Software Message and Attributes for PA-TNC
draft-coffin-sacm-nea-swid-patnc-02
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Authors | Chris Coffin , Daniel Haynes , Charles Schmidt , Jessica Fitzgerald-McKay | ||
| Last updated | 2016-09-12 | ||
| Replaced by | draft-ietf-sacm-nea-swid-patnc | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-coffin-sacm-nea-swid-patnc-02
SACM C. Coffin
Internet-Draft D. Haynes
Intended status: Standards Track C. Schmidt
Expires: March 16, 2017 The MITRE Corporation
J. Fitzgerald-McKay
Department of Defense
September 12, 2016
Software Message and Attributes for PA-TNC
draft-coffin-sacm-nea-swid-patnc-02
Abstract
This document specifies the Software 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]).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on March 16, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Scope and Audience . . . . . . . . . . . . . . . . . . . 4
1.2. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1. Supported Use Cases . . . . . . . . . . . . . . . . . . . 7
2.1.1. Use Software Inventory as a Factor in Determining
Endpoint Access . . . . . . . . . . . . . . . . . . . 8
2.1.2. Maintain a Central Repository Reflecting an
Endpoint's Software Inventory . . . . . . . . . . . . 8
2.1.3. PA-TNC Use Cases . . . . . . . . . . . . . . . . . . 9
2.2. Non-supported Use Cases . . . . . . . . . . . . . . . . . 9
2.3. Specification Requirements . . . . . . . . . . . . . . . 10
2.4. Non-Requirements . . . . . . . . . . . . . . . . . . . . 11
2.5. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 11
2.6. Non-Assumptions . . . . . . . . . . . . . . . . . . . . . 12
2.7. Software Message and Attributes for PA-TNC Diagram
Conventions . . . . . . . . . . . . . . . . . . . . . . . 12
3. Software Message and Attributes for PA-TNC System
Requirements . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1. Basic Inventory Exchange . . . . . . . . . . . . . . . . 13
3.2. Software Identifiers . . . . . . . . . . . . . . . . . . 14
3.2.1. Record Identifiers . . . . . . . . . . . . . . . . . 15
3.2.2. Using Software and Record Identifiers in SW
Attributes . . . . . . . . . . . . . . . . . . . . . 16
3.3. Targeted Requests . . . . . . . . . . . . . . . . . . . . 16
3.4. Monitoring Changes in an Endpoint's Software Inventory
Evidence Collection . . . . . . . . . . . . . . . . . . . 17
3.5. Reporting Change Events . . . . . . . . . . . . . . . . . 19
3.5.1. Change Event Records . . . . . . . . . . . . . . . . 20
3.5.2. Updating Inventory Knowledge Based on Events . . . . 21
3.5.3. Using Event Records in SW Attributes . . . . . . . . 22
3.5.4. Partial and Complete Lists of Event Records in SW
Attributes . . . . . . . . . . . . . . . . . . . . . 22
3.5.5. Synchronizing Event Identifiers and Epochs . . . . . 24
3.6. Subscriptions . . . . . . . . . . . . . . . . . . . . . . 26
3.6.1. Establishing Subscriptions . . . . . . . . . . . . . 26
3.6.2. Managing Subscriptions . . . . . . . . . . . . . . . 27
3.6.3. Terminating Subscriptions . . . . . . . . . . . . . . 27
3.6.4. Subscription Status . . . . . . . . . . . . . . . . . 28
3.6.5. Fulfilling Subscriptions . . . . . . . . . . . . . . 28
3.6.5.1. Subscriptions Reporting Inventories . . . . . . . 30
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3.6.5.2. Subscriptions Reporting Events . . . . . . . . . 30
3.6.5.3. Targeted Subscriptions . . . . . . . . . . . . . 31
3.6.5.4. No Subscription Consolidation . . . . . . . . . . 32
3.6.5.5. Delayed Subscription Fulfillment . . . . . . . . 32
3.7. Multiple Sources of Software Inventory Evidence Records . 33
3.8. Error Handling . . . . . . . . . . . . . . . . . . . . . 34
4. Software Message and Attributes for PA-TNC Protocol . . . . . 36
4.1. PA Subtype (AKA PA-TNC Component Type) . . . . . . . . . 36
4.2. PB-TNC and PA-TNC Messages . . . . . . . . . . . . . . . 36
4.3. PA-TNC Attribute Header . . . . . . . . . . . . . . . . . 37
4.4. SW Attribute Overview . . . . . . . . . . . . . . . . . . 38
4.5. SW Attribute Exchanges . . . . . . . . . . . . . . . . . 40
4.6. Software Message and Attributes for PA-TNC Attribute
Enumeration . . . . . . . . . . . . . . . . . . . . . . . 42
4.7. Normalization of Text Encoding . . . . . . . . . . . . . 43
4.8. Request IDs . . . . . . . . . . . . . . . . . . . . . . . 44
4.9. SW Request . . . . . . . . . . . . . . . . . . . . . . . 45
4.10. Software Identifier Inventory . . . . . . . . . . . . . . 48
4.11. Software Identifier Events . . . . . . . . . . . . . . . 51
4.12. Software Inventory . . . . . . . . . . . . . . . . . . . 56
4.13. Software Events . . . . . . . . . . . . . . . . . . . . . 58
4.14. Subscription Status Request . . . . . . . . . . . . . . . 62
4.15. Subscription Status Response . . . . . . . . . . . . . . 62
4.16. PA-TNC Error as Used by Software Message and Attributes
for PA-TNC . . . . . . . . . . . . . . . . . . . . . . . 64
4.16.1. SW_ERROR, SW_SUBSCRIPTION_DENIED_ERROR and
SW_SUBSCRIPTION_ID_REUSE_ERROR Information . . . . . 66
4.16.2. SW_RESPONSE_TOO_LARGE_ERROR Information . . . . . . 68
4.16.3. SW_SUBSCRIPTION_FULFILLMENT_ERROR Information . . . 69
5. Supported Data Models . . . . . . . . . . . . . . . . . . . . 71
5.1. ISO 2015 SWID Tags using XML . . . . . . . . . . . . . . 71
5.1.1. Guidance on Normalizing Source Data to ISO 2015 SWID
Tags using XML . . . . . . . . . . . . . . . . . . . 72
5.1.2. Guidance on Creation of Software Identifiers from ISO
2015 SWID Tags . . . . . . . . . . . . . . . . . . . 72
5.2. ISO 2009 SWID Tags using XML . . . . . . . . . . . . . . 72
5.2.1. Guidance on Normalizing Source Data to ISO 2015 SWID
Tags using XML . . . . . . . . . . . . . . . . . . . 72
5.2.2. Guidance on Creation of Software Identifiers from ISO
2015 SWID Tags . . . . . . . . . . . . . . . . . . . 73
6. Security Considerations . . . . . . . . . . . . . . . . . . . 73
6.1. Evidentiary Value of Software Inventory Evidence Records 73
6.2. Sensitivity of Collected Records . . . . . . . . . . . . 74
6.3. Integrity of Endpoint Records . . . . . . . . . . . . . . 75
6.4. SW-PC Access Permissions . . . . . . . . . . . . . . . . 75
6.5. Sanitization of Record Fields . . . . . . . . . . . . . . 76
6.6. PA-TNC Security Threats . . . . . . . . . . . . . . . . . 76
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 76
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8. Relationship to Other Specifications . . . . . . . . . . . . 77
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 77
9.1. Registry for PA-TNC Attribute Types . . . . . . . . . . . 77
9.2. Registry for PA-TNC Error Codes . . . . . . . . . . . . . 78
9.3. Registry for PA Subtypes . . . . . . . . . . . . . . . . 79
9.4. Registry for Software Data Models . . . . . . . . . . . . 80
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 80
10.1. Normative References . . . . . . . . . . . . . . . . . . 80
10.2. Informative References . . . . . . . . . . . . . . . . . 80
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 81
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. Such information can come from multiple sources,
including tag files (such as ISO SWID tags [SWID], reports from third
party inventory tools, output from package managers, and other
sources. The attributes defined in this document are used to
communicate software inventory evidence, collected from a range of
possible sources, from the posture collector on the endpoint to the
posture validator on a NEA Server using the PA-TNC interface, as
shown in Figure 1 below.
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+-------------+ +--------------+
| Posture | <--------PA--------> | Posture |
| Collectors | | Validators |
| (1 .. N) | | (1 .. N) |
+-------------+ +--------------+
| |
| |
| |
+-------------+ +--------------+
| Posture | | Posture |
| Broker | <--------PB--------> | Broker |
| Client | | Server |
+-------------+ +--------------+
| |
| |
+-------------+ +--------------+
| Posture | | Posture |
| Transport | <--------PT--------> | Transport |
| Client | | Server |
| (1 .. N) | | (1 .. N) |
+-------------+ +--------------+
NEA CLIENT NEA SERVER
Figure 1: NEA Reference Model
This specification defines a new set of PA-TNC attributes, carried
over PA-TNC messages, which are used to communicate requests for
software information and software events, and for conveying that
information back to a NEA Server.
Possession of a list of an endpoint's installed software 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, reported software inventory lists can be used to
indicate compliance or non-compliance with these requirements.
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. All of these uses make an understanding of an
endpoint's software 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
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requirements common to PA-TNC interfaces as defined in RFC 5792
[RFC5792].
This document is based on standards published by the Trusted
Computing Group's Trusted Network Communications (TNC) workgroup.
The TNC and NEA architectures are interoperable and the following
components are equivalent:
+---------------------------------------+-----------------------+
| 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
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.
SW-PC - A Posture Collector (PC) that conforms to this specification.
Note that such a posture collector might also support other PA-TNC
exchanges beyond Software Message and Attributes for PA-TNC.
SW-PV - A Posture Validator (PV) that conforms to this specification.
Note that such a posture verifier might also support other PA-TNC
exchanges beyond Software Message and Attributes for PA-TNC.
SW Attribute - This is a PA-TNC attribute (as defined in RFC 5792
[RFC5792] extension for conveying software inventory information.
This specification defines several new attribute types.
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Endpoint's Software Inventory Evidence Collection - The set of
information regarding the set of software installed on an endpoint
and expressed using one of the Software Message and Attributes data
models, as described in the Software Data Model IANA table (see
Section 9.4. An endpoint's software inventory evidence collection
might include information created by or derived from multiple
sources, including but not limited to SWID tag files deposited on the
file system during software installation, information generated to
report output from software discovery tools, and information
dynamically generated by a software or package management system on
an endpoint.
Software Inventory Evidence Record - The endpoint's Software
Inventory Evidence Collection is composed of "records". Each record
corresponds to one installed instance of a particular software
product as reported by some data source. It is possible for a single
installed instance to have multiple software inventory evidence
records in an endpoint's Software Inventory Evidence Collection -
this can happen if multiple sources all report the same software
installation instance.
Software Identifier - A string associated with a specific version of
a specific software product. Each supported Software Message and
Attributes for PA-TNC data model has its own rules for how a Software
Identifier (see Section 3.2) is derived from the representation of
the given software product using that data model, and different
sources for this information might populate relevant information
differently. As such, while each Software Identifier uniquely
identifies a specific software product, the same software product
might be associated with multiple Software Identifiers reflecting
differences between different information sources and supported data
models.
2. Background
2.1. Supported Use Cases
This section describes the Software Message and Attributes for PA-TNC
use cases supported by this specification. The primary use of
exchanging software inventory information over the PA-TNC interface
is to enable a challenger (e.g. NEA Server) to obtain inventory
evidence about some system in a way that conforms to NEA procedures
and expressed using a standard format. Collected software
information 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.
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2.1.1. 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.
Software Message and Attributes for PA-TNC facilitates policy
decisions that consider an endpoint's software inventory by providing
the NEA Server with software inventory information from the endpoint.
The SW-PC can provide a complete or partial inventory to the SW-PV as
required to determine policy compliance. The SW-PV can then use this
as evidence of compliance or non-compliance with enterprise policy.
2.1.2. 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.
Software Message and Attributes for PA-TNC supports this activity
through a number of mechanisms. As noted above, it allows a SW-PC to
provide a complete list of software present in an endpoint's Software
Inventory Evidence Collection to the SW-PV, which can then pass this
information on to a central repository such as a Configuration
Management Database (CMDB) or similar application. In addition, SW-
PCs are required to be able to monitor for changes to an endpoint's
Software Inventory Evidence Collection in near real-time and push
reports of changes to the SW-PV as soon as those changes are
detected. Thus any central repository fed by a SW-PV receiving such
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information can be updated soon after the change occurs. Keeping
such a central repository synchronized with the state of each
endpoint's Software Inventory Evidence Collection allows tools that
use this information for their own security activities to make
decisions in a consistent, efficient manner.
