Internet Engineering Task Force (IETF) N. Cam-Winget

Internet Engineering Task Force (IETF) N. Cam-Winget
Request for Comments: 8248 Cisco Systems
Category: Informational L. Lorenzin
ISSN: 2070-1721 Pulse Secure
September 2017

Security Automation and Continuous Monitoring (SACM) Requirements

Abstract

This document defines the scope and set of requirements for the
Security Automation and Continuous Monitoring (SACM) architecture,
data model, and transfer protocols. The requirements and scope are
based on the agreed-upon use cases described in RFC 7632.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8248.

Copyright Notice

Copyright (c) 2017 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
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.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements for SACM . . . . . . . . . . . . . . . . . . 4
2.2. Requirements for the Architecture . . . . . . . . . . . . 7
2.3. Requirements for the Information Model . . . . . . . . . 9
2.4. Requirements for the Data Model . . . . . . . . . . . . . 10
2.5. Requirements for Data Model Operations . . . . . . . . . 12
2.6. Requirements for SACM Transfer Protocols . . . . . . . . 14
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
4. Security Considerations . . . . . . . . . . . . . . . . . . . 15
4.1. Trust between Provider and Requestor . . . . . . . . . . 16
4.2. Privacy Considerations . . . . . . . . . . . . . . . . . 17
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1. Normative References . . . . . . . . . . . . . . . . . . 18
5.2. Informative References . . . . . . . . . . . . . . . . . 18
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19

1. Introduction

Today's environment of rapidly evolving security threats highlights
the need to automate the sharing of security information (such as
posture information) while protecting user information and the
systems that store, process, and transmit this information. Security
threats can be detected in a number of ways. The Security Automation
and Continuous Monitoring (SACM) charter focuses on how to collect
and share this information based on use cases that involve posture
assessment of endpoints.

Scalable and sustainable collection, expression, and evaluation of
endpoint information is foundational to SACM's objectives. To secure
and defend a network, one must reliably determine what devices are on
the network, how those devices are configured from a hardware
perspective, what software products are installed on those devices,
and how those products are configured. We need to be able to
determine, share, and use this information in a secure, timely,
consistent, and automated manner to perform endpoint posture
assessments.

This document focuses on describing the requirements for facilitating
the exchange of posture assessment information in the enterprise, in
particular, for the use cases as exemplified in [RFC7632].

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As proposals are evaluated for SACM standardization, the documents
describing each proposal are expected to include a section that
describes how the enumerated requirements are addressed.

This document uses terminology defined in [TERMS].

1.1. Requirements Language

Use of each capitalized word within a sentence or phrase carries the
following meaning during the SACM WG's protocol selection process:

MUST - indicates an absolute requirement

MUST NOT - indicates something absolutely prohibited

SHOULD - indicates a strong recommendation of a desired result

SHOULD NOT - indicates a strong recommendation against a result

MAY - indicates a willingness to allow an optional outcome

When the words appear in lower case, their natural language meaning
is used.

2. Requirements

This document defines requirements based on the SACM use cases
described in [RFC7632]. This section describes the requirements used
by SACM to assess and compare candidate data models, interfaces, and
protocols. These requirements express characteristics or features
that a candidate protocol, information model, or data model must be
capable of offering to ensure security and interoperability.

Multiple data models, protocols, and transfers may be employed in a
SACM environment. A SACM transfer protocol is one that runs on top
of transport-layer protocols such as TCP/IP or internet-layer
protocols such as HTTP, carries operations (requests/responses), and
moves data.

SACM will define an architecture and information model focused on
addressing the needs for determining, sharing, and using posture
information securely via posture information providers and posture
information consumers. With the information model defining assets
and attributes to facilitate the guidance, collection, and assessment
of posture, tasks that should be considered include:

1. Asset Classification: Map the target endpoint and/or the assets
on the target endpoints to asset classes. This enables

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identification of the attributes needed to exchange information
pertaining to the target endpoint.

