Internet DRAFT - draft-coffin-sacm-nea-swid-patnc
draft-coffin-sacm-nea-swid-patnc
SACM C. Coffin
Internet-Draft D. Haynes
Intended status: Standards Track C. Schmidt
Expires: September 8, 2016 The MITRE Corporation
J. Fitzgerald-McKay
Department of Defense
March 7, 2016
SWID Message and Attributes for PA-TNC
draft-coffin-sacm-nea-swid-patnc-00
Abstract
This document specifies the SWID Message and Attributes for PA-TNC.
It extends the PA-TNC specification [RFC5792] by providing specific
attributes and message exchanges to allow endpoints to report their
software inventory information to a NEA server (as described in
[RFC5209]) using SWID tags [SWID].
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Scope and Audience . . . . . . . . . . . . . . . . . . . 4
1.2. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 7
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Role of SWID Message and Attributes for PA-TNC . . . . . 8
2.2. Supported Use Cases . . . . . . . . . . . . . . . . . . . 9
2.2.1. Use Software Inventory as a Factor in Determining
Endpoint Access . . . . . . . . . . . . . . . . . . . 9
2.2.2. Maintain a Central Repository Reflecting an
Endpoint's Software Inventory . . . . . . . . . . . . 10
2.2.3. PA-TNC Use Cases . . . . . . . . . . . . . . . . . . 10
2.3. Non-supported Use Cases . . . . . . . . . . . . . . . . . 11
2.4. Specification Requirements . . . . . . . . . . . . . . . 12
2.5. Non-Requirements . . . . . . . . . . . . . . . . . . . . 13
2.6. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 13
2.7. Non-Assumptions . . . . . . . . . . . . . . . . . . . . . 14
2.8. Caveat Regarding Persistent Connections . . . . . . . . . 14
2.9. SWID Message and Attributes for PA-TNC Diagram
Conventions . . . . . . . . . . . . . . . . . . . . . . . 15
3. SWID Message and Attributes for PA-TNC System Requirements . 15
3.1. SWID Tags as Inventory Evidence . . . . . . . . . . . . . 16
3.2. Basic SWID Tag Inventory Exchange . . . . . . . . . . . . 16
3.3. SWID Tag Identifiers . . . . . . . . . . . . . . . . . . 17
3.3.1. Tag Identifier Data . . . . . . . . . . . . . . . . . 18
3.3.2. Tag Identifier Instances . . . . . . . . . . . . . . 19
3.3.3. Comparing Tag Identifiers and Tag Identifier
Instances . . . . . . . . . . . . . . . . . . . . . . 20
3.3.3.1. Matching Tag Identifiers Indicate the Same
Software Product . . . . . . . . . . . . . . . . 21
3.3.3.2. Matching Tag Identifiers DO NOT Necessarily
Indicate Identical Tag Files . . . . . . . . . . 21
3.3.3.3. Matching Tag Identifier Instances MIGHT Indicate
Identical Tag Files . . . . . . . . . . . . . . . 22
3.3.3.4. Differing Tag Identifiers DO NOT Necessarily
Indicate Different Software Products . . . . . . 22
3.3.4. Using Tag Identifiers in SWID Attributes . . . . . . 23
3.4. Targeted Requests . . . . . . . . . . . . . . . . . . . . 23
3.5. Monitoring Changes in an Endpoint's SWID Tag Collection . 24
3.6. Reporting Change Events . . . . . . . . . . . . . . . . . 26
3.6.1. Change Event Records . . . . . . . . . . . . . . . . 27
3.6.2. Updating Inventory Knowledge Based on Events . . . . 28
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3.6.3. Using Event Records in SWID Attributes . . . . . . . 29
3.6.4. Partial and Complete Lists of Event Records in SWID
Attributes . . . . . . . . . . . . . . . . . . . . . 29
3.6.5. Synchronizing Event Identifiers and Epochs . . . . . 31
3.7. Supporting Multiple Instances of a Single Tag . . . . . . 33
3.7.1. Inventory Reporting in the Presence of Multiply-
Instantiated Tags . . . . . . . . . . . . . . . . . . 33
3.7.2. Event Reporting in the Presence of Multiply
Instantiated Tags . . . . . . . . . . . . . . . . . . 33
3.8. Subscriptions . . . . . . . . . . . . . . . . . . . . . . 34
3.8.1. Establishing Subscriptions . . . . . . . . . . . . . 34
3.8.2. Managing Subscriptions . . . . . . . . . . . . . . . 35
3.8.3. Terminating Subscriptions . . . . . . . . . . . . . . 35
3.8.4. Subscription Status . . . . . . . . . . . . . . . . . 36
3.8.5. Fulfilling Subscriptions . . . . . . . . . . . . . . 37
3.8.5.1. Subscriptions Reporting Inventories . . . . . . . 39
3.8.5.2. Subscriptions Reporting Events . . . . . . . . . 39
3.8.5.3. Targeted Subscriptions . . . . . . . . . . . . . 40
3.8.5.4. No Subscription Consolidation . . . . . . . . . . 41
3.8.5.5. Delayed Subscription Fulfillment . . . . . . . . 41
3.9. Multiple Sources of SWID Tags . . . . . . . . . . . . . . 42
3.10. Error Handling . . . . . . . . . . . . . . . . . . . . . 43
4. SWID Message and Attributes for PA-TNC Protocol . . . . . . . 45
4.1. PA Subtype (AKA PA-TNC Component Type) . . . . . . . . . 45
4.2. PB-TNC and PA-TNC Messages . . . . . . . . . . . . . . . 46
4.3. PA-TNC Attribute Header . . . . . . . . . . . . . . . . . 46
4.4. SWID Attribute Overview . . . . . . . . . . . . . . . . . 47
4.5. SWID Attribute Exchanges . . . . . . . . . . . . . . . . 49
4.6. SWID Message and Attributes for PA-TNC Attribute
Enumeration . . . . . . . . . . . . . . . . . . . . . . . 51
4.7. Normalization of Text Encoding . . . . . . . . . . . . . 52
4.8. Request IDs . . . . . . . . . . . . . . . . . . . . . . . 53
4.9. SWID Request . . . . . . . . . . . . . . . . . . . . . . 54
4.10. SWID Tag Identifier Inventory . . . . . . . . . . . . . . 58
4.11. SWID Tag Identifier Events . . . . . . . . . . . . . . . 61
4.12. SWID Tag Inventory . . . . . . . . . . . . . . . . . . . 66
4.13. SWID Tag Events . . . . . . . . . . . . . . . . . . . . . 68
4.14. Subscription Status Request . . . . . . . . . . . . . . . 72
4.15. Subscription Status Response . . . . . . . . . . . . . . 72
4.16. PA-TNC Error as Used by SWID Message and Attributes for
PA-TNC . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.16.1. SWID_ERROR, SWID_SUBSCRIPTION_DENIED_ERROR
and SWID_SUBSCRIPTION_ID_REUSE_ERROR
Information . . . . . . . . . . . . . . . . . . . . 76
4.16.2. SWID_RESPONSE_TOO_LARGE_ERROR Information . . . . . 77
4.16.3. SWID_SUBSCRIPTION_FULFILLMENT_ERROR Information . . 79
5. Security Considerations . . . . . . . . . . . . . . . . . . . 80
5.1. Evidentiary Value of SWID Tags . . . . . . . . . . . . . 81
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5.2. Integrity of the SWID Tag Collection . . . . . . . . . . 81
5.3. Sensitivity of Collected Tags . . . . . . . . . . . . . . 82
5.4. Integrity of Endpoint Records . . . . . . . . . . . . . . 83
5.5. SWID-PC Access Permissions . . . . . . . . . . . . . . . 84
5.6. Sanitization of Tag Fields . . . . . . . . . . . . . . . 84
5.7. Tag Library Poisoning . . . . . . . . . . . . . . . . . . 85
5.8. PA-TNC Security Threats . . . . . . . . . . . . . . . . . 85
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 85
7. Relationship to Other Specifications . . . . . . . . . . . . 86
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 86
8.1. Registry for PA-TNC Attribute Types . . . . . . . . . . . 87
8.2. Registry for PA-TNC Error Codes . . . . . . . . . . . . . 87
8.3. Registry for PA Subtypes . . . . . . . . . . . . . . . . 88
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 88
9.1. Normative References . . . . . . . . . . . . . . . . . . 89
9.2. Informative References . . . . . . . . . . . . . . . . . 89
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 90
A.1. A Simple SWID Tag . . . . . . . . . . . . . . . . . . . . 90
A.2. SWID Request Attributes . . . . . . . . . . . . . . . . . 92
A.2.1. Simple Request . . . . . . . . . . . . . . . . . . . 92
A.2.2. Subscription Request for Events . . . . . . . . . . . 93
A.2.3. Targeted Request . . . . . . . . . . . . . . . . . . 93
A.3. SWID Response Attributes . . . . . . . . . . . . . . . . 95
A.3.1. SWID Tag Identifier Events Attribute . . . . . . . . 95
A.3.2. SWID Tag Inventory Attribute . . . . . . . . . . . . 97
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 98
1. Introduction
1.1. Scope and Audience
The Network Endpoint Assessment (NEA) Working Group defines 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, monitor endpoint health,
and for many other activities. Information about the software
present on an endpoint is an important consideration for such
activities. Software Identification tags (SWID tags) [SWID] are
formatted records (usually XML documents) that identify a specific
software product. In this case, a "software product" can be a
distinct release of some piece of software, such as an operating
system, web browser, etc.; a patch or plug-in for such an
application; or a suite of such applications. The SWID specification
describes the format of these documents as well as rules governing
their use on computer systems. In particular, software that supports
SWID tags is expected to deposit an identifying tag on the endpoint
when the software is installed, modify or replace the tag as the
software is updated, and delete the tag when the software is
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uninstalled. SWID tags can also be created and managed by third-
party tools or by local enterprises, allowing for tags to indicate
the presence of software even when that software's manufacturer has
not included SWID support. As such, by collecting a list of tags on
an endpoint, one receives evidence as to the software present on that
endpoint. The attributes defined in this document are used to
communicate software inventory evidence, in the form of SWID tags,
between the posture collector and posture validator using the PA-TNC
interface, as shown in Figure 1 below.
+-------------+ +--------------+
| Posture | <--------PA--------> | Posture |
| Collectors | | Validators |
| (1 .. N) | | (1 .. N) |
+-------------+ +--------------+
| |
| IF-IMC | IF-IMV
| |
+-------------+ +--------------+
| 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
The use of standard protocols and formats for conveying evidence
about endpoint state (in this case, endpoint inventory information)
has a number of benefits. The use of standard protocols and formats
facilitates interoperability between products developed by different
vendors. This allows consumers to select the product that has
features that best fit with the needs of their environment, with the
expectation that it will be able to interoperate with other parts of
their infrastructure (at least with regard to the aforementioned
protocols and formats). In addition, because a standard is expected
to be implemented by multiple independent parties, this means that
the standard protocols and formats receive more review than might be
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expected in a proprietary solution. When the standard is managed by
a group that is responsive to feedback from such implementers, as is
the case with the IETF, this can lead to improvements in efficiency
and security of those protocols and formats. For these reasons, a
standard means of conveying endpoint inventory information such as
the one described in this document provides significant value to
users. Vendors benefit from utilizing SWIDs to serve as evidence of
software inventory because it reduces their need to develop remote
software inventory tools for the increasing variety of endpoint
platforms. If those endpoints support SWID Message and Attributes
for PA-TNC, vendors can use these protocols to gather software
inventory information remotely.
This specification defines a new set of PA-TNC attributes, carried
over PA-TNC messages, which are used to communicate requests for SWID
tags and events surrounding those tags, and for conveying that
information back to a NEA Server.
Possession of a list of an endpoint's SWID tags is very useful in
understanding and maintaining the security state of an enterprise.
For example, if an enterprise policy requires the presence of certain
pieces of software and/or prohibits the presence of other software,
SWID tags can be used to indicate compliance or non-compliance with
these requirements. SWID tags indicating software presence and the
patch level of that software can be compared to vulnerability or
threat alerts to determine an endpoint's exposure to attack. SWID
tags provide a great deal of information about unfamiliar software
products, including the software author and potentially including
where the software is installed on the endpoint and what files on the
endpoint are associated with this installed software. All of these
uses make an understanding of an endpoint's SWID tag collection
highly useful to NEA Servers and other enterprise security
applications.
Before reading this specification any further, the reader should
review and understand the NEA reference architecture as described in
the Network Endpoint Assessment (NEA): Overview and Requirements
[RFC5209]. The reader should also understand the capabilities and
requirements common to PA-TNC interfaces as defined in RFC 5792
[RFC5792].
In addition, this document relies upon features in the Trusted
Computing Group's Trusted Network Communications (TNC) IF-IMC 1.3
[IF-IMC] and IF-IMV 1.4 [IF-IMV] specifications. These
specifications describe standard interfaces and requirements for the
interoperation between TNC IMCs and TNC Clients, and between TNC IMVs
and TNC Servers. The TNC and NEA architectures are interoperable and
the following components are equivalent:
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+---------------------------------------+-----------------------+
| TNC Component | NEA Component |
+---------------------------------------+-----------------------+
| Integrity Measurement Verifier (IMV) | Posture Validator |
| Integrity Measurement Collector (IMC) | Posture Collector |
| TNC Server (TNCS) | Posture Broker Server |
| TNC Client (TNCC) | Posture Broker Client |
+---------------------------------------+-----------------------+
Table 1: Equivalent components in TNC and NEA architectures
As a result, the IF-IMC specification effectively standardizes an
interface between a Posture Collector and the Posture Broker Client,
while the IF-IMV specification effectively standardize an interface
between a Posture Validator and a Posture Broker Server. However, as
there is currently no NEA equivalent for IF-IMC or IF-IMV, the names
for these specifications as well as the names of functions and data
structures that appear in those specifications uses TNC rather than
NEA terminology. Readers should be aware of the functional
equivalence of the TNC and NEA terms.
If the reader is building a posture collector that supports PA-TNC,
the reader is encouraged to read the TNC IF-IMC Specification prior
to reading this specification. If the reader is building a posture
validator that supports IF-IMV, the reader is encouraged to read the
TNC IF-IMV Specification prior to reading this specification.
1.2. Keywords
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
specification are to be interpreted as described in RFC 2119
[RFC2119]. This specification does not distinguish blocks of
informative comments and normative requirements. Therefore, for the
sake of clarity, note that lower case instances of must, should, etc.
do not indicate normative requirements.
1.3. Definitions
This section defines terms with special meaning within this document.
SWID-PC - A Posture Collector (PC) that conforms to this
specification. Note that such a posture collector might also support
other PA-TNC exchanges beyond SWID Message and Attributes for PA-TNC.
SWID-PV - A Posture Validator (PV) that conforms to this
specification. Note that such a posture verifier might also support
other PA-TNC exchanges beyond SWID Message and Attributes for PA-TNC.
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Endpoint's SWID Tag Collection - The set of SWID tags installed and
managed on an endpoint for software installed on that endpoint. An
endpoint's SWID tag collection might include SWID tags from multiple
sources, including but not limited to SWID tag files deposited on the
file system during software installation, SWID tags generated to
report output from software discovery tools, and SWID tags
dynamically generated by a software or package management system on
an endpoint.
2. Background
2.1. Role of SWID Message and Attributes for PA-TNC
The International Organization for Standardization and the
International Electrotechnical Commission (ISO/IEC) published the
specification governing SWID tag construction and use in 2009.
[SWID] Since that time, a growing number of vendors have integrated
SWID tags into their software products. Doing so significantly
simplifies 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 readily available list of SWID tags provides simple and immediate
evidence as to the presence of the given piece of software.
SWID tags can also be useful even when a piece of software does not
supply the tags itself. Discovery processes are permitted to express
their findings using SWID tags, place these in the endpoint's SWID
tag collection, and maintain them like vendor-created SWID tags.
This means that an endpoint's SWID tag collection is not necessarily
limited to containing SWID tags for software whose authors have taken
the time to integrate SWID maintenance into their installation and
update processes. Similarly, software and package managers on an
endpoint (such as RPM and YUM) keep records of installed software,
and these records can be exported as a series of SWID tags, allowing
these managers to expose their information about software inventories
in a standards-based manner. Finally, for organizations that
centrally manage the distribution of software, in-house-developed
SWID tags can be added to any software product that does not natively
support SWID tags allowing the organization to accurately identify
any software it has distributed.
The NEA Server needs access to this inventory evidence if it is to
use this information to assess endpoint compliance with policy. The
SWID Message and Attributes for PA-TNC specification has been created
for this purpose. Specifically, the attributes defined in this
specification allow a Posture Validator to request evidence of an
endpoint's inventory in the form of SWID tags and allow the Posture
Collector to respond with the appropriate information.
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It is not necessary to understand the details of SWID tag
construction and maintenance to understand the behaviors described in
the SWID Message and Attributes for PA-TNC specification, and it is
beyond the scope of this specification to discuss the details of the
SWID standard. Implementers, however, will likely need to be
familiar with the SWID tag format and how to locate tags on an
endpoint. The SWID specification is available from ISO/IEC at
http://www.iso.org/iso/catalogue_detail.htm?csnumber=53670. The XML
schema for a SWID tag file is available from ISO:
http://standards.iso.org/iso/19770/-2/2009/schema.xsd. The most
current working and production versions of the XML schema for SWID
tags can be found in the directory listing at
http://standards.iso.org/iso/19770/-2/. The US National Institute of
Standards and Technology (NIST) also has published guidelines for
SWID tag creation, which provide further guidance for those
interested in the use and best practices surrounding SWID tags.
[NIST-SWID]
2.2. Supported Use Cases
This section describes the SWID Message and Attributes for PA-TNC use
cases supported by this specification. The primary use of exchanging
SWID tag information over the PA-TNC interface is to enable a
challenger (e.g. NEA Server) to obtain inventory evidence about some
system in a way that conforms to NEA procedures while taking
advantage of the simplicity and precision of SWID tags. Collected
SWID tags can support a range of security activities including
determining whether an endpoint is permitted to connect to the
enterprise, determining which endpoints contain software that
requires patching, and similar activities.
2.2.1. Use Software Inventory as a Factor in Determining Endpoint
Access
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
by endpoints that have certain prohibited pieces of software
installed, such as applications that pose known security risks. To
support such policies, the NEA Server needs to collect evidence
indicating the software inventory of an endpoint that is seeking to
initiate or continue connectivity to the enterprise.
SWID Message and Attributes for PA-TNC facilitates policy decisions
that consider an endpoint's software inventory by providing the NEA
Server with a list of the SWID tags in the endpoint's SWID tag
collection. The tags in this collection serve as evidence as to the
endpoint's installed software. The SWID-PC can provide a complete or
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partial list of tags to the SWID-PV as required to determine policy
compliance. The SWID-PV can then use this as evidence of compliance
or non-compliance with enterprise policy.
2.2.2. Maintain a Central Repository Reflecting an Endpoint's Software
Inventory
Many tools can use information about an endpoint's software inventory
to monitor and enforce the security of an enterprise. For example, a
software patching service can use an endpoint's software inventory to
determine whether certain endpoints have software that requires
patching. A vulnerability management tool might identify endpoints
with known vulnerabilities (patched or otherwise) and use this to
gauge enterprise exposure to attack. A license management tool might
verify that all copies of a particular piece of software are
accounted for within the enterprise. The presence of a central
repository representing a real-time understanding of each endpoint's
software inventory facilitates all such activities. Using a central
repository that can ensure the freshness of its collected information
is generally more efficient than having each tool collect the same
inventory information from each endpoint individually and leads to a
more consistent understanding of enterprise state.
SWID Message and Attributes for PA-TNC supports this activity through
a number of mechanisms. As noted above, it allows a SWID-PC to
provide a complete list of the tags present in an endpoint's SWID tag
collection to the SWID-PV, which can then pass this information on to
a central repository such as a Configuration Management Database
(CMDB) or similar application. In addition, SWID-PCs are required to
be able to monitor for changes to an endpoint's SWID tag collection
in near real-time and push reports of changes to the SWID-PV as soon
as those changes are detected. Thus any central repository fed by a
SWID-PV receiving such information can be updated soon after the
change occurs. Keeping such a central repository synchronized with
the state of each endpoint's SWID tag collection allows tools that
use this information for their own security activities to make
decisions in a consistent, efficient manner.
2.2.3. PA-TNC Use Cases
SWID Message and Attributes for PA-TNC are intended to operate over
the PA-TNC interface and, as such, are intended to meet the use cases
set out in the PA-TNC specification.
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2.3. Non-supported Use Cases
Some use cases not covered by this version of SWID Message and
Attributes for PA-TNC include:
o This specification does not address how the endpoint's SWID tag
collection is populated. In particular, NEA components are not
expected to perform software discovery activities beyond compiling
the tags in an endpoint's SWID tag collection. This collection
might potentially come from multiple sources on the endpoint
(e.g., SWID tags generated dynamically by package management tools
or discovery tools, as well as SWID tag files discovered on the
file system). While an enterprise might make use of software
discovery procedures to identify installed software, especially
software that does not install or manage its own SWID tag, such
procedures are outside the scope of this specification.
o This specification does not address converting inventory
information expressed in a proprietary format into the SWID tag
format or converting a SWID tag into a proprietary format.
Instead, it focuses exclusively on defining interfaces for the
transportation of SWID tags in the expectation that this is the
format around which reporting tools will converge.
o This specification provides no mechanisms for a posture validator
to request a specific list of tags based on arbitrary tag
properties from the endpoint. For example, requesting only tags
representing software from a particular vendor is not supported.