2.1.3. PA-TNC Use Cases
Software 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.
2.2. Non-supported Use Cases
Some use cases not covered by this version of Software Message and
Attributes for PA-TNC include:
o This specification does not address how the endpoint's Software
Inventory Evidence Collection is populated. In particular, NEA
components are not expected to perform software discovery
activities beyond compiling information in an endpoint's Software
Inventory Evidence Collection. This collection might potentially
come from multiple sources on the endpoint (e.g., information
generated dynamically by package management tools or discovery
tools, as well as SWID tag files discovered on the file system).
While an enterprise might make use of software discovery
procedures to identify installed software 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 standard
format used in the messages described in this specification.
Instead, it focuses exclusively on defining interfaces for the
transportation of software information 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 software information based on
arbitrary software properties. For example, requesting only
information about software from a particular vendor is not
supported. After the endpoint's software inventory evidence
collection has been copied to some central location, such as the
CMDB, processes there can perform queries based on any criteria
present in the collected information, but this specification does
not address using such queries to constrain the initial collection
of this information from the endpoint.
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o This specification does not address utilization of properties of
certain sources of software information that might facilitate
local tests (i.e., on the endpoint) of endpoint state. For
example, the optional package_footprint field of an ISO SWID tag
can contain a list of files and hash values associated with the
software indicated by the tag. Tools on the endpoint can use the
values in this field to test for the presence of the indicated
files. Successful evaluation of such tests leads to greater
assurance that the indicated software is present on the endpoint.
Currently, most SWID tag creators do not provide values for tag
fields that support local testing. For this reason, the added
complexity of supporting endpoint testing using these fields is
out of scope for this specification. Future versions of this
specification might add support for such testing.
2.3. Specification Requirements
Below are the requirements that the Software 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 Software 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 Scalable
Software 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.
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o Interoperable
This specification defines the protocol for how PCs and PVs can
exchange and use software information to provide a NEA Server with
information about an endpoint's software inventory. Therefore a key
goal for this specification is ensuring that all SW 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 outlines 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 software inventory evidence 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 software inventory evidence
collection throughout the entire interval when it was not connected.
2.4. Non-Requirements
There are certain requirements that the Software Message and
Attributes for PA-TNC specification explicitly is not required to
meet. This list is not exhaustive.
o End to End Confidentiality
This specification does not define 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 8 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.
2.5. Assumptions
Here are the assumptions that Software 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
Attributes sent between the SW 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.
2.6. Non-Assumptions
The Software Message and Attributes for PA-TNC specification
explicitly does not assume:
o Authenticity and Accuracy of the Software Inventory Evidence
Collection with Regard to Endpoint Inventory
This specification makes no assumption as to whether the software
information that it reports correctly reflect the 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
reported Software Inventory Evidence Collection to the NEA Server.
Similarly, this specification makes no assumption with regard to the
completeness of the Software Inventory Evidence Collection's coverage
of the total set of software installed on the endpoint. It is
possible, and even likely, that some installed software is not
represented by a record in an endpoints Software Inventory Evidence
Collection. See Section 6 for more on this security consideration.
2.7. Software Message and Attributes for PA-TNC Diagram Conventions
This specification defines the syntax of the Software 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).
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3. Software Message and Attributes for PA-TNC System Requirements
The Software Message and Attributes for PA-TNC specification
facilitates the exchange of software inventory and event information.
Specifically, each application supporting Software Message and
Attributes for PA-TNC includes a component known as the SW-PC that
receives messages sent with the SW Attributes component type. The
SW-PC is also responsible for sending appropriate SW Attributes back
to the SW-PV in response. This section outlines what software
inventories and events are and the requirements on SW-PCs and SW-PVs
in order to support the stated use cases of this specification.
3.1. Basic Inventory Exchange
In the most basic exchange supported by this specification, a SW-PV
sends a request to the SW-PC requesting all inventory information in
the endpoint's Software Inventory Evidence Collection. This simple
exchange is shown in Figure 2.
+-------------+ +--------------+
| SW-PC | | SW-PV | Time
+-------------+ +--------------+ |
| | |
|<--------------SW Request----------------| |
| | |
|---------------SW Response-------------->| |
| | V
Figure 2: Basic SW Message Exchange
Upon receiving such a SW Request from the SW-PV, the SW-PC is
expected to collect all inventory information from the endpoint's
software evidence collection and place it within its response
attribute.
SW-PVs MUST discard without error any SW Response attributes that
they receive for which they do not know the SW Request parameters
that led to this SW Response. This is due to the fact that the SW
Request includes parameters that control the nature of the response
(as will be described in the following sections) and without knowing
those parameters the SW Response cannot be reliably interpreted.
Most often receiving an unsolicited SW Response attribute happens
when a NEA Server has multiple SW-PVs; one SW-PV sends a SW Request
but, unless exclusive delivery is used by the SW-PC in sending the
response, both SW-PVs receive copies of the resulting SW Response.
In this case, the SW-PV that didn't send the SW Request would lack
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the context necessary to correctly interpret the SW Response it
received and would simply discard it. Note, however, that
proprietary measures might allow a SW-PV to discover the SW Request
parameters for a SW Response even if that SW-PV did not send the
given SW Request. As such, there is no blanket requirement for a SW-
PV to discard all SW Responses to SW Request the SW-PV did not
generate itself, only that SW-PVs are required to discard SW
Responses for which they cannot get the necessary context to
interpret.
In the case that it is possible to do so, the SW-PC SHOULD send its
SW Response attribute to the SW-PV that requested it using exclusive
delivery as described in section 4.5 of RFC 5793 (PB-TNC) [RFC5793].
Exclusive delivery ensures that only the sender of the SW Request
receives the resulting SW Response.
3.2. Software Identifiers
Software information records contain a large amount of descriptive
information about installed software products. However, in many
cases the complete level of detail in these records is not necessary.
For example, if one is simply tracking the installation or removal of
known software products, one only needs enough information to
recognize the software added or removed. To allow such uses to be
efficiently supported, Software Message and Attributes for PA-TNC
supports the use of Software Identifiers.
A Software Identifier uniquely identifies a specific version of a
specific software product. The Software Message and Attributes for
PA-TNC specification does not dictate the structure of a Software
Identifier (beyond stating that it is a string) or define how it is
created. Instead, each data model described in the Software Data
Model IANA table (Section 9.4 includes its own rules for how a
Software Identifier is created based on a record in the Endpoint's
Software Inventory Evidence Collection expressed in that data model.
Within the Software Message and Attributes for PA-TNC specification,
the Software Identifier is simply an opaque string.
Software Identifiers allow SW Response messages to identify software
to a server at a fraction of the bandwidth that would be needed to
send the entire associated record. For some combinations of data
models and sources, the full record might never be necessary as the
identifier can be directly correlated to the contents of the full
record. This is possible with authoritative SWID tags, since these
tags always have the same contents and thus a Software Identifier
derived from these tags can be used as a lookup to a local copy of
the full tag. For other combinations of source and data model, a
server might not be able to determine the specific software product
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and version associated with the identifier without requesting deliver
of the full record. In either case, however, a SW-PV can use
Software Identifiers to track the presence of specific software
products on an endpoint over time in a bandwidth-efficient manner.
There are two important limitations of Software Identifiers to keep
in mind:
The identifiers do not necessarily change when the associated
record changes. In some situations, a record in the endpoint's
Software Inventory Evidence Collection will change due to new
information becoming available or in order to correct prior errors
in that information. Such changes might or might not result in
changes to the Software Identifier, depending on the nature of the
changes and the rules governing how Software Identifiers are
derived from records of the appropriate data model.
It is possible that a single software product is installed on a
single endpoint multiple times. If both of these installation
instances are reported by the same source using the same data
format, then this will result in identical Software Identifiers
for each installation instances. In other words, Software
Identifiers do not uniquely identify installation instances; they
just uniquely identify software products (which might have more
than one installation instance). Instead, to distinguish between
multiple instances of a single software product, one needs to make
use of Record Identifiers, described in the following section.
3.2.1. Record Identifiers
A Record Identifier is a string generated by the SW-PC that is
uniquely associated with a specific record within the Endpoint's
Software Inventory Evidence Collection. The SW-PC MUST assign a
unique identifier to each record when it is added to the Endpoint's
Software Inventory Evidence Collection. The Record Identifier SHOULD
remain unchanged if that record is modified. The SWID-PC might wish
to assign Record Identifiers sequentially, but any scheme is
acceptable provided that no two records receive the same identifier.
Servers can use Record Identifiers to distinguish between multiple
instances of a single software product installed on an endpoint.
Since each installation instance of a software product is associated
with a separate record, servers can use the record identifier to
distinguish between instances. For example, if an event is reported
(as described in Section 3.5), the record identifier will allow the
server to discern which instance of a software product is involved.
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3.2.2. Using Software and Record Identifiers in SW Attributes
A SW Attribute reporting an endpoint's Software Inventory Evidence
Collection can contain Software Identifiers instead of copies of
software inventory evidence records. The message exchange is
identical to the diagram shown in Figure 2, but the contents of the
SW Response are Software Identifiers instead of evidence records.
The SW Request attribute indicates whether the response is required
to use full records or Software Identifiers. Using Software
Identifiers can reduce the attribute size of the response by multiple
orders of magnitude when compared to sending the same inventory using
full records. A SW-PC responds to a SW Request attribute requesting
Software Identifiers the same way it responds to a request for full
software records, except that instead of copying each record entirely
into the attribute body of the response, it provides the specific
values that comprise a Software Identifier for each record.
All SW Response attributes include Record Identifiers for each
reported record. This is true regardless of whether the record is
delivered in full or represented by a Software Identifier.
3.3. Targeted Requests
Sometimes a SW-PV does not require information about every piece of
software on an endpoint but only needs to receive updates about
certain software instances. For example, enterprise endpoints might
be required to have certain software products installed and to keep
these updated. Instead of requesting a complete inventory just to
see if these products are present, the SW-PV can make a "targeted
request" for the software in question.
Targeted requests follow the same message exchange described in
Figure 2. The SW-PV targets its request by providing one or more
Software Identifiers in its SW Request attribute. The SW-PC MUST
then limit its response to contain only records that match the
indicated Software Identifier(s). This allows the network exchange
to exclude information that is not relevant to a given policy
question, thus reducing unnecessary bandwidth consumption. The SW-
PC's response might consist of full records or of Software
Identifiers, depending on the parameters of the SW Request.
Note that targeted requests identify the software relevant to the
request only through Software Identifiers. This specification does
not support arbitrary, parameterized querying of records. For
example, one cannot request all records from a certain software
publisher, or all records created by a particular record source.
Targeted requests only allow a requestor to request specific software
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(as identified by their Software Identifiers) and receive a response
that is limited to the named software.
There is no assumption that a SW-PC will recognize "synonymous
records" - that is, records from different sources for the same
software. Recall that different sources and data models may use
different Software Identifier strings for the same software product.
The SW-PC returns only records that match the Software Identifiers in
the SW Request, even if there might be other records in the
endpoint's Software Inventory Evidence Collection for the same
software product. This is necessary because SW-PCs might not have
the ability to determine that two Software Identifiers refer to the
same product.
Targeted requests do not include Record Identifiers. The response to
a targeted request MUST include all records associated with the named
Software Identifiers, including the case where there are multiple
records associated with a single Software Identifier.
SW-PCs MUST accept targeted requests and process them correctly as
described above. SW-PVs MUST be capable of making targeted requests
and processing the responses thereto.
3.4. Monitoring Changes in an Endpoint's Software Inventory Evidence
Collection
The software collection on an endpoint is not static. As software is
installed, uninstalled, patched, or updated, the Software Inventory
Evidence Collection is expected to change to reflect the new software
state on the endpoint. Different record sources might update the
evidence collection at different rates. For example, a package
manager might update its records in the Software Inventory Evidence
Collection immediately whenever it is used to add or remove a
software product. By contrast, sources that perform periodic
examination of the endpoint would likely only update their records in
the Software Inventory Evidence Collection after each examination.
All SW-PCs MUST be able to be able to detect changes to the Software
Inventory Evidence Collection. Specifically, SW-PCs MUST be able to
detect:
o The creation of records
o The deletion of records
o The alteration of records
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An "alteration" is anything that modifies the contents of a record
(or would modify it, if the record is dynamically generated on
demand) in any way, regardless of whether the change is functionally
meaningful.
