wdiff rfc8412.original rfc8412.txt

SACM
Internet Engineering Task Force (IETF) C. Schmidt
Internet-Draft
Request for Comments: 8412 D. Haynes
Intended status:
Category: Standards Track C. Coffin
Expires: October 8, 2018
ISSN: 2070-1721 The MITRE Corporation
D. Waltermire
National Institute of Standards and Technology
J. Fitzgerald-McKay
United States National Security Agency
April 6,
July 2018

Software Inventory Message and Attributes (SWIMA) for PA-TNC
draft-ietf-sacm-nea-swima-patnc-05

Abstract

This document extends "PA-TNC: A Posture Attribute (PA) Protocol
Compatible with Trusted Network Connect (TNC)" (RFC 5792) by
providing specific attributes and message exchanges to allow
endpoints to report their installed software inventory information to
a NEA server, Server, as defined in "Network Endpoint Assessment (NEA):
Overview and Requirements" (RFC 5209).

Status of This Memo

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This Internet-Draft will expire on October 8, 2018.
https://www.rfc-editor.org/info/rfc8412.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 ....................................................4
1.1. Network Endpoint Assessment (NEA) . . . . . . . . . . . . 5 ..........................6
1.2. Conventions Used in This Document . . . . . . . . . . . . 6 ..........................7
1.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 7 ................................................7
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 8 ......................................................8
2.1. Supported Use Cases . . . . . . . . . . . . . . . . . . . 8 ........................................8
2.1.1. Use Software Inventory as an Access Control Factor . 8 ..8
2.1.2. Central Stores of Up-to-Date Endpoint
Software Inventory Data . . . . . . . . . . . . . . . . . . . 8 .............................9
2.1.3. PA-TNC Use Cases . . . . . . . . . . . . . . . . . . 9 ....................................9
2.2. Non-supported Use Cases . . . . . . . . . . . . . . . . . 9 That Are Not Supported ...........................9
2.3. SWIMA Requirements . . . . . . . . . . . . . . . . . . . 10 ........................................10
2.4. Non-SWIMA Requirements . . . . . . . . . . . . . . . . . 11 ....................................11
2.5. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 11 ...............................................12
2.6. Non-Assumptions . . . . . . . . . . . . . . . . . . . . . 11 Assumptions Not Made ......................................12
3. System Requirements . . . . . . . . . . . . . . . . . . . . . 12 ............................................12
3.1. Data Sources . . . . . . . . . . . . . . . . . . . . . . 12 ..............................................13
3.2. Data Models . . . . . . . . . . . . . . . . . . . . . . . 13 ...............................................14
3.3. Basic Attribute Exchange . . . . . . . . . . . . . . . . 15 ..................................16
3.4. Core Software Reporting Software-Reporting Information . . . . . . . . . . . 16 .......................17
3.4.1. Software Identifiers . . . . . . . . . . . . . . . . 16 ...............................17
3.4.2. Data Model Type . . . . . . . . . . . . . . . . . . . 17 ....................................19
3.4.3. Record Identifiers . . . . . . . . . . . . . . . . . 18 .................................19
3.4.4. Software Locators . . . . . . . . . . . . . . . . . . 18 ..................................20
3.4.5. Source Identifiers . . . . . . . . . . . . . . . . . 19 .................................21
3.4.6. Using Software and Record Identifiers in
SWIMA Attributes . . . . . . . . . . . . . . . . . . . . . 21 ...................................22
3.5. Targeted Requests . . . . . . . . . . . . . . . . . . . . 21 .........................................22
3.6. Monitoring Changes in an Endpoint's Software
Inventory Evidence Collection . . . . . . . . . . . . . . . . . . . 22 .............................23
3.7. Reporting Change Events . . . . . . . . . . . . . . . . . 25 ...................................26
3.7.1. Event Identifiers . . . . . . . . . . . . . . . . . . 25 ..................................27
3.7.2. Core Event Tracking Event-Tracking Information . . . . . . . . . . . 27 ....................28
3.7.3. Updating Inventory Knowledge Based on Events . . . . 27 .......29
3.7.4. Using Event Records in SWIMA Attributes . . . . . . . 28 ............29
3.7.5. Partial and Complete Lists of Event Records
in SWIMA Attributes . . . . . . . . . . . . . . . . . . . . . 28 ................................30
3.7.6. Synchronizing Event Identifiers and Epochs . . . . . 30 .........32
3.8. Subscriptions . . . . . . . . . . . . . . . . . . . . . . 32 .............................................33
3.8.1. Establishing Subscriptions . . . . . . . . . . . . . 32 .........................34
3.8.2. Managing Subscriptions . . . . . . . . . . . . . . . 33 .............................35
3.8.3. Terminating Subscriptions . . . . . . . . . . . . . . 33 ..........................36
3.8.4. Subscription Status . . . . . . . . . . . . . . . . . 34 ................................36
3.8.5. Fulfilling Subscriptions . . . . . . . . . . . . . . 34 ...........................37
3.8.5.1. Subscriptions Reporting That Report Inventories . . . . . . . 36 .....38
3.8.5.2. Subscriptions Reporting That Report Events . . . . . . . . . 36 ..........38
3.8.5.3. Targeted Subscriptions . . . . . . . . . . . . . 37 ....................40
3.8.5.4. No Subscription Consolidation . . . . . . . . . . 38 .............40
3.8.5.5. Delayed Subscription Fulfillment . . . . . . . . 38 ..........41
3.9. Error Handling . . . . . . . . . . . . . . . . . . . . . 39 ............................................41
4. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 41 .......................................................43
4.1. Direct Response to a SWIMA Request . . . . . . . . . . . 41 ........................44
4.2. Subscription-Based Response . . . . . . . . . . . . . . . 41 ...............................45
4.3. Required Exchanges . . . . . . . . . . . . . . . . . . . 42 ........................................45
5. Software Inventory Messages and Attributes . . . . . . . . . 42 .....................46
5.1. PA Subtype (AKA (aka PA-TNC Component Type) . . . . . . . . . 42 ....................46
5.2. SWIMA Attribute Overview . . . . . . . . . . . . . . . . 43 ..................................46
5.3. Message Diagram Syntax . . . . . . . . . . . . . . . . . 45 ....................................48
5.4. Normalization of Text Encoding ............................49
5.5. Request IDs ...............................................49
5.6. SWIMA Attribute Enumeration . . . . . . . . . . . . . . . 45
5.5. Normalization of Text Encoding . . . . . . . . . . . . . 45
5.6. Request IDs . . . . . . . . . . . . . . . . . . . . . . . 45 .............................................50
5.7. SWIMA Request . . . . . . . . . . . . . . . . . . . . . . 46
5.8. Software Identifier Inventory . . . . . . . . . . . . . . 50
5.9. .............................54
5.8. Software Identifier Events . . . . . . . . . . . . . . . 54
5.10. ................................58
5.9. Software Inventory . . . . . . . . . . . . . . . . . . . 59
5.11. ........................................64
5.10. Software Events . . . . . . . . . . . . . . . . . . . . . 62
5.12. ..........................................67
5.11. Subscription Status Request . . . . . . . . . . . . . . . 67
5.13. ..............................72
5.12. Subscription Status Response . . . . . . . . . . . . . . 68
5.14. .............................73
5.13. Source Metadata Request . . . . . . . . . . . . . . . . . 70
5.15. ..................................75
5.14. Source Metadata Response . . . . . . . . . . . . . . . . 71
5.16. .................................76
5.15. PA-TNC Error as Used by SWIMA . . . . . . . . . . . . . . 73
5.16.1. ............................78
5.15.1. SWIMA_ERROR,
SWIMA_SUBSCRIPTION_DENIED_ERROR SWIMA_SUBSCRIPTION_DENIED_ERROR, and
SWIMA_SUBSCRIPTION_ID_REUSE_ERROR Information . . . 76
5.16.2. .....81
5.15.2. SWIMA_RESPONSE_TOO_LARGE_ERROR Information . . . . . 77
5.16.3. ........83
5.15.3. SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR Information . . 79 ..85
6. Supported Data Models . . . . . . . . . . . . . . . . . . . . 81 ..........................................87
6.1. ISO 2015 SWID Tags using Using XML . . . . . . . . . . . . . . 81 ..............................87
6.1.1. Guidance on Normalizing Source Data to ISO 2015
SWID Tags using Using XML . . . . . . . . . . . . . . . . . . . 81 ................................87
6.1.2. Guidance on Creation of Software Identifiers from
ISO 2015 SWID Tags . . . . . . . . . . . . . . . . . . . 82 .................................88
6.2. ISO 2009 SWID Tags using Using XML . . . . . . . . . . . . . . 82 ..............................88
6.2.1. Guidance on Normalizing Source Data to ISO 2009
SWID Tags using Using XML . . . . . . . . . . . . . . . . . . . 82 ................................88
6.2.2. Guidance on Creation of Software Identifiers from
ISO 2009 SWID Tags . . . . . . . . . . . . . . . . . . . 83 .................................89
7. Relationship to Other Specifications . . . . . . . . . . . . 83 ...........................89
8. Security Considerations . . . . . . . . . . . . . . . . . . . 84 ........................................90
8.1. Evidentiary Value of Software Inventory Evidence Records 84 ..90
8.2. Sensitivity of Collected Records . . . . . . . . . . . . 85 ..........................91
8.3. Integrity of Endpoint Records . . . . . . . . . . . . . . 86 .............................92
8.4. SWIMA-PC Access Permissions . . . . . . . . . . . . . . . 86 ...............................92
8.5. Sanitization of Record Fields . . . . . . . . . . . . . . 87
8.6. PA-TNC Security Threats . . . . . . . . . . . . . . . . . 87
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 87
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 88
10.1. PA Subtypes . . . . . . . . . . . . . . . . . . . . . . 88
10.2. Registry Record Fields .............................93
8.6. PA-TNC Security Threats ...................................93
9. Privacy Considerations .........................................93
10. IANA Considerations ...........................................94
10.1. Guidance for the Designated Experts ......................94
10.2. PA Subtypes ..............................................95
10.3. PA-TNC Attribute Types . . . . . . . . . . 88
10.3. Registry for ...................................96
10.4. PA-TNC Error Codes . . . . . . . . . . . . 89
10.4. Registry for .......................................97
10.5. Software Data Models . . . . . . . . . . . 90 Model Types ................................97
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 91 ....................................................98
11.1. Normative References . . . . . . . . . . . . . . . . . . 91 .....................................98
11.2. Informative References . . . . . . . . . . . . . . . . . 92
11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 93 ...................................99
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 93 ...............................................101

1. Introduction

Knowing the list of the software installed on endpoints is useful to
understand and maintain the security state of a network. For
example, if an enterprise policy requires the presence of certain
software and prohibits the presence of other software, reported
software installation information can be used to indicate compliance
and non-compliance with these requirements. Endpoint software
installation inventory lists (hereinafter "software inventories") can
further be used to determine an endpoint's exposure to attack based
on comparison to of vulnerability or threat alerts against identified
software's patch level patch-level data. These are some of the highly useful
management use cases supported by software inventory data.

Software Inventory Message and Attributes (SWIMA) for PA-TNC (see
"PA-TNC: A Posture Attribute (PA) Protocol Compatible with Trusted
Network Connect (TNC)" [RFC5792]) provides a standardized method for
exchanging software inventory data that includes a unique software identifier Software
Identifier associated with a specific version of a software product.
SWIMA can also convey metadata about software products beyond this
identifier. SWIMA enables software identification, installation, and
characterization information to be
be transported to a central server
from any endpoint that supports this specification. Such information
can come from multiple sources, including tag files (such as ISO SWID
Software Identification (SWID) tags [SWID15]), reports from
third party
third-party inventory tools, output from package managers, and other
sources. SWIMA does not standardize how software is detected,
instead relying on a set of "data sources" to provide information
about installed software. Instead, SWIMA provides a flexible transport
capable of conveying this information information, regardless of how it is
expressed.

This specification is designed to only report software that is
installed on a target endpoint. In particular, it does not monitor
or report information about what software is running on the endpoint.
Likewise, it is not intended to report individual files, libraries,
installation packages, or similar artifacts. While all of this
information has its uses, this information requires different
metadata and monitoring methods. As a result, this specification
focuses solely on software inventory information, leaving the
reporting of other classes of endpoint information to other
specifications.

Note that while this specification focuses on "software inventory",
the mechanisms it describes could also be used to convey information
about firmware and operating systems associated with an endpoint.
The focus on software throughout this document should not be read as
excluding the use of SWIMA for these other purposes.

This specification defines a new set of PA-TNC attributes, which attributes; these
attributes are used to communicate requests for software inventory
information and software installation change events. The exchange of
these messages allows software inventory information to be sent to a NEA
Network Endpoint Assessment (NEA) Server, which can make this
information available to other applications.

Part of the motivation for the development of SWIMA was to support
the IETF's Security Automation and Continuous Monitoring (SACM)
architecture. More details about SWIMA's role in SACM appear in
Section 7. However, SWIMA has no dependencies on any part of SACM
and is usable wherever the NEA architecture is employed.

1.1. Network Endpoint Assessment (NEA)

SWIMA defines extensions to the PA-TNC specification, which is specification [RFC5792]; these
extensions are part of the Network Endpoint Assessment (NEA) NEA architecture. The NEA specifications
define an open solution architecture that enables network operators
to collect and utilize information about endpoint configuration and
state. This information can be used to enforce
policies, policies and monitor
endpoint health, and for among many other activities. Information about the
software present on an endpoint is an important consideration for
such activities. The new PA-TNC attributes defined in this document
are used to communicate software inventory evidence, collected from a
range of possible sources, from the posture
collector Posture Collector on the endpoint
to the posture validator Posture Validator on a NEA Server using the PA-TNC interface,
as shown in Figure 1 below.

+-------------+ +--------------+
| Posture | <--------PA--------> | Posture |
| Collectors | | Validators |
| (1 .. N) | | (1 .. N) |
+-------------+ +--------------+
| |
| |
| |
+-------------+ +--------------+
| Posture | | Posture |
| Broker | <--------PB--------> | Broker |
| Client | | Server |
+-------------+ +--------------+
| |
| |
+-------------+ +--------------+
| Posture | | Posture |
| Transport | <--------PT--------> | Transport |
| Client | | Server |
| (1 .. N) | | (1 .. N) |
+-------------+ +--------------+
NEA CLIENT NEA SERVER

Figure 1: NEA Reference Model

To better understand this specification, the reader should review the
NEA reference architecture as described in the Network "Network Endpoint
Assessment (NEA): Overview and Requirements Requirements" [RFC5209]. The reader
should also review the PA-TNC interfaces as defined in RFC 5792
[RFC5792].

This document is based on standards published by the Trusted
Computing Group's Trusted Network Communications (TNC) workgroup. workgroup (see
<https://trustedcomputinggroup.org/>). The TNC and NEA architectures
are interoperable interoperable, and many components are equivalent.

1.2. Conventions Used in This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

1.3. Definitions

This section defines terms with that have special meaning within this
document.

o SWIMA-PC - A NEA Posture Collector (PC) that interprets SWIMA
Attributes
attributes sent by SWIMA-PVs and which that conforms to this
specification. Note that such a posture collector Posture Collector might also
support other PA-TNC exchanges beyond those defined herein.

o SWIMA-PV - A NEA Posture Validator (PV) that interprets SWIMA
Attributes
attributes sent by SWIMA-PCs and which that conforms to this
specification. Note that such a posture verifier Posture Validator might also
support other PA-TNC exchanges beyond those defined herein.

o SWIMA Attribute - This is a A PA-TNC attribute (as defined in RFC 5792
[RFC5792] extension as
[RFC5792]) whose structure and behavior is defined in this
specification.

o Endpoint's Software Inventory Evidence Collection - The set of
information regarding the set of software installed on an
endpoint. An endpoint's software inventory evidence collection Software Inventory Evidence Collection
might include information created by or derived from multiple
sources, including but not limited to SWID tag files deposited on
the file system filesystem during software installation, information generated
by software discovery tools, and information dynamically generated
by a software or package management system on an endpoint.

o Software Inventory Evidence Record - The Part of the endpoint's
Software Inventory Evidence Collection (which is composed of "records".
"records"). Each record corresponds to one installed instance of
a particular software product as reported by some data source. It
is possible for a single installed instance to have multiple software inventory evidence
records
Software Inventory Evidence Records in an endpoint's Software
Inventory Evidence Collection - -- this can happen if multiple
sources all report the same software installation instance.

o Software Identifier - A string associated with a specific version
of a specific software product. These identifiers are derived
from the records used to describe software products. SWIMA does
not limit the formats of these records, nor does it enforce that the same format be
populated the same way by
all data sources. sources populate records using the same format. As such,
while each
software identifier Software Identifier uniquely identifies a specific
software product, the same software product might be associated
with multiple software
identifiers Software Identifiers reflecting differences between
different data sources and supported record formats.

2. Background

2.1. Supported Use Cases

This section describes the use cases supported by this specification.
The primary use of exchanging software inventory information over the
PA-TNC interface is to enable a challenger (e.g., a NEA Server) to
obtain inventory evidence about some system in a way that conforms to
NEA procedures and expressed using a standard format. procedures. Collected software information can support a range
of security activities activities, including determining whether an endpoint is
permitted to connect to the enterprise, determining which endpoints
contain software that requires patching, and similar activities.

2.1.1. Use Software Inventory as an Access Control Factor

Some enterprises might define security policies that require
connected endpoints to have certain pieces of security software
installed. By contrast, some security policies might prevent access
to resources by endpoints that have certain prohibited pieces of
software installed, since such applications might pose a security
risk. To support such policies, the NEA Server needs to collect
software inventory evidence from a target endpoint that is seeking to
initiate or continue connectivity to the enterprise resource.

Based on this specification, the SWIMA-PC can provide a complete or
partial inventory to the SWIMA-PV as required to determine policy
compliance. The SWIMA-PV can then use this as evidence of compliance
or non-compliance to make a policy-based access decision.

2.1.2. Central Stores of Up-to-Date Endpoint Software Inventory Data

Many tools use information about an endpoint's software inventory to
monitor and enforce the security of a network. For example, a
software patching
software-patching tool needs to determine if there is out-of-date
software installed that needs to be updated. A vulnerability
management tool needs to identify endpoints with known vulnerable
software installed (patched or otherwise) to gauge an endpoint's
relative exposure to attack. A license management tool needs to
verify that all installed software within the enterprise is accounted
for. A central repository representing an up-to-date understanding
of each endpoint's software inventory facilitates these activities.
Multiple tools can share such a repository repository, ensuring that software
inventory information is collected more frequently and efficiently,
leading to a more complete and consistent understanding of installed
software state as compared to each tool collecting the same inventory
information from endpoints individually.

This specification supports these activities through a number of
mechanisms. As noted above, a SWIMA-PC can provide a complete list
of software present in an endpoint's Software Inventory Evidence
Collection to the SWIMA-PV, which can then pass this information on
to a central repository, such as a Configuration Management Database
(CMDB) or similar application. In addition, SWIMA-PCs are required
to be able to monitor for changes to an endpoint's Software Inventory
Evidence Collection in near real-time real time and can be requested to
immediately push reports of detected changes to the SWIMA-PV. Thus,
any central repository fed by a SWIMA-PV receiving inventory
information can be updated quickly after a change occurs. Keeping a
central repository synchronized with current software inventory
information in this way allows tools to make efficient decisions
based on up-to-date, consistent information.

2.1.3. PA-TNC Use Cases

SWIMA is intended to operate over the PA-TNC interface and, as such,
are
is intended to meet the use cases set out in the PA-TNC
specification.