2. Attribute Definition: Define the attributes desired to be
collected from each target endpoint. For instance, organizations
will want to know what software is installed and its critical
security attributes such as patch level.

3. Policy Definition: This is where an organization can express its
policy for acceptable or problematic values of an endpoint
attribute. The expected values of an endpoint attribute are
determined for later comparison against the actual endpoint
attribute values during the evaluation process. Expected values
may include both values that are good as well as values that
represent problems, such as vulnerabilities. The organization
can also specify the endpoint attributes that are to be present
for a given target endpoint.

4. Information Collection: Collect information (attribute values)
from the target endpoint to populate the endpoint data.

5. Endpoint Assessment: Evaluate the actual values of the endpoint
attributes against those expressed in the policy. (An evaluation
result may become additional endpoint data.)

6. Result Reporting: Report the results of the evaluation for use by
other components. Examples of the use of a report would be
additional evaluation, network enforcement, vulnerability
detection, and license management.

2.1. Requirements for SACM

Many deployment scenarios can be instantiated to address the above
tasks and the use cases defined in [RFC7632]. To ensure
interoperability, scalability, and flexibility in any of these
deployments, the following requirements are defined for proposed SACM
standards:

G-001 (Solution Extensibility): The information model, data models,
protocols, and transfers defined by SACM MUST be designed to allow
support for future extensions. SACM MUST allow for both
standardized and proprietary extensions.

1. The information model and programmatic interfaces (see G-012 for
one example) MUST support the ability to add new operations
while maintaining backwards compatibility. SACM-defined
transfer protocols MUST have extensibility to allow them to
transfer operations that are defined in the future.

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2. The query language MUST allow for general inquiries as well as
expression of specific attributes or relationships between
attributes; the retrieval of specific information based on an
event or on a continuous basis; and the ability to retrieve
specific pieces of information, specific types or classes of
information, or the entirety of available information.

3. The information model MUST accommodate the interoperable
addition of new data types and/or schemas.

G-002 (Interoperability): The data models, protocols, and transports
MUST be specified with enough details to ensure interoperability.

G-003 (Scalability): SACM needs to support a broad set of deployment
scenarios. The data models, protocols, and transports have to be
scalable unless they are specifically defined to apply to a special-
purpose scenario, such as constrained devices. A SACM transfer
protocol standard SHOULD include a section on scalability
considerations that addresses the number of endpoints and amount of
information to which it can reasonably be expected to scale.
Scalability must be addressed to support:

* Large messages: It is possible that the size of posture
assessment information can vary from a single assessment that is
small in size to a very large message or a very large set of
assessments (up to multiple gigabytes in size).

* Large number of messages per second: A deployment may involve
many rapid or simultaneous events that require processing,
generating many messages per second.

* Large number of providers and consumers: A deployment may consist
of a very large number of endpoints requesting and/or producing
posture assessment information.

* Large number of target endpoints: A deployment may be managing
information of a very large number of target endpoints.

G-004 (Versatility): The data model, protocols, and transports must
be suitably specified to enable implementations to fit into
different deployment models and scenarios, including considerations
for implementations of data models and transports operating in
constrained environments. Separate solutions may be necessary to
meet the needs of specific deployment models and scenarios.

G-005 (Information Extensibility): Non-standard (implementation-
specific) attributes MUST be supported. A method SHOULD be defined
for preventing collisions from occurring in the naming of all

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attributes independent of their source. For interoperability and
scope boundary, the information model MUST define the mandatory set
of attributes.

G-006 (Data Protection): To protect the information being shared,
SACM components MUST protect the integrity and confidentiality of
data in transit (end to end) and data at rest (as information is
stored in repositories). Mechanisms for this protection are
unspecified but should include industry best practices. These
mechanisms are required to be available (i.e., all data-handling
components must support them) but are not required to be used in all
cases.