SW-PCs MUST detect such changes to the endpoint's Software Inventory
Evidence Collection in close to real-time (i.e., within seconds) when
the Posture Collector is operating. In addition, in the case where
there is a period during which the SW-PC is not operating, the SW-PC
MUST be able to determine the net change to the endpoint's Software
Inventory Evidence Collection over the period it was not operational.
Specifically, the "net change" represents the difference between the
state of the endpoint's Software Inventory Evidence Collection when
the SW-PC was last operational and monitoring its state, and the
state of the endpoint's software inventory evidence collection when
the SW-PC resumed operation. Note that a net change might not
reflect the total number of change events over this interval. For
example, if a record was altered three times during a period when the
SW-PC was unable to monitor for changes, the net change of this
interval might only note that there was an alteration to the record,
but not how many individual alteration events occurred. It is
sufficient for a SW-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 SW-PC MUST assign a time to each detected change in the
endpoint's Software Inventory Evidence Collection. These timestamps
correspond to the SW-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 Software Inventory Evidence Collection
that occur while the SW-PC is operating, the SW-PC ought to be able
to assign a time to the event that is accurate to within a few
seconds. For changes to the endpoint's Software Inventory Evidence
Collection that occur while the SW-PC is not operational, upon
becoming operational the SW-PC needs to make a best guess as to the
time of the relevant events (possibly by looking at timestamps on
files), but these values might be off. In the case of dynamically
generated records, the time of change is the time at which the data
from which the records are generate changes, not the time at which a
changed record is generated. For example, if records are dynamically
generated based on data in an RPM database, the time of change would
be when the RPM record was changed.
With regard to deletions of records, the SW-PC needs to detect the
deletion and MUST retain a copy of the full deleted record along with
its Record Identifier so that the record itself can be provided to
the SW-PV upon request. This copy of the record MUST be retained for
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a reasonable amount of time. Vendors and administrators determine
what "reasonable" means, but a copy of the record SHOULD be retained
for as long as the event recording the deletion of the record remains
in the SW-PC's event log (as described in Section 3.5). This is
recommended because, as long as the event is in the SW-PC's change
logs, the SW-PC might send an event attribute (described in
Section 3.5) that references this record, and a copy of the record is
needed if the SW-PV wanted a full copy of the relevant records.
With regard to alterations to a record, SW-PCs MUST detect any
alterations to the contents of a record. Alterations need to be
detected even if they have no functional impact on the record. A
good guideline is that any alteration to a record that might change
the value of a hash taken on the record's contents needs to be
detected by the SW-PC. A SW-PC might be unable to distinguish
modifications to the content of a record from modifications to the
metadata the file system associates with the record. For example, a
SW-PC might use the "last modification" timestamp as an indication of
alteration to a given record, but a record's last modification time
can change for reasons other than modifications to the record
contents. A SW-PC is still considered compliant with this
specification if it also reports metadata change events that do not
change the record itself as alterations to the record. In other
words, while SW-PC authors are encouraged to exclude modifications
that do not affect the bytes within the record, discriminating
between modifications to file contents and changes to file metadata
can be difficult and time consuming on some systems. As such, as
long as the alterations detected by a SW-PC always cover all
modifications to the contents of record, the SW-PC is considered
compliant even if it also registers alterations that do not modify
the contents of a record as well. When recording an alteration to a
record, the SW-PC is only required to note that an alteration
occurred. The SW-PC is not required to note or record how the record
altered, nor is it possible to include such details in SW Attributes
reporting the change to a SW-PV.
3.5. Reporting Change Events
As noted in the preceding section, SW-PCs MUST be able to detect
changes to the endpoints software inventory evidence collection
(creation, deletion, and alteration) in near real-time while the SW-
PC is operational, and MUST be able to account for any net change to
the endpoint's Software Inventory Evidence Collection that occurs
when the SW-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 Software Message and Attributes for PA-TNC, this is facilitated by
reporting change events. All SW-PCs MUST be capable of receiving
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requests for change events and sending change event attributes. All
SW-PVs MUST be capable of requesting and receiving change event
attributes.
3.5.1. Change Event Records
A change event record consists of either a complete record or
Software Identifier from the changed record along with the following
pieces of information:
o The nature of the change (i.e., creation, deletion, or lteration)
o An Event Identifier (EID) value
o An EID Epoch value
An EID is a 4-byte unsigned integer that the SW-PC assigns
sequentially to each observed event (whether detected in real-time or
deduced by looking for net changes over a period of SW-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 SW-PC and any SW-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 SW-PC reverted to an earlier
state (e.g., resetting it to factory defaults). In the case where a
SW-PC needs to reset its EID counter, either because it has exhausted
all available EID values or because the SW-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 SW-PC might not otherwise be able to determine
an ordering for events. In these cases, the SW-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 SW Request attribute indicates
that a SW-PV wants an inventory response rather than an event
response, while an EID of 0 in a SW Response is used to indicate the
initial state of the endpoint's Software Inventory Evidence
Collection prior to the observation of any events. Thus the very
first recorded event in a SW-PC's records within an EID Epoch MUST be
assigned a value of 1 or greater. Note that EID and EID Epoch values
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are assigned by the SW-PC without regard to whether events are being
reported to one or more SW-PVs. The SW-PC records events and assigns
EIDs during its operation. Any and all SW-PVs that request event
information from the SW-PC will have those requests served from the
same event records and thus will see the same EIDs and EID Epochs for
the same events.
The SW-PC MUST ensure there is no coverage gap (i.e., change events
that are not recorded in the SW-PC's records) in its change event
records. This is necessary because a coverage gap might give a SW-PV
a false impression of the endpoint's state. For example, if a SW-PV
saw an event indicating that a particular record had been added to
the endpoint's software inventory evidence collection, and saw no
subsequent events indicating that record had been deleted, it might
reasonably assume that this record was still present and thus that
the indicated software was still installed (assuming the Epoch has
not changed). If there is a coverage gap in the SW-PC's event
records, however, this assumption is false. For this reason, the SW-
PC's event records MUST NOT contain gaps. In the case where there
are periods where it is possible that changes occurred without the
SW-PC detecting or recording them, the SW-PC MUST either compute a
net change and update its event 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 SW-PC's Epoch changes, all of these associations between
EIDs and events are cancelled, and EID values once again become free
for assignment.
3.5.2. 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 SW-PC to a SW-PV (as described in
Section 3.1 through Section 3.3) includes the EID Epoch and EID of
the last event recorded prior to that inventory being compiled. This
allows the SW-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 software inventory evidence
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collection). Specifically, a SW-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 attribute describing these events indicates the nature
of the change, the affected records, and the order in which these
events occurred (as indicated by the sequential EIDs). Using this
information, any remote record of the endpoint's Software Inventory
Evidence Collection can be updated appropriately.
3.5.3. Using Event Records in SW Attributes
A SW-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 SW Request attribute, the SW-PV provides an EID other than 0. (A
value of 0 in these fields represents a request for an inventory.)
When the SW-PC receives such a request, instead of identifying
records from the endpoint's Software Inventory Evidence Collection,
it consults its list of detected changes. The SW-PC MUST add an
event record to the SW Response attribute for each recorded change
event with an EID greater than or equal to the EID in the SW Request
attribute (although targeting of requests, as described in the next
paragraph, might limit this list). A list of event records MUST only
contain events with EIDs that all come from the current Epoch.
SW-PVs can target requests for event records by including one or more
Software Identifiers, as described in Section 3.3, in the SW Request
that requests an event record list. A targeted request for event
records is used to indicate that only events affecting software that
match the provided Software Identifiers are to be returned.
Specifically, in response to a targeted request for event records,
the SW-PC MUST exclude any event records that are less than the
indicated EID (within the current EID Epoch) and exclude any event
records where the affected software does not match one of the
provided Software Identifiers. This might mean that the resulting
list of event records sent in the response attribute does not provide
a continuous sequence of EIDs. Both SW-PCs and SWIC-PVs MUST support
targeted request for event records.
3.5.4. Partial and Complete Lists of Event Records in SW Attributes
Over time, a SW-PC might record a large number of change events. If
a SW-PV requests all change events covering a large period of time,
the resulting SW Response attribute might be extremely large,
especially if the SW-PV is requesting the use of full records instead
of the use of Software Identifiers (as described in Section 3.2.2).
In the case that the resulting attribute is too large to send (either
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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 SW-PC) the SW-PC MAY send a partial list of event records back
to the SW-PV.
Generation of a partial list of events in a SW Response attribute
requires the SW-PC to identify a "consulted range" of EIDs. A
consulted range is the set of event records that are examined for
inclusion in the SW Response attribute and that are included in that
attribute if applicable. Recall that, if a SW Request is targeted,
only event records that involve the indicated software would be
applicable. (See Section 3.3 for more on Targeted Request.) If a
request is not targeted, all event records in the considered range
are applicable and included in the SW Response attribute.
The lower bound of the consulted range MUST be the EID provided in
the SW Request. (Recall that a SW Request indicates a request for
event records by providing a non-0 EID value in the SW Request. See
Section 3.5.3.) 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 SW Response attribute if it is applicable to the request. The
EID of this last event record is called the "Last Consulted EID".
The SW-PC chooses this Last Consulted EID based on the size of the
event record list it is willing to provide to the SW-PV.
A partial result list MUST include all applicable event records
within the consulted range. This means that for any applicable event
record (i.e., any event record in an un-targeted request, or an event
record associated with software matching a requested Software
Identifier in a targeted request) whose EID is greater than or equal
to the EID provided in the SW Request and whose EID is less than or
equal to the Last Consulted EID, that event record MUST be included
in the SW 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 SW Response attributes that convey event records (either using
full records or using Software Identifiers) include an Epoch, Last
EID, and Last Consulted EID field. The Last EID contains the EID of
the last event record known to the SW-PC at the time that the SW
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 SW Response attribute. Note that,
if responding to a targeted SW Request, the SW Response attribute
might not contain the event record whose EID matches the Last
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Consulted EID value. For example, the last consulted EID record
might have been deemed inapplicable because it did not match the
specified list of Software Identifiers in the SW Request.
If a SW-PV receives a SW Response attribute where the Last EID and
Last Consulted EID fields are identical, the SW-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 SW-PV has received a
partial result list. In the latter case, if the SW-PV wishes to try
to collect the rest of the partially delivered result list it then
sends a new SW Request whose EID is one greater than the Last
Consulted EID in the preceding response. Doing this causes the SW-PC
to generate another SW 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 SW
Response where the Last EID and Last Consulted EID are equal, the SW-
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 SW Request might specify an EID
that is greater than the EID of the last event recorded by a SW-PC.
In accordance with the behaviors described in Section 3.5.3, a SW-PC
MUST respond to such a request with a SW Response attribute of the
appropriate type (using full records or Software Identifiers as
specified in the SW Request) that contains zero event records. This
is because the SW-PC has recorded no event records with EIDs greater
than or equal to the EID in the SW Request. In such a case, the Last
Consulted EID field MUST be set to the same value as the Last EID
field in this SW Response attribute. This case is called out because
the consulted range on a SW-PC in such a situation is a negative
range, where the "first" EID in the range (provided in the SW
Request) is greater than the "last" EID in the range (this being the
EID of the last recorded event on the SW-PC). Implementers need to
ensure that SW-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.
3.5.5. Synchronizing Event Identifiers and Epochs
Since EIDs are sequential within an Epoch, if a SW-PV's list of event
records contains gaps in the EID values within a single Epoch, the
SW-PV knows that there are events that have not been accounted for.
The SW-PV can either request a new event list to collect the missing
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events or request a full inventory to re-sync its understanding of
the state of the Endpoint's Software Inventory Evidence Collection.
In either case, after the SW-PV's record of the endpoint's Software
Inventory Evidence Collection has been updated, the SW-PV can record
the new latest EID value and track events normally from that point
on.
If the SW-PV receives any attribute from a SW-PC where the EID Epoch
differs from the EID Epoch that was used previously, then SW-PV or
any entity using this information to track the endpoint's Software
Inventory Evidence 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 Software Inventory Evidence Collection, the SW-PV
needs to receive a full inventory from the endpoint. The SW-PV
cannot be brought in sync with the endpoint's state through the
collection of any set of event records in this situation. This is
because it is not possible to account for all events on the SW-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 SW-PV has
received a full inventory for the new Epoch, the SW-PV records the
latest EID reported in this new Epoch and can track further events
normally.