After the endpoint's SWID tag 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 SWID tags,
but this specification does not address using such queries to
constrain the initial collection of this information from the
endpoint.
o This specification does not address utilization of certain SWID
tag fields designed to facilitate local tests (i.e., on the
endpoint) of endpoint state. For example, the optional
package_footprint field of a 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. Future
versions of this specification might add support for such testing.
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2.4. Specification Requirements
Below are the requirements that the SWID Message and Attributes for
PA-TNC specification is required to meet in order to successfully
play its role in the NEA architecture.
o Efficient
The NEA architecture enables delay of network access until the
endpoint is determined not to pose a security threat to the network
based on its asserted integrity information. To minimize user
frustration, the SWID Message and Attributes for PA-TNC ought to
minimize overhead delays and make PA-TNC communications as rapid and
efficient as possible.
Efficiency is also important when one considers that some network
endpoints are small and low powered, some networks are low bandwidth
and/or high latency, and some transport protocols (such as PT-EAP,
Posture Transport (PT) Protocol for Extensible Authentication
Protocol (EAP) Tunnel Methods [RFC7171]) or their underlying carrier
protocol might allow only one packet in flight at a time or only one
roundtrip. However, when the underlying PT protocol imposes fewer
constraints on communications, this protocol ought to be capable of
taking advantage of more robust communication channels (e.g. using
larger messages or multiple roundtrips).
o Loosely Coupled to the SWID Specification
Because the SWID specification is managed by ISO/IEC, the IETF has no
direct influence over this specification or any revisions made to it.
For this reason, the SWID Message and Attributes for PA-TNC
specification ought to minimize its requirements and assumptions with
regard to the structure and content of the SWID tags. While some
level of visibility into tag contents is required for certain
features of this specification, minimization of such dependencies is
necessary to improve compatibility with future revisions of the SWID
specification.
o Scalable
SWID Message and Attributes for PA-TNC 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.
o Interoperable
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This specification defines the protocol for how PCs and PVs can
exchange and use SWID tags to provide a NEA Server with information
about an endpoint's software inventory. Therefore a key goal for
this specification is ensuring that all SWID PCs and PVs, regardless
of the vendor who created them, are able to interoperate in their
performance of these duties.
o Support precise and complete historical reporting
This specification is expected to outline capabilities that support
real-time understanding of the state of endpoint in a network in a
way that can be used by other tools. One means of facilitating such
an outcome is for a Configuration Management Database (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 be able to report any changes to its SWID tag collection in
near real-time while connected and, upon reconnection to the
enterprise, be able to update the NEA Server (and through it the
CMDB) with regard to the state of its SWID tag collection throughout
the entire interval when it was not connected.
2.5. Non-Requirements
There are certain requirements that the SWID Message and Attributes
for PA-TNC specification explicitly is not required to meet. This
list is not exhaustive.
o End to End Confidentiality
SWID tags have no inherent mechanism for confidentiality, nor is this
property automatically provided by PA-TNC interface use.
Confidentiality is generally provided by the underlying transport
protocols, such as the PT Binding to TLS [RFC6876] or PT-EAP Posture
Transport for Tunneled EAP Methods [RFC7171] - see Section 7 for more
information on related standards. Should users wish confidentiality
protection of assessment instructions or results, this needs to be
provided by parts of the NEA architecture other than this
specification.
2.6. Assumptions
Here are the assumptions that SWID Message and Attributes for PA-TNC
makes about other components in the NEA architecture.
o Reliable Message Delivery
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The Posture Broker Client and Posture Broker Server are assumed to
provide reliable delivery for PA-TNC messages and therefore the SWID
Attributes sent between the SWID PCs and the PVs. In the event that
reliable delivery cannot be provided, the Posture Collector or
Posture Validator is expected to terminate the connection.
2.7. Non-Assumptions
The SWID Message and Attributes for PA-TNC specification explicitly
does not assume:
o Authenticity and Accuracy of SWID tags with Regard to Endpoint
Inventory
This specification makes no assumption as to whether the SWID tags
that it reports are authentic tags (rather than maliciously
generated) or that these tags correctly reflect software state on 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
existing SWID tags to the NEA Server. Similarly, this specification
makes no assumption with regard to the completeness of the SWID tag
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 tag in an endpoints SWID tag
collection. See Section 5 for more on this security consideration.
2.8. Caveat Regarding Persistent Connections
One of the features defined in this specification describes the
ability for SWID-PCs to monitor the state of their endpoint's SWID
tag collection and, when changes are detected, to push updates to the
SWID-PV without the SWID-PV sending a request. (This feature is
described in more detail in Section 3.8.) This capability is tied to
the SWID-PC's ability to initiate an Integrity Check Handshake (as
described in section 2.10.1 of the IF-IMC 1.3 specification
[IF-IMC]), which in turn is only possible if there is an active
connection with a valid connection ID (as described in section 2.10.2
of the IF-IMC 1.3 specification).
The other specifications of the NEA architecture do not require
endpoints to maintain active connections outside of an Integrity
Check Handshake. While implementers are allowed to maintain
connections outside of an Integrity Check Handshake (and there are
advantages to doing so), maintaining open connections also consumes
resources on both the endpoint and the NEA Server, so some
implementers may choose to close connections as soon as a handshake
completes. Moreover, for devices with intermittent connectivity
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(such as mobile phones), maintaining an active, ongoing connection
may be impractical.
This specification requires that all SWID-PCs and SWID-PVs support
subscriptions. However, for the reasons noted above, subscriptions
may not be practical in all environments where SWID-PCs and SWID-PVs
are deployed. Parties deploying SWID-PCs and SWID-PVs as part of
their enterprise protection strategy are encouraged to understand the
limits of specific devices and their NEA architecture as a whole. In
some cases, while other features of the SWID Message and Attributes
for PA-TNC specification may be employed, the use of subscriptions
may be limited or impractical without additional infrastructure
changes.
2.9. SWID Message and Attributes for PA-TNC Diagram Conventions
This specification defines the syntax of the SWID Message and
Attributes for PA-TNC using diagrams. Each diagram depicts the
format and size of each field in bits. Implementations MUST send the
bits in each diagram as they are shown from left to right for each
32-bit quantity traversing the diagram from top to bottom. Multi-
octet fields representing numeric values MUST be sent in network (big
endian) byte order.
Descriptions of bit fields (e.g. flags) 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).
3. SWID Message and Attributes for PA-TNC System Requirements
The SWID Message and Attributes for PA-TNC specification facilitates
the exchange of SWID tag inventories and event information.
Specifically, each application supporting SWID Message and Attributes
for PA-TNC includes a component known as the SWID-PC that receives
messages sent with the SWID Attributes component type. The SWID-PC
is also responsible for sending appropriate SWID Attributes back to
the SWID-PV in response. Similarly, the SWID-PV exists on a NEA
Server and is responsible for interpreting responses, forwarding
information to a CMDB if desired, and making policy decisions based
upon the received information. This section outlines what a SWID tag
inventory is, important features of tags used by this specification,
and the requirements on SWID-PCs and SWID-PVs in order to support the
stated use cases of this specification.
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3.1. SWID Tags as Inventory Evidence
As noted in Section 2.1, SWID tags are intended to be open, easily
accessible evidence indicating the presence of a particular piece of
software on an endpoint. A SWID tag contains multiple fields
intended to uniquely identify a single software product. Ideally, a
SWID tag is managed by the software that installs, modifies,
replaces, amends (e.g. patches, updates), and/or uninstalls the
product. Discovery processes, software package managers, and other
tools can also create and manage tags as a way to represent software
that they discover or manage on the endpoint.
It is important to note that, even in the ideal cases where a product
manages its own SWID tag, a tag is inherently distinct from the
product that it identifies. For this reason, a SWID tag needs to be
treated as evidence of software presence, but cannot be treated as
proof of software presence. That noted, a standardized
representation of evidence indicative of an endpoint's software
inventory is a powerful tool in managing software within an
enterprise.
3.2. Basic SWID Tag Inventory Exchange
In the most basic exchange supported by this specification, a SWID-PV
sends a request to the SWID-PC requesting a copy of all the SWID tags
in the endpoint's SWID tag collection. This simple exchange is shown
in Figure 2.
+-------------+ +--------------+
| SWID-PC | | SWID-PV | Time
+-------------+ +--------------+ |
| | |
|<-------------SWID Request---------------| |
| | |
|--------------SWID Response------------->| |
| | V
Figure 2: Basic SWID Message Exchange
Upon receiving such a SWID Request from the SWID-PV, the SWID-PC is
expected to locate the endpoint's SWID tags and then create copies of
all identified SWID tags and place them within its response
attribute.
SWID-PVs MUST discard without error any SWID Response attributes that
they receive for which they do not know the SWID Request parameters
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that led to this SWID Response. This is due to the fact that the
SWID Request includes parameters that control the nature of the
response (as will be described in the following sections) and without
knowing those parameters the SWID Response cannot be reliably
interpreted. Most often receiving an unsolicited SWID Response
attribute happens when a NEA Server has multiple SWID-PVs; one SWID-
PV sends a SWID Request but, unless exclusive delivery is used by the
SWID-PC in sending the response, both SWID-PVs receive copies of the
resulting SWID Response. In this case, the SWID-PV that didn't send
the SWID Request would lack the context necessary to correctly
interpret the SWID Response it received and would simply discard it.
Note, however, that proprietary measures might allow a SWID-PV to
discover the SWID Request parameters for a SWID Response even if that
SWID-PV did not send the given SWID Request. As such, there is no
blanket requirement for a SWID-PV to discard all SWID Responses to
SWID Request the SWID-PV did not generate itself, only that SWID-PVs
are required to discard SWID Responses for which they cannot get the
necessary context to interpret.
In the case that it is possible to do so, the SWID-PC MAY send its
SWID Response attribute to the SWID-PV that requested it using
exclusive delivery as described in section 3.3.2.2 of the IF-IMV r1.4
specification. Exclusive delivery ensures that only the sender of
the SWID Request receives the resulting SWID Response. However,
exclusive delivery is not always possible (it requires the use of IF-
IMC 1.3 or later and IF-IMV 1.3 or later, and not all products
currently do this) or necessarily desirable in all cases. As such,
SWID Message and Attributes for PA-TNC does not require support for
exclusive delivery of attributes.
3.3. SWID Tag Identifiers
SWID tags can contain a great deal of information about a software
product. In addition to identifying name, manufacturer, and version
of a software product, SWID tags might contain references to related
products, associated files and libraries, dependencies on other
software, and many other details. Moreover, SWID tags might be
customized on the endpoint to indicate when the SWID tag was last
checked for accuracy relative to the endpoint's installed software
and other information about how the software was received. (This
document refers to this customized information as
"installationspecific" tag information.) For this reason, actual
possession of a SWID tag can be useful for reasoning about details of
an endpoint's software inventory. However, a SWID tag file that
contains all optional fields might be tens of KB in size. This means
that an endpoint's full SWID inventory, encompassing hundreds of
applications, can be quite large.
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If bandwidth is a concern within an enterprise, there is a way to
identify a SWID tag without needing the complete tag. All tags
contain specific fields that can be used to distinguish a tag for a
particular piece of software from tags for different pieces of
software. The Tag Creator RegID is a string that uniquely identifies
the creator of this SWID tag (who might or might not be the same as
the entity who created the described software) while the Unique ID is
a string that uniquely identifies the described piece of software
according to that tag creator. These two pieces of information
together create a "tag identifier".
3.3.1. Tag Identifier Data
Some attributes defined in this specification contain fields to hold
tag identifiers rather than whole tags. When populating these
fields, both the Tag Creator RegID and the Unique ID values MUST be
copies of the values of fields within the SWID tag that is being
identified. The specific fields of a SWID tag that correspond to the
Tag Creator RegID and Unique ID values vary between the different
releases of the ISO SWID tag specification. It is important to note
that, in all other parts of this specification, the terms Tag Creator
RegID and Unique ID refer to the general field values defined above
rather to any term used in any specific release of the ISO SWID tag
specification.
To identify the SWID tag field corresponding to the Tag Creator
RegID, identify the field containing the regid value of the entity
that created the given SWID tag. Note that this might not be the
same entity that created the software. The Tag Creator RegID MUST be
the regid, rather than any prose name that might be associated with
the tag creator. The specific structure of a regid is defined in the
ISO/IEC SWID specification.
To identify the SWID tag field corresponding to the Unique ID, find
the field that contains a string that uniquely identifies a specific
product, version, edition, revision, etc. of a piece of software.
Note that this is a single field within the SWID tag, rather than a
concatenation of multiple fields. In particular, SWID tags often
contain designated fields for just the product name, product version,
product edition, etc., but these fields are not used to populate the
Unique ID. Instead, look for a single field that is designed to
uniquely identify a specific software product, version, etc. (and
thus uniquely identifies a specific tag, at least according to the
tag's creator).
Consult the ISO/IEC specification for the specific fields that
correspond to the requirements of the Tag Creator RegID and Unique
ID, as defined above. For example, in the 2009 version of the ISO/
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IEC SWID specification [SWID], the Tag Creator RegID corresponds to
the value of the software_identification_tag/software_id/
tag_creator_regid field in a SWID tag. The Unique ID corresponds to
the value of the software_identification_tag/software_id/unique_id
field in a SWID tag. In subsequent releases of the ISO/IEC SWID
specification, different fields might be used to convey the same
information.
3.3.2. Tag Identifier Instances
A tag identifier (i.e., the combination of the Tag Creator RegID and
the Unique ID fields) uniquely identifies a particular SWID tag,
which corresponds to a single software product. Assuming that this
product manages its own SWID tag (i.e., creates the tag on
installation and deletes the tag when the product is uninstalled)
then every system with an instance of this software product installed
would also have a copy of this same SWID tag file with the same tag
identifier field values. (Presence of SWID tags managed by other
tools, such as discovery tools, would also depend on the presence of
those tools on the device.) In fact, if multiple instances of the
same software product are installed on a single device (i.e., it has
been installed twice in different locations) that device would have
two instances of the same SWID tag, one for each installation. Both
instances of the SWID tag would have the same tag identifier field
values. This is true even though the tags themselves might differ
with regard to their installation-specific tag fields. In many cases
it is important to distinguish between instances of a particular tag
on a particular endpoint. For example, if one is alerted to the
deletion of a particular SWID tag and there are multiple instances of
that SWID tag on the endpoint, one will likely wish to know which
instance was deleted.
Individual instances of SWID tags are distinguished by providing an
"Instance ID" value along with the tag identifier. An Instance ID is
a string that is uniquely associated with a particular instance of a
SWID tag on a particular endpoint. The exact nature of the Instance
ID depends on the source of the SWID tag. If the SWID tag is
represented as a file on disk, the Instance ID might be the full path
of the SWID tag file, including the name of the SWID tag file itself.
(Note that the SWID tag filename MUST be included in the tag file
path because it is possible for two SWID tags, each for different
instances of the same software product, to co-exist in the same
directory under different file names.) In the case that the SWID tag
is dynamically generated upon request by some source, such as an RPM
or YUM package manager, the generation process MUST create an
Instance ID to distinguish instances of a particular tag. Inclusion
of this Instance ID ensures each tag is uniquely identified on a
given endpoint.
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To the extent that it is possible, the generation of Instance IDs
SHOULD be repeatable for a single installation of a single SWID tag.
In the case where a product is installed once, and then SWID tags are
generated upon request, each time the SWID tag is generated the tag
identifier instance SHOULD all have the same Instance ID value. For
example, if a package manager generates a SWID tag in response to a
request based on some record it possesses, and then later generates
the SWID tag again based on the same record of package installation,
then the same Instance ID value SHOULD be created both times. This
is necessary to allow remote parties to understand whether a reported
SWID tag instance is for the same product installation they saw
reported earlier or if it represents a new installation of the same
product. Note, however, that some exceptional situations might
result in the changing of a product's Instance ID. For example, it
is not explicitly prohibited by the SWID specification for tags to
move after installation, and thus have their tag file path change.
If the file path was used as the tag's Instance ID, subsequent tag
identifier instances for that same product might appear to be
different. Implementers and users need to be aware of this
possibility.
The combination of a tag identifier with an Instance ID is referred
to as a "tag identifier instance". A tag identifier instance
uniquely identifies a particular instance of a particular tag on a
given endpoint. Note that two endpoints might produce identical tag
identifier instances, but these do not mean that the tag files on the
two endpoints are identical - the tags in question indicate the same
software product on both endpoints (since the respective tag
identifiers are identical), but the tags might still differ in their
installation-specific fields. Therefore, it is important to remember
that tag identifier instances are only comparable in the scope of a
single endpoint; when comparing across different endpoints, only the
tag identifier fields (Tag Create RegID and Unique ID) can be
meaningfully compared - any Instance ID value will need to be
excluded from comparison.
3.3.3. Comparing Tag Identifiers and Tag Identifier Instances
Comparison of tag identifiers can be used to determine whether a
particular SWID tag is present in an endpoint's SWID tag collection.
A pair of SWID tag identifiers is said to "match" if their Tag
Creator RegID and Unique ID fields are identical. Similarly, a pair
of tag identifier instances is said to match if their Tag Creator
RegID, Unique ID, and Instance ID fields are identical. Fields in
SWID Message and Attributes for PA-TNC attributes that contain tag
identifiers or tag identifier instances MUST always be normalized to
Network Unicode, so comparison between values transported in
attributes can be a simple string comparison. When comparing tag
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identifiers and tag identifier instances from attributes with the
corresponding values from other sources (such as when comparing them
to a full SWID tag file or similar record), the relevant fields from
the latter need to undergo normalization prior to comparison. See
Section 4.7 for more on normalization of the encoding for these
fields. Comparisons are case-sensitive.
Matching tag identifiers and tag identifier instances indicate very
specific things about the respective tags. The following sections
describe what one can and cannot deduce based on matching tag
identifiers.
3.3.3.1. Matching Tag Identifiers Indicate the Same Software Product
The Unique ID value of a tag identifier represents a value that the
given tag creator will only use to indicate a particular software
product (e.g., a particular release of a particular application).
The ISO SWID specification prohibits the tag creator from associating
a Unique ID value with multiple, different software products. At the
same time, the Tag Creator RegID element value uniquely identifies a
given tag creator. As such, even if two different tag creators were
to assign the same Unique ID value to two different software
products, the Tag Creator RegID values will be different, and
therefore the tag identifiers will be different. For these reasons,
the expectation is that if one sees two tags with the same tag
identifiers, these tags are both associated with the same software
product (assuming the tag's fields are correctly populated).
3.3.3.2. Matching Tag Identifiers DO NOT Necessarily Indicate Identical
Tag Files
Some optional fields in SWID tags can reflect installation-specific
information. As such, the SWID tags for a piece of software residing
on two different endpoints (or installed twice on a single endpoint)
will have the same tag identifier value (same tag creator with the
same Unique ID for the same software product) but might contain
different information in their installation-specific fields. For
this reason, one cannot assume that just because two endpoints
provide the same tag identifier value for their software inventories,
that the tags on those endpoints are identical in all their fields
(although one can deduce that the same software product was present
on both endpoints).
Informative note: Initial drafts of the revised ISO SWID
specification indicate that modification of SWID tags might no longer
be permitted by parties other than the original tag creator (usually
the vendor of the software identified by the tag). If this becomes
part of the revised SWID specification, then for SWID tags that
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conform to this revised specification, this will mean that matching
tag identifiers do imply identical tag files.
3.3.3.3. Matching Tag Identifier Instances MIGHT Indicate Identical Tag
Files
For a single endpoint, matching tag identifier instance values might
indicate identical tag files, at least within a narrow time window.
Tag identifier instance values are unique to a specific SWID tag
record on that particular endpoint at a particular point in time.
The Instance ID in the tag identifier instance information ought to
be unique relative to any other instances of the same SWID tag
currently also on that endpoint. However, tag identifier instances
are still not guaranteed to be unique to a single SWID tag file over
a long period of time. Consider a piece of software that is
installed (adding a SWID tag), uninstalled (removing the SWID tag),
and then reinstalled (adding that SWID tag back but with a different
installation-specific field values). It is possible that the two
SWID tag files, present at different points in time, might have
identical tag identifier instance values even though the tag files
themselves were different.
As noted above, SWID tag identifier instances are only comparable
within the context of a single endpoint. When SWID tag identifier
instances are collected from multiple endpoints and then compared,
the Instance ID MUST be ignored in any comparison of tag identifiers
from different endpoints.
3.3.3.4. Differing Tag Identifiers DO NOT Necessarily Indicate
Different Software Products
While a tag identifier uniquely identifies a software product (i.e.,
that tag identifier cannot be associated with a different software
product), a single product might have more than one tag identifier.
This is because it is possible for more than one tag creator to
create a SWID tag for the same software product. Multiple tags for
the same software product but created by different tag creators will
have different Tag Creator RegID values and will also likely differ
in their Unique ID value. Thus, these two tags will have different
tag identifiers even though they were associated with the same
software product. In fact, in some circumstances, two parties might
create two different SWID tag records for a single instance of the
same software product. For example, when a product is installed, it
creates a SWID tag file on the file system, and a software discovery
tool also notes the installation of the product and generates its own
SWID tag record for the same installation. In this case, that single
installation is associated with two SWID tags with different SWID tag
identifiers. In short, identical tag identifiers always indicate the
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same software product, but different tag identifiers do not
necessarily indicate different software products.