2.2. Non-supported Use Cases That Are Not Supported

Some use cases not covered by this specification include:

o Addressing how the endpoint's Software Inventory Evidence
Collection is populated. In particular, NEA components are not
expected to perform software discovery activities beyond compiling
information in an endpoint's Software Inventory Evidence
Collection. This collection might come from multiple sources on
the endpoint (e.g., information generated dynamically by package
management tools or discovery tools, as well as SWID tag files
discovered on the file system). filesystem). While an enterprise might make use
of software discovery capabilities to identify installed software,
such capabilities are outside the scope of this specification.

o Converting inventory information expressed in a proprietary format
into formats used in the attributes described in this
specification. Instead, this specification focuses exclusively on
defining interfaces for the transportation of software information
information, expecting that reporting tools will converge around
some set of standardized formats for this information.

o Mechanisms for a posture validator Posture Validator to request a specific list of
software information based on arbitrary software properties. For
example, requesting only information about software from a
particular vendor is not supported. After the endpoint's Software
Inventory Evidence Collection has been copied to some central
location, such as the CMDB, processes there can perform queries
based on any criteria present in the collected information, but
this specification does not address using such queries to
constrain the initial collection of this information from the
endpoint.

o Use of properties of certain sources of software information that
might facilitate local tests (i.e., on the endpoint) of endpoint
state. For example, the optional package_footprint field of an
ISO SWID tag can contain a list of files and hash values
associated with the software indicated by the tag. Tools on the
endpoint can use the values in this field to test for the presence
of the indicated files. Successful evaluation of such tests leads
to greater assurance that the indicated software is present on the
endpoint. Currently, most SWID tag creators do not provide values
for tag fields that support local testing. For this reason, the
added complexity of supporting endpoint testing using these fields
is out of scope for this specification, but this topic may be
considered in a future version.

2.3. SWIMA Requirements

Below are the requirements that the SWIMA specification is required
to must meet in order to
successfully play its role in the NEA architecture.

Efficient: The NEA architecture enables delay of network access
until the endpoint is determined not to pose a security threat to
the network network, based on its asserted integrity information. To
minimize user frustration, SWIMA ought to minimize overhead delays
and make PA-TNC communications as rapid and efficient as possible.

Scalable: SWIMA needs to be usable in enterprises that contain tens
of thousands of endpoints or more. As such, it needs to allow a
security tools to make decisions based on up-to-date information
about an endpoint's software inventory without creating an
excessive burden on the enterprise's network.

Support precise and complete historical reporting: This
specification outlines capabilities that support real-time
understanding of the state of endpoint endpoints in a network in a way that
can be used by other tools. One means of facilitating such an
outcome is for a CMDB to be able to contain information about all
endpoints connected to the enterprise for all points in time
between the endpoint's first connection and the present. In such
a scenario, it is necessary that any PC SWIMA-PC be able to report
any changes to its software inventory evidence collection Software Inventory Evidence Collection in near
real-time
real time while connected and, upon reconnection to the
enterprise, be able to update the NEA Server (and (and, through it it, the
CMDB) with regard to the state of its software inventory evidence
collection Software Inventory Evidence
Collection throughout the entire interval when it was not
connected.

2.4. Non-SWIMA Requirements

There are certain capabilities that users of the SWIMA specification might require but which
that are beyond the scope of SWIMA itself and need to be addressed by
other standards. This list is not exhaustive.

Confidentiality: The SWIMA specification does not define a mechanism for
confidentiality, nor is confidentiality automatically provided by
using the PA-TNC interface. In the NEA architecture,
confidentiality is generally provided by the underlying transport
protocols, such as the PT Binding binding to TLS [RFC6876] or PT-EAP Posture
(Posture Transport for Tunneled EAP Methods
[RFC7171] - Extensible Authentication Protocol
(EAP) Methods) [RFC7171]; see Section 7 for more information on
related standards. The information conveyed by SWIMA is often
sensitive in nature for both security (Section 8) and privacy
(Section 9) reasons. Those who implement SWIMA need to ensure
that appropriate NEA transport mechanisms are employed to meet
confidentiality requirements.

2.5. Assumptions

The Posture Broker Client and Posture Broker Server are assumed to
provide reliable delivery for PA-TNC messages and attributes sent
between the SWIMA-PCs and the SWIMA-PVs. Reliable delivery "Reliable delivery" means
that either a message is delivered or the sender is made aware of the
delivery failure. In the event that reliable delivery cannot be
provided, the Posture Collector or Posture Validator is expected to
terminate the connection. some SWIMA features, primarily subscriptions, might not
behave as expected.

2.6. Non-Assumptions Assumptions Not Made

This specification explicitly does not assume that software inventory
information exchanges reflect the software installation state of the
endpoint. This specification does not attempt to detect when the
endpoint is providing false information, either through malice or
error, but instead focuses on correctly and reliably providing the
reported Software Inventory Evidence Collection to the NEA Server.
Tools that employ the SWIMA standard can include methods to help
verify the accuracy of reports, but how those tools do so is beyond
the scope of this specification.

Similarly, this specification makes no assumption about the
completeness of the Software Inventory Evidence Collection's coverage
of the total set of software installed on the endpoint. It is
possible, and even likely, that some installed software is not
represented by a record in an endpoints endpoint's Software Inventory Evidence
Collection. Instead, SWIMA ensures that what does get reported is
reported consistently and that the software products that are
reported can be reliably tracked.

See Section 8 for more on this security consideration.

3. System Requirements

The

SWIMA specification facilitates the exchange of software inventory and event
information. Specifically, each application supporting SWIMA
includes a component known as the SWIMA-PC that receives messages sent with the SWIMA Attributes component type.
attributes. The SWIMA-PC is also responsible for sending appropriate
SWIMA Attributes attributes back to the SWIMA-PV in response. This section
outlines what software inventories and events are and the
requirements on SWIMA-PCs and SWIMA-PVs in order to support the
stated use cases of this specification.

3.1. Data Sources

The records in an endpoint's software inventory evidence collection Software Inventory Evidence Collection
come from one or more "sources". A source represents one collection
of software inventory information about the endpoint. Examples of
sources include, but are not limited to, ISO SWID tags deposited on
the filesystem and collected therefrom, information derived from
package managers (e.g., RPM or YUM), managers, and the output of software
inventory scanning inventory-scanning
tools.

There is no expectation that any one source of inventory information
will have either perfect or complete software inventory information.
For this reason, this specification supports the simultaneous use of
multiple sources of software inventory information. Each source
might have its own "sphere of expertise" and report the software
within that sphere. For example, a package manager would have an
excellent understanding of the software that it managed, managed but would not
necessarily have any information about software installed via other
means.

A SWIMA-PC is not required to utilize every possible source of
software information on its endpoint. Some SWIMA-PCs might be
explicitly tied only to one or a handful of software inventory
sources, or it a given SWIMA-PC could be designed to dynamically
accommodate new sources. For all software inventory evidence sources
that a particular SWIMA-PC supports, it MUST completely support all
requirements of this specification with regard to those sources. A
potential source that cannot support some set of required
functionality (e.g., it is unable to monitor the software it reports
for change events, as discussed in Section 3.6) MUST NOT be used as a
source of endpoint software inventory information, even if it could
provide some information. In other words, a source either supports
full functionality as described in this specification, specification or it cannot be
used at all. In the event that a previously used source becomes
unavailable, this would be treated as a discontinuity in the
SWIMA-PC's reporting. Section 3.7.1 describes how to use changes in
the Event Identifier (EID) Epoch value to indicate a reporting
discontinuity.

When sending information about installed software software, the SWIMA-PC MUST
include the complete set of relevant data from all supported sources
of software inventory evidence. In other words, sources need to be
used consistently. This is because, because if a particular source is
included in an initial inventory, inventory but excluded from a later inventory,
the SWIMA-PV receiving this information might reasonably conclude
that the software reported by that source was no longer installed on
the endpoint. As such, it is important that all supported sources be
used every time the SWIMA-PC provides information to a SWIMA-PV.

Note that, that if a SWIMA-PC collects data from multiple sources, it is
possible that some software products might be "double counted". This
can happen if both two or more sources of inventory evidence provide a
record for a single installation of a software product. When a
SWIMA-PC reports information or records events from multiple
inventory evidence sources, it MUST use the information those sources
provide, rather than attempting attempt to perform some form of reduction. In
other words, if multiple sources report records corresponding to a
single installation of a software product, all such records from each
source are required to be part of the SWIMA-PC's processing even if
this might lead to multiple reporting, and the SWIMA-PC is not to
ignore some records to avoid such multiple reporting.

All inventory records reported by a SWIMA-PC include a Source
Identifier linking them to a particular source. Source Identifiers
are discussed more in Section 3.4.5. As discussed in that section,
Source Identifiers can help consumers of SWIMA data identify cases of
multiple reporting.

3.2. Data Models

SWIMA conveys records about software presence from a SWIMA-PC to a
SWIMA-PV. SWIMA does not manage the actual generation or collection
of such records on the endpoint. As a result, information available
to SWIMA-PCs might come in a variety of formats, and a SWIMA-PC could
have little control over the format of the data made available to it.
Because of this, SWIMA places no constraints on the format of these
generated records and supports an open set of record formats by which
installed software instances can be described. The following terms
are used in this document:

o Data model - The format used to structure data within a given
record. SWIMA does not constrain the data models it conveys.

o Record - A populated instance of some data model that describes a
software product.

Do not confuse the "data model" described here with the structure of
the SWIMA messages and attributes used to convey information between
SWIMA-PVs and PCs. SWIMA-PCs. The SWIMA specification standard dictates the structure
of its messages and attributes. Some attributes, however, have
specific fields used to convey inventory records, and those fields
support an extensible list of data models for their values. In other
words, SWIMA data models provide an extension point within SWIMA
attributes that allows the structure of inventory records to evolve.

The data model used to structure software inventory information has
very little impact on the behavior of the components defined in this
specification. The SWIMA-PV has no dependency on the data model of
records conveyed in SWIMA messages. For this reason, it MUST NOT
reject a message or respond with a PA-TNC Error due to the data model
used to structure records in attributes it receives. Similarly, it
MUST NOT reject a message or respond with a PA-TNC Error if a record
fails to comply with a stated format, unless that failure prevents
correct parsing of the attribute itself. In short, the record bodies
are effectively treated as "black boxes" by the SWIMA-PV. (Note that
the SWIMA-PV might serve as the front-end "front end" of other functionality
that does have a dependency on the data model used to structure
software information, but any such dependency is beyond the scope of
this specification and needs to be addressed outside the behaviors
specified in this document. This specification is only concerned
with the collection and delivery of software inventory information;
components that consume and use this information are a separate
concern.)

The SWIMA-PC does have one functional dependency on the data models
used in the software records it delivers, but only insofar as it is
required to deterministically create a Software Identifier (described
in Section 3.4.1) based on each record it delivers. The SWIMA-PC
MUST be able to generate a Software Identifier for each record it
delivers, and if the SWIMA-PC cannot do so the record so, it cannot be
delivered by deliver the SWIMA-PC.
record. All SWIMA-PCs MUST at least be able to generate Software
Identifiers for the data model types specified in Section 6 of this
document. A SWIMA-PC MAY include the ability to generate Software
Identifiers for other data model types, types and thus be able to support
them as well.

3.3. Basic Attribute Exchange

In the most basic exchange supported by this specification, a SWIMA-
PV
SWIMA-PV sends a request to the SWIMA-PC SWIMA-PC, requesting some type of
information about the endpoint's software inventory. This simple
exchange is shown in Figure 2.

+-------------+ +--------------+
| SWIMA-PC | | SWIMA-PV | Time
+-------------+ +--------------+ |
| | |
|<------------SWIMA Request---------------| |
| | |
|-------------SWIMA Response------------->| |
| | V

Figure 2: Basic SWIMA Attribute Exchange

Upon receiving such a SWIMA Request from the SWIMA-PV, the SWIMA-PC
is expected to collect all the relevant software inventory
information from the endpoint's software evidence collection Software Inventory Evidence
Collection and place it within its response attribute.

SWIMA-PVs MUST discard discard, without error error, any SWIMA Response attributes
that they receive for which they do not know the SWIMA Request
parameters that led to this SWIMA Response. This is due to the fact
that the SWIMA Request includes parameters that control the nature of
the response (as will be described in the following sections) and sections);
without knowing those parameters parameters, the SWIMA Response cannot be
reliably interpreted. Most often receiving Each SWIMA Request includes a Request ID,
which is echoed in any SWIMA Response to that request and allows
matching of responses to requests. See Section 5.5 for more on
Request IDs. Receiving an unsolicited SWIMA Response attribute happens will
most often happen when a NEA Server has multiple SWIMA-PVs; one
SWIMA-PV sends a SWIMA Request but, Request, but unless exclusive delivery
[RFC5793] is set by the sender and honored by the recipient, both multiple
SWIMA-PVs will receive copies of the resulting SWIMA Response. In
this case, the SWIMA-PV that didn't send the SWIMA Request would lack
the context necessary to correctly interpret the SWIMA Response it
received and would simply discard it. Note, however, that
proprietary measures might allow a SWIMA-PV to discover the SWIMA
Request parameters for a SWIMA Response even if that SWIMA-PV did not
send the given SWIMA Request. As such, there is no blanket
requirement for a SWIMA-PV to discard all SWIMA Responses to SWIMA Request
Requests that the SWIMA-PV did not generate itself, itself -- only that
SWIMA-PVs are required to discard SWIMA Responses for which they
cannot get the necessary context to interpret.

In the case that it is possible to do so, the SWIMA-PC SHOULD send
its SWIMA Response attribute to the SWIMA-PV that requested it it, using
exclusive delivery as described in section Section 4.5 of RFC 5793 (PB-TNC) "PB-TNC: A Posture
Broker (PB) Protocol Compatible with Trusted Network Connect (TNC)"
[RFC5793]. Exclusive delivery requests that only the sender of the
SWIMA Request receives be the receiver of the resulting SWIMA Response. Note,
however, that PB-TNC does not require the recipient to honor the
exclusive delivery flag in messages that it receives, so setting the
flag cannot be guaranteed to prevent a SWIMA-PV from receiving
unsolicited SWIMA Responses.

Note that, in the case that a single endpoint hosts multiple
SWIMA-PCs, a single SWIMA Request could result in multiple SWIMA
Responses. SWIMA-PVs need to handle such an occurrence without
error.

All numeric values sent in SWIMA messages are sent in network
(big endian) byte order.

3.4. Core Software Reporting Software-Reporting Information

Different parameters in the SWIMA Request can influence what
information is returned in the SWIMA Response. However, while each
SWIMA Response provides different additional information about this
installed software, they the responses all share a common set of fields
that support reliable software identification on an endpoint. These
fields include: include Software Identifiers, the Data Model Type, Record
Identifiers, Software Locators, and Source Identifiers. These fields
are present for each reported piece of software in each type of SWIMA
Response. The following sections examine these information types in
more detail.

3.4.1. Software Identifiers

A Software Identifier uniquely identifies a specific version of a
specific software product. The SWIMA specification standard does not dictate the
structure of a Software Identifier (beyond stating that it is a
string) or define how it is created. Instead, each data model
described in the Software "Software Data Model IANA table Types" registry (Section 10.4) 10.5)
includes its own rules for how a Software Identifier is created based
on a record in the Endpoint's endpoint's Software Inventory Evidence Collection
expressed in that data model. Other data models will have their own
procedures for the creation of associated Software Identifiers.
Within the SWIMA specification, SWIMA, the Software Identifier is simply an opaque string string, and
there is never any need to unpack any information that might be part
of that identifier.

A Software Identifier is a fraction of the size of the inventory
record from which it is derived. For this reason, it is often more
efficient to collect full inventories using Software Identifiers and
only collect full records when necessary using targeted requests.
For some combinations of data models and sources, the full record
might never be necessary necessary, as the identifier can be directly
correlated to the contents of the full record. This is possible with
authoritative SWID tags, since these tags always have the same
contents and thus a Software Identifier derived from these tags can
be used as a lookup to a local copy of the full tag. For other
combinations of source and data model, a server might not be able to
determine the specific software product and version associated with
the identifier without requesting the delivery of the full record.
However, even in those cases, downstream consumers of this
information might never need the full record as long as the Software
Identifiers they receive can be tracked reliably. A SWIMA-PV can use
Software Identifiers to track the presence of specific software
products on an endpoint over time in a bandwidth-efficient manner.

There are two important limitations of Software Identifiers to keep
in mind:

1. The identifiers do not necessarily change when the associated
record changes. In some situations, a record in the endpoint's
Software Inventory Evidence Collection will change due to new
information becoming available or in order to correct prior
errors in that information. Such changes might or might not
result in changes to the Software Identifier, depending on the
nature of the changes and the rules governing how Software
Identifiers are derived from records of the appropriate data
model.

2. It is possible that a single software product is installed on a
single endpoint multiple times. If both of these multiple installation
instances are reported by the same source using the same data
format, then this can result in identical Software Identifiers
for each both installation instances. In other words, Software
Identifiers might not uniquely identify installation instances;
they just are just intended to uniquely identify software products
(which might have more than one installation instance). Instead,
to reliably distinguish between multiple instances of a single
software product, one needs to make use of Record Identifiers, Identifiers as
described in Section 3.4.3.

3.4.2. Data Model Type

The Data Model Type consists of two fields: the Data Model Type PEN and the
Data Model Type. ("PEN" stands for "Private Enterprise Number".)
The combination of these fields is used to identify the type of data
model of the associated software inventory record. The data model is
significant not only because it informs the recipient of the data
model of the associated record, record but also because the process for generation of
generating the Software Identifier for the record depends on the
record's data model. Clearly identifying the type of data model from
which the Software Identifier was derived thus provides useful
context for that value.

The PEN (or Private Enterprise Number) identifies the organization that assigns meaning to the Data
Model Type field value. PENs are managed by IANA in the Private "Private
Enterprise Numbers Numbers" registry. PENs allow vendors to designate their
own set of data models for software inventory description. IANA
reserves the PEN of 0x000000. Data Model Types associated with this
PEN are defined in the Software "Software Data Model IANA table, created in Types" registry; see
Section 10.4 10.5 of this specification. Note that this IANA table
reserves all values greater than or equal to 0xC0 (192) for local
enterprise use. This means that local enterprises can use custom
data formats and indicate them with the IANA PEN and a Data Model
Type value between 0xC0 and 0XFF, 0xFF, inclusive. Those enterprises are
responsible for configuring their SWIMA-PCs to correctly report those
custom data models.

3.4.3. Record Identifiers

A Record Identifier is a 4-byte unsigned integer that is generated by
the SWIMA-PC that and is uniquely associated with a specific record within
the Endpoint's endpoint's Software Inventory Evidence Collection. The SWIMA-PC
MUST assign a unique identifier to each record when it is added to
the Endpoint's endpoint's Software Inventory Evidence Collection. The Record
Identifier SHOULD remain unchanged if that record is modified.
(However,
However, it is recognized that, in some circumstances, record
modification might be hard to distinguish from record deletion
followed by creation of a new record. For this reason, retaining a
constant Record Identifier across a record modification is
recommended but not required.) required. Similarly, in the case that the
software product associated with a record is moved, ideally the
Record Identifier for the record of the moved software will remain
unchanged, reflecting that it represents the same software product
instance, albeit in a new location. However, this level of tracking
could prove difficult to achieve and is not required. The SWIMA-PC
might wish to assign Record Identifiers sequentially, but any scheme
is acceptable acceptable, provided that no two records receive the same
identifier.

Servers can use Record Identifiers to distinguish between multiple
instances of a single software product installed on an endpoint.
Since each installation instance of a software product is associated
with a separate record, servers can use the record identifier Record Identifier to
distinguish between instances. For example, if an event is reported
(as described in Section 3.7), the record identifier Record Identifier will allow the
server to discern which instance of a software product is involved.