G-007 (Data Partitioning): A method for partitioning data MUST be
supported to accommodate considerations such as geographic,
regulatory, operational requirements, overlay boundaries, and
federation (where the data may be collected in multiple locations
and either centralized or kept in the local region). Where
replication of data is supported, it is required that methods exist
to prevent update loops.

G-008 (Versioning and Backward Compatibility): Announcement and
negotiation of versions, inclusive of existing capabilities (such as
transfer protocols, data models, specific attributes within data
models, standard attribute expression sets, etc.) MUST be supported.
Negotiation for both versioning and capabilities is needed to
accommodate future growth and ecosystems with mixed capabilities.

G-009 (Information Discovery): There MUST be mechanisms for
components to discover what information is available across the
ecosystem (i.e., a method for cataloging data available in the
ecosystem and advertising it to consumers), where to go to get a
specific piece of that information (i.e., which provider has the
information), and what schemas are in use for organizing the
information. For example, a method can be provided by which a node
can locate the advertised information so that consumers are not
required to have a priori knowledge to find available information.

G-010 (Target Endpoint Discovery): SACM MUST define the means by
which target endpoints may be discovered. The use case in
Section 2.1.2 of [RFC7632] describes the need to discover endpoints
and their composition.

G-011 (Push and Pull Access): Three methods of data access MUST be
supported: a Pull model, a solicited Push model, and an unsolicited
Push model. All of the methods of data access MUST support the
ability for the initiator to filter the set of posture assessment
information to be delivered. Additionally, the provider of the

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information MUST be able to filter the set of posture assessment
information based on the permissions of the recipient. This
requirement is driven by the use cases in Sections 2.1.3 and 2.1.4
of [RFC7632].

G-012 (SACM Component Interface): The interfaces by which SACM
components communicate to share endpoint posture information MUST be
well defined. That is, the interface defines the data model, SACM
transfer protocols, and network transfer protocols to enable SACM
components to communicate.

G-013 (Endpoint Location and Network Topology): The SACM
architecture and interfaces MUST allow for the target endpoint
(network) location and network topology to be modeled and
understood. Where appropriate, the data model and the interfaces
SHOULD allow for discovery of the target endpoint location, network
topology, or both.

G-014 (Target Endpoint Identity): The SACM architecture and
interfaces MUST support the ability of components to provide
attributes that can be used to compose an identity for a target
endpoint. These identities MAY be composed of attributes from one
or more SACM components.

G-015 (Data Access Control): Methods of access control must be
supported to accommodate considerations such as geographic,
regulatory, operational, and federations. Entities accessing or
publishing data MUST identify themselves and pass access policy.

2.2. Requirements for the Architecture

Following are the requirements for the SACM architecture:

ARCH-001 (Component Functions): At the simplest abstraction, the
SACM architecture MUST represent the core components and interfaces
needed to perform the production and consumption of posture
assessment information.

ARCH-002 (Scalability): The architectural components MUST account
for a range of deployments, from very small sets of endpoints to
very large deployments.

ARCH-003 (Flexibility): The architectural components MUST account
for different deployment scenarios where the architectural
components may be implemented, deployed, or used within a single
application, service, or network, or may comprise a federated
system.

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ARCH-004 (Separation of Data and Management Functions): SACM MUST
define both the configuration and management of the SACM data models
and protocols used to transfer and share posture assessment
information.

ARCH-005 (Topology Flexibility): Both centralized and decentralized
(peer-to-peer) information exchange MUST be supported. Centralized
data exchange enables use of a common data format to bridge together
data exchange between diverse systems and can leverage a virtual
data store that centralizes and offloads all data access, storage,
and maintenance to a dedicated resource. Decentralized data
exchange enables simplicity of sharing data between relatively
uniform systems and between small numbers of systems, especially
within a single enterprise domain. The fact that a centralized or
decentralized deployment is used SHOULD be invisible to a consumer.
However, there may be cases where the producer chooses to include
that information due to consumer preference.

