Common: Constructs, enumerations, and identifier formats that are
      used throughout the other model components.

   o  Definitions: Constructs that describe assertions about system
      state.  This component also includes constructs for internal
      variable creation and manipulation through a variety of functions.
      The core elements are:

      *  Definition: A collection of logical statements that are
         combined to form an assertion based on endpoint state.

      *  Test(platform specific): A generalized construct that is
         extended in platform schema to describe the evaluation of
         expected against actual state.






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      *  Object(platform specific): A generalized construct that is
         extended in platform schema to describe a collectable aspect of
         endpoint posture.

      *  State(platform specific): A generalized construct that is
         extended in platform schema to describe a set of criteria for
         evaluating posture attributes.

   o  Variables: Constructs that allow for the parameterization of the
      elements used in the Definitions component based on externally
      provided values.

   o  System Characteristics: Constructs that represent collected
      posture from one or more endpoints.  This element may be embedded
      with the Results component, or may be exchanged separately to
      allow for separate collection and evaluation.  The core elements
      of this component are:

      *  CollectedObject: Provides a mapping of collected Items to
         elements defined in the Definitions component.

      *  Item(platform specific): A generalized construct that is
         extended in platform schema to describe specific posture
         attributes pertaining to an aspect of endpoint state.

   o  Results: Constructs that represent the result of evaluating
      expected state (state elements) against actual state (item
      elements).  It includes the true/false evaluation result for each
      evaluated Definition and Test.  Systems characteristics are
      embedded as well to provide low-level posture details.

   o  Directives: Constructs that enable result reporting detail to be
      declared, allowing for result production to be customized.

   End-user organizations and vendors create assessment guidance using
   OVAL by creating XML instances based on the XML schema implementation
   of the OVAL Definitions model.  The OVAL Definitions model defines a
   structured identifier format for each of the Definition, Test,
   Object, State, and Item elements.  Each instantiation of these
   elements in OVAL XML instances are assigned a unique identifier based
   on the specific elements identifier syntax.  These XML instances are
   used by tools that support OVAL to drive collection and evaluation of
   endpoint posture.  When posture collection is performed, an OVAL
   Systems Characteristics XML instance is generated based on the
   collected posture attributes.  When this collected posture is
   evaluated, an OVAL Result XML instance is generated that contains the
   results of the evaluation.  In most implementations, the collection
   and evaluation is performed at the same time.



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   Many of the elements in the OVAL model (i.e., Test, Object, State,
   Item) are abstract, requiring a platform-specific schema
   implementation, called a "Component Model" in OVAL.  These platform
   schema implementations are where platform specific posture attributes
   are defined.  For each aspect of platform posture a specialized OVAL
   Object, which appears in the OVAL Definitions model, provides a
   format for expressing what posture attribute data to collect from an
   endpoint through the specification of a datatype, operation, and
   value(s) on entities that uniquely identify a platform configuration
   item.  For example, a hive, key, and name is used to identify a
   registry key on a Windows endpoint.  Each specialized OVAL Object has
   a corresponding specialized State, which represents the posture
   attributes that can be evaluated, and an Item which represents the
   specific posture attributes that can be collected.  Additionally, a
   specialized Test exists that allows collected Items corresponding to
   a CollectedObject to be evaluated against one or more specialized
   States of the same posture type.

   The OVAL language provides a generalized approach suitable for
   posture collection and evaluation.  While this approach does provide
   for a degree of extensibility, there are some concerns that should be
   addressed in order to make OVAL a viable basis for SACM's use.  These
   concerns include:

   o  Platform Schema Creation and Maintenance: In OVAL platform schema,
      the OVAL data model maintains a tight binding between the Test,
      Object, State, and Item elements used to assess an aspect of
      endpoint posture.  Creating a new platform schema or adding a new
      posture aspect to an existing platform schema can be a very labor
      intensive process.  Doing so often involves researching and
      understanding system APIs and can be prone to issues with
      inconsistency within and between platforms.  To simplify platform
      schema creation and maintenance, the model needs to be evolved to
      generalize the Test, Object, and State elements, requiring only
      the definition of an Item representation.

   o  Given an XML instance based on the Definitions model, it is not
      clear in the specification how incremental collection and
      evaluation can occur.  Because of this, typically, OVAL
      assessments are performed on a periodic basis.  The OVAL
      specification needs to be enhanced to include specifications for
      performing event-based and incremental assessment in addition to
      full periodic collection.

   o  Defining new functions for manipulating variable values is current
      handled in the Definitions schema.  This requires revision to the
      core language to add new functions.  The OVAL specification needs




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      to be evolved to provide for greater extensibility in this area,
      allowing extension schema to define new functions.

   o  The current process for releasing a new version of OVAL, bundle
      releases of the core language with release of community recognized
      platform schema.  The revision processes for the core and platform
      schema need to be decoupled.  Each platform schema should use some
      mechanism to declare which core language version it relies on.

   If adopted by SCAM, these issues will need to be addressed as part of
   the SCAM engineering work to make OVAL more broadly adoptable as a
   general purpose data model for posture collection and evaluation.