3.4.4. Software Locators

In addition to the need to identify what software products, many products are on an
endpoint, some processes that use cases
of inventory information also need to
know where software is located on the endpoint. This information
might be needed to direct remediation actions or similar processes.
For this reason, every reported software product also includes a
Software Locator to identify where the software is installed on the
endpoint.

If the location is not provided directly by the record source data source, the
SWIMA-PC is responsible for attempting to determine the location of
the software product. The "location" of a product SHOULD be the
directory in which the software products' product's executables are kept. The
source and/or
SWIMA-PC MUST be consistent in reporting the location of a software product (i.e.,
product. In other words, assuming that a software product has not
moved, the SWIMA-PC cannot use one location in one report and a
different location for the same software product in another). another. (If a
software product has moved, the Software Locator needs to reflect the
new location.)

The location is expressed as a URI string. The string MUST conform
to URI syntax requirements. [RFC3986] requirements [RFC3986]. The URI schema scheme describes the
context of the described location. For example, in most cases the
location of the installed software product will be expressed in terms
of its path in the filesystem. For such locations, the location URI
scheme MUST be "file" "file", and the URI MUST conform to the "file" URI
scheme standard [RFC8089] [RFC8089], including the percent-encoding of
whitespace and other special characters. It is possible that other
schemes could be used to represent other location contexts. Apart
from specifying the use of the "file" scheme, this specification does
not identify other schemes or define their use. When representing
software products in other location contexts, tools MUST be
consistent in their use of schemes, but the exact schemes are not
normatively defined here. SWIMA implementations are not limited to
the IANA list of URI schemes [1] <https://www.iana.org/assignments/
uri-schemes/> and can define new schemes to support other types of
application locations.

It is possible, possible that a SWIMA-PC is unable to determine the location of
a reported software product. In this case, the SWIMA-PC MUST provide
a zero-length Software Locator.

3.4.5. Source Identifiers

All SWIMA-PCs MUST track the source of each piece of software
information they report. Each time a SWIMA-PC gets information to
send to a given SWIMA-PV from a new source (from the perspective of
that SWIMA-PV), the SWIMA-PC MUST assign that source a Source
Identification Number,
Identifier, which is an 8-bit unsigned integer. Each item reported
includes the number of the Source Identification Number Identifier for the source that
provided that information. All information that is provided by that source,
source MUST be delivered with this same Source Identification Number. Identifier. This MUST
be done for each source used. If the SWIMA-PC ever is ever unclear as to
whether a given source is new or not, it MUST assume that this is a
new source and assign it a new Source Identification Number. Identifier. Source
Identification Numbers Identifier
numbers do not need to be assigned sequentially. SWIMA does not
support the presence of more than 256 sources sources, as the chance that a
single endpoint will have more than 256 methods of collecting
inventory information is vanishingly small. All possible values
between 0 and 255 are valid; there are no reserved Source
Identification Numbers Identifier
numbers.

Source Identification Numbers Identifiers can help with (although will not completely
eliminate) the challenges posed by multiple reporting of a single
software instance: since a single source would only report an
instance or event once, if instance. If multiple reports sources each report the same type of
software product once, there is most likely a similar instance
come from multiple sources, this might be an single instance of multiple
reporting (although it still might not be so). that
product installed on the endpoint, which each source has detected
independently. On the other hand, if multiple instances are reported
by a single source, this almost certainly means that there are
actually multiple instances that are being legitimately reported.

The SWIMA-PC is responsible for tracking associations between Source
Identifiers and the given data source. This association MUST remain
consistent with regard to a given SWIMA-PV while there is an active
PB-TNC session with that SWIMA-PV. The SWIMA-PC MAY have a different
Source Identifier association for different SWIMA-PVs. Likewise, the
SWIMA-PC MAY change the Source Identifier association for a given
SWIMA-PV if the PB-TNC session terminates. However, implementers of
SWIMA-PCs will probably find it easier to manage associations by
maintaining the same association for all SWIMA-PVs and across
multiple sessions.

Of special note, events event records reported from the SWIMA-PC's event log
(discussed in Section 3.7) also need to be sent with their associated
data source. The Source Identifier reported with events MUST be the
current (i.e., at the time the event is sent) Source Identifier
associated with the data source that produced the event, regardless
of how long ago that event occurred. Event logs are likely to
persist far longer than a single PB-TNC session. SWIMA-PCs MUST
ensure that each event can be linked to the appropriate data source,
even if the Source Identifiers used when the event was created have
since been reassigned. In other words, when sending an event, it
needs to be sent with the Source Identifier currently linked to the
data source that produced it, regardless of whether a different
Source Identifier would have been associated with the event when the
event was first created.

Note that the Source Identification Number Identifier is primarily used to support
recognition, rather than identification, of sources. That is to say,
a Software Identification Number Source Identifier can tell a recipient that two events were
reported by the same source, but the number will not necessarily help
that recipient determine which source was used. Moreover, different
SWIMA-PCs will not necessarily use the same Source
Identification Numbers Identifiers for
the same sources. SWIMA-PCs MUST track the assignment of Source Identification Numbers
Identifiers to ensure consistent application thereof. SWIMA-PCs MUST
also track which Source
Identification Numbers Identifiers have been used with each SWIMA-PV
with which they communicate.

3.4.6. Using Software and Record Identifiers in SWIMA Attributes

A SWIMA Attribute attribute reporting an endpoint's Software Inventory Evidence
Collection always contains the Software Identifiers associated with
the identified software products. A SWIMA Attribute attribute might or might
not also contain copies of software inventory evidence records. Software Inventory Evidence Records. The
attribute exchange is identical to the diagram shown in Figure 2 2,
regardless of whether software inventory evidence records Software Inventory Evidence Records are
included. The SWIMA Request attribute indicates whether the response
is required to include software inventory evidence records. Software Inventory Evidence Records.
Excluding software inventory evidence records Software Inventory Evidence Records can reduce the
attribute size of the response by multiple orders of magnitude when
compared to sending the same inventory with full records.

3.5. Targeted Requests

Sometimes a SWIMA-PV does not require information about every piece
of software on an endpoint but only needs to receive updates about
certain software instances. For example, enterprise endpoints might
be required to have certain software products installed and to keep
these updated. Instead of requesting a complete inventory just to
see if these products are present, the SWIMA-PV can make a "targeted
request" for the software in question.

Targeted requests follow the same attribute exchange as the exchange
described in Figure 2. The SWIMA-PV targets its request by providing
one or more Software Identifiers in its SWIMA Request attribute. The
SWIMA-PC MUST then limit its response to contain only records that
match the indicated Software Identifier(s). This allows the network
exchange to exclude information that is not relevant to a given
policy question, thus reducing unnecessary bandwidth consumption.
The SWIMA-PC's response might or might not include software inventory
evidence records, Software Inventory
Evidence Records, depending on the parameters of the SWIMA Request.

Note that targeted requests identify the software relevant to the
request only through Software Identifiers. This specification does
not support arbitrary, parameterized querying of records. For
example, one cannot request all records from a certain software
publisher,
publisher or all records created by a particular record data source.
Targeted requests only allow a requestor requester to request specific software
(as identified by their Software Identifiers) and receive a response
that is limited to the named software.

There is no assumption that a SWIMA-PC will recognize "synonymous
records" - -- that is, records from different sources for the same
software. Recall that different sources and data models may use
different Software Identifier strings for the same software product.
The SWIMA-PC returns only records that match the Software Identifiers
in the SWIMA Request, even if there might be other records in the
endpoint's Software Inventory Evidence Collection for the same
software product. This is necessary because SWIMA-PCs might not have
the ability to determine that two Software Identifiers refer to the
same product.

Targeted requests do

A targeted SWIMA Request attribute does not include specify Record
Identifiers or Software Locators. The response to a targeted request
MUST include all records associated with the named Software
Identifiers, including the case where there are multiple records
associated with a single Software Identifier.

SWIMA-PCs MUST accept targeted requests and process them correctly as
described above. SWIMA-PVs MUST be capable of making targeted
requests and processing the responses thereto.

3.6. Monitoring Changes in an Endpoint's Software Inventory Evidence
Collection

The software collection on an endpoint is not static. As software is
installed, uninstalled, patched, or updated, the Software Inventory
Evidence Collection is expected to change to reflect the new software
state on the endpoint. Different record data sources might update the
evidence collection at different rates. For example, a package
manager might update its records in the Software Inventory Evidence
Collection immediately whenever it is used to add or remove a
software product. By contrast, sources that perform periodic
examination of the endpoint would likely only update their records in
the Software Inventory Evidence Collection after each examination.

All SWIMA-PCs MUST be able to be able to detect changes to the Software
Inventory Evidence Collection. Specifically, SWIMA-PCs MUST be able
to detect:

o The creation of records

o The deletion of records

o The alteration of records

An "alteration" is anything that modifies the contents of a record
(or would modify it, if the record is dynamically generated on
demand) in any way, regardless of whether the change is functionally
meaningful.

SWIMA-PCs MUST detect such changes to the endpoint's Software
Inventory Evidence Collection in close to real-time real time (i.e., within
seconds) when the Posture Collector SWIMA-PC is operating. In addition, in the case
where there is a period during which the SWIMA-PC is not operating,
the SWIMA-PC MUST be able to determine the net change to the
endpoint's Software Inventory Evidence Collection over the period it
was not operational. Specifically, the "net change" represents the
difference between (1) the state of the endpoint's Software Inventory
Evidence Collection when the SWIMA-PC was last operational and
monitoring its state, state and (2) the state of the endpoint's software
inventory evidence collection Software
Inventory Evidence Collection when the SWIMA-PC resumed operation.
Note that a net change might not reflect the total number of change
events over this interval. For example, if a record was altered
three times during a period when the SWIMA-PC was unable to monitor
for changes, the net change of this interval might only note that
there was an alteration to the record, but not how many individual
alteration events occurred. It is sufficient for a SWIMA-PC's
determination of a net change to note that there was a difference
between the earlier and current state state, rather than enumerating to enumerate all
the individual events that allowed the current state to be reached.

The SWIMA-PC MUST assign a time to each detected change in the
endpoint's Software Inventory Evidence Collection. These timestamps
correspond to the SWIMA-PC's best understanding as to when the
detected change occurred. For changes to the endpoint's Software
Inventory Evidence Collection that occur while the SWIMA-PC is
operating, the SWIMA-PC ought to be able to assign a time to the
event that is accurate to within a few seconds. For changes to the
endpoint's Software Inventory Evidence Collection that occur while
the SWIMA-PC is not operational, upon becoming operational the SWIMA-
PC
SWIMA-PC needs to make a best guess as to the time of the relevant
events (possibly by looking at timestamps on files), but these values
might be off. In the case of dynamically generated records, the time
of change is the time at which the data from which the records are
generate
generated changes, not the time at which a changed record is
generated. For example, if records are dynamically generated based
on data in an RPM database, database (<http://rpm.org/>), the time of change
would be when the RPM database changed.

With regard to deletions of records, the SWIMA-PC needs to detect the
deletion of a given record and MUST retain a copy of the full deleted
record along with the associated Record Identifier and Software
Locator so that the record and associated information can be provided
to the SWIMA-PV upon request. This copy of the record MUST be
retained for a reasonable amount of time. Vendors and administrators
determine what "reasonable" means, but a copy of the record SHOULD be
retained for as long as the event recording the deletion of the
record remains in the SWIMA-PC's event log (as described in
Section 3.7). This is
recommended because, recommended, because as long as the event is
in the SWIMA-PC's change
logs, event log the SWIMA-PC might send an a change event
attribute (described in Section 3.7) that references this record, and
a copy of the record is needed if the SWIMA-PV wants a full copy of
the relevant records. record. In the case that a SWIMA-PC is called upon to
report a deletion event that is still in the event log but where the
record itself is no longer available, the SWIMA-PC will still return
an entry corresponding to the deletion event, but the field of that
entry that would normally contain the full copy of the record SHOULD
be
0-length. zero-length.

With regard to alterations to a record, SWIMA-PCs MUST detect any
alterations to the contents of a record. Alterations need to be
detected even if they have no functional impact on the record. A
good guideline is that any alteration to a record that might change
the value of a hash taken on the record's contents needs to be
detected by the SWIMA-PC. A SWIMA-PC might be unable to distinguish
modifications to the content contents of a record from modifications to the
metadata that the file system filesystem associates with the record. For
example, a SWIMA-PC might use the "last modification" timestamp as an
indication of alteration to a given record, but a record's last
modification time can change for reasons other than modifications to
the record record's contents. A SWIMA-PC is still considered compliant with
this specification if it also reports metadata change events that do
not change the record itself as alterations to the record. In other
words, while SWIMA-PC authors implementers are encouraged to exclude
modifications that do not affect the bytes within the record,
discriminating between modifications to file contents and changes to
file metadata can be difficult and time consuming on some systems.
As such, as long as the alterations detected by a SWIMA-PC always
cover all modifications to the contents of a record, the SWIMA-PC is
considered compliant even if it also registers alterations that do
not modify the contents of a record as well. When recording an
alteration to a record, the SWIMA-PC is only required to note that an
alteration occurred. The SWIMA-PC is not required to note or record
how the record was altered, nor is it possible to include such
details in SWIMA
Attributes attributes reporting the change to a SWIMA-PV.
There is no need to retain a copy of the original record prior to the
alteration.

When a record changes changes, it SHOULD retain the same Record Identifier.
The Software Locator might or might not change, depending on whether
the software changed locations during the changes that led to the
record change. A record change MUST retain the same Software
Identifier. This means that any action that changes a software
product (e.g., application of a patch that results in a change to the
product's version) MUST NOT be reflected by a record change but
instead MUST result in the deletion of the old record and the
creation of a new record. This reflects the requirement that a
record in the endpoint's Software Inventory Evidence Collection
correspond directly with an instance of a specific software product.

3.7. Reporting Change Events

As noted in Section 3.6, SWIMA-PCs are required to detect changes to
the endpoints endpoint's Software Inventory Evidence Collection (creation,
deletion, and alteration) in near real-time real time while the SWIMA-PC is
operational, and a given SWIMA-PC MUST be able to account for any net
change to the endpoint's Software Inventory Evidence Collection that
occurs when the SWIMA-PC is not operational. However, to be of use
to the enterprise, the NEA Server needs to be able to receive these
events and be able to understand how new changes relate to earlier
changes. In SWIMA, this is facilitated by reporting change events.
All SWIMA-
PCs SWIMA-PCs MUST be capable of receiving requests for change events
and sending change event attributes. All SWIMA-PVs MUST be capable
of requesting and receiving change event attributes.

3.7.1. Event Identifiers

To be useful, change events need to be correctly ordered. Ordering The
ordering of events is facilitated by two pieces of information: an
Event Identifier (EID) value and an EID Epoch value.

An EID is a 4-byte unsigned integer that the SWIMA-PC assigns
sequentially to each observed event (whether detected in real-time real time or
deduced by looking for net changes over a period of SWIMA-PC
inactivity). All EIDs exist within the context of some "EID Epoch",
which is also represented as a 4-byte unsigned integer. EID Epochs
are used to ensure synchronization between the SWIMA-PC and any
SWIMA-PVs with which it communicates. EID Epoch values MUST be
generated in such a way as to minimize the chance that an EID Epoch
will be reused, even in the case where the SWIMA-PC reverts to an
earlier state. For this reason, sequential EID Epochs are
discouraged, since loss of state could result in value reuse. There
are multiple reasons that a SWIMA-PC might need to deliberately reset
its EID counter, including exhaustion of available EID values, the
need to purge entries from the event log to recover memory, or
corruption of the event log. In all case cases where a SWIMA-PC needs to
reset its EID counter, a new EID Epoch MUST be selected.

Within an Epoch, EIDs MUST be assigned sequentially, so that if a
particular event is assigned an EID of N, the next observed event is
given an EID of N+1. In some cases, events might occur
simultaneously, or the SWIMA-PC might not otherwise be able to
determine an ordering for events. In these cases, the SWIMA-PC
creates an arbitrary ordering of the events and assigns EIDs
according to this ordering. Two change events MUST NOT ever be
assigned the same EID within the same EID Epoch. No meaningful
comparison can be made between EID values of different Epochs.

The EID value of 0 is reserved and MUST NOT be associated with any
event. Specifically, an EID of 0 in a SWIMA Request attribute
indicates that a SWIMA-PV wants an inventory response rather than an
event response, while an EID of 0 in a SWIMA Response is used to
indicate the initial state of the endpoint's Software Inventory
Evidence Collection prior to the observation of any events. Thus Thus,
the very first recorded event in a SWIMA-PC's records within an EID
Epoch MUST be assigned a value of 1. Note that EID and EID Epoch
values are assigned by the SWIMA-PC without regard to whether events
are being reported to one or more SWIMA-PVs. The SWIMA-PC records
events and assigns EIDs during its operation. All SWIMA-PVs that
request event information from the SWIMA-PC will have those requests
served from the same event records and thus will see the same EIDs
and EID Epochs for the same events.

If a SWIMA-PC uses multiple sources, a SWIMA-PC's assignment of EIDs
MUST reflect the presence and order of all events on the endpoint (at
least for supported sources) sources), regardless of the source. This means
that if source A experiences an event, event and then source B experiences
two events, and then source A experiences another two events, the
SWIMA-PC is required to capture five events with consecutive EID
values reflecting the order in which the events occur. occurred.

The SWIMA-PC MUST ensure that there is no coverage gap (i.e., change
events that are not recorded in the SWIMA-PC's records) in its change
event records. This is necessary because a coverage gap might give a
SWIMA-PV a false impression of the endpoint's state. For example, if
a SWIMA-PV saw an event indicating that a particular record had been
added to the endpoint's software inventory evidence collection, and
saw no Software Inventory Evidence Collection but
did not see any subsequent events indicating that the record in
question had been deleted, it might reasonably assume that this
record was still present and thus that the indicated software was
still installed (assuming that the Epoch has not changed). If there
is a coverage gap in the SWIMA-PC's event records, however, this
assumption could be false. For this reason, the SWIMA-PC's event
records MUST NOT contain gaps. In the case where there are periods
where it is possible that changes occurred without the SWIMA-PC
detecting or recording them, the SWIMA-PC MUST either (1) compute a
net change and update its event records
appropriately, appropriately or (2) pick a
new EID Epoch to indicate a discontinuity with previous event
records.

Within a given Epoch, once a particular event has been assigned an
EID, this association MUST NOT be changed. That is, within an Epoch,
once an EID is assigned to an event, that EID cannot be reassigned to
a different event, and the event cannot be assigned a different EID.
When the SWIMA-PC's Epoch changes, all of these associations between
EIDs and events are cancelled, and EID values once again become free
for assignment.

3.7.2. Core Event Tracking Event-Tracking Information

Whether reporting events or full inventories inventories, it is important to know
how the reported information fits into the overall timeline of change
events. This is why all SWIMA Response attributes include fields to
place that response within the sequence of detected events.
Specifically, all SWIMA Responses include a Last EID field and an EID
Epoch field. The EID Epoch field identifies the EID Epoch in which
the SWIMA Response was sent. If the SWIMA Response is reporting
events, all reported events occurred within the named EID Epoch. The
Last EID (which is also always from the named EID Epoch) indicates
the EID of the last recorded change event at the time that the SWIMA
Response was sent. These two fields allow any response to be placed
in the context of the complete set of detected change events within a
given EID Epoch.

3.7.3. Updating Inventory Knowledge Based on Events

Modern endpoints can have hundreds of software products installed,
most of which are unlikely to change from one day to the next. As
such, instead of exchanging a complete list of an endpoint's
inventory on a regular basis, one might wish to only identify changes
since some earlier known state of this inventory. This is readily
facilitated by the use of EIDs to place change events in a context
relative to the earlier state.