ARCH-006 (Capability Negotiation): Announcement and negotiation of
functional capabilities (such as authentication protocols,
authorization schemes, data models, transfer protocols, etc.) MUST
be supported, enabling a SACM component to make inquiries about the
capabilities of other components in the SACM ecosystem.

ARCH-007 (Role-Based Authorization): The SACM architecture MUST be
capable of effecting role-based authorization. Distinction of
endpoints capable of and authorized to provide or consume
information is required to address appropriate access controls.

ARCH-008 (Context-Based Authorization): The SACM architecture MUST
be capable of effecting context-based authorization. Different
policies (e.g., business, regulatory, etc.) might specify what data
may be exposed to, or shared by, consumers based on one or more
attributes of the consumer. The policy might specify that consumers
are required to share specific information either back to the system
or to administrators.

ARCH-009 (Time Synchronization): Actions or decisions based on time-
sensitive data (such as user logon/logoff, endpoint connection/
disconnection, endpoint behavior events, etc.) are all predicated on
a synchronized understanding of time. The SACM architecture MUST
provide a mechanism for all components to synchronize time. A
mechanism for detecting and reporting time discrepancies SHOULD be
provided by the architecture and reflected in the information model.

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2.3. Requirements for the Information Model

The SACM information model represents the abstracted representation
for posture assessment information to be communicated. SACM data
models must adhere to and comply with the SACM information model.
The requirements for the SACM information model include:

IM-001 (Extensible Attribute Vocabulary): The information model MUST
define a minimum set of attributes for communicating posture
information, to ensure interoperability between data models.
(Individual data models may define attributes beyond the mandatory-
to-implement minimum set.) The attributes should be defined with a
clear mechanism for extensibility to enable data models to adhere to
SACM's required attributes as well as allow for their own
extensions. The attribute vocabulary should be defined with a clear
mechanism for extensibility to enable future versions of the
information model to be interoperably expanded with new attributes.

IM-002 (Posture Data Publication): The information model MUST allow
for the data to be provided by a SACM component either solicited or
unsolicited. No aspect of the information model should be dependent
upon or assume a Push or Pull model of publication.

IM-003 (Data Model Negotiation): SACM's information model MUST allow
support for different data models, data model versions, and
different versions of the operations on the data models and transfer
protocols. The SACM information model MUST include the ability to
discover and negotiate the use of a particular data model or any
data model.

IM-004 (Data Model Identification): The information model MUST
provide a means to uniquely identify each data model. The
identifier MUST contain both an identifier of the data model and a
version indicator for the data model. The identifiers SHOULD be
decomposable so that a customer can query for any version of a
specific data model and compare returned values for older or newer
than a desired version.

IM-005 (Data Lifetime Management): The information model MUST
provide a means to allow data models to include data lifetime
management. The information model must identify attributes that can
allow data models to, at minimum, identify the data's origination
time and expected time of next update or data longevity (how long
the data should be assumed to still be valid).

IM-006 (Singularity and Modularity): The SACM information model MUST
be singular (i.e., there is only one information model, not multiple
alternative information models from which to choose) and MAY be

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modular (a conjunction of several subcomponents) for ease of
maintenance and extension. For example, endpoint identification
could be an independent subcomponent of the information model, to
simplify updating of endpoint identification attributes.

2.4. Requirements for the Data Model

The SACM information model represents an abstraction for "what"
information can be communicated and "how" it is to be represented and
shared. It is expected that as applications may produce posture
assessment information, they may share it using a specific data
model. Similarly, applications consuming or requesting posture
assessment information may require that it be based on a specific
data model. Thus, while there may exist different data models and
schemas, they should adhere to the SACM information model and meet
the requirements defined in this section.