G.3.2.1.1.2.2.  Applicability to Platform Configuration Item
                Identification

   Each OVAL Object is identified by a globally unique identifier.  This
   globally unique identifier could be used by the SACM community to
   identify platform-specific configuration items and at the same time
   serve as collection guidance.  If used in this manner, OVAL Objects
   would likely need to undergo changes in order to decouple it from
   evaluation guidance and to provide more robust collection
   capabilities to support the needs of the SACM community.

G.3.2.2.  Configuration Item Identifier

   An identifier for a high-level, platform-independent configuration
   control.  This identification concept is necessary to allow similar
   configuration item concepts to be comparable across platforms.  For
   example, a configuration item might be created for the minimum
   password length configuration control, which may then have a number
   of different platform-specific configuration settings.  Without this
   type of identification, it will be difficult to perform evaluation of
   expected versus actual state in a platform-neutral way.

   High-level configuration items tend to change much less frequently
   than the platform-specific configuration items (see Appendix G.3.2.1)
   that might be associated with them.  To provide for the greatest
   amount of sustainability, collections of configuration item
   identifiers are best defined by specific communities of interest,
   while platform-specific identifiers are best defined by the source
   vendor of the platform.  Under this model, the primary source vendors
   would map their platform-specific configuration controls to the
   appropriate platform-independent item allowing end-user organizations
   to make use of these relationships.

   To support different communities of interest, it may be necessary to
   support multiple methods for identification of configuration items



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   and for associating related metadata.  Use of an IANA registry
   supporting multiple configuration item identification methods would
   be an ideal way forward.  To the extent possible, a few number of
   configuration item identification approaches is desirable, to
   maximize the update by vendors who would be maintain mapping of
   platform-specific configuration identifiers to the more general
   platform-neutral configuration identifiers.

G.3.2.2.1.  Related Work

G.3.2.2.1.1.  Control Correlation Identifier

   The Control Correlation Identifier (CCI) [CCI] is developed and
   managed by the United States Department of Defense (US-DoD) Defense
   Information Systems Agency (DISA).  According to their website, CCI
   "provides a standard identifier and description for each of the
   singular, actionable statements that comprise an information
   assurance (IA) control or IA best practice.  CCI bridges the gap
   between high-level policy expressions and low-level technical
   implementations.  CCI allows a security requirement that is expressed
   in a high-level policy framework to be decomposed and explicitly
   associated with the low-level security setting(s) that must be
   assessed to determine compliance with the objectives of that specific
   security control.  This ability to trace security requirements from
   their origin (e.g., regulations, IA frameworks) to their low-level
   implementation allows organizations to readily demonstrate compliance
   to multiple IA compliance frameworks.  CCI also provides a means to
   objectively roll-up and compare related compliance assessment results
   across disparate technologies."

   It is recommended that this approach be analysed as a potential
   candidate for use as a configuration item identifier method.

   Note: This reference to CCI is for informational purposes.  Since the
   editors do not represent DISA's interests, its inclusion in this
   document does not indicate the presence or lack of desire to
   contribute aspects of this effort to SACM.

G.3.2.2.1.2.  A Potential Alternate Approach

   There will likely be a desire by different communities to create
   different collections of configuration item identifiers.  This
   fracturing may be caused by:

   o  Different requirements for levels of abstraction,

   o  Varying needs for timely maintenance of the collection, and




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   o  Differing scopes of technological needs.

   Due to these and other potential needs, it will be difficult to
   standardize around a single collection of configuration identifiers.
   A workable solution will be one that is scalable and usable for a
   broad population of end-user organizations.  An alternate approach
   that should be considered is the definition of data model that
   contains a common set of metadata attributes, perhaps supported by an
   extensible taxonomy, that can be assigned to platform-specific
   configuration items.  If defined at a necessary level of granularity,
   it may be possible to query collections of platform-specific
   configuration items provided by vendors to create groupings at
   various levels of abstractions.  By utilizing data provided by
   vendors, technological needs and the timeliness of information can be
   addressed based on customer requirements.

   SACM should consider this and other approaches to satisfy the need
   for configuration item roll-up in a way that provides the broadest
   benefit, while achieving a sensible degree of scalability and
   sustainability.

G.3.2.3.  Vulnerability Identifier

   An unique name for a known software flaw that exists in specific
   versions of one or more units of software.  One use of a
   vulnerability identifier in the SACM context is to associate a given
   flaw with the vulnerable software using software identifiers.  For
   this reason at minimum, software identifiers should identify a
   software product to the patch or version level, and not just to the
   level that the product is licensed.

G.3.2.3.1.  Related Work

G.3.2.3.1.1.  Common Vulnerabilities and Exposures

   Common Vulnerabilities and Exposures (CVE) [CVE-WEBSITE] is a MITRE
   led effort to assign common identifiers to publicly known security
   vulnerabilities in software to facilitate the sharing of information
   related to the vulnerabilities.  CVE is the industry standard by
   which software vendors, tools, and security professionals identify
   vulnerabilities and could be used to address SACM's need for a
   vulnerability identifier.