As noted above, every SWIMA Response sent by a SWIMA-PC to a SWIMA-PV
(as described in Section Sections 3.3 through Section 3.5) includes the EID Epoch and
EID of the last event recorded prior to that response being compiled.
This allows the SWIMA-PV to place all subsequently received event
records in context relative to this SWIMA Response attribute (since
the EIDs represent a total ordering of all changes to the endpoint's software inventory evidence collection).
Software Inventory Evidence Collection). Specifically, a SWIMA-PV
(or, more likely, a database that collects and records its findings)
can record an endpoint's full inventory and also the EID and Epoch of
the most recent event reflected at the time of that inventory. From
that point on, if change events are observed, the attribute
describing these events indicates the nature of the change, the
affected records, and the order in which these events occurred (as
indicated by the sequential EIDs). Using this information, any
remote record of the endpoint's Software Inventory Evidence
Collection can be updated appropriately.

3.7.4. Using Event Records in SWIMA Attributes

A SWIMA-PV MUST be able to request a list of event records instead of
an inventory. The attribute flow in such an exchange looks the same
as the basic flow shown in Figure 2. The only difference is that, that in
the SWIMA Request attribute, attribute the SWIMA-PV provides an EID other than
0. (A (An EID value of 0 in these fields a SWIMA Request represents a request for an
inventory.) When the SWIMA-PC receives such a request, instead of
identifying records from the endpoint's Software Inventory Evidence
Collection, it consults its list of detected changes. The SWIMA-PC
MUST add an event record to the SWIMA Response attribute for each
recorded change event with an EID greater than or equal to the EID in
the SWIMA Request attribute (although the targeting of requests, as
described in the next paragraph, might limit this list). A list of
event records MUST only contain events with EIDs that all come from
the current Epoch.

SWIMA-PVs can target requests for event records by including one or
more Software Identifiers, as described in Section 3.5, in the SWIMA
Request that requests an event record list. A targeted request for
event records is used to indicate that only events affecting software
that matches one of the provided Software Identifiers are to be
returned. Specifically, in response to a targeted request for event
records, the SWIMA-PC MUST exclude any event records that are less
than the indicated EID (within the current EID Epoch) and exclude any
event records where the affected software does not match one of the
provided Software Identifiers. This might mean that the resulting
list of event records sent in the response attribute does not provide
a continuous sequence of EIDs. Both SWIMA-PCs and SWIMA-PVs MUST
support targeted request requests for event records.

3.7.5. Partial and Complete Lists of Event Records in SWIMA Attributes

Over time, a SWIMA-PC might record a large number of change events.
If a SWIMA-PV requests all change events covering a large long period of
time, the resulting SWIMA Response attribute might be extremely
large, especially if the SWIMA-PV requests the inclusion of software
inventory evidence records Software
Inventory Evidence Records in the response. In the case that the
resulting attribute is too large to send (either because (because it exceeds either
(1) the 4GB 4 GB attribute size limit imposed by the PA-TNC specification, specification
or
because it exceeds (2) some smaller size limit imposed on the SWIMA-PC) SWIMA-PC), the SWIMA-PC
MAY send a partial list of event records back to the SWIMA-PV.

Generation

The generation of a partial list of events in a SWIMA Response
attribute requires the SWIMA-PC to identify a "consulted range" of
EIDs. A consulted range is the set of event records that are
examined for inclusion in the SWIMA Response attribute and that are
included in that attribute if applicable. Recall that, that if a SWIMA
Request is targeted, only event records that involve the indicated
software would be applicable. (See Section 3.5 for more on Targeted Request.) targeted
requests.) If a request is not targeted, all event records in the considered
consulted range are applicable and are included in the SWIMA Response
attribute.

The lower bound of the consulted range MUST be the EID provided in
the SWIMA Request. (Recall that a SWIMA Request SWIMA-PV indicates a request for
event records by providing a non-0 non-zero EID value in the SWIMA Request.
See Section 3.7.4.) The upper bound of the consulted range is the
EID of the latest event record (as ordered by EID values) that is
included in the SWIMA Response attribute if it is applicable to the
request. The EID of this last event record is called the "Last
Consulted EID". The SWIMA-PC chooses this Last Consulted EID based
on the size of the event record list it is willing to provide to the
SWIMA-PV.

A partial result list MUST include all applicable event records
within the consulted range. This means that for any applicable event
record (i.e., any event record in an un-targeted request, a non-targeted request or any event
record associated with software matching a requested Software
Identifier in a targeted request) whose EID is greater than or equal
to the EID provided in the SWIMA Request and whose EID is less than
or equal to the Last Consulted EID, that event record MUST be
included in the SWIMA Response conveying this partial list of event
records. This ensures that every partial list of event records is
always complete within its indicated range. Remember that, that for
targeted requests, "complete" doesn't mean that all EIDs between the
range endpoints are present, but present -- only that every matching EID between
the range endpoints is included.

All SWIMA Response attributes that convey event records include a
Last Consulted EID field. This is in

In addition to the EID Epoch and Last EID fields that are present in
all SWIMA Responses. Responses, all SWIMA Response attributes that convey event
records include a Last Consulted EID field. Note that, that if responding
to a targeted SWIMA Request, the SWIMA Response attribute might not
contain the event record whose EID matches the Last Consulted EID
value. For example, the last consulted EID that record might have been deemed inapplicable
because it did not match the specified list of Software Identifiers
in the SWIMA Request.

If a SWIMA-PV receives a SWIMA Response attribute where the Last EID
and Last Consulted EID fields are identical, the SWIMA-PV knows that
it has received a result list that is complete, given the parameters
of the request, up to the present time.

On the other hand, if the Last EID is greater than the Last Consulted
EID, the SWIMA-PV has received a partial result list. (The Last
Consulted EID MUST NOT exceed the Last EID.) In this case, if the
SWIMA-PV wishes to try to collect the rest of the partially delivered
result list list, it then sends a new SWIMA Request whose EID is one
greater than the Last Consulted EID in the preceding response. Doing
this causes the SWIMA-PC to generate another SWIMA Response attribute
containing event records where the earliest reported event record is
the one immediately after the event record with the Last Consulted
EID (since EIDs are assigned sequentially). By repeating this
process until it receives a SWIMA Response where the Last EID and
Last Consulted EID are equal, the SWIMA-PV is able to collect all
event records over a given range, even if the complete set of event
records would be too large to deliver via a single attribute.

Implementers need to be aware that a SWIMA Request might specify an
EID that is greater than the EID of the last event recorded by a
SWIMA-PC. In accordance with the behaviors described in
Section 3.7.4, a SWIMA-PC MUST respond to such a request with a SWIMA
Response attribute that contains zero event records. This is because
the SWIMA-PC has recorded no event records with EIDs greater than or
equal to the EID in the SWIMA Request. In such a case, the Last
Consulted EID field MUST be set to the same value as the Last EID
field in this SWIMA Response attribute. This case is called out
because the consulted range on a SWIMA-PC in such a situation is a
negative range, where the "first" EID in the range (provided in the
SWIMA Request) is greater than the "last" EID in the range (this
being the EID of the last recorded event on the SWIMA-PC).
Implementers need to ensure that SWIMA-PCs do not experience problems
in such a circumstance.

Note that this specification only supports the returning of partial
results when returning event records. There is no way to return a
partial inventory list under this specification.

3.7.6. Synchronizing Event Identifiers and Epochs

Since EIDs are sequential within an Epoch, if a SWIMA-PV's list of
event records contains gaps in the EID values within a single Epoch,
the SWIMA-PV knows that there are events that have it has not been accounted
for. The SWIMA-PV can either request either (1) a new event list to collect
the missing events or request (2) a full inventory to re-sync resync its
understanding of the state of the endpoint's Software Inventory
Evidence Collection. In either case, after the SWIMA-PV's record of
the endpoint's Software Inventory Evidence Collection has been
updated, the SWIMA-PV can record the new latest EID value and track
events normally from that point on.

If the SWIMA-PV receives any attribute from a SWIMA-PC where the EID
Epoch differs from the EID Epoch that was used previously, then the
SWIMA-PV or any entity using this information to track the endpoint's
Software Inventory Evidence Collection knows that there is a
discontinuity in their its understanding of the endpoint's state. To move
past this discontinuity and reestablish a current understanding of
the state of the endpoint's Software Inventory Evidence Collection,
the SWIMA-PV needs to receive a full inventory from the endpoint.
The SWIMA-PV cannot be brought in sync with the endpoint's state
through the collection of any set of event records in this situation.
This is because it is not possible to account for all events on the
SWIMA-PC since the previous Epoch was used, because used: there is no way to query
for EIDs from a previous Epoch. Once the SWIMA-PV has received a
full inventory for the new Epoch, the SWIMA-
PV SWIMA-PV records the latest EID
reported in this new Epoch and can track further events normally.

A SWIMA-PC MUST NOT report events with EIDs from any Epoch other than
the current EID Epoch. The SWIMA-PC MAY choose to purge all event
records from a previous Epoch from memory after an Epoch change.
Alternately, the SWIMA-PC MAY choose to retain some event records
from a previous EID Epoch and assign them new EIDs in the current
Epoch. However, in the case where a SWIMA-PC chooses the latter
option it MUST ensure that the order of events according to their
EIDs is unchanged and that there is no coverage gap between the first
retained event recorded during the previous Epoch (now reassigned
with an EID in the current Epoch) and the first event recorded during
the current Epoch. In particular, the SWIMA-PC MUST ensure that all
change events that occurred after the last recorded event from the
previous Epoch are known and recorded. (This might not be possible
if the Epoch change is due to state corruption on the SWIMA-PC.) A
SWIMA-PC might choose to reassign EIDs to records from a preceding
Epoch to create a "sliding window" of events, where each Epoch change
represents a shift in the window of available events.

In the case where a SWIMA-PC suffers a crash and loses track of its
current EID Epoch or current EID, then it MUST generate a new EID
Epoch value and begin assigning EIDs within that Epoch. In this
case, the SWIMA-PC MUST purge all event records from before the crash
crash, as it cannot ensure that there is not a gap between the last
of those records and the next detected event. The process for
generating a new EID Epoch MUST minimize the possibility that the
newly generated EID Epoch is the same as a previously used EID Epoch.

The SWIMA-PV will normally never receive an attribute indicating that
the latest EID is less than the latest EID reported in a previous
attribute within the same EID Epoch. If this occurs, the SWIMA-PC
has suffered an error of some kind, possibly indicative of at least
partial corruption of its event log. In this case, the SWIMA-PV MUST
treat the situation as if there was a change in Epoch and treat any
local copy of the endpoint's Software Inventory Evidence Collection
as out-of-sync being out of sync until a full inventory can be reported by the SWIMA-
PC. In this case, the
SWIMA-PC. The SWIMA-PV SHOULD log the occurrence so the SWIMA-PC can
be examined to ensure that it is now operating properly.

3.8. Subscriptions

Thus far, all attribute exchanges discussed assume that a SWIMA-PV
sent an a SWIMA Request attribute and the SWIMA-PC is providing a direct
response to that request. The SWIMA specification also supports the ability for of a
SWIMA-PC to send a SWIMA Response to the SWIMA-PV in response to
observed changes in the endpoint's software
inventory evidence collection, Software Inventory Evidence
Collection, instead of in direct response to a SWIMA Request. An
agreement by a SWIMA-PC to send content when certain changes are detected to the
endpoint's Software Inventory Evidence Collection are detected is
referred to in this specification as a "subscription", and the
SWIMA-PV that receives this content is said to be "subscribed to" the
given SWIMA-PC. All SWIMA-PCs and SWIMA-
PVs SWIMA-PVs MUST support the use of
subscriptions.

3.8.1. Establishing Subscriptions

A SWIMA-PV establishes a subscription on a particular SWIMA-PC by
sending a SWIMA Request attribute with the Subscription Subscribe flag set. The
SWIMA Request attribute is otherwise identical to the SWIMA Requests
discussed in previous sections. Specifically, such a SWIMA Request
might or might not request the inclusion of software inventory
evidence records, Software Inventory
Evidence Records, might or might not be targeted, and might request
change event records or endpoint inventory. Assuming that no error
is encountered, a SWIMA-PC MUST send a SWIMA Response attribute in
direct response to this SWIMA Request attribute, just as if the
Subscription
Subscribe flag was not set. As such, the attribute exchange that
establishes a new subscription in a SWIMA-PC has the same flow as the
flow seen in the previous attribute exchanges, as depicted in
Figure 2. If the SWIMA-PV does not receive a PA-TNC Error attribute
(as described in
Section Sections 3.9 and Section 5.16) 5.15) in response to their its
subscription request, the subscription has been successfully
established on the SWIMA-PC. The SWIMA Request attribute that
establishes a new subscription is referred to as the "establishing
request" for that subscription.

When a subscription is established established, it is assigned a Subscription ID
value. The Subscription ID is equal to the value of the Request ID
of the establishing request. (For more about Request IDs, see
Section 5.6.) 5.5.)

A SWIMA-PC MUST have the ability to record and support at least 8
simultaneous subscriptions and SHOULD have the ability to support
more than this. These subscriptions might all come from a single
SWIMA-PV, might all be from different SWIMA-PVs, SWIMA-PVs (residing on the same
or different NEA Servers), or might be a mix. In the case that a
SWIMA-PC receives a subscription request but is unable to support an
additional subscription, it MUST respond to the request with a PA-TNC
Error attribute of type with error code SWIMA_SUBSCRIPTION_DENIED_ERROR.

A SWIMA-PV MUST have the ability to record and support at least 256
simultaneous subscriptions and SHOULD have the ability to support
more than this. Any number of these subscriptions might be to the
same SWIMA-PC SWIMA-PC, and any number of these subscriptions might be to
different SWIMA-PCs.

3.8.2. Managing Subscriptions

The SWIMA-PC MUST record each accepted subscription along with
different SWIMA-PCs. In the latter case, some of these SWIMA-PCs
might share a single endpoint, while others might be on different
endpoints.

3.8.2. Managing Subscriptions

The SWIMA-PC MUST record each accepted subscription along with the
identity of the party to whom attributes are to be pushed. This
identity includes two parts:

o An identifier for the PB-TNC session between the Posture Broker
Server on a NEA Server and the Posture Broker Client on the
endpoint. This identifier is called the "Connection ID"

o The Posture Validator Identifier for the SWIMA-PV that made the
subscription request

The Posture Validator Identifier is provided in the field of the same
name in the PB-PA message that encapsulates the subscription request
attribute (Section 4.5 of [RFC5793]), and this information is passed
along to NEA Posture Collectors (Section 3.3 of [RFC5792]). The
Connection ID is a value local to a particular endpoint's Posture
Broker Client that identifies an ongoing session between a specific
Posture Broker Client and a specific Posture Broker Server. Posture
Broker Clients and Posture Broker Servers need to be capable of
supporting multiple simultaneous sessions, so they already need a way
to locally distinguish each ongoing session. (See Section 3.1 of
[RFC5793].) A Posture Broker Client needs to assign each session at
a given time its own Connection ID that lasts for the life of that
session. Connection IDs only need to be unique among the Connection
IDs of simultaneously occurring sessions on that endpoint. This
Connection ID needs to be exposed to the
identity of SWIMA-PC, and the party to whom attributes are SWIMA-PC
needs to be pushed in
compliance with the subscription. This identity includes both informed when the
NEA Server's connection Connection ID and the Posture Validator Identifier from is unbound due to the PB-PA message
closure of that delivered the request. connection.

Likewise, SWIMA-PVs MUST record each accepted subscription for which
they are the subscribing party party, including the parameters of the
establishing request, along with the associated Subscription ID and
the identity of the SWIMA-PC that will be fulfilling the
subscription. The SWIMA-PV needs to retain this information in order
to correctly interpret pushed SWIMA Response attributes sent in
fulfillment of the subscription. The identity of the SWIMA-PC is
given in the Posture Collector Identifier [RFC5793] of the PB-PA
message header in all messages from that SWIMA-PC. The SWIMA-PV has
no need to record the associated connection ID of the subscription as
the SWIMA-PV is only receiving, not sending, attributes once a
subscription is established.

3.8.3. Terminating Subscriptions

Subscriptions MAY be terminated at any time by the subscribing SWIMA-
PV
SWIMA-PV by setting the Clear Subscriptions flag in a SWIMA Request.
(See Section 5.7 5.6 for more on using this flag.) In the case that a
SWIMA Request with the Clear Subscriptions flag set is received received, the SWIMA-
PC
SWIMA-PC MUST only clear subscriptions that match both the NEA server
connection
Server's Connection ID and the SWIMA-PV ID SWIMA-PV's Posture Validator
Identifier for this SWIMA Request, Request and MUST clear all such
subscriptions.

This specification does not give the SWIMA-PV the ability to
terminate subscriptions individually - -- all subscriptions to the
SWIMA-PV are cleared when the Clear Subscriptions flag is set.

This specification does not give the SWIMA-PC the ability to
unilaterally terminate a subscription. However, if the SWIMA-PC
experiences a fatal error while fulfilling a subscription, resulting
in sending a PA-TNC Error attribute of type with error code
SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR, then the subscription whose
fulfillment led to the error MUST be treated as terminated by both
the SWIMA-PC and the SWIMA-PV. Only the subscription experiencing
the error is cancelled and cancelled; other subscriptions are unaffected. See
Section 3.9 for more on this error condition.

Finally, a subscription is terminated if the connection between the
SWIMA-PC and SWIMA-PV is deleted. closed. This occurs when the connection Connection ID
used in the messages between the SWIMA-PC and the SWIMA-PV becomes
unbound. Loss of this connection Connection ID would prevent the SWIMA-PC from
sending messages in fulfillment of this subscription. As such, loss
of the connection Connection ID necessarily forces subscription termination
between the affected parties.

3.8.4. Subscription Status

A SWIMA-PV can request that a SWIMA-PC report the list of active
subscriptions for which the SWIMA-PV is the subscriber. A SWIMA-PV
can use this capability to recover lost information about active
subscriptions. A SWIMA-PV can also use this capability to verify
that a SWIMA-PC has not forgotten any of its subscriptions. The
latter is especially useful in cases where a SWIMA-PC does not send
any attributes in fulfillment of a given subscription for a long
period of time. The SWIMA-PV can check the list of active
subscriptions on the SWIMA-PC and verify whether the inactivity is
due to (1) a lack of reportable events or due
to (2) the SWIMA-PC forgetting
its obligations to fulfill a given subscription.

A SWIMA-PV requests a list of its subscriptions on a given SWIMA-PC
by sending that SWIMA-PC a Subscription Status Request. The SWIMA-PC
MUST then respond with a Subscription Status Response (or a PA-TNC
Error if an error condition is experienced). The Subscription Status
Response MUST contain one subscription record for each of the active
subscriptions for which the SWIMA-PV is the subscribing party.

3.8.5. Fulfilling Subscriptions

As noted in Section 3.6 3.6, SWIMA-PCs are required to automatically
detect changes to an endpoint's Software Inventory Evidence
Collection in near real-time. real time. For every active subscription, the
SWIMA-PC MUST send an attribute to the subscribed SWIMA-PV whenever a
change is detected to relevant records is detected within the endpoint's Software
Inventory Evidence Collection. Such an attribute is said to be sent
"in fulfillment of" the given subscription subscription, and any such attribute
MUST include that subscription's Subscription ID. If the
establishing request for that subscription was a targeted request,
then only records that match the Software Identifiers provided in
that establishing request are considered relevant. Otherwise, Otherwise (i.e.,
for non-targeted requests) requests), any record is considered relevant for
this purpose. Figure 3 shows a sample attribute exchange where a
subscription is established and then later attributes are sent from the
SWIMA-PC in fulfillment of the established subscription.

