One document matched: draft-ietf-nea-pa-tnc-00.txt
Network Working Group P. Sangster
Internet Draft Symantec Corporation
Intended status: Proposed Standard April 11, 2008
Expires: October 2008
PA-TNC: A Posture Attribute Protocol (PA) Compatible with TNC
draft-ietf-nea-pa-tnc-00.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document specifies PA-TNC, a Posture Attribute Protocol
identical to the Trusted Computing Group's IF-M 1.0 protocol.
The document then evaluates PA-TNC against the requirements
defined in the NEA Requirements specification.
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Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described
in RFC 2119 [1].
Table of Contents
1. Introduction.............................................. 3
1.1. Background on Trusted Computing Group................ 3
1.2. Background on Trusted Network Connect................ 4
1.3. Submission of This Document.......................... 4
1.4. Prerequisites........................................ 4
1.5. Message Diagram Conventions.......................... 5
2. PA-TNC Message Protocol................................... 5
2.1. PA-TNC Messaging Model............................... 5
2.2. PA-TNC Relationship to PB-TNC........................ 6
2.3. PA-TNC Messages in PB-TNC............................ 8
2.4. IETF Standard PA Subtypes............................ 9
2.5. PA-TNC Message Header Format.........................10
3. PA-TNC Attributes.........................................11
3.1. PA-TNC Attribute Header..............................12
3.2. IETF Standard PA-TNC Attribute Types.................16
3.2.1. Attribute Request...............................17
3.2.2. Product Information.............................19
3.2.3. Numeric Version.................................21
3.2.4. String Version..................................24
3.2.5. Operational Status..............................26
3.2.6. Port Filter.....................................29
3.2.7. Installed Packages..............................31
3.2.8. PA-TNC Error....................................34
3.2.8.1. Definition of Invalid Parameter Error Code 36
3.2.8.2. Definition of Version Not Supported Error
Code................................................37
3.2.8.3. Definition of Attribute Type Not Supported
Error Code..........................................39
3.3. Vendor-Defined Attributes............................41
4. Evaluation Against NEA Requirements.......................41
4.1. Evaluation Against Requirement C-1...................41
4.2. Evaluation Against Requirement C-2...................42
4.3. Evaluation Against Requirement C-3...................42
4.4. Evaluation Against Requirement C-4...................42
4.5. Evaluation Against Requirement C-5...................43
4.6. Evaluation Against Requirement C-6...................43
4.7. Evaluation Against Requirement C-7...................43
4.8. Evaluation Against Requirement C-8...................44
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4.9. Evaluation Against Requirement C-9...................44
4.10. Evaluation Against Requirement C-10 ................45
4.11. Evaluation Against Requirement PA-1 ................45
4.12. Evaluation Against Requirement PA-2 ................45
4.13. Evaluation Against Requirement PA-3 ................46
4.14. Evaluation Against Requirement PA-4 ................46
4.15. Evaluation Against Requirement PA-5 ................46
4.16. Evaluation Against Requirement PA-6 ................47
5. Security Considerations...................................47
5.1. Trust Relationships..................................48
5.1.1. Posture Collector...............................48
5.1.2. Posture Validator...............................48
5.1.3. Posture Broker Client, Posture Broker Server, and
PB-TNC.................................................49
5.2. Security Threats.....................................49
5.2.1. Attribute Theft.................................50
5.2.2. Message Fabrication.............................50
5.2.3. Attribute Modification..........................51
5.2.4. Attribute Replay................................51
5.2.5. Attribute Insertion.............................51
5.2.6. Denial of Service...............................52
6. Privacy Considerations....................................52
7. IANA Considerations.......................................54
7.1. New IETF Standard PA Subtypes........................54
7.2. Registry for IETF Standard PA-TNC Attribute Types....54
7.3. Registry for IETF Standard PA-TNC Error Codes........55
8. Acknowledgments ..........................................56
9. References ...............................................56
9.1. Normative References ................................56
9.2. Informative References...............................56
Author's Address.............................................57
Intellectual Property Statement..............................57
Disclaimer of Validity.......................................58
1. Introduction
This document specifies PA-TNC, a Posture Attribute Protocol
(PA) identical to the Trusted Computing Group's IF-M 1.0
protocol [6]. The document then evaluates PA-TNC against the
requirements defined in the NEA Requirements specification [7].
1.1. Background on Trusted Computing Group
The Trusted Computing Group (TCG) is a consortium that develops
specifications for trusted (secure) computing. Since its
formation in 2003, TCG has published specifications for a
variety of technologies such as Trusted Platform Module (TPM),
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TCG Software Stack (TSS), Mobile Trusted Module (MTM), and
Trusted Network Connect (TNC).
TCG members include more than 175 organizations that design,
build, sell, or use trusted computing technology. Membership is
open to any organization that signs the membership agreement and
pays the annual membership fee. Non-members are welcome to
implement the TCG specifications. Several open source
implementers have done so.
1.2. Background on Trusted Network Connect
Starting in 2004, the TCG has defined and published the Trusted
Network Connect (TNC) architecture and standards for network
access control. These standards enable multi-vendor
interoperability at all points in the architecture and have been
widely adopted and deployed.
1.3. Submission of This Document
The IETF has recently chartered the Network Endpoint Assessment
(NEA) working group to develop several standards in the same
area as TNC. In order to avoid the development of multiple
incompatible standards, the TCG is offering several of its TNC
standards to the IETF as candidates for standardization in the
IETF also. This document is equivalent to TCG's IF-M 1.0.
Consistent with IETF's requirements for standards track
documents, the TCG has authorized the editors of this document
to offer the specification to the IETF without restriction. As
with other Internet-Drafts, the IETF Trust owns the copyright to
this document. The IETF may modify this document, ignore it,
publish it as an RFC, or take any other action. If the IETF
decides to adopt a later version of this document as an RFC, the
TCG plans to publish a specification for an equivalent TNC
protocol to ensure compatibility.
1.4. Prerequisites
This document does not define an architecture or reference
model. Instead, it defines a protocol that works within the
reference model described in the NEA Requirements specification.
The reader is assumed to be thoroughly familiar with that
document. No familiarity with TCG specifications is assumed.
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1.5. Message Diagram Conventions
This specification defines the syntax of PA-TNC messages 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, traversing the diagram from top to
bottom and then from left to right within each line (which
represents a 32-bit quantity). Multi-byte fields representing
numeric values must be sent in network (big endian) byte order.
Descriptions of bit field (e.g. flag) values are described
referring to the position of the bit within the field. These
bit positions are numbered from the most significant bit through
the least significant bit so a one octet field with only bit 0
set has the value 0x80.
2. PA-TNC Message Protocol
This section discusses the use of the PA-TNC message and its
attributes, and specifies the syntax and semantics for the PA-
TNC message header. The details of each attribute included
within the PA-TNC payload are specified in section 3.2.
2.1. PA-TNC Messaging Model
PA-TNC messages are carried by the PB-TNC protocol [5], which
provides a multi-roundtrip reliable transport and end-to-end
message delivery to subscribed (interested) parties using a
variety of underlying network protocols. PA-TNC is unaware of
these underlying PT transport protocols being used below PB-TNC.
The interested parties consist of Posture Collectors on the NEA
Client and Posture Validators associated with the NEA Server
that have registered to receive messages about particular types
of components (e.g. anti-virus) during an assessment. The PA-
TNC messaging protocol operates synchronously within an
assessment session, with Posture Collectors and Posture
Validators taking turns sending one or more messages to each
other. Each PA-TNC message may contain one or more attributes
associated with the functional component defined in the PB
protocol. Posture Collectors may only send PA-TNC messages to
Posture Validators and vice versa. No Posture Collector to
Posture Collector or Posture Validator to Posture Validator
messaging is allowed to occur. Each Posture Collector or
Posture Validator may send several PA-TNC messages in succession
before indicating that it has completed its response to the
Posture Broker Client or Posture Broker Server respectively. As
necessary, the Posture Broker Client and Posture Broker Server
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will batch these messages prior to sending them over the
network.
PB-TNC provides a publish/subscribe model of message exchange.
This means that, at any given point in time, zero or more
subscribers for a particular type of message may be present on a
Posture Broker Client or Posture Broker Server. This is
beneficial, since it allows one Posture Collector or Posture
Validator to combine multiple functions (like anti-virus and
personal firewall) by subscribing to both TNC standard component
types. It also allows multiple Posture Collectors or Posture
Validators to support the same components, such as two anti-
virus Posture Validators that are each used to manage their own
respective anti-virus client software. However, this
publish/subscribe model has some possible negative side effects.
When a Posture Collector or Posture Validator initially sends a
PA-TNC message, it does not know whether it will receive many,
one, or no PA-TNC messages from the other side. For many types
of assessments, this is acceptable, but in some cases a more
direct channel binding between a particular Posture Collector
and Posture Validator pair is necessary. For example, a Posture
Validator may wish to provide remediation instructions to a
particular Posture Collector that it knows is capable of
remediating a non-compliant component. This can be accomplished
using the PB-TNC capability to limit distribution of a message
to a single Posture Collector.
2.2. PA-TNC Relationship to PB-TNC
This section summarizes the major elements of a PA-TNC message
as they might appear inside of a PB-TNC message. The double
line (===) in the diagram below indicates the separation between
the PB-TNC and PA-TNC protocols. The PA-TNC portion of the
message is delivered to each Posture Collector or Posture
Validator registered to receive messages containing a particular
message type. Note that PB-TNC is capable of carrying multiple
PB-TNC and PA-TNC messages in a single PB-TNC batch. See the
PB-TNC specification [5] for more information on its
capabilities.
One important linkage between the PA-TNC and PB-TNC protocols is
the PA message type (PA Message Vendor ID and PA subtype) that
is used by the Posture Broker Client and Posture Broker Server
to route messages to interested Posture Collectors and Posture
Validators. The message type indicates the software component
(component type) that is associated with the attributes included
inside the PA-TNC message. Therefore, Posture Collectors and
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Posture Validators written to support an assessment of a
particular component can register to receive messages about the
component and thus participate in its assessment. Each Posture
Collector and Posture Validator MUST only send PA-TNC messages
containing attributes that pertain to the software component
defined in the message type of the message. This assures that
only the appropriate Posture Collectors and Posture Validators
that support a particular type of component will receive
attributes related to that component. If a PA-TNC message
contained a mix of attributes about different components and a
message type of only one of those components, the message would
only be delivered to parties interested in the component type
included in the message type, so other interested recipients
wouldn't see those attributes.
