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draft-ietf-sacm-epcp
SACM D. Haynes
Internet-Draft The MITRE Corporation
Intended status: Standards Track J. Fitzgerald-McKay
Expires: January 3, 2019 Department of Defense
L. Lorenzin
Pulse Secure
July 2, 2018
Endpoint Posture Collection Profile
draft-ietf-sacm-ecp-02
Abstract
This document specifies the Endpoint Posture Collection Profile,
which describes the best practices for the application of IETF and
TNC protocols and interfaces to support the on-going collection,
communication, and assessment of endpoint posture, as well as the
controlled exposure of endpoint posture to other tools. This
document is an extension of the Trusted Computing Group's Endpoint
Compliance Profile Version 1.0 specification.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 3, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Preventative Posture Assessments . . . . . . . . . . . . 4
1.2. All Network-Connected Endpoints are Endpoints . . . . . . 5
1.3. All Endpoints on the Network Must be Uniquely Identified 5
1.4. Standardized Data Models . . . . . . . . . . . . . . . . 5
1.5. Posture Information Must Be Stored . . . . . . . . . . . 6
1.6. Posture Information Can Be Shared . . . . . . . . . . . . 6
1.7. Enterprise Asset Posture Information Belongs to the
Enterprise . . . . . . . . . . . . . . . . . . . . . . . 6
1.8. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 7
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Endpoint Posture Collection Profile . . . . . . . . . . . . . 7
3.1. Posture Assessments . . . . . . . . . . . . . . . . . . . 7
3.2. Data Storage . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Data Sharing . . . . . . . . . . . . . . . . . . . . . . 8
4. EPCP Components . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Endpoint . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1.1. Posture Collection Engine . . . . . . . . . . . . . . 9
4.2. Posture Manager . . . . . . . . . . . . . . . . . . . . . 9
4.2.1. Posture Collection Manager . . . . . . . . . . . . . 10
4.3. Repository . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Evaluator . . . . . . . . . . . . . . . . . . . . . . . . 10
4.5. Orchestrator . . . . . . . . . . . . . . . . . . . . . . 11
5. EPCP Transactions . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Provisioning . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Discovery and Validation . . . . . . . . . . . . . . . . 11
5.3. Event Driven Collection . . . . . . . . . . . . . . . . . 11
5.4. Querying . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5. Data Storage . . . . . . . . . . . . . . . . . . . . . . 12
5.6. Data Sharing . . . . . . . . . . . . . . . . . . . . . . 12
6. EPCP Implementations . . . . . . . . . . . . . . . . . . . . 13
6.1. IETF NEA EPCP Implementation for Traditional Endpoints . 13
6.1.1. Endpoint Pre-Provisioning . . . . . . . . . . . . . . 14
6.1.2. Endpoint . . . . . . . . . . . . . . . . . . . . . . 15
6.1.2.1. Posture Collector . . . . . . . . . . . . . . . . 15
6.1.2.2. Posture Broker Client . . . . . . . . . . . . . . 16
6.1.2.3. Posture Transport Client . . . . . . . . . . . . 16
6.1.3. Posture Manager . . . . . . . . . . . . . . . . . . . 16
6.1.3.1. Posture Validator . . . . . . . . . . . . . . . . 16
6.1.3.2. Posture Broker Server . . . . . . . . . . . . . . 16
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6.1.3.3. Posture Transport Server . . . . . . . . . . . . 16
6.1.4. Repository . . . . . . . . . . . . . . . . . . . . . 17
6.1.5. IETF SACM SWAM Extension to the IETF NEA EPCP
Implementation . . . . . . . . . . . . . . . . . . . 17
6.1.5.1. Endpoint Pre-Provisioning . . . . . . . . . . . . 17
6.1.5.2. SWID Tags . . . . . . . . . . . . . . . . . . . . 17
6.1.5.3. SWID Posture Collectors and Posture Validators . 17
6.1.5.4. Repository . . . . . . . . . . . . . . . . . . . 19
6.2. IETF NETMOD EPCP Implementation for Network Device
Endpoints . . . . . . . . . . . . . . . . . . . . . . . . 19
6.2.1. Endpoint Pre-Provisioning . . . . . . . . . . . . . . 20
6.2.2. Posture Manager Pre-Provisioning . . . . . . . . . . 20
6.2.3. Endpoint . . . . . . . . . . . . . . . . . . . . . . 20
6.2.3.1. Datastore . . . . . . . . . . . . . . . . . . . . 20
6.2.4. Posture Manager . . . . . . . . . . . . . . . . . . . 20
6.2.5. Repository . . . . . . . . . . . . . . . . . . . . . 21
6.3. Administrative Interface and API . . . . . . . . . . . . 21
7. EPCP Use Cases . . . . . . . . . . . . . . . . . . . . . . . 22
7.1. Hardware Asset Management . . . . . . . . . . . . . . . . 22
7.2. Software Asset Management . . . . . . . . . . . . . . . . 22
7.3. Vulnerability Searches . . . . . . . . . . . . . . . . . 22
7.4. Threat Detection and Analysis . . . . . . . . . . . . . . 23
8. Non-supported Use Cases . . . . . . . . . . . . . . . . . . . 23
9. Endpoint Posture Collection Profile Examples . . . . . . . . 23
9.1. Continuous Posture Assessment of an Endpoint . . . . . . 23
9.1.1. Change on Endpoint Triggers Posture Assessment . . . 24
9.2. Administrator Searches for Vulnerable Endpoints . . . . . 27
10. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 28
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 29
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
13. Security Considerations . . . . . . . . . . . . . . . . . . . 31
13.1. Security Benefits of Endpoint Posture Collection Profile 31
13.2. Threat Model . . . . . . . . . . . . . . . . . . . . . . 33
13.2.1. Endpoint Attacks . . . . . . . . . . . . . . . . . . 33
13.2.2. Network Attacks . . . . . . . . . . . . . . . . . . 34
13.2.3. Posture Manager Attacks . . . . . . . . . . . . . . 34
13.2.4. Repository Attacks . . . . . . . . . . . . . . . . . 34
13.3. Countermeasures . . . . . . . . . . . . . . . . . . . . 35
13.3.1. Countermeasures for Endpoint Attacks . . . . . . . . 35
13.3.2. Countermeasures for Network Attacks . . . . . . . . 36
13.3.3. Countermeasures for Posture Manager Attacks . . . . 36
13.3.4. Countermeasures for Repository Attacks . . . . . . . 37
14. Privacy Considerations . . . . . . . . . . . . . . . . . . . 37
15. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 38
15.1. -01 to -02 . . . . . . . . . . . . . . . . . . . . . . . 38
15.2. -00 to -01 . . . . . . . . . . . . . . . . . . . . . . . 38
15.3. -01 to -02 . . . . . . . . . . . . . . . . . . . . . . . 38
15.4. -02 to -00 . . . . . . . . . . . . . . . . . . . . . . . 38
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15.5. -00 to -01 . . . . . . . . . . . . . . . . . . . . . . . 38
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 39
16.1. Informative References . . . . . . . . . . . . . . . . . 39
16.2. Normative References . . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction
The Endpoint Posture Collection Profile (EPCP) builds on prior work
from the IETF NEA WG, the IETF NETMOD WG, and the Trusted Computing
Group [TNC] Trusted Network Communications (TNC) WG to describe the
best practices for the collection, communication, and sharing of
posture information from network-connected endpoints. The first
generation of this document focuses on reducing the security exposure
of a network by enabling event-driven posture collection,
standardized querying of additional endpoint data as needed, and the
communication of that data to a posture manager.
Future revisions of this document may include support for the
collection of endpoint posture from other endpoint types and a
standardized interface for repositories among other capabilities.
Additional information about this future work can be found in
Section 10 of this document.