G.3.3.  Endpoint characterization

   Target when policies (collection, evaluated, guidance) apply

   Collection can be used to further characterize



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   Also human input

   Information required to characterize an endpoint is used to determine
   what endpoints are the target of a posture assessment.  It is also
   used to determine the collection, evaluation, and/or reporting
   policies and the associated guidance that apply to the assessment.
   Endpoint characterization information may be populated by:

   o  A manual input process and entered into records associated with
      the endpoint, or

   o  Using information collected and evaluated by an assessment.

   Regardless of the method of collection, it will be necessary to query
   and exchange endpoint characterization information as part of the
   assessment planning workflow.

G.3.3.1.  Related Work

G.3.3.1.1.  Extensible Configuration Checklist Description Format

G.3.3.1.1.1.  Background

   The Extensible Configuration Checklist Description Format (XCCDF) is
   a specification that provides an XML-based format for expressing
   security checklists.  The XCCDF 1.2 specification is published by
   International Organization for Standardization (ISO) [ISO.18180].
   XCCDF contains multiple components and capabilities, and various
   components align with different elements of this information model.

   This specification was originally published by NIST [NISTIR-7275].
   When contributed to ISO Joint Technical Committee 1 (JTC 1), a
   comment was introduced indicating an interest in the IETF becoming
   the maintenance organization for this standard.  If the SACM working
   group is interested in taking on engineering work pertaining to
   XCCDF, a contribution through a national body can be made to create a
   ballot resolution for transition of this standard to the IETF for
   maintenance.

G.3.3.1.1.2.  Applicability to Endpoint characterization

   The target component of XCCDF provides a mechanism for capturing
   characteristics about an endpoint including the fully qualified
   domain name, network address, references to external identification
   information (e.g.  Asset Identification), and is extensible to
   support other useful information (e.g.  MAC address, globally unique
   identifier, certificate, etc.).  XCCDF may serve as a good starting




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   point for understanding the types of information that should be used
   to identify an endpoint.

G.3.3.1.2.  Asset Reporting Format

G.3.3.1.2.1.  Background

   The Asset Reporting Format (ARF) [NISTIR-7694] is a data model to
   express information about assets, and the relationships between
   assets and reports.  It facilitates the reporting, correlating, and
   fusing of asset information within and between organizations.  ARF is
   vendor and technology neutral, flexible, and suited for a wide
   variety of reporting applications.

   There are four major sub-components of ARF:

   o  Asset: The asset component element includes asset identification
      information for one or more assets.  It simply houses assets
      independent of their relationships to reports.  The relationship
      section can then link the report section to specific assets.

   o  Report: The report component element contains one or more asset
      reports.  An asset report is composed of content (or a link to
      content) about one or more assets.

   o  Report-Request: The report-request component element contains the
      asset report requests, which can give context to asset reports
      captured in the report section.  The report-request section simply
      houses asset report requests independent of the report which was
      subsequently generated.

   o  Relationship: The relationship component element links assets,
      reports, and report requests together with well-defined
      relationships.  Each relationship is defined as {subject}
      {predicate} {object}, where {subject} is the asset, report
      request, or report of interest, {predicate} is the relationship
      type being established, and {object} is one or more assets, report
      requests, or reports.

G.3.3.1.2.2.  Relationship to Endpoint Characterization

   For Endpoint Characterization, ARF can be used in multiple ways due
   to its flexibility.  ARF supports the use of the Asset Identification
   specification (more in Appendix G.3.3.1.2.3) to embed the
   representation of one or more assets as well as relationships between
   those assets.  It also allows the inclusion of report-requests, which
   can provide details on what data was required for an assessment.




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   ARF is agnostic to the data formats of the collected posture
   attributes and therefore can be used within the SACM Architecture to
   provide Endpoint Characterization without dictating data formats for
   the encoding of posture attributes.  The embedded Asset
   Identification data model (see Appendix G.3.1.1.1) can be used to
   characterize one or more endpoints to allow targeting for collection,
   evaluation, etc.  Additionally, the report-request model can dictate
   the type of reporting that has been requested, thereby providing
   context as to which endpoints the guidance applies.

G.3.3.1.2.3.  Asset Identification

   Described earlier

   In the context of Endpoint Characterization, the Asset Identification
   data model could be used to encode information that identifies
   specific endpoints and/or classes of endpoints to which a particular
   assessment is relevant.  The flexibility in the Asset Identification
   specification allows usage of various endpoint identifiers as defined
   by the SACM engineering work.

   As stated in Appendix G.3.3.1.2.3, the Asset Identification
   specification is included within the Asset Reporting Framework (ARF)
   and therefore can be used in concert with that specification as well.

G.3.3.1.3.  The CPE Applicability Language

   CPE described earlier

   Applicability in CPE is defined as an XML language [NISTIR-7698] for
   using CPE names to create applicability statements using logical
   expressions.  These expressions can be used to applicability
   statements that can drive decisions about assets, whether or not to
   do things like collect data, report data, and execute policy
   compliance checks.

   It is recommended that SACM evolve the CPE Applicability Language
   through engineering work to allow it to better fit into the security
   automation vision laid out by the Use Cases and Architecture for
   SACM.  This should include de-coupling the identification part of the
   language from the logical expressions, making it such that the
   language is agnostic to the method by which assets are identified.
   This will allow use of SWID, CPE Names, or other identifiers to be
   used, perhaps supported by an IANA registry of identifier types.