+-------------+ +--------------+
| SWIMA-PC | | SWIMA-PV | Time
+-------------+ +--------------+ |
| | |
|<----------SWIMA Request-----------| |
| | |
|-----------SWIMA Response--------->| |
| | |
. . .
. . .
. . .
<Change Event>| | |
|----------SWIMA Response---------->| |
| | |
. . .
. . .
. . .
<Change Event>| | |
|----------SWIMA Response---------->| |
| | V

Figure 3: Subscription Establishment and Fulfillment
The contents of an attribute sent in fulfillment of a subscription
depend on the parameters provided in the establishing request for
that subscription. Specifically, the contents of an attribute sent in fulfillment
of a subscription have has the same format attribute type as would a direct
response to the establishing request. For example, if the
establishing request stipulated a response that contained an event
record list that included software inventory evidence records, Software Inventory Evidence Records, all
attributes sent in fulfillment of this subscription will also consist
of event record lists with software inventory evidence records. Software Inventory Evidence Records. As
such, all SWIMA Responses displayed in the exchange depicted in
Figure 3 have are the same format. attribute type. A SWIMA Response generated in
fulfillment of an active subscription MUST be a valid SWIMA Response
attribute according to all the rules outlined in the preceding
sections. In other words, an attribute constructed in fulfillment of
a subscription will look the same as an attribute sent in direct
response to an explicit request from a SWIMA-PV that had the same
request parameters and which that arrived immediately after the given
change event. There are a few special rules that expand on this
guideline:
guideline, as discussed in Sections 3.8.5.1 through 3.8.5.5.

3.8.5.1. Subscriptions Reporting That Report Inventories

In the case that a SWIMA-PV subscribes to a SWIMA-PC requesting and requests an
inventory attribute whenever changes are detected (i.e., the EID in
the establishing request is 0), then the SWIMA-PC MUST send the
requested inventory whenever a relevant change is detected. (A
"relevant change" is any change for untargeted requests, non-targeted requests or a change
to an indicated record in a targeted request.) Upon detection of a
relevant change for an active subscription, the SWIMA-PC sends the
appropriate inventory information as if it had just received the
establishing request. Attributes Inventory attributes sent in fulfillment of
this subscription will probably have a large amount of redundancy, as
the same records are likely to be present in each of these SWIMA
Attributes.
attributes. The role of an inventory subscription is not to report
records just for the items that changed - -- that is the role of a
subscription that reports events (see Section 3.8.5.2). A SWIMA-PC
MUST NOT exclude a record from an attribute sent in fulfillment of an
inventory subscription simply because that record was not involved in
the triggering event (although a record might be excluded for other
reasons, such as if the subscription is targeted - targeted; see
Section 3.8.5.3).

3.8.5.2. Subscriptions Reporting That Report Events

The way in which a

A SWIMA-PV indicates that it wishes to establish a subscription
requesting event records is by providing a non-zero EID in the SWIMA
Request establishing the subscription (see Section 3.7.1). However,
when the SWIMA-PC constructs an attribute in fulfillment of the
subscription (other than the direct response to the establishing
request), it MUST only include event records for the detected
change(s) that precipitated this response attribute. In other words,
it MUST NOT send a complete list of all changes starting with the
establishing request's EID, up through the latest change, every time
a new event is detected. In effect, the EID in the establishing
request is treated as being updated every time an attribute is sent
in fulfillment of this subscription, such that a single event is not
reported twice in fulfillment of a single subscription. As such,
every SWIMA-PC MUST track the EID of the last event that triggered an
attribute for the given subscription. When the next event (or set of
events) is detected, the SWIMA-PC MUST only report events with EIDs
after the last reported event. In the case that the EID Epoch of the
SWIMA-PC changes, the SWIMA-PC MUST reset this EID tracker to 0 zero
(if the event log is completely purged) or to the new EID of the last
reported retained event (if the event log is partially purged to
create a "sliding window"). Doing this ensures that the SWIMA-PC
continues to only send events that have not been previously reported.

Note that while a subscription is active, the subscribing SWIMA-PV
MAY make other requests for event records that overlap with events
that are reported in fulfillment of a subscription. Such requests
are unaffected not affected by the presence of the subscription, nor is the
subscription affected by such requests. In other words, a given
request will get the same results back whether or not there was a
subscription. Likewise, an attribute sent in fulfillment of a
subscription will contain the same information whether or not other
requests had been received from the SWIMA-PV.

A SWIMA-PV needs to pay attention to the EID Epoch in these
attributes, as changes in the Epoch might create discontinuities in
the SWIMA-PV's understanding of the endpoint's Software Inventory
Evidence Collection state, as discussed in Section 3.7.6. In
particular, once the EID Epoch changes, a SWIMA-PV is unable to have
confidence that it has a correct understanding of the state of an
endpoint's Software Inventory Evidence Collection until after the
SWIMA-PV collects a complete inventory.

SWIMA-PCs MAY send partial lists of event records in fulfillment of a
subscription. (See Section 3.7.5 for more on partial list lists of event
records.) In the case that a SWIMA-PC sends a partial list of event
records in fulfillment of a subscription, it MUST immediately send
the next consecutive partial list, list and continue doing so until it has
sent the equivalent of the complete list of event records. In other
words, if the SWIMA-PC sends a partial list list, it does not wait for
another change event to send another SWIMA Response, but Response; rather, it
continues sending SWIMA Responses until it has sent all event records
that would have been included in a complete fulfillment of the
subscription. Note that the direct response to the establishing
request is not considered to be sent in fulfillment of a
subscription. However, in this case the SWIMA-PC MUST treat the
presence of unreported events as a triggering event for pushing
additional messages in fulfillment of the newly established
subscription. As such, the net effect is that, that if the direct response
to the establishing request (i.e., the Subscription Fulfillment flag
is unset) is partial, the SWIMA-PC will immediately follow this with
additional attributes (with the Subscription Fulfillment flag set)
until the complete set of events has been sent to the SWIMA-PV.

3.8.5.3. Targeted Subscriptions

Subscriptions MAY be targeted to only apply to records that match a
given set of Software Identifiers. In the case where changes are
detected that
affect multiple records, records are detected -- some matching the
establishing request's Software Identifiers and some not, not -- the
attribute sent in fulfillment of the subscription MUST only include
inventory or events (as appropriate) for records that match the
establishing request's Software Identifiers. The SWIMA-PC MUST NOT
include non-matching records in the attribute, even if those
non-matching records experienced change events that were co-temporal simultaneous
with change events on the matching records.

In addition, a SWIMA-PC MUST send an attribute in fulfillment of a
targeted subscription only when changes to the endpoint's Software
Inventory Evidence Collection impact one or more records matching the
subscription's establishing request's Software Identifiers. A SWIMA-
PC
SWIMA-PC MUST NOT send any attribute in fulfillment of a targeted
subscription based on detected change changes to the endpoint's Software
Inventory Evidence Collection that did not involve any of the records
targeted by that subscription.

3.8.5.4. No Subscription Consolidation

A SWIMA-PV MAY establish multiple subscriptions to a given SWIMA-PC.
If this is the case, it is possible that a single change event on the
endpoint might require fulfillment by multiple subscriptions, subscriptions and that
the information included in attributes that fulfill each of these
subscriptions might overlap. The SWIMA-PC MUST send separate
attributes for each established subscription that requires a response
due to the given event. Each of these attributes MUST contain all
information required to fulfill that individual subscription, even if
that information is also sent in other attributes sent in fulfillment
of other subscriptions at the same time. In other words, SWIMA-PCs
MUST NOT attempt to combine information when fulfilling multiple
subscriptions simultaneously, even if this results in some redundancy
in the attributes sent to the SWIMA-PV.

3.8.5.5. Delayed Subscription Fulfillment

A SWIMA-PC MAY delay the fulfillment of a subscription following a
change event in the interest of waiting to see if additional change
events are forthcoming and, if so, conveying the relevant records
back to the SWIMA-PV in a single SWIMA Response attribute. This can
help reduce network bandwidth consumption between the SWIMA-PC and
the SWIMA-PV. For example, consider a situation where 10 changes
occur a tenth of a second apart. If the SWIMA-PC does not delay in
assembling and sending SWIMA Response attributes, the SWIMA-PV will
receive 10 separate SWIMA Response attributes over a period of
1 second. However, if the SWIMA-PC waits half a second after the
initial event before assembling a SWIMA Response, the SWIMA-PV only
receives two SWIMA Response attributes over the same period of time.

Note that the ability to consolidate events for a single subscription
over a given period of time does not contradict the rules in
Section 3.8.5.4 prohibiting consolidation across multiple
subscriptions. When delaying fulfillment of subscriptions, SWIMA-PCs
are still required to fulfill each individual subscription
separately. Moreover, in the case that change events within the
delay window cancel each other out (e.g., a record is deleted and
then re-added), the SWIMA-PC MUST still report each change event event,
rather than just reporting report the net effect of changes over the delay
period. In other words, delayed fulfillment can decrease the number
of attributes send sent by the SWIMA-PC, but it does not reduce the total
number of change events reported.

SWIMA-PCs are not required to support delayed fulfillment of
subscriptions. However, in the case that the SWIMA-PC does support
delayed subscription fulfillment, it MUST be possible to configure
the SWIMA-PC to disable delayed fulfillment. In other words, parties
deploying SWIMA-PCs need to be allowed to disable delayed
subscription fulfillment in their SWIMA-PCs. The manner in which
such configuration occurs is left to the discretion of implementers,
although implementers MUST protect the configuration procedure from
unauthorized tampering. In other words, there needs to be some
assurance that unauthorized individuals are not able to introduce
long delays in subscription fulfillment.

3.9. Error Handling

In the case where the SWIMA-PC detects an error in a SWIMA Request
attribute that it receives receives, it MUST respond with a PA-TNC Error
attribute with an error code appropriate to the nature of the error.
(See Section 4.2.8 of PA-TNC [RFC5792] for more details about PA-TNC
Error attributes and error codes as well as codes, and see Section 5.16 5.15 in this
specification for error codes specific to SWIMA Attributes.) attributes.) In the
case that an error is detected in a SWIMA Request Request, the SWIMA-PC
MUST NOT take any action requested by this SWIMA Request, even if
partial completion of the request is possible. In other words, a
SWIMA Request that contains an error is will be completely ignored by
the SWIMA-PC (beyond sending a PA-TNC Error attribute, attribute and possibly
logging the error locally) rather than being partially executed. locally); no attempt at partial completion of the
request will be made.

In the case where the SWIMA-PC receives a valid SWIMA Request
attribute but experiences an error during the process of responding
to that attribute's instructions where that error prevents the SWIMA-
PC
SWIMA-PC from properly or completely fulfilling that request, the
SWIMA-PC MUST send a PA-TNC Error attribute with an error code
appropriate to the nature of the error. In the case where a PA-TNC
Error attribute is sent, the SWIMA-PC MUST NOT take any of the
actions requested by the SWIMA Request attribute which that led to the
detected error. This is the case even if some actions could have
been completed successfully, successfully and might even require the SWIMA-PC to
reverse some successful actions already taken before the error
condition was detected. In other words, either (1) all aspects of a
SWIMA Request complete fully and successfully (in which case the
SWIMA-PC sends a SWIMA Response
attribute), attribute) or (2) no aspects of the
SWIMA Request occur (in which case the SWIMA-PC sends a PA-TNC Error
attribute). In the case that a SWIMA-PC sends a PA-TNC Error
attribute in response to a SWIMA
Request Request, then the SWIMA-PC MUST NOT
also send any SWIMA Response attribute in response to the same SWIMA
Request. For this reason, the sending of a SWIMA Response attribute
MUST be the last action taken by a SWIMA-PC in response to a SWIMA Request
Request, to avoid the possibility of a processing error occurring
after that SWIMA Response attribute is sent.

In the case that the SWIMA-PC detects an error that prevents it from
properly or completely fulfilling its obligations under an active
subscription, the SWIMA-PC MUST send a PA-TNC Error attribute of type with
error code SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR to the SWIMA-PV that
established this subscription. This type of PA-TNC Error attribute
identifies the specific subscription that cannot be adequately
honored due to the error condition as well as and also identifies an error "sub-type".
"subtype". The error sub-
type is used to indicate subtype indicates the type error code of the error
condition the SWIMA-PC experienced that prevented it from honoring
the given subscription. In the case that the error condition cannot
be identified or does not align with any of the defined error codes,
the SWIMA_ERROR error code SHOULD be used in the sub-type. subtype. In the
case that a SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR is sent, the
associated subscription MUST be treated as cancelled by both the
SWIMA-PC and the SWIMA-PV.

The SWIMA-PV MUST NOT send any PA-TNC Error attributes to SWIMA-PCs.
In the case that a SWIMA-PV detects an error condition, it SHOULD log
this error error, but the SWIMA-PV does not inform any SWIMA-PC's SWIMA-PCs of this
event. Errors might include, but are not limited to, the detection
of malformed SWIMA Response attributes sent from a given SWIMA-PC, as
well as the detection of error conditions when the SWIMA-PV processes
SWIMA Responses.

Both SWIMA-PCs and SWIMA-PVs SHOULD log errors so that administrators
can trace the causes of errors. Log entries SHOULD include the type code
of the error, the time it was detected, and additional descriptive
information to aid in understanding the nature and cause of the
error. Logs are an important debugging tool tool, and implementers are
strongly advised to include comprehensive logging capabilities in
their products.

4. Protocol

The software inventory SWIMA protocol supports two different types of message exchanges which
for conveying software inventory information. These message
exchanges are described in the following subsections, along with
implementation requirements for supporting them.

The SWIMA protocol also supports two simple status exchanges: a
Subscription Status exchange for conveying information about active
subscriptions, and a Source Metadata exchange for conveying
information about a SWIMA-PC's data sources. In both cases, a
SWIMA-PV sends a request attribute (Subscription Status Request or
Source Metadata Request, respectively) and a SWIMA-PC responds with a
matching response attribute (Subscription Status Response or Source
Metadata Response, respectively). As these
exchanges. exchanges are
straightforward, no additional information on the exchanges is
provided.

4.1. Direct Response to a SWIMA Request

The first type of software information exchange is used to provide
the SWIMA-PV with a software inventory or event collection from the
queried endpoint.

+-------------+ +--------------+
| SWIMA-PC | | SWIMA-PV | Time
+-------------+ +--------------+ |
| | |
|<-----------SWIMA Request------------| |
| | |
| SWIMA Response* | |
|-----------------or----------------->| |
| PA-TNC Error | |
| | V

*SWIMA Response is one of the following: Software Identifier
Inventory, Software Identifier Events, Software Inventory,
or Software Events.

Figure 4: SWIMA Attribute Exchange (Direct Response to SWIMA Request)

In this exchange, the SWIMA-PV indicates to the SWIMA-PC, via a SWIMA
Request, the nature of the information it wishes to receive
(inventory vs. events, full or targeted) and how it wishes the
returned inventory to be expressed (with or without software
inventory evidence records). Software
Inventory Evidence Records). The SWIMA-PC responds with the
requested information using the appropriate attribute type. A single
SWIMA Request MUST only lead to a single SWIMA Response or PA-TNC
Error that is in direct response to that request.

4.2. Subscription-Based Response

The second type of software information exchange allows change event-based change-event-
based reporting based on a subscription. If there is an active
subscription on the endpoint, the SWIMA-PC sends a SWIMA Response to
the SWIMA-PV following a change event on the endpoint in fulfillment
of that subscription. Such an exchange is shown in Figure 5.

*SWIMA Response is one of the following: Software Identifier
Inventory, Software Identifier Events, Software Inventory,
or Software Events.

Figure 5: SWIMA Attribute Exchange (In (in Fulfillment of an
Active Subscription)

Note that, that unlike direct responses to a SWIMA Request, a single change
event can precipitate multiple SWIMA Responses for a single
subscription, but only if all but the last of those SWIMA Responses
convey partial lists of event records. When providing multiple SWIMA
Responses in this way, the initial responses contain partial lists of
event records and the last of those SWIMA Responses conveys the
remainder of the relevant event records, completing the delivery of
all relevant events in response to the change event. A single Change
Event change
event MUST NOT otherwise be followed by multiple SWIMA Response Responses or
PA-TNC Error attributes in any combination.

4.3. Required Exchanges

All SWIMA-PVs and SWIMA-PCs MUST support both types of software
information exchanges. In particular, SWIMA-PCs MUST be capable of
pushing a SWIMA Response to a SWIMA-PV immediately upon detection of
a change to the endpoint's Software Inventory Evidence Collection in
fulfillment of established SWIMA-PV subscriptions, as described in
Section 3.8.

All SWIMA-PCs MUST support both status exchanges (Subscription Status
and Source Metadata); SWIMA-PVs are recommended to support these
status exchanges, but doing so is not required.

5. Software Inventory Messages and Attributes

This section describes the format and semantics of the SWIMA
protocol. This protocol uses the PA-TNC message header format
[RFC5792].

5.1. PA Subtype (AKA (aka PA-TNC Component Type)

The NEA PB-TNC [RFC5793] interface provides a general
message-batching protocol capable of carrying one or more PA-TNC
messages between the Posture Broker Client and Posture Broker Server.
When PB-TNC is carrying a PA-TNC message, the PB-TNC message headers
contain a 32 bit 32-bit identifier called the PA Subtype. "PA Subtype". The PA Subtype
field indicates the type of component associated with all of the
PA-TNC attributes carried by the PB-TNC message. The core set of
PA Subtypes is defined in the PA-TNC specification. This
specification defines a new "SWIMA Attributes" PA Subtype, which is
registered in Section 10.1 10.2 of this document, which document and is used as a
namespace for the collection of SWIMA Attributes attributes defined in this
document.

For more information on PB-TNC and PA-TNC messages and PA-TNC messages, as well
as their message headers, see the PB-TNC [RFC5793] and PA-TNC
[RFC5792] specifications, respectively.

5.2. SWIMA Attribute Overview

Each PA-TNC attribute described in this specification is intended to
be sent between the SWIMA-PC and SWIMA-PV, SWIMA-PV and so will be carried in a
PB-TNC message indicating a PA Subtype of "SWIMA Attributes". PB-TNC
messages MUST always include the SWIMA Attributes Subtype defined in
Section 5.1 when carrying SWIMA Attributes attributes over PA-TNC. The
attributes defined in this specification appear below below, along with a
short summary of their purposes.

PA-TNC attribute types are identified in the PA-TNC Attribute Header
via the PA-TNC Attribute Type Vendor ID field and the PA-TNC Attribute
Type fields. field; see Section 4.1 of [RFC5792] for details. Table 1
identifies the appropriate values for these fields for each attribute
type used within the SWIMA protocol. All attributes have a PEN value
of 0x000000. For the Integer value field, both Both the hexadecimal and decimal values are provided. provided in
the Integer column in the table. Each attribute is described in
greater detail in subsequent sections identified (identified in the attribute
description.

+--------------+------------+---------------------------------------+ table's
Description column).

Table 1: SWIMA Attribute Enumeration

Because one of the Software Identifier Inventory, Software Identifier
Events, Software Inventory, or Software Events attributes are is expected
to be sent to a SWIMA-PV in direct response to a SWIMA Request
attribute or in fulfillment of an active subscription, those four
attribute types are referred to collectively in this document as
"SWIMA Response attributes".

All SWIMA-PVs MUST be capable of sending SWIMA Request attributes and
be capable of receiving and processing all SWIMA Response attributes
as well as PA-TNC Error attributes. All SWIMA-PCs MUST be capable of
receiving and processing SWIMA Request attributes and be capable of
sending all types of SWIMA Response attributes as well as PA-TNC
Error attributes. In other words, both SWIMA-PVs and SWIMA-PCs are
required to support their role in exchanges using any of the
attribute types defined in this section. SWIMA-PVs MUST ignore any SWIMA Request attributes
that they receive. SWIMA-PCs MUST ignore any SWIMA Response
attributes or PA-TNC Error attributes that they receive.