The specific requirements for candidate data models include:

DM-001 (Element Association): A SACM information model consists of a
set of SACM information model elements. A SACM data model MUST be
derived from the SACM information model. A SACM data model consists
of a set of SACM data model elements. In this derivation, a SACM
data model element MAY map to one or more SACM information model
elements. In addition, a SACM data model MAY include additional
data model elements that are not associated with any SACM
information model elements.

DM-002 (Data Model Structure): The data model can be structured
either as one single module or separated into modules and submodules
that allow for references between them. The data model structure
MAY reflect structure in the information model but does not need to.
For example, the data model might use one module to define
endpoints, and that module might reference other modules that
describe the various assets associated with the endpoint.
Constraints and interfaces might further be defined to resolve or
tolerate ambiguity in the references (e.g., the same IP address used
in two separate networks).

DM-003 (Search Flexibility): The search interfaces and actions MUST
include the ability to start a search anywhere within a data model
structure and the ability to search based on patterns ("wildcard
searches") as well as specific data elements.

DM-004 (Full vs. Partial Updates): The data model SHOULD include the
ability to allow providers of data to provide the data as a whole or
when updates occur. For example, a consumer can request a full
update on initial engagement, then request to receive deltas

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(updates containing only the changes since the last update) on an
ongoing basis as new data is generated.

DM-005 (Loose Coupling): The data model SHOULD allow for a loose
coupling between the provider and the consumer, such that the
consumer can request information without being required to request
it from a specific provider, and a provider can publish information
without having a specific consumer targeted to receive it.

DM-006 (Data Cardinality): The data model MUST describe their
constraints (e.g., cardinality). As posture information and the
tasks for collection, aggregation, or evaluation could comprise one
or more attributes, interfaces and actions MUST allow and account
for such cardinality and for conditional, optional, or mandatory
attributes.

DM-007 (Data Model Negotiation): The interfaces and actions in the
data model MUST include capability negotiation to enable discovery
of supported and available data types and schemas.

DM-008 (Data Origin): The data model MUST include the ability for
consumers to identify the data origin (provider that collected the
data).

DM-009 (Origination Time): The data model SHOULD allow the provider
to include the information's origination time.

DM-010 (Data Generation): The data model MUST allow the provider to
include attributes defining how the data was generated (e.g., self-
reported, reported by aggregator, scan result, etc.).

DM-011 (Data Source): The data model MUST allow the provider to
include attributes identifying the data source (target endpoint from
which the data was collected), e.g., hostname, domain (DNS) name, or
application name.

DM-012 (Data Updates): The data model SHOULD allow the provider to
include attributes defining whether the information provided is a
delta, partial, or full set of information.

DM-013 (Multiple Collectors): The data model MUST support the
collection of attributes by a variety of collectors, including
internal collectors, external collectors with an authenticated
relationship with the endpoint, and external collectors based on
network and other observers.

DM-014 (Attribute Extensibility): All of the use cases in Section 2
of [RFC7632] describe the need for an attribute dictionary. With

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SACM's scope focused on posture assessment, the data model attribute
collection and aggregation MUST have a well-understood set of
attributes inclusive of their meaning or usage intent. The data
model MUST include all attributes defined in the information model
and MAY include additional attributes beyond those found in the
information model. Additional attributes MUST be defined in
accordance with the extensibility framework provided in the
information model (see IM-001).

DM-015 (Solicited vs. Unsolicited Updates): The data model MUST
enable a provider to publish data either solicited (in response to a
request from a consumer) or unsolicited (as new data is generated,
without a request required). For example, an external collector can
publish data in response to a request by a consumer for information
about an endpoint, or it can publish data as it observes new
information about an endpoint, without any specific consumer request
triggering the publication; a compliance-server provider may publish
endpoint posture information in response to a request from a
consumer (solicited), or it may publish posture information driven
by a change in the posture of the endpoint (unsolicited).

DM-016 (Transfer Agnostic): The data model MUST be transfer
agnostic, to allow for the data operations to leverage the most
appropriate SACM transfer protocol.