   The other key aspect that should be evolved is the ability to make
   use of the Applicability Language against a centralized repository of
   collected posture attributes.  The language should be able to make



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   applicability statements against previously collected posture
   attributes, such that an enterprise can quickly query the correct set
   of applicable endpoints in an automated and scalable manner.

G.3.4.  Posture Attribute Expression

   Discuss the catalog concept.  Listing of things that can be chosen
   from.  Things we can know about.  Vendors define catalogs.  Ways for
   users to get vendor-provided catalogs.

   To support the collection of posture attributes, there needs to be a
   way for operators to identify and select from a set of platform-
   specific attribute(s) to collect.  The same identified attributes
   will also need to be identified post-collection to associate the
   actual value of that attribute pertaining to an endpoint as it was
   configured at the time of the collection.  To provide for
   extensibility, the need exists to support a variety of possible
   identification approaches.  It is also necessary to enable vendors of
   software to provide a listing, or catalog, of the available posture
   attributes to operators that can be collected.  Ideally, a federated
   approach will be used to allow organizations to identify the location
   for a repository containing catalogs of posture attributes provided
   by authoritative primary source vendors.  By querying these
   repositories, operators will be able to acquire the appropriate
   listings of available posture attributes for their deployed assets.
   One or more posture attribute expressions are needed to support these
   exchanges.

G.3.4.1.  Related Work

   The ATOM Syndication Format [RFC4287] provides an extensible,
   flexible XML-based expression for organizing a collection of data
   feeds consisting of entries.  This standard can be used to express
   one or more catalogs of posture attributes represented as data feeds.
   Groupings of posture attributes would be represented as entries.
   These entries could be defined using the data models described in the
   "Related Work" sections below.  Additionally, this approach can also
   be used more generally for guidance repositories allowing other forms
   of security automation guidance to be exchanged using the same
   format.

G.3.4.2.  Platform Configuration Attributes

   A low-level, platform-dependent posture attribute as determined by
   the authoritative primary source vendor.  Collection guidance will be
   derived from catalogs of platform specific posture attributes.





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   For example, a primary source vendor would create a platform-specific
   posture attribute that best models the posture attribute data for
   their platform.

G.3.4.2.1.  Related Work

G.3.4.2.1.1.  Open Vulnerability and Assessment Language

   A general overview of OVAL was provided previously in
   Appendix G.3.2.1.1.2.1.  The OVAL System Characteristics platform
   extension models provide a catalog of the posture attributes that can
   be collected from an endpoint.  In OVAL these posture attributes are
   further grouped into logical constructs called OVAL Items.  For
   example, the passwordpolicy_item that is part of the Windows platform
   extension groups together all the posture attributes related to
   passwords for an endpoint running Windows (e.g. maximum password age,
   minimum password length, password complexity, etc.).  The various
   OVAL Items defined in the OVAL System Characteristics may serve as a
   good starting for the types of posture attribute data that needs to
   be collected from endpoints.

   OVAL platform extension models may be shared using the ATOM
   Syndication Format.

G.3.4.2.1.2.  Network Configuration Protocol and YANG Data Modeling
              Language

   The Network Configuration Protocol (NETCONF) [RFC6241] defines a
   mechanism for managing and retrieving posture attribute data from
   network infrastructure endpoints.  The posture attribute data that
   can be collected from a network infrastructure endpoint is highly
   extensible and can defined using the YANG modeling language
   [RFC6020].  Models exist for common datatypes, interfaces, and
   routing subsystem information among other subjects.  The YANG
   modeling language may be useful in providing an extensible framework
   for the SACM community to define one or more catalogs of posture
   attribute data that can be collected from network infrastructure
   endpoints.

   Custom YANG modules may also be shared using the ATOM Syndication
   Format.

G.3.4.2.1.3.  Simple Network Management Protocol and Management
              Information Base Entry

   The Simple Network Protocol (SNMP) [RFC3411] defines a protocol for
   managing and retrieving posture attribute data from endpoints on a
   network . The posture attribute data that can be collected of an



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   endpoint and retrieved by SNMP is defined by the Management
   Information Base (MIB) [RFC3418] which is hierarchical collection of
   information that is referenced using Object Identifiers . Given this,
   MIBs may provide an extensible way for the SACM community to define a
   catalog of posture attribute data that can be collected off of
   endpoints using SNMP.

   MIBs may be shared using the ATOM Syndication Format.

G.3.5.  Actual Value Representation

   Discuss instance concept.

   The actual value of a posture attribute is collected or published
   from an endpoint.  The identifiers discussed previously provide names
   for the posture attributes (i.e., software or configuration item)
   that can be the subject of an assessment.  The information items
   listed below are the actual values collected during the assessment
   and are all associated with a specific endpoint.

G.3.5.1.  Software Inventory

   A software inventory is a list of software identifiers (or content)
   associated with a specific endpoint.  Software inventories are
   maintained in some organized fashion so that entities can interact
   with it.  Just having software publish identifiers onto an endpoint
   is not enough, there needs to be an organized listing of all those
   identifiers associated with that endpoint.