1.1. Preventative Posture Assessments
The value of continuous endpoint posture assessment is well
established. Security experts have identified asset management and
vulnerability remediation as a critical step for preventing
intrusions. Application whitelisting, patching applications and
operating systems, and using the latest versions of applications top
the Defense Signals Directorate's "Top 4 Mitigations to Protect Your
ICT System". [DSD] "Inventory of Authorized and Unauthorized
Endpoints", "Inventory of Authorized and Unauthorized Software", and
"Continuous Vulnerability Assessment and Remediation" are Controls 1,
2, and 4, respectively, of the CIS Controls. [CIS] While there are
commercially available solutions that attempt to address these
security controls, these solutions do not run on all types of
endpoints; consistently interoperate with other tools that could make
use of the data collected; collect posture information from all types
of endpoints in a consistent, standardized schema; or require vetted,
standardized protocols that have been evaluated by the international
community for cryptographic soundness.
As is true of most solutions offered today, the solution found in the
EPCP does not attempt to solve the lying endpoint problem, or detect
infected endpoints; rather, it focuses on ensuring that healthy
endpoints remain healthy by keeping software up-to-date and patched.
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1.2. All Network-Connected Endpoints are Endpoints
As defined by [I-D.ietf-sacm-terminology], an endpoint is any
physical or virtual computing endpoint that can be connected to a
network. Posture assessment against policy is equally, if not more,
important for continuously connected endpoints, such as enterprise
workstations and infrastructure endpoints, as it is for sporadically
connected endpoints. Continuously connected endpoints are just as
likely to fall out of compliance with policy, and a standardized
posture assessment method is necessary to ensure they can be properly
handled.
1.3. All Endpoints on the Network Must be Uniquely Identified
Many administrators struggle to identify what endpoints are connected
to the network at any given time. By requiring a standardized method
of endpoint identity, the EPCP will enable administrators to answer
the basic question, "What is on my network?" In
[I-D.ietf-sacm-terminology], SACM defines this set of endpoints on
the network as the SACM domain. Unique endpoint identification also
enables the comparison of current and past endpoint posture
assessments, by allowing administrators to correlate assessments from
the same endpoint. This makes it easier to flag suspicious changes
in endpoint posture for manual or automatic review, and helps to
swiftly identify malicious changes to endpoint applications.
1.4. Standardized Data Models
Meeting EPCP best practices requires the use of standardized data
models for the exchange of posture information. This helps to ensure
that the posture information sent from endpoints to the repository
can be easily stored, due to their known format, and shared with
authorized endpoints and users.
Posture information must be sent over standardized protocols to
ensure the confidentiality and authenticity of this data while in
transit. Implementations of the EPCP include [RFC6876] and [RFC6241]
for communication between the target endpoint and the posture
manager. These protocols allow networks that implement this solution
to collect large amounts of posture information from an endpoint to
make decisions about that endpoint's compliance with some policy.
The EPCP offers a solution for all endpoints already connected to the
network. Periodic assessments and automated reporting of changes to
endpoint posture allow for instantaneous identification of connected
endpoints that are no longer compliant to some policy.
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1.5. Posture Information Must Be Stored
Posture information must be stored by the repository and must be
exposed to an interface at the posture manager. Standard data models
enable standard queries from an interface exposed to an administrator
at the posture manager console. A repository must retain any current
posture information retrieved from the target endpoint and store it
indexed by the unique identifier for the endpoint. Any posture
collection manager specified by this profile must be able to
ascertain from its corresponding posture collection engine whether
the posture information is up to date. An interface on the posture
manager must support a request to obtain up-to-date information when
an endpoint is connected. This interface must also support the
ability to make a standard set of queries about the posture
information stored by the repository. In the future, some forms of
posture information might be retained at the endpoint. The interface
on the posture manager must accommodate the ability to make a request
to the corresponding posture collection engine about the posture of
the target endpoint. Standard data models and protocols also enable
the security of posture assessment results. By storing these results
indexed under the endpoint's unique identification, secure storage
itself enables endpoint posture information correlation, and ensures
that the enterprise's repositories always offer the freshest, most
up-to-date view of the enterprise's endpoint posture information
possible.
1.6. Posture Information Can Be Shared
By exposing posture information using a standard interface and API,
other security and operational components have a high level of
insight into the enterprise's endpoints and the software installed on
them. This will support innovation in the areas of asset management,
vulnerability scanning, and administrative interfaces, as any
authorized infrastructure endpoint can interact with the posture
information.
1.7. Enterprise Asset Posture Information Belongs to the Enterprise
Owners and administrators must have complete control of posture
information, policy, and endpoint mitigation. Standardized data
models, protocols and interfaces help to ensure that this posture
information is not locked in proprietary databases, but is made
available to its owners. This enables administrators to develop as
nuanced a policy as necessary to keep their networks secure.
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1.8. Keywords
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 [RFC2119]. This
specification does not distinguish blocks of informative comments and
normative requirements. Therefore, for the sake of clarity, note
that lower case instances of must, should, etc. do not indicate
normative requirements.
2. Terminology
This document uses terms as defined in [I-D.ietf-sacm-terminology]
unless otherwise specified.
3. Endpoint Posture Collection Profile
The EPCP describes how IETF data models and protocols can be used to
support the posture assessment of endpoints on a network. This
profile does not generate new data models or protocols; rather, it
offers best practices for a full end-to-end solution for posture
assessment, as well as a fresh perspective on how existing standards
can be leveraged against vulnerabilities.
3.1. Posture Assessments
The EPCP describes how IETF and TNC data models and protocols make it
possible to perform posture assessments against all network-connected
endpoints by:
1. uniquely identifying the endpoint;
2. collecting and evaluating posture based on data from the
endpoint;
3. creating a secure, authenticated, confidential channel between
the endpoint and the posture manager;
4. enabling the endpoint to notify the posture manager about changes
to its configuration;
5. enabling the posture manager to request information about the
configuration of the endpoint; and
6. storing the posture information in a repository linked to the
identifier for the endpoint.
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3.2. Data Storage
The EPCP focuses on being able to collect posture information from an
endpoint, store it, and make it available to authorized parties.
Currently, the EPCP does not specify a protocol or interfaces to
access stored posture information. This needs to be addressed in a
future revision. Until then, vendors are free to implement a
repository and the protocols and interfaces used to interact with it
in a way that makes the most sense for them.
3.3. Data Sharing
The EPCP aims to facilitate the sharing of posture information
between components to enable asset management, software asset
management, and configuration management use cases as well as support
analytic, access control, remediation, and reporting processes.
However, the EPCP does not currently specify a protocol for
communicating this information between components to support these
use cases and processes. This needs to be addressed in a future
revision.
4. EPCP Components
To perform posture assessment, data storage, and data sharing, EPCP
defines a number of components. Some of these components reside on
the target endpoint. Others reside on a posture manager that manages
communications with the target endpoint and stores the target
endpoint's posture information in a repository.
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Posture Manager Endpoint
Orchestrator +----------------+ +----------------+
+--------+ | | | |
| | | | | |
| |<---->| | | |
| | pub/ | | | |
| | sub | +------------+ | | +------------+ |
+--------+ | | | | | | | |
| | Posture | | | | Posture | |
Evaluator Repository | | Collection | | | | Collection | |
+------+ +--------+ | | Manager | |<-------| | Engine | |
| | | | | | | | report | | | |
| | | | | +------------+ | | +------------+ |
| |<-----> | |<---->| | query | |
| |request/| | store| |------->| |
| |respond | | | | | |
| | | | | | | |
+------+ +--------+ +----------------+ +----------------+
| ^
| query |
+-------------------------------------+
Figure 1: EPCP Components
4.1. Endpoint
An endpoint is defined in [RFC6876]. In the EPCP, the endpoint is
monitored by the enterprise and is the target of posture assessments.
To support these posture assessments, posture information is
collected via a posture collection engine.
4.1.1. Posture Collection Engine
The posture collection engine is located on the target endpoint and
receives queries from a posture collection manager. It also sends
collected posture information to the posture manager where it can be
sanity checked and stored in the repository. The posture collection
engine also contains a capability that sets up exchanges between the
target endpoint and posture manager. This capability makes the
posture collection engine responsible for performing the client-side
portion of encryption handshakes, and for locating authorized posture
managers with which to communicate.