A SW-PC MUST NOT report events with EIDs from any Epoch other than
the current EID Epoch. The SW-PC MAY choose to purge all event
records from a previous Epoch from memory after an Epoch change.
Alternately, the SW-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 SW-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 SW-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 SW-PC.) A SW-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 SW-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 SW-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
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new EID Epoch MUST minimize the possibility that the newly generated
EID Epoch is the same as a previously used EID Epoch.
The SW-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 SW-PC has
suffered an error of some kind, possibly indicative of at least
partial corruption of its event log. In this case, the SW-PV SHOULD
treat the situation as if there was a change in Epoch and treat any
local copy of the endpoint's Software Inventory Evidence Collection
as out-of-sync until a full inventory can be reported by the SW-PC.
In this case, the SW-PV SHOULD flag the occurrence so the SW-PC can
be examined to ensure it is now operating properly.
3.6. Subscriptions
Thus far, all message exchanges discussed assume that a SW-PV sent an
SW Request attribute and the SW-PC is providing a direct response to
that request. The Software Message and Attributes for PA-TNC
specification also supports the ability for a SW-PC to send a message
with a SW Attribute to the SW-PV in response to observed changes in
the endpoint's software inventory evidence collection, instead of in
direct response to a SW Request. An agreement by a SW-PC to send
content when certain changes are detected to the endpoint's Software
Inventory Evidence Collection is referred to in this specification as
a "subscription", and the SW-PV that receives this content is said to
be "subscribed to" the given SW-PC. All SW-PCs and SW-PVs MUST
support the use of subscriptions.
3.6.1. Establishing Subscriptions
A SW-PV establishes a subscription on a particular SW-PC by sending a
SW Request attribute with the Subscription flag set. The SW Request
attribute is otherwise identical to the SW Requests discussed in
previous sections. Specifically, such a SW Request might request
full records or Software Identifiers, might be targeted, and might
request change event records or endpoint inventory. Assuming no
error is encountered, a SW-PC MUST send a SW Response attribute in
direct response to this SW Request attribute, just as if the
Subscription flag was not set. As such, the message exchange that
establishes a new subscription in a SW-PC has the same flow seen in
the previous message exchanges, as depicted in Figure 2. If the SW-
PV does not receive a PA-TNC Error attribute (as described in
Section 3.8 and Section 4.16) in response to their subscription
request, the subscription has been successfully established on the
SW-PC. The SW Request attribute that establishes a new subscription
is referred to as the "establishing request" for that subscription.
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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 SW-PC MUST have the ability to record and support multiple
simultaneous subscriptions from a single party and from multiple
parties. A SW-PV MUST have the ability to record and support
multiple simultaneous subscriptions to a single party and
subscriptions to multiple parties.
3.6.2. Managing Subscriptions
The SW-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. This identity includes both the
NEA Server's connection ID and the Posture Validator Identifier from
the PB-PA message that delivered the request.
Likewise, SW-PVs MUST record each accepted subscription for which
they are the subscribing party along with the associated Subscription
ID and the identity of the SW-PC that will be fulfilling the
subscription. The SW-PV needs to retain this information in order to
correctly interpret pushed SW Response attributes sent in fulfillment
of the subscription. The identity of the SW-PC is given in the
Posture Collector Identifier of the PB-PA message header in all
messages from that SW-PC.
3.6.3. Terminating Subscriptions
Subscriptions MAY be terminated at any time by the subscribing SW-PV
by setting the Clear Subscriptions flag in a SW Request. (See
Section 4.9 for more on using this flag.) In the case that a SW
Request with the Clear Subscriptions flag set is received the SW-PC
MUST only clear subscriptions that match both the NEA server
connection ID and the SW-PV ID for this SW Request, and MUST clear
all such subscriptions.
This specification does not give the SW-PV the ability to terminate
subscriptions individually - all subscriptions to the SW-PV are
cleared when the Clear Subscriptions flag is set.
This specification does not give the SW-PC the ability to
unilaterally terminate a subscription. However, if the SW-PC
experiences a fatal error fulfilling a subscription, resulting in
sending a PA-TNC Error attribute of type
SW_SUBSCRIPTION_FULFILLMENT_ERROR, then the subscription whose
fulfillment led to the error MUST be treated as terminated by both
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the SW-PC and the SW-PV. Only the subscription experiencing the
error is cancelled and other subscriptions are unaffected. See
Section 3.8 for more on this error condition.
Finally, a subscription is terminated if the connection between the
SW-PC and SW-PV is deleted. This occurs when the connection ID used
in the messages between the SW-PC and the SW-PV becomes unbound.
Loss of this connection ID would prevent the SW-PC from sending
messages in fulfillment of this subscription. As such, loss of the
connection ID necessarily forces subscription termination between the
affected parties.
3.6.4. Subscription Status
A SW-PV can request that a SW-PC report the list of active
subscriptions where the SW-PV is the subscriber. A SW-PV can use
this to recover lost information about active subscriptions. A SW-PV
can also use this capability to verify that a SW-PC has not forgotten
any of its subscriptions. The latter is especially useful where a
SW-PC does not send any attributes in fulfillment of a given
subscription for a long period of time. The SW-PV can check the list
of active subscriptions on the SW-PC and verify whether the
inactivity is due to a lack of reportable events, or due to the SW-PC
forgetting its obligations to fulfill a given subscription.
A SW-PV requests a list of its subscriptions on a given SW-PC by
sending that SW-PC a Subscription Status Request. The SW-PC MUST
then respond with a Subscription Status Response (or a PA-TNC Error
if an error condition is experienced). The Subscription Status
Response MUST contain one subscription record for each of the active
subscriptions for which the SW-PV is the subscribing party.
3.6.5. Fulfilling Subscriptions
As noted in Section 3.4 SW-PCs MUST have the ability to automatically
detect changes to an endpoint's Software Inventory Evidence
Collection in near real-time. For every active subscription, the SW-
PC MUST send an attribute to the subscribed SW-PV whenever a change
is detected to relevant records within the endpoint's Software
Inventory Evidence Collection. Such an attribute is said to be sent
"in fulfillment of" the given subscription and any such attribute
MUST include that subscription's Subscription ID. If the
establishing request for that subscription was a targeted request,
then only records that match the Software Identifiers provided in
that establishing request are considered relevant. Otherwise, (i.e.,
for non-targeted requests) any record is considered relevant for this
purpose. Figure 3 shows a sample message exchange where a
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subscription is established and then later messages are sent from the
SW-PC in fulfillment of the established subscription.
+-------------+ +--------------+
| SW-PC | | SW-PV | Time
+-------------+ +--------------+ |
| | |
|<-----------SW Request-------------| |
| | |
|------------SW Response----------->| |
| | |
. . .
. . .
. . .
<Change Event>| | |
|------------SW Response----------->| |
| | |
. . .
. . .
. . .
<Change Event>| | |
|------------SW 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 software indicated using Software
Identifiers, all attributes sent in fulfillment of this subscription
will also consist of event record lists expressed using Software
Identifiers. As such, all SW Responses displayed in the exchange
depicted in Figure 3 have the same format. A SW Response generated
in fulfillment of an active subscription MUST be a valid SW 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 SW-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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3.6.5.1. Subscriptions Reporting Inventories
In the case that a SW-PV subscribes to a SW-PC requesting an
inventory attribute whenever changes are detected (i.e. the EID in
the establishing request is 0), then the SW-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 record in a targeted request.) Upon detection of a
relevant change for an active subscription, the SW-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 records are likely to be present in each of these SW Attributes.
The role of an inventory subscription is not to report records just
for the items that changed - that is the role of a subscription that
reports events (see Section 3.6.5.2). A SW-PC MUST NOT exclude a
record from an attribute sent in fulfillment of an inventory
subscription simply because that record was not involved in the
triggering event (although a record might be excluded for other
reasons, such as if the subscription is targeted - see
Section 3.6.5.3).
3.6.5.2. Subscriptions Reporting Events
The way in which a SW-PV indicates it wishes to establish a
subscription requesting event records is by providing a non-zero EID
in the SW Request establishing the subscription (see Section 3.5.1).
However, when the SW-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 SW-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 SW-PC MUST only report events with EIDs
after the last reported event. In the case that the EID Epoch of the
SW-PC changes, the SW-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 SW-PV MAY
make other requests for event records that overlap with events that
are reported in fulfillment of a subscription. Such requests are
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unaffected by the presence of the subscription, nor is the
subscription affected by such requests. In other words, a given
request will get the same results back whether or not there was a
subscription. Likewise, an attribute sent in fulfillment of a
subscription will contain the same information whether or not other
requests had been received from the SW-PV.
A SW-PV needs to pay attention to the EID Epoch in these messages, as
changes in the Epoch might create discontinuities in the SW-PV's
understanding of the endpoint's Software Inventory Evidence
Collection state, as discussed in Section 3.5.5. In particular, once
the EID Epoch changes, a SW-PV is unable have confidence that it has
a correct understanding of the state of an endpoint's Software
Inventory Evidence Collection until after the SW-PV collects a
complete inventory.
SW-PCs MAY send partial lists of event records in fulfillment of a
subscription. (See Section 3.5.4 for more on partial list of event
records.) In the case that a SW-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 SW-PC sends a
partial list it does not wait for another change event to send
another SW Response, but continues sending SW Responses until it has
sent all event records that would have been included in a complete
fulfillment of the subscription.
3.6.5.3. Targeted Subscriptions
Subscriptions MAY be targeted to only apply to records that match a
given set of Software Identifiers. In the case where changes are
detected that affect multiple records, some matching the establishing
request's Software Identifiers and some not, the attribute sent in
fulfillment of the subscription MUST only include inventory or events
(as appropriate) for records that match the establishing request's
Software Identifiers. The SW-PC MUST NOT include non-matching
records in the attribute, even if those non-matching records
experienced change events that were co-temporal with change events on
the matching records.
In addition, a SW-PC MUST send an attribute in fulfillment of a
targeted subscription only when changes to the endpoint's Software
Inventory Evidence Collection impact one or more records matching the
subscription's establishing request's Software Identifiers. A SW-PC
MUST NOT send any attribute in fulfillment of a targeted subscription
based on detected change to the endpoint's Software Inventory
Evidence Collection that did not involve any of the records targeted
by that subscription.
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3.6.5.4. No Subscription Consolidation
A SW-PV MAY establish multiple subscriptions to a given SW-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 SW-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, SW-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 SW-PV.
3.6.5.5. Delayed Subscription Fulfillment
A SW-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 SW-PV in a single SW Response attribute. This can help
reduce network bandwidth consumption between the SW-PC and the SW-PV.
For example, consider a situation where 10 changes occur a tenth of a
second apart. If the SW-PC does not delay in assembling and sending
SW Response attributes, the SW-PV will receive 10 separate SW
Response attributes over a period of 1 second. However, if the SW-PC
waits half a second after the initial event before assembling a SW
Response, the SW-PV only receives two SW 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 3.6.5.4 prohibiting consolidation across multiple
subscriptions. When delaying fulfillment of subscriptions, SW-PCs
are still required to fulfill each individual subscription
separately. Moreover, in the case that change events within the
delay window cancel each other out (e.g., a record is deleted and
then re-added), the SW-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 SW-PC, but it does not reduce the total number
of change events reported.
SW-PCs are not required to support delayed fulfillment of
subscriptions. However, in the case that the SW-PC does support
delayed subscription fulfillment, it MUST be possible to configure
the SW-PC to disable delayed fulfillment. In other words, parties
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deploying SW-PCs need to be allowed to disable delayed subscription
fulfillment in their SW-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.
3.7. Multiple Sources of Software Inventory Evidence Records
The records in an endpoint's software inventory evidence collection
might potentially come from multiple sources. For example, records
might be derived from ISO SWID tags deposited on the file system and
collected therefrom. Records might also be generated by tools such
as software and package managers (e.g., RPM or YUM) or might be
translated from software discovery reports.
A SW-PC is not required to identify every possible source of software
information on its endpoint. Some SW-PCs might be explicitly tied
only to one or a handful of software inventory sources. For all
software inventory evidence sources that a particular SW-PC supports,
it MUST completely support all requirements of this specification
with regard to those sources. In other words, for supported sources,
the SW-PC is required to be capable of providing a complete set of
the provided software inventory evidence records; monitoring for
changes in the records reported by those sources, correctly providing
responses for both full and targeted requests that include records
from those sources, and providing either complete records or Software
Identifiers as appropriate. If the source's output is not in one of
the data models identified in the Software Data Model IANA table (see
Section 9.4), the SW-PC MUST be capable of converting that output
into one of the supported data models. In all cases, the SW-PC MUST
also be capable of deriving a Software Identifier from the resulting
record and also assigning that record a unique Record Identifier.