G.3.5.1.1.  Related Work

G.3.5.1.1.1.  Asset Summary Reporting

   The Asset Summary Reporting (ASR) specification [NISTIR-7848]
   provides a format for capturing summary information about one or more
   assets.  Specifically, it provides the ability to express a
   collection of records from some defined data source and map them to
   some set of assets.  As a result, this specification may be useful
   for capturing the software installed on an endpoint, its relevant
   attributes, and associating it with a particular endpoint.

G.3.5.1.1.2.  Software Identification Tags

   SWID tag were previously introduced in Appendix G.3.1.3.1.2.  As
   stated before, SWID tags are ideally deployed to an endpoint during
   software installation.  In the less ideal case, they may also be
   generated based on information retrieved from a proprietary software
   installation data store.  At minimum, SWID tag must contain an



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   identifier for each unit of installed software.  Given this, SWID
   tags may be a viable way for SACM to express detailed information
   about the software installed on an endpoint.

G.3.5.2.  Collected Platform Configuration Posture Attributes

   Configurations associated with a software instance associated with an
   endpoint

   A list of the configuration posture attributes associated with the
   actual values collected from the endpoint during the assessment as
   required/expressed by any related guidance.  Additionally, each
   configuration posture attribute is associated with the installed
   software instance it pertains to.

G.3.5.2.1.  Related Work

G.3.5.2.1.1.  Open Vulnerability and Assessment Language

   A general overview of OVAL was provided previously in
   Appendix G.3.2.1.1.2.1.  As mentioned earlier, the OVAL System
   Characteristics platform extensions provide a catalog of the posture
   attributes that can be collected and assessed in the form of OVAL
   Items.  These OVAL Items also serve as a model for representing
   posture attribute data and associated values that are collected off
   an endpoint.  Furthermore, the OVAL System Characteristics model
   provides a system_info construct that captures information that
   identifies and characterizes the endpoint from which the posture
   attribute data was collected.  Specifically, it includes operating
   system name, operating system version, endpoint architecture,
   hostname, network interfaces, and an extensible construct to support
   arbitrary additional information that may be useful in identifying
   the endpoint in an enterprise such as information capture in Asset
   Identification constructs.  The OVAL System Characteristics model
   could serve as a useful starting point for representing posture
   attribute data collected from an endpoint although it may need to
   undergo some changes to satisfy the needs of the SACM community.

G.3.5.2.1.2.  NETCONF-Based Collection

   Introduced earlier in Appendix G.3.4.2.1.2, NETCONF defines a
   protocol for managing and retrieving posture attribute data from
   network infrastructure endpoints.  NETCONF provides the <get-config>
   and <get> operations to retrieve the configuration data, and
   configuration data and state data respectively from a network
   infrastructure endpoint.  Upon successful completion of these
   operations, the current posture attribute data of the network
   infrastructure endpoint will be made available.  NETCONF also



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   provides a variety of filtering mechanisms (XPath, subtree, content
   matching, etc.) to trim down the posture attribute data that is
   collected from the endpoint.  Given that NETCONF is widely adopted by
   network infrastructure vendors, it may useful to consider this
   protocol as a standardized mechanism for collecting posture attribute
   data from network infrastructure endpoints.

   As a side note, members of the OVAL Community have also developed a
   proposal to extend the OVAL Language to support the assessment of
   NETCONF configuration data
   <https://github.com/OVALProject/Sandbox/blob/master/x-netconf-
   definitions-schema.xsd>.  The proposal leverages XPath to extract the
   posture attribute data of interest from the XML data returned by
   NETCONF.  The collected posture attribute data can then be evaluated
   using OVAL Definitions and the results of the evaluation can be
   expressed as OVAL Results.  While this proposal is not currently part
   of the OVAL Language, it may be worth considering.

G.3.5.2.1.3.  SNMP-Based Collection

   The SNMP, previously introduced in Appendix G.3.4.2.1.3, defines a
   protocol for managing and retrieving posture attribute data from
   endpoints on a network [RFC3411].  SNMP provides three protocol
   operations [RFC3416] (GetRequest, GetNextRequest, and GetBulkRequest)
   for retrieving posture attribute data defined by MIB objects.  Upon
   successful completion of these operations, the requested posture
   attribute data of the endpoint will be made available to the
   requesting application.  Given that SNMP is widely adopted by
   vendors, and the MIBs that define posture attribute data on an
   endpoint are highly extensible, it may useful to consider this
   protocol as a standardized mechanism for collecting posture attribute
   data from endpoints in an enterprise.

G.3.6.  Evaluation Guidance

G.3.6.1.  Configuration Evaluation Guidance

   The evaluation guidance is applied by evaluators during posture
   assessment of an endpoint.  This guidance must be able to reference
   or be associated with the following previously defined information
   elements:

   o  configuration item identifiers,

   o  platform configuration identifiers, and

   o  collected Platform Configuration Posture Attributes.




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G.3.6.1.1.  Related Work

G.3.6.1.1.1.  Open Vulnerability and Assessment Language

   A general overview of OVAL was provided previously in
   Appendix G.3.2.1.1.2.1.  The OVAL Definitions model provides an
   extensible framework for making assertions about the state of posture
   attribute data collected from an endpoint.  Guidance written against
   this model consists of one or more OVAL Tests, which can be logically
   combined, where each OVAL Test defines what posture attributes should
   be collected from an endpoint (as OVAL Objects) and optionally
   defines the expected state of the posture attributes (as OVAL
   States).  While the OVAL Definitions model may be a useful starting
   point for evaluation guidance, it will likely require some changes to
   decouple collection and evaluation concepts to satisfy the needs of
   the SACM community.