4.2. Posture Manager
The posture manager is an endpoint that collects, validates, and
enriches posture information received about a target endpoint. It
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also stores the posture information it receives in the repository.
The posture manager does not evaluate the posture information.
4.2.1. Posture Collection Manager
A posture collection manager is a lightweight and extensible
component that facilitates the coordination and execution of posture
collection requests using collection mechanisms deployed across the
enterprise. The posture collection manager may query and retrieve
guidance from the repository to guide the collection of posture
information from the target endpoint.
The posture collection manager also contains a capability that sets
up exchanges between the target endpoint and the posture manager, and
manages data sent to and from posture collection engine. It is also
responsible for performing the server-side portion of encryption
handshakes.
4.3. Repository
The repository hosts guidance, endpoint identification information,
and posture information reported by target endpoints where it is made
available to authorized components and persisted over a period of
time set by the administrator. Information stored in the repository
will be accessible to authorized parties via a standard
administrative interface as well as through a standardized API. The
repository may be a standalone component or may be located on the
posture manager. Furthermore, an implementation is not restricted to
a single repository and may leverage several repositories to provide
this functionality.
Currently, the EPCP does not provide a standardized interface or API
for accessing the information contained within the repository. A
future revision of the EPCP may specify a standardized interface and
API for components to interact with the repository.
4.4. Evaluator
The evaluator assesses the posture status of a target endpoint by
comparing collected posture information against the desired state of
the target endpoint specified in guidance. The evaluator queries and
retrieves the appropriate guidance from the repository as well as
queries and retrieves the posture information required for the
assessment from the repository. If the required posture information
is not available in the repository, the evaluator may request the
posture information from the posture collection manager, which will
result in the collection of additional posture information from the
target endpoint. This information is subsequently stored in the
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repository where it is made available to the evaluator and other
components. The results of the assessment are stored in the
repository where they are available to tools and administrators for
follow-up actions, further evaluation, and historical purposes.
4.5. Orchestrator
The orchestrator provides a publish/subscribe interface for the
repository so that infrastructure endpoints can subscribe to and
receive published posture assessment results from the repository
regarding endpoint posture changes.
The EPCP does not currently define an orchestrator component nor does
it specify a standardized publish/subscribe interface for this
purpose. Future revisions of the EPCP may specify such an interface.
5. EPCP Transactions
5.1. Provisioning
An endpoint is provisioned with one or more attributes that will
serve as its unique identifier on the network as well as the
components necessary to interact with the posture manager. The
endpoint is deployed on the network.
NOTE: TO BE EXPANDED
5.2. Discovery and Validation
If necessary, the target endpoint finds and validates the posture
manager. The posture collection engine on the target endpoint and
posture collection manager on the posture manager complete an
encryption handshake, during which endpoint identity information is
exchanged.
5.3. Event Driven Collection
The posture assessment is initiated when the posture collector engine
on the target endpoint notices that relevant posture information on
the endpoint has changed. Then, the posture collection engine
initiates a posture assessment information exchange with the posture
collection manager.
5.4. Querying
The posture assessment is initiated by the posture collection
manager. This can occur because:
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1. policy states that a previous assessment has aged out or become
invalid, or
2. the posture collection manager is alerted by a sensor or an
administrator (via the posture manager's administrative
interface) that an assessment must be completed
5.5. Data Storage
Once posture information is received by the posture manager, it is
forwarded to the repository. The repository could be co-located with
the posture manager, or there could be direct or brokered
communication between the posture manager and the repository. The
posture information is stored in the repository along with past
posture information collected about the target endpoint.
5.6. Data Sharing
Because the target endpoint posture information was sent in
standards-based data models over secure, standardized protocols, and
then stored in a centralized repository linked to unique endpoint
identifiers, authorized parties are able to access the posture
information. Such authorized parties may include, but are not
limited to, administrators or endpoint owners (via the posture
manager's administrative interface), evaluators that access the
repository directly, and orchestrators that rely on publish/subscribe
communications with the repository.
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Posture Manager Endpoint
Orchestrator +----------------+ +----------------+
+--------+ | | | |
| | | | | |
| |<---->| | | |
| | pub/ | | | |
| | sub | +------------+ | | +------------+ |
+--------+ | | | | | | | |
| | Posture | | | | Posture | |
Evaluator Repository | | Collection | | | | Collection | |
+------+ +--------+ | | Manager | |<-------| | Engine | |
| | | | | | | | report | | | |
| | | | | +------------+ | | +------------+ |
| |<-----> | |<---->| | query | |
| |request/| | store| |------->| |
| |respond | | | | | |
| | | | | | | |
+------+ +--------+ +----------------+ +----------------+
| ^
| query |
+-------------------------------------+
+--------------------------------+
| Administrative Interface |
| and API |
+--------------------------------+
Figure 2: Exposing Data to the Network
6. EPCP Implementations
The following sections describe implementations of the EPCP
leveraging the IETF NEA and IETF NETMOD architectures.
6.1. IETF NEA EPCP Implementation for Traditional Endpoints
When EPCP is used, posture collectors running on the target endpoint
gather posture information as changes occur on the endpoint. The
data is aggregated by the posture broker client and forwarded to a
posture manager, over a secure channel, via the posture transport
client. Once received by the posture transport server on the posture
manager, the posture information is directed by the posture broker
server to the appropriate posture validators where it can be
processed and stored in a repository. There the posture information
can be used by other tools to carry out assessment tasks. Posture
collectors can also be queried by posture validators to refresh
posture information about the target endpoint or to ask a specific
question about posture information. This is shown in Figure 3.
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Posture Posture
Collection Collection
Manager Engine
+---------------+ +---------------+
| | | |
| +-----------+ | PA-TNC | +-----------+ |
| | Posture | |--------| | Posture | |
| | Validator | | | | Collector | |
| +-----------+ | | +-----------+ |
| | | | | |
| | IF-IMV | | | IF-IMC |
| | | | | |
| +-----------+ | PB-TNC | +-----------+ |
| | PB Server | |--------| | PB Client | |
| +-----------+ | | +-----------+ |
| | | | | |
| | | | | |
| | | | | |
| +-----------+ | | +-----------+ |
| | PT Server | |<------>| | PT Client | |
| +-----------+ | PT-TLS | +-----------+ |
| | | |
+---------------+ +---------------+
Figure 3: NEA Components
These requirements are written with a view to performing a posture
assessment on an endpoint; as the EPCP grows and evolves, these
requirements will be expanded to address issues that arise. Note
that these requirements refer to defined components of the NEA
architecture. As with the NEA architecture, vendors have discretion
as to how these NEA components map to separate pieces of software or
endpoints.
It should be noted that the posture broker client and posture
transport client components of the posture collection engine and the
posture broker server and posture transport server components of the
posture collection manager would likely need to be implemented by a
single vendor because there are no standardized interfaces between
the respective components and would not be interoperable.
6.1.1. Endpoint Pre-Provisioning
An endpoint is provisioned with a machine certificate that will serve
as its unique identifier on the network as well as the components
necessary to interact with the posture manager. This includes a
posture collection engine to manage requests from the posture manager
and the posture collectors necessary to collect the posture
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information of importance to the enterprise. The endpoint is
deployed on the network.
The target endpoint SHOULD authenticate to the posture manager using
a machine certificate during the establishment of the outer tunnel
achieved with the posture transport protocol defined in [RFC6876].
[IF-IMV] specifies how to pull an endpoint identifier out of a
machine certificate. An endpoint identifier SHOULD be created in
conformance with [IF-IMV] from a machine certificate sent via
[RFC6876].
In the future, the identity could be a hardware certificate compliant
with [IEEE-802-1ar]; ideally, this identifier SHOULD be associated
with the identity of a hardware cryptographic module, in accordance
with [IEEE-802-1ar], if present on the endpoint. The enterprise
SHOULD stand up a certificate root authority; install its root
certificate on endpoints and on the posture manager; and provision
the endpoints and the posture manager with machine certificates. The
target endpoint MAY authenticate to the posture manager using a
combination of the machine account and password; however, this is
less secure and not recommended.