The SW-PC MUST NOT provide any inventory or event information from
software inventory sources for which it cannot provide this full
support.
When providing a SW Response (either in direct response to a SW
Request or in fulfillment of a subscription) the SW-PC MUST include
the complete set of relevant data from all supported sources of
software inventory evidence. In other words, a full inventory is
required to contain all records from all supported sources, a
targeted inventory is required to contain all relevant records from
all sources, and event tracking is required to cover all events from
all sources. With regard to events, a SW-PC's assignment of EIDs
MUST reflect the presence and order of all events on the endpoint (at
least for supported sources) regardless of the source. This means
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that if source A experiences an event, and then source B experiences
two events, and then source A experiences another two events, the SW-
PC is required to capture five events with consecutive EID values
reflecting the order in which the events occur.
Note that, if a SW-PC collects data from multiple sources, it is
possible that some software products might be "double counted". This
can happen if both sources of inventory evidence provide a record for
a single installation of a software product. Moreover, each of these
provided records might have different Software Identifiers. When a
SW-PC reports information or records events from multiple inventory
evidence 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 records corresponding to a single
installation of a software product, all such records from each source
are required to be part of the SW-PC's processing even if this might
lead to multiple reporting, and the SW-PC is not to ignore some
records to avoid such multiple reporting. Similarly, in the case
that multiple sources report an event, the SW-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 software inventory
information collected via SW-PCs and SW-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.
3.8. Error Handling
In the case where the SW-PC detects an error in a SW 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 SW Attributes.) In the
case that an error is detected in a SW Request the SW-PC MUST NOT
take any action requested by this SW Request, even if partial
completion of the SW is possible. In other words, a SW Request that
contains an error is completely ignored by the SW-PC (beyond sending
a PA-TNC Error attribute, and possibly logging the error locally)
rather than being partially executed.
In the case where the SW-PC receives a valid SW Request attribute but
experiences an error during the process of responding to that
attribute's instructions where that error prevents the SW-PC from
properly or completely fulfilling that request, the SW-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 SW-PC MUST NOT take any of the actions requested by the SW
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Request attribute which led to the detected error. This is the case
even if some actions could have been completed successfully, and
might even require the SW-PC to reverse some successful actions
already taken before the error condition was detected. In other
words, either all aspects of a SW Request complete fully and
successfully (in which case the SW-PC sends a SW Response attribute),
or no aspects of the SW Request occur (in which case the SW-PC sends
a PA-TNC Error attribute). In the case that a SW-PC sends a PA-TNC
Error attribute in response to a SW Request then the SW-PC MUST NOT
also send any SW Response attribute in response to the same SW
Request. For this reason, the sending of a SW Response attribute
MUST be the last action taken by a SW-PC in response to a SW Request
to avoid the possibility of a processing error occurring after that
SW Response attribute is sent.
In the case that the SW-PC detects an error that prevents it from
properly or completely fulfilling its obligations under an active
subscription, the SW-PC MUST send a PA-TNC Error attribute of type
SW_SUBSCRIPTION_FULFILLMENT_ERROR to the SW-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 SW-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 SW_ERROR error code SHOULD be
used in the sub-type. In the case that a
SW_SUBSCRIPTION_FULFILLMENT_ERROR is sent, the associated
subscription MUST be treated as cancelled by both the SW-PC and SW-
PV.
The SW-PV MUST NOT send any PA-TNC Error attributes to SW-PCs. In
the case that a SW-PV detects an error condition, it SHOULD log this
error but does not inform any SW-PC's of this event. Errors might
include, but are not limited to, detection of malformed SW Response
attributes sent from a given SW-PC, as well as detection of error
conditions when the SW-PV processes SW Responses.
Both SW-PCs and SW-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
information to aid in understanding the nature and cause of the
error.
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4. Software Message and Attributes for PA-TNC Protocol
This section describes the format and semantics of the Software
Message and Attributes for PA-TNC protocol. Software 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. 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 | SW | Software 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 SW-PC and SW-PV, so will be carried in a PB-TNC
message indicating a PA Subtype of SW Attributes. Note that although
the PA-TNC Error attribute is defined in the PA-TNC specification,
when it is used in a SW Attribute exchange, it uses the SW Attributes
Component Definition Value, as described in Section 4.2.8 of the PA-
TNC specification [RFC5792]. PB-TNC messages MUST always include the
SW Attributes Subtype defined in this section when carrying SW
Attributes over PA-TNC.
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, SW Attributes are never sent in the same PA-TNC
message as attributes defined in other PA-TNC binding specifications.
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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 Software 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 Software Message and Attributes for PA-TNC
specification defines a collection of PA-TNC attributes relevant to
the collection and transmission of software inventories and
associated events.
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.
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
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+-----------+-------------------------------------------------------+
| Field | Description |
+-----------+-------------------------------------------------------+
| Flags | This field defines flags affecting the processing of |
| | the Software 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 Software 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 SW 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 SW Attribute. |
| Value | |
+-----------+-------------------------------------------------------+
Table 3: Fields of the PA-TNC Attribute Format
4.4. SW 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.
o SW Request - This attribute is used to request a software
inventory or software event list from an endpoint. This attribute
might also establish a subscription on the recipient SW-PC. A SW-
PC MUST NOT send this attribute.
o Software Identifier Inventory - This attribute is used to convey
an inventory expressed using Software Identifiers (instead of full
records). When a SW-PC receives a SW Request attribute requesting
an inventory using Software Identifiers, the SW-PC MUST send a
Software Identifier Inventory attribute (or a PA-TNC Error) in
response. This attribute also MAY be sent by the SW-PC in
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fulfillment of an active subscription. A SW-PV MUST NOT send this
attribute.
o Software Identifier Events - This attribute is used to convey a
list of events concerning changes to an endpoint's Software
Inventory Evidence Collection. Affected software inventory
evidence records are indicated using Software Identifiers (instead
of full records). When a SW-PC receives a SW Request attribute
requesting an event collection using Software Identifiers, the SW-
PC MUST send a Software Identifier Events attribute (or a PA-TNC
Error) in response. This attribute also MAY be sent by the SW-PC
in fulfillment of an active subscription. A SW-PV MUST NOT send
this attribute.
o Software Inventory - This attribute is used to convey an inventory
expressed using full software inventory evidence records (instead
of Software Identifiers). When a SW-PC receives a SW Request
attribute requesting an inventory using full software inventory
evidence records, the SW-PC MUST send a Software Inventory
attribute (or a PA-TNC Error) in response. This attribute also
MAY be sent by the SW-PC in fulfillment of an active subscription.
A SW-PV MUST NOT send this attribute.
o Software Events - This attribute is used to convey a list of
events concerning changes to an endpoint's inventory evidence
collection. Affected software inventory evidence records are
indicated using full records (instead of Software Identifiers).
When a SW-PC receives a SW Request attribute requesting an event
collection using full records, the SW-PC MUST send a Software
Events attribute (or a PA-TNC Error) in response. This attribute
also MAY be sent by the SW-PC in fulfillment of an active
subscription. A SW-PV MUST NOT send this attribute.
o Subscription Status Request - This attribute is used to request a
SW-PC send a summary of all the active subscriptions it has where
the requesting party is the subscriber. The SW-PC MUST respond
with a Subscription Status Response (or a PA-TNC Error). A SW-PC
MUST NOT send this attribute.
o Subscription Status Response - This attribute is used to convey
information about the active subscriptions that a SW-PC has for a
given subscriber. A SW-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 SW Attribute exchange. It MUST be sent
by a SW-PC in response to a SW Request in the case where the SW-PC
encounters a fatal error (i.e., an error that prevents further
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processing of an exchange) relating to the attribute exchange. A
SW-PV MUST NOT send this attribute. The SW-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
SW-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 Software Identifier Inventory, Software Identifier
Events, Software Inventory, or Software Events attributes is expected
to be sent to a SW-PV in direct response to a SW Request attribute or
in fulfillment of an active subscription, those four attribute types
are referred to collectively in this document as "SW Response"
attributes.
All SW-PVs MUST be capable of sending SW Requests and be capable of
receiving and processing all SW Response attributes as well as PA-TNC
Error attributes. All SW-PCs MUST be capable of receiving and
processing SW Requests and be capable of sending all types of SW
Response attributes as well as PA-TNC Error attributes. In other
words, both SW-PVs and SW-PCs are required to support their role in
exchanges using any of the attribute types defined in this section.
SW-PVs MUST ignore any SW Request attributes that they receive. SW-
PCs MUST ignore any SW Response attributes or PA-TNC Error attributes
that they receive.
4.5. SW Attribute Exchanges
A SW Attribute Exchange is used to provide the SW-PV with a software
inventory or event collection from the queried endpoint.
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+-------------+ +--------------+
| SW-PC | | SW-PV | Time
+-------------+ +--------------+ |
| | |
|<------------SW Request--------------| |
| | |
| SW Response* | |
|-----------------or----------------->| |
| PA-TNC Error | |
| | V
*SW Response is one of the following: Software Identifier
Inventory, Software Identifier Events, Software Inventory,
or Software Events.
Figure 5: SW Attribute Exchange (Direct Response to SW Request)
In this exchange, the SW-PV indicates to the SW-PC, via a SW 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 records or Software Identifiers). The SW-PC
responds with the requested information using the appropriate
attribute type. A single SW Request MUST only lead to a single SW
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
SW-PC sends a SW Response to the SW-PV following a change event on
the endpoint in fulfillment of that subscription. Such an exchange
is shown in Figure 6.
+-------------+ +--------------+
| SW-PC | | SW-PV | Time
+-------------+ +--------------+ |
| | |
<Change Event>| | |
|--------SW Response(s)*------->| |
| | |
*SW Response is one of the following: Software Identifier
Inventory, Software Identifier Events, Software Inventory,
or Software Events.
Figure 6: SW Attribute Exchange (In Fulfillment of an Active
Subscription)
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Note that, unlike direct responses to a SW Request, a single change
event can precipitate multiple SW Responses for a single
subscription, but only if all but the last of those SW Responses
convey partial lists of event records, and the last of those SW
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 SW Response or PA-TNC
Error attributes in any combination except as noted earlier in this
paragraph.
All SW-PVs and SW-PCs MUST support both types of exchanges. In
particular, SW-PCs MUST be capable of pushing a SW Response to a SW-
PV immediately upon detection of a change to the endpoint's Software
Inventory Evidence Collection in fulfillment of established SW-PV
subscriptions, as described in Section 3.6.
4.6. Software 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 Software Message and
Attributes for PA-TNC protocol.
+--------------+----------+------------+----------------------------+
| Attribute | PEN | Integer | Description |
| Name | | | |
+--------------+----------+------------+----------------------------+
| SW Request | 0x000000 | 0x00000011 | Request from a SW-PV to a |
| | | | SW-PC for the SW-PC to |
| | | | provide a software |
| | | | inventory or event list |
| | | | |
| Software | 0x000000 | 0x00000012 | A collection of Software |
| Identifier | | | Identifiers sent from a |
| Inventory | | | SW-PC. |
| | | | |
| Software | 0x000000 | 0x00000013 | A collection of events |
| Identifier | | | impacting the endpoint's |
| Events | | | Software Inventory |
| | | | Evidence Collection, where |
| | | | impacted software |
| | | | inventory evidence records |
| | | | are indicated using |
| | | | Software Identifiers. |
| | | | |
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| Software | 0x000000 | 0x00000014 | A collection of software |
| Inventory | | | inventory evidence records |
| | | | sent from a SW-PC. |
| | | | |
| Software | 0x000000 | 0x00000015 | A collection of events |
| Events | | | impacting the endpoint's |
| | | | Software Inventory |
| | | | Evidence Collection, where |
| | | | impacted software |
| | | | inventory evidence records |
| | | | are indicated using full |
| | | | records. |
| | | | |
| Subscription | 0x000000 | 0x00000016 | A request for a list of a |
| Status | | | SW-PV's active |
| Request | | | subscription. |
| | | | |
| Subscription | 0x000000 | 0x00000017 | A list of a SW-PV's active |
| Status | | | subscriptions. |
| Response | | | |
| | | | |
| Reserved | 0x000000 | 0x00000018 | These attribute types are |
| | | - | reserved for future use in |
| | | 0x0000001F | revisions to Software |
| | | | Message and Attributes for |
| | | | PA-TNC. |
| | | | |
| PA-TNC Error | 0x000000 | 0x00000008 | An error attribute as |
| | | | defined in the PA-TNC |
| | | | specification [RFC5792]. |
+--------------+----------+------------+----------------------------+
Table 4: SW Attribute Enumeration
4.7. Normalization of Text Encoding
In order to ensure consistency of transmitted attributes, a field
requiring normalization, as indicated in its description, 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. SW-PCs and SW-PVs
MUST NOT perform conversion and normalization on any field values
except those specifically identified as requiring normalization in
the following sections. Note, however, that some data models require
additional normalization before source information is added to an
Endpoint's Inventory Evidence Collection as a record. The references
from the Software Data Model IANA table (see section Section 9.4 will
note where this is necessary.