G.3.6.1.1.2.  XCCDF Rule

   A general description of XCCDF was provided in Appendix G.3.3.1.1.1.
   As noted there, an XCCDF document represents a checklist of items
   against which a given endpoint's state is compared and evaluated.  An
   XCCDF Rule represents one assessed item in this checklist.  A Rule
   contains both a prose description of the assessed item (either for
   presentation to the user in a tool's user interface, or for rendering
   into a prose checklist for human consumption) and can also contain
   instructions to support automated evaluation of the assessed item, if
   such automated assessment is possible.  Automated assessment
   instructions can be provided either within the XCCDF Rule itself, or
   by providing a reference to instructions expressed in other
   languages, such as OVAL.

   In order to support greater flexibility in XCCDF, checklists can be
   tailored to meet certain needs.  One way to do this is to enable or
   disable certain rules that are appropriate or inappropriate to a
   given endpoint, respectively.  For example, a single XCCDF checklist
   might contain check items to evaluate the configuration of an
   endpoint's operating system.  An endpoint deployed in an enterprise's
   DMZ might need to be locked down more than a common internal
   endpoint, due to the greater exposure to attack.  In this case, some
   operating system configuration requirements for the DMZ endpoint
   might be unnecessary for the internal endpoint.  Nonetheless, most
   configuration requirements would probably remain applicable to both
   environments (providing a common baseline for configuration of the
   given operating system) and thus be common to the checking
   instructions for both types of endpoints.  XCCDF supports this by
   allowing a single checklist to be defined, but then tailored to the
   needs of the assessed endpoint.  In the previous example, some Rules



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   that apply only to the DMZ endpoint would be disabled during the
   assessment of an internal endpoint and would not be exercised during
   the assessment or count towards the assessment results.  To
   accomplish this, XCCDF uses the CPE Applicability Language.  By
   enhancing this applicability language to support other aspects of
   endpoint characterization (see Appendix G.3.3.1.3), XCCDF will also
   benefit from these enhancements.

   In addition, XCCDF Rules also support parameterization, allowing
   customization of the expected value for a given check item.  For
   example, the DMZ endpoint might require a password of at least 12
   characters, while an internal endpoint may only need 8 or more
   characters in its password.  By employing parameterization of the
   XCCDF Rule, the same Rule can be used when assessing either type of
   endpoint, and simply be provided with a different target parameter
   each time to reflect the different role-based requirements.  Sets of
   customizations can be stored within the XCCDF document itself: XCCDF
   Values store parameters values that can be used in tailoring, while
   XCCDF Profiles store sets of tailoring instructions, including
   selection of certain Values as parameters and the enabling and
   disabling of certain Rules.  The tailoring capabilities supported by
   XCCDF allow a single XCCDF document to encapsulate configuration
   evaluation guidance that applies to a broad range of endpoint roles.

G.3.7.  Evaluation Result Reporting

G.3.7.1.  Configuration Evaluation Results

   The evaluation guidance applied during posture assessment of an
   endpoint to customize the behavior of evaluators.  Guidance can be
   used to define specific result output formats or to select the level-
   of-detail for the generated results.  This guidance must be able to
   reference or be associated with the following previously defined
   information elements:

   o  configuration item identifiers,

   o  platform configuration identifiers, and

   o  collected Platform Configuration Posture Attributes.

G.3.7.1.1.  Related Work

G.3.7.1.1.1.  XCCDF TestResults

   A general description of the eXtensible Configuration Checklist
   Description Format (XCCDF) was provided in section
   Appendix G.3.3.1.1.1.  The XCCDF TestResult structure captures the



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   outcome of assessing a single endpoint against the assessed items
   (i.e., XCCDF Rules) contained in an XCCDF instance document.  XCCDF
   TestResults capture a number of important pieces of information about
   the assessment including:

   o  The identity of the assessed endpoint.  See Appendix G.3.3.1.1.2
      for more about XCCDF structures used for endpoint identification.

   o  Any tailoring of the checklist that might have been employed.  See
      Appendix G.3.6.1.1.2 for more on how XCCDF supports tailoring.

   o  The individual results of the assessment of each enabled XCCDF
      Rule in the checklist.  See Appendix G.3.6.1.1.2 for more on XCCDF
      Rules.

   The individual results for a given XCCDF Rule capture only whether
   the rule "passed", "failed", or experienced some exceptional
   condition, such as if an error was encountered during assessment.
   XCCDF 1.2 Rule results do not capture the actual state of the
   endpoint.  For example, an XCCDF Rule result might indicate that an
   endpoint failed to pass requirement that passwords be of a length
   greater than or equal to 8, but it would not capture that the
   endpoint was, in fact, only requiring passwords of 4 or more
   characters.  It may, however, be possible for a user to discover this
   information via other means.  For example, if the XCCDF Rule uses an
   OVAL Definition to effect the Rule's evaluation, then the actual
   endpoint state may be captured in the corresponding OVAL System
   Characteristics file.