5.3. Message Diagram Syntax

This specification defines uses diagrams to define the syntax of new PA-TNC
messages and
attributes using diagrams. attributes. Each diagram depicts the format and size of
each field in bits. Implementations MUST send the bits depicted in
each diagram as they are shown from left to right for each 32-bit quantity
traversing
quantity, "traversing" the diagram from top to bottom. Fields
representing numeric values MUST be sent in network (big endian) byte
order.

Descriptions of bit fields field (e.g., flags) flag) values refer to the position
of the bit within the field. These bit positions are numbered from
the most significant bit through the least significant bit. As such,
an octet with only bit 0 set would have a value of 0x80 (1000 0000),
an octet with only bit 1 set would have a value of 0x40 (0100 0000),
and an octet with only bit 7 set would have a value of 0x01
(0000 0001).

5.4. SWIMA Attribute Enumeration

5.5. Normalization of Text Encoding

In order to ensure consistency of transmitted attributes attributes, some fields
require normalization of their format. When this is necessary, this
information is indicated in the field's description. In such cases,
the field contents MUST be normalized to Network Unicode format as
defined in RFC 5198 [RFC5198]. Network Unicode format defines a
refinement of UTF-8 [RFC3629] that ensures a normalized expression of
characters. SWIMA-PCs and SWIMA-PVs MUST NOT perform conversion and
normalization on any field values except those specifically
identified as requiring
normalization in the following sections. sections as requiring normalization.
Note, however, that some data models require additional normalization
before source information is added to an Endpoint's endpoint's Software
Inventory Evidence Collection as a record. The references from the Software
"Software Data Model IANA table Types" registry (see Section 10.4) 10.5) will note
where this is necessary.

5.6.

5.5. Request IDs

All SWIMA Request attributes MUST include a Request ID value. The
Request ID field provides a value that identifies a given request
relative to other requests between a SWIMA-PV and the receiving
SWIMA-PC. Specifically, the SWIMA-PV assigns each SWIMA Request
attribute a Request ID value that is intended to be unique within the
lifetime of a given network connection ID as assigned by the SWIMA-
PV's Posture Broker Server. Connection ID.

In the case that a SWIMA Request requests the establishment of a
subscription and the receiving SWIMA-PC agrees to that subscription,
the Request ID of that SWIMA Request (i.e., the establishing request
of the subscription) becomes that subscription's Subscription ID.
All attributes sent in fulfillment of this subscription include a
flag indicating that the attribute fulfills a subscription and the
subscription's Subscription ID. A SWIMA-PV MUST NOT reuse a Request
ID value in communicating to communications with a given SWIMA-PC while that Request
ID is also serving as a Subscription ID for an active subscription
with that SWIMA-PC. In the case where a SWIMA-PC receives a SWIMA
Request from a given SWIMA-PV where that Request ID is also the
Subscription ID of an active subscription with that SWIMA-PV, the
SWIMA-PC MUST respond with a PA-TNC Error attribute with an error
code of SWIMA_SUBSCRIPTION_ID_REUSE_ERROR. Note that this error does
not cancel the indicated subscription.

Subscription Status Requests and Subscription Status Responses do not
include Request IDs.

In the case where all possible Request ID values have been exhausted
within the lifetime of a single network connection Connection ID, the sender MAY
reuse previously used Request IDs within the same network connection
if the ID is not being used as a Subscription ID. In such a case of
Request ID reuse, Request IDs SHOULD be reused in the order of their
original use. In other words, a SWIMA-PC SHOULD NOT use a given
Request ID value more than once within a persistent connection
between a given Posture Broker Client-Posture Broker Server pair. In the case where
reuse is necessary due to exhaustion of possible ID values, the SWIMA-PC
SWIMA-PV SHOULD structure the reuse to maximize the time between
original and subsequent use. The Request ID value is included in a
SWIMA Response attribute directly responding to this SWIMA Request to
indicate which SWIMA Request was received and caused the response.
Request IDs can be randomly generated or sequential, as long as
values are not repeated per the rules in this paragraph. SWIMA-PCs
are not required to check for duplicate Request IDs.

5.7. IDs, except insofar
as is necessary to detect Subscription ID reuse.

5.6. SWIMA Request

A SWIMA-PV sends this attribute to a SWIMA-PC to request that the
SWIMA-PC send software inventory information to the SWIMA-PV. A
SWIMA-PC MUST NOT send this attribute.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Software Identifier Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Earliest EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SUB-BLOCK (Repeated "Software Identifier Count" times) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 6: SWIMA Request Attribute

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Identifier Length | Software Identifier (var len) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Table 2: SWIMA Request Attribute Fields

The SWIMA-PV sends the SWIMA Request attribute to a SWIMA-PC to
request the indicated information. Note that between the Result Type
flag and the Earliest EID field, the SWIMA-PC is constrained to a
single possible SWIMA Response attribute type (or a PA-TNC Error
attribute) in its response to the request.

The Subscribe flag and the Clear Subscription flags Subscriptions flag are used to
manage subscriptions for the requesting SWIMA-PV on the receiving
SWIMA-PC. Specifically, an attribute with the Subscribe flag set
seeks to establish a new subscription by the requesting SWIMA-PV to
the given SWIMA-PC, while an attribute with the Clear Subscription Subscriptions
flag set seeks to delete all existing subscriptions by the requesting
SWIMA-PV on the given SWIMA-PC. Note that, that in the latter case, only
the subscriptions associated with the Connection ID and the Posture
Validator ID Identifier of the requester are deleted as described in
Section 3.8.3. A newly established subscription has the parameters
outlined in the SWIMA Request attribute. Specifically, the Result
Type flag indicates the type of result to send in fulfillment of the
subscription, the value of the Earliest EID field indicates whether
the fulfillment attributes list inventories or events, and the fields
describing Software Identifiers (if present) indicate if and how a
subscription is targeted. In the case that the SWIMA-PC is unable or
unwilling to comply with the SWIMA-PV's request to establish or clear
subscriptions, the SWIMA-PC MUST respond with a PA-TNC Error
attribute with the SWIMA_SUBSCRIPTION_DENIED_ERROR error code. If
the SWIMA-PV requests that subscriptions be cleared but has no
existing subscriptions, this is not an error.

An attribute requesting the establishment of a subscription is
effectively doing double-duty, "double duty", as it is a request for an immediate
response from the SWIMA-PC in addition to setting up the
subscription. Assuming that the SWIMA-PC is willing to comply with
the
subscription subscription, it MUST send an appropriate response attribute to a
request with the Subscribe flag set containing all requested
information. The same is true of the Clear Subscription Subscriptions flag - --
assuming that there is no error error, the SWIMA-PC MUST generate a
response attribute without regard to the presence of this flag flag, in
addition to clearing its subscription list.

Both the Subscribe flag and the Clear Subscription flags Subscriptions flag MAY be set
in a single SWIMA Request attribute. In the case where this request
is successful, the end result MUST be equivalent to the SWIMA-PC
clearing its subscription list for the given SWIMA-PV first and then
creating a new subscription in accordance with the request
parameters. In other words, do not first create the new subscription
and then clear all the subscriptions including (including the one that was just
created.
created). In the case that the requested actions are successfully
completed, the SWIMA-PC MUST respond with a SWIMA Response attribute.
The specific type of SWIMA Response attribute depends on the Result
Type flag and the Earliest EID fields, field, as described above. In the
case where there is a failure that prevents some part of this request
from completing, the SWIMA-PC MUST NOT add a new subscription,
MUST NOT clear the old subscriptions, and the SWIMA-PC MUST respond with a PA-
TNC PA-TNC
Error attribute. In other words, the SWIMA-PC MUST NOT partially
succeed at implementing such a request; either all actions succeed, succeed or
none succeed.

The Earliest EID field is used to indicate if the SWIMA-PV is
requesting an inventory or event list from the SWIMA-PC. A value of
0 (0x00000000) represents a request for inventory information.
Otherwise, the SWIMA-PV is requesting event information. For
Earliest EID values other than 0, the SWIMA-PC's response SWIMA-PC MUST respond with
event records, as described in Section 3.7. Note that the request
does not identify a particular EID Epoch, since responses can only
include events in the SWIMA-PC's current EID Epoch.

The Software Identifier Count indicates the number of Software
Identifiers in the attribute. This number might be any value between
0 and 16,777,216, inclusive. A single Software Identifier is
represented by the following fields: Software Identifier Length and
Software Identifier. These fields are repeated a number of times
equal to the Software Identifier Count, which may be 0. The Software
Identifier Length field indicates the number of bytes allocated to
the Software Identifier field. The Software Identifier field
contains a Software Identifier as describe described in Section 3.4.1. The
presence of one or more Software Identifiers is used by the SWIMA-PV
to indicate a targeted request, which seeks only inventories of or
events affecting software corresponding to the given identifiers.
The SWIMA-PC MUST only report software that matched the Software
Identifiers provided in the SWIMA-PVs SWIMA-PV's SWIMA Request attribute.

5.8.

5.7. Software Identifier Inventory

A SWIMA-PC sends this attribute to a SWIMA-PV to convey the inventory
of the endpoint's Software Inventory Evidence Collection without the
inclusion of software inventory evidence records. Software Inventory Evidence Records. This list might
represent a complete inventory or a targeted list of records,
depending on the parameters in the SWIMA-PV's request. A SWIMA-PV
MUST NOT send this attribute. The SWIMA-PC either sends this attribute
either (1) in fulfillment of an existing subscription where the
establishing request has a Result Type of 1 and the Earliest EID is
zero,
zero or (2) in direct response to a SWIMA Request attribute where the
Result Type is 1 and the Earliest EID is zero.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Software Identifier Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SUB-BLOCK (Repeated "Software Identifier Count" times) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 8: Software Identifier Inventory Attribute
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Model Type PEN |Data Model Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Id Num | Reserved | Software Identifier Length |Software Id (v)| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Identifier (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Locator Length |Software Locator (variable len)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 9: Software Identifier Inventory Attribute SUB-BLOCK

Table 3: Software Identifier Inventory Attribute Fields

In the case that this attribute is sent in fulfillment of a
subscription, the Subscription Fulfillment bit MUST be set (1). In
the case that this attribute is sent in direct response to a SWIMA
Request, the Subscription Fulfillment bit MUST be unset (0). Note
that the SWIMA Response attribute sent in direct response to a SWIMA
Request that establishes a subscription (i.e., a subscription's
establishing request) MUST be treated as a direct response to that
SWIMA Request (and thus the Subscription Fulfillment bit is unset).
SWIMA Response attributes are only treated as being in fulfillment of
a subscription (i.e., Subscription Fulfillment bit set) if they are
sent following a change event, as shown in Figure 3.

The Software Identifier Count field indicates the number of Software
Identifiers present in this inventory. Each Software Identifier is
represented by the following set of fields: Record Identifier, Data
Model Type PEN, Data Model Type, Source Identification Number,
Reserved, Software Identifier Length, Software Identifier, Software
Locator Length, and Software Locator. These fields will appear once
for each reported record.

When responding directly to a SWIMA Request attribute, the Request ID
Copy / Subscription ID field MUST contain an exact copy of the
Request ID field from that SWIMA Request. When this attribute is
sent in fulfillment of an existing subscription on this Posture
Collector, then SWIMA-PC,
this field MUST contain the Subscription ID of the fulfilled
subscription.

The EID Epoch field indicates the EID Epoch of the Last EID value.
The Last EID field MUST contain the EID of the last recorded change
event (see Section 3.7 for more about EIDs and recorded events) at
the time this inventory was collected. In the case where there are
no recorded change events at the time that this inventory was
collected, the Last EID field MUST contain 0. These fields can be
interpreted to indicate that the provided inventory reflects the
state of the endpoint after all changes up to and including this last
event have been accounted for.

The Data Model Type PEN and Data Model Type fields are used to
identify the data model associated with the given software record.
These fields are discussed more in Section 3.4.2.

The Source Identification Number field is used to identify the source
that provided the given record, as described in Section 3.1.

5.9.

5.8. Software Identifier Events

A SWIMA-PC sends this attribute to a SWIMA-PV to convey events where
the affected records are reported without software inventory evidence
records. Software Inventory Evidence
Records. A SWIMA-PV MUST NOT send this attribute. The SWIMA-PC
either
sends this attribute either (1) in fulfillment of an existing
subscription where the establishing request has a Result Type is of 1
and the Earliest EID is non-zero, non-zero or (2) in direct response to a SWIMA
Request attribute where the Result Type is 1 and the Earliest EID is
non-zero.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Event Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Consulted EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SUB-BLOCK (Repeated "Event Count" times) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 10: Software Identifier Events Attribute
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- -+
| |
+- -+
| Timestamp |
+- -+
| |
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Model Type PEN |Data Model Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Id Num | Action | Software Identifier Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Identifier (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Locator Length |Software Locator (variable len)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Table 4: Software Identifier Events Attribute Fields

The first few fields in the Software Identifier Events attribute
mirror those in the Software Identifier Inventory attribute. The
primary difference is that, that instead of conveying an inventory, inventory the
attribute conveys zero or more event records, consisting of the EID,
timestamp,
Timestamp, Record Identifier, action type, data model type, Data Model Type PEN, Data Model Type,
Source Identification Number, Action, Software Identifier Length,
Software Identifier, Software Locator Length, and Software Locator
fields of the affected software inventory
evidence record. Software Inventory Evidence Record.

With regard to the Timestamp field, it is important to note that
clock skew between the SWIMA-PC and SWIMA-PV as well as between
different SWIMA-PCs within an enterprise might make correlation of
timestamp
Timestamp values difficult. This specification does not attempt to
resolve clock skew issues, although other mechanisms (which are
outside the scope of this
specification specification) do exist to reduce the
impact of clock skew and make the timestamp more useful for such
correlation. Instead, SWIMA uses the Timestamp value primarily as a
means to indicate the amount of time between two events on a single
endpoint. For example, by taking the difference of the times for
when a record was removed and then subsequently re-added, one can get
an indication as to how long the system was without the given record (and,
(and thus without the associated software). Since this will involve
comparison of timestamp Timestamp values all originating on the same system,
clock skew between the SWIMA-PC and SWIMA-PV is not an issue.
However, if the SWIMA-PC's clock was adjusted between two recorded
events, it is possible for such a calculation to lead to incorrect understandings of
misunderstandings regarding the temporal distance between events.
Users of this field need to be aware of the possibility for such
occurrences. In the case where the Timestamp values of two events
appear to contradict the EID ordering of those events (i.e., the
later EID has an earlier timestamp) timestamp), the recipient MUST treat the EID
ordering as correct.

All events recorded in a Software Identifier Events Attribute attribute are
required to be part of the same EID Epoch. Specifically, all such
reported events MUST have an EID that is from the same EID Epoch as each
other, and which
that is the same as the EID Epoch of the Last EID and Last Consulted
EID values. The SWIMA-PC MUST NOT report events with EIDs from
different EID Epochs.

The Last Consulted EID field contains the EID of the last event
record considered for inclusion in this attribute. If this attribute
contains a partial event set (as described in Section 3.7.5) 3.7.5), this
field value will be less than the Last EID value; if this attribute
contains a complete event set, the Last EID and Last Consulted EID
values are identical.

If multiple events are sent in a Software Identifier Events
attribute, the order in which they appear within the attribute is not
significant. The EIDs associated with them are used for ordering the
indicated events appropriately. Also note that a single software
record might be reported multiple times in an attribute, such as if
multiple events involving the associated record were being reported.

5.10.

5.9. Software Inventory

A SWIMA-PC sends this attribute to a SWIMA-PV to convey a list of
inventory records. A SWIMA-PV MUST NOT send this attribute. The
SWIMA-PC either sends this attribute either (1) in fulfillment of an
existing subscription where the establishing request had has a Result
Type of 0 and the Earliest EID is zero, zero or (2) in direct response to a
SWIMA Request attribute where the Result Type is 0 and the Earliest
EID is zero.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SUB-BLOCK (Repeated "Record Count" times) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 12: Software Inventory Attribute

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Model Type PEN |Data Model Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Id Num | Reserved | Software Identifier Length |Software Id (v)| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Identifier (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Locator Length |Software Locator (variable len)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Table 5: Software Inventory Attribute Fields
The Software Inventory attribute contains some number of software
inventory evidence records Software
Inventory Evidence Records along with the core response attribute
fields. Given that the size of records can vary considerably, the
length of this attribute is highly variable and, if transmitting a
complete inventory, can be extremely large. Enterprises To avoid unnecessarily
overburdening the network, enterprises might wish to constrain the
use of Software Inventory attributes to targeted
requests to avoid over-burdening the network unnecessarily. requests.

When copying a software inventory evidence record Software Inventory Evidence Record into the Record
field, the record MUST be converted and normalized to use Network
Unicode format prior to its inclusion in the record Record field.

5.11.

5.10. Software Events

A SWIMA-PC sends this attribute to a SWIMA-PV to convey a list of
events that include software inventory evidence records. Software Inventory Evidence Records. A SWIMA-PV
MUST NOT send this attribute. The SWIMA-PC either sends this attribute
either (1) in fulfillment of an existing subscription where the
establishing request has a Result Type of 0 and the Earliest EID is
non-zero,
non-zero or (2) in direct response to a SWIMA Request attribute where
the Result Type is 0 and the Earliest EID is non-zero.

Figure 14: Software Events Attribute
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- -+
| |
+- -+
| Timestamp |
+- -+
| |
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Model Type PEN |Data Model Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Id Num | Action | Software Identifier Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Identifier (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Locator Length |Software Locator (variable len)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record (variable Length) length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Table 6: Software Events Attribute Fields

The fields of this attribute are used in the same way as the
corresponding fields of the previous attributes. As with the
Software Inventory attribute, a Software Events attribute can be
quite large if many events have occurred following the event
indicated by a request's Earliest EID. As such, it is recommended
that the SWIMA Request attributes only request that full records be
sent (Result Type set to 0) zero) in a targeted request, thus
constraining the response just to records that match a given set of
Software Identifiers.

As with the Software Identifier Events Attribute, attribute, this attribute MUST
only contain event records with EIDs coming from the current EID
Epoch of the SWIMA-PC.

As with the Software Inventory Attribute, attribute, the SWIMA-PC MUST perform
conversion and normalization of the record.

5.12.

5.11. Subscription Status Request

A SWIMA-PV sends this attribute to a SWIMA-PC to request a list of
active subscriptions for which the requesting SWIMA-PV is the
subscriber. A SWIMA-PC MUST NOT send this attribute.

This attribute has no fields.

A SWIMA-PC MUST respond to this attribute by sending a Subscription
Status Response attribute (or a PA-TNC Error attribute if it is
unable to correctly provide a response).

5.13.

5.12. Subscription Status Response

A SWIMA-PC sends this attribute to a SWIMA-PV to report the list of
active subscriptions for which the receiving SWIMA-PV is the
subscriber. A SWIMA-PV MUST NOT send this attribute.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status Flags | Subscription Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SUB-BLOCK (Repeated "Subscription Record Count" times) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 16: Subscription Status Response Attribute

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Software Identifier Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Earliest EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SUB-SUB-BLOCK (Repeated "Software Identifier Count" times) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 17: SWIMA Subscription Status Response Attribute SUB-BLOCK

Table 7: Subscription Status Response Fields

A Subscription Status Response contains zero or more subscription
records. Specifically, it MUST contain one subscription record for
each active subscription associated with the party that sent the
Subscription Status Request to which this attribute is a response.
As described in Section 3.8.2, the SWIMA-PC MUST use the requester's
Connection ID and its Posture Validator ID Identifier to determine which
subscriptions are associated with the requester.