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4.8. Request IDs
All SW 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 SW-PV and the receiving SW-PC.
Specifically, the SW-PV assigns each SW 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 SW-PV's Posture Broker
Server. 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 SW-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 SW-PC
SHOULD structure the reuse to maximize the time between original and
subsequent use. The Request ID value is included in a SW Response
attribute directly responding to this SW Request to indicate which SW
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. SW-PCs are not required to check
for duplicate Request IDs.
In the case that a SW Request requests the establishment of a
subscription and the receiving SW-PC agrees to that subscription, the
Request ID of that SW 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 SW-PV MUST NOT reuse a Request ID
value in communicating to a given SW-PC while that Request ID is also
serving as a Subscription ID for an active subscription with that SW-
PC. In the case where a SW-PC receives a SW Request from a given SW-
PV where that Request ID is also the Subscription ID of an active
subscription with that SW-PV, the SW-PC MUST respond with a PA-TNC
Error attribute with an error code of SW_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.
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4.9. SW Request
A SW-PV sends this attribute to a SW-PC to request that the SW-PC
send software inventory information to the SW-PV. A SW-PC MUST NOT
send this attribute.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Software Identifier Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Earliest EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Identifier Length | Software ID (var length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: SW Request Attribute
+---------------+---------------------------------------------------+
| Field | Description |
+---------------+---------------------------------------------------+
| Flags: Bit 0 | If set (1), the SW-PC MUST delete all |
| - Clear | subscriptions established by the requesting SW-PV |
| Subscriptions | (barring any errors). |
| | |
| Flags: Bit 1 | If set (1), in addition to responding to the |
| - Subscribe | request as described, the SW-PC MUST establish a |
| | subscription with parameters matching those in |
| | the request attribute (barring any errors). |
| | |
| Flags: Bit 2 | If unset (0), the SW-PC's response MUST consist |
| - Result Type | of complete software inventory evidence records |
| | and thus the response MUST be a Software |
| | Inventory, a Software Events, or a PA-TNC Error |
| | attribute. If set (1), the response MUST consist |
| | of Software Identifiers and thus the response |
| | MUST be a Software Identifier Inventory, a |
| | Software 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. |
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| | |
| Software | A 3-byte unsigned integer indicating the number |
| Identifier | of Software Identifiers that follow. If this |
| Count | value is non-zero, this is a targeted request, as |
| | described in Section 3.3. The Software |
| | Identifier Length and Software ID fields are |
| | repeated, in order, the number of times indicated |
| | in this field. In the case where Software |
| | Identifiers are present, the SW-PC MUST only |
| | respond with software inventory evidence records |
| | or Software Identifiers that correspond to the |
| | identifiers the SW-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 Software Identifier Length and |
| | Software ID fields. In this case, the SW-PV is |
| | indicating an interest in all software inventory |
| | evidence records on the endpoint (i.e., this is |
| | not a targeted request). |
| | |
| Request ID | A value that uniquely identifies this SW Request |
| | from a particular SW-PV. |
| | |
| Earliest EID | In the case where the SW-PV is requesting |
| | software events, this field contains the EID |
| | value of the earliest event the SW-PV wishes to |
| | have reported. (Note - the report will be |
| | inclusive of the event with this EID value.) In |
| | the case where the SW-PV is requesting an |
| | inventory, then this field MUST be 0. |
| | (0x00000000) In the case where this field is non- |
| | zero, the SW-PV is requesting events and the SW- |
| | PC MUST respond using a Software Events, Software |
| | Identifier Events, or a PA-TNC Error attribute. |
| | In the case where this field is zero, the SW-PV |
| | is requesting an inventory and the SW-PC MUST |
| | respond using a Software Inventory, a Software |
| | Identifier Inventory, or a PA-TNC Error |
| | attribute. |
| | |
| Software | A 2-byte unsigned integer indicating the length |
| Identifier | in bytes of the Software ID field. |
| Length | |
| | |
| Software ID | A string containing the Software Identifier value |
| | from a software inventory evidence record. This |
| | field value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
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| | MUST NOT be NULL terminated. |
+---------------+---------------------------------------------------+
Table 5: SW Request Attribute Fields
The SW-PV sends the SW Request attribute to a SW-PC to request the
indicated information. Note that between the Result Type flag and
the Earliest EID field, the SW-PC is constrained to a single possible
SW 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 SW-PV on the receiving SW-PC.
Specifically, an attribute with the Subscribe flag set seeks to
establish a new subscription by the requesting SW-PV to the given SW-
PC, while an attribute with the Clear Subscription flag seeks to
delete all existing subscriptions by the requesting SW-PV on the
given SW-PC. Note that, in the latter case, only the subscriptions
associated with the Connection ID and the Posture Validator ID of the
requester are deleted as described in Section 3.6.3. 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 Software Identifiers
(if present) indicate if and how a subscription is targeted. In the
case that the SW-PC is unable or unwilling to comply with the SW-PV's
request to establish or clear subscriptions, the SW-PC MUST respond
with a PA-TNC Error attribute with the SW_SUBSCRIPTION_DENIED_ERROR
error code. (Note that if the SW-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 SW-PC in addition to setting up the subscription.
Assuming the SW-PC is willing to comply with the subscription it MUST
send an appropriate response attribute to a request with the
Subscribe flag set containing all requested information. The same is
true of the Clear Subscription flag - assuming there is no error the
SW-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 SW Request attribute. In the case where this request is
successful, the end result MUST be equivalent to the SW-PC clearing
its subscription list for the given SW-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
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all the subscriptions including the one that was just created.) In
the case that the requested actions are successfully completed, the
SW-PC MUST respond with a SW Response attribute. (The specific type
of SW 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 SW-PC MUST
NOT add a new subscription, MUST NOT clear the old subscriptions, and
the SW-PC MUST respond with a PA-TNC Error attribute. In other
words, the SW-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 SW-PV is
requesting an inventory or event list from the SW-PC. A value of 0
(0x00000000) represents a request for inventory information.
Otherwise, the SW-PV is requesting event information. For Earliest
EID values other than 0, the SW-PC's response MUST respond with event
records, as described in Section 3.5. Note that the request does not
identify a particular EID Epoch, since responses can only include
events in the SW-PC's current EID Epoch.
The Software Identifier Count indicates the number of Software
Identifiers in the attribute. This number might be any value between
0 and 16,777,216, inclusive. A single Software Identifier is
represented by fields: Software Identifier Length and Software ID.
The Software Identifier Length field indicates the number of bytes
allocated to Software ID field. The Software Identifier field
contains a Software Identifier as describe in Section 3.2. The
presence of one or more Software Identifiers is used by the SW-PV to
indicate a targeted request, which seeks only inventories of or
events affecting software corresponding to the given identifiers.
The SW-PC MUST only respond with records that match the Software
Identifiers provided in the SW-PVs SW Request attribute.
4.10. Software Identifier Inventory
A SW-PC sends this attribute to a SW-PV to convey the inventory of
the endpoint's Software Inventory Evidence Collection expressed using
Software Identifiers. This list might represent a complete inventory
or a targeted list of records, depending on the parameters in the SW-
PV's request. A SW-PV MUST NOT send this attribute. The SW-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 SW 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 | Software Identifier Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Data Model Type| Software IdentifierLength |SW ID (var len)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record ID Length | Record ID (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Software 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 SW 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 | |
| | |
| Software | The number of Software Identifiers that follow. |
| Identifier | This field is an unsigned integer. The Data Model |
| Count | Type, Software Identifier Length, SW ID, Record ID |
| | Length, and Record 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 SW Request attribute from a SW-PV, |
| Subscription | this field MUST contain an exact copy of the |
| ID | Request ID field from that SW 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 |
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| | 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 SW-PC, |
| | or 0 if the SW-PC has no recorded events. This |
| | field is an unsigned 4-byte integer. |
| | |
| Data Model | A 1-byte unsigned integer containing an identifier |
| Type | number from the Software Data Model IANA table |
| | that identifies the data model of the reported |
| | record. |
| | |
| Software | A 2-byte unsigned integer indicating the length in |
| Identifier | bytes of the SW ID field. |
| Length | |
| | |
| SW ID | A string containing the Software Identifier value |
| | from a software inventory evidence record. This |
| | field value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
| | |
| Record ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Record ID field. |
| | |
| Record ID | A string containing the Record Identifier value |
| | from a software inventory evidence record. 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: Software Identifier Inventory Attribute Fields
In the case that this attribute is sent in fulfillment of a
subscription, the Subscription Fulfillment bit MUST be set (1). In
the case that this attribute is sent in direct response to a SW
Request, the Subscription Fulfillment bit MUST be unset (0). Note
that the SW Response attribute sent in direct response to a SW
Request that establishes a subscription (i.e., a subscription's
establishing request) MUST be treated as a direct response to that SW
Request (and thus the Subscription Fulfillment bit is unset). SW
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.
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The Software Identifier Count field indicates the number of Software
Identifiers present in this inventory. Each Software Identifier is
represented by a set of five fields: Data Model Type, Software
Identifier Length, SW ID, Record ID Length, and Record ID. These
fields will appear once for each reported record.
When responding directly to a SW Request attribute, the Request ID
Copy / Subscription ID field MUST contain an exact copy of the
Request ID field from that SW 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 3.5 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. Software Identifier Events
A SW-PC sends this attribute to a SW-PV to convey events where the
affected records are expressed using Software Identifiers. A SW-PV
MUST NOT send this attribute. The SW-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 SW Request attribute where the Result Type is
1 and the Earliest EID is non-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 | Event Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Consulted EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action |Data Model Type| Software Identifier Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|SW ID (var len)| Record ID Length |Record ID (var)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Software 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 SW 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, Data Model |
| | Type, Software Identifier Length, SW ID, Record ID |
| | Length, and Record ID fields are repeated, in |
| | order, the number of times indicated in this |
| | field. (An instance of these 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 SW Request attribute from a SW-PV, |
| Subscription | this field MUST contain an exact copy of the |
| ID | Request ID field from that SW 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 SW-PC, |
| | or 0 if the SW-PC has no recorded events. This |
| | field contains the EID of the SW-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 3.5.4 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 SW-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 |
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| | 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 SW-PVs MUST support them. The Timestamp |
| | string MUST NOT be NULL 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 record to the endpoint's Software |
| | Inventory Evidence Collection; 2 = DELETION - the |
| | removal of a record from the endpoint's Software |
| | Inventory Evidence Collection; 3 = ALTERATION - |
| | There was an alteration to a record within the |
| | endpoint's Software Inventory Evidence Collection. |
| | All other values are reserved for future use and |
| | MUST NOT be used when sending attributes. In the |
| | case where a SW-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. |
| | |
| Data Model | A 1-byte unsigned integer containing an identifier |
| Type | number from the Software Data Model IANA table |
| | that identifies the data model of the reported |
| | record. |
| | |
| Software | A 2-byte unsigned integer indicating the length in |
| Identifier | bytes of the SW ID field. |
| Length | |
| | |
| SW ID | A string containing the Software Identifier value |
| | from a software inventory evidence record. This |
| | field value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
| | |
| Record ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Record ID field. |
| | |
| Record ID | A string containing the Record Identifier value |
| | from a software inventory evidence record. This |
| | field value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
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Table 7: Software Identifier Events Attribute Fields
The first few fields in the Software Identifier Events attribute
mirror those in the Software Identifier Inventory attribute. The
primary difference is that, instead of conveying an inventory using
Software Identifiers, the attribute conveys zero or more event
records, consisting of the EID, timestamp, action type, data model
type, Software Identifier, and Record Identifier of the affected
software inventory evidence record.
With regard to the Timestamp field, it is important to note that
clock skew between the SW-PC and SW-PV as well as between different
SW-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, Software
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 record was removed and then subsequently re-added, one can get
an indication as to how long the system was without the given record
(and, thus without the associated software). Since this will involve
comparison of timestamp values all originating on the same system,
clock skew between the SW-PC and SW-PV is not an issue. However, if
the SW-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 Software 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 SW-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 3.5.4) 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.