   The XCCDF TestResult structure does provide a useful structure for
   understanding the overall assessment that was conducted and the
   results thereof.  The ability to quickly determine the Rules that are
   not complied with on a given endpoint allow administrators to quickly
   identify where remediation needs to occur.

G.3.7.1.1.2.  Open Vulnerability and Assessment Language

   A general overview of OVAL was provided previously in
   Appendix G.3.2.1.1.2.1.  OVAL Results provides a model for expressing
   the results of the assessment of the actual state of the posture
   attribute values collected of an endpoint (represented as an OVAL
   System Characteristics document) against the expected posture
   attribute values (defined in an OVAL Definitions document.  Using
   OVAL Directives, the granularity of OVAL Results can also be
   specified.  The OVAL Results model may be useful in providing a
   format for capturing the results of an assessment.





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G.3.7.1.1.3.  Asset Summary Reporting

   A general overview of ASR was provided previously in
   Appendix G.3.5.1.1.1.  As ASR provides a way to report summary
   information about assets, it can be used within the SACM Architecture
   to provide a way to aggregate asset information for later use.  It
   makes no assertions about the data formats used by the assessment,
   but rather provides an XML, record-based way to collect aggregated
   information about assets.

   By using ASR to collect this summary information within the SACM
   Architecture, one can provide a way to encode the details used by
   various reporting requirements, including user-definable reports.

G.3.7.1.1.4.  ARF

   A general overview of ARF was provided previously in
   Appendix G.3.3.1.2.1.  Because ARF is data model agnostic, it can
   provide a flexible format for exchanging collection and evaluation
   information from endpoints.  It additionally provides a way to encode
   relationships between guidance and assets, and as such, can be used
   to associate assessment results with guidance.  This could be the
   guidance that directly triggered the assessment, or for guidance that
   is run against collected posture attributes located in a central
   repository.

G.3.7.2.  Software Inventory Evaluation Results

   The results of an evaluation of an endpoint's software inventory
   against an authorized software list.  The authorized software list
   represents the policy for what software units are allowed,
   prohibited, and mandatory for an endpoint.

Appendix H.  Graph Model

   TODO: Write text on how the information model above can be realized
   in this kind of graph model.

   The graph model describes how security information is structured,
   related, and accessed.  Control of operations to supply and/or access
   the data is architecturally distinct from the structuring of the data
   in the information model.  Authorization may be applied by the
   Control Plane (as defined in the SACM Architecture
   [I-D.ietf-sacm-architecture]) to requests for information from a
   consumer or requests for publication from a provider, and may also be
   applied by a provider to a direct request from a consumer.





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   This architecture addresses information structure independently of
   the access/transport of that information.  This separation enables
   scalability, customizability, and extensibility.  Access to provide
   or consume information is particularly suited to publish/subscribe/
   query data transport and data access control models.

   This graph model is a framework that:

   o  Facilitates the definition of extensible data types that support
      SACM's use cases

   o  Provides a structure for the defined data types to be exchanged
      via a variety of data transport models

   o  Describes components used in information exchange, and the objects
      exchanged

   o  Captures and organizes evolving information and information
      relationships for multiple data publishers

   o  Provides access to the published information via publish, query,
      and subscribe operations

   o  Leverages the knowledge and experience gained from incorporating
      TNC IF-MAP into many disparate products that have to integrate and
      share an information model in a scalable, extensible manner

H.1.  Background: Graph Models

   Knowledge is often represented with graph-based formalisms.  A common
   formalism defines a graph as follows:

   o  A set of *vertices*

   o  A set of *edges*, each connecting two vertices (technically, an
      edge is an ordered pair of vertices)

   o  A set of zero or more *properties* attached to each vertices and
      edges.  Each property consists of a type and a optionally a value.
      The type and the value are typically just strings











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      +------------------+                 +-----------------+
      | Id:          1   |   parent-of     |Id:          2   |
      | Given name:  Sue | --------------> |Given name:  Ann |
      | Family name: Wong|                 |Family name: Wong|
      +------------------+                 +-----------------+

            A VERTEX          AN EDGE           A VERTEX

                Figure 10: Knowledge represented by a graph

   A pair of vertices connected by an edge is commonly referred to as a
   triple that comprises subject, predicate and object.  For example,
   subject = Sue Wong, predicate = is-parent-of, object = Ann Wong.  A
   common language that uses this representation is the Resource
   Description Framework (RDF) [W3C.REC-rdf11-concepts-20140225].

H.2.  Graph Model Overview

   The proposed model, influenced by IF-MAP, is a labeled graph: each
   vertex has a label.

   A table of synonyms follows.

   +----------------+-----------------+--------------------------------+
   | Graph Theory   | Graph Databases | IF-MAP and This Internet Draft |
   +----------------+-----------------+--------------------------------+
   | Vertex or Node | Node            | -                              |
   | Label          | -               | Identifier                     |
   | Edge           | Edge            | Link                           |
   | -              | Property        | Metadata Item                  |
   +----------------+-----------------+--------------------------------+

   In this mode, identifiers and metadata have hierarchical structure.

   The graphical aspect makes this model well suited to non-hierarchical
   relationships, such as connectivity in a computer network.