The message type is comprised of 2 fields: a PA Message Vendor
ID and a PA Subtype. The PA Message Vendor ID identifies the
vendor or other organization that defined this message type. The
PA Subtype identifies the message type more particularly within
the set of message types defined by that vendor. This
specification defines several IETF Standard PA Subtypes to be
used with a PA Message Vendor ID of zero (0). Within this
specification, the PA Subtype field is used to indicate the type
of component (e.g. firewall) involved with the message's
attributes. Therefore for clarity the PA subtype will be
referred to as the "component type" in this specification.
Vendor-defined name spaces may use other semantics for the PA
Subtype field as this is outside the scope of this
specification.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PB-TNC Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PB-TNC Message of type PB-PA-Message |
| (includes PA Message Vendor ID, PA Subtype, and other fields|
| used by Posture Broker Client and Posture Broker Server for |
| routing) |
===============================================================
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Message Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute |
| (e.g. Product Information) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute |
| (e.g. Operational Status) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 Overview of a PB-TNC batch that contains a PA-TNC
Message
For example, if a Posture Broker Client sent a PB-TNC batch that
contained a PA-TNC message with a message type indicating
firewall component, this message would be routed by the Posture
Broker Server to Posture Validators registered to assess
firewalls. Each registered Posture Validator would receive a
copy of the PA-TNC message including the PA-TNC header and set
of attributes. It is important that each of the attributes
included in the PA-TNC message be associated with the firewall
component because only the Posture Collector and Posture
Validator interested in firewalls will receive such messages.
For example, if the above message contained both firewall and
operating system attributes (inside a PA-TNC message with a
component type of firewall), then any Posture Collector and
Posture Validator registered to receive operating system
messages would not receive those attributes, as the messages
would only be delivered to those registered for firewall
messages.
2.3. PA-TNC Messages in PB-TNC
As depicted in section 2.2, a PA-TNC message consists of a PA-
TNC header followed by a sequence of one or more attributes. The
PA-TNC message header (described in section 2.5) and the header
for each of the PA-TNC attributes (specified in section 3.1)
have a fixed type-length-value (TLV) format. Each PA-TNC
message MAY contain a mixture of standards-based and vendor-
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defined attributes identifiable using the type portion of the
attribute header. All Posture Collectors and Posture Validators
compliant with this specification MUST be capable of processing
multiple attributes in a received PA-TNC message. A Posture
Collector or Posture Validator that receives a PA-TNC message
can use the attribute header's length field to skip any
attributes that it does not understand, unless the attribute is
marked as mandatory to process.
2.4. IETF Standard PA Subtypes
This section defines several IETF Standard PA Subtypes. Each PA
subtype defined here identifies a specific component relevant to
the endpoint's posture. This allows a small set of generic PA-
TNC attributes (e.g. Product Information) to be used to describe
a large number of different components (e.g. OS, anti-virus
software, etc.). It also allows Posture Collectors and Posture
Validators to specialize in a particular component (e.g.
operating system) and only receive PA-TNC messages relevant to
that component.
Number Name Definition
------ ---- ----------
0 Testing Reserved for use in specification
examples, experimentation and
testing.
1 Operating System Operating system running on the
endpoint
2 Anti-Virus Host-based anti-virus software
3 Anti-Spyware Host-based anti-spyware software
4 Anti-Malware Host-based anti-malware (e.g. anti-
bot) software not included within
anti-virus or anti-spyware components
5 Firewall Host-based firewall
6 IDPS Host-based Intrusion Detection and/or
Prevention Software (IDPS)
7 VPN Host-based Virtual Private Networking
(VPN) software
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These PA subtypes must be used in a PB-PA message with a PA
Message Vendor ID of zero (0) (as described in the PB-TNC
specification [5]). If these PA subtype values are used with a
different PA Message Vendor ID, they have a completely different
meaning that is not defined in this specification.
2.5. PA-TNC Message Header Format
This section describes the format and semantics of the PA-TNC
header. Every PA-TNC message MUST start with a PA-TNC header.
The PA-TNC header provides a common context applying to all of
the attributes contained within the PA-TNC payload. The payload
consists of a sequence of assessment attributes described in
section 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version
This field indicates the version of the format for the PA-TNC
message. This version is intended to allow for evolution of
the PA-TNC message header and payload in a manner that can
easily be detected by message recipients.
PA-TNC message senders MUST set this field to 0x01 for all
PA-TNC messages that comply with formats and requirements
described in version 1.0 of this specification.
Implementations responding to a PA-TNC message containing a
supported version SHOULD use the same Version number to
minimize the risk of version incompatibility.
Message senders MAY send an empty PA-TNC message with the
Version value set to 0 in order to discover the PA-TNC
protocol versions supported by peer recipients (see PA-TNC
Error Code information in section 3.2.8). Message recipients
MUST NOT support version 0 and MUST NOT interpret the
contents (after the Version field) of a PA-TNC message
containing a version number that the recipient does not
support. Message recipients MUST respond to a PA-TNC message
with an unsupported version by sending a Version Not
Supported error code in a PA-TNC Error attribute.
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PA-TNC message initiators supporting multiple PA-TNC protocol
versions SHOULD be able to alter which version of PA-TNC
message they send based on prior message exchanges with a
particular peer Posture Collector or Posture Validator.
Reserved
Reserved for future use. This field MUST be set to 0 on
transmission and ignored upon reception.
Message Identifier
This field contains a value that uniquely identifies this
message, differentiating it from others sent by a particular
PA-TNC message sender within this assessment. This value can
be included in a response message to indicate which message
was received and caused the response. For example, this
field is included in the PA-TNC error messages so the party
who receives the error message can determine which of the
messages they had sent caused the error.
PA-TNC message senders MUST NOT send the same message
identifier more than once during an assessment. Message
identifiers may be randomly generated or sequenced as long as
values are not repeated during an assessment message
exchange. PA-TNC message recipients are not required to
check for duplicate message identifiers.
3. PA-TNC Attributes
This section defines the PA-TNC attributes that can be carried
within a PA-TNC message. The initial section defines the
standard attribute header that appears at the start of each
attribute in a PA-TNC message. The second section defines each
of the IETF Standard PA-TNC attributes and the final section
discusses how vendor-defined PA-TNC attributes can be used
within a PA-TNC message. Vendor-defined PA-TNC attributes use
the vendor's SMI Private Enterprise Number in the Attribute Type
field.
A PA-TNC message MUST contain a PA-TNC header (defined in
section 2.5) followed by a sequence of zero or more PA-TNC
attributes. All PA-TNC attributes MUST begin with a standard PA-
TNC attribute header, as defined in section 3.1. The contents
of PA-TNC attributes vary widely, depending on their attribute
type. Section 3.2 defines the IETF Standard PA-TNC Attributes.
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Section 3.3 discusses how vendor-specific PA-TNC attributes can
be defined.
3.1. PA-TNC Attribute Header
Following the PA-TNC message header is a sequence of zero or
more attributes. All PA-TNC attributes MUST begin with the
standard PA-TNC attribute header defined in this subsection.
Each attribute described in this specification is represented by
a TLV tuple. The TLV tuple includes an attribute identifier
comprised of the Vendor ID and Attribute Type (type), the TLV
tuple's overall length and finally the attribute's value. The
use of TLV representation was chosen due to its flexibility and
extensibility and use in other standards. Recipients of an
attribute can use the attribute type fields to determine the
precise syntax and semantics of the attribute value field and
the length to skip over an unrecognized attribute. The length
field is also beneficial when a variable length attribute value
is provided.
The TLV format does not contain an explicit TLV format version
number, so every attribute included in a particular PA-TNC
message MUST use the same TLV format. Using the PA-TNC message
version number to indicate the format of all TLV attributes
within a PA-TNC message allows for future versioning of the TLV
format in a manner detectable by PA-TNC message recipients.
Similarly, requiring all TLV attribute formats to be the same
within a PA-TNC message also assures that recipients compliant
with a particular PA-TNC message version can at least parse
every attribute header and use the length to skip over
unrecognized attributes. Every PA-TNC 1.0 compliant TLV
attribute MUST use the following TLV format:
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | PA-TNC Attribute Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Correlation ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Value (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags
This field defines flags impacting the processing of the
associated attribute.
Bit 0 (0x80) is the NOSKIP flag. Any Posture Collector or
Posture Validator that receives an attribute with this flag
set to 1 but does not support this attribute MUST NOT process
any part of the PA-TNC message and SHOULD respond with an
Attribute Type Not Supported error in a PA-TNC error message.
In order to avoid taking action on a subset of the attributes
only to later find an unsupported attribute with the NOSKIP
flag set, recipients of a multi-attribute PA-TNC message
might need to scan all of the attributes prior to acting upon
any attribute.
When the NOSKIP flag is set to 0, recipients SHOULD skip any
unsupported attributes and continue processing the next
attribute.
Bit 1 (0x40) is the Correlation ID (COR) flag. This flag
indicates whether the optional Correlation ID value is
included in the header. When set to 1, a 32 bit Correlation
ID field is present. Otherwise when set to 0, no Correlation
ID is included.
Bit 2-7 are reserved for future use. These bits MUST be set
to 0 on transmission and ignored upon reception.
PA-TNC Attribute Vendor ID
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This field indicates the owner of the name space associated
with the PA-TNC Attribute Type. This is accomplished by
specifying the 24 bit SMI Private Enterprise Number Vendor ID
of the party who owns the Attribute Type name space. IETF
Standard PA-TNC Attribute Types MUST use zero (0) in this
field.
The PA-TNC Attribute Vendor ID 0xffffff is reserved. Posture
Collectors and Posture Verifiers MUST NOT send PA-TNC
messages in which the PA-TNC Attribute Vendor ID has this
reserved value (0xffffff). If a Posture Collector or Posture
Verifier receives a message in which the PA-TNC Attribute
Vendor ID has this reserved value (0xffffff), it SHOULD
respond with an Invalid Parameter error code in a PA-TNC
Error attribute.
PA-TNC Attribute Type
This field defines the type of the attribute included in the
Attribute Value field. This field is qualified by the PA-TNC
Attribute Vendor ID field so that a particular PA-TNC
Attribute Type value (e.g. 327) has a completely different
meaning depending on the value in the PA-TNC Attribute Vendor
ID field.
If the PA-TNC Attribute Vendor ID field has the value zero
(0) then the PA-TNC Attribute Type field contains an IETF
Standard PA-TNC Attribute Type, as listed in the IANA
registry. Section 3.2 of this specification defines the
initial set of IETF Standard PA-TNC Attribute Types.
The PA-TNC Attribute Type 0xffffffff is reserved. Posture
Collectors and Posture Verifiers MUST NOT send PA-TNC
messages in which the PA-TNC Attribute Type has this reserved
value (0xffffffff). If a Posture Collector or Posture
Verifier receives a message in which the PA-TNC Attribute
Type has this reserved value (0xffffffff), it SHOULD respond
with an Invalid Parameter error code in a PA-TNC Error
attribute.