A SWIMA-PC MUST send a Subscription Status Response attribute in
response to a Subscription Status Request attribute. The only
exception to this is if attribute, except in cases
where the SWIMA-PC experiences an error condition that prevents it
from correctly populating the Subscription Status Response attribute, in attribute
(in which case it MUST respond with a PA-TNC Error attribute
appropriate to the type of error experienced. experienced). If there are no
active subscriptions associated with the requesting party, the
Subscription Status Response attribute will consist only of its
Status Flags field, field and a Subscription Record Count field with a value
of 0, and no additional fields.

Each subscription record included in a Subscription Status Response
attribute duplicates the fields of a the SWIMA Request attribute that
was the establishing request of a subscription. Note that the
Request ID field in the record captures the Subscription ID
associated with the given subscription record (since the Subscription
ID is the same as the Request ID of the establishing request). Note
also that if the establishing request is targeted, then its Record
Count field will be non-zero and, within that subscription record,
the Software Identifier Length and Software Identifier fields are
repeated, in order, the number of times indicated in the Record Count
field. As such, each subscription record can be different sizes. If
the establishing request is not targeted (Record Count field is 0),
the subscription record has no Software Identifier Length or Software
Identifier fields.

When a SWIMA-PV compares the information received in a Subscription
Status Response to its own records of active subscriptions subscriptions, it should
be aware that the SWIMA-PC might be unable to distinguish this SWIMA-
PV
SWIMA-PV from other SWIMA-PVs on the same NEA Server. As a result,
it is possible that the SWIMA-PC will report more subscription
records than the SWIMA-PV recognizes. For this reason, SWIMA-PVs
SHOULD NOT automatically assume that extra subscriptions reported in
a Subscription Status Response indicate a problem.

5.14.

5.13. Source Metadata Request

A SWIMA-PV sends this attribute to a SWIMA-PC to request metadata
about sources that the SWIMA-PC is using to collect software
inventory information. A SWIMA-PC MUST NOT send this attribute.

This attribute has no fields.

A SWIMA-PC MUST respond to this attribute by sending a Sources Source
Metadata Response attribute (or a PA-TNC Error attribute if it is
unable to correctly provide a response).

5.15.

5.14. Source Metadata Response

A SWIMA-PC sends this attribute to a SWIMA-PV to provide descriptive
metadata about the sources of software inventory information used by
the SWIMA-PC. A SWIMA-PV MUST NOT send this attribute.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Source Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| SUB-BLOCK (Repeated "Source Count" times times) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 19: Source Metadata Response Attribute

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source ID Id Num | Metadata Length | Metadata (var)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 20: Source Metadata Response Attribute SUB-BLOCK
+----------+--------------------------------------------------------+
+----------------+--------------------------------------------------+
| Field | Description |
+----------+--------------------------------------------------------+
+----------------+--------------------------------------------------+
| Reserved | Reserved for future use. This field MUST be set to |
| | to zero on transmission and ignored upon |
| | reception. |
| | |
| Source Count | The number of source records that follow. The Source |
| Count | ID, Source Identification Number, Metadata Size, Length, |
| | and Metadata fields are repeated, |
| | in order, the |
| | number of times indicated by this field. This |
| | This field MAY be 0, in which case no fields follow |
| | (but this would only be done to indicate that the |
| | the SWIMA-PC has no active sources, which sources; this would not be a |
| | usual not be a typical situation). |
| | |
| Source | The Source ID Identifier number associated with the described |
| ID Identification | described source for any communications with the recipient |
| Number | recipient SWIMA-PV. |
| | |
| Metadata | A 2-byte unsigned integer indicating the length in length, |
| Length | bytes in bytes, of the Metadata field. |
| | |
| Metadata | A string containing descriptive metadata about the |
| | the indicated data source. This string MUST NOT be NULL |
| | be null terminated. |
+----------+--------------------------------------------------------+
+----------------+--------------------------------------------------+

Table 8: Source Metadata Response Fields

A Source Metadata Response attribute contains 0 zero or more records,
each describing one of the data sources the SWIMA-PC uses to collect
software inventory information. It SHOULD contain one metadata
record for each source that the SWIMA-PC uses. (There might be
reasons not to inform certain SWIMA-PVs of the presence of certain
data sources.) The attribute MUST contain a metadata record for each
source that has been identified in inventory or event messages to the
given SWIMA-PV.

A SWIMA-PC MUST send a Source Metadata Response attribute in response
to a Source Metadata Request attribute. The only exception to this
is if attribute, except in cases where the
SWIMA-PC experiences an error condition that prevents it from
correctly populating the Source Metadata Response attribute, in attribute (in which
case it MUST respond with a PA-TNC Error attribute appropriate to the
type of error experienced. experienced).

The Source Count field indicates how many source metadata records are
included in the attribute. Each included record consists of a Source
Identifier,
Identification Number field, a Metadata Length, Length field, and a Metadata
field.

The Source Identifier Identification Number field in the Source Metadata
Response attribute corresponds to the Source Identifier Identification Number
field in inventory and event messages. In the case where (1) the
Source
Identifier Identification Number value in a Source Metadata Response this attribute matches a Source Identifier associated with
Identification Number field in an event or inventory or event record and
(2) both the Source Metadata Response and the inventory/event inventory or event
record were sent to the same SWIMA-PV, the source described in the
Metadata field MUST be the same source that provided the event or inventory or
event record associated with the this Source Identifier. Recall that a
SWIMA-PC MAY use different Source Identifier Identification Number associations
with different SWIMA-
PVs. SWIMA-PVs. As such, the association between a Source Identifier
Identification Number and the conveyed metadata is also only
meaningful for communications between the sending SWIMA-PC and
receiving SWIMA-PV. When sending to a given SWIMA-PV, the SWIMA-PC
MUST use the recipient SWIMA-PVs SWIMA-PV's Source
Identifier Identification Number
associations.

The Metadata Length field indicates the length, in bytes, if of the
Metadata field. The Metadata field contains information about the
indicated data source. This specification does not dictate a format
for the contents of the Metadata field. This field MAY include machine-
readable
machine-readable information. For broadest utility, the Metadata
field SHOULD include human-readable, descriptive information about
the data source.

5.16.

5.15. PA-TNC Error as Used by SWIMA

The PA-TNC Error attribute is defined in the PA-TNC specification
[RFC5792], and its use here conforms to that specification. A PA-TNC
Error can be sent due to any error in the PA-TNC exchange and might
also be sent in response to error conditions specific to the SWIMA
exchange. The latter case utilizes error codes defined below.

A PA-TNC Error MUST be sent by a SWIMA-PC in response to a SWIMA
Request in the case where the SWIMA-PC encounters a fatal error
(i.e., an error that prevents further processing of an exchange)
relating to the attribute exchange. A SWIMA-PV MUST NOT send this
attribute. In the case where the SWIMA-PV experiences a fatal error,
it MUST handle the error without sending a PA-TNC Error attribute.
The SWIMA-PV MAY take other actions in response to the error, such as
logging the cause of the error, error or even taking actions to isolate the
endpoint.

A PA-TNC Error attribute is sent instead of a SWIMA Response
attribute due to factors that when certain issues prevent the reliable creation of a
SWIMA Response. As such, a SWIMA-PC MUST NOT send both a PA-TNC
Error attribute and a SWIMA Response attribute in response to a
single SWIMA Request attribute.

Table 8 9 lists the Error Code error code values for the PA-TNC Error attribute
that are specific to the SWIMA exchange. Error codes are shown in
both hexadecimal and decimal format. In all of these cases, the
Error Code Vendor ID field MUST be set to 0x000000, corresponding to
the IETF SMI Private Enterprise Number. PEN. The Error Information error information structures for each error type
code are described in the following subsections.

Note that a message with a SWIMA attribute might also result in an
error condition covered by the IETF Standard PA-TNC Error Codes
defined in
PA-TNC. Section 4.2.8 of [RFC5792]. For example, a SWIMA Attribute
attribute might have an invalid parameter, leading to an error code
of "Invalid Parameter". In this case, the SWIMA-PC MUST use the
appropriate PA-TNC Error Code value as defined in Section 4.2.8 of PA-TNC specification.

+------------+------------------------------------------------------+
[RFC5792].

Table 8: 9: PA-TNC Error Codes for SWIMA
The following subsections describe the structures present in the
Error Information
error information fields. Note that all error structures include a
variable-length field, field but do not include any fields indicating the
length of those fields. Such a A length field is unnecessary because all
other fields in the PA-TNC Error attribute are fixed-length, of fixed length, and
thus the length of the variable-length field can be found by
subtracting the size of these fixed-length fields from the PA-TNC
Attribute Length field in the PA-TNC Attribute Header.

5.16.1.

5.15.1. SWIMA_ERROR, SWIMA_SUBSCRIPTION_DENIED_ERROR SWIMA_SUBSCRIPTION_DENIED_ERROR, and
SWIMA_SUBSCRIPTION_ID_REUSE_ERROR Information

The SWIMA_ERROR error code indicates that the sender (the SWIMA-PC)
has encountered an error that is related to the processing of a SWIMA
Request attribute but which that is not covered by more specific SWIMA error
codes. codes that
are more specific. The SWIMA_SUBSCRIPTION_DENIED_ERROR is used when
the SWIMA-PV
requests sends a request to establish a subscription or clear all
subscriptions from the given SWIMA-PV, SWIMA-PV but the SWIMA-PC is unable or
unwilling to comply with this request. The
SWIMA_SUBSCRIPTION_ID_REUSE_ERROR is used when the SWIMA-PC receives
a SWIMA Request whose Request ID duplicates a Subscription ID of an
active subscription with the request's sender. All of these error
codes use the following error information structure.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Copy of Request ID / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Description (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 19: SWIMA Error, Subscription Error, 21: SWIMA_ERROR, SWIMA_SUBSCRIPTION_DENIED_ERROR, and Subscription ID Reuse
SWIMA_SUBSCRIPTION_ID_REUSE_ERROR Information
+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Copy of | In the case that this error condition is generated |
| Request ID / | in direct response to a SWIMA Request attribute, |
| Subscription | this field MUST contain an exact copy of the |
| ID | Request ID field in the SWIMA Request attribute |
| | that caused this error. In the case that the |
| | attribute in question is generated in fulfillment |
| | of an active subscription, this field MUST contain |
| | the Subscription ID of the subscription for which |
| | the attribute was generated. (This is only |
| | possible if the error code is SWIMA_ERROR SWIMA_ERROR, as the |
| | other errors are not generated by subscription |
| | fulfillment.) Note that, that in this case, the case of failed |
| | subscription fulfillment, the indicated error |
| | appears as a sub-error for a |
| | SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR, as described |
| | in Section 5.16.3. 5.15.3. |
| | |
| Description | A UTF-8 [RFC3629] string describing the condition |
| | that caused this error. This field MAY be zero- |
| | 0-length. length. However, senders SHOULD include some kind |
| | of description in all PA-TNC Error attributes of with |
| | these types. error codes. This field MUST NOT be NULL null |
| | terminated. |
+--------------+----------------------------------------------------+

Table 9: SWIMA Error, Subscription Error, 10: SWIMA_ERROR, SWIMA_SUBSCRIPTION_DENIED_ERROR, and Subscription ID Reuse
SWIMA_SUBSCRIPTION_ID_REUSE_ERROR Information Fields

This error information structure is used with SWIMA_ERROR,
SWIMA_SUBSCRIPTION_DENIED_ERROR, and
SWIMA_SUBSCRIPTION_ID_REUSE_ERROR status codes to identify the SWIMA
Request attribute that precipitated the error condition and to
describe the error. The Description field contains text describing
the error. The SWIMA-PC MAY encode machine-interpretable information
in this field, field but SHOULD also include a human-readable description of
the error, since the receiving SWIMA-PV might not recognize the
SWIMA-PC's encoded information.

5.16.2.

5.15.2. SWIMA_RESPONSE_TOO_LARGE_ERROR Information

The SWIMA_RESPONSE_TOO_LARGE_ERROR error code indicates that a
response generated by a SWIMA-PC in
SWIMA-PC's response to a SWIMA-PV's SWIMA Request attribute was too
large to send.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Copy of Request ID / Subscription I ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Allowed Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Description (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Table 10: SWIMA Response Too Large Error 11: SWIMA_RESPONSE_TOO_LARGE_ERROR Information Fields

This error structure is used with the SWIMA_RESPONSE_TOO_LARGE_ERROR
status code to identify the SWIMA Request attribute that precipitated
the error condition and to describe the error. The Maximum Allowed
Size field indicates the largest attribute the SWIMA-PC is willing to
send in response to a SWIMA Request under the current circumstances.
Note that under other circumstances, the SWIMA-PC might be willing to
return larger or smaller responses than indicated (such as if the
endpoint connects to the NEA Server using a different network
protocol). The other fields in this error information structure have
the same meanings as corresponding fields in the SWIMA_ERROR and
SWIMA_SUBSCRIPTION_DENIED_ERROR information structure.

5.16.3. structures.

5.15.3. SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR Information

The SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR error code indicates that
the SWIMA-PC encountered an error while fulfilling a subscription.
The bytes after the first 4 octets duplicate a PA-TNC Error attribute
(as described in Section 4.2.8 of PA-TNC) PA-TNC [RFC5792]) that is used to
identify the nature of the encountered error.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Sub Error Sub-error Code Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub Error Sub-error Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub Error Sub-error Information (variable Length) length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Table 11: SWIMA Subscription Fulfillment Error 12: SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR Information Fields

This error structure is used with the
SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR status code. The first 4 octets
of this error structure contain the Subscription ID of the
subscription that was being fulfilled when the error occurred. The
remaining fields of this error structure duplicate the fields of a
PA-TNC Error attribute, referred to as the "sub-error". The error
code of the sub-error corresponds to the type code of the error that the
SWIMA-PC encountered while fulfilling the given subscription. The
sub-error MUST NOT have an error code of
SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR.

The SWIMA-PC sending a PA-TNC Error attribute with this error code,
and the SWIMA-PV receiving it, MUST treat the subscription identified
by the Subscription ID field as cancelled. All other subscriptions
are unaffected.

6. Supported Data Models

SWIMA supports an extensible list of data models for representing and
transmitting software inventory information. This list of data
models appears in the Software "Software Data Model IANA Types" registry (see
Section 10.4). 10.5). This document provides guidance for an initial set of
data models. Other documents might provide guidance on the use of
new data models by SWIMA, SWIMA and will be referenced by extensions to the
Software
"Software Data Model IANA Types" registry.

6.1. ISO 2015 SWID Tags using Using XML

The International Organization for Standardization and the
International Electrotechnical Commission (ISO/IEC) published the
specification governing SWID tag construction and use
(ISO/IEC 19770-2:2009) in 2009 [SWID09], with a revised version of
the specification (ISO/IEC 19770-2:2015) published in 2015. [SWID15] 2015 [SWID15].
Since that time, a growing number of vendors have integrated SWID
tags into their software products. Doing so SWID tags significantly simplifies simplify
the task of identifying these pieces of software: instead of relying on
discovery processes that look for clues as to software presence, such
as the presence of particular files or registry keys. A keys, vendors can use
a readily available list of SWID tags that provides simple and
immediate evidence as to the presence of the given piece of software.

SWIMA has no reliance on the presence or management of SWID tags on
an endpoint as described in the ISO 2015 SWID tag specification.
However, as presented in the ISO 2015 SWID tag specification, the
data model for describing software that is presented in the ISO
specification provides a robust and
comprehensive way of describing software and is adopted here as a
means of representing and transmitting software information. It
should be emphasized, emphasized that the use of the ISO SWID tag data model
makes no assumption as to whether (1) the source of the recorded
information was, in fact, an ISO SWID tag harvested from the endpoint
or whether (2) the information was created using some other source and
normalized to the SWID format.

6.1.1. Guidance on Normalizing Source Data to ISO 2015 SWID Tags using
Using XML

Any record associated with this Software Data Model Type MUST conform
to the ISO/IEC 19770-2-2015 [SWID15] specification. [SWID15].

If generating a new ISO 2015 SWID tag, the software generating the
tag MUST use a Tag Creator RegID that is associated with the
generating software, unless this is impossible, in which case it MUST
use the "http://invalid.unavailable" Tag Creator RegID value. (This
conforms to conventions for an unknown Tag Creator tag creator in the ISO 2015
SWID tag specification.) Do not use a RegID associated with any
other party. In particular, it is incorrect to use a Tag Creator
RegID associated with the software being described by the tag, the
enterprise that is using the software, or any other entity except
that of the party that built the tool that is generating the SWID
tag. This reflects the requirement that the Tag Creator RegID
identify the party that created the tag. Moreover, any generated
tags SHOULD conform with to guidance for tag creators as provided NIST IR in
NISTIR 8060 [NIST8060], which provides additional recommendations to
increase interoperable use of SWID tags.

6.1.2. Guidance on Creation of Software Identifiers from ISO 2015
SWID Tags

A Software Identifier generated from an ISO 2015 SWID tag is
expressed as a concatenation of the value of the Tag Creator RegID
field and the Unique ID field. Specifically, (1) it MUST be of the form:
form TAG_CREATOR_REGID "_" "_" UNIQUE_ID. Specifically, the Software
Identifier UNIQUE_ID and (2) it consists of, of the
Tag Creator RegID and the Unique ID from the tag connected with a
double underscore (_), without any other connecting character or
whitespace.

6.2. ISO 2009 SWID Tags using Using XML

As noted above, ISO's SWID tag specification provides a useful data
model for representation of software information. As of the writing
of this specification, while the ISO 2015 specification is considered
more comprehensive and addresses some issues with the ISO 2009
specification, 2009-format SWID tags remain far more common in
deployments. For this reason, ISO 2009 SWID tags are included in the
Software
"Software Data Model IANA table. Types" registry.

6.2.1. Guidance on Normalizing Source Data to ISO 2009 SWID Tags using
Using XML

Any record associated with this Software Data Model Type MUST conform
to the ISO/IEC 19770-2-2009 [SWID09] specification. [SWID09]. Any such tag SHOULD use a UTF-8 encoding [RFC3629], [RFC3629] but
MUST NOT alter the existing encoding if doing so would invalidate
digital signatures included in the tag.

If generating a new ISO 2009 SWID tag, the software generating the
tag MUST use a Tag Creator RegID that is associated with the
generating software software, unless this is impossible, in which case it MUST
use "unknown", which indicates that the Tag Creator tag creator is unknown.
(This conforms to conventions for an unknown Tag Creator tag creator in the
ISO 2009 SWID tag specification.) Do not use a RegID associated with
any other party. In particular, it is incorrect to use a Tag Creator
RegID associated with the software being described by the tag, the
enterprise that is using the software, or any other entity except
that of the party that built the tool that is generating the SWID
tag. This reflects the requirement that the Tag Creator RegID
identify the party that created the tag.

6.2.2. Guidance on Creation of Software Identifiers from ISO 2009
SWID Tags

A Software Identifier generated from an ISO 2009 SWID tag is
expressed as a concatenation of the value of the Tag Creator RegID
field and the Unique ID field. Specifically, (1) it MUST be of the form:
form TAG_CREATOR_REGID "_" "_" UNIQUE_ID. Specifically, the Software
Identifier UNIQUE_ID and (2) it consists of, of the
Tag Creator RegID and the Unique ID from the tag connected with a
double underscore (_), without any other connecting character or
whitespace.

7. Relationship to Other Specifications

This specification is expected to participate in a standard NEA
architecture. As such, it is expected to be used in conjunction with
the other protocols used in a NEA exchange. In particular, SWIMA
Attributes
attributes are conveyed over PB-TNC [RFC5793], which is in turn
conveyed over some variant of PT (either PT-TLS [RFC6876] or PT-EAP
[RFC7171]). These protocols have an especially important role, as
they are responsible for ensuring that attributes defined under this
specification are delivered reliably, securely, and to the
appropriate party.