3.3.4. Using Tag Identifiers in SWID Attributes
A SWID attribute reporting an endpoint's SWID tag collection can
contain SWID tag identifier instances instead of copies of SWID tag
files. The message exchange is identical to the diagram shown in
Figure 2, but the contents of the SWID Response are SWID tag
identifier instances instead of tags. The SWID Request attribute
indicates whether the response is required to use full tags or tag
identifier instances. Using tag identifier instances can reduce the
attribute size of the response by multiple orders of magnitude when
compared to sending the same inventory using full tags. A SWID-PC
responds to a SWID Request attribute requesting SWID tag identifier
instances the same way it responds to a request for full SWID tags,
except that instead of copying each SWID tag entirely into the
attribute body of the response, it provides the specific values that
comprise a SWID tag identifier instance for each tag.
3.4. Targeted Requests
Sometimes a SWID-PV does not require information about every tag on
an endpoint but only needs to know about certain tags. For example,
an endpoint might be required to have a particular patch installed.
In determining compliance with this policy, the SWID-PV is only
interested in the specific SWID tag associated with this patch.
Instead of requesting a complete inventory just to see if the patch's
SWID tag is present, the SWID-PV can make a "targeted request" for
the tag in question.
Targeted requests follow the same message exchange described in
Figure 2. The SWID-PV targets its request by providing one or more
SWID tag identifiers in its SWID Request attribute. The SWID-PC MUST
then limit its response to contain only tags that match the indicated
tag 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 SWID-PC's response
might consist of full tags or of tag identifier instances, depending
on the parameters of the SWID Request.
Targeted requests cannot target specific SWID tag instances; the SWID
Request does not include fields for Instance IDs. As a result, when
responding to a targeted request, a SWID-PC MUST return applicable
results for every instance of the identified tags.
Note that targeted requests identify the SWID tags relevant to the
request only through SWID tag identifiers for those tags. This
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specification does not support arbitrary, parameterized querying of
tags. For example, one cannot request all tags from a certain
software publisher, or all tags created by a particular tag creator.
Targeted requests only allow a requestor to request specific tags (as
identified by their tag identifiers) and receive a response that is
limited to the named tags. There is also no assumption that a SWID-
PC will recognize "synonymous tags" - that is, tags by different tag
creators for the same software product. The SWID-PC returns only
tags that match the tag identifiers in the SWID Request, even if
there might be other SWID tags in the endpoint's SWID tag collection
for the same software product.
SWID-PCs MUST accept targeted requests and process them correctly as
described above. SWID-PVs MUST be capable of making targeted
requests and processing the responses thereto.
3.5. Monitoring Changes in an Endpoint's SWID Tag Collection
The SWID collection on an endpoint is not static. As software is
installed, uninstalled, patched, or updated, the SWID tag collection
is expected to change to reflect the new software state on the
endpoint. For tags managed by an application's installer, tag
changes usually occur at the time of installation or update. For
tags added by discovery tools, software and package managers, and
other sources, changes to the endpoint's SWID tag collection occur
when some process discovers the new or altered software product,
which typically lags behind the actual installation or update time.
All SWID-PCs MUST be able to be able to detect changes to the SWID
tag repositories on their endpoint. Specifically, SWID-PCs MUST be
able to detect:
o The creation of tags
o The deletion of tags
o The alteration of tags
An "alteration" is anything that modifies the contents of a SWID tag
file (or would modify it, if the tag file is dynamically generated on
demand) in any way, regardless of whether the change is functionally
meaningful. Changes MUST be monitored for all utilized sources of
SWID tags. This includes, but is not limited to, monitoring sources
that dynamically generate SWID tags.
SWID-PCs MUST detect such changes to the endpoint's SWID tag
collection in close to real-time (i.e., within seconds) when the
Posture Collector is operating. In addition, in the case where there
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is a period during which the SWID-PC is not operating, the SWID-PC
MUST be able to determine the net change to the endpoint's SWID tag
collection over the period it was not operational. Specifically, the
"net change" represents the difference between the state of the
endpoint's SWID tag collection when the SWID-PC was last operational
and monitoring its state, and the state of the endpoint's SWID tag
collection when the SWID-PC resumed operation. Note that a net
change might not reflect the total number of change events over this
interval. For example, if a SWID tag file was altered three times
during a period when the SWID-PC was unable to monitor for changes,
the net change of this interval might only note that there was an
alteration to the file, but not how many individual alteration events
occurred. It is sufficient for a SWID-PC's determination of a net
change to note that there was a difference between the earlier and
current state rather than enumerating all the individual events that
allowed the current state to be reached.
The SWID-PC MUST assign a time to each detected change in the
endpoint's SWID tag collection. These timestamps correspond to the
SWID-PC's best understanding as to when the detected change occurred.
These timestamps MUST be as accurate as possible. For changes to the
endpoint's SWID tag collection that occur while the SWID-PC is
operating, the SWID-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 SWID tag collection that occur while the SWID-PC is not
operational, upon becoming operational the SWID-PC needs to make a
best guess as to the time of the relevant events (possibly by looking
at timestamps on the files), but these values might be off. In the
case of dynamically generated SWID tags, the time of change is the
time at which the data from which the SWID tags are generate changes,
not the time at which a changed SWID tag is generated. For example,
if SWID tags are dynamically generated based on data in an RPM
database, the time of change would be when the RPM record was
changed.
With regard to deletions of SWID tags, the SWID-PC needs to detect
the deletion and MUST retain a copy of the full deleted tag so that
the tag itself can be provided to the SWID-PV upon request. This
copy of the SWID tag MUST be retained for a reasonable amount of
time. Vendors and administrators determine what "reasonable" means,
but a copy of the tag SHOULD be retained for as long as the event
recording the deletion of the tag remains in the SWID-PC's records.
This is recommended because, as long as the event is in the SWID-PC's
records, the SWID-PC might send an event attribute (described in
Section 3.6) that references this tag, and a copy of the tag is
needed if the SWID-PV wanted a full copy of the relevant tags.
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With regard to alterations to a SWID tag file, SWID-PCs MUST detect
any alterations to the contents of a tag file. Alterations need to
be detected even if they have no functional impact on the tag file.
For example, the addition of whitespace between XML attributes does
not have any impact on the meaning of the SWID tag file, but still
needs to be detected as a tag file alteration by a SWID-PC. A good
guideline is that any alteration to a file that might change the
value of a hash taken on the file's contents needs to be detected by
the SWID-PC. A SWID-PC might be unable to distinguish modifications
to the content of a tag file from modifications to the metadata the
file system associates with the tag file. For example, a SWID-PC
might use the "last modification" timestamp as an indication of
alteration to a given tag file, but a file's last modification time
can change for reasons other than modifications to the file contents.
A SWID-PC is still considered compliant with this specification if it
also reports metadata change events that do not change the SWID tag
file itself as alterations to the SWID tag file. In other words,
while SWID-PC authors are encouraged to exclude modifications that do
not affect the bytes within the tag file when detecting alterations
to a SWID tag 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 SWID-PC always cover all modifications to the contents
of tag files, the SWID-PC is considered compliant even if it also
registers alterations that do not modify the contents of a tag file
as well. When recording an alteration to a tag file, the SWID-PC is
only required to note that an alteration occurred. The SWID-PC is
not required to note or record how the tag file altered, nor is it
possible to include such details in SWID Attributes reporting the
change to a SWID-PV.
3.6. Reporting Change Events
As noted in the preceding section, SWID-PCs MUST be able to detect
changes to the SWID tag repositories (tag creation, tag removal, and
tag alteration) in near real-time while the SWID-PC is operational,
and MUST be able to account for any net change to the endpoint's SWID
tag collection that occurs when the SWID-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 SWID Message and Attributes
for PA-TNC, this is facilitated by reporting change events. All
SWID-PCs MUST be capable of receiving requests for change events and
sending change event attributes. All SWID-PVs MUST be capable of
requesting and receiving change event attributes.
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3.6.1. Change Event Records
A change event record consists of either a complete SWID tag or SWID
tag identifier instance along with the following pieces of
information:
o The nature of the change (i.e., tag creation, tag deletion, or tag
alteration)
o An Event Identifier (EID) value
o An EID Epoch value
An EID is a 4-byte unsigned integer that the SWID-PC assigns
sequentially to each observed event (whether detected in real-time or
deduced by looking for net changes over a period of SWID-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 SWID-PC and any SWID-
PVs with which it communicates. EID Epoch values SHOULD be generated
randomly and in such a way that it is unlikely that the same EID
Epoch is generated twice, even if the SWID-PC reverted to an earlier
state (e.g., resetting it to factory defaults). In the case where a
SWID-PC needs to reset its EID counter, either because it has
exhausted all available EID values or because the SWID-PC's event log
becomes corrupted, then 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 SWID-PC might not otherwise be able to
determine an ordering for events. In these cases, the SWID-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 SWID Request attribute
indicates that a SWID-PV wants an inventory response rather than an
event response, while an EID of 0 in a SWID Response is used to
indicate the initial state of the endpoint's SWID tag collection
prior to the observation of any events. Thus the very first recorded
event in a SWID-PC's records within an EID Epoch MUST be assigned a
value of 1 or greater. Note that EID and EID Epoch values are
assigned by the SWID-PC without regard to whether events are being
reported to one or more SWID-PVs. The SWID-PC records events and
assigns EIDs during its operation. Any and all SWID-PVs that request
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event information from the SWID-PC will have those requests served
from the same records and thus will see the same EIDs and EID Epochs
for the same events.
The SWID-PC MUST ensure there is no coverage gap (i.e., change events
that are not recorded in the SWID-PC's records) in its records of
change events. This is necessary because a coverage gap might give a
SWID-PV a false impression of the endpoint's state. For example, if
a SWID-PV saw an event indicating that a particular SWID tag had been
installed, and saw no subsequent events indicating that tag had been
deleted, it might reasonably assume that this tag was still installed
(assuming the Epoch has not changed). If there is a coverage gap in
the SWID-PC's records, however, this assumption is false. For this
reason, the SWID-PC's event records MUST NOT contain gaps. In the
case where there are periods where it is possible that changes
occurred without the SWID-PC detecting or recording them, the SWID-PC
MUST either compute a net change and update its records
appropriately, or 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 SWID-PC's Epoch changes, all of these associations between
EIDs and events are cancelled, and EID values once again become free
for assignment.
3.6.2. 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 earlier state.
Every inventory sent by a SWID-PC to a SWID-PV (as described in
Section 3.2 through Section 3.4) includes the EID Epoch and EID of
the last event recorded prior to that inventory being compiled. This
allows the SWID-PV to place all subsequently received event records
in context relative to this inventory (since the EIDs represent a
total ordering of all changes to the endpoint's SWID tag collection).
Specifically, a SWID-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 in that
state. From that point on, if change events are observed, the
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attribute describing these events indicates the nature of the change,
the affected SWID tags, and the order in which these events occurred
(as indicated by the sequential EIDs). Using this information, any
remote record of the endpoint's SWID tag collection can be updated
appropriately.
3.6.3. Using Event Records in SWID Attributes
A SWID-PV MUST be able to request a list of event records instead of
an inventory. The message flow in such an exchange looks the same as
the basic flow shown in Figure 2. The only difference is that, in
the SWID Request attribute, the SWID-PV provides an EID other than 0.
(A value of 0 in these fields represents a request for an inventory.)
When the SWID-PC receives such a request, instead of identifying SWID
tags in the endpoint's SWID tag collection, it consults its record of
detected changes. The SWID-PC MUST add an event record to the SWID
Response attribute for each recorded change event with an EID greater
than or equal to the EID in the SWID Request attribute (although
targeting of requests, as described in the next paragraph, may limit
this list). A list of event records MUST only contain events with
EIDs that all come from the current Epoch.
SWID-PVs can target requests for event records by including one or
more tag identifiers, as described in Section 3.4, in the SWID
Request that requests an event record list. A targeted request for
event records is used to indicate that only events affecting SWID
tags that match the provided SWID tag identifiers are to be returned.
Specifically, in response to a targeted request for event records,
the SWID-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 SWID tag does not match one of the
provided SWID tag 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 SWID-PCs and SWIC-PVs MUST
support targeted request for event records.
3.6.4. Partial and Complete Lists of Event Records in SWID Attributes
Over time, a SWID-PC might record a large number of change events.
If a SWID-PV requests all change events covering a large period of
time, the resulting SWID Response attribute might be extremely large,
especially if the SWID-PV is requesting the use of full SWID tags
instead of the use of SWID Identifier instances (as described in
Section 3.3.4). In the case that the resulting attribute is too
large to send (either because it exceeds the 4GB attribute size limit
imposed by the PA-TNC specification, or because it exceeds some
smaller size limit imposed on the SWID-PC) the SWID-PC MAY send a
partial list of events back to the SWID-PV.
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Generation of a partial list of events in a SWID Response attribute
requires the SWID-PC to identify a "consulted range" of EIDs. A
consulted range is the set of event records that are examined for
inclusion in the SWID Response attribute and that are included in
that attribute if applicable. Recall that, if a SWID Request is
targeted, only event records that involve the indicated SWID tags
would be applicable. (See Section 3.4 for more on Targeted Request.)
If a request is not targeted, all event records in the considered
range are applicable and included in the SWID Response attribute.
The lower bound of the consulted range MUST be the EID provided in
the SWID Request. (Recall that a SWID Request indicates a request
for event records by providing a non-0 EID value in the SWID Request.
See Section 3.6.3.) 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 SWID Response attribute if it is applicable to the
request. The EID of this last event record is called the "Last
Consulted EID". The SWID-PC chooses this Last Consulted EID based on
the size of the event record list it is willing to provide to the
SWID-PV.
A partial result list MUST include all applicable event records
within the consulted range. This means that for any applicable event
record whose EID is greater than or equal to the EID provided in the
SWID Request and whose EID is less than or equal to the Last
Consulted EID, that event record MUST be included in the SWID
Response conveying this partial list of event records. This ensures
that every partial list of event records is always complete within
its indicated range.
All SWID Response attributes that convey event records (either using
full SWID tags or using SWID tag identifier instances) include an
Epoch, Last EID, and Last Consulted EID field. The Last EID contains
the EID of the last event record known to the SWID-PC at the time
that the SWID Response attribute was generated. The Last EID might
or might not be part of the consulted range. As noted above, the
Last Consulted EID field contains the EID of the last event record in
the consulted range. The Epoch field contains the EID Epoch
associated with the Last EID and Last Consulted EID fields as well as
all the EIDs in event records contained within the SWID Response
attribute. Note that, if responding to a targeted SWID Request, the
SWID Response attribute might not contain the event record whose EID
matches the Last Consulted EID value. For example, the last
consulted EID record might have been deemed inapplicable because it
did not match the specified list of SWID tag identifiers in the SWID
Request.
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If a SWID-PV receives a SWID Response attribute where the Last EID
and Last Consulted EID fields are identical, the SWID-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 and Last Consulted EID values differ, the SWID-PV has
received a partial result list. In the latter case, if the SWID-PV
wishes to try to collect the rest of the partially delivered result
list it then sends a new SWID Request whose EID is one greater than
the Last Consulted EID in the preceding response. Doing this causes
the SWID-PC to generate another SWID 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 SWID Response where the Last EID and Last Consulted EID
are equal, the SWID-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 SWID Request might specify an
EID that is greater than the EID of the last event recorded by a
SWID-PC. In accordance with the behaviors described in
Section 3.6.3, a SWID-PC MUST respond to such a request with a SWID
Response attribute of the appropriate type (using SWID tags or SWID
tag identifier instances as specified in the SWID Request) that
contains zero event records. This is because the SWID-PC has
recorded no event records with EIDs greater than or equal to the EID
in the SWID Request. In such a case, the Last Consulted EID field
MUST be set to the same value as the Last EID field in this SWID
response attribute. This case is called out because consulted range
on a SWID-PC in such a situation is a negative range, where the
"first" EID in the range (provided in the SWID Request) is greater
than the "last" EID in the range (this being the EID of the last
recorded event on the SWID-PC). Implementers need to ensure that
SWID-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.
3.6.5. Synchronizing Event Identifiers and Epochs
Since EIDs are sequential within an Epoch, if a SWID-PV's list of
event records contains gaps in the EID values within a single Epoch,
the SWID-PV knows that there are events that have not been accounted
for. The SWID-PV can either request a new event list to collect the
missing events or request a full inventory to re-sync its
understanding of the state of the SWID tags on the endpoint. In
either case, after the SWID-PV's record of the endpoint's SWID tag
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collection has been updated, the SWID-PV records the new latest EID
value and tracks events normally from that point on.
If the SWID-PV receives any attribute from a SWID-PC where the EID
Epoch differs from the EID Epoch that was used previously, then SWID-
PV or any entity using this information to track the endpoint's SWID
tag collection knows that there is a discontinuity in their
understanding of the endpoint's state. To move past this
discontinuity and reestablish a current understanding of the state of
the endpoint's SWID tag collection, the SWID-PV needs to receive a
full inventory from the endpoint. This is because it is not possible
to account for all events on the SWID-PC over the interval since the
previous Epoch was used, because there is no way to query for EIDs
from a previous Epoch. Once the SWID-PV has received a full
inventory for the new Epoch, the SWID-PV records the latest EID
reported in this new Epoch and can track further events normally.
A SWID-PC MUST NOT report events with EIDs from any Epoch other than
the current EID Epoch. The SWID-PC MAY choose to purge all event
records from a previous Epoch from memory after an Epoch change.
Alternately, the SWID-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 SWID-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 SWID-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 SWID-PC.) A
SWID-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 SWID-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 SWID-PC MUST purge all event records from before the 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 SWID-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 SWID-PC has
suffered an error of some kind, possibly indicative of at least
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partial corruption of its event log. In this case, the SWID-PV
SHOULD treat the situation as if there was a change in Epoch and
treat any local copy of the endpoint's SWID tag collection as out-of-
sync until a full inventory can be reported by the SWID-PC. In this
case, the SWID-PV SHOULD flag the event so it can be examined to
ensure it is now operating properly.
3.7. Supporting Multiple Instances of a Single Tag
One important consideration is that it is possible for multiple
instances of a SWID tag to be present on an endpoint. (I.e.,
multiple SWID tag files whose tag identifiers are the same.) This
can happen if there are multiple instances of the indicated software
product installed on the endpoint. In order to account for the
possibility, all SWID-PCs MUST follow specific rules, outlined below.
3.7.1. Inventory Reporting in the Presence of Multiply-Instantiated
Tags
When sending an inventory, either full or based on a targeted
request, the SWID-PC MUST include one entry for each instance of a
relevant tag. (All tags are relevant in a full inventory. In a
targeted request for an inventory, only tags that match the tag
identifiers provided by the SWID-PV are considered relevant.) For
example, if a particular piece of software is installed twice on an
endpoint, and thus there are two instances of its SWID tag present in
the endpoint's SWID tag collection, an inventory for which this tag
is relevant will contain at least two records for this piece of
software, one for each tag instance. (It might contain more if
multiple tag creators each created tags for the same piece of
installed software.) In the case where the SWID-PC's response is
expressed using full tags, the response MUST contain one copy of each
instance of the given tag. In other words, the SWID-PC MUST send one
copy of each tag instance, rather than send multiple copies of one
tag instance. In the case where the SWID-PC's response is expressed
using tag identifiers, the response MUST include the tag identifier
instance for each instance of the given tag.
3.7.2. Event Reporting in the Presence of Multiply Instantiated Tags
When reporting events, the specific tags that were added, deleted, or
changed MUST be indicated. For example, in the case where tags A and
B are two instances of the same SWID tag, each for separate
installations of the same software product, and tag A changes in the
endpoint's SWID tag collection, the SWID-PC MUST report the event
using tag A (rather than reporting it using B). This means that the
report MUST contain the tag file or the tag identifier instance for
the affected tag.
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3.8. Subscriptions
Thus far, all message exchanges discussed assume that a SWID-PV sent
an SWID Request attribute and the SWID-PC is providing a direct
response to that request. The SWID Message and Attributes for PA-TNC
specification also supports the ability for a SWID-PC to send a
message with a SWID Attribute to the SWID-PV in response to observed
changes in the endpoint's SWID tag collection, instead of in direct
response to a SWID Request. An agreement by a SWID-PC to send
content when certain changes are detected to the endpoint's SWID tag
collection is referred to in this specification as a "subscription",
and the SWID-PV that receives this content is said to be "subscribed
to" the given SWID-PC. All SWID-PCs and SWID-PVs MUST support the
use of subscriptions.
3.8.1. Establishing Subscriptions
A SWID-PV establishes a subscription on a particular SWID-PC by
sending a SWID Request attribute with the Subscription flag set. The
SWID Request attribute is otherwise identical to the SWID Requests
discussed in previous sections. Specifically, such a SWID Request
might request full tags or tag identifier instances, might be
targeted, and might request change event records or endpoint
inventory. Assuming no error is encountered, a SWID-PC MUST send a
SWID Response attribute in direct response to this SWID Request
attribute, just as if the Subscription flag was not set. As such,
the message exchange that establishes a new subscription in a SWID-PC
has the same flow seen in the previous message exchanges, as depicted
in Figure 2. If the SWID-PV does not receive a PA-TNC Error
attribute (as described in Section 3.10 and Section 4.16) in response
to their subscription request, the subscription has been successfully
established on the SWID-PC. The SWID Request attribute that
establishes a new subscription is referred to as the "establishing
request" for that subscription.
When a subscription is 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 4.8.)
A SWID-PC MUST have the ability to record and support multiple
simultaneous subscriptions from a single party and subscriptions from
multiple parties. A SWID-PV MUST have the ability to record and
support multiple simultaneous subscriptions to a single party and
subscriptions to multiple parties.