PA-TNC Attribute Length
This field contains the length in octets of the entire PA-TNC
Attribute including the PA-TNC Attribute Header (the fields
Flags, PA-TNC Attribute Vendor ID, PA-TNC Attribute Type, and
PA-TNC Attribute Length). Therefore, this value MUST always
be at least 12 (16 if the Correlation ID is present). Any
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Posture Collector or Posture Verifier that receives a message
with a PA-TNC Attribute Length field whose value is less than
12 (16 if the Correlation ID is present) SHOULD respond with
an Invalid Parameter PA-TNC error code.
Implementations that do not support the specified PA-TNC
Attribute Type can use this length to skip over this
attribute to the next attribute. Note that while this field
is 4 octets the maximum usable attribute length is likely to
be less than 2^32-1 due to limitations of the underlying
protocol stack.
Correlation ID
This optional field MUST be present when the COR flag is set
to 1 and MUST NOT be present when the COR flag is set to 0.
Normally, this field will not be present. However, there are
times when this field is necessary.
Some Posture Collectors may wish to report on several
products with the same component ID on an endpoint (e.g. two
anti-malware software packages). In this case, the Posture
Collector and Posture Validator need a way to identify the
different products. For example, if a Posture Validator
requests Product Information and Numeric Version attributes
for the anti-malware component, this Posture Collector would
produce two Product Information and two Numeric Version
attributes, each attribute having a Correlation ID specific
to the product being described. The Product Information and
Numeric Version attributes describing the same product would
have the same Correlation ID. This allows the Posture
Validator to associate the Product Information and Numeric
Version attributes that apply to a single product. Because
the Product Information and Numeric Version attribute
requests might be requested at different times, it is
important that the Posture Collector use a consistent value
for each product upon which it is able to report. A Posture
Collector might create a persistent table of locally unique
IDs (e.g. counters) for each product upon which it reports,
for situations where a Correlation ID is necessary.
Note that many Posture Collectors will not need to worry
about Correlation IDs because they will only support
reporting on one product per endpoint. If an endpoint has two
anti-malware Posture Collectors installed that each support
only one product and those Posture Collectors are reporting
on two separate anti-malware products, the Correlation ID is
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not required. This is because the Posture Validator can use
the Posture Collector ID reported in the PB-TNC protocol to
associate the attributes sent by each Posture Collector.
When a single Posture Collector needs to send several
attributes in a single assessment that pertain to separate
products but have the same PA Message Vendor ID and PA
Subtype, the Posture Collector MUST use the Correlation ID
field. The Correlation ID value MUST be constant per product
for an entire PB-TNC session so that the Posture Validator
can correlate attributes requested earlier about the same
product. The Posture Validator MAY send attributes with a
Correlation ID to identify the product to which they pertain.
Attribute Value
This field varies depending on the particular type of
attribute being expressed. The contents of this field for
each of the IETF Standard PA-TNC Attribute Types is defined
in section 3.2.
3.2. IETF Standard PA-TNC Attribute Types
This section defines an initial set of IETF Standard PA-TNC
Attribute Types. These Attribute Types MUST always be used with
a PA-TNC Vendor ID of zero (0). If these PA-TNC Attribute Type
values are used with a different PA-TNC Vendor ID, they have a
completely different meaning that is not defined in this
specification.
The following table briefly describes each attribute and defines
the numeric value to be used in the PA-TNC Attribute Type field
of the PA-TNC Attribute Header. Later subsections provide
detailed specifications for each PA-TNC Attribute Value.
Number Name Description
------ ---- -----------
0 Testing Reserved for use in
specification examples,
experimentation and testing.
1 Attribute Request Contains a list of attribute
type values defining the
attributes desired from the
Posture Collectors.
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2 Product Information Manufacturer and product
information for the component.
3 Numeric Version Numeric version of the
component.
4 String Version String version of the
component.
5 Operational Status Describes whether the component
is running on the endpoint.
6 Port Filter Lists the set of ports (e.g.
TCP port 80 for HTTP) that are
allowed or blocked on the
endpoint.
7 Installed Packages List of software packages
installed on endpoint that
provide the requested
component.
8 PA-TNC Error PA-TNC message or attribute
processing error.
The following subsections discuss the usage, format and
semantics of the Attribute Value field for each IETF Standard
PA-TNC Attribute Type.
3.2.1. Attribute Request
This PA-TNC Attribute Type allows a Posture Validator to request
certain attributes from the registered set of Posture
Collectors.
All Posture Collectors that implement any of the IETF Standard
PA Subtypes defined in this specification SHOULD support
receiving and processing this attribute type for at least those
PA subtypes. Posture Collectors that receive and process this
attribute MAY choose to send all, a subset or none of the
requested attributes but MUST NOT send attributes that were not
requested (except error attributes). All Posture Validators
that implement any of the IETF Standard PA Subtypes defined in
this specification SHOULD support sending this attribute type
for at least those PA subtypes.
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Posture Verifiers MUST NOT include this attribute type in an
Attribute Request attribute. It does not make sense for a
Posture Verifier to request that a Posture Collector send an
Attribute Request attribute.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 1.
The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
Note that this diagram shows two attribute types. The actual
number of attribute types included in an Attribute Request
attribute can vary from one to a large number (limited only by
the maximum message and length supported by the underlying PT
transport protocol). However, each Attribute Request MUST
contain at least one attribute type. Because the length of a
PA-TNC Attribute Vendor ID paired with a PA-TNC Attribute Type
and a one octet Reserved field is always 8 octets, the number of
requested attributes can be easily computed using the PA-TNC
Attribute Length field by subtracting the number of octets in
the PA-TNC Attribute Header and dividing by 8. If the PA-TNC
Attribute Length field is invalid, Posture Collectors SHOULD
respond with an Invalid Parameter PA-TNC error code.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | PA-TNC Attribute Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | PA-TNC Attribute Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved
Reserved for future use. This field MUST be set to 0 on
transmission and ignored upon reception.
PA-TNC Attribute Vendor ID
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This field contains the SMI Private Enterprise Number of the
organization that controls the name space for the following
PA-TNC Attribute Type. This field enables IETF Standard PA-
TNC Attributes and vendor-defined PA-TNC Attributes to be
used without potential collisions.
Any IETF Standard PA-TNC Attribute Types defined in section
3.2 MUST use zero (0) in this field. Vendor-defined
attributes MUST use the SMI Private Enterprise Number of the
organization that defined the attribute.
PA-TNC Attribute Type
The PA-TNC Attribute Type field (together with the PA-TNC
Vendor ID field) indicates the specific attribute requested.
Some IETF Standard PA-TNC Attribute Types MUST NOT be
requested using this field (e.g. requesting a PA-TNC Error
attribute). This is explicitly indicated in the description
of those PA-TNC Attribute Types. Any Posture Collector or
Posture Validator that receives an Attribute Request
containing one of the prohibited Attribute Types SHOULD
respond with an Invalid Parameter error in a PA-TNC error
message.
3.2.2. Product Information
This PA-TNC Attribute Type contains identifying information
about a product that implements the component specified in the
PA Subtype field, as described in section 2.4. For example, if
the PA Subtype is Anti-Virus, this attribute would contain
information identifying an anti-virus product installed on the
endpoint.
All Posture Collectors that implement any of the IETF Standard
PA Subtypes defined in this specification MUST support sending
this attribute type, at least for those PA subtypes. Whether a
particular Posture Collector actually sends this attribute type
SHOULD still be governed by local privacy and security policies.
All Posture Validators that implement any of the IETF Standard
PA Subtypes defined in this specification MUST support receiving
this attribute type, at least for those PA subtypes. Posture
Validators MUST NOT send this attribute type.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 2. The value in the PA-TNC Attribute Length field
will vary, depending on the length of the Product Name field.
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However, the value in the PA-TNC Attribute Length field MUST be
at least 17 (21 if the Correlation ID field is present) because
this is the length of the fixed size fields in the PA-TNC
Attribute Header and the fixed size fields in this attribute
type. If the PA-TNC Attribute Length field is less than the
size of these fixed length fields, implementations SHOULD
respond with an Invalid Parameter PA-TNC error code.
This attribute type includes both numeric and textual
identifiers for the organization that created the product (the
"product creator") and for the product itself. For automated
processing, numeric identifiers are superior because they are
less ambiguous and more efficient. However, numeric identifiers
are only available if the product creator has assigned them.
Therefore, a textual identifier is also included. This textual
identifier has the additional benefit that it may be easier for
humans to read (although this benefit is minimal since the
primary purpose of this attribute is automated assessment).
The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Product Vendor ID | Product ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Product ID | Product Name (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Product Vendor ID
This field contains the SMI Private Enterprise Number for the
product creator. If the SMI PEN for the product creator is
unknown or if the product creator does not have an SMI PEN,
the Product Vendor ID field MUST be set to 0 and the identity
of the product creator SHOULD be included in the Product Name
along with the name of the product.
Product ID
This field identifies the product using a numeric identifier
assigned by the product creator. If this Product ID value is
unknown or if the product creator has not assigned such a
value, this field MUST be set to 0. If the Product Vendor ID
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is 0, this field MUST be set to 0. In any case, the name of
the product SHOULD be included in the Product Name field.
Note that a particular Product ID value (e.g. 635) will have
completely different meanings depending on the Product Vendor
ID. Each Product Vendor ID defines a different space of
Product ID values. Product creators are encouraged to publish
lists of Product ID values for their products.
Product Name
This variable length field contains a UTF-8 [2] string
identifying the product (e.g. "Symantec Norton AntiVirus(TM)
2008") in enough detail to unambiguously distinguish it from
other products from the product creator. Products whose
creator is known, but does not have a registered SMI Private
Enterprise Number, SHOULD be represented using a combination
of the creator name and full product name (e.g. "Ubuntu(R)
IPtables" for the IPtables firewall in the Ubuntu
distribution of Linux). If the product creator's SMI Private
Enterprise Number is included in the Product Vendor ID field,
the product creator's name may be omitted from this field.
The length of this field can be determined by starting with
the value in the PA-TNC Attribute Length field in the PA-TNC
Attribute Header and subtracting the size of the fixed length
fields in that header (12 or 16, depending on whether the
Correlation ID is present) and the size of the fixed length
fields in this attribute (5). If the PA-TNC Attribute Length
field is less than the size of these fixed length fields,
implementations SHOULD respond with an Invalid Parameter PA-
TNC error code.
3.2.3. Numeric Version
This PA-TNC Attribute Type contains numeric version information
for a product on the endpoint that implements the component
specified in the PA Subtype field, as described in section 2.4.