6.1.2. Endpoint
The endpoint MUST conform to [RFC5793], which levies a number of
requirements against the endpoint. An endpoint that complies with
these requirements will be able to:
1. attempt to initiate a session with the posture manager if the
posture makes a request to send an update to posture manager;
2. notify the posture collector if no PT-TLS session with the
posture manager can be created;
3. notify the posture collector when a PT-TLS session is
established; and
4. receive information from the posture collectors, forward this
information to the posture manager via the posture collection
engine.
6.1.2.1. Posture Collector
Any posture collector used in an EPCP solution MUST be conformant
with [IF-IMC]; an Internet-Draft, under development, that is a subset
of the TCG TNC Integrity Measurement Collector interface [IF-IMC] and
will be submitted in the near future.
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6.1.2.2. Posture Broker Client
The posture broker client MUST conform to [IF-IMC] to enable
communications between the posture broker client and the posture
collectors on the endpoint.
6.1.2.3. Posture Transport Client
The posture transport client MUST implement PT-TLS.
The posture transport client MUST support the use of machine
certificates for TLS at each endpoint consistent with the
requirements stipulated in [RFC6876] and [Server-Discovery].
The posture transport client MUST be able to locate an authorized
posture manager, and switch to a new posture manager when required by
the network, in conformance with [Server-Discovery].
6.1.3. Posture Manager
The posture manager MUST conform to all requirements in the
[RFC5793].
6.1.3.1. Posture Validator
Any posture validator used in an EPCP solution MUST be conformant
with [IF-IMV]; an Internet-Draft, under development, that is a subset
of the TCG TNC Integrity Measurement Verifier interface [IF-IMV] and
will be submitted in the near future.
6.1.3.2. Posture Broker Server
The posture broker server MUST conform to [IF-IMV]. Conformance to
[IF-IMV] enables the posture broker server to obtain endpoint
identity information from the posture transport server, and pass this
information to any posture validators on the posture manager.
6.1.3.3. Posture Transport Server
The posture transport server MUST implement PT-TLS.
The posture transport server MUST support the use of machine
certificates for TLS at each endpoint consistent with the
requirements stipulated in [RFC6876] and [Server-Discovery].
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6.1.4. Repository
EPCP requires a simple administrative interface for the repository.
Posture validators on the posture manager receive the target endpoint
posture information via PA-TNC [RFC5792] messages sent from
corresponding posture collectors on the target endpoint. The posture
validators store this information in the repository linked to the
identity of the target endpoint where the posture collectors are
located.
6.1.5. IETF SACM SWAM Extension to the IETF NEA EPCP Implementation
This section defines the requirements associated with the software
asset management extension [I-D.ietf-sacm-nea-swima-patnc] to the
IETF NEA EPCP implementation.
6.1.5.1. Endpoint Pre-Provisioning
This section defines the requirements associated with implementing
SWIMA.
The following requirements assume that the platform or OS vendor
supports the use of SWID tags and has identified a standard directory
location for the SWID tags to be located as specified by [SWID].
6.1.5.2. SWID Tags
The primary content for the EPCP is the information conveyed in the
elements of a SWID tag.
The endpoint MUST have SWID tags stored in a directory specified in
[SWID]. The tags SHOULD be provided by the software vendor; they MAY
also be generated by:
o the software installer; or
o third-party software that creates tags based on the applications
it sees installed on the endpoint.
The elements in the SWID tag MUST be populated as specified in
[SWID]. These tags, and the directory in which they are stored, MUST
be updated as software is added, removed, or updated.
6.1.5.3. SWID Posture Collectors and Posture Validators
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6.1.5.3.1. The SWID Posture Collector
For the EPCP, the SWID posture collector MUST be conformant with
[I-D.ietf-sacm-nea-swima-patnc], which includes requirements for:
1. Collecting SWID tags from the SWID directory
2. Monitoring the SWID directory for changes
3. Initiating a session with the posture manager to report changes
to the directory
4. Maintaining a list of changes to the SWID directory when updates
take place and no PT-TLS connection can be created with the
posture manager
5. Responding to a request for SWID tags from the SWID Posture
Validator on the posture manager
6. Responding to a query from the SWID posture validator as to
whether all updates have been sent
The SWID posture collector is not responsible for detecting that the
SWID directory was not updated when an application was either
installed or uninstalled.
6.1.5.3.2. The SWID Posture Validator
Conformance to [I-D.ietf-sacm-nea-swima-patnc] enables the SWID
posture validator to:
1. Send messages to the SWID posture collector (at the behest of the
administrator at the posture manager console) requesting updates
for SWID tags located on endpoint
2. Ask the SWID posture collector whether all updates to the SWID
directory located at the posture manager have been sent
3. Compare an endpoint's SWID posture information to policy, and
make a recommendation to the posture manager about the endpoint
In addition to these requirements, a SWID posture validator used in
conformance with this profile MUST be capable of passing information
from the posture assessment results and the endpoint identity
associated with those results to the repository for storage.
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6.1.5.4. Repository
The administrative interface SHOULD enable an administrator to:
1. Query which endpoints have reported SWID tags for a particular
application
2. Query which SWID tags are installed on an endpoint
3. Query tags based on characteristics, such as vendor, publisher,
etc.
6.2. IETF NETMOD EPCP Implementation for Network Device Endpoints
When EPCP is used, a NETCONF client that implements the posture
collection manager sends a query to target network device endpoint
requesting posture information over a secure channel. Once the
NETCONF server on the endpoint receives the request, it queries one
or more datastores for the posture information. The NETCONF server
then reports the information back to the NETCONF client where it can
be stored in a repository for use by other tools. This is shown in
Figure 4.
Posture Posture
Collection Collection
Manager Engine
+---------------+ +---------------+
| | | |
| | | +-----------+ |
| | | | Data | |
| | | | Store(s) | |
| | | +-----------+ |
| | | | |
| | | | |
| +-----------+ | | +-----------+ |
| | NETCONF | | | | NETCONF | |
| | Client | |<------->| | Server | |
| +-----------+ | NETCONF | +-----------+ |
| | | |
+---------------+ +---------------+
Figure 4: NETMOD Components
These requirements are written with a view to performing a posture
assessment on network device endpoints (routers, switches, etc.); as
the EPCP grows and evolves, these requirements will be expanded to
address issues that arise.
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Note that these requirements refer to defined components of the
NETMOD architecture and map back to EPCP. As with the NETMOD
architecture, vendors have discretion as to how these NETMOD
components map to separate pieces of software or endpoints.
6.2.1. Endpoint Pre-Provisioning
For the posture manager to be able to query the datastores on the
endpoint, the endpoint MUST be configured to grant the posture
manager access to its datastores as described in [RFC6241]. The
posture manager is identified by its NETCONF username.
6.2.2. Posture Manager Pre-Provisioning
For the posture manager to be able to query the datastores on the
endpoint, the posture manager MUST be provisioned with a NETCONF
username that will be used to authenticate the posture manager to the
endpoint as described in [RFC6241]. The username generated will be
determined by the selected transport protocol.
6.2.3. Endpoint
An endpoint MUST conform to the requirements outlined for servers in
the NETCONF protocol as defined in [RFC6241]. This requires the
implementation of NETCONF over SSH [RFC6242]. An endpoint MAY
support the NETCONF protocol over other transports such as TLS
[RFC7589] as well as the RESTCONF protocol as defined in [RFC8040].
6.2.3.1. Datastore
A NETCONF datastore on an endpoint MUST support the operations
outlined in [RFC6241], but, the actual implementation of the
datastore is left to the endpoint vendor.
Datastores MUST support the YANG data modeling language [RFC7950] for
expressing endpoint posture information in a structured format. In
addition, datastores MAY support other data models such as XML (via
YIN) for representing posture information.