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3.8.2. Managing Subscriptions
The SWID-PC MUST record each accepted subscription along with the
identity of the party to whom attributes are to be pushed in
compliance with the subscription. If the attribute is received by
the SWID-PC using the TNC_IMC_ReceiveMessage (section 3.8.4 of IF-IMC
1.3 [IF-IMC]) function, then only the connection ID of the SWID-PV's
NEA Server is available to the SWID-PC. If the attribute is received
by the SWID-PC using the TNC_IMC_ReceiveMessageLong function (section
3.8.6 of IF-IMC) then the SWID-PC has both the NEA Server's
connection ID and the Posture Validator ID of the sending SWID-PV.
SWID-PCs SHOULD support TNC_IMC_ReceiveMessageLong function calls.
SWID-PCs MUST record the connection ID of the SWID-PV's NEA Server
for each accepted subscription. SWID-PCs SHOULD record the SWID-PV's
Posture Validator ID for each accepted subscription if this
information is available.
Likewise, SWID-PVs MUST record each accepted subscription for which
they are the subscribing party along with its Subscription ID and the
identity of the SWID-PC that will be fulfilling the subscription.
The SWID-PV needs to retain this information in order to correctly
interpret pushed SWID Response attributes sent in fulfillment of the
subscription. As with the SWID-PC, the SWID-PV might only have
access to the connection ID of the SWID-PC's endpoint, or might have
both this connection ID and the SWID-PC's Posture Collector ID
depending on the supported IF-IMV functions [IF-IMV]. SWID-PVs
SHOULD support TNC_IMV_ReceiveMessageLong function calls so as to be
capable of receiving the SWID-PC's Posture Collector ID. SWID-PVs
MUST record the connection ID of the SWID-PC's endpoint for each
accepted subscription. The SWID-PV SHOULD record the SWID-PC's
Posture Collector ID for each accepted subscription if this
information is available.
3.8.3. Terminating Subscriptions
Subscriptions MAY be terminated at any time by the subscribing SWID-
PV by setting the Clear Subscriptions flag in a SWID Request. (See
Section 4.9 for more on using this flag.) In the case that the SWID-
PC receives both the connection ID and the Posture Validator ID of
the SWID-PV requesting that subscriptions be cleared (i.e., the clear
subscription request is received via a TNC_IMC_ReceiveMessageLong
function) and the SWID-PC has been recording PV IDs associated with
subscriptions when available, the SWID-PC MUST only clear
subscriptions that match both the connection ID and the PV ID, and
MUST clear all such subscriptions. In the case that the SWID-PC only
has the connection ID of the party requesting that subscriptions be
cleared or the SWID-PC has not been recording Posture Validator IDs
associated with subscriptions even when available, it MUST only clear
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subscriptions that match the connection ID and that have no
associated Posture Validator ID, and MUST clear all such
subscriptions.
This specification does not give the SWID-PV the ability to terminate
subscriptions individually - all subscriptions to the SWID-PV are
cleared when the Clear Subscriptions flag is set.
This specification does not give the SWID-PC the ability to
unilaterally terminate a subscription. However, if the SWID-PC
experiences a fatal error fulfilling a subscription, resulting in
sending a PA-TNC Error attribute of type
SWID_SUBSCRIPTION_FULFILLMENT_ERROR, then the subscription whose
fulfillment led to the error MUST be treated as terminated by both
the SWID-PC and the SWID-PV. Only the subscription experiencing the
error is cancelled and other subscriptions are unaffected. See
Section 3.10 for more on this error condition.
Finally, a subscription is terminated if the connection between the
SWID-PC and SWID-PV is deleted, as indicated by the connection state
changing to DELETE. (Described in section 3.5.2.2 of IF-IMC [IF-IMC]
and section 3.5.2.2 of IF-IMV [IF-IMV].) Doing this renders the
SWID-PC incapable of pushing additional SWID Response attributes to
the subscribing party. Both the SWID-PC and SWID-PV MUST delete all
subscriptions for which the connection has been deleted. SWID-PCs
MUST support the TNC_IMC_NotifyConnectionChange function, as defined
in IF-IMC 1.3 section 3.8.2, so that the SWID-PC can be informed when
a connection's state changes to DELETE. Likewise, a SWID-PV MUST
support the TNC_IMV_NotifyConnectionChange function, as defined in
IF-IMV 1.4 section 3.8.2, for the same reason.
3.8.4. Subscription Status
A SWID-PV can request that a SWID-PC report the list of active
subscriptions where the SWID-PV is the subscriber. A SWID-PV can use
this to recover lost information about active subscriptions. A SWID-
PV can also use this capability to verify that a SWID-PC has not
forgotten any of its subscriptions. The latter is especially useful
where a SWID-PC does not send any attributes in fulfillment of a
given subscription for a long period of time. The SWID-PV can check
the list of active subscriptions on the SWID-PC and verify whether
the inactivity is due to a lack of reportable events, or due to the
SWID-PC forgetting its obligations to fulfill a given subscription.
A SWID-PV requests a list of its subscriptions on a given SWID-PC by
sending that SWID-PC a Subscription Status Request. The SWID-PC MUST
then respond with a Subscription Status Response (or a PA-TNC Error
if an error condition is experienced). The Subscription Status
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Response contains one subscription record for each of the active
subscriptions for which the SWID-PV is the subscribing party.
Specifically, in the case that the Subscription Status Request
arrives with both a connection ID and a Posture Validator ID and the
SWID-PC has been recording Posture Validator IDs associated with
subscriptions when available, the SWID-PC MUST include only
subscription records associated with both the given connection ID and
Posture Validator ID, and MUST include all such records. In the case
that the Subscription Status Request arrives with only a connection
ID or the SWID-PC has not been recording Posture Validator IDs
associated with subscriptions even when available, the SWID-PC MUST
include only subscription records associated with the given
connection ID and that have no associated Posture Validator ID, and
MUST include all such records.
3.8.5. Fulfilling Subscriptions
As noted in Section 3.5 SWID-PCs MUST have the ability to
automatically detect changes to an endpoint's SWID tag collection in
near real-time. For every active subscription, the SWID-PC MUST send
an attribute to the subscribed SWID-PV whenever a change is detected
to relevant tags within the endpoint's SWID tag collection. The
SWID-PC MAY choose to exclusively deliver this attribute in the case
that the SWID-PV's Posture Validator ID is known. (See section
3.3.2.2 of IF-IMC 1.3 [IF-IMC] or section 3.3.2.2 of IF-IMV 1.4
[IF-IMV] for more on exclusive delivery.) Such an attribute is said
to be sent "in fulfillment of" the given subscription and any such
attribute include that subscription's Subscription ID. If the
establishing request for that subscription was a targeted request,
then only tags that match the SWID tag identifiers provided in that
establishing request are considered relevant. Otherwise, (i.e., for
non-targeted requests) any tag is considered relevant for this
purpose. Figure 3 shows a sample message exchange where a
subscription is established and then later messages are sent from the
SWID-PC in fulfillment of the established subscription.
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+-------------+ +--------------+
| SWID-PC | | SWID-PV | Time
+-------------+ +--------------+ |
| | |
|<----------SWID Request------------| |
| | |
|-----------SWID Response---------->| |
| | |
. . .
. . .
. . .
<Change Event>| | |
|-----------SWID Response---------->| |
| | |
. . .
. . .
. . .
<Change Event>| | |
|-----------SWID 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 the same format as would a
direct response to the establishing request. For example, if the
establishing request stipulated a response that contained an event
record list wherein affected SWID tags were indicated using SWID tag
identifier instances, all attributes sent in fulfillment of this
subscription will also consist of event record lists expressed using
SWID tag identifier instances. As such, all SWID Responses displayed
in the exchange depicted in Figure 3 have the same format. A SWID
Response generated in fulfillment of an active subscription MUST be a
valid SWID 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 SWID-PV that had the
same request parameters and which arrived immediately after the given
change event. There are a few special rules that expand on this
guideline:
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3.8.5.1. Subscriptions Reporting Inventories
In the case that a SWID-PV subscribes to a SWID-PC requesting an
inventory attribute whenever changes are detected (i.e. the EID in
the establishing request is 0), then the SWID-PC MUST send the
requested inventory whenever a relevant change is detected. (A
"relevant change" is any change for untargeted requests, or a change
to an indicated SWID tag in a targeted request.) Upon detection of a
relevant change for an active subscription, the SWID-PC sends the
appropriate inventory information as if it had just received the
establishing request. Attributes sent in fulfillment of this
subscription will probably have a large amount of redundancy, as the
same tags are likely to be present in each of these SWID Attributes.
The role of an inventory subscription is not to report tags just for
the items that changed - that is the role of a subscription that
reports events (see Section 3.8.5.2). A SWID-PC MUST NOT exclude a
tag from an attribute sent in fulfillment of an inventory
subscription simply because that tag was not involved in the
triggering event (although the tag might be excluded for other
reasons, such as if the subscription is targeted - see
Section 3.8.5.3).
3.8.5.2. Subscriptions Reporting Events
The way in which a SWID-PV indicates it wishes to establish a
subscription requesting event records is by providing a non-zero EID
in the SWID Request establishing the subscription (see
Section 3.6.1). However, when the SWID-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 indicated 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 SWID-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 SWID-PC MUST only report events with later
EIDs. In the case that the EID Epoch of the SWID-PC changes, the
SWID-PC MUST treat EID values in the new Epoch as being after all
EIDs assigned in the previous Epoch regardless of the relative
numeric values of these EIDs.
Note that while a subscription is active, the subscribing SWID-PV MAY
make other requests for event records that overlap with events that
are reported due to a subscription. Such requests are unaffected by
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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
SWID-PV.
A SWID-PV needs to pay attention to the EID Epoch in these messages,
as changes in the Epoch might create discontinuities in the SWID-PV's
understanding of the endpoint's SWID tag collection state, as
discussed in Section 3.6.5. In particular, once the EID Epoch
changes, a SWID-PV is unable have confidence that it has a correct
understanding of the state of an endpoint's SWID tag collection until
after the SWID-PV collects a complete inventory.
SWID-PCs MAY send partial lists of event records in fulfillment of a
subscription. (See Section 3.6.4 for more on partial list of event
records.) In the case that a SWID-PC sends a partial list of event
records, it MUST immediately send the next consecutive partial list,
and continue doing so until it has sent the equivalent of the
complete list of event records. In other words, if the SWID-PC sends
a partial list it does not wait for another change event to send
another SWID Response, but continues sending SWID Responses until it
has sent all event records that would have been included in a
complete fulfillment of the subscription.
3.8.5.3. Targeted Subscriptions
Subscriptions MAY be targeted to only apply to tags that match a
given set of tag identifiers. In the case where changes are detected
that affect multiple tags, some matching the establishing request's
tag identifiers and some not, the attribute sent in fulfillment of
the subscription MUST only include inventory or events (as
appropriate) for tags that match the establishing request's tag
identifiers. The SWID-PC MUST NOT include non-matching tags in the
attribute, even if those non-matching tags experienced change events
that were co-temporal with change events on the matching tags.
In addition, a SWID-PC MUST send an attribute in fulfillment of a
targeted subscription only when changes to the endpoint's SWID tag
collection impact one or more tags matching the subscription's
establishing request's tag identifiers. A SWID-PC MUST NOT send any
attribute in fulfillment of a targeted subscription based on detected
change to the endpoint's SWID tag collection that did not involve any
of the tags targeted by that subscription.
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3.8.5.4. No Subscription Consolidation
A SWID-PV MAY establish multiple subscriptions to a given SWID-PC.
If this is the case, it is possible that a single change event on the
endpoint might require fulfillment by multiple subscriptions, and
that the information included in attributes that fulfill each of
these subscriptions might overlap. The SWID-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, SWID-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 SWID-PV.
3.8.5.5. Delayed Subscription Fulfillment
A SWID-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 SWID-PV in a single SWID Response attribute. This can
help reduce network bandwidth consumption between the SWID-PC and the
SWID-PV. For example, consider a situation where 10 changes occur a
tenth of a second apart. If the SWID-PC does not delay in assembling
and sending SWID Response attributes, the SWID-PV will received 10
separate SWID Response attributes over a period of 1 second.
However, if the SWID-PC waits half a second after the initial event
before assembling a SWID Response, the SWID-PV only receives two SWID
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, SWID-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 SWID tag is deleted and
then re-added), the SWID-PC MUST still report each change event
rather than just reporting the net effect of changes over the delay
period. In other words, delayed fulfillment can decrease the number
of attributes send by the SWID-PC, but it does not reduce the total
number of change events reported.
SWID-PCs are not required to support delayed fulfillment of
subscriptions. However, in the case that the SWID-PC does support
delayed subscription fulfillment, it MUST be possible to configure
the SWID-PC to disable delayed fulfillment. In other words, parties
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deploying SWID-PCs need to be allowed to disable delayed subscription
fulfillment in their SWID-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. Multiple Sources of SWID Tags
As noted in Section 2.1, the SWID tags in an endpoint's SWID tag
collection might potentially come from multiple sources. For
example, SWID tags might be deposited on the file system and
collected therefrom. SWID tags might also be dynamically generated
by tools such as software and package managers (e.g., RPM or YUM) or
might be dynamically translated from software discovery reports
expressed in some non-SWID format.
A SWID-PC is not required to identify every possible source of SWID
tags on its endpoint. Some SWID-PCs might be explicitly tied only to
one or a handful of SWID tag sources. SWID-PCs are not required to
be aware of SWID tags that come from sources other than those that
they specifically support. In particular, if an endpoint has 3
sources of SWID tags, and a SWID-PC supports collecting SWID tags
from two of those sources, not only is that SWID-PC only responsible
for reporting tags that come from its two supported sources, but it
is also only responsible for monitoring for change events from those
two sources. This noted, for all of the SWID tag sources that a
particular SWID-PC supports, it MUST completely support all
requirements of this specification with regard to its supported
sources. In other words, for supported sources, the SWID-PC is
required to be capable of providing complete inventories of SWID
tags; monitoring for changes in the SWID collections reported by
those sources, correctly providing responses for both full and
targeted requests, and providing either complete SWID tag files or
SWID identifier instances as appropriate. The SWID-PC MUST NOT
provide any inventory or event information from SWID tag sources for
which it cannot provide this full support.
The SWID Response attributes provide no way of distinguishing as to
which SWID tags, identifier instances, or event records are
associated with specific sources. The SWID-PC MUST include the
complete set of relevant data from all supported sources of SWID tags
in every SWID Response. In other words, a full inventory is required
to contain all the SWID tags from all supported sources, a targeted
inventory is required to contain all relevant tags from all sources,
and event tracking is required to cover all events from both sources.
With regard to events, a SWID-PC's assignment of EIDs MUST reflect
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the presence and order of all events on the endpoint (at least for
supported sources) regardless of the source. This means that if
source A experiences an event, and then source B experiences two
events, and then source A experiences another two events, the SWID-PC
is required to capture five events with consecutive EID values
reflecting the order in which the events occur.
Note that, if a SWID-PC collects data from multiple sources, it is
possible that some software products might be "double counted". This
can happen if both sources of SWID tags provide a SWID tag for a
single instance of a software product. Moreover, each of these
provided tags will probably have different SWID tag identifier
instances, since Instance IDs are managed by the process that
extracts the SWID tags from the individual sources, and such
processes are under no obligation to coordinate with each other as to
the Instance ID value. When a SWID-PC reports information or records
events from multiple SWID tag sources, it MUST use the information
those sources provide, rather than attempting to perform some form of
reduction. In other words, if multiple sources report a particular
SWID tag corresponding to a single installation of a software
product, all such tags from each source are required to be part of
the SWID-PC's processing even if this might lead to multiple
reporting, and the SWID-PC is not to ignore some tags to avoid such
multiple reporting. Similarly, in the case that multiple sources
report an event, the SWID-PC MUST create separate event records with
separate EIDs for each of these, even if there is the chance that
they represent the two sources reporting the same action on the
endpoint. Entities tracking SWID tags collected via SWID-PCs and
SWID-PVs need to be aware that such double-reporting might occur.
How (or if) such occurrences are detected and resolved is up to the
implementers of those entities.
3.10. Error Handling
In the case where the SWID-PC detects an error in a SWID Request
attribute that it 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 Section 4.16 in this
specification for error codes specific to SWID attributes.) In the
cast that an error is detected in a SWID Request the SWID-PC MUST NOT
take any action requested by this SWID Request, even if some
requested action can be completed successfully despite the error in
the attribute. In other words, a SWID Request that contains an error
is ignored by the SWID-PC beyond sending a PA-TNC Error attribute,
and possibly logging the error locally.
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In the case where the SWID-PC receives a valid SWID Request attribute
but experiences an error during the process of responding to that
attribute's instructions where that error prevents the SWID-PC from
properly or completely fulfilling that request, the SWID-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 SWID-PC MUST NOT take any of the actions requested by the SWID
Request attribute which led to the detected error. This is the case
even if some actions can be completed successfully, and might even
require the SWID-PC to reverse some successful actions already taken
before the error condition was detected. In other words, either all
aspects of a SWID Request complete fully and successfully (in which
case the SWID-PC sends a SWID Response attribute), or no aspects of
the SWID Request occur (in which case the SWID-PC sends a PA-TNC
Error attribute). In the case that a SWID-PC sends a PA-TNC Error
attribute in response to a SWID Request then the SWID-PC MUST NOT
also send any SWID Response attribute in response to the same SWID
Request. For this reason, the sending of a SWID Response attribute
MUST be the last action taken by a SWID-PC in response to a SWID
Request to avoid the possibility of a processing error occurring
after that SWID Response attribute is sent.
In the case that the SWID-PC detects an error that prevents it from
properly or completely fulfilling its obligations under an active
subscription, the SWID-PC MUST send a PA-TNC Error attribute of type
SWID_SUBSCRIPTION_FULFILLMENT_ERROR to the SWID-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 an error "sub-type". The error sub-
type is used to indicate the type of error condition the SWID-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 SWID_ERROR error code
SHOULD be used in the sub-type. In the case that a
SWID_SUBSCRIPTION_FULFILLMENT_ERROR is sent, the associated
subscription MUST be treated as cancelled by both the SWID-PC and
SWID-PV.
The SWID-PV MUST NOT send any PA-TNC Error attributes to SWID-PCs.
In the case that a SWID-PV detects an error condition, it SHOULD log
this error but does not inform any SWID-PC's of this event. Errors
might include, but are not limited to, detection of malformed SWID
Response attributes sent from a given SWID-PC, as well as detection
of error conditions when the SWID-PV processes SWID Responses.
Both SWID-PCs and SWID-PVs SHOULD log errors so that administrators
can trace the causes of errors. Log messages SHOULD include the type
of the error, the time it was detected, and additional descriptive
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information to aid in understanding the nature and cause of the
error.
4. SWID Message and Attributes for PA-TNC Protocol
This section describes the format and semantics of the SWID Message
and Attributes for PA-TNC protocol leveraging the existing SWID tag
format. SWID Message and Attributes for PA-TNC uses the standard PA-
TNC message header format. See the PA-TNC specification [RFC5792]
for information on this header format.
4.1. PA Subtype (AKA PA-TNC Component Type)
The NEA PB-TNC 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
identifier called the 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. In order for the NEA protocols
to carry SWID tags, this specification adds the following enumeration
element to the table in section 7.2 of the PA-TNC specification
[RFC5792] using the IETF Standard name space (SMI Private Enterprise
Number 0x000000):
+-----+---------+----------------+----------------------------------+
| PEN | Integer | Name | Defining Specification |
+-----+---------+----------------+----------------------------------+
| 0 | 9 | SWID | SWID Message and Attributes for |
| | | Attributes | PA-TNC |
+-----+---------+----------------+----------------------------------+
Table 2: PA Subtype
Each PA-TNC attribute described in this specification is intended to
be sent between the SWID-PC and SWID-PV, so will be carried in a PB-
TNC message indicating a PA Subtype of SWID Attributes. Note that
although the PA-TNC Error attribute is defined in the PA-TNC
specification, when it is used in a SWID Attribute exchange, it uses
the SWID Attributes Component Definition Value, as described in
Section 4.2.8 of the PA-TNC specification [RFC5792]. PB-TNC messages
MUST always include the SWID Attributes Subtype defined in this
section when carrying SWID Attributes over PA-TNC.
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4.2. PB-TNC and PA-TNC Messages
A PA-TNC message is wrapped within a PB-TNC message. A single PA-TNC
message might contain one or more PA-TNC attributes. All of these
attributes within a single PA-TNC message use the same PA Subtype
value. As such, SWID Attributes are never sent with attributes
defined in other PA-TNC binding specifications in a single PA-TNC
message. Note, however, that a single PB-TNC batch might contain
multiple PB-TNC and PA-TNC messages, and each of those messages might
use different PA Subtypes.
For more information on PB-TNC and PA-TNC messages and message
headers, see the PB-TNC [RFC5793] and PA-TNC [RFC5792]
specifications, respectively.
4.3. PA-TNC Attribute Header
The SWID Message and Attributes for PA-TNC protocol described in this
specification is an extension of the PA-TNC protocol described in the
NEA Architecture. PA-TNC was designed to be very flexible in order
to carry many types of PA-TNC attributes that pertain to an
enumerated set of component types (e.g. Table 2). PA-TNC attributes
might be carried from Posture Collector to Posture Validator or vice
versa and might carry information about endpoint state or other
information to be sent between a Posture Validator and a Posture
Collector. Therefore the SWID Message and Attributes for PA-TNC
specification defines a collection of PA-TNC attributes relevant to
the collection and transmission of SWID tag inventories.