For example, if the PA Subtype is Operating System, this
attribute would contain numeric version information for the
operating system installed on the endpoint. The version
information in this attribute is associated with a particular
product, so Posture Validators are expected to also possess the
corresponding Product Information attribute when interpreting
this attribute.
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All Posture Collectors that implement the IETF Standard PA
Subtype for Operating System SHOULD support sending this
attribute type, at least for the Operating System PA subtype.
Other Posture Collectors MAY support sending this attribute
type. Whether a particular Posture Collector actually sends
this attribute type SHOULD still be governed by local privacy
and security policies. All Posture Validators that implement
the IETF Standard PA Subtype for Operating System SHOULD support
receiving this attribute type, at least for the Operating System
PA subtype. Other Posture Validators MAY support receiving this
attribute type. A Posture Validator that does not support
receiving this attribute type SHOULD simply ignore attributes
with this type. Posture Validators MUST NOT send this attribute
type.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 3. The value in the PA-TNC Attribute Length field
MUST be 28 if the Correlation ID field is not present and 32 if
it is present. If the PA-TNC Attribute Length field is less
than the size of these fixed length fields, implementations
SHOULD respond with an Invalid Parameter PA-TNC error code.
This attribute type includes numeric values for the product
version information, enabling Posture Validators to do
comparative operations on the version. Some Posture Collectors
may not be able to determine some or all of this information for
a product. However, this attribute can be especially useful for
describing the version of the operating system, where numeric
version numbers are generally available.
The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Major Version Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minor Version Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Build Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Pack Major | Service Pack Minor |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Major Version Number
This field contains the major version number for the product,
if applicable. If unused or unknown, this field SHOULD be set
to 0.
Minor Version Number
This field contains the minor version number for the product,
if applicable. If unused or unknown, this field SHOULD be set
to 0.
Build Number
This field contains the build number for the product, if
applicable. This may provide more granularity than the minor
version number, as many builds may occur leading up to an
official release, and all these builds may share a single
major and minor version number. If unused or unknown, this
field SHOULD be set to 0.
Service Pack Major
This field contains the major version number of the service
pack for the product, if applicable. If unused or unknown,
this field SHOULD be set to 0.
Service Pack Minor
This field contains the minor version number of the service
pack for the product, if applicable. If unused or unknown,
this field SHOULD be set to 0.
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3.2.4. String Version
This PA-TNC Attribute Type contains string version information
for a product on the endpoint that implements the component
specified in the PA Subtype field, as described in section 2.4.
For example, if the PA Subtype is Firewall, this attribute would
contain string version information for a host-based firewall
product installed on the endpoint (if any). The version
information in this attribute is associated with a particular
product, so Posture Validators are expected to also possess the
corresponding Product Information attribute when interpreting
this attribute.
All Posture Collectors that implement any of the IETF Standard
PA Subtypes defined in this document MUST support sending this
attribute type, at least for those PA subtypes. Other Posture
Collectors MAY support sending this attribute type. Whether a
particular Posture Collector actually sends this attribute type
SHOULD still be governed by local privacy and security policies.
All Posture Validators that implement any of the IETF Standard
PA Subtypes defined in this document MUST support receiving this
attribute type, at least for those PA subtypes. Other Posture
Validators MAY support receiving this attribute type. Posture
Validators MUST NOT send this attribute type.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 4. The value in the PA-TNC Attribute Length field
will vary, depending on the length of the Component Version
Number, Internal Build Number, and Configuration Version Number
fields. However, the value in the PA-TNC Attribute Length field
MUST be at least 15 (19 if the Correlation ID field is present)
because this is the length of the fixed size fields in the PA-
TNC Attribute Header and the fixed size fields in this attribute
type. If the PA-TNC Attribute Length field is less than the
size of these fixed length fields or does not match the length
indicated by the sum of the fixed length and variable length
fields, implementations SHOULD respond with an Invalid Parameter
PA-TNC error code.
The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version Len | Product Version Number (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Build Num Len | Internal Build Number (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Config. Len | Configuration Version Number (Variable Length)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version Len
This field defines the number of octets in the Product
Version Number field. If the product version number is
unavailable or unknown, this field MUST be set to 0 and the
Product Version Number field will be zero length (effectively
not present).
Product Version Number
This field contains a UTF-8 string identifying the version of
the component (e.g. "1.12.23.114"). This field MUST be sized
to fit the version string and MUST NOT include extra octets
for padding or NUL character termination.
Various products use a wide range of different formats and
semantics for version strings. Some use alphabetic
characters, white space, and punctuation. Some consider
version "1.21" to be later than version "1.3" and some
earlier. Therefore, the syntax and semantics of this string
are not defined.
Build Num Len
This field defines the number of octets in the Internal Build
Number field. For products where the internal build number
is unavailable or unknown, this field MUST be set to 0 and
the Internal Build Number field will be zero length
(effectively not present).
Internal Build Number
This field contains a UTF-8 string identifying the
engineering build number of the product. This field MUST be
sized to fit the build number string and MUST NOT include
extra octets for padding or NUL character termination. The
syntax and semantics of this string are not defined.
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Config. Len
This field defines the number of octets in the Configuration
Version Number field. If the product version number is
unavailable or unknown, this field MUST be set to 0 and the
Product Version Number field will be zero length (effectively
not present).
Configuration Version Number
This field contains a UTF-8 string identifying the version of
the configuration used by the component. This version SHOULD
represent the overall configuration version even if several
configuration policy files or settings are used. Posture
Collectors MAY include multiple version numbers in this
single string if a single version is not practical. This
field MUST be sized to fit the version string and MUST NOT
include extra octets for padding or NUL character
termination.
Various products use a wide range of different formats for
version strings. Some use alphabetic characters, white
space, and punctuation. Some consider version "1.21" to be
later than version "1.3" and some earlier. In addition, some
Posture Collectors may place multiple configuration version
numbers in this single string. Therefore, the syntax and
semantics of this string are not defined.
3.2.5. Operational Status
This PA-TNC Attribute Type describes the operational status of a
product that can implement the component specified in the PA
Subtype field, as described in section 2.4. For example, if the
PA Subtype is Anti-Spyware, this attribute would contain
information about the operational status of a host-based anti-
spyware product that may or may not be installed on the
endpoint.
Posture Collectors that implement the IETF Standard PA Subtype
for Operating System or VPN MAY support sending this attribute
type for those PA subtypes. Posture Collectors that implement
other IETF Standard PA Subtypes defined in this specification
SHOULD support sending this attribute type for those PA
subtypes. Other Posture Collectors MAY support sending this
attribute type. Whether a particular Posture Collector actually
sends this attribute type SHOULD still be governed by local
privacy and security policies. Posture Validators that
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implement the IETF Standard PA Subtype for Operating System or
VPN MAY support receiving this attribute type, at least for
those PA subtypes. Posture Validators that implement other IETF
Standard PA Subtypes defined in this specification SHOULD
support receiving this attribute type, at least for those PA
subtypes. Other Posture Validators MAY support receiving this
attribute type. A Posture Validator that does not support
receiving this attribute type SHOULD simply ignore attributes
with this type. Posture Validators MUST NOT send this attribute
type.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 5. The value in the PA-TNC Attribute Length field
MUST be 36 if the Correlation ID field is not present and 40 if
it is present. If the PA-TNC Attribute Length field does not
have this value, implementations SHOULD respond with an Invalid
Parameter PA-TNC error code.
The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
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 | Result | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Use |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Use (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Use (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Use (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Use (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Status
This field gives the operational status of the product. The
following table lists the values currently defined for this
field. As described in section 7, the IANA maintains a
registry of valid values for this field so that new values
can be defined.
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Value Description
----- -----------
0 Unknown or other
1 Not installed
2 Installed but not operational
3 Operational
If a Posture Validator receives a value for this field that
it does not recognize, it SHOULD treat this value as
equivalent to the value 0.
Result
This field contains the result of the last use of the
product. The following table lists the values currently
defined for this field. As described in section 7, the IANA
maintains a registry of valid values for this field so that
new values can be defined.
Value Description
----- -----------
0 Unknown or other
1 Successful use with no errors detected
2 Successful use with one or more errors detected
3 Unsuccessful use (e.g. aborted)
Posture Collectors SHOULD set this field to 0 if the Status
field contains a value of 1 (Not installed) or 2 (Installed
but not operational). If a Posture Validator receives a
value for this field that it does not recognize, it SHOULD
treat this value as equivalent to the value 0.
Reserved
This field is reserved for future use. The field MUST be set
to 0 on transmission and ignored upon reception.
Last Use
This field contains the date and time of the last use of the
component. The Last Use date and time MUST be represented as
an RFC 3339 [4] 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.
Leap seconds are permitted and Posture Validators MUST
support them. The last use string MUST NOT be NUL terminated
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or padded in any way. If the last use time is not known, not
applicable, or cannot be represented in this format, the
Posture Collector MUST set this field to the value "0000-00-
00T00:00:00Z" (allowing this field to be fixed length). Not
that this particular reserved value is NOT a valid RFC 3339
date and time and MUST NOT be used for any other purpose in
this field.
This encoding produces a string that is easy to read, parse,
and interpret. The format (more precisely defined in RFC
3339) is YYYY-MM-DDTHH:MM:SSZ, resulting in one and only one
representation for each second in UTC time from year 0000 to
year 9999. For example, 9:05:00AM EST (GMT-0500) on January
19, 1995 can be represented as "1995-01-19T14:05:00Z". The
length of this field is always 20 octets.
3.2.6. Port Filter
This PA-TNC Attribute Type provides the list of port numbers and
associated protocols (e.g. TCP and UDP) that are currently
blocked or allowed by a host-based firewall on the endpoint.
Posture Collectors that implement the IETF Standard PA Subtype
for Firewall or VPN SHOULD support sending this attribute type
for those PA subtypes. Posture Collectors that implement other
IETF Standard PA Subtypes defined in this specification MUST NOT
support sending this attribute type for those PA subtypes.
Other Posture Collectors MAY support sending this attribute
type, if it is appropriate to their PA subtype. Whether a
particular Posture Collector actually sends this attribute type
SHOULD still be governed by local privacy and security policies.
Posture Validators that implement the IETF Standard PA Subtype
for Firewall or VPN SHOULD support receiving this attribute
type, at least for those PA subtypes. Posture Validators that
implement other IETF Standard PA Subtypes defined in this
specification MUST NOT support receiving this attribute type for
those PA subtypes. Other Posture Validators MAY support
receiving this attribute type. A Posture Validator that does
not support receiving this attribute type SHOULD simply ignore
attributes with this type. Posture Validators MUST NOT send
this attribute type.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 6.