Datastores MUST support the compliance posture information specified
in [RFC7317]. Datastores MAY support other models standardized or
proprietary as deemed appropriate by the endpoint vendor.
6.2.4. Posture Manager
A posture manager MUST conform to the requirements specified for
clients in the NETCONF protocol as defined in [RFC6241]. This
requires the implementation of NETCONF over SSH [RFC6242]. A posture
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manager MAY also support the NETCONF protocol over other transports
such as TLS [RFC7589]. In addition, a posture manager MAY support
the RESTCONF protocol as defined in [RFC8040].
While ad-hoc fetch/polling via NETCONF and RESTCONF is useful for
assessing endpoint compliance, such solutions by themselves are not
able to detect changes as they occur on the endpoint. As a result, a
future revision of this document will support
[I-D.ietf-netconf-yang-push] to receive updates on YANG-modeled
posture information. Similarly, because not all posture information
is modeled in YANG, a future revision of this document will reference
[I-D.ietf-netconf-subscribed-notifications] once it is a standard to
support continuous streams of unstructured data from the endpoint to
the posture manager.
6.2.5. Repository
EPCP requires a simple administrative interface for the repository.
The posture collection manager on the posture manager receives the
target endpoint posture information via NETCONF [RFC6241] messages
sent from posture collection engine on the target endpoint. The
posture collection manager stores this information in the repository
linked to the identity of the target endpoint from which it was
collected.
6.3. Administrative Interface and API
An interface is necessary to allow administrators to manage the
endpoints and software used in the EPCP. This interface SHOULD be
accessible either on or through (as in the case of a remotely hosted
interface) the posture manager. Using this interface, an authorized
user or administrator SHOULD be able to:
o Query the repository
o Send commands to the posture collection managers, requesting
information from the associated posture collection engines
residing on endpoints
o Update the policy that resides on the posture manager
An API is necessary to allow infrastructure endpoints and software
access to the information stored in the repository. Using this API,
an authorized endpoint SHOULD be able to:
o Query the repository
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7. EPCP Use Cases
The following sections describe the different use cases supported by
the EPCP.
7.1. Hardware Asset Management
Using the administrative interface on the posture manager, an
authorized user can learn:
o what endpoints are connected to the network at any given time; and
o what SWID tags were reported for the endpoints.
The ability to answer these questions offers a standards-based
approach to asset management, which is a vital part of enterprise
processes such as compliance report generation for the Federal
Information Security Modernization Act (FISMA), Payment Card Industry
Data Security Standard (PCI DSS), Health Insurance Portability and
Accountability Act (HIPAA), etc.
7.2. Software Asset Management
The administrative interface on the posture manager provides the
ability for authorized users and infrastructure to know which
software is installed on which endpoints on the enterprise's network.
This allows the enterprise to answer questions about what software is
installed to determine if it is licensed or prohibited. This
information can also drive other use cases such as:
o vulnerability management: knowing what software is installed
supports the ability to determine which endpoints contain
vulnerable software and need to be patched.
o configuration management: knowing which security controls need to
be applied to harden installed software and better protect
endpoints.
7.3. Vulnerability Searches
The administrative interface also provides the ability for authorized
users or infrastructure to locate endpoints running software for
which vulnerabilities have been announced. Because of
1. the unique IDs assigned to each endpoint; and
2. the rich application data provided in the endpoints' posture
information,
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the repository can be queried to find all endpoints running a
vulnerable application. Endpoints suspected of being vulnerable can
be addressed by the administrator or flagged for further scrutiny.
7.4. Threat Detection and Analysis
The repository's standardized API allows authorized infrastructure
endpoints and software to search endpoint posture assessment
information for evidence that an endpoint's software inventory has
changed, and can make endpoint software inventory data available to
other endpoints. This automates security data sharing in a way that
expedites the correlation of relevant network data, allowing
administrators and infrastructure endpoints to identify odd endpoint
behavior and configuration using secure, standards-based data models
and protocols.
8. Non-supported Use Cases
Several use cases, including but not limited to these, are not
covered by the EPCP:
o Gathering non-standardized types of posture information: The EPCP
does not prevent administrators from collecting posture
information in proprietary formats from the endpoint; however it
does not set requirements for doing so.
o Solving the lying endpoint problem: The EPCP does not address the
lying endpoint problem; the Profile makes no assertions that it
can catch an endpoint that is, either maliciously or accidentally,
reporting false posture information to the posture manager.
However, other solutions may be able to use the posture
information collected using the capabilities described in this
profile to catch an endpoint in a lie. For example, a sensor may
be able to compare the posture information it has collected on an
endpoint's activity on the network to what the endpoint reported
to the server and flag discrepancies. However, these capabilities
are not described in this profile.
9. Endpoint Posture Collection Profile Examples
The following subsections provide examples of the EPCP as implemented
using components from the NEA architecture.
9.1. Continuous Posture Assessment of an Endpoint
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Endpoint Posture Manager
+---------------+ +---------------+
| | | |
| +-----------+ | | +-----------+ |
| | SWID | | | | SWID | |
| | Posture | | | | Posture | |
| | Collector | | | | Validator | |
| +-----------+ | | +-----------+ |
| | | | | |
| | IF-IMC | | | IF-IMV |
| | | | | |
| +-----------+ | | +-----------+ |
| | PB Client | | | | PB Server | |
| +-----------+ | | +-----------+ |
| | | | | |
| | | | | |
| | | | | |
| +-----------+ | | +-----------+ |
| | PT Client | |<------>| | PT Server | |
| +-----------+ | PT-TLS | +-----------+ |
| | | |
+---------------+ +---------------+
Figure 5: Continuous Posture Assessment of an Endpoint
9.1.1. Change on Endpoint Triggers Posture Assessment
A new application is installed on the endpoint, and the SWID
directory is updated. This triggers an update from the SWID posture
collector to the SWID posture validator. The message is sent down
the NEA stack, encapsulated by NEA protocols until it is sent by the
posture transport client to the posture transport server. The
posture transport server then forwards it up through the stack, where
the layers of encapsulation are removed until the SWID Message
arrives at the SWID posture validator.
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Endpoint Posture Manager
+---------------+ +---------------+
| | | |
| +-----------+ | | +-----------+ |
| | SWID | | | | SWID | |
| | Posture | | | | Posture | |
| | Collector | | | | Validator | |
| +-----------+ | | +-----------+ |
| | | SWID Message | | |
| | IF-IMC | for PA-TNC | | IF-IMV |
| | | | | |
| +-----------+ | | +-----------+ |
| | PB Client | | | | PB Server | |
| +-----------+ | | +-----------+ |
| | | | | |
| | | PB-TNC {SWID | | |
| | | Message for | | |
| | | PA-TNC} | | |
| +-----------+ | | +-----------+ |
| | PT Client | |<-------------->| | PT Server | |
| +-----------+ | PT-TLS {PB-TNC | +-----------+ |
| | {SWID Message | |
+---------------+ for PA-TNC}} +---------------+
Figure 6: Compliance Protocol Encapsulation
The SWID posture validator stores the new tag information in the
repository. If the tag indicates that the endpoint is compliant to
the policy, then the process is complete until the next time an
update is needed (either because policy states that the endpoint must
submit posture assessment results periodically or because an
install/uninstall/update on the endpoint triggers a posture
assessment).
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Endpoint Posture Manager
+---------------+ +---------------+
| | | |
| +-----------+ | | +-----------+ |
| | SWID | | | | SWID |-|-+
| | Posture | | | | Posture | | |
| | Collector | | | | Validator | | |
| +-----------+ | | +-----------+ | |
| | | | | | | Repository
| | IF-IMC | | | IF-IMV | | +--------+
| | | | | | | | |
| +-----------+ | | +-----------+ | | | |
| | PB Client | | | | PB Server | | +---->| |
| +-----------+ | | +-----------+ | | |
| | | | | | +--------+
| | | | | |
| | | | | |
| +-----------+ | | +-----------+ |
| | PT Client | |<------>| | PT Server | |
| +-----------+ | PT-TLS | +-----------+ |
| | | |
+---------------+ +---------------+
Figure 7: Storing SWIDs in the Repository
If the endpoint has fallen out of compliance with a policy, the
posture manager can alert the administrator via the posture manager's
administrative interface. The administrator can then take steps to
address the problem. If the administrator has already established a
policy for automatically addressing this problem, that policy will be
followed.