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If multiple events are sent in a Software Identifier Events
attribute, the order in which they appear within the attribute is not
significant. The EIDs associated with them are used for ordering the
indicated events appropriately. Also note that a single Software
Identifier might appear multiple times in an attribute, such as if
multiple events involving the associated record were being reported.
4.12. Software Inventory
A SW-PC sends this attribute to a SW-PV to convey a list of inventory
records. A SW-PV MUST NOT send this attribute. The SW-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 SW Request attribute where the
Result Type is 0 and the Earliest EID is zero.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID Copy / Subscription ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Data Model Type| Record ID Length |Record ID (var)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Software 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 SW Request, this bit MUST be unset |
| | (0). |
| | |
| Flags: Bit | Reserved for future use. This field MUST be set to |
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| 1-7 - | zero on transmission and ignored upon reception. |
| Reserved | |
| | |
| Record Count | The number of records that follow. This field is a |
| | 3-byte unsigned integer. The Data Model Type, |
| | Record Identifier Length, Record ID, Record |
| | Length, and Record 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 SW Request attribute from a SW-PV, |
| Subscription | this field MUST contain an exact copy of the |
| ID | Request ID field from that SW 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 SW-PC, |
| | or 0 if the SW-PC has no recorded events. This |
| | field is an unsigned 4-byte integer. |
| | |
| Data Model | A 1-byte unsigned integer containing an identifier |
| Type | number from the Software Data Model IANA table |
| | that identifies the data model of the reported |
| | record. |
| | |
| Record ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Record ID field. |
| | |
| Record ID | A string containing the Record Identifier value |
| | from a software inventory evidence record. This |
| | field value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
| | |
| Record Len | This is a 4-byte unsigned integer indicating the |
| | length of the following software inventory |
| | evidence record in bytes. |
| | |
| Record | A software inventory evidence record as a string. |
| | The record MUST be converted and normalized to |
| | Network Unicode format, as described in Section |
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| | 4.7. This string MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 8: Software Inventory Attribute Fields
The Software Inventory attribute contains some number of software
inventory evidence records. Given that the size of records can vary
considerably, the length of this attribute is highly variable and, if
transmitting a complete inventory, can be extremely large.
Enterprises might wish to constrain the use of Software Inventory
attributes to targeted requests to avoid over-burdening the network
unnecessarily.
When copying a software inventory evidence record into the Record
field, the record MUST be converted and normalized to use Network
Unicode format prior to its inclusion in the record field.
4.13. Software Events
A SW-PC sends this attribute to a SW-PV to convey a list of events
where the affected software inventory evidence records are expressed
using full records. A SW-PV MUST NOT send this attribute. The SW-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 SW
Request attribute where the Result Type is 0 and the Earliest EID is
non-zero.
Note that each record is reported along with its Record Identifier.
This can be used to link reported records to reported Software
Identifier + Record Identifier pairs.
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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 |Data Model Type| Record ID Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Identifier (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Software 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 SW 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. |
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| Reserved | |
| | |
| Event Count | The number of events being reported in this |
| | attribute. This field is a 3-byte unsigned |
| | integer. The EID, Timestamp, Action, Data Model |
| | Type, Record Identifier Length, Record Identifier, |
| | Record Length, and Record fields are repeated, in |
| | order, the number of times indicated in this |
| | field. (An instance of these 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 SW Request attribute from a SW-PV, |
| Subscription | this field MUST contain an exact copy of the |
| ID | Request ID field from that SW 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 SW-PC, |
| | or 0 if the SW-PC has no recorded events. This |
| | field contains the EID of the SW-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 3.5.4 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 timestamp is the SW-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 |
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| | 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 SW-PVs MUST support them. The Timestamp |
| | string MUST NOT be NULL 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 record to the endpoint's Software |
| | Inventory Evidence Collection; 2 = DELETION - the |
| | removal of a record from the endpoint's Software |
| | Inventory Evidence Collection; 3 = ALTERATION - |
| | There was an alteration to a record within the |
| | endpoint's Software Inventory Evidence Collection. |
| | All other values are reserved for future use and |
| | MUST NOT be used when sending attributes. In the |
| | case where a SW-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. |
| | |
| Data Model | A 1-byte unsigned integer containing an identifier |
| Type | number from the Software Data Model IANA table |
| | that identifies the data model of the reported |
| | record. |
| | |
| Record ID | A 2-byte unsigned integer indicating the length in |
| Length | bytes of the Record ID field. |
| | |
| Record ID | A string containing the Record Identifier value |
| | from a software inventory evidence record. This |
| | field value MUST be normalized to Network Unicode |
| | format, as described in Section 4.7. This string |
| | MUST NOT be NULL terminated. |
| | |
| Record Len | This is a 4-byte unsigned integer indicating the |
| | length of the following record in bytes. |
| | |
| Record | A software inventory evidence record as a string. |
| | The record MUST be converted and normalized to |
| | Network Unicode format, as described in Section |
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| | 4.7. This string MUST NOT be NULL terminated. |
+--------------+----------------------------------------------------+
Table 9: Software Events Attribute Fields
The fields of this attribute are used in the same way as the
corresponding fields of the previous attributes. As with the
Software Inventory attribute, a Software Events attribute can be
quite large if many events have occurred following the event
indicated by a request's Earliest EID. As such, it is recommended
that the SW Request attributes only request full records be sent
(Result Type set to 0) in a targeted request, thus constraining the
response just to records that match a given set of Software
Identifiers.
As with the Software Identifier Events Attribute, this attribute MUST
only contain event records with EIDs coming from the current EID
Epoch of the SW-PC.
As with the Software Inventory Attribute, the SW-PC MUST perform
conversion and normalization of the record.
4.14. Subscription Status Request
A SW-PV sends this attribute to a SW-PC to request a list of active
subscriptions for which the requesting SW-PV is the subscriber. A
SW-PC MUST NOT send this attribute.
This attribute has no fields.
A SW-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 SW-PC sends this attribute to a SW-PV to report the list of active
subscriptions for which the receiving SW-PV is the subscriber. A SW-
PV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status Flags | Subscription Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Software Identifier Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Earliest EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Identifier Length | Software ID (var length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Subscription Status Response Attribute
+-----------------+-------------------------------------------------+
| Field | Description |
+-----------------+-------------------------------------------------+
| Flags: Bit 0-7 | Reserved for future use. This field MUST be set |
| - Reserved | to zero on transmission and ignored upon |
| | reception. |
| | |
| Subscription | The number of subscription records that follow. |
| Record Count | This field is a 3-byte unsigned integer. The |
| | Flags, Software Identifier Count, Request ID, |
| | Earliest EID, Software Identifier Length, and |
| | 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, Software | For each active subscription, these fields |
| Identifier | contain an exact copy of the fields with the |
| Count, Request | same name as provided in the subscription's |
| ID, Earliest | establishing request. |
| EID, Software | |
| Identifier | |
| Length, and | |
| 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
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Subscription Status Request to which this attribute is a response.
As described in Section 3.6.2, the SW-PC MUST use the requester's
Connection ID and its Posture Validator ID to determine which
subscriptions are associated with the requester.
A SW-PC MUST send a Subscription Status Response attribute in
response to a Subscription Status Request attribute. The only
exception to this is if the SW-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.
Each subscription record included in a Subscription Status Response
attribute duplicates the fields of a SW Request attribute that was
the establishing request of a subscription. Note that the Request ID
field in the record captures the Subscription ID associated with the
given subscription record (since the Subscription ID is the same as
the Request ID of the establishing request). Note also that if the
establishing request is targeted, then its Record Count field will be
non-zero and, within that subscription record, the Record Namespace
Length, Record Namespace, Record ID Length, and Record ID fields are
repeated, in order, the number of times indicated in the Record Count
field. As such, each subscription record can be different sizes. If
the establishing request is not targeted (Record Count field is 0),
the subscription record has no Record Namespace Length, Record
Namespace, Record ID Length, or Record ID fields.
When a SW-PV compares the information received in a Subscription
Status Response to its own records of active subscriptions it should
be aware that the SW-PC might be unable to distinguish this SW-PV
from other SW-PVs on the same NEA Server. As a result, it is
possible that the SW-PC will report more subscription records than
the SW-PV recognizes. For this reason, SW-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 Software 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 Software
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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 SW Response attribute
due to factors that prevent the reliable creation of a SW Response.
As such, a SW-PC MUST NOT send both a PA-TNC Error attribute and a SW
Response attribute in response to a single SW Request attribute.
Table 11 lists the Error Code values for the PA-TNC Error attribute
specific to the Software 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.
Note that a message with a Software 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, a SW
Attribute might have an invalid parameter, leading to an error code
of "Invalid Parameter". In this case, the SW-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 | SW_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 SW Attributes. The |
| | Description field SHOULD contain |
| | additional diagnostic information. |
| | |
| 0x00000021 | SW_SUBSCRIPTION_DENIED_ERROR. This |
| | indicates that the SW-PC denied the SW- |
| | PV's request to establish a subscription. |
| | The Description field SHOULD contain |
| | additional diagnostic information. |
| | |
| 0x00000022 | SW_RESPONSE_TOO_LARGE_ERROR. This |
| | indicates that the SW-PC's response to |
| | the SW-PV's request was too large to be |
| | serviced. The error information structure |
| | indicates the largest possible size of a |
| | response supported by the SW-PC (see |
| | Section 4.16.2). The Description field |
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| | SHOULD contain additional diagnostic |
| | information. |
| | |
| 0x00000023 | SW_SUBSCRIPTION_FULFILLMENT_ERROR. This |
| | indicates that the SW-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 SW- |
| | PC experienced. The SW-PC and SW-PV MUST |
| | treat the identified subscription as |
| | cancelled. |
| | |
| 0x00000024 | SW_SUBSCRIPTION_ID_REUSE_ERROR. This |
| | indicates that the SW-PC received a SW |
| | Request from a given SW-PV where the |
| | Request ID of that SW Request is |
| | currently used as the Subscription ID of |
| | an active subscription with that SW-PV. |
| | This error does not cancel the identified |
| | subscription. |
| | |
| 0x00000025-0x0000002F | RESERVED. These Error Codes are reserved |
| | for use by future revisions of the |
| | Software 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 Software Message and Attributes for
PA-TNC
The following subsections describe the structures present in the
Error Information fields.
4.16.1. SW_ERROR, SW_SUBSCRIPTION_DENIED_ERROR and
SW_SUBSCRIPTION_ID_REUSE_ERROR Information
The SW_ERROR error code indicates that the sender (the SW-PC) has
encountered an error related to the processing of a SW Request
attribute but which is not covered by more specific SW error codes.
The SW_SUBSCRIPTION_DENIED_ERROR is used when the SW-PV requests to
establish a subscription or clear all subscriptions from the given
SW-PV, but the SW-PC is unable or unwilling to comply with this
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request. The SW_SUBSCRIPTION_ID_REUSE_ERROR is used when the SW-PC
receives a SW 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: SW Error, Subscription Error, and Subscription ID Reuse
Information
+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Copy of | In the case that this error condition is generated |
| Request ID / | in direct response to a SW Request attribute, this |
| Subscription | field MUST contain an exact copy of the Request ID |
| ID | field in the SW 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 SW_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 |
| | SW_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: SW Error, Subscription Error, and Subscription ID Reuse
Information Fields
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This error information structure is used with SW_ERROR,
SW_SUBSCRIPTION_DENIED_ERROR, and SW_SUBSCRIPTION_ID_REUSE_ERROR
status codes to identify the SW Request attribute that precipitated
the error condition and to describe the error. The Description field
contains text describing the error. The SW-PC MAY encode machine-
interpretable information in this field, but SHOULD also include a
human-readable description of the error, since the receiving SW-PV
might not recognize the SW-PC's encoded information.