Figure 4, reproduced from the PA-TNC specification, shows the format
of a PA-TNC attribute. Multiple PA-TNC attributes can be sent in a
single PB-TNC message, each housed within an attribute structure as
described below.
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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 | PA-TNC Attribute Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Value (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: PA-TNC Header and Attribute Format
+-----------+-------------------------------------------------------+
| Field | Description |
+-----------+-------------------------------------------------------+
| Flags | This field defines flags affecting the processing of |
| | the SWID Message and Attributes for PA-TNC. |
| | Permissible flags are given in the PA-TNC |
| | specification. [RFC5792] |
| Attribute | This field indicates the owner of the name space |
| Type | associated with the Attribute Type. Attributes |
| Vendor ID | defined in the SWID Message and Attributes for PA-TNC |
| | specification have a value corresponding to the IETF |
| | SMI Private Enterprise Number value (0x000000). The |
| | PA-TNC Error attribute is defined in the PA-TNC |
| | specification [RFC5792] and also uses the IETF SMI |
| | Private Enterprise Number Value (0x000000). See Table |
| | 4 for more information. |
| Attribute | This field defines the type of the Attribute. The |
| Type | values corresponding to SWID Attributes are given in |
| | Table 4. |
| Attribute | This field contains the length in octets of the |
| Length | entire Attribute, including the Attribute's header. |
| Attribute | This field contains the SWID Attribute. |
| Value | |
+-----------+-------------------------------------------------------+
Table 3: Fields of the PA-TNC Attribute Format
4.4. SWID Attribute Overview
The attributes defined in this specification appear below with a
short summary of their purposes. Each attribute is described in
greater detail in subsequent sections.
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o SWID Request - This attribute is used to request a SWID tag
inventory or SWID event list from an endpoint. This attribute
might also establish a subscription on the recipient SWID-PC. A
SWID-PC MUST NOT send this attribute.
o SWID Tag Identifier Inventory - This attribute is used to convey
an inventory expressed using SWID tag identifier instances
(instead of full tags). When a SWID-PC receives a SWID Request
attribute requesting an inventory using SWID tag identifier
instances, the SWID-PC MUST send a SWID Tag Identifier Inventory
attribute (or a PA-TNC Error) in response. This attribute also
MAY be sent by the SWID-PC in fulfillment of an active
subscription. A SWID-PV MUST NOT send this attribute.
o SWID Tag Identifier Events - This attribute is used to convey a
list of events concerning changes to an endpoint's collection of
SWID tags. Affected SWID tags are indicated using SWID tag
identifier instances (instead of full tags). When a SWID-PC
receives a SWID Request attribute requesting an event collection
using with SWID tag identifier instances, the SWID-PC MUST send a
SWID Tag Identifier Events attribute (or a PA-TNC Error) in
response. This attribute also MAY be sent by the SWID-PC in
fulfillment of an active subscription. A SWID-PV MUST NOT send
this attribute.
o SWID Tag Inventory - This attribute is used to convey an inventory
expressed using full SWID tags (instead of SWID tag identifier
instances). When a SWID-PC receives a SWID Request attribute
requesting an inventory using full SWID tags, the SWID-PC MUST
send a SWID Tag Inventory attribute (or a PA-TNC Error) in
response. This attribute also MAY be sent by the SWID-PC in
fulfillment of an active subscription. A SWID-PV MUST NOT send
this attribute.
o SWID Tag Events - This attribute is used to convey a list of
events concerning changes to an endpoint's collection of SWID
tags. Affected SWID tags are indicated using full SWID tags
(instead of SWID tag identifier instances). When a SWID-PC
receives a SWID Request attribute requesting an event collection
using full SWID tags, the SWID-PC MUST send a SWID Tag Events
attribute (or a PA-TNC Error) in response. This attribute also
MAY be sent by the SWID-PC in fulfillment of an active
subscription. A SWID-PV MUST NOT send this attribute.
o Subscription Status Request - This attribute is used to request a
SWID-PC send a summary of all the active subscriptions it has
where the requesting party is the subscriber. The SWID-PC MUST
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respond with a Subscription Status Response (or a PA-TNC Error).
A SWID-PC MUST NOT send this attribute.
o Subscription Status Response - This attribute is used to convey
information about the active subscriptions that a SWID-PC has for
a given subscriber. A SWID-PV MUST NOT send this attribute.
o PA-TNC Error - This is the standard PA-TNC Error attribute as
defined in PA-TNC [RFC5792] and is used to indicate that an error
was encountered during a SWID Attribute exchange. It MUST be sent
by a SWID-PC in response to a SWID Request in the case where the
SWID-PC encounters a fatal error (i.e., an error that prevents
further processing of an exchange) relating to the attribute
exchange. A SWID-PV MUST NOT send this attribute. The SWID-PC
MUST then ignore the erroneous attribute after a PA-TNC Error
attribute is sent (i.e., do not attempt to act on an attribute
that generated a PA-TNC Error beyond sending the PA-TNC Error).
In the case where the SWID-PV experiences a fatal error, it MUST
ignore the erroneous attribute without sending a PA-TNC Error
attribute. It MAY take other actions in response to the error,
such as logging the cause of the error, or even taking actions to
isolate the endpoint
Because one of the SWID Tag Identifier Inventory, SWID Tag Identifier
Events, SWID Tag Inventory, or SWID Tag Events attributes is expected
to be sent to a SWID-PV in direct response to a SWID Request
attribute or in fulfillment of an active subscription, those four
attribute types are frequently referred to collectively in this
document as "SWID Response" attributes.
All SWID-PVs MUST be capable of sending SWID Requests and be capable
of receiving and processing all SWID Response attributes as well as
PA-TNC Error attributes. All SWID-PCs MUST be capable of receiving
and processing SWID Requests and be capable of sending all types of
SWID Response attributes as well as PA-TNC Error attributes. In
other words, both SWID-PVs and SWID-PCs are required to support their
role in exchanges using any of the attribute types defined in this
section. SWID-PVs MUST ignore any SWID Request attributes that they
receive. SWID-PCs MUST ignore any SWID Response attributes or PA-TNC
Error attributes that they receive.
4.5. SWID Attribute Exchanges
A SWID Attribute Exchange is used to provide the SWID-PV with a SWID
tag inventory or event collection from the queried endpoint.
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+-------------+ +--------------+
| SWID-PC | | SWID-PV | Time
+-------------+ +--------------+ |
| | |
|<-----------SWID Request-------------| |
| | |
| SWID Response* | |
|-----------------or----------------->| |
| PA-TNC Error | |
| | V
*SWID Response is one of the following: SWID Tag Identifier
Inventory, SWID Tag Identifier Events, SWID Tag Inventory,
or SWID Tag Events.
Figure 5: SWID Attribute Exchange (Direct Response to SWID Request)
In this exchange, the SWID-PV indicates to the SWID-PC, via a SWID
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 (full tags or tag identifier
instances). The SWID-PC responds with the requested information
using the appropriate attribute type. A single SWID Request MUST
only lead to a single SWID Response or PA-TNC Error that is in direct
response to that request.
In addition, if there is an active subscription on the endpoint, the
SWID-PC sends a SWID Response to the SWID-PV following a change event
on the endpoint in fulfillment of that subscription. Such an
exchange is shown in Figure 6.
+-------------+ +--------------+
| SWID-PC | | SWID-PV | Time
+-------------+ +--------------+ |
| | |
<Change Event>| | |
|-------SWID Response(s)*------>| |
| | |
*SWID Response is one of the following: SWID Tag Identifier
Inventory, SWID Tag Identifier Events, SWID Tag Inventory,
or SWID Tag Events.
Figure 6: SWID Attribute Exchange (In Fulfillment of an Active
Subscription)
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Note that, unlike direct responses to a SWID Request, a single change
event can precipitate multiple SWID Responses, but only if all but
the last of those SWID Responses convey partial lists of event
records, and the last of those SWID Responses conveys a complete list
of event records. (That is, the initial responses are partial lists
and the last response is the remainder of the relevant event records,
completing the delivery of all relevant events at the time of the
change event.) A single Change Event MUST NOT be followed by
multiple SWID Response or PA-TNC Error attributes in any combination
except as noted earlier in this paragraph.
All SWID-PVs and SWID-PCs MUST support both exchanges. In
particular, SWID-PCs MUST be capable of pushing a SWID Response to a
SWID-PV immediately upon detection of a change to the endpoint's SWID
tag collection in fulfillment of established SWID-PV subscriptions,
as described in Section 3.8.
4.6. SWID Message and Attributes for PA-TNC Attribute Enumeration
PA-TNC attribute types are identified in the PA-TNC Attribute Header
(see Section 4.2) via the Attribute Type Vendor ID and Attribute Type
fields. Table 4 identifies the appropriate values for these fields
for each attribute type used within the SWID Message and Attributes
for PA-TNC protocol.
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+--------------+----------+------------+----------------------------+
| Attribute | PEN | Integer | Description |
| Name | | | |
+--------------+----------+------------+----------------------------+
| SWID Request | 0x000000 | 0x00000011 | Request from a SWID-PV to |
| | | | a SWID-PC for the SWID-PC |
| | | | to provide a SWID tag |
| | | | inventory or event list |
| SWID Tag | 0x000000 | 0x00000012 | A collection of SWID tag |
| Identifier | | | identifier instances sent |
| Inventory | | | from a SWID-PC. |
| SWID Tag | 0x000000 | 0x00000013 | A collection of events |
| Identifier | | | impacting the endpoint's |
| Events | | | SWID tag collection, where |
| | | | impacted SWID tags are |
| | | | indicated using SWID tag |
| | | | identifier instances. |
| SWID Tag | 0x000000 | 0x00000014 | A collection of SWID tags |
| Inventory | | | sent from a SWID-PC. |
| SWID Tag | 0x000000 | 0x00000015 | A collection of events |
| Events | | | impacting the endpoint's |
| | | | SWID tag collection, where |
| | | | impacted SWID tags are |
| | | | indicated using full SWID |
| | | | tags. |
| Subscription | 0x000000 | 0x00000016 | A request for a list of a |
| Status | | | SWID-PV's active |
| Request | | | subscription. |
| Subscription | 0x000000 | 0x00000017 | A list of a SWID-PV's |
| Status | | | active subscriptions. |
| Response | | | |
| Reserved | 0x000000 | 0x00000018 | These attribute types are |
| | | - | reserved for future use in |
| | | 0x0000001F | revisions to SWID Message |
| | | | and Attributes for PA-TNC. |
| PA-TNC Error | 0x000000 | 0x00000008 | An error attribute as |
| | | | defined in the PA-TNC |
| | | | specification [RFC5792]. |
+--------------+----------+------------+----------------------------+
Table 4: SWID Attribute Enumeration
4.7. Normalization of Text Encoding
SWID tags do not have a required encoding format. The 2009 ISO SWID
specification states that "For encoding purposes, the use of utf-8 is
the suggested methodology for software identification tags...", but
leaves implementers free to use different encodings if this makes
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sense in their local environment. As such, implementers of the SWID
Message and Attributes for PA-TNC specification cannot assume any
specific encoding of SWID tag fields (although, in most current
examples of SWID tags, SWID tag creators have followed the suggestion
of using UTF-8 encodings). Similarly, sometimes the SWID Message and
Attributes for PA-TNC specification requires the use of data taken
from other sources, such a path from the endpoint's file system, and
different platforms might use different encodings for this
information. In order to ensure the ability to consistently and
reliably compare information sent using the SWID Message and
Attributes for PA-TNC exchange, certain field values (identified
explicitly in the attribute definitions in the following sections)
are required to undergo normalization prior to their inclusion in an
attribute.
In order to ensure consistency of transmitted attributes, a field
requiring normalization, as indicated in its description, and only
such fields MUST be normalized to Network Unicode format as defined
in RFC 5198 [RFC5198]. Network Unicode format defines a refinement
of UTF-8 that ensures a normalized expression of characters. SWID-
PCs and SWID-PVs MUST NOT perform conversion and normalization on any
field values except those specifically identified in the following
sections.
4.8. Request IDs
All SWID 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 SWID-PV and the receiving SWID-
PC. Specifically, the SWID-PV assigns each SWID 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 SWID-PV's Posture
Broker Server (as described in section 3.5.2.2 of the IF-IMV
specification [IF-IMV]). In the case where all possible Request ID
values have been exhausted within the lifetime of a single network
connection ID, the sender MAY reuse previously used Request IDs
within the same network connection that are not being used as
Subscription IDs. (See below in this section for an explanation of
Subscription ID assignment.) In this case of Request ID reuse,
Request IDs SHOULD be reused in the order of their original use. For
example, if a Request ID of X was the first Request ID used within a
particular network connection and if the Request IDs are exhausted, X
will be the first reused Request ID. In other words, a SWID-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, but, in the case where reuse is necessary due to
exhaustion of possible ID values, the SWID-PC SHOULD structure the
reuse to maximize the time between original and subsequent use. The
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Request ID value is included in a response attribute directly
responding to this SWID Request to indicate which SWID 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. SWID-PCs are not required to check for
duplicate Request IDs.
In the case that a SWID Request requests the establishment of a
subscription and the receiving SWID-PC agrees to that subscription,
the Request ID of that SWID 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 SWID-PV MUST NOT reuse a Request
ID value in communicating to a given SWID-PC while that Request ID is
also serving as a Subscription ID for an active subscription with
that SWID-PC. In the case where a SWID-PC receives a SWID Request
from a given SWID-PV where that Request ID is also the Subscription
ID of an active subscription with that SWID-PV, the SWID-PC MUST
respond with a PA-TNC Error attribute with an error code of
SWID_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.
4.9. SWID Request
A SWID-PV sends this attribute to a SWID-PC to request that the SWID-
PC send SWID tag-based information to the SWID-PV. A SWID-PC MUST
NOT send this attribute.
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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 | Tag ID Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Earliest EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag Creator Length | Tag Creator (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unique Software ID Length |Unique Software ID (var length)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: SWID Request Attribute
+---------------+---------------------------------------------------+
| Field | Description |
+---------------+---------------------------------------------------+
| Flags: Bit 0 | If set (1), the SWID-PC MUST delete all |
| - Clear | subscriptions established by the requesting SWID- |
| Subscriptions | PV (barring any errors). |
| Flags: Bit 1 | If set (1), in addition to responding to the |
| - Subscribe | request as described, the SWID-PC MUST establish |
| | a subscription with parameters matching those in |
| | the request attribute (barring any errors). |
| Flags: Bit 2 | If unset (0), the SWID-PC's response MUST consist |
| - Result Type | of complete SWID tags and thus the response MUST |
| | be a SWID Tag Inventory, a SWID Tag Events, or a |
| | PA-TNC Error attribute. If set (1), the response |
| | MUST consist of SWID tag identifier instances and |
| | thus the response MUST be a SWID Tag Identifier |
| | Inventory, a SWID Tag Identifier Events, or a PA- |
| | TNC Error attribute. |
| Flags: Bit | Reserved for future use. This field MUST be set |
| 3-7 - | to zero on transmission and ignored upon |
| Reserved | reception. |
| Tag ID Count | A 3-byte unsigned integer indicating the number |
| | of tag identifiers that follow. If this value is |
| | non-zero, this is a targeted request, as |
| | described in Section 3.4. This field is a 3-byte |
| | unsigned integer. The Tag Creator Length, Tag |
| | Creator, Unique Software ID Length, and Unique |
| | Software ID fields are repeated, in order, the |
| | number of times indicated in this field. In the |
| | case where tag identifiers are present, the SWID- |
| | PC MUST only respond with SWID tags or tag |
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| | identifier instances that correspond to the |
| | identifiers the SWID-PV provided in this |
| | attribute (or with a PA-TNC Error attribute). |
| | This field value MAY be 0, in which case there |
| | are no instances of the Tag Creator Length, Tag |
| | Creator, Unique Software ID Length, and Unique |
| | Software ID fields. In this case, the SWID-PV is |
| | indicating an interest in all SWID tags on the |
| | endpoint (i.e., this is not a targeted request). |
| Request ID | A value that uniquely identifies this SWID |
| | Request from a particular SWID-PV. |
| Earliest EID | In the case where the SWID-PV is requesting SWID |
| | events, this field contains the EID value of the |
| | earliest event the SWID-PV wishes to have |
| | reported. (Note - the report will be inclusive of |
| | the event with this EID value.) In the case where |
| | the SWID-PV is requesting an inventory, then this |
| | field MUST be 0. (0x00000000) In the case where |
| | this field is non-zero, the SWID-PV is requesting |
| | events and the SWID-PC MUST respond using a SWID |
| | Tag Events, SWID Tag Identifier Events, or a PA- |
| | TNC Error attribute. In the case where this field |
| | is zero, the SWID-PV is requesting an inventory |
| | and the SWID-PC MUST respond using a SWID Tag |
| | Inventory, a SWID Tag Identifier Inventory, or a |
| | PA-TNC Error attribute. |
| Tag Creator | A 2-byte unsigned integer indicating the length |
| Length | in bytes of the Tag Creator field. |
| Tag Creator | A string containing the Tag Creator RegID value |
| | from within a SWID tag. This field value MUST be |
| | normalized to Network Unicode format, as |
| | described in Section 4.7. This string MUST NOT |
| | be NULL terminated. |
| Unique | A 2-byte unsigned integer indicating the length |
| Software ID | in bytes of the Unique Software ID field. |
| Length | |
| Unique | A string containing the Unique ID value from |
| Software ID | within a SWID tag. This field value MUST be |
| | normalized to Network Unicode format, as |
| | described in Section 4.7. This string MUST NOT be |
| | NULL terminated. |
+---------------+---------------------------------------------------+
Table 5: SWID Request Attribute Fields
The SWID-PV sends the SWID Request attribute to a SWID-PC to request
the indicated information. Note that between the Result Type flag
and the Earliest EID field, the SWID-PC is constrained to a single
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possible SWID Response attribute type (or a PA-TNC Error attribute)
in its response to the request.
The Subscribe and Clear Subscription flags are used to manage
subscriptions for the requesting SWID-PV on the receiving SWID-PC.
Specifically, an attribute with the Subscribe flag set seeks to
establish a new subscription by the requesting SWID-PV to the given
SWID-PC, while an attribute with the Clear Subscription flag seeks to
delete all existing subscriptions by the requesting SWID-PV on the
given SWID-PC. Note that, in the latter case, only the subscriptions
associated with the Connection ID and, if available, the Posture
Validator ID of the requester are deleted as described in
Section 3.8.3. A newly established subscription has the parameters
outlined in the 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 tag identifiers (if present) indicate if and how a
subscription is targeted. In the case that the SWID-PC is unable or
unwilling to comply with the SWID-PV's request to establish or clear
subscriptions, the SWID-PC MUST respond with a PA-TNC Error attribute
with the SWID_SUBSCRIPTION_DENIED_ERROR error code. (Note that if
the SWID-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, as it is a request for an immediate
response from the SWID-PC in addition to setting up the subscription.
A SWID-PC 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 flag - the SWID-PC MUST
generate a response attribute without regard to the presence of this
flag in addition to clearing its subscription list.
Both the Subscribe and Clear Subscription flags MAY be set in a
single SWID Request attribute. In the case where this request is
successful, the end result MUST be equivalent to the SWID-PC clearing
its subscription list for the given SWID-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 the one that was just created.) In
the case that the requested actions are successfully completed, the
SWID-PC MUST respond with a SWID Response attribute. (The specific
type of SWID Response attribute depends on the Result Type and
Earliest EID fields, as described above.) In the case where there is
a failure that prevents some part this request from completing, the
SWID-PC MUST NOT add a new subscription, MUST NOT clear the old
subscriptions, and the SWID-PC MUST respond with a PA-TNC Error
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attribute. In other words, the SWID-PC MUST NOT partially succeed at
implementing such a request; either both actions succeed, or neither
succeed.
The Earliest EID field is used to indicate whether the SWID-PV is
requesting an inventory or event list from the SWID-PC. A value of 0
(0x00000000) represents a request for inventory information.
Otherwise, the SWID-PV is requesting event information. For Earliest
EID values other than 0, the SWID-PC's response MUST respond with
event records, as described in Section 3.6. Note that the request
does not identify a particular EID Epoch, since responses can only
include events in the SWID-PC's current EID Epoch.
The Tag ID Count indicates the number of tag identifiers in the
attribute. This number might be any value between 0 and 16,777,216,
inclusive. A single tag identifier is represented by four fields:
Tag Creator Length, Tag Creator, Unique Software ID Length, and
Unique Software ID. The two length fields are used to indicate the
number of bytes allocated to their corresponding string field. The
two string fields, Tag Creator and Unique Software ID, contain copies
of the SWID tag's Tag Creator RegID and Unique ID values,
respectively, converted and normalized to Network Unicode format, as
described in Section 4.7. Note that there is no field to indicate a
particular Instance ID. Thus, targeted requests request all
instances of the indicated SWID tags. The presence of one or more
tag identifiers is used by the SWID-PV to indicate a targeted
request, which seeks only inventories of or events affecting SWID
tags corresponding to the given identifiers. The SWID-PC MUST only
respond with tags that match the tag identifier structures provided
in the SWID-PVs SWID Request attribute (as described in
Section 3.3.3) and MUST include all instances of matching tags in its
response.
4.10. SWID Tag Identifier Inventory
A SWID-PC sends this attribute to a SWID-PV to convey a list of the
endpoint's SWID tags expressed using SWID tag identifier instances.
This list might represent a complete inventory or a targeted list of
tags, depending on the parameters in the SWID-PV's request. A SWID-
PV MUST NOT send this attribute. The SWID-PC either sends this
attribute in fulfillment of an existing subscription where the
establishing request has a Result Type of 1 and the Earliest EID is
zero, or in direct response to a SWID Request attribute where the
Result Type is 1 and the Earliest EID is zero.