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(")
__|__
+-->|
Endpoint Posture Manager | / \
+---------------+ +---------------+ |
| | | | |
| +-----------+ | | +-----------+ | |
| | SWID | | | | SWID |-|-+
| | Posture | | | | Posture | |
| | Collector | | | | Validator | |
| +-----------+ | | +-----------+ |
| | | | | | Repository
| | IF-IMC | | | IF-IMV | +--------+
| | | | | | | |
| +-----------+ | | +-----------+ | | |
| | PB Client | | | | PB Server | | | |
| +-----------+ | | +-----------+ | | |
| | | | | | +--------+
| | | | | |
| | | | | |
| +-----------+ | | +-----------+ |
| | PT Client | |<------>| | PT Server | |
| +-----------+ | PT-TLS | +-----------+ |
| | | |
+---------------+ +---------------+
Figure 8: Server Alerts Network Admin
9.2. Administrator Searches for Vulnerable Endpoints
An announcement is made that a particular version of a piece of
software has a vulnerability. The administrator uses the
administrative interface on the server to search the repository for
endpoints that reported the SWID tag for the vulnerable software.
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(")
__|__
+-->|
Endpoint Posture Manager | / \
+---------------+ +---------------+ |
| | | | |
| +-----------+ | | +-----------+ | |
| | SWID | | | | SWID |-|-+
| | Posture | | | | Posture | |
| | Collector | | | | Validator | |
| +-----------+ | | +-----------+ |
| | | | | | Repository
| | IF-IMC | | | IF-IMV | +--------+
| | | | | | | |
| +-----------+ | | +-----------+ | | |
| | PB Client | | | | PB Server | |------>| |
| +-----------+ | | +-----------+ | | |
| | | | | | +--------+
| | | | | |
| | | | | |
| +-----------+ | | +-----------+ |
| | PT Client | |<------>| | PT Server | |
| +-----------+ | PT-TLS | +-----------+ |
| | | |
+---------------+ +---------------+
Figure 9: Admin Searches for Vulnerable Endpoints
The repository returns a list of entries in the matching the
administrator's search. The administrator can then address the
vulnerable endpoints by taking some follow-up action such as removing
it from the network, quarantining it, or updating the vulnerable
software.
10. Future Work
This section captures ideas for future work related to EPCP that
might be of interest to the IETF SACM WG. These ideas are listed in
no particular order.
o Integrate the IETF NETMOD Yang Push architecture.
o Add support endpoint types beyond workstations, servers, and
network infrastructure devices.
o Examine the integration of [I-D.ietf-mile-xmpp-grid].
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o Define a standard interface and API for interacting with the
repository. Requirements to consider include: creating a secure
channel between a publisher and the repository, creating a secure
channel between a subscriber and the repository, and the types of
interactions that must be supported between publishers and
subscribers to a repository.
o Define a standard interface for communications between the posture
broker client and posture transport client(s) as well as the
posture broker server and posture transport server(s).
o Retention of posture information on the target endpoint.
o Define an orchestrator component as well as publish/subscribe
interface for it.
o Define an evaluator component as well as an interface for it.
11. Acknowledgements
The authors wish to thank all of those in the TCG TNC work group who
contributed to development of the TNC ECP specification upon which
this document is based.
+-----------------------+-------------------------------------------+
| Member | Organization |
+-----------------------+-------------------------------------------+
| Padma Krishnaswamy | Battelle Memorial Institute |
| | |
| Eric Fleischman | Boeing |
| | |
| Richard Hill | Boeing |
| | |
| Steven Venema | Boeing |
| | |
| Nancy Cam-Winget | Cisco Systems |
| | |
| Scott Pope | Cisco Systems |
| | |
| Max Pritikin | Cisco Systems |
| | |
| Allan Thompson | Cisco Systems |
| | |
| Nicolai Kuntze | Fraunhofer Institute for Secure |
| | Information Technology (SIT) |
| | |
| Ira McDonald | High North |
| | |
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| Dr. Andreas Steffen | HSR University of Applied Sciences |
| | Rapperswil |
| | |
| Josef von Helden | Hochschule Hannover |
| | |
| James Tan | Infoblox |
| | |
| Steve Hanna (TNC-WG | Juniper Networks |
| Co-Chair) | |
| | |
| Cliff Kahn | Juniper Networks |
| | |
| Lisa Lorenzin | Juniper Networks |
| | |
| Atul Shah (TNC-WG Co- | Microsoft |
| Chair) | |
| | |
| Jon Baker | MITRE |
| | |
| Charles Schmidt | MITRE |
| | |
| Rainer Enders | NCP Engineering |
| | |
| Dick Wilkins | Phoenix Technologies |
| | |
| David Waltermire | NIST |
| | |
| Mike Boyle | U.S. Government |
| | |
| Emily Doll | U.S. Government |
| | |
| Jessica Fitzgerald- | U.S. Government |
| McKay | |
| | |
| Mary Lessels | U.S. Government |
| | |
| Chris Salter | U.S. Government |
+-----------------------+-------------------------------------------+
Table 1: Members of the TNC Work Group that Contributed to the
Document
12. IANA Considerations
This document does not define any new IANA registries. However, this
document does reference other documents that do define IANA
registries. As a result, the IANA Considerations section of the
referenced documents should be consulted.
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13. Security Considerations
The EPCP offers substantial improvements in endpoint security, as
evidenced by the Australian Defense Signals Directorate's analysis
that 85% of targeted cyber intrusions can be prevented through
application whitelisting, patching applications and operating
systems, and using the latest versions of applications. [DSD]
Despite these gains, some security risks continue to exist and must
be considered.
To ensure that these benefits and risks are properly understood, this
Security Considerations section includes an analysis of the benefits
provided by the EPCP (Section 13.1), the attacks that may be mounted
against systems that implement the EPCP (Section 13.2), and the
countermeasures that may be used to prevent or mitigate these attacks
(Section 13.3). Overall, a substantial reduction in cyber risk can
be achieved.
13.1. Security Benefits of Endpoint Posture Collection Profile
Security weaknesses of the components for this profile should be
considered in light of the practical considerations that must be
addressed to have a viable solution.
Posture assessment has two parts: assessment and follow-up actions.
The point of posture assessment is to ensure that authorized users
are using authorized software configured to be as resilient as
possible against an attack.
Posture assessment answers the question whether the endpoint is
healthy. Our goal for posture assessment is to make it harder for an
adversary to execute code on one of our endpoints. This profile
represents an important first step in reaching that goal. If we keep
our endpoints healthier, we are able to prevent more attacks on our
endpoints and thus on our information systems.
The goal of EPCP is to address posture assessment in stages. Stage 1
is the ability to ascertain whether all endpoints are authorized and
whether all applications are authorized and up to date. Stage 2 will
attempt to address the harder problem of whether all software is
configured safely. Eventually, the goal is to also address
remediation which is currently out-of-scope for the SACM WG; that
presents a far greater security challenge than reporting, since
remediation implies the ability of a remote party to modify software
or its settings on endpoints.
A second security consideration is how to gain visibility over every
type of endpoint and every piece of software installed on the
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endpoint. This is a problem of scaling and observation. A solution
is needed that can report from every type of endpoint. All software
on the endpoint has to be discovered. Information about the software
has to be up to date and accurate. The information that is
discovered has to be reported in a consistent format, so
administrators do not have to squander time deciphering proprietary
systems and the information can be made readily useful for other
security automation purposes.