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The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
Note that this diagram shows two Protocol/Port Number pairs. The
actual number of Protocol/Port Number pairs included in a Port
Filter attribute can vary from one to a large number (limited
only by the maximum message and length supported by the
underlying PT transport protocol). However, each Port Filter
attribute MUST contain at least one Protocol/Port Number pair.
Because the length of a Protocol/Port Number pair with the
Reserved field and B flag is always 4 octets, the number of
Protocol/Port Number pairs can be easily computed using the PA-
TNC Attribute Length field by subtracting the number of octets
in the PA-TNC Attribute Header and dividing by 4. If the PA-TNC
Attribute Length field is invalid, Posture Validators SHOULD
respond with an Invalid Parameter PA-TNC error code.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |B| Protocol | Port Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |B| Protocol | Port Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved
This field is reserved for future use. It MUST be set to 0
on transmission and ignored upon reception.
B Flag (Blocked or Allowed Port)
This single bit field indicates whether the following port is
blocked or allowed. This bit MUST be set to 1 if the
protocol and port combination is blocked. Otherwise this
field MUST be set to 0. This field was provided to allow for
more abbreviated reporting of the port filtering policy (e.g.
when all ports are blocked except a few, the Posture
Collector can just list the few that are allowed).
Posture Collectors MUST NOT provide a mixed list of block and
non-blocked ports for a particular protocol. To be more
precise, a Posture Collector MUST NOT include two
Protocol/Port Number pairs in a single Port List attribute
where the protocol number is the same but the B flag is
different. Also, Posture Collectors MUST NOT list the same
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Protocol and Port Number combination twice in a Port List
attribute.
Posture Collectors MAY list all blocked ports for one
protocol and all allowed ports for a different protocol in a
single Port List attribute, using the B flag to indicate
whether each entry is blocked. For example, a Posture
Collector might list all the blocked TCP ports but only list
the allowed UDP ports. However it MUST NOT list some blocked
TCP ports and some other allowed TCP ports.
Protocol
This field contains the protocol number being blocked or
allowed. The values used in this field are the same ones used
in the IPv4 Protocol and IPv6 Next Header fields. The IANA
already maintains a registry of these values.
Port Number
This field contains the port number being blocked or allowed.
The values used in this field are specific to the protocol
identified by the Protocol field. The IANA maintains
registries for TCP and UDP port numbers.
3.2.7. Installed Packages
This PA-TNC Attribute Type contains a list of the installed
packages that comprise a product on the endpoint that implements
the component specified in the PA Subtype field, as described in
section 2.4. This allows a Posture Validator to check which
packages are installed for a particular product and which
versions of those packages are installed.
Posture Collectors that implement any of the IETF Standard PA
Subtypes defined in this document SHOULD support sending this
attribute type for those PA subtypes. Other Posture Collectors
MAY support sending this attribute type, if it is appropriate to
their PA subtype. Whether a particular Posture Collector
actually sends this attribute type SHOULD still be governed by
local privacy and security policies. Posture Validators that
implement any of the IETF Standard PA Subtypes defined in this
document SHOULD support receiving this attribute type, at least
for those PA subtypes. Other Posture Validators MAY support
receiving this attribute type. A Posture Validator that does
not support receiving this attribute type SHOULD simply ignore
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attributes with this type. Posture Validators MUST NOT send
this attribute type.
This attribute type can be quite long, especially for the
Operating System PA subtype. This can cause problems, especially
with 802.1X and other limited transport protocols. Therefore,
Posture Collectors SHOULD NOT send this attribute unless
specifically requested to do so using the Attribute Request
attribute or otherwise configured to do so. Also, Posture
Validators SHOULD NOT request this attribute unless the
transport protocol in use can support the large amount of data
that may be sent in response.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 7. The value in the PA-TNC Attribute Length field
will vary, depending on the number of packages and the length of
the Package Name and Package Version Number fields for those
packages. However, the value in the PA-TNC Attribute Length
field MUST be at least 16 (20 if the Correlation ID field is
present) because this is the length of the fixed size fields in
the PA-TNC Attribute Header and the fixed size fields in this
attribute type. If the PA-TNC Attribute Length field is less
than the size of these fixed length fields or does not match the
length indicated by the sum of the fixed length and variable
length fields, implementations SHOULD respond with an Invalid
Parameter PA-TNC error code.
The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
Note that this diagram shows an attribute containing information
on one package. The actual number of package descriptions
included in an Installed Packages attribute is indicated by the
Package Count field. This value may vary from zero to a large
number (up to 65535, if the underlying PT transport protocol can
support that many). If this number is not sufficient,
specialized patch management software should be employed which
can simply report compliance with a pre-established patch
policy.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Package Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pkg Name Len | Package Name (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version Len | Package Version Number (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved
This field is reserved for future use. The field MUST be set
to 0 on transmission and ignored upon reception.
Package Count
This field is an unsigned 16-bit integer that indicates the
number of packages listed in this attribute. For each
package so indicated, a Pkg Name Len, Package Name, Version
Len, and Package Version Number field is included in the
attribute.
Pkg Name Len
This field is an unsigned 8-bit integer that indicates the
length of the Package Name field in octets. This field may be
zero if a Package Name is not available.
Package Name
This field contains the name of the package associated with
the product. This field is a UTF-8 encoded character string
whose octet length is given by the Pkg Name Len field. This
field MUST NOT include extra octets for padding or NUL
character termination. The syntax and semantics of this name
are not specified in this document, since they may vary
across products and/or operating systems. Posture Collectors
MAY list two packages with the same name in a single
Installed Packages attribute. The meaning of doing so is not
defined here.
Version Len
This field is an unsigned 8-bit integer that indicates the
length of the Package Version Number field in octets. This
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field may be zero if a Package Version Number is not
available.
Package Version Number
This field contains the version string for the package named
in the previous Package Name field. This field is a UTF-8
encoded character string whose octet length is given by the
Version Len field. This field MUST NOT include extra octets
for padding or NUL character termination. The syntax and
semantics of this version string are not specified in this
document, since they may vary across products and/or
operating systems. Posture Collectors MAY list two packages
with the same Package Version Number (and even the same
Package Name and Package Version Number) in a single
Installed Packages attribute. The meaning of doing so is not
defined here.
3.2.8. PA-TNC Error
This PA-TNC Attribute Type contains an error code and
supplemental information regarding an error pertaining to PA-
TNC.
All Posture Collectors and Posture Validators that implement any
of the IETF Standard PA Subtypes defined in this specification
MUST support sending and receiving this attribute type, at least
for those PA subtypes.
For this attribute type, the PA-TNC Attribute Vendor ID field
MUST be set to zero (0) and the PA-TNC Attribute Type field MUST
be set to 8. The value in the PA-TNC Attribute Length field
will vary, depending on the length of the Error Information
field. However, the value in the PA-TNC Attribute Length field
MUST be at least 20 (24 if the Correlation ID field is present)
because this is the length of the fixed size fields in the PA-
TNC Attribute Header and the fixed size fields in this attribute
type.
A PA-TNC error code SHOULD be sent with the same PA Message
Vendor ID and PA Subtype used by the PA-TNC message that caused
the error so that the error code is sent to the party who sent
the offending PA-TNC message. Other measures (such as setting
PB-TNC's EXCL flag and Posture Collector Identifier or Posture
Validator Identifier fields) SHOULD also be taken to attempt to
ensure that only the party who sent the offending message
receives the error.
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When a PA-TNC error code is received, the recipient MUST NOT
respond with a PA-TNC error code because this could result in an
infinite loop of errors. Instead, the recipient MAY log the
error, modify its behavior to attempt to avoid the error
(attempting to avoid loops or long strings of errors), ignore
the error, terminate the assessment, or take other action as
appropriate (as long as it is consistent with the requirements
of this specification).
Posture Verifiers MUST NOT include this attribute type in an
Attribute Request attribute. It does not make sense for a
Posture Verifier to request that a Posture Collector send a PA-
TNC Error attribute.
The following diagram illustrates the format and contents of the
Attribute Value field for this attribute type. The text after
this diagram describes the fields shown here.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | PA-TNC Error Code Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Error Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Information (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved
This field is reserved for future use. This field MUST be
set to 0 on transmission and ignored upon reception.
PA-TNC Error Code Vendor ID
This field contains the SMI Private Enterprise Number for the
organization that defined the PA-TNC Error Code that is being
used in the attribute. For IETF Standard PA-TNC Error Code
values this field MUST be set to zero (0).
PA-TNC Error Code
This field contains the PA-TNC Error Code being reported in
this attribute. Note that a particular PA-TNC Error Code
value will have completely different meanings depending on
the PA-TNC Error Code Vendor ID. Each PA-TNC Error Code
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Vendor ID defines a different space of PA-TNC Error Code
values.
When the PA-TNC Error Code Vendor ID is set to zero (0), the
PA-TNC Error Code is an IETF Standard PA-TNC Error Code. The
IANA maintains a registry for these values. The following
table lists the IETF Standard PA-TNC Error Codes defined in
this specification:
Value Description
----- -----------
0 Reserved
1 Invalid Parameter
2 Version Not Supported
3 Attribute Type Not Supported
The next few subsections of this document provide detailed
definitions of these error codes.
Error Information
This field provides additional context for the error. The
contents of this field vary based on the PA-TNC Error Code
Vendor ID and PA-TNC Error Code. Therefore, whenever a PA-TNC
Error Code is defined, the format of this field for that
error code must also be defined. The definitions of IETF
Standard PA-TNC Error Codes on the next few pages provide
good examples of such definitions.
The length of this field can be determined by the recipient
using the PA-TNC Attribute Length field by subtracting the
length of the fixed-length fields in the PA-TNC Attribute
Header and the fixed-length fields in this attribute.
3.2.8.1. Definition of Invalid Parameter Error Code
The Invalid Parameter error code is an IETF Standard PA-TNC
Error Code (value 1) that indicates that the sender of this
error code has detected an invalid value in a PA-TNC message
sent by the recipient of this error code in the current
assessment.
For this error code, the Error Information field contains the
first 8 octets of the PA-TNC message that contained the invalid
parameter and an offset indicating the position within that
message of the invalid parameter.
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The following diagram illustrates the format and contents of the
Error Information field for this error code. The text after
this diagram describes the fields shown here.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Copy of Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version
This field MUST contain an exact copy of the Version field in
the PA-TNC Message Header of the PA-TNC message that caused
this error.
Copy of Reserved
This field MUST contain an exact copy of the Reserved field
in the PA-TNC Message Header of the PA-TNC message that
caused this error.