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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 | Tag ID Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag Creator Length | Tag Creator (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unique Software ID Length |Unique Software ID (var length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID Length | Instance ID (var length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: SWID Tag Identifier Inventory Attribute
+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Flags: Bit 0 | In the case that this attribute is sent in |
| - | fulfillment of a subscription this bit MUST be set |
| Subscription | (1). In the case that this attribute is a direct |
| Fulfillment | response to a SWID Request, this bit MUST be unset |
| | (0). |
| Flags: Bit | Reserved for future use. This field MUST be set to |
| 1-7 - | zero on transmission and ignored upon reception. |
| Reserved | |
| Tag ID Count | The number of tag identifier instances that |
| | follow. This field is an unsigned integer. The Tag |
| | Creator Length, Tag Creator, Unique Software ID |
| | Length, Unique Software ID, Instance ID Length, |
| | and Instance ID fields are repeated, in order, the |
| | number of times indicated in this field. This |
| | field value MAY be 0, in which case there are no |
| | instances of these fields. |
| Request ID | In the case where this attribute is in direct |
| Copy / | response to a SWID Request attribute from a SWID- |
| Subscription | PV, this field MUST contain an exact copy of the |
| ID | Request ID field from that SWID Request. In the |
| | case where this attribute is sent in fulfillment |
| | of an active subscription, this field MUST contain |
| | the Subscription ID of the subscription being |
| | fulfilled by this attribute. |
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| EID Epoch | The EID Epoch of the Last EID value. This field is |
| | an unsigned 4-byte integer. |
| Last EID | The EID of the last event recorded by the SWID-PC, |
| | or 0 if the SWID-PC has no recorded events. This |
| | field is an unsigned 4-byte integer. |
| Tag Creator | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Tag Creator field. |
| Tag Creator | A string containing the Tag Creator RegID value |
| | from within a SWID tag. This field value MUST be |
| | normalized to Network Unicode format, as described |
| | in Section 4.7. This string MUST NOT be NULL |
| | terminated. |
| Unique | A 2-byte unsigned integer indicating the length in |
| Software ID | bytes of the Unique Software ID field. |
| Length | |
| Unique | A string containing the Unique ID value from |
| Software ID | within a SWID tag. This field value MUST be |
| | normalized to Network Unicode format, as described |
| | in Section 4.7. This string MUST NOT be NULL |
| | terminated. |
| Instance ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Instance ID field. |
| Instance ID | A string containing the Instance ID of a given tag |
| | instance. The exact value of this field depends on |
| | the party that provides this SWID tag. This field |
| | value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 6: SWID Tag 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 SWID
Request, the Subscription Fulfillment bit MUST be unset (0). Note
that the SWID response attribute sent in direct response to a SWID
Request that establishes a subscription (i.e., a subscription's
establishing request) MUST be treated as a direct response to that
SWID Request (and thus the Subscription Fulfillment bit is unset).
SWID 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 Tag ID Count field indicates the number of tag identifier
instances present in this inventory. Each tag identifier instance is
represented by a set of six fields: Tag Creator Length, Tag Creator,
Unique Software ID Length, Unique Software ID, Instance ID Length,
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and Instance ID. These six fields, collectively referred to as the
"Tag ID Fields", will appear once for each reported tag instance.
Note that an endpoint's SWID tag collection might contain multiple
instances of a single tag (i.e., multiple tag files with the same tag
identifier value). When this occurs, in the case where that tag is
reported, then the response MUST contain a set of Tag ID Fields for
each instance of that tag. (The tag might not be reported if the
SWID-PV made a targeted request that does not match that tag's tag
identifier.) For example, if an endpoint has three copies of tag X,
and the SWID-PV requests a full inventory, then the response is
required to include three sets of Tag ID Fields corresponding to the
three instances of that tag. Only the Instance ID fields are
different between these three instances.
When responding directly to a SWID Request attribute, the Request ID
Copy / Subscription ID field MUST contain an exact copy of the
Request ID field from that SWID Request. When this attribute is sent
in fulfillment of an existing subscription on this Posture Collector,
then 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 3.6 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, this field MUST contain 0. These fields can be
interpreted to indicate that the provided inventory (be it full or
targeted) reflects the record of events on the endpoint after all
changes up to and including this last event have been accounted for.
4.11. SWID Tag Identifier Events
A SWID-PC sends this attribute to a SWID-PV to convey events where
the affected SWID tags are expressed using SWID tag identifier
instances. A SWID-PV MUST NOT send this attribute. The SWID-PC
either sends this attribute in fulfillment of an existing
subscription where the establishing request has a Result Type is 1
and the Earliest EID is non-zero, or in direct response to a SWID
Request attribute where the Result Type is 1 and the Earliest EID is
non-zero.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Tag Creator Length |Tag Creator (v)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unique Software ID Length |Unique Software ID (var length)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID Length | Instance ID (var length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: SWID Tag Identifier Events Attribute
+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Flags: Bit 0 | In the case that this attribute is sent in |
| - | fulfillment of a subscription this bit MUST be set |
| Subscription | (1). In the case that this attribute is a direct |
| Fulfillment | response to a SWID Request, this bit MUST be unset |
| | (0). |
| Flags: Bit | Reserved for future use. This field MUST be set to |
| 1-7 - | zero on transmission and ignored upon reception. |
| Reserved | |
| Event Count | The number of events that are reported in this |
| | attribute. This field is a 3-byte unsigned |
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| | integer. The EID, Timestamp, Action, Tag Creator |
| | Length, Tag Creator, Unique Software ID Length, |
| | Unique Software ID, Instance ID Length, and |
| | Instance ID fields are repeated, in order, the |
| | number of times indicated in this field. (An |
| | instance of these nine fields is referred to as an |
| | "event record" in this attribute. Thus the Event |
| | Count field indicates the number of event |
| | records.) This field value MAY be 0, in which case |
| | there are no instances of these fields. |
| Request ID | In the case where this attribute is in direct |
| Copy / | response to a SWID Request attribute from a SWID- |
| Subscription | PV, this field MUST contain an exact copy of the |
| ID | Request ID field from that SWID Request. In the |
| | case where this attribute is sent in fulfillment |
| | of an active subscription, this field MUST contain |
| | the Subscription ID of the subscription being |
| | fulfilled by this attribute. |
| EID Epoch | The EID Epoch of the Last EID value. This field is |
| | an unsigned 4-byte integer. |
| Last EID | The EID of the last event recorded by the SWID-PC, |
| | or 0 if the SWID-PC has no recorded events. This |
| | field contains the EID of the SWID-PC's last |
| | recorded change event (which might or might not be |
| | included as an event record in this attribute). |
| Last | The EID of the last event record that was |
| Consulted | consulted when generating the event record list |
| EID | included in this attribute. This is different from |
| | the Last EID field value if and only if this |
| | attribute is conveying a partial list of event |
| | records. See Section 3.6.4 for more on partial |
| | list of event records. |
| EID | The EID of the event in this event record. |
| Timestamp | The timestamp associated with the event in this |
| | event record. This timestamps is the SWID-PC's |
| | best understanding of when the given event |
| | occurred. Note that this timestamp might be an |
| | estimate. The Timestamp date and time MUST be |
| | represented as an RFC 3339 [5] compliant ASCII |
| | string in Coordinated Universal Time (UTC) time |
| | with the additional restrictions that the 'T' |
| | delimiter and the 'Z' suffix MUST be capitalized |
| | and fractional seconds (time-secfrac) MUST NOT be |
| | included. This field conforms to the date-time |
| | ABNF production from section 5.6 of RFC 3339 |
| | [RFC3339] with the above restrictions. Leap |
| | seconds are permitted and SWID-PVs MUST support |
| | them. The Timestamp string MUST NOT be NULL |
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| | terminated or padded in any way. The length of |
| | this field is always 20 octets. |
| Action | The type of event that is recorded in this event |
| | record. Possible values are: 1 = CREATION - the |
| | addition of a tag to the endpoint's SWID tag |
| | collection; 2 = DELETION - the removal of a tag |
| | from the endpoint's SWID tag collection; 3 = |
| | ALTERATION - There was an alteration to a tag file |
| | within the endpoint's tag collection. All other |
| | values are reserved for future use and MUST NOT be |
| | used when sending attributes. In the case where a |
| | SWID-PV receives an event record that uses an |
| | action value other than the ones defined here, it |
| | MUST ignore that event record but SHOULD process |
| | other event records in this attribute as normal. |
| Tag Creator | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Tag Creator field of the tag affected |
| | by the described event. |
| Tag Creator | A string containing the Tag Creator RegID value |
| | from within the SWID tag affected by the described |
| | event. This field value MUST be normalized to |
| | Network Unicode format, as described in Section |
| | 4.7. This string MUST NOT be NULL terminated. |
| Unique | A 2-byte unsigned integer indicating the length in |
| Software ID | bytes of the Unique Software ID field of the tag |
| Length | affected by the described event. |
| Unique | A string containing the Unique ID value from |
| Software ID | within the SWID tag affected by the described |
| | event. This field value MUST be normalized to |
| | Network Unicode format, as described in Section |
| | 4.7. This string MUST NOT be NULL terminated. |
| Instance ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Instance ID field. |
| Instance ID | A string containing the Instance ID of a given tag |
| | instance. The exact value of this field depends on |
| | the party that provides this SWID tag. This field |
| | value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 7: SWID Tag Identifier Events Attribute Fields
The first few fields in the SWID Tag Identifier Events attribute
mirror those in the SWID Tag Identifier Inventory attribute. The
primary difference is that, instead of conveying an inventory using
tag identifier instances, the attribute conveys zero or more event
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records, including the EID, timestamp, action type, and tag
identifier instance of the affected tag.
With regard to the Timestamp field, it is important to note that
clock skew between the SWID-PC and SWID-PV as well as between
different SWID-PCs within an enterprise might make correlation of
timestamp values difficult. This specification does not attempt to
resolve clock skew issues, although other mechanisms outside of this
specification do exist to reduce the impact of clock skew and make
the timestamp more useful for such correlation. Instead, SWID
Message and Attributes for PA-TNC uses 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 SWID tag was removed and then subsequently re-added, one can
get an indication as to how long the system was without the given tag
(and, thus without the associated software). Since this will involve
comparison of timestamp values all originating on the same system,
clock skew between the SWID-PC and SWID-PV is not an issue. However,
if the SWID-PC's clock was adjusted between two recorded events, it
is possible for such a calculation to lead to incorrect
understandings of 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) the recipient MUST treat the EID ordering as
correct.
All event records in a Tag Identifier Events Attribute are required
to be part of the same EID Epoch. Specifically, all reported events
MUST have an EID from the same EID Epoch as each other, and which is
the same as the EID Epoch of the Last EID and Last Consulted EID
values. The SWID-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 3.6.4) this
field value will differ from that of the Last EID field; 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 SWID Tag 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 tag
identifier instance might appear multiple times in an attribute, such
as if multiple events involving the associated tag were being
reported.
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4.12. SWID Tag Inventory
A SWID-PC sends this attribute to a SWID-PV to convey a list of SWID
tags. A SWID-PV MUST NOT send this attribute. The SWID-PC either
sends this attribute in fulfillment of an existing subscription where
the establishing request had a Result Type of 0 and the Earliest EID
is zero, or in direct response to a SWID 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 | Tag Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID Length | Instance ID (var length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: SWID Tag Inventory Attribute
+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Flags: Bit 0 | In the case that this attribute is sent in |
| - | fulfillment of a subscription this bit MUST be set |
| Subscription | (1). In the case that this attribute is a direct |
| Fulfillment | response to a SWID Request, this bit MUST be unset |
| | (0). |
| Flags: Bit | Reserved for future use. This field MUST be set to |
| 1-7 - | zero on transmission and ignored upon reception. |
| Reserved | |
| Tag ID Count | The number of tags that follow. This field is a |
| | 3-byte unsigned integer. The Instance ID Length, |
| | Instance ID, Tag Length, and Tag fields are |
| | repeated, in order, the number of times indicated |
| | in this field. This field value MAY be 0 in which |
| | case there are no instances of these fields. |
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| Request ID | In the case where this attribute is in direct |
| Copy / | response to a SWID Request attribute from a SWID- |
| Subscription | PV, this field MUST contain an exact copy of the |
| ID | Request ID field from that SWID Request. In the |
| | case where this attribute is sent in fulfillment |
| | of an active subscription, this field MUST contain |
| | the Subscription ID of the subscription being |
| | fulfilled by this attribute. |
| EID Epoch | The EID Epoch of the Last EID value. This field is |
| | an unsigned 4-byte integer. |
| Last EID | The EID of the last event recorded by the SWID-PC, |
| | or 0 if the SWID-PC has no recorded events. This |
| | field is an unsigned 4-byte integer. |
| Instance ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Instance ID field. |
| Instance ID | A string containing the Instance ID of a given tag |
| | instance. The exact value of this field depends on |
| | the party that provides this SWID tag. This field |
| | value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
| Tag Len | This is a 4-byte unsigned integer indicating the |
| | length of the following SWID tag in bytes. |
| Tag | A SWID tag as a string. In the case where the |
| | original SWID tag is not expressed using UTF-8 |
| | encoding, it MUST be converted and normalized to |
| | Network Unicode format, as described in Section |
| | 4.7. However, in the case where the original SWID |
| | tag is expressed using UTF-8 encoding, the SWID |
| | tag MUST be copied to this field without |
| | modification, even if the original SWID tag does |
| | not conform fully to Network Unicode format. This |
| | string MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 8: SWID Tag Inventory Attribute Fields
The SWID Tag Inventory attribute contains some number of SWID tags.
Given that the size of tags can vary considerably, the length of this
attribute is highly variable and, if transmitting a complete
inventory, can be extremely large. Enterprises might wish to
constrain the use of SWID Tag Inventory attributes to targeted
requests to avoid over-burdening the network unnecessarily.
Note that the Instance ID is included in this attribute along with
the tag. This is because, unlike the Tag Creator RegID and Unique ID
fields that make up the tag identifier, the Instance ID cannot always
be extracted from fields within a SWID tag. As such, in order to be
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able to associate a tag file with a given tag identifier instance, it
is necessary to include the Instance ID value in the attribute.
When copying a SWID tag into the Tag field, conversion and
normalization of the character encoding happens if and only if the
source SWID tag does not use UTF-8 encoding. In the case where the
source SWID tag is expressed using an encoding other than UTF-8, then
that tag MUST be converted and normalized to use Network Unicode
format prior to its inclusion in the tag field. However, in the case
where the source SWID tag is expressed in UTF-8, the source tag MUST
be copied to the Tag field without conversion or normalization. This
is true even if the source SWID tag uses UTF-8 but is not fully
conformant with Network Unicode format. This is done because any
conversion or normalization of a full SWID tag is likely to break any
cryptographic signatures included in the SWID tag. As such,
conversion only happens to ensure a SWID tag is readable for the
recipient (by ensuring it always uses UTF-8), but is otherwise
avoided if possible. Recipients of this attribute can always be
assured that the Tag field uses UTF-8 format, but cannot depend on
full Network Unicode format compliance.
4.13. SWID Tag Events
A SWID-PC sends this attribute to a SWID-PV to convey a list of
events where the affected SWID tags are expressed using full tags. A
SWID-PV MUST NOT send this attribute. The SWID-PC either sends this
attribute in fulfillment of an existing subscription where the
establishing request has a Result Type of 0 and the Earliest EID is
non-zero, or in direct response to a SWID Request attribute where the
Result Type is 0 and the Earliest EID is non-zero.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Instance ID Length |Instance ID (v)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: SWID Tag Events Attribute
+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Flags: Bit 0 | In the case that this attribute is sent in |
| - | fulfillment of a subscription this bit MUST be set |
| Subscription | (1). In the case that this attribute is a direct |
| Fulfillment | response to a SWID Request, this bit MUST be unset |
| | (0). |
| Flags: Bit | Reserved for future use. This field MUST be set to |
| 1-7 - | zero on transmission and ignored upon reception. |
| Reserved | |
| Event Count | The number of events being reported in this |
| | attribute. This field is a 3-byte unsigned |
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| | integer. The EID, Timestamp, Action, Instance ID |
| | Length, Instance ID, Tag Length, and Tag fields |
| | are repeated, in order, the number of times |
| | indicated in this field. (An instance of these |
| | five fields is referred to as an "event record" in |
| | this attribute. Thus the Event Count field |
| | indicates the number of event records.) This field |
| | value MAY be 0, in which case there are no |
| | instances of these fields. |
| Request ID | In the case where this attribute is in direct |
| Copy / | response to a SWID Request attribute from a SWID- |
| Subscription | PV, this field MUST contain an exact copy of the |
| ID | Request ID field from that SWID Request. In the |
| | case where this attribute is sent in fulfillment |
| | of an active subscription, this field MUST contain |
| | the Subscription ID of the subscription being |
| | fulfilled by this attribute. |
| EID Epoch | The EID Epoch of the Last EID value. This field is |
| | an unsigned 4-byte integer. |
| Last EID | The EID of the last event recorded by the SWID-PC, |
| | or 0 if the SWID-PC has no recorded events. This |
| | field contains the EID of the SWID-PC's last |
| | recorded change event (which might or might not be |
| | included as an event record in this attribute). |
| Last | The EID of the last event record that was |
| Consulted | consulted when generating the event record list |
| EID | included in this attribute. This is different from |
| | the Last EID field value if and only if this |
| | attribute is conveying a partial list of event |
| | records. See Section 3.6.4 for more on partial |
| | list of event records. |
| EID | The EID of the event in this event record. |
| Timestamp | The timestamp associated with the event in this |
| | event record. This timestamps is the SWID-PC's |
| | best understanding of when the given event |
| | occurred. Note that this timestamp might be an |
| | estimate. The Timestamp date and time MUST be |
| | represented as an RFC 3339 [5] compliant ASCII |
| | string in Coordinated Universal Time (UTC) time |
| | with the additional restrictions that the 'T' |
| | delimiter and the 'Z' suffix MUST be capitalized |
| | and fractional seconds (time-secfrac) MUST NOT be |
| | included. This field conforms to the date-time |
| | ABNF production from section 5.6 of RFC 3339 |
| | [RFC3339] with the above restrictions. Leap |
| | seconds are permitted and SWID-PVs MUST support |
| | them. The Timestamp string MUST NOT be NULL |
| | terminated or padded in any way. The length of |
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| | this field is always 20 octets. |
| Action | The type of event that is recorded in this event |
| | record. Possible values are: 1 = CREATION - the |
| | addition of a tag to the endpoint's SWID tag |
| | collection; 2 = DELETION - the removal of a tag |
| | from the endpoint's SWID tag collection; 3 = |
| | ALTERATION - There was an alteration to a tag file |
| | within the endpoint's tag collection. All other |
| | values are reserved for future use and MUST NOT be |
| | used when sending attributes. In the case where a |
| | SWID-PV receives an event record that uses an |
| | action value other than the ones defined here, it |
| | MUST ignore that event record but SHOULD process |
| | other event records in this attribute as normal. |
| Instance ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Instance ID field. |
| Instance ID | A string containing the Instance ID of a given tag |
| | instance. The exact value of this field depends on |
| | the party that provides this SWID tag. This field |
| | value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
| Tag Len | This is a 4-byte unsigned integer indicating the |
| | length of the following SWID tag in bytes. |
| Tag | A SWID tag as a string. In the case where the |
| | original SWID tag is not expressed using UTF-8 |
| | encoding, it MUST be converted and normalized to |
| | Network Unicode format, as described in Section |
| | 4.7. However, in the case where the original SWID |
| | tag is expressed using UTF-8 encoding, the SWID |
| | tag MUST be copied to this field without |
| | modification, even if the original SWID tag does |
| | not conform fully to Network Unicode format. This |
| | string MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 9: SWID Tag 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 SWID
Tag Inventory attribute, a SWID Tag 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 SWID
Request attributes only request full tags be sent (Result Type set to
0) in a targeted request, thus constraining the response just to tags
that match a given set of tag identifiers.
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As with the SWID Tag Identifier Events Attribute, this attribute MUST
only contain event records with EIDs coming from the current EID
Epoch of the SWID-PC.
As with the SWID Tag Inventory Attribute, the SWID-PC MUST perform
conversion and normalization of the SWID tag itself in the case where
the source SWID tag is expressed using an encoding other than UTF-8,
and MUST NOT perform conversion or normalization of the SWID tag
itself in the case where the source SWID tag is expressed using UTF-
8.
4.14. Subscription Status Request
A SWID-PV sends this attribute to a SWID-PC to request a list of
active subscriptions for which the requesting SWID-PV is the
subscriber. A SWID-PC MUST NOT send this attribute.
This attribute has no fields.
A SWID-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).
4.15. Subscription Status Response
A SWID-PC sends this attribute to a SWID-P to report the list of
active subscriptions for which the receiving SWID-PV is the
subscriber. A SWID-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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Tag ID Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Earliest EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag Creator Length | Tag Creator (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unique Software ID Length |Unique Software ID (var length)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Subscription Status Response Attribute
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+------------------+------------------------------------------------+
| Field | Description |
+------------------+------------------------------------------------+
| Flags: Bit 0-7 - | Reserved for future use. This field MUST be |
| Reserved | set to zero on transmission and ignored upon |
| | reception. |
| Subscription | The number of subscription records that |
| Record Count | follow. This field is a 3-byte unsigned |
| | integer. The Flags, Tag ID Count, Request ID, |
| | Earliest EID, Tag Creator Length, Tag Creator, |
| | Unique Software ID Length, and Unique Software |
| | ID fields are repeated, in order, the number |
| | of times indicated in this field. This field |
| | value MAY be 0 in which case there are no |
| | instances of these fields. |
| Flags, Tag ID | For each active subscription, these fields |
| Count, Request | contain an exact copy of the fields with the |
| ID, Earliest | same name as provided in the subscription's |
| EID, Tag Creator | establishing request. |
| Length, Tag | |
| Creator, Unique | |
| Software ID | |
| Length, and | |
| Unique Software | |
| ID | |
+------------------+------------------------------------------------+
Table 10: 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 SWID-PC MUST use the requester's
Connection ID and, if available, its Posture Validator ID to
determine which subscriptions are associated with the requester.