EPCP is based on a model of a standards-based schema, a standards-
based set of protocols and interfaces, and the existence of an
oversight group, the IETF, that can update the data models and
protocols to meet new use cases and security issues that may be
discovered.
The data elements in the schema determine what work can be done
consistently for every endpoint and every piece of software. How the
data gets populated is an important consideration. EPCP leverages
the SWID tags from ISO 19770-2 because the tag originates with a
single authoritative source, the application vendor itself.
Moreover, there is a natural incentive for the vendor to create this
content, since it makes it easier for enterprises and vendors to
track whether software is licensed. Practical considerations are
security considerations. A sustainable business model for obtaining
all the necessary content is a fundamental requirement.
The NEA implementation of EPCP is based on having a NEA client run on
an endpoint that publishes posture information to a server. The
advantages are easy to list. A platform vendor can implement its own
NEA client and have it be compatible with the NEA server from a
different vendor. The interfaces are layered on top of mature
protocols such as TLS. TLS is the protocol of choice for EPCP,
since:
o it has proven secure properties,
o it can be implemented on most types of endpoints,
o it allows the gathering of large amounts of information when a
endpoint is connected, and
o it enables use of a mechanism to ensure that the client is
authenticated (authorized) - a client certificate - which also
provides a consistent identifier.
Mature protocols that can be implemented on most types of endpoints
and a standards-based schema with a sustainable business model are
both critical security considerations for compliance.
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Additionally, it is important to consider the future stages for EPCP
such as a posture assessment being followed up by some action (e.g.
remediation, alert, etc.). Ensuring that clients are taking
instructions only from authorized parties will be critical. Inasmuch
as it is practical, enterprises will want to use the same
infrastructure and investment in PKI to send those instructions to a
client.
Likewise, as more information with more value is gathered from
endpoints, we will also want to ensure that this information is only
released to authorized applications and parties. For the next stage
of EPCP, SACM may want to define an interface on the repository that
can be queried by other security automation applications to make it
easier to detect attacks and for other security automation
applications. This interface has to be standards-based for
enterprises to reap the benefits of innovation that can be achieved
by making the enterprise's data available to other tools and
services.
13.2. Threat Model
This section lists the attacks that can be mounted on a NEA
implementation of an EPCP environment. The following section
(Section 13.3) describes countermeasures.
Because the EPCP describes a specific use case for NEA components,
many security considerations for these components are addressed in
more detail in the technical specifications:
[I-D.ietf-sacm-nea-swima-patnc], [IF-IMC], [RFC5793],
[Server-Discovery], [RFC6876], [IF-IMV].
13.2.1. Endpoint Attacks
While the EPCP provides substantial improvements in endpoint security
as described in Section 13.1, a certain percentage of endpoints will
always get compromised. For this reason, all parties must regard
data coming from endpoints as potentially unreliable or even
malicious. An analogy can be drawn with human testimony in an
investigation or trial. Human testimony is essential but must be
regarded with suspicion.
o Compromise of endpoint: A compromised endpoint may report false
information to confuse or even provide maliciously crafted
information with a goal of infecting others.
o Putting bad information in SWID directory: Even if an endpoint is
not completely compromised, some of the software running on it may
be unreliable or even malicious. This software, potentially
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including the SWID generation or discovery tool, or malicious
software pretending to be a SWID generation or discovery tool, can
place incorrect or maliciously crafted information into the SWID
directory. Endpoint users may even place such information in the
directory, whether motivated by curiosity or confusion or a desire
to bypass restrictions on their use of the endpoint.
o Identity spoofing (impersonation): A compromised endpoint may
attempt to impersonate another endpoint to gain its privileges or
to besmirch the reputation of that other endpoint.
13.2.2. Network Attacks
A variety of attacks can be mounted using the network. Generally,
the network cannot be trusted.
o Eavesdropping, modification, injection, replay, deletion
o Traffic analysis
o Denial of service and blocking traffic
13.2.3. Posture Manager Attacks
The posture manager is a critical security element and therefore
merits considerable scrutiny.
o Compromised trusted manager: A compromised posture manager or a
malicious party that is able to impersonate a posture manager can
incorrectly grant or deny access to endpoints, place incorrect
information into the repository, or send malicious messages to
endpoints.
o Misconfiguration of posture manager: Accidental or purposeful
misconfiguration of a trusted posture manager can cause effects
that are similar to those listed for compromised trusted posture
manager.
o Malicious untrusted posture manager: An untrusted posture manager
cannot mount any significant attacks because all properly
implemented endpoints will refuse to engage in any meaningful
dialog with such a posture manager.
13.2.4. Repository Attacks
The repository is also an important security element and therefore
merits careful scrutiny.
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o Putting bad information into trusted repository: An authorized
repository client such as a server may be able to put incorrect
information into a trusted repository or delete or modify
historical information, causing incorrect decisions about endpoint
security. Placing maliciously crafted data in the repository
could even lead to compromise of repository clients, if they fail
to carefully check such data.
o Compromised trusted repository: A compromised trusted repository
or a malicious untrusted repository that is able to impersonate a
trusted repository can lead to effects similar to those listed for
"Putting bad information into trusted repository". Further, a
compromised trusted repository can report different results to
different repository clients or deny access to the repository for
selected repository clients.
o Misconfiguration of trusted repository: Accidental or purposeful
misconfiguration of a trusted repository can deny access to the
repository or result in loss of historical data.
o Malicious untrusted repository: An untrusted repository cannot
mount any significant attacks because all properly implemented
repository clients will refuse to engage in any meaningful dialog
with such a repository.
13.3. Countermeasures
This section lists the countermeasures that can be used in a NEA
implementation of an EPCP environment.
13.3.1. Countermeasures for Endpoint Attacks
This profile is in and of itself a countermeasure for a compromised
endpoint. A primary defense for an endpoint is to run up to date
software configured to be run as safely as possible.
Ensuring that anti-virus signatures are up to date and that a
firewall is configured are also protections for an endpoint that are
supported by the current NEA specifications.
Endpoints that have hardware cryptographic modules that are
provisioned by the enterprise, in accordance with [IEEE-802-1ar], can
protect the private keys used for authentication and help prevent
adversaries from stealing credentials that can be used for
impersonation. Future versions of the EPCP may want to discuss in
greater detail how to use a hardware cryptographic module, in
accordance with [IEEE-802-1ar], to protect credentials and to protect
the integrity of the code that executes during the bootstrap process.
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13.3.2. Countermeasures for Network Attacks
To address network attacks, [RFC6876] includes required encryption,
authentication, integrity protection, and replay protection.
[Server-Discovery] also includes authorization checks to ensure that
only authorized servers are trusted by endpoints. Any unspecified or
not yet specified network protocols employed in the EPCP (e.g. the
protocol used to interface with the repository) should include
similar protections.
These protections reduce the scope of the network threat to traffic
analysis and denial of service. Countermeasures for traffic analysis
(e.g. masking) are usually impractical but may be employed.
Countermeasures for denial of service (e.g. detecting and blocking
particular sources) SHOULD be used when appropriate to detect and
block denial of service attacks. These are routine practices in
network security.
13.3.3. Countermeasures for Posture Manager Attacks
Because of the serious consequences of posture manager compromise,
posture managers SHOULD be especially well hardened against attack
and minimized to reduce their attack surface. They SHOULD be
monitored using the NEA protocols to ensure the integrity of the
behavior and analysis data stored on the posture manager and SHOULD
utilize a [IEEE-802-1ar]compliant hardware cryptographic module for
identity and/or integrity measurements of the posture manager. They
should be well managed to minimize vulnerabilities in the underlying
platform and in systems upon which the posture manager depends.
Network security measures such as firewalls or intrusion detection
systems may be used to monitor and limit traffic to and from the
posture manager. Personnel with administrative access to the posture
manager should be carefully screened and monitored to detect problems
as soon as possible. Posture manager administrators should not use
password-based authentication but should instead use non-reusable
credentials and multi-factor authentication (where available).
Physical security measures should be employed to prevent physical
attacks on posture managers.