Message Identifier
This field MUST contain an exact copy of the Message
Identifier field in the PA-TNC Message Header of the PA-TNC
message that caused this error.
Offset
This field MUST contain an octet offset from the start of the
PA-TNC Message Header of the PA-TNC message that caused this
error to the start of the value that caused this error. For
instance, if the first PA-TNC attribute in the message had an
invalid PA-TNC Attribute Length (e.g. 0), this value would be
16.
3.2.8.2. Definition of Version Not Supported Error Code
The Version Not Supported error code is an IETF Standard PA-TNC
Error Code (value 2) that indicates that the sender of this
error code does not support the PA-TNC version number included
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in the PA-TNC Message Header of a PA-TNC message sent by the
recipient of this error code in the current assessment.
For this error code, the Error Information field contains the
first 8 octets of the PA-TNC message that contained the
unsupported version as well as Max Version and Min Version
fields that indicate which PA-TNC version numbers are supported
by the sender of the error code.
The sender MUST support all PA-TNC versions between the Min
Version and the Max Version, inclusive (i.e. including the Min
Version and the Max Version). When possible, recipients of this
error code SHOULD send future messages to the Posture Collector
or Posture Validator that originated this error message with a
PA-TNC version number within the stated range.
Any party that is sending the Version Not Supported error code
SHOULD include that error code as the only PA-TNC attribute in a
PA-TNC message with version number 1. All parties that send PA-
TNC messages SHOULD be able to properly process a message that
meets this description, even if they cannot process any other
aspect of PA-TNC version 1. This ensures that a PA-TNC version
exchange can proceed properly, no matter what versions of PA-TNC
the parties implement.
The following diagram illustrates the format and contents of the
Error Information field for this error code. The text after
this diagram describes the fields shown here.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Copy of Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Version | Min Version | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version
This field MUST contain an exact copy of the Version field in
the PA-TNC Message Header of the PA-TNC message that caused
this error.
Copy of Reserved
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This field MUST contain an exact copy of the Reserved field
in the PA-TNC Message Header of the PA-TNC message that
caused this error.
Message Identifier
This field MUST contain an exact copy of the Message
Identifier field in the PA-TNC Message Header of the PA-TNC
message that caused this error.
Max Version
This field MUST contain the maximum PA-TNC version supported
by the sender of this error code.
Min Version
This field MUST contain the minimum PA-TNC version supported
by the sender of this error code.
Reserved
Reserved for future use. This field MUST be set to 0 on
transmission and ignored upon reception.
3.2.8.3. Definition of Attribute Type Not Supported Error Code
The Attribute Type Not Supported error code is an IETF Standard
PA-TNC Error Code (value 3) that indicates that the sender of
this error code does not support the PA-TNC Attribute Type
included in the Error Information field. This PA-TNC Attribute
Type was included in a PA-TNC message sent by the recipient of
this error code in the current assessment.
For this error code, the Error Information field contains the
first 8 octets of the PA-TNC message that contained the
unsupported attribute type as well as a copy of the attribute
type that caused the problem.
The following diagram illustrates the format and contents of the
Error Information field for this error code. The text after
this diagram describes the fields shown here.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | PA-TNC Attribute Vendor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PA-TNC Attribute Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version
This field MUST contain an exact copy of the Version field in
the PA-TNC Message Header of the PA-TNC message that caused
this error.
Copy of Reserved
This field MUST contain an exact copy of the Reserved field
in the PA-TNC Message Header of the PA-TNC message that
caused this error.
Message Identifier
This field MUST contain an exact copy of the Message
Identifier field in the PA-TNC Message Header of the PA-TNC
message that caused this error.
Flags
This field MUST contain an exact copy of the Flags field in
the PA-TNC Attribute Header of the PA-TNC attribute that
caused this error.
PA-TNC Attribute Vendor ID
This field MUST contain an exact copy of the PA-TNC Attribute
Vendor ID field in the PA-TNC Attribute Header of the PA-TNC
attribute that caused this error.
PA-TNC Attribute Type
This field MUST contain an exact copy of the PA-TNC Attribute
Type field in the PA-TNC Attribute Header of the PA-TNC
attribute that caused this error.
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3.3. Vendor-Defined Attributes
This section discusses the use of vendor-defined attributes
within PA-TNC. The PA-TNC protocol was designed to allow for
vendor-defined attributes to be used as a replacement where a
standard attribute could be used. In some cases even the
standard attributes allow for vendor-defined information to be
included. It is envisioned that over time as particular vendor-
defined attributes become popular, an equivalent standard
attribute could be added allowing for broader interoperability.
This specification does not define vendor-defined attributes,
but rather highlights how such attributes can be used with PA-
TNC without the potential for name space collisions or
misinterpretations. In order to avoid collisions, PA-TNC uses
the well-established SMI Private Enterprise Numbers as Vendor
IDs to define separate name spaces for important fields within a
PA-TNC message. For example, to ensure the uniqueness of
attribute types while providing for vendor extensions, vendor-
defined attribute types include the vendor's unique Vendor ID,
to indicate the intended name space for the attribute type,
followed by the attribute type. IETF Standard PA-TNC Attribute
Types use a Vendor ID of zero (0).
SMI Private Enterprise Numbers are used to provide a separate
identifier space for each vendor. The IANA provides a registry
for SMI Private Enterprise Numbers. Any organization (including
non-profit organizations, governmental bodies, etc.) can obtain
one of these numbers at no charge and thousands of organizations
have done so. Within this document, SMI Private Enterprise
Numbers are known as "vendor IDs".
4. Evaluation Against NEA Requirements
This section evaluates the PA-TNC protocol against the
requirements defined in the NEA Requirements document. Each
subsection considers a separate requirement from the NEA
Requirements document. Only common requirements (C-1 through C-
10) and PA requirements (PA-1 through PA-6) are considered,
since these are the only ones that apply to PA.
4.1. Evaluation Against Requirement C-1
Requirement C-1 says:
C-1 NEA protocols MUST support multiple round trips between
the NEA Client and NEA Server in a single assessment.
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PA-TNC meets this requirement. It allows an unlimited number of
round trips between the NEA Client and NEA Server.
4.2. Evaluation Against Requirement C-2
Requirement C-2 says:
C-2 NEA protocols SHOULD provide a way for both the NEA Client
and the NEA Server to initiate a posture assessment or
reassessment as needed.
PA-TNC meets this requirement. PA-TNC is designed to work
whether the NEA Client or the NEA Server initiates a posture
assessment or reassessment.
4.3. Evaluation Against Requirement C-3
Requirement C-3 says:
C-3 NEA protocols including security capabilities MUST be
capable of protecting against active and passive attacks
by intermediaries and endpoints including prevention from
replay based attacks.
Security for PA-TNC can be provided through PT security or
through the use of PA-TNC security, which is defined in a
separate specification: PA-TNC Security [8]. Therefore, this
base specification for PA-TNC does not include any security
capabilities. Since this requirement only applies to NEA
protocols that include security capabilities, this base
specification for PA-TNC meets this requirement.
4.4. Evaluation Against Requirement C-4
Requirement C-4 says:
C-4 The PA and PB protocols MUST be capable of operating over
any PT protocol. For example, the PB protocol must
provide a transport independent interface allowing the PA
protocol to operate without change across a variety of
network protocol environments (e.g. EAP/802.1X, PANA, TLS
and IKE/IPsec).
PA-TNC meets this requirement. PA-TNC can operate over any PT
protocol that meets the requirements for PT stated in the NEA
Requirements document. PA-TNC does not have any dependencies on
specific details of the underlying PT protocol.
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4.5. Evaluation Against Requirement C-5
Requirement C-5 says:
C-5 The selection process for NEA protocols MUST evaluate and
prefer the reuse of existing open standards that meet the
requirements before defining new ones. The goal of NEA is
not to create additional alternative protocols where
acceptable solutions already exist.
Based on this requirement, PA-TNC should receive a strong
preference. PA-TNC is equivalent with IF-M 1.0, an open TCG
specification. Other specifications from TCG and other groups
are also under development based on the IF-M 1.0 specification.
Selecting PA-TNC as the basis for the PA protocol will ensure
compatibility with IF-M 1.0, with these other specifications,
and with their implementations.
4.6. Evaluation Against Requirement C-6
Requirement C-6 says:
C-6 NEA protocols MUST be highly scalable; the protocols MUST
support many Posture Collectors on a large number of NEA
Clients to be assessed by numerous Posture Validators
residing on multiple NEA Servers.
PA-TNC meets this requirement. PA-TNC supports an unlimited
number of Posture Collectors, Posture Validators, NEA Clients,
and NEA Servers. It also is quite scalable in many other
aspects as well. A PA-TNC message can contain up to 2^32-1
octets and about 2^28 PA-TNC attributes. Each organization with
an SMI Private Enterprise Number is entitled to define up to
2^32 vendor-specific PA-TNC Attribute Types, 2^16 vendor-
specific PA-TNC Product IDs, and 2^32 vendor-specific PA-TNC
Error Codes. Each attribute can contain almost 2^32 octets. It
is generally not advisable or necessary to send this much data
in a NEA assessment, but still PA-TNC is highly scalable and
meets requirement C-6 easily.
4.7. Evaluation Against Requirement C-7
Requirement C-7 says:
C-7 The protocols MUST support efficient transport of a large
number of attribute messages between the NEA Client and
the NEA Server.
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PA-TNC meets this requirement. Each PA-TNC message can contain
about 2^28 PA-TNC attributes. PA-TNC supports up to 2^32 round
trips in a session so the maximum number of attribute messages
that can be sent in a single session is actually about 2^50.
However, it is generally inadvisable and unnecessary to send a
large number of messages in a NEA assessment. As for
efficiency, PA-TNC adds only 12 octets of overhead per attribute
and 8 octets per message (which is negligible on a per-attribute
basis).
4.8. Evaluation Against Requirement C-8
Requirement C-8 says:
C-8 NEA protocols MUST operate efficiently over low bandwidth
or high latency links.
PA-TNC meets this requirement. A typical PA-TNC exchange will
involve one or two round trips with less than 500 octets of PA-
TNC messages. Of course, use of PA-TNC security or vendor-
specific PA-TNC attribute types could expand the assessment.
However, PA-TNC itself imposes an overhead of only 8 octets per
PA-TNC message and 12 octets per attribute.
4.9. Evaluation Against Requirement C-9
Requirement C-9 says:
C-9 For any strings intended for display to a user, the
protocols MUST support adapting these strings to the
user's language preferences.
PA-TNC meets this requirement. The fields defined here do not
include any strings intended for display to a user. They are
intended for logging and programmatic comparisons.