A SWID-PC MUST send a Subscription Status Response attribute in
response to a Subscription Status Request attribute. The only
exception to this is if the SWID-PC experiences an error condition
that prevents it from correctly populating the Subscription Status
Response attribute, in which case it MUST respond with a PA-TNC Error
attribute appropriate to the type of error experienced. If there are
no active subscriptions associated with the requesting party, the
Subscription Status Response attribute will consist of its Status
Flags field, a Subscription Record Count field with a value of 0, and
no additional fields.
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Each subscription record included in a Subscription Status Response
attribute duplicates the fields of a SWID 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 Tag ID Count field will be
non-zero and, within that subscription record, the Tag Creator
Length, Tag Creator, Unique Software ID Length, and Unique Software
ID fields are repeated, in order, the number of times indicated in
the Tag ID Count field. As such, each subscription record can be
different sizes. Likewise, if the establishing request is not
targeted (Tag ID Count field is 0), the subscription record has no
Tag Creator Length, Tag Creator, Unique Software ID Length, or Unique
Software ID fields.
When a SWID-PV compares the information received in a Subscription
Status Response to its own records of active subscriptions it should
be aware that the SWID-PC might be unable to distinguish this SWID-PV
from other SWID-PVs on the same NEA Server. As a result, it is
possible that the SWID-PC will report more subscription records than
the SWID-PV recognizes. For this reason, SWID-PVs SHOULD NOT
automatically assume that extra subscriptions reported in a
Subscription Status Response indicate a problem.
4.16. PA-TNC Error as Used by SWID Message and Attributes for PA-TNC
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 SWID
Message and Attributes for PA-TNC exchange. The latter case utilizes
error codes defined below.
A PA-TNC Error attribute is sent instead of a SWID Response attribute
due to factors that prevent the reliable creation of a SWID Response.
As such, a SWID-PC MUST NOT send both a PA-TNC Error attribute and a
SWID Response attribute in response to a single SWID Request
attribute.
Table 11 lists the Error Code values for the PA-TNC Error attribute
specific to the SWID Message and Attributes for PA-TNC exchange. In
all of these cases, the Error Code Vendor ID field MUST be set to
0x000000, corresponding to the IETF SMI Private Enterprise Number.
The Error Information structures for each error type are described in
the following subsections.
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Note that a message with a SWID Message and Attributes for PA-TNC
attribute might also result in an error condition covered by the
Standard PA-TNC Error Codes defined in PA-TNC. For example, the SWID
Attribute might have an invalid parameter, leading to an error code
of "Invalid Parameter". In this case, the SWID-PC MUST use the
appropriate PA-TNC Error Code value as defined in Section 4.2.8 of
PA-TNC specification.
+-----------------------+-------------------------------------------+
| Error Code Value | Description |
+-----------------------+-------------------------------------------+
| 0x00000020 | SWID_ERROR. This indicates a fatal error |
| | (i.e., an error that precludes the |
| | creation of a suitable response |
| | attribute) other than the errors |
| | described below but still specific to the |
| | processing of SWID Attributes. The |
| | Description field SHOULD contain |
| | additional diagnostic information. |
| 0x00000021 | SWID_SUBSCRIPTION_DENIED_ERROR. This |
| | indicates that the SWID-PC denied the |
| | SWID-PV's request to establish a |
| | subscription. The Description field |
| | SHOULD contain additional diagnostic |
| | information. |
| 0x00000022 | SWID_RESPONSE_TOO_LARGE_ERROR. This |
| | indicates that the SWID-PC's response to |
| | the SWID-PV's request was too large to be |
| | serviced. The error information structure |
| | indicates the largest possible size of a |
| | response supported by the SWID-PC (see |
| | Section 4.16.2). The Description field |
| | SHOULD contain additional diagnostic |
| | information. |
| 0x00000023 | SWID_SUBSCRIPTION_FULFILLMENT_ERROR. This |
| | indicates that the SWID-PC experienced an |
| | error fulfilling a given subscription. |
| | The error information includes the |
| | Subscription ID of the relevant |
| | subscription, as well as a sub-error that |
| | describes the nature of the error the |
| | SWID-PC experienced. The SWID-PC and |
| | SWID-PV MUST treat the identified |
| | subscription as cancelled. |
| 0x00000024 | SWID_SUBSCRIPTION_ID_REUSE_ERROR. This |
| | indicates that the SWID-PC received a |
| | SWID Request from a given SWID-PV where |
| | the Request ID of that SWID Request is |
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| | currently used as the Subscription ID of |
| | an active subscription with that SWID-PV. |
| | This error does not cancel the identified |
| | subscription. |
| 0x00000025-0x0000002F | RESERVED. These Error Codes are reserved |
| | for use by future revisions of the SWID |
| | Message and Attributes for PA-TNC |
| | specification. Any PA-TNC Error attribute |
| | using one of these Error Codes MUST be |
| | treated as indicating a fatal error on |
| | the sender without further |
| | interpretation. |
+-----------------------+-------------------------------------------+
Table 11: PA-TNC Error Codes for SWID Message and Attributes for PA-
TNC
The following subsections describe the structures present in the
Error Information fields.
4.16.1. SWID_ERROR, SWID_SUBSCRIPTION_DENIED_ERROR and
SWID_SUBSCRIPTION_ID_REUSE_ERROR Information
The SWID_ERROR error code indicates that the sender (the SWID-PC) has
encountered an error related to the processing of a SWID Request
attribute but which is not covered by more specific SWID error codes.
The SWID_SUBSCRIPTION_DENIED_ERROR is used when the SWID-PV requests
to establish a subscription or clear all subscriptions from the given
SWID-PV, but the SWID-PC is unable or unwilling to comply with this
request. The SWID_SUBSCRIPTION_ID_REUSE_ERROR is used when the SWID-
PC receives a SWID 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 13: SWID Error, Subscription Error, and Subscription ID Reuse
Information
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+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Copy of | In the case that this error condition is generated |
| Request ID / | in direct response to a SWID Request attribute, |
| Subscription | this field MUST contain an exact copy of the |
| ID | Request ID field in the SWID 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 SWID_ERROR as the |
| | other errors are not generated by subscription |
| | fulfillment.) Note that, in this case, the |
| | indicated error appears as a sub-error for a |
| | SWID_SUBSCRIPTION_FULFILLMENT_ERROR, as described |
| | in Section 4.16.3. |
| Description | A UTF-8 string describing the condition that |
| | caused this error. This field MAY be 0-length. |
| | However, senders SHOULD include some description |
| | in all PA-TNC Error attributes of these types. |
| | This field MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 12: SWID Error, Subscription Error, and Subscription ID Reuse
Information Fields
This error information structure is used with SWID_ERROR,
SWID_SUBSCRIPTION_DENIED_ERROR, and SWID_SUBSCRIPTION_ID_REUSE_ERROR
status codes to identify the SWID Request attribute that precipitated
the error condition and to describe the error. The Description field
contains text describing the error. The SWID-PC MAY encode machine-
interpretable information in this field, but SHOULD also include a
human-readable description of the error, since the receiving SWID-PV
might not recognize the SWID-PC's encoded information.
4.16.2. SWID_RESPONSE_TOO_LARGE_ERROR Information
The SWID_RESPONSE_TOO_LARGE_ERROR error code indicates that a
response generated by a SWID-PC in response to a SWID-PV's SWID
Request attribute was too large to send.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Allowed Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Description (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: SWID Response Too Large Error Information
+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Copy of | In the case that the attribute in question is |
| Request ID / | generated in direct response to a SWID Request, |
| Subscription | this field MUST contain an exact copy of the |
| ID | Request ID field in the SWID 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. Note that, in this |
| | case, the SWID_RESPONSE_TOO_LARGE_ERROR appears as |
| | a sub-error for a |
| | SWID_SUBSCRIPTION_FULFILLMENT_ERROR, as described |
| | in Section 4.16.3. |
| Maximum | This field MUST contain an unsigned integer |
| Allowed Size | indicating the largest permissible size, in bytes, |
| | of SWID Attribute that the SWID-PC is currently |
| | willing to send in response to a SWID Request |
| | attribute. |
| Description | A UTF-8 string describing the condition that |
| | caused this error. This field MAY be 0-length. |
| | However, senders SHOULD include some description |
| | in all PA-TNC Error attributes of these types. |
| | This field MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 13: SWID Response Too Large Error Information Fields
This error structure is used with the SWID_RESPONSE_TOO_LARGE_ERROR
status code to identify the SWID Request attribute that precipitated
the error condition and to describe the error. The Maximum Allowed
Size field indicates the largest attribute the SWID-PC is willing to
send in response to a SWID Request under the current circumstances.
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Note that under other circumstances, the SWID-PC might be willing to
return larger 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 SWID_ERROR and
SWID_SUBSCRIPTION_DENIED_ERROR information structure.
4.16.3. SWID_SUBSCRIPTION_FULFILLMENT_ERROR Information
The SWID_SUBSCRIPTION_FULFILLMENT_ERROR error code indicates that the
SWID-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) 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 Code Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub Error Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub Error Information (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: SWID Subscription Fulfillment Error Information
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+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Subscription | This field MUST contain the Subscription ID of the |
| ID | subscription whose fulfillment caused this error. |
| Reserved | This field MUST contain the value of the Reserved |
| | field of a PA-TNC Error attribute that describes |
| | the error condition encountered during |
| | subscription processing. |
| Sub Error | This field MUST contain the value of the Error |
| Code Vendor | Code Vendor ID field of a PA-TNC Error attribute |
| ID | that describes the error condition encountered |
| | during subscription processing. |
| Sub Error | This field MUST contain the value of the Error |
| Code | Code field of a PA-TNC Error attribute that |
| | describes the error condition encountered during |
| | subscription processing. |
| Sub Error | This field MUST contain the value of the Error |
| Information | Information field of a PA-TNC Error attribute that |
| | describes the error condition encountered during |
| | subscription processing. |
+--------------+----------------------------------------------------+
Table 14: SWID Subscription Fulfillment Error Information Fields
This error structure is used with the
SWID_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 of error that the SWID-
PC encountered while fulfilling the given subscription. The sub-
error MUST NOT have an error code of
SWID_SUBSCRIPTION_FULFILLMENT_ERROR.
The SWID-PC sending a PA-TNC Error attribute with this error code,
and the SWID-PV receiving it, MUST treat the subscription identified
by the Subscription ID field as cancelled. All other subscriptions
are unaffected.
5. Security Considerations
This section discusses some of the security threats facing Posture
Collectors and Posture Validators that implement the SWID Message and
Attributes for PA-TNC protocol. This section primarily notes
potential issues for implementers to consider, although it does
contain a handful of normative requirements to address certain
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security issues. Implementers need to make the final decision as to
how their implementations address the given issues. The issues
identified below focus on capabilities specific to this document.
Implementers are advised to consult other relevant NEA specifications
for security issues that are applicable to such components in
general.
Reading the Security Considerations section of any well-written
specification can be discouraging, as a long list of possible threats
is catalogued. Keep in mind that no security measure is absolute,
but each one can be beneficial. By understanding the weaknesses of
each security measure, we can put in place countermeasures to protect
against exploitation of these weaknesses.
5.1. Evidentiary Value of SWID Tags
A SWID tag is only indirect evidence as to the installation of a
piece of software on an endpoint. While the ideal is for the
presence of a tag to correspond to the presence of the corresponding
software, such a correlation hinges on software that accurately
manages individual tags as software is added and removed.
Utilization of the tests included in a tag's package_footprint and/or
validation elements can provide more direct evidence of software
presence, but this information might not be present in many tags and,
because of its limited support, this version of the SWID Message and
Attributes for PA-TNC specification does not support use of these
flags. Tags can include cryptographic signatures of some or all of
their fields, which can enable detection of field modification. This
is extremely useful in ensuring that sensitive fields are not
modified maliciously. However, the use of cryptographic signatures
is not required in SWID tags, and even when utilized, not all fields
will necessarily be protected by signatures. For these reasons, it
is important to treat SWID tags as evidence rather than proof of
software presence.
5.2. Integrity of the SWID Tag Collection
On a related note, while some systems might protect SWID tags against
modification, on others there might be very few restrictions on who
can add or delete tags on an endpoint. This can mean that a
malicious party has relatively free rein to add and remove tags with
the goal of obscuring the actual software inventory of the endpoint.
As noted above, signatures on tag files can keep tag modification
from going undetected, but an attacker can simply delete the signed
tag and replace it with a modified tag that lacks the associated
signature. In fact, even a signed tag can be added by an adversary
and go undetected if the tag does not include fields to verify
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software presence, such as the package_footprint or validation
element
There is little a SWID-PC can do to prevent unauthorized
modifications of the endpoint's SWID tag from occurring if the local
system does not provide protections for tags. Instead, the SWID-PV
and NEA Server need to operate with an awareness that this type of
modification can occur. The use of mechanisms to corroborate
software inventories can help detect malicious modification of an
endpoint's SWID tag collection. Likewise, the SWID-PV can look for
odd behavior such as the deletion and rapid re-installation of a
particular tag, especially the replacement of a signed tag with an
unsigned one. Parties that use SWID tags as evidence of compliance
with security policies need to be aware of the possible risks of
corruption of an endpoint's SWID tag collection.
5.3. Sensitivity of Collected Tags
Tags on an endpoint are generally not considered to be sensitive,
although there can be exceptions to this generalization as noted in
the section on Privacy Considerations. In general, an endpoint's
SWID tag collection can be browsed and individual tags read by any
party with access to the endpoint. This is generally not considered
to be problematic, as those with access to the endpoint can usually
learn of everything disclosed by that endpoint's tags simply by
inspecting other parts of the endpoint.
The situation changes when an endpoint's SWID tags are collected and
stored off of the endpoint itself, such as on a NEA Server or CMDB.
Tags represent a wealth of information about the endpoint in question
and, for an adversary who does not already have access to the
endpoint, a collection of the endpoint's tags might provide many
details that are useful for mounting an attack. A list of the tags
associated with an endpoint reveals a list of software installed on
the endpoint. This list is very detailed, generally noting specific
versions and even patch levels, which an adversary can use to
identify vulnerable software and design efficacious attacks.
In addition, other information might also be gleaned from a
collection of SWID tags:
o A SWID tag 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 A SWID tag 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.
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This information might be used as a starting point for the
development of supply chain attacks.
o Events affecting SWID tags 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 tag 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
necessary individuals and processes, and other basic security
precautions.
5.4. Integrity of Endpoint Records
SWID-PCs maintain records of detected changes to the endpoint's SWID
tag collection. These records are used to respond to a SWID-PV's
request for change events. The SWID-PV might use a list of reported
events to update its understanding of the endpoint's SWID tag
collection without needing to receive a full inventory report from
the SWID-PC. For this reason, preserving the integrity of the SWID-
PC's record of events is extremely important. If an attacker
modifies the SWID-PC's record of changes to the endpoint's SWID tag
collection, this might cause the SWID-PV's understanding of the
endpoint's SWID tag collection to differ from its actual state.
Results might include leading the SWID-PV to believe that absent
software was present, that present software was absent, that patches
have been installed even if this is not the case, or to be unaware of
other changes to SWID tags. As such, the SWID-PC MUST take steps to
protect the integrity of its event record.
In addition, sometimes a SWID-PC captures metadata about existing
tags or even creates copies of whole tags. Metadata might include
hash values of tag files or records of the last time a particular tag
file was modified, while whole tags might be preserved to record tags
that were deleted from the endpoint's SWID tag collection. If an
attacker is able to corrupt or modify this information, they might
cause a SWID-PC to fail to detect certain change events, incorrectly
report information, or otherwise fail to correctly fulfill SWID-PV
requests. As such, this additional information about SWID tags, if
collected, MUST be integrity protected.
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Finally, records of established SWID-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
SWID-PV, the SWID-PC might fail to correctly fulfill this
subscription. The SWID-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 SWID-PV
might collect a full inventory and realize from this that certain
events had not been correctly reported in accordance with an
established subscription. For this reason, the SWID-PC MUST protect
the integrity of subscription records.
5.5. SWID-PC Access Permissions
A SWID-PC requires sufficient permissions to locate and read SWID
tags on the endpoint that constitute the endpoint's SWID tag
collection, and 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. Depending on the operating environment
and other activities undertaken by a SWID-PC (or software that
incorporates a SWID-PC as one of its capabilities) additional
permissions might be required by the SWID-PC software. The SWID-PC
SHOULD NOT be granted permissions beyond what it needs in order to
fulfill its duties.
5.6. Sanitization of Tag Fields
In most cases there is no constraint on an endpoint as to who can add
tags. This open model allows applications that run in user space to
register tags as easily as more privileged applications. However,
this also means that any tool reading an endpoint's tags needs to
treat these tags as un-vetted input and employ appropriate
safeguards. In particular, tools that read SWID tags, including
SWID-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 tag.
Fields of a SWID tag that change the SWID-PC's behavior, alter system
state, or execute code need to be handled with special care. In
particular, the validation element, which provides a command line
that can nominally be executed to validate the tag's correctness, can
be utilized by an attacker to point to a malicious executable. To
defend against this, SWID-PCs MUST NOT execute an application
indicated by a validation element unless the element is signed and
the SWID-PC has determined that the signature is intact and trusted.
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5.7. Tag Library Poisoning
It can be useful for a SWID-PV to have access to a library of tags.
If the SWID-PV receives a list of tag identifier instances, it can
consult this library and collect full tags corresponding to those
identifiers. Assuming it does not need access to installation-
specific information, it can perform calculations on these full tags
as if it had received them from a SWID-PC. For example, it can use
this library to derive software names, publishers, and version by
finding the tag that corresponds to the given tag identifier value.
If the SWID-PV keeps a collection of full SWID tags for matching
against tag identifiers, there might be a temptation to add any
previously unknown tags that a SWID-PC might report to this library
automatically. In fact, this behavior can pose a security risk. If
the endpoint has been compromised and the tag manipulated on that
endpoint, the tag that it provides to the SWID-PV might be misleading
with regard to the software associated with this tag. If the SWID-PV
automatically adds this corrupted tag to its library, not only will
the computations with the compromised endpoint be affected, but
computations with other endpoints that provide tag identifier
instances that map to the corrupted tag will also be affected.
Instead, if the SWID-PV does make use of a tag library, it is
recommended to only populate that library with tags retrieved from a
trusted source, or at least to segregate collections of reported tags
by endpoint, so corrupted tags on one endpoint will not affect tag
computations involving other endpoints. In general, tags retrieved
from a trusted source and signed by a trusted authority are likely be
safe for inclusion in a tag library.
5.8. PA-TNC Security Threats
In addition to the aforementioned considerations the SWID Message and
Attributes for PA-TNC protocol is subject to the same security
threats as other PA-TNC transactions, as noted in 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.
6. Privacy Considerations
As noted in Section 5.3, 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 adequate safeguards are in
place to prevent exposure of collected tags. For similar reasons, it
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is advisable that an endpoint only send tags to a NEA Server that is
authorized to receive this information and that can be trusted to
safeguard this information after collection.
7. Relationship to Other Specifications
This specification makes frequent reference to and use of other
specifications. This section describes these relationships.
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, the SWID-
PC communicates with the endpoint's Posture Broker Client using IF-
IMC [IF-IMC], while the SWID-PV communicates with the NEA Server's
Posture Broker Server using IF-IMV [IF-IMV].
In addition, SWID 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 SWID
Message and Attributes for PA-TNC specification is able to convey a
broader query, resulting in a more comprehensive set of evidence
regarding an endpoint's installed software. Moreover, because this
specification makes use of the well-defined structures in SWID tags,
it is able to convey information that is more concise (by making use
of specific identifier fields instead of sending the whole SWID tag)
and/or more comprehensive (as the SWID structures contain many more
fields than expressible in PA-TNC). As such, this specification
provides important capabilities not present in the PA-TNC
specification.
8. IANA Considerations
This section extends multiple existing IANA registries.
Specifically, it extends the PA-TNC Attribute Types and PA-TNC Error
Codes defined in the PA-TNC specification [RFC5792] and the PA-
Subtypes registry defined in the PB-TNC specification [RFC5793] and
extended in PA-TNC. This specification only adds values to these
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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.
8.1. Registry for PA-TNC Attribute Types
Section 4.6 of this specification defines several new PA-TNC
attributes. The following values are added to the registry for PA-
TNC Attribute Types defined in the PA-TNC specification. Note that
Table 4 in Section 4.6 lists these attributes but uses a hexadecimal
value to identify their associated integer. The integer values given
in that table are identical to those provided here. Note also that
Table 4 includes an entry for PA-TNC Error attributes, but the IANA
information associated with that attribute is already defined in the
PA-TNC specification and is not reproduced here.