To ease detection of posture manager compromise should it occur,
posture manager behavior should be monitored to detect unusual
behavior (such as a server reboot, unusual traffic patterns, or other
odd behavior). Endpoints should log and/or notify users and/or
administrators when peculiar posture manager behavior is detected.
To aid forensic investigation, permanent read-only audit logs of
security-relevant information pertaining to posture manager
(especially administrative actions) should be maintained. If posture
manager compromise is detected, the posture manager's certificate
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should be revoked and careful analysis should be performed of the
source and impact of this compromise. Any reusable credentials that
may have been compromised should be reissued.
Endpoints can reduce the threat of server compromise by minimizing
the number of trusted posture managers, using the mechanisms
described in [Server-Discovery].
13.3.4. Countermeasures for Repository Attacks
If the host for the repository is located on its own endpoint, it
should be protected with the same measures taken to protect the
posture manager. In this circumstance, all messages between the
posture manager and repository should be protected with a mature
security protocol such as TLS or IPsec.
The repository can aid in the detection of compromised endpoints if
an adversary cannot tamper with its contents. For instance, if an
endpoint reports that it does not have an application with a known
vulnerability installed, an administrator can check whether the
endpoint might be lying by querying the repository for the history of
what applications were installed on the endpoint.
To help prevent tampering with the information in the repository:
1. Only authorized parties should have privilege to run code on the
endpoint and to change the repository.
2. If a separate endpoint hosts the repository, then the
functionality of that endpoint should be limited to hosting the
repository. The firewall on the repository should only allow
access to the posture manager and to any endpoint authorized for
administration.
3. The repository should ideally use "write once" media to archive
the history of what was placed in the repository, to include a
snapshot of the current status of applications on endpoints.
14. Privacy Considerations
The EPCP specifically addresses the collection of posture data from
enterprise endpoints by an enterprise network. As such, privacy is
not going to often arise as a concern for those deploying this
solution.
A possible exception may be the concerns a user may have when
attempting to connect a personal endpoint (such as a phone or mobile
endpoint) to an enterprise network. The user may not want to share
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certain details, such as an endpoint identifier or SWID tags, with
the enterprise. The user can configure their NEA client to reject
requests for this information; however, it is possible that the
enterprise policy will not allow the user's endpoint to connect to
the network without providing the requested data.
15. Change Log
15.1. -01 to -02
Addressed various comments from the SACM WG.
Added a section for the collection of posture information from
network devices using standards from the NETMOD WG.
Updated EPCP component diagrams so they were not specific to a NEA-
based implementation.
Updated EPCP NEA example diagrams to reflect all the components in
the NEA architecture.
15.2. -00 to -01
There are no textual changes associated with this revision. This
revision simply reflects a resubmission of the document so that it
remains in active status.
15.3. -01 to -02
Added references to the Software Inventory Message and Attributes
(SWIMA) for PA-TNC I-D.
Replaced references to PC-TNC with IF-IMC.
Removed erroneous hyphens from a couple of section titles.
Made a few minor editorial changes.
15.4. -02 to -00
Draft adopted by IETF SACM WG.
15.5. -00 to -01
Significant edits to up-level the draft to describe SACM collection
over multiple different protocols.
Replaced references to SANS with CIS.
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Made other minor editorial changes.
16. References
16.1. Informative References
[CIS] http://www.cisecurity.org/controls/, "CIS Critical
Security Controls".
[DSD] http://www.dsd.gov.au/publications/csocprotect/
top_4_mitigations.htm, "Top 4 Mitigation Strategies to
Protect Your ICT System", November 2012.
[IEEE-802-1ar]
Institute of Electrical and Electronics Engineers, "IEEE
802.1ar", December 2009.
[RFC5209] Sangster, P., Khosravi, H., Mani, M., Narayan, K., and J.
Tardo, "Network Endpoint Assessment (NEA): Overview and
Requirements", RFC 5209, DOI 10.17487/RFC5209, June 2008,
<https://www.rfc-editor.org/info/rfc5209>.
[TNC] Trusted Computing Group, "TCG Trusted Network Connect TNC
Architecture for Interoperability, Version 1.5", February
2012.
16.2. Normative References
[I-D.ietf-mile-xmpp-grid]
Cam-Winget, N., Appala, S., Pope, S., and P. Saint-Andre,
"Using XMPP for Security Information Exchange", draft-
ietf-mile-xmpp-grid-04 (work in progress), October 2017.
[I-D.ietf-netconf-subscribed-notifications]
Voit, E., Clemm, A., Prieto, A., Nilsen-Nygaard, E., and
A. Tripathy, "Customized Subscriptions to a Publisher's
Event Streams", draft-ietf-netconf-subscribed-
notifications-13 (work in progress), June 2018.
[I-D.ietf-netconf-yang-push]
Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
Nygaard, E., Bierman, A., and B. Lengyel, "YANG Datastore
Subscription", draft-ietf-netconf-yang-push-12 (work in
progress), December 2017.
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[I-D.ietf-sacm-nea-swima-patnc]
Schmidt, C., Haynes, D., Coffin, C., Waltermire, D., and
J. Fitzgerald-McKay, "Software Inventory Message and
Attributes (SWIMA) for PA-TNC", draft-ietf-sacm-nea-swima-
patnc-01 (work in progress), September 2017.
[I-D.ietf-sacm-terminology]
Waltermire, D., Montville, A., Harrington, D., and N. Cam-
Winget, "Terminology for Security Assessment", draft-ietf-
sacm-terminology-05 (work in progress), August 2014.
[IF-IMC] Trusted Computing Group, "TCG Trusted Network Connect TNC
IF-IMC, Version 1.3", February 2013.
[IF-IMV] Trusted Computing Group, "TCG Trusted Network Connect TNC
IF-IMV, Version 1.4", December 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5792] Sangster, P. and K. Narayan, "PA-TNC: A Posture Attribute
(PA) Protocol Compatible with Trusted Network Connect
(TNC)", RFC 5792, DOI 10.17487/RFC5792, March 2010,
<https://www.rfc-editor.org/info/rfc5792>.
[RFC5793] Sahita, R., Hanna, S., Hurst, R., and K. Narayan, "PB-TNC:
A Posture Broker (PB) Protocol Compatible with Trusted
Network Connect (TNC)", RFC 5793, DOI 10.17487/RFC5793,
March 2010, <https://www.rfc-editor.org/info/rfc5793>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6876] Sangster, P., Cam-Winget, N., and J. Salowey, "A Posture
Transport Protocol over TLS (PT-TLS)", RFC 6876,
DOI 10.17487/RFC6876, February 2013,
<https://www.rfc-editor.org/info/rfc6876>.
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[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, DOI 10.17487/RFC7317, August
2014, <https://www.rfc-editor.org/info/rfc7317>.
[RFC7589] Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
NETCONF Protocol over Transport Layer Security (TLS) with
Mutual X.509 Authentication", RFC 7589,
DOI 10.17487/RFC7589, June 2015,
<https://www.rfc-editor.org/info/rfc7589>.
[RFC7632] Waltermire, D. and D. Harrington, "Endpoint Security
Posture Assessment: Enterprise Use Cases", RFC 7632,
DOI 10.17487/RFC7632, September 2015,
<https://www.rfc-editor.org/info/rfc7632>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[Server-Discovery]
Trusted Computing Group, "DRAFT: TCG Trusted Network
Connect PDP Discovery and Validation, Version 1.0",
October 2015.
[SWID] "Information technology--Software asset management--Part
2: Software identification tag", ISO/IEC 9899:1999, 2009.
Authors' Addresses
Danny Haynes
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730
USA
Email: dhaynes@mitre.org
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Jessica Fitzgerald-McKay
Department of Defense
9800 Savage Road
Ft. Meade, Maryland
USA
Email: jmfitz2@nsa.gov
Lisa Lorenzin
Pulse Secure
2700 Zanker Rd., Suite 200
San Jose, CA 95134
US
Email: llorenzin@pulsesecure.net
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