If any vendor-specific PA-TNC attribute types or future IETF
Standard PA-TNC Attribute Types include strings that are
intended for display to a user, they can be adapted to the
user's language preferences using the PB-TNC protocol's ability
to exchange information about those preferences in a standard
manner. The Posture Broker Server will need to expose the
user's preferences to the Posture Validators through whatever
API or protocol is used to connect those components. However,
that is all out of scope for this specification.
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4.10. Evaluation Against Requirement C-10
Requirement C-10 says:
C-10 NEA protocols MUST support encoding of strings in UTF-8
format.
PA-TNC meets this requirement. All strings in the PA-TNC
protocol are encoded in UTF-8 format. This allows the protocol
to support a wide range of languages efficiently.
4.11. Evaluation Against Requirement PA-1
Requirement PA-1 says:
PA-1 The PA protocol MUST support communication of an
extensible set of NEA standards defined attributes. These
attributes will be uniquely identifiable from non-standard
attributes.
PA-TNC meets this requirement. Each attribute is identified
with a PA-TNC Attribute Vendor ID and a PA-TNC Attribute Type.
IETF Standard PA-TNC Attribute Types use a vendor ID of zero
(0), in contrast with vendor-specific PA-TNC Attribute Types,
which will use the vendor's SMI Private Enterprise Number as the
vendor ID. The IANA will maintain a registry of IETF Standard
PA-TNC Attribute Types with new values added by IETF Consensus,
as described in the IANA Considerations section of this
specification. Thus, the set of standard attribute types is
extensible, but all standard attribute types are uniquely
identifiable.
4.12. Evaluation Against Requirement PA-2
Requirement PA-2 says:
PA-2 The PA protocol MUST support communication of an
extensible set of vendor-specific attributes. These
attributes will be segmented into uniquely identifiable
vendor specific name spaces.
PA-TNC meets this requirement. Each attribute is identified
with a PA-TNC Attribute Vendor ID and a PA-TNC Attribute Type.
Vendor-defined PA-TNC Attribute Types use the vendor's SMI
Private Enterprise Number as the PA-TNC Attribute Vendor ID.
Each vendor can define up to 2^32 PA-TNC Attribute Types, using
its own internal processes to manage its set of attribute types.
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The IANA is not involved, other than the initial assignment of
the vendor's SMI Private Enterprise Number. Thus, the set of
vendor-specific attributes is segmented into uniquely
identifiable vendor-specific name spaces.
4.13. Evaluation Against Requirement PA-3
Requirement PA-3 says:
PA-3 The PA protocol MUST enable a Posture Validator to make
one or more requests for attributes from a Posture
Collector within a single assessment. This enables the
Posture Validator to reassess the posture of a particular
endpoint feature or to request additional posture
including from other parts of the endpoint.
PA-TNC meets this requirement. The Attribute Request attribute
type is an IETF Standard PA-TNC Attribute Type that permits a
Posture Validator to send to one or more Posture Collectors a
request for one or more attributes. This attribute may be sent
at any point in the posture assessment process and may in fact
be sent more than once if the Posture Validator needs to first
determine the type of operating system and then request certain
attributes specific to that operating system, for example.
4.14. Evaluation Against Requirement PA-4
Requirement PA-4 says:
PA-4 The PA protocol MUST be capable of returning attributes
from a Posture Validator to a Posture Collector. For
example, this might enable the Posture Collector to learn
the specific reason for a failed assessment and to aid in
remediation and notification of the system owner.
PA-TNC meets this requirement. A Posture Validator can easily
send attributes to one or more Posture Collectors.
4.15. Evaluation Against Requirement PA-5
Requirement PA-5 says:
PA-5 The PA protocol SHOULD provide authentication, integrity,
and confidentiality of attributes communicated between a
Posture Collector and Posture Validator. This enables
end-to-end security across a NEA deployment that might
involve traversal of several systems or trust boundaries.
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PA-TNC meets this requirement when a PA-TNC Security mechanism
is used, such as PA-TNC Security with CMS. The specifications
for those mechanisms should be consulted for a complete analysis
of their security properties.
PA-TNC Security is an optional addition to PA-TNC because
different products and deployments may require different
security mechanisms. For example, one product might integrate
Posture Validators, the Posture Broker Server, and the Posture
Transport Server into a single entity. In that case, PA-TNC
security may not be needed. PT security may be enough. Another
deployment may employ remote Posture Validators in the same
trust domain as the Posture Broker Server. In that case, a TLS
session between the Posture Broker Server and the Posture
Validators may suffice. A third deployment may include a Posture
Broker Server that is not trusted to see PA-TNC messages, at
least for some Posture Validators. In that case, PA-TNC security
may be desirable. Even there, some deployments may wish to use
PKI (Public Key Infrastructure) for security, while others may
wish to use Kerberos or another mechanism.
4.16. Evaluation Against Requirement PA-6
Requirement PA-6 says:
PA-6 The PA protocol MUST be capable of carrying attributes
that contain non-binary and binary data including
encrypted content.
PA-TNC meets this requirement. PA-TNC attributes can contain
non-binary and binary data including encrypted content. For
examples, see the attribute type definitions contained in this
specification and in the PA-TNC Security with CMS specification.
5. Security Considerations
This section discusses the major types of potential security
threats relevant to the PA-TNC message protocol and summarizes
the expected security protections that should be offered by PA-
TNC security protocols. PA-TNC security protocols are described
in separate specifications which layer upon the base PA-TNC
protocol described in this specification. It is envisioned that
additional attribute types will be defined to facilitate the
exchange of security capabilities, keys, and security protected
attributes. Ultimately, the NEA deployer decides which security
protection is most appropriate for a particular deployment
environment. The security protections discussed in this section
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highlight the need for PA-TNC security protocol implementations
to be capable of offering the feature.
5.1. Trust Relationships
In order to understand where security countermeasures are
necessary, this section starts with a discussion of where the
TNC architecture envisions some trust relationships between the
processing elements of the PA-TNC protocol. Some deployments
may wish to reduce the amount of assumed trust by using a PA-TNC
security protocol to protect the PA-TNC messages. The following
sub-sections discuss the trust properties associated with each
portion of the NEA reference model directly involved with the
processing of the PA-TNC protocol.
5.1.1. Posture Collector
The Posture Collectors are trusted by Posture Validators to:
o Collect valid information about the component type associated
with the Posture Collector
o Report upon collected information consistent with local
security and privacy policies
o Accurately report information associated with the type of
component for the PA-TNC message
o Not act maliciously to the Posture Broker Server and Posture
Validators, including attacks such as Denial Of Service
5.1.2. Posture Validator
The Posture Validators are trusted by Posture Collectors to:
o Only request information necessary to assess the security
state of the endpoint
o Make assessment decisions based on deployer defined policies
o Discard collected information consistent with data retention
and privacy policies
o Not act maliciously to the Posture Broker Server and Posture
Collectors, including attacks such as Denial Of Service
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5.1.3. Posture Broker Client, Posture Broker Server, and PB-TNC
The Posture Broker Client and Posture Broker Server are trusted
by the Posture Collector and Posture Validator to:
o Provide a reliable transport for PA-TNC messages
o Deliver messages for a particular PA Subtype only to those
Posture Collectors and Posture Validators that have
registered for them
o Not disclose any provided attributes to unauthorized parties
o Not act maliciously to drop messages, duplicate messages, or
flood the Posture Collectors and Posture Validators with
unnecessary messages
o Not observe, fabricate, or alter the contents of a PA-TNC
message (this trust can be minimized with a PA-TNC security
protocol)
o Properly place Posture Collector and Posture Validator
identifiers into the PB-TNC protocol, deliver those
identifiers to Posture Collectors and Posture Validators as
needed, and manage exclusive delivery to a particular Posture
Collector or Posture Validator
o Properly expose authentication information from PT security
so that Posture Collectors and Posture Validators can use
this to make policy decisions
5.2. Security Threats
Beyond the trusted relationships assumed in section 5.1, the PA-
TNC protocol faces a number of potential security attacks that
could require targeted security countermeasures. PA-TNC
security protocol specifications MUST state if and how the
security protocol will safeguard against these types of attack.
Generally the PA-TNC protocol, without the presence of security
countermeasures, relies upon the underlying PT protocol to
protect the messages from attack when traveling over the
network. Once the message resides on the Posture Broker Client
or Posture Broker Server, it is trusted to be properly and
safely delivered to the appropriate Posture Collectors and
Posture Validators. However, in some deployments the PA-TNC
messages need to travel over network hops that are not protected
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by PT or require more assurance that only the appropriate
Posture Collector or Posture Validator has received the message.
In these cases, end to end PA-TNC message protection might be
required. The following sub-sections focus on the potential
threats where end to end protection might be desired and thus
when the use of the PA-TNC security protocol becomes beneficial.
5.2.1. Attribute Theft
When PA-TNC messages are sent over unprotected network links or
spanning local software stacks that are not trusted, the
contents of the PA-TNC messages may be subject to information
theft by an intermediary party. This theft could result in
information being recorded for future use or analysis by the
adversary. Attributes observed by eavesdroppers could contain
information that exposes potential weaknesses in the security of
the endpoint, or system fingerprinting information easing the
ability of the attacker to employ attacks more likely to be
successful against the endpoint. The eavesdropper might also
learn information about the endpoint or network policies that
either singularly or collectively is considered sensitive
information (e.g. certain endpoints are lacking patches, or
particular sub-networks have more lenient policies). PA-TNC
attributes are not intended to carry privacy-sensitive
information, but should some exist in a message, the adversary
could come into possession of the information which could be
used for other financial gain.
5.2.2. Message Fabrication
Attackers on the network or present within the NEA system could
introduce fabricated PA-TNC messages intending to trick or
create a denial of service against aspects of an assessment.
This could occur if an active attacker could launch a man-in-
the-middle (MiTM) attack by proxying the PA-TNC messages and was
able to replace undesired messages with ones easing future
attack upon the endpoint. Consider a scenario where PT security
protection is not used, and the Posture Broker Server proxies
all assessment traffic to a remote Posture Broker Server. The
proxy could eavesdrop and replace assessment results attributes,
tricking the endpoint into thinking it has passed an assessment,
when in fact it has not and requires remediation. Because the
Posture Collector has no way to verify that attributes were
actually created by an authentic Posture Validator, it is unable
to detect the falsified attribute or message.
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5.2.3. Attribute Modification
This attack could allow an active attacker capable of
intercepting a message to modify a PA-TNC message attribute to a
desired value to ease the compromise of an endpoint. Without
the ability for message recipients to detect whether a received
message contains the same content as what was originally sent,
active attackers can stealthily modify the attribute exchange.