+-----+---------+----------------------+----------------------------+
| PEN | Integer | Name | Defining Specification |
+-----+---------+----------------------+----------------------------+
| 0 | 17 | SWID Request | SWID Message and |
| | | | Attributes for PA-TNC |
| 0 | 18 | SWID Tag Identifier | SWID Message and |
| | | Inventory | Attributes for PA-TNC |
| 0 | 19 | SWID Tag Identifier | SWID Message and |
| | | Events | Attributes for PA-TNC |
| 0 | 20 | SWID Tag Inventory | SWID Message and |
| | | | Attributes for PA-TNC |
| 0 | 21 | SWID Tag Events | SWID Message and |
| | | | Attributes for PA-TNC |
| 0 | 22 | Subscription Status | SWID Message and |
| | | Request | Attributes for PA-TNC |
| 0 | 23 | Subscription Status | SWID Message and |
| | | Response | Attributes for PA-TNC |
| 0 | 24 | Subscription Status | SWID Message and |
| | | Response | Attributes for PA-TNC |
| 0 | 25 - 31 | Reserved for future | SWID Message and |
| | | use | Attributes for PA-TNC |
+-----+---------+----------------------+----------------------------+
8.2. Registry for PA-TNC Error Codes
Section 4.16 of this specification defines several new PA-TNC Error
Codes. The following values are added to the registry for PA-TNC
Error Codes defined in the PA-TNC specification. Note that Table 11
in Section 4.16 lists these attributes but uses a hexadecimal value
to identify their associated integer. The integer values given in
that table are identical to those provided here.
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+----+---------+------------------------------------+---------------+
| PE | Integer | Name | Defining |
| N | | | Specification |
+----+---------+------------------------------------+---------------+
| 0 | 32 | SWID_ERROR | SWID Message |
| | | | and |
| | | | Attributes |
| | | | for PA-TNC |
| 0 | 33 | SWID_SUBSCRIPTION_DENIED_ERROR | SWID Message |
| | | | and |
| | | | Attributes |
| | | | for PA-TNC |
| 0 | 34 | SWID_RESPONSE_TOO_LARGE_ERROR | SWID Message |
| | | | and |
| | | | Attributes |
| | | | for PA-TNC |
| 0 | 35 | SWID_SUBSCRIPTION_FULFILLMENT_ERRO | SWID Message |
| | | R | and |
| | | | Attributes |
| | | | for PA-TNC |
| 0 | 36 | SWID_SUBSCRIPTION_ID_REUSE_ERROR | SWID Message |
| | | | and |
| | | | Attributes |
| | | | for PA-TNC |
| 0 | 37-47 | Reserved for future use | SWID Message |
| | | | and |
| | | | Attributes |
| | | | for PA-TNC |
+----+---------+------------------------------------+---------------+
8.3. Registry for PA Subtypes
Section 4.1 of this specification defines one new PA Subtype. The
following value is added to the registry for PA Subtypes defined in
the PB-TNC specification.
+-----+---------+----------------+----------------------------------+
| PEN | Integer | Name | Defining Specification |
+-----+---------+----------------+----------------------------------+
| 0 | 9 | SWID | SWID Message and Attributes for |
| | | Attributes | PA-TNC |
+-----+---------+----------------+----------------------------------+
9. References
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9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<http://www.rfc-editor.org/info/rfc3339>.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<http://www.rfc-editor.org/info/rfc5198>.
[RFC5209] Sangster, P., Khosravi, H., Mani, M., Narayan, K., and J.
Tardo, "Network Endpoint Assessment (NEA): Overview and
Requirements", RFC 5209, DOI 10.17487/RFC5209, June 2008,
<http://www.rfc-editor.org/info/rfc5209>.
[RFC5792] Sangster, P. and K. Narayan, "PA-TNC: A Posture Attribute
(PA) Protocol Compatible with Trusted Network Connect
(TNC)", RFC 5792, DOI 10.17487/RFC5792, March 2010,
<http://www.rfc-editor.org/info/rfc5792>.
[SWID] The International Organization for Standardization/
International Electrotechnical Commission, "Information
Technology - Software Asset Management - Part 2: Software
Identification Tag, ISO/IEC 19770-2", November 2009.
9.2. Informative References
[IF-IMC] Trusted Computing Group, "TNC IF-IMC version 1.3",
February 2013.
[IF-IMV] Trusted Computing Group, "TNC IF-IMV version 1.4", August
2013.
[NIST-SWID]
The National Institute of Standards and Technology and The
MITRE Corporation, "Guidelines for the Creation of
Interoperable Software Identification (SWID) Tags", August
2013.
[RFC5793] Sahita, R., Hanna, S., Hurst, R., and K. Narayan, "PB-TNC:
A Posture Broker (PB) Protocol Compatible with Trusted
Network Connect (TNC)", RFC 5793, DOI 10.17487/RFC5793,
March 2010, <http://www.rfc-editor.org/info/rfc5793>.
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[RFC6876] Sangster, P., Cam-Winget, N., and J. Salowey, "A Posture
Transport Protocol over TLS (PT-TLS)", RFC 6876,
DOI 10.17487/RFC6876, February 2013,
<http://www.rfc-editor.org/info/rfc6876>.
[RFC7171] Cam-Winget, N. and P. Sangster, "PT-EAP: Posture Transport
(PT) Protocol for Extensible Authentication Protocol (EAP)
Tunnel Methods", RFC 7171, DOI 10.17487/RFC7171, May 2014,
<http://www.rfc-editor.org/info/rfc7171>.
Appendix A. Examples
This appendix includes examples of a SWID tag file and SWID
attributes. All examples represent fictional content. Examples are
provided using the 2009 release of the ISO/IEC SWID specification.
A.1. A Simple SWID Tag
Figure 16 shows an example SWID tag for a fictional software product
called SomeApp created by Vendor Inc. This example includes only the
required SWID tag fields. This tag is for version 2.3, build 12 of
the product.
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1]<?xml version="1.0" encoding="UTF-8"?>
2]<swid:software_identification_tag
3] xmlns:swid="http://standards.iso.org/iso/19770/-2/2009/schema.xsd"
4] xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
5] <swid:entitlement_required_indicator>
6] true
7] </swid:entitlement_required_indicator>
8] <swid:product_title>SomeApp</swid:product_title>
9] <swid:product_version>
10] <swid:name>2.3 r12</swid:name>
11] <swid:numeric>
12] <swid:major>2</swid:major>
13] <swid:minor>3</swid:minor>
14] <swid:build>12</swid:build>
15] <swid:review>0</swid:review>
16] </swid:numeric>
17] </swid:product_version>
18] <swid:software_creator>
19] <swid:name>Vendor Inc.</swid:name>
20] <swid:regid>regid.2013-06.com.vendor</swid:regid>
21] </swid:software_creator>
22] <swid:software_licensor>
23] <swid:name>Vendor Inc.</swid:name>
24] <swid:regid>regid.2013-06.com.vendor</swid:regid>
25] </swid:software_licensor>
26] <swid:software_id>
27] <swid:unique_id>
28] someapp-21ec2020-3aea-1069-a2dd-08002b30309d
29] </swid:unique_id>
30] <swid:tag_creator_regid>
31] regid.2013-06.com.vendor
32] </swid:tag_creator_regid>
33] </swid:software_id>
34] <swid:tag_creator>
35] <swid:name>Vendor Inc.</swid:name>
36] <swid:regid>regid.2013-06.com.vendor</swid:regid>
37] </swid:tag_creator>
38]</swid:software_identification_tag>
Figure 16: A Simple SWID Tag
The SWID tag described in Figure 16 is limited to only the
information required by the SWID specification [SWID]. This
information includes the following:
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o Lines 5-7: Entitlement requirement indicator. This indicates
whether some sort of entitlement (e.g., a license) is required in
order to install and/or use the software.
o Line 8: Prose name of the product
o Lines 9-17: Product version. This includes both a prose
expression of the full product version and the version information
broken down into distinct fields.
o Lines 18-21: Software creator identification. This identifies the
party that created the software. This includes both a prose name
of the software creator and their "regid" value.
o Lines 22-25: Software licensor identification. This identifies
the party that holds the rights to license others to use the
software.
o Lines 26-33: Software unique identifier. This structure contains
the regid for the party that created this tag and a value that
party uses to uniquely identify the named software product. The
SWID Message and Attributes for PA-TNC specification uses the
values of these fields when constructing a SWID tag identifier, as
described in Section 3.3.
o Lines 34-37: Tag creator identification. This identifies the
party that created the tag.
Assume the SWID tag file is installed on the file system in the
following location:
C:\ProgramData\Vendor\regid.2013-06.com.vendor_someapp-21ec2020-3aea-
1069.swidtag
A.2. SWID Request Attributes
Below are hexadecimal dumps of example SWID Request attributes. SWID
Request attributes are described in more detail in Section 4.7.
A.2.1. Simple Request
This is a basic SWID request for inventory information - the request
is not targeted nor does the request establish a subscription on the
endpoint. The SWID Request dictates that the response be expressed
using SWID tag identifier instances.
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+-------------+-----------------------------------------------------+
| 20 00 00 00 | Clear Subscriptions = 0 (don't clear |
| | subscriptions), Subscribe = 0 (don't establish a |
| | new subscription), Result Type = 1 (respond using |
| | SWID tag identifier instances), Tag ID Count = 0 |
| | (non-targeted request) |
| ----------- | |
| 00 00 3a 76 | Request ID = 14966 |
| ----------- | |
| 00 00 00 00 | Earliest EID = 0 (respond with inventory rather |
| | than event records) |
+-------------+-----------------------------------------------------+
Note that this attribute does not contain any Tag Creator Length, Tag
Creator, Unique Software ID Length, or Unique Software ID fields
because the Tag ID Count field is 0.
A.2.2. Subscription Request for Events
This attribute establishes a request for a new subscription that will
report new SWID change events as they occur.
+-------------+-----------------------------------------------------+
| 60 00 00 00 | Clear Subscriptions = 0 (don't clear |
| | subscriptions), Subscribe = 1 (establish a new |
| | subscription), Result Type = 1 (respond using SWID |
| | tag identifier instances), Tag ID Count = 0 (non- |
| | targeted request) |
| ----------- | |
| 00 00 3a 76 | Request ID = 14967 |
| ----------- | |
| 00 02 cc 3a | Earliest EID = 183354 |
+-------------+-----------------------------------------------------+
As before, this attribute does not contain any Tag Creator Length,
Tag Creator, Unique Software ID Length, or Unique Software ID fields
because the Tag ID Count field is 0. The immediate response to this
message (assuming no errors are encountered) will be a list of events
with EIDs that are greater than or equal to 183354. Thereafter, if
any new events are recorded, those events (and only those events)
will be sent back to the SWID-PV in fulfillment of this subscription.
(See Section 3.8.2 for more on subscription fulfillment.)
A.2.3. Targeted Request
This example shows a targeted request. Specifically, the request
includes two SWID tag identifiers. The attribute requests that the
corresponding full SWID tags be returned.
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+-----------------+-------------------------------------------------+
| 00 00 00 02 | Clear Subscriptions = 0 (don't clear |
| | subscriptions), Subscribe = 0 (don't establish |
| | a new subscription), Result Type = 0 (respond |
| | using full SWID tags), Tag ID Count = 2 |
| | (targeted request identifying two SWID tags) |
| ----------- | |
| 00 00 3a 76 | Request ID = 14968 |
| ----------- | |
| 00 00 00 00 | Earliest EID = 0 (respond with inventory rather |
| | than event records) |
| =========== | START TAG IDENTIFIER 1 |
| 00 18 | Tag Creator Length = 24 |
| ----------- | |
| 72 65 67 69 64 | Tag Creator = regid.2013-06.com.vendor |
| 2e 32 30 31 33 | |
| 2d 30 36 2e 63 | |
| 6f 6d 2e 76 65 | |
| 6e 64 6f 72 | |
| ----------- | |
| 00 2c | Unique Software ID Length = 44 |
| ----------- | |
| 73 6f 6d 65 61 | Unique Software ID = |
| 70 70 2d 32 31 | someapp-21ec2020-3aea-1069-a2dd-08002b30309d |
| 65 63 32 30 32 | |
| 30 2d 33 61 65 | |
| 61 2d 31 30 36 | |
| 39 2d 61 32 64 | |
| 64 2d 30 38 30 | |
| 30 32 62 33 30 | |
| 33 30 39 64 | |
| =========== | START TAG IDENTIFIER 2 |
| 00 18 | Tag Creator Length = 24 |
| ----------- | |
| 72 65 67 69 64 | Tag Creator = regid.2013-06.com.vendor |
| 2e 32 30 31 33 | |
| 2d 30 36 2e 63 | |
| 6f 6d 2e 76 65 | |
| 6e 64 6f 72 | |
| ----------- | |
| 00 2f | Unique Software ID Length = 47 |
| ----------- | |
| 61 6e 6f 74 68 | Unique Software ID = |
| 65 72 61 70 70 | anotherapp-23a52020-3aea-1069-a2dd-0800884d4e21 |
| 2d 32 33 61 35 | |
| 32 30 32 30 2d | |
| 33 61 65 61 2d | |
| 31 30 36 39 2d | |
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| 61 32 64 64 2d | |
| 30 38 30 30 38 | |
| 38 34 64 34 65 | |
| 32 31 | |
+-----------------+-------------------------------------------------+
This message contains SWID tag identifiers for two SWID tags. The
first of these tags is the example SWID tag described in
Appendix A.1. The second tag is created by the same tag creator, but
indicates a different software product.
A.3. SWID Response Attributes
This section contains examples of SWID response attributes.
A.3.1. SWID Tag Identifier Events Attribute
This shows an example of a SWID Tag Identifier Events attribute. In
this case, this attribute is sent in fulfillment of an established
subscription rather than in direct response to a SWID Request
attribute. (This is indicated by setting the Subscription
Fulfillment flag.) The SWID Request attribute shown in
Appendix A.2.2 established this subscription (as indicated by the
Subscription ID field).
This response contains two event records.
+-------------------+-----------------------------------------------+
| 80 00 00 02 | Subscription Fulfillment = 1, Event Count = 2 |
| ----------- | |
| 00 00 3a 76 | Subscription ID = 14968 |
| ----------- | |
| 7e 82 1c aa | EID Epoch = 2122456234 |
| ----------- | |
| 00 02 cc 84 | Last EID = 183428 |
| ----------- | |
| 00 02 cc 84 | Last Consulted EID = 183428 (Same as Last EID |
| | so this is a complete result) |
| =========== | START EVENT RECORD 1 |
| 00 02 cc 83 | EID = 183427 |
| ----------- | |
| 32 30 31 33 2d 30 | Timestamp = 2013-07-21T04:32:16Z |
| 37 2d 32 31 54 30 | |
| 34 3a 33 32 3a 31 | |
| 36 5a | |
| ----------- | |
| 01 | Action = 1 (CREATION) |
| ----------- | |
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| 00 18 | Tag Creator Length = 24 |
| ----------- | |
| 72 65 67 69 64 2e | Tag Creator = regid.2013-06.com.vendor |
| 32 30 31 33 2d 30 | |
| 36 2e 63 6f 6d 2e | |
| 76 65 6e 64 6f 72 | |
| ----------- | |
| 00 2c | Unique Software ID Length = 44 |
| ----------- | |
| 73 6f 6d 65 61 70 | Unique Software ID = |
| 70 2d 32 31 65 63 | someapp-21ec2020-3aea-1069-a2dd-08002b30309d |
| 32 30 32 30 2d 33 | |
| 61 65 61 2d 31 30 | |
| 36 39 2d 61 32 64 | |
| 64 2d 30 38 30 30 | |
| 32 62 33 30 33 30 | |
| 39 64 | |
| ----------- | |
| 00 51 | Instance ID Length = 81 |
| ----------- | |
| 43 3a 5c 50 72 6f | Instance ID = |
| 67 72 61 6d 44 61 | C:\ProgramData\Vendor\regid.2013-06. |
| 74 61 5c 56 65 6e | com.vendor_someapp-21ec2020-3aea-1069.swidtag |
| 64 6f 72 5c 72 65 | |
| 67 69 64 2e 32 30 | |
| 31 33 2d 30 36 2e | |
| 63 6f 6d 2e 76 65 | |
| 6e 64 6f 72 5f 73 | |
| 6f 6d 65 61 70 70 | |
| 2d 32 31 65 63 32 | |
| 30 32 30 2d 33 61 | |
| 65 61 2d 31 30 36 | |
| 39 2e 73 77 69 64 | |
| 74 61 67 | |
| ============ | START EVENT RECORD 2 |
| 00 02 cc 84 | EID = 183428 |
| ----------- | |
| 32 30 31 33 2d 30 | Timestamp = 2013-07-21T04:32:22Z |
| 37 2d 32 31 54 30 | |
| 34 3a 33 32 3a 32 | |
| 32 5a | |
| ----------- | |
| 02 | Action = 2 (DELETED) |
| ----------- | |
| 00 18 | Tag Creator Length = 24 |
| ----------- | |
| 72 65 67 69 64 2e | Tag Creator = regid.2009-08.com.company |
| 32 30 30 39 2d 30 | |
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| 38 2e 63 6f 6d 2e | |
| 63 6f 6d 70 61 6e | |
| 79 | |
| ----------- | |
| 00 24 | Unique Software ID Length = 36 |
| ----------- | |
| 32 34 38 35 34 39 | Unique Software ID = |
| 37 35 2d 31 32 35 | 24854975-125e-ee3e-98ac-45684248eefa |
| 65 2d 65 65 33 65 | |
| 2d 39 38 61 63 2d | |
| 34 35 36 38 34 32 | |
| 34 38 65 65 66 61 | |
| ----------- | |
| 00 47 | Instance ID Length = 71 |
| ----------- | |
| 43 3a 5c 50 72 6f | Instance ID = C:\Program |
| 67 72 61 6d 20 46 | Files\Company\OurProduct\ |
| 69 6c 65 73 5c 43 | OurProduct_8749-84789200-02.swidtag |
| 6f 6d 70 61 6e 79 | |
| 5c 4f 75 72 50 72 | |
| 6f 64 75 63 74 5c | |
| 4f 75 72 50 72 6f | |
| 64 75 63 74 5f 38 | |
| 37 34 39 2d 38 34 | |
| 37 38 39 32 30 30 | |
| 2d 30 32 2e 73 77 | |
| 69 64 74 61 67 | |
+-------------------+-----------------------------------------------+
This response contains two event records. Note that their timestamps
indicate that they occurred a few seconds apart - some SWID-PCs might
choose to wait a brief time before sending messages in fulfillment of
subscriptions so as to send multiple event records in a single
attribute. The first event record indicates the creation of the SWID
tag shown in Appendix A.1. The second event record indicates the
deletion of a different SWID tag. Finally, note that since the Last
EID field is equal to the EID of one of the reported event records,
this indicates that the SWID-PC has no later recorded events.
A.3.2. SWID Tag Inventory Attribute
This shows an example of a SWID Tag Inventory attribute. In this
case, this attribute is being sent in direct response to a SWID
Request attribute, as indicated by the Subscription Fulfillment flag
being unset. (Specifically, it is being sent in response to the SWID
Request shown in Appendix A.2.3, as can be shown by comparing the
Request ID and Request ID Copy fields.) The result includes a single
tag entry.
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+-----------------------+-------------------------------------------+
| 00 00 00 01 | Subscription Fulfillment = 0, Tag Count = |
| | 1 |
| ----------- | |
| 00 00 3a 76 | Request ID Copy = 14968 |
| ----------- | |
| 7e 82 1c aa | EID Epoch = 2122456234 |
| ----------- | |
| 00 02 cc 84 | Last EID = 183428 |
| =========== | BEGIN TAG ENTRY |
| 00 51 | Instance ID Length = 81 |
| ----------- | |
| 43 3a 5c 50 72 6f 67 | Instance ID = |
| 72 61 6d 44 61 74 61 | C:\ProgramData\Vendor\regid.2013-06.com. |
| 5c 56 65 6e 64 6f 72 | vendor_someapp-21ec2020-3aea-1069.swidtag |
| 5c 72 65 67 69 64 2e | |
| 32 30 31 33 2d 30 36 | |
| 2e 63 6f 6d 2e 76 65 | |
| 6e 64 6f 72 5f 73 6f | |
| 6d 65 61 70 70 2d 32 | |
| 31 65 63 32 30 32 30 | |
| 2d 33 61 65 61 2d 31 | |
| 30 36 39 2e 73 77 69 | |
| 64 74 61 67 | |
| ----------- | |
| 05 ac | Tag Length = 1452 |
| ----------- | |
| 3c 3f 78 6d 6c 20 76 | The Tag field is equal to the SWID tag |
| ... 69 6f 6e 5f 74 | shown in Figure 16. Note that since the |
| 61 67 3e | original tag used UTF-8 encoding, the tag |
| | is copied without undergoing any |
| | conversion or normalization. |
+-----------------------+-------------------------------------------+
This attribute contains a single SWID tag. As a response to the
targeted SWID Request in Appendix A.2.3, this indicates a single
instance of the first requested SWID tag and no instances of the
second requested tag were present in the endpoint's SWID tag
collection. Moreover, if the same party receives both this attribute
and the attribute in Appendix A.3.1, one can tell that there have
been no change events recorded since the preceding message, because
the EID Epoch and Last EID values are unchanged.
Authors' Addresses
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Chris Coffin
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730
USA
Email: ccoffin@mitre.org
Daniel Haynes
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730
USA
Email: dhaynes@mitre.org
Charles Schmidt
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730
USA
Email: cmschmidt@mitre.org
Jessica Fitzgerald-McKay
Department of Defense
9800 Savage Road
Ft. Meade, Maryland
USA
Email: jmfitz2@nsa.gov
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