It is important to note that the Product Information, Numeric
Version, and String Version attributes defined in the PA-TNC
specification [RFC5792] are also meant to convey information about
installed applications and the versions thereof. As such, there is
some conceptual overlap between those attributes and the intent of
this specification. However, PA-TNC was designed to respond to very
specific queries about specific classes of products, while the SWIMA
specification is
able to convey a broader query, resulting in a more comprehensive set
of evidence information regarding an endpoint's installed software. As such,
this specification provides important capabilities not present in the
PA-TNC specification.

The NEA architecture is intended to support a broad range of
activities and, as such, might be employed by other specifications.
For example, requirement T-001 in the SACM Requirements document
[RFC8248] notes that NEA can support data collection from endpoints
within the broader SACM architecture. (Other parts of the NEA
architecture, which SWIMA uses, meet the other SACM data transport
requirements.) In the SACM architecture, a SWIMA-PV corresponds to a
"SACM Collector" and a SWIMA-PC corresponds to a "SACM Internal
Collector". In the SACM architecture, the SWIMA specification can support activities
relating to software inventory collection. Specifically, SWIMA
supports the SACM "Endpoint Posture Attribute Value Collection" use
case (section (Section 2.1.3 in [RFC7632]) by describing a collection
mechanism that enables event driven, event-driven, scheduled, and ad- ad hoc data
collection of software inventory information. SWIMA's flexibility
with regard to the format of inventory data records means that it is
compatible with virtually any data format that implements SACM's
"Define, Publish, Query, and Retrieve Security Automation Data" (section use
case (Section 2.1.1 in [RFC7632]). This is just one example of how
SWIMA can support broader security solution standards. Note that, that
while SWIMA can support these SACM use cases, SWIMA has no
dependencies upon on the SACM architecture or any other context in which
NEA might reasonably be applied.

8. Security Considerations

This section discusses some of the security threats facing Posture
Collectors SWIMA-PCs
and Posture Validators that implement the SWIMA protocol. SWIMA-PVs. This section primarily notes potential issues for
implementers to consider, although it does contain a handful of
normative requirements to address certain security issues. The
issues identified below focus on capabilities specific to this
document. Implementers are advised to consult other relevant NEA
specifications, particularly [RFC5209] (the NEA Architecture) architecture) and
[RFC5792] (PA-TNC), for security issues that are applicable to such
components in general.

8.1. Evidentiary Value of Software Inventory Evidence Records

The degree to which an endpoint's Software Inventory Evidence
Collection accurately reflects the endpoint's actual software load
and any changes made to this software load is dependent on the
accuracy of the tools used to populate and manage the software
inventory evidence records Software
Inventory Evidence Records in this collection. While the SWIMA-PC is
required to detect changes to an endpoint's Software Inventory
Evidence Collection in near real-time, real time, some tools might not be
designed to update records in the Software Inventory Evidence
Collection in real time. This can result in a collection that is
out-of-sync out
of sync with actual system state. Moreover, tools might inaccurately
characterize software, software or fail to properly record its removal.
Finally, it is likely that there will be software on the endpoint
that is not tracked by any source and thus is not reflected in the
Software Inventory Evidence Collection. Tools that implement SWIMA
ought to be aware of these potential issues and minimize them, but
completely eliminating such issues is likely impossible. Users of
collected software inventory evidence records Software Inventory Evidence Records need to understand that
the information provided by the SWIMA capability cannot be treated as completely
accurate. Nonetheless, having endpoints report this information can
still provide useful insights into the state of the endpoint's
software load, load and can alert administrators and policy tools of
situations that require remediation.

8.2. Sensitivity of Collected Records

Collected software records can be sensitive in nature. This can
include both security sensitivities and privacy sensitivities.
Privacy sensitivities are discussed more in Section 9. With regard
to security, inventory records represent a wealth of information
about the endpoint in question and, question, and for an adversary who does not
already have access to the endpoint, endpoint a collection of the endpoint's
inventory records might provide many details that are useful for
mounting an attack. A list of the inventory records associated with
an endpoint reveals a list of software installed on the endpoint.
This list can be very detailed, noting specific versions and even
patch levels, which levels; an adversary can use this information to identify
vulnerable software and design efficacious attacks.

In addition, other

The following information might also be gleaned from a collection of
software inventory records:

o An inventory record might include information about where the
product was installed on a given endpoint. This can reveal
details about the file organization of that endpoint that an
attacker can utilize.

o An inventory record might include information about how the
software was provided to the endpoint, who in an organization
signs off on the package release, and who packaged the product for
installation. This information might be used as a starting point
for the development of supply chain attacks.

o Events affecting inventory records are reported with timestamps
indicating when each given event occurred. This can give the
attacker an indication of how quickly an organization distributes
patches and updates, helping the attacker determine how long an
attack window might remain open.

Any consolidated software inventory is a potential risk, because such
an inventory can provide an adversary an insight into the
enterprise's configuration and management process. It is recommended
that a centralized software inventory record collection be protected
against unauthorized access. Mechanisms to accomplish this can
include encrypting the data at rest, ensuring that access to the data
is limited only to authorized individuals and processes, and other
basic security precautions.

8.3. Integrity of Endpoint Records

SWIMA-PCs maintain records of detected changes to the endpoint's
Software Inventory Evidence Collection. These records are used to
respond to a SWIMA-PV's request for change events. The SWIMA-PV
might use a list of reported events to update its understanding of
the endpoint's Software Inventory Evidence Collection without needing
to receive a full inventory report from the SWIMA-PC. For this
reason, preserving the integrity of the SWIMA-PC's record of events
is extremely important. If an attacker modifies the SWIMA-PC's
record of changes to the endpoint's Software Inventory Evidence
Collection, this might cause the SWIMA-PV's understanding of the
endpoint's Software Inventory Evidence Collection to differ from its
actual state. Results The results of such an attack might include leading
the SWIMA-PV to believe that (1) absent software was present, present or,
conversely, that present software was absent,
that absent or (2) patches have been
installed even if this is not the case, or case. Such an attack could also
cause the SWIMA-PV to be unaware of other changes to Software
Inventory Evidence Records. As such, the SWIMA-PC MUST take steps to
protect the integrity of its event records.

In addition, records of established SWIMA-PV subscriptions also
require protection against manipulation or corruption. If an
attacker is able to modify or delete records of an established
subscription by a SWIMA-PV, SWIMA-PV's
established subscription, the SWIMA-PC might fail to correctly
fulfill this subscription. The SWIMA-PV would not be aware that its
subscription was not being correctly fulfilled unless it received
additional information that indicated a discrepancy. For example,
the SWIMA-PV might collect a full inventory and realize from this
information that certain events had not been correctly reported in
accordance with an established subscription. For this reason, the
SWIMA-PC MUST protect the integrity of subscription records.

8.4. SWIMA-PC Access Permissions

A SWIMA-PC requires sufficient permissions to collect Software
Inventory Evidence Records from all of its supported sources, as well
as sufficient permissions to interact with the endpoint's Posture
Broker Client. With regard to the former, this might require
permissions to read the contents of directories throughout the file
system.
filesystem. Depending on the operating environment and other
activities undertaken by a SWIMA-PC (or software that incorporates a
SWIMA-PC as one of its capabilities) capabilities), additional permissions might be
required by the SWIMA-PC software. The SWIMA-PC SHOULD NOT be
granted permissions beyond what it needs in order to fulfill its duties.

8.5. Sanitization of Record Fields

Not all sources of software inventory evidence are necessarily
tightly controlled. For example, consider a source that gathers
.swid files from the endpoint's file system. filesystem. Any party could create a
new .swid file that could be collected and turned into a Software
Inventory Evidence Record. As a result, it is important that the
contents of source information not be automatically trusted. In
particular, tools that read source information and the Software
Inventory Evidence Records derived therefrom, including SWIMA-PCs,
need to be careful to sanitize input to prevent buffer overflow
attacks, encoding attacks, and other weaknesses that might be
exploited by an adversary who can control the contents of a record.

8.6. PA-TNC Security Threats

In addition to the aforementioned considerations considerations, the SWIMA protocol
is subject to the same security threats as other PA-TNC transactions,
as noted in transactions;
see Section 5.2 of PA-TNC [RFC5792]. These include, but are not
limited to, attribute theft, message fabrication, attribute
modification, attribute replay, attribute insertion, and denial of
service. Implementers are advised to consult the PA-TNC
specification to better understand these security issues.

9. Privacy Considerations

As noted in Section 8.2, if an adversary can gain an understanding of
the software installed on an endpoint, they can utilize this to
launch attacks and maintain footholds on this endpoint. For this
reason, the NEA Server needs to ensure that adequate safeguards are
in place to prevent exposure of collected inventory records. For
similar reasons, it is advisable that an endpoint only send records
to a NEA Server that is authorized to receive this information and
that can be trusted to safeguard this information after collection.

In addition, software inventory information can lead to insights
about the endpoint's primary user if that user is able to install
software. (Note that users might be "able" to install their own
software even if they are not "allowed" to do so.) This is
especially true on endpoints that support "apps", as individual apps
can be closely tied to specific groups or activities. This could
conceivably allow inferences about things such as a user's hobbies, hobbies;
the banks and other financial institutions that they use, use; and
information about the user's race, sex, or sexual orientation.

Organizations that collect software inventory information from
endpoints ought to make sure the endpoints' users are aware of this
collection. In addition, organizations should be aware that a
software inventory associated with an individual, such as the
inventory of the individual's primary endpoint, could expose
sensitive personal information. For this reason, privacy safeguards
are necessary for collected inventory information. Such safeguards
would require not only protection of the inventory's confidentiality, confidentiality
but also appropriate access controls so that only those trained in
relevant privacy requirements are able to view the data.

10. IANA Considerations

This section extends multiple existing IANA registries.
Specifically, it extends the PA-TNC "PA-TNC Attribute Types Types" and PA-TNC "PA-TNC
Error
Codes Codes" registries defined in the PA-TNC specification [RFC5792]
and the PA-
Subtypes "PA Subtypes" registry defined in the PB-TNC specification
[RFC5793] and extended in PA-TNC. This specification only adds
values to these registries and does not alter how these registries
work or are maintained. Consult the appropriate specifications for
details on the operations and maintenance of these registries.

This section also defines a new IANA registry for "Software Data
Model Types". The structure and requirements for this registry are
provided, as well as guidelines for reviewers adjudicating the
addition of new entries to this registry.

10.1. Guidance for the Designated Experts

For the "Software Data Model Types" registry defined by this
specification, new values are added to the registry using the
"Specification Required" process defined in RFC 8126 [RFC8126].

This section provides guidance to designated experts so that they may
make decisions using a philosophy appropriate for this registry.

Designated experts should focus on the following requirements. All
values in this IANA registry MUST be documented in a specification
that is permanently and publicly available. Values MUST also be
useful, not harmful to the Internet, and defined in a manner that is
clear and likely to ensure interoperability.

Designated experts should encourage vendors to avoid defining similar
but incompatible values and instead agree on a single value allocated
via IETF standards. However, it is beneficial to document existing
practice.

There are several ways to ensure that a specification is permanently
and publicly available. It may be published as an RFC.
Alternatively, it may be published in another manner that makes it
freely available to anyone. However, in this latter case, the vendor
MUST supply a copy to IANA and authorize IANA to archive this copy
and make it freely available to all, if at some point the document
becomes no longer freely available to all through other channels.

Sections 10.2, 10.3, and 10.4 define a new PA Subtype, new PA-TNC
Attribute Types, and new PA-TNC Error Codes, respectively.
Section 10.5 provides guidance to IANA in creating and managing the
new "Software Data Model Types" registry defined by this
specification.

10.2. PA Subtypes

The following is an extension to the list of PA Subtype registry [2] defined Subtypes provided in section
Section 7.2 of [RFC5792] and defined in the PA-TNC specification [RFC5792]. "PA Subtypes" registry in
Section 6.3 of [RFC5793]. See <https://www.iana.org/assignments/
pb-tnc-parameters/>.

+-----+---------+------------------+------------------------+
| PEN | Integer | Name | Defining Specification |
+-----+---------+------------------+------------------------+
| 0 | 9 | SWIMA Attributes | [RFC-to-be] RFC 8412 |
+-----+---------+------------------+------------------------+

10.2. Registry for

10.3. PA-TNC Attribute Types

Section 5.4 5.2 of this specification defines several new PA-TNC
attributes. The following values are have been added to the registry for PA-
TNC "PA-TNC
Attribute Types Types" registry defined in the PA-TNC specification. Note
that Table 1 in Section 5.4 5.2 lists these attributes but uses a in both
hexadecimal
value to identify their associated integer. and decimal format. The integer decimal values given in that
table are identical to those provided here. Note also that Table 1
includes an entry for the PA-TNC Error attributes, attribute, but the IANA
information associated with that the PA-TNC Error attribute is already
defined in the PA-TNC specification and is not reproduced here.

+-----+---------+----------------------------+----------------------+
| PEN | Integer | Name | Defining |
| | | | Specification |
+-----+---------+----------------------------+----------------------+
| 0 | 13 | SWIMA Request | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 14 | Software Identifier | [RFC-to-be] RFC 8412 |
| | | Inventory | |
| | | | |
| 0 | 15 | Software Identifier Events | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 16 | Software Inventory | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 17 | Software Events | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 18 | Subscription Status | [RFC-to-be] RFC 8412 |
| | | Request | |
| | | | |
| 0 | 19 | Subscription Status | [RFC-to-be] RFC 8412 |
| | | Response | |
| | | | |
| 0 | 20 | Source Metadata Request | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 21 | Source Metadata Response | [RFC-to-be] RFC 8412 |
+-----+---------+----------------------------+----------------------+

10.3. Registry for

10.4. PA-TNC Error Codes

Section 5.16 5.15 of this specification defines several new PA-TNC Error
Codes. The following values are have been added to the registry for PA-TNC "PA-TNC Error Codes
Codes" registry defined in the PA-TNC specification. Note that
Table 8 9 in Section 5.16 5.15 lists these codes but uses a in both hexadecimal value to
identify their associated integer. and
decimal format. The integer decimal values given in that table are identical
to those provided here.

+----+--------+-------------------------------------+---------------+

+-----+---------+--------------------------------------+---------------+
| PE PEN | Intege Integer | Name | Defining |
| N | r | | Specification |
+----+--------+-------------------------------------+---------------+
+-----+---------+--------------------------------------+---------------+
| 0 | 4 | SWIMA_ERROR | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 5 | SWIMA_SUBSCRIPTION_DENIED_ERROR | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 6 | SWIMA_RESPONSE_TOO_LARGE_ERROR | [RFC-to-be] RFC 8412 |
| | | | |
| 0 | 7 | SWIMA_SUBSCRIPTION_FULFILLMENT_ERRO | [RFC-to-be] |
| | | R SWIMA_SUBSCRIPTION_FULFILLMENT_ERROR | RFC 8412 |
| | | | |
| 0 | 8 | SWIMA_SUBSCRIPTION_ID_REUSE_ERROR | [RFC-to-be] RFC 8412 |
+----+--------+-------------------------------------+---------------+

10.4. Registry for
+-----+---------+--------------------------------------+---------------+

10.5. Software Data Models

The name for this registry is Model Types

For the "Software Data Model Types". Each
entry in this Types" registry
(<https://www.iana.org/assignments/pa-tnc-parameters/
#software-data-model-types>, each entry should include a human readable
human-readable name, an SMI
Private Enterprise Number, PEN, a decimal integer value between 1 0
and 2^8-1 (inclusive), and a reference to the specification where the
use of this data model is defined. This referenced specification
needs to provide both a description of the format used by the data
model and the procedures by which Software Identifiers are derived
from a record expressed using this data model. Note that a
specification that just defines the data model structure and its use
is generally not
sufficient sufficient, as it would likely lack the procedures
for constructing a Software Identifier. This is why the table below references
uses the
current specification SWIMA standard for ISO SWID tags, rather than using tags as the reference for the
use of ISO SWID tags and does not reference the actual ISO SWID tag
specification.

The following entries for this registry are defined in this document.
They are the initial entries in the registry for Software "Software Data Model
Types. Types"
registry. Additional entries to this registry are added by Expert
Review with Specification Required, following
the "Specification Required" policy defined in [RFC8126], following
the guidelines in
[RFC8126]. Section 10.1.

+-----+---------+-----------------------------+---------------------+
| PEN | Integer | Name | Defining |
| | | | Specification |
+-----+---------+-----------------------------+---------------------+
| 0 | 0 | ISO 2015 SWID Tags tags using | [RFC-to-be] RFC 8412 |
| | | XML | |
| | | | |
| 0 | 1 | ISO 2009 SWID Tags tags using | [RFC-to-be] RFC 8412 |
| | | XML | |
| | | | |
| 0 | 192-255 | Reserved for local | N/A |
| | | enterprise use | |
+-----+---------+-----------------------------+---------------------+

11. References

11.1. Normative References

[NIST8060]
Waltermire, D., Cheikes, B., Feldman, L., and G. Witte,
"Guidelines for the Creation of Interoperable Software
Identification (SWID) Tags", DOI 10.6028/NIST.IR.8060,
April 2016. 2016, <https://nvlpubs.nist.gov/nistpubs/ir/2016/
NIST.IR.8060.pdf>.

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

[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.

[RFC3629] Yergeau, F., "UTF-8, a transformation format of
ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629,
November 2003, <https://www.rfc-editor.org/info/rfc3629>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.

[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<https://www.rfc-editor.org/info/rfc5198>.

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

[RFC8089] Kerwin, M., "The "file" URI Scheme", RFC 8089,
DOI 10.17487/RFC8089, February 2017,
<https://www.rfc-editor.org/info/rfc8089>.

[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.

[SWID09] The International Organization for Standardization/
International Electrotechnical Commission, "Information
Technology
technology - Software Asset Management asset management - Part 2: Software
Identification Tag,
identification tag", ISO/IEC 19770-2", 19770-2:2009, November 2009. 2009,
<https://www.iso.org/standard/53670.html>.

[SWID15] The International Organization for Standardization/
International Electrotechnical Commission, "Information
Technology
technology - Software Asset Management asset management - Part 2: Software
Identification Tag,
identification tag", ISO/IEC 19770-2", 19770-2:2015, October 2015. 2015,
<https://www.iso.org/standard/65666.html>.

11.2. Informative References

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

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

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

[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,
<https://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,
<https://www.rfc-editor.org/info/rfc7632>.

[RFC8248] Cam-Winget, N. and L. Lorenzin, "Security Automation and
Continuous Monitoring (SACM) Requirements", RFC 8248,
DOI 10.17487/RFC8248, September 2017,
<https://www.rfc-editor.org/info/rfc8248>.

11.3. URIs

[1] https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml

[2] https://www.iana.org/assignments/pb-tnc-parameters/pb-tnc-
parameters.xhtml#pb-tnc-parameters-2

Authors' Addresses

Charles Schmidt
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730
USA
United States of America

Email: cmschmidt@mitre.org

Daniel Haynes
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730
USA
United States of America

Email: dhaynes@mitre.org

Chris Coffin
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730
USA
United States of America

Email: ccoffin@mitre.org

David Waltermire
National Institute of Standards and Technology
100 Bureau Drive
Gaithersburg, Maryland
USA
United States of America

Email: david.waltermire@nist.gov

Jessica Fitzgerald-McKay
United States National Security Agency
9800 Savage Road
Ft. Meade, Maryland
USA
United States of America

Email: jmfitz2@radium.ncsc.mil