4.16.2. SW_RESPONSE_TOO_LARGE_ERROR Information
The SW_RESPONSE_TOO_LARGE_ERROR error code indicates that a response
generated by a SW-PC in response to a SW-PV's SW Request attribute
was too large to send.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Copy of Request ID / Subscription I |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Allowed Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Description (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: SW Response Too Large Error Information
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+--------------+----------------------------------------------------+
| Field | Description |
+--------------+----------------------------------------------------+
| Copy of | In the case that the attribute in question is |
| Request ID / | generated in direct response to a SW Request, this |
| Subscription | field MUST contain an exact copy of the Request ID |
| ID | field in the SW 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 the latter |
| | case, the SW_RESPONSE_TOO_LARGE_ERROR appears as a |
| | sub-error for a SW_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 SW Attribute that the SW-PC is currently |
| | willing to send in response to a SW 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: SW Response Too Large Error Information Fields
This error structure is used with the SW_RESPONSE_TOO_LARGE_ERROR
status code to identify the SW Request attribute that precipitated
the error condition and to describe the error. The Maximum Allowed
Size field indicates the largest attribute the SW-PC is willing to
send in response to a SW Request under the current circumstances.
Note that under other circumstances, the SW-PC might be willing to
return larger or smaller responses than indicated (such as if the
endpoint connects to the NEA Server using a different network
protocol). The other fields in this error information structure have
the same meanings as corresponding fields in the SW_ERROR and
SW_SUBSCRIPTION_DENIED_ERROR information structure.
4.16.3. SW_SUBSCRIPTION_FULFILLMENT_ERROR Information
The SW_SUBSCRIPTION_FULFILLMENT_ERROR error code indicates that the
SW-PC encountered an error while fulfilling a subscription. The
bytes after the first 4 octets duplicate a PA-TNC Error attribute (as
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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: SW Subscription Fulfillment Error Information
+--------------+----------------------------------------------------+
| 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: SW Subscription Fulfillment Error Information Fields
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This error structure is used with the
SW_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 SW-PC encountered
while fulfilling the given subscription. The sub-error MUST NOT have
an error code of SW_SUBSCRIPTION_FULFILLMENT_ERROR.
The SW-PC sending a PA-TNC Error attribute with this error code, and
the SW-PV receiving it, MUST treat the subscription identified by the
Subscription ID field as cancelled. All other subscriptions are
unaffected.
5. Supported Data Models
Software Message and Attributes for PA-TNC supports an extensible
list of data models for representing and transmitting software
inventory information. This list of data models appears in the
Software Data Model IANA table (see Section 9.4). This document
provides guidance for an initial set of data models. Other documents
might provide guidance on the use of new data models by Software
Message and Attributes for PA-TNC, and will be referenced by
extensions to the Software Data Model IANA table.
5.1. ISO 2015 SWID Tags using XML
The International Organization for Standardization and the
International Electrotechnical Commission (ISO/IEC) published the
specification governing SWID tag construction and use in 2009 with a
revised version published in 2015. [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 Message and Attributes for PA-TNC has no reliance on the
presence or management of SWID tags on an endpoint as described in
the ISO specification. However, the data model for describing
software that is presented in the ISO specification provides a robust
and comprehensive way of describing software and is adopted here as a
means of representing and transmitting software information. It
should be emphasized, the use of the ISO SWID tag data model makes no
assumption as to whether the source of the recorded information was,
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in fact, an ISO SWID tag harvested from the endpoint or whether the
information was created using some other source and normalized to the
SWID format.
5.1.1. Guidance on Normalizing Source Data to ISO 2015 SWID Tags using
XML
TBD
Don't violate the specification
Use your own Tag Creator RegID or the Unknown Tag Creator RegID. Do
not use some other party's RegID, especially not the RegID of the
software author if you are not the author.
5.1.2. Guidance on Creation of Software Identifiers from ISO 2015 SWID
Tags
TBD
Use combination of Tag Creator RegID and Unique ID fields.
Specifically, format should be NUMBER::TAG_CREATOR_REGID UNIQUE_ID,
where NUMBER is the length of TAG_CREATOR_REGID in bytes. The rest
of the Software Identifier MUST be the concatination of the Tag
Creator RegID and the Unique ID from the tag, without any connecting
character or whitespace.
5.2. ISO 2009 SWID Tags using XML
As noted above, ISO's SWID tag specification provides a useful data
model for representation of software information. As of the writing
of this specification, while the 2015 specification is considered
more comprehensive and addresses some issues with the 2009
specification, 2009-format SWID tags remain far more common in
deployments. For this reason, ISO 2009 SWID tags are included in the
Software Data Model IANA table.
5.2.1. Guidance on Normalizing Source Data to ISO 2015 SWID Tags using
XML
TBD
Don't violate the specification
Use your own Tag Creator RegID or the Unknown Tag Creator RegID. Do
not use some other party's RegID, especially not the RegID of the
software author if you are not the author.
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5.2.2. Guidance on Creation of Software Identifiers from ISO 2015 SWID
Tags
TBD
Use combination of Tag Creator RegID and Unique ID fields.
Specifically, format should be NUMBER::TAG_CREATOR_REGID UNIQUE_ID,
where NUMBER is the length of TAG_CREATOR_REGID in bytes. The rest
of the Software Identifier MUST be the concatination of the Tag
Creator RegID and the Unique ID from the tag, without any connecting
character or whitespace.
6. Security Considerations
This section discusses some of the security threats facing Posture
Collectors and Posture Validators that implement the Software 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
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.
6.1. Evidentiary Value of Software Inventory Evidence Records
It must be remembered that the accuracy of an endpoints Software
Inventory Evidence Collection as an indicator of the endpoints
software load and changes thereon is only as accurate as the tools
that populate and manage the software inventory evidence records in
this collection. Some tools might not be designed to update records
in the Software Inventory Evidence Collection in real time resulting
in a collection that is out-of-step with actual system state.
Moreover, tools might inaccurately characterize software, or fail to
properly record its removal. Finally, it is likely that there will
be software on the endpoint that is not tracked by any source and
thus is not reflected in the Software Inventory Evidence Collection.
Users of collected software inventory evidence records need to
understand that the information provided by the Software Message and
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Attributes for PA-TNC capability cannot be treated as completely
accurate. Nonetheless, having endpoints report this information can
still provide useful insights into the state of the endpoint's
software load, and can alert administrators and policy tools of
situations that require remediation.
6.2. Sensitivity of Collected Records
Software records 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 Software Inventory Evidence Collection can be browsed and
individual records 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 records simply by inspecting other parts of the
endpoint.
The situation changes when an endpoint's inventory records are
collected and stored off of the endpoint itself, such as on a NEA
Server or CMDB. Inventory records 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
inventory records might provide many details that are useful for
mounting an attack. A list of the inventory records associated with
an endpoint reveals a list of software installed on the endpoint.
This list can be very detailed, noting specific versions and even
patch levels, which an adversary can use to identify vulnerable
software and design efficacious attacks.
In addition, other information might also be gleaned from a
collection of software inventory records:
o An inventory record might include information about where the
product was installed on a given endpoint. This can reveal
details about the file organization of that endpoint that an
attacker can utilize.
o An inventory record might include information about how the
software was provided to the endpoint, who in an organization
signs off on the package release, and who packaged the product for
installation. This information might be used as a starting point
for the development of supply chain attacks.
o Events affecting inventory records are reported with timestamps
indicating when each given event occurred. This can give the
attacker an indication of how quickly an organization distributes
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patches and updates, helping the attacker determine how long an
attack window might remain open.
Any consolidated software inventory is a potential risk, because such
an inventory can provide an adversary an insight into the
enterprise's configuration and management process. It is recommended
that a centralized software inventory record collection be protected
against unauthorized access. Mechanisms to accomplish this can
include encrypting the data at rest, ensuring that access to the data
is limited only to necessary individuals and processes, and other
basic security precautions.
6.3. Integrity of Endpoint Records
SW-PCs maintain records of detected changes to the endpoint's
Software Inventory Evidence Collection. These records are used to
respond to a SW-PV's request for change events. The SW-PV might use
a list of reported events to update its understanding of the
endpoint's Software Inventory Evidence Collection without needing to
receive a full inventory report from the SW-PC. For this reason,
preserving the integrity of the SW-PC's record of events is extremely
important. If an attacker modifies the SW-PC's record of changes to
the endpoint's Software Inventory Evidence Collection, this might
cause the SW-PV's understanding of the endpoint's Software Inventory
Evidence Collection to differ from its actual state. Results might
include leading the SW-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 Software Inventory Evidence Records. As such, the SW-PC
MUST take steps to protect the integrity of its event records.
In addition, records of established SW-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
SW-PV, the SW-PC might fail to correctly fulfill this subscription.
The SW-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 SW-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 SW-PC MUST protect the integrity of subscription
records.
6.4. SW-PC Access Permissions
A SW-PC requires sufficient permissions to collect Software Inventory
Evidence Records from all of its supported sources, as well as
sufficient permissions to interact with the endpoint's Posture Broker
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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 SW-PC (or software that incorporates a SW-PC as one
of its capabilities) additional permissions might be required by the
SW-PC software. The SW-PC SHOULD NOT be granted permissions beyond
what it needs in order to fulfill its duties.
6.5. Sanitization of Record Fields
Not all sources of software inventory evidence are necessarily
tightly controlled. For example, consider a source that gathers
.swid files from the endpoint's file system. Any party could create
a new .swid file that could be collected and turned into a Software
Inventory Evidence Record. As a result, it is important that the
contents of source information not be automatically trusted. In
particular, tools that read source information and the Software
Inventory Evidence Records derived therefrom, including SW-PCs, need
to be careful to sanitize input to prevent buffer overflow attacks,
encoding attacks, and other weaknesses that might be exploited by an
adversary who can control the contents of a record.
6.6. PA-TNC Security Threats
In addition to the aforementioned considerations the Software 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.
7. Privacy Considerations
As noted in Section 6.2, if an adversary can gain an understanding of
the software installed on an endpoint, they can utilize this to
launch attacks and maintain footholds on this endpoint. For this
reason, the NEA Server needs to ensure adequate safeguards are in
place to prevent exposure of collected inventory records. For
similar reasons, it is advisable that an endpoint only send records
to a NEA Server that is authorized to receive this information and
that can be trusted to safeguard this information after collection.
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8. 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, SW
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
Software 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. As such, this
specification provides important capabilities not present in the PA-
TNC specification.
9. 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
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.
9.1. 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
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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 | SW Request | Software Message and |
| | | | Attributes for PA-TNC |
| | | | |
| 0 | 18 | Software Identifier | Software Message and |
| | | Inventory | Attributes for PA-TNC |
| | | | |
| 0 | 19 | Software Identifier | Software Message and |
| | | Events | Attributes for PA-TNC |
| | | | |
| 0 | 20 | Software Inventory | Software Message and |
| | | | Attributes for PA-TNC |
| | | | |
| 0 | 21 | Software Events | Software Message and |
| | | | Attributes for PA-TNC |
| | | | |
| 0 | 22 | Subscription Status | Software Message and |
| | | Request | Attributes for PA-TNC |
| | | | |
| 0 | 23 | Subscription Status | Software Message and |
| | | Response | Attributes for PA-TNC |
| | | | |
| 0 | 24 | Subscription Status | Software Message and |
| | | Response | Attributes for PA-TNC |
| | | | |
| 0 | 25 - 31 | Reserved for future | Software Message and |
| | | use | Attributes for PA-TNC |
+-----+---------+---------------------+-----------------------------+
9.2. 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 codes 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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+-----+---------+-----------------------------------+---------------+
| PEN | Integer | Name | Defining |
| | | | Specification |
+-----+---------+-----------------------------------+---------------+
| 0 | 32 | SW_ERROR | Software |
| | | | Message and |
| | | | Attributes |
| | | | for PA-TNC |
| | | | |
| 0 | 33 | SW_SUBSCRIPTION_DENIED_ERROR | Software |
| | | | Message and |
| | | | Attributes |
| | | | for PA-TNC |
| | | | |
| 0 | 34 | SW_RESPONSE_TOO_LARGE_ERROR | Software |
| | | | Message and |
| | | | Attributes |
| | | | for PA-TNC |
| | | | |
| 0 | 35 | SW_SUBSCRIPTION_FULFILLMENT_ERROR | Software |
| | | | Message and |
| | | | Attributes |
| | | | for PA-TNC |
| | | | |
| 0 | 36 | SW_SUBSCRIPTION_ID_REUSE_ERROR | Software |
| | | | Message and |
| | | | Attributes |
| | | | for PA-TNC |
| | | | |
| 0 | 37-47 | Reserved for future use | Software |
| | | | Message and |
| | | | Attributes |
| | | | for PA-TNC |
+-----+---------+-----------------------------------+---------------+
9.3. 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 | SW | Software Message and Attributes for |
| | | Attributes | PA-TNC |
+-----+---------+-------------+-------------------------------------+
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9.4. Registry for Software Data Models
TBD
10. References
10.1. 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.
10.2. Informative References
[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>.
Authors' Addresses
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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