   Hierarchical properties allow this model to accommodate structures
   such as YANG [RFC6020] data models.

H.3.  Identifiers

   Each identifier is an XML element.  For extensibility, schemas use
   xsd:anyAttribute and such.

   Alternately, this model could be changed to use another hierarchical
   notation, such as JSON.




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   Identifiers are unique: two different vertices cannot have equivalent
   identifiers.

   An identifier has a type.  There is a finite, but extensible, set of
   identifier types.  If the identifier is XML, the type is based on the
   XML schema.

   In IF-MAP, standard identifier types include IP address, MAC address,
   identity, and overlay network.  Additional identifier types will need
   to be standardized for SACM use cases.

   Any number of metadata items can be attached to an identifier.

   Some identifiers, especially those relating to identity, address, and
   location, require the ability to specify an administrative domain
   (such as AD domain, L2 broadcast domain / L3 routing domain, or
   geographic domain) in order to differentiate between instances with
   the same name occurring in different realms.

H.4.  Links

   A link can be thought of as an ordered pair of identifiers.

   Any number of metadata items can be attached to a link.

H.5.  Metadata

   A metadata item is the basic unit of information, and is attached to
   an identifier or to a link.

   A given metadata item is an XML document.  In IF-MAP metadata items
   are generally small.  However, larger ones, such as YANG data models,
   can also fit.  For extensibility, the XML schemas of metadata items
   use xsd:anyAttribute and such.

   Alternately, this model could be changed to use another hierarchical
   notation, such as JSON.

   A metadata item has a type.  There is a finite, but extensible, set
   of metadata types.  If the metadata item is XML, the type is based on
   the XML schema.  An example metadata type is
   http://www.trustedcomputinggroup.org/2010/IFMAP-METADATA/2#device-
   characteristic.

   TNC IF-MAP Metadata for Network Security [TNC-IF-MAP-NETSEC-METADATA]
   and TNC IF-MAP Metadata for ICS Security [TNC-IF-MAP-ICS-METADATA]
   define many pertinent metadata types.  More will need to be
   standardized for SACM use cases.



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H.6.  Use for SACM

   Many of the information elements can be represented as vertices, and
   many of the relationships can be represented as edges.

   Identifiers are like database keys.  For example, there would be
   identifiers for addresses, identities, unique endpoint identifiers,
   software component identifiers, and hardware component identifiers.
   The inventory of software instances and hardware instances within an
   endpoint might be expressed using a single YANG description, as a
   single metadata item in the graph.  Where to put Endpoint Attribute
   Assertions, Evaluation Results, and the like is an open question.

H.7.  Provenance

   Provenance helps to protect the SACM ecosystem against a misled or
   malicious provider.

   The provenance of a metadata item includes:

   o  The time when the item was produced

   o  The component that produced the item, including its software and
      version

   o  The policies that governed the producing component, with versions

   o  The method used to produce the information (e.g., vulnerability
      scan)

   How provenance should be expressed is an open question.  For
   reference, in IF-MAP provenance of a metadata item is expressed
   within the metadata item [TNC-IF-MAP-NETSEC-METADATA].  For example,
   there is a top-level XML attribute called "timestamp".

   It is critical that provenance be secure from tampering.  How to
   achieve that security is out of scope of this document.

H.8.  Extensibility

   Anyone can define an identifier type or a metadata type, by creating
   an XML schema (or other specification).  There is no need for a
   central authority.  Some deployments may exercise administrative
   control over the permitted identifier types and metadata types;
   others may leave components free rein.

   A community of components can agree on and use new identifier and
   metadata types, if the administrators allow it.  This allows rapid



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   innovation.  Intermediate software that conveys graph changes from
   one component to another does not need changes.  Components that do
   not understand the new types do not need changes.  Accordingly, a
   consumer normally ignores metadata types and identifier types it does
   not understand.

   As a proof point for this agility, the original use cases for TNC IF-
   MAP Binding for SOAP [TNC-IF-MAP-SOAP-Binding] were addressed in TNC
   IF-MAP Metadata for Network Security [TNC-IF-MAP-NETSEC-METADATA].
   Some years later an additional, major set of use cases, TNC IF-MAP
   Metadata for ICS [TNC-IF-MAP-ICS-METADATA], were specified and
   implemented.

Authors' Addresses

   David Waltermire (editor)
   National Institute of Standards and Technology
   100 Bureau Drive
   Gaithersburg, Maryland  20877
   USA

   Email: david.waltermire@nist.gov


   Kim Watson
   United States Department of Homeland Security
   DHS/CS&C/FNR
   245 Murray Ln. SW, Bldg 410
   MS0613
   Washington, DC  20528
   USA

   Email: kimberly.watson@hq.dhs.gov


   Clifford Kahn
   Pulse Secure, LLC
   2700 Zanker Road, Suite 200
   San Jose, CA  95134
   USA

   Email: cliffordk@pulsesecure.net









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   Lisa Lorenzin
   Pulse Secure, LLC
   2700 Zanker Road, Suite 200
   San Jose, CA  95134
   USA

   Email: llorenzin@pulsesecure.net


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

   Email: dhaynes@mitre.org



































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