For example, an attacker might wish to change the contents of
the firewall component's version string attribute to disguise
the fact that the firewall is running an old, vulnerable
version. The attacker would change the version string sent by
the firewall Posture Collector to the current version number, so
the Posture Validator's assessment passes while leaving the
endpoint vulnerable to attack. Similarly, an attacker could
achieve widespread denial of service by altering large numbers
of assessments' version string attributes to an old value so
they repeatedly fail assessments even after a successful
remediation. Upon receiving the lower value, the Posture
Validator would continue to believe that the endpoint is running
old, potentially vulnerable versions of the firewall that does
not meet network compliance policy, so therefore the endpoint
would not be allowed to join the network.
5.2.4. Attribute Replay
Another potential attack against an unprotected PA-TNC message
attribute exchange is to exploit the lack of a strong binding
between the attributes sent during an assessment to the specific
endpoint. Without a strong binding of the endpoint to the
measurement information, an attacker could record the attributes
sent during an assessment of a compliant endpoint and later
replay those attributes so that a non-compliant endpoint can now
gain access to the network or protected resource. This attack
could be employed by a network MiTM that is able to eavesdrop
and proxy message exchanges, or by using local rogue agents on
the endpoints. Assessments lacking some form of freshness
exchange could be subject to replay of prior assessment data,
even if it no longer reflects the current state of the endpoint.
5.2.5. Attribute Insertion
Similar to the attribute modification attacks, an adversary
wishing to include one or more attributes or PA-TNC messages
inside a valid assessment may be able to insert the attributes
or messages without detection is possible by the recipient.
Even if authentication of the parties is present during a PA-TNC
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exchange, if no per-message and per-session integrity protection
is present, an attacker can add information to the assessment,
possibly causing incorrect assessment results. For example, an
attacker could add attributes to the front of a PA-TNC message
to cause an assessment to succeed even for a non-compliant
endpoint, particularly if it knew that the recipient ignored
repeated attributes within a message. Similarly, if a Posture
Collector or Posture Validator always generated an error if it
saw unexpected attributes, the attacker could cause failures and
denial of service by adding attributes or messages to an
exchange.
5.2.6. Denial of Service
A variety of types of denial of service attacks are possible
against the PA-TNC message exchange if left unprotected to
untrusted parties along the communication path between the
Posture Collector and Posture Validator. Normally, the PT
exchange is bi-directionally authenticated which helps to
prevent a MiTM on the network from becoming an active proxy, but
transparent message routing gateways may still exist on the
communication path and can modify the integrity of the message
exchange unless adequate integrity protection is provided. If
the MiTM or other entities on the network can send messages to
the Posture Broker Client or Posture Broker Server that appear
to be part of an assessment, these messages could confuse the
Posture Collector and Posture Validator or cause them to perform
unnecessary work or take incorrect action. Several example
denial of service situations are described in section 5.2.3 and
5.2.5. Many potential denial of service examples exist,
including flooding messages to Posture Collector or Posture
Validator, sending very large messages containing many
attributes, and repeatedly asking for resource intensive
operations.
6. Privacy Considerations
The PA-TNC protocol is designed to allow for controlled
disclosure of security relevant information about an endpoint,
specifically for the purpose of enabling an assessment of the
endpoint's compliance with network policy. The purpose of this
protocol is to provide visibility into the state of the
protective mechanisms on the endpoint, in order for the Posture
Validators and Posture Broker Server to determine whether the
endpoint is up to date and thus has the best chance of being
resilient in the face of malware threats. One risk associated
with providing visibility into the contents of an endpoint is
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the increased chance for exposure of privacy sensitive
information without the consent of the user.
While this protocol does provide the Posture Validator the
ability to request specific information about the endpoint, the
protocol is not open ended--bounding the Posture Validator to
only query specific information (attributes) about specific
security features (component types) of the endpoint. Each PA-
TNC message is explicitly about a single component from the list
of components in section 2.4. These components include a list
of security-related aspects of the endpoint that affect the
ability of the endpoint to resist attacks and thus are of
interest during an assessment. Discretionary components used by
the user to create or view content are not on the list, as they
are more likely to have access to privacy sensitive information.
Similarly, PA-TNC messages contain a set of attributes which
describe the particular component. Each attribute contains
generic information (e.g. product information or versions) about
the component, so it is unlikely to include any user specific or
identifying information. This combination of limited set of
security related components with non-user specific attributes
greatly reduces the risk of exposure of privacy sensitive
information. Vendors that choose to define additional component
types and/or attributes within their name space are encouraged
to provide similar constraints.
Even with the bounding of standard attribute information to
specific components, it is possible that individuals might wish
to share less information with different networks they wish to
access. For example, a user may wish to share more information
when connecting or being reassessed by the user's employer
network than what would be made available to the local coffee
shop wireless network. While these situations do not impact the
protocol itself, they do suggest that Posture Collector
implementations should consider supporting a privacy filter
allowing the user and/or system owner to restrict access to
certain attributes based upon the target network. The
underlying PT protocol authenticates the network's Posture
Broker Server at the start of an assessment, so identity can be
made available to the Posture Collector and per-network privacy
filtering is possible. Network owners should make available a
list of the attributes they require to perform an assessment and
any privacy policy they enforce when handling the data. Users
wishing to use a more restricted privacy filter on the endpoint
may risk not being able to pass an assessment and thus not gain
access to the requested network or resource.
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7. IANA Considerations
Two new IANA registries are defined by this specification: IETF
Standard PA-TNC Attribute Types and IETF Standard PA-TNC Error
Codes. This section explains how these registries work. Also,
this specification defines nine new IETF Standard PA Subtypes.
These assignments will be added to the registry for IETF
Standard PA Subtypes when this document is approved by the IESG
as an RFC.
Section 7.1 defines the new IETF Standard PA Subtypes. Sections
7.2 and 7.3 provide guidance to the IANA in creating and
managing the two new IANA registries defined by this
specification.
7.1. New IETF Standard PA Subtypes
Section 2.4 of this specification defines several new IETF
Standard PA Subtypes. Here is a list of these assignments:
Number Name
------ ----
0 Testing
1 Operating System
2 Anti-Virus
3 Anti-Spyware
4 Anti-Malware
5 Firewall
6 IDPS
7 VPN
Once this document becomes an RFC, these IETF Standard PA
Subtypes should be added to the registry for IETF Standard PA
Subtypes defined in the PB-TNC specification. The RFC number
assigned to this document should be associated with these
assignments.
7.2. Registry for IETF Standard PA-TNC Attribute Types
The name for this registry is "IETF Standard PA-TNC Attribute
Types". Each entry in this registry should include a human-
readable name, a decimal integer value between 0 and 2^32-1, and
a reference to an RFC where the contents of this attribute type
are defined. This RFC must define the meaning of this PA-TNC
attribute type and the format and semantics of the PA-TNC
Attribute Value field for PA-TNC attributes that include the
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designated numeric value in the PA-TNC Attribute Type field and
the value 0 in the PA-TNC Attribute Vendor ID field.
Entries to this registry may only be added by IETF Consensus, as
defined in RFC 2434 [3]. That is, they can only be added in an
RFC approved by the IESG.
The following entries for this registry are defined in this
document. Once this document becomes an RFC, they should become
the initial entries in the registry for IETF Standard PA-TNC
Attribute Types.
Integer Value Name Defining RFC
------------- ---- ------------
0 Testing RFC # Assigned to this I-D
1 Attribute Request RFC # Assigned to this I-D
2 Product Information RFC # Assigned to this I-D
3 Numeric Version RFC # Assigned to this I-D
4 String Version RFC # Assigned to this I-D
5 Operational Status RFC # Assigned to this I-D
6 Port Filter RFC # Assigned to this I-D
7 Installed Packages RFC # Assigned to this I-D
8 PA-TNC Error RFC # Assigned to this I-D
7.3. Registry for IETF Standard PA-TNC Error Codes
The name for this registry is "IETF Standard PA-TNC Error
Codes". Each entry in this registry should include a human-
readable name, a decimal integer value between 0 and 2^32-1, and
a reference to an RFC where this error code is defined. This
RFC must define the meaning of this error code and the format
and semantics of the Error Information field for PA-TNC
attributes that have a PA-TNC Vendor ID of 0, a PA-TNC Attribute
Type of PA-TNC Error, the designated numeric value in the PA-TNC
Error Code field, and the value 0 in the PA-TNC Error Code
Vendor ID field.
Entries to this registry may only be added by IETF Consensus, as
defined in RFC 2434. That is, they can only be added in an RFC
approved by the IESG.
The following entries for this registry are defined in this
document. Once this document becomes an RFC, they should become
the initial entries in the registry for IETF Standard PA-TNC
Error Codes.
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Integer Value Name Defining RFC
------------- ---- ------------
1 Invalid Parameter RFC # Assigned to this I-D
2 Version Not Supported RFC # Assigned to this I-D
3 Attribute Type Not Supported RFC # Assigned to this I-D
8. Acknowledgments
The authors of this draft would like to acknowledge the
following people who have contributed to or provided substantial
input on the preparation of this document or predecessors to it:
Stuart Bailey, Roger Chickering, Lauren Giroux, Charles
Goldberg, Steve Hanna, Ryan Hurst, Meenakshi Kaushik, Greg
Kazmierczak, Scott Kelly, PJ Kirner, Houcheng Lee, Lisa
Lorenzin, Mahalingam Mani, Sung Lee, Ravi Sahita, Mauricio
Sanchez, Brad Upson, and Han Yin.
This document was prepared using 2-Word-v2.0.template.dot.
9. References
9.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] F. Yergeau, "UTF-8, a transformation format of ISO 10646",
RFC 3629, November 2003.
[3] Alvestrand, H. and T. Narten, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2434, October
1998.
[4] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, July 2002.
[5] Sahita, R., Hanna, S., and R. Hurst, "PB-TNC: A Posture
Broker Protocol (PB) Compatible with TNC", draft-ietf-nea-
pb-tnc-00.txt, Work In Progress, April 2008.
9.2. Informative References
[6] Trusted Computing Group, "IF-M: TLV Binding", February
2008.
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[7] Sangster, P., Khosravi, H., Mani, M., Narayan, K., and J.
Tardo, "Network Endpoint Assessment (NEA): Overview and
Requirements", draft-ietf-nea-requirements-06.txt, Work In
Progress, February 2008.
[8] Sangster, P., "PA-TNC Security: A Posture Attribute (PA)
Security Protocol Compatible with TNC", draft-sangster-
nea-pa-tnc-security-00.txt, Work In Progress, February
2008.
Author's Address
Paul Sangster
Symantec Corporation
6825 Citrine Drive
Carlsbad, CA 92009 USA
Phone: +1.760.438.5656
Email: Paul_Sangster@symantec.com
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