2.5. Requirements for Data Model Operations

Posture information data adhering to a data model must also provide
interfaces that include operations for access and production of the
data. Operations requirements are distinct from transfer
requirements in that operations requirements are requirements on the
application performing requests and responses, whereas transfer
requirements are requirements on the transfer protocol carrying the
requests and responses. The specific requirements for such
operations include:

OP-001 (Time Synchronization): Request and response operations MUST
be timestamped, and published information SHOULD capture time of
publication. Actions or decisions based on time-sensitive data
(such as user logon/logoff, endpoint connection/disconnection,
endpoint behavior events, etc.) are all predicated on a synchronized
understanding of time. A method for detecting and reporting time
discrepancies SHOULD be provided.

OP-002 (Collection Abstraction): Collection is the act of a SACM
component gathering data from a target endpoint. The request for a
data item MUST include enough information to properly identify the
item to collect, but the request shall not be a command to directly

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execute nor be directly applied as arguments to a command. The
purpose of this requirement is primarily to reduce the potential
attack vectors but has the additional benefit of abstracting the
request for collection from the collection method, thereby allowing
more flexibility in how collection is implemented.

OP-003 (Collection Composition): A collection request MAY be
composed of multiple collection requests (which yield collected
values). The desire for multiple values MUST be expressed as part
of the collection request, so that the aggregation can be resolved
at the point of collection without having to interact with the
requestor. This requirement should not be interpreted as preventing
a collector from providing attributes that were not part of the
original request.

OP-004 (Attribute-Based Query): A query operation is the act of
requesting data from a provider. Query operations SHOULD be based
on a set of attributes. Query operations MUST support both a query
for specific attributes and a query for all attributes. The use
case in Section 2.1.2 of [RFC7632] describes the need for the data
model to support a query operation based on a set of attributes to
facilitate collection of information such as posture assessment,
inventory (of endpoints or endpoint components), and configuration
checklist.

OP-005 (Information-Based Query with Filtering): The query operation
MUST support filtering. The use case in Section 2.1.3 of [RFC7632]
describes the need for the data model to support the means for the
information to be collected through a query mechanism. Furthermore,
the query operation requires filtering capabilities to allow for
only a subset of information to be retrieved. The query operation
MAY be a synchronous request or asynchronous request.

OP-006 (Operation Scalability): The operation resulting from a query
operation MUST be able to handle the return and receipt of large
amounts of data. The use case in Section 2.1.4 of [RFC7632]
describe the need for the data model to support scalability. For
example, the query operation may result in a very large set of
attributes as well as a large set of targets.

OP-007 (Data Abstraction): The data model MUST allow a SACM
component to communicate what data was used to construct the target
endpoint's identity, so that other SACM components can determine
whether they are constructing an equivalent target endpoint (and its
identity) and whether they have confidence in that identity. SACM
components SHOULD have interfaces defined to transmit this data
directly or to refer to where the information can be retrieved.

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OP-008 (Provider Restriction): Request operations MUST include the
ability to restrict the data to be provided by a specific provider
or a provider with specific characteristics. Response operations
MUST include the ability to identify the provider that supplied the
response. For example, a SACM consumer should be able to request
that all of the data come from a specific provider by identity
(e.g., Provider A) or from a provider that is in a specific location
(e.g., in the Boston office).

2.6. Requirements for SACM Transfer Protocols

The term "SACM transfer protocol" is intended to be distinguished
from underlying transport- and internet-layer protocols such as TCP/
IP or operating at an application-layer protocol such as HTTP. The
SACM transfer protocol is focused on moving data and performing
necessary access control operations; it is agnostic to the data model
operations.

The requirements for SACM transfer protocols include:

T-001 (Multiple Transfer Protocol Support): SACM transfer protocols
will vary depending on the deployment model that relies on different
transfer-layer requirements, different device capabilities, and
system configurations dealing with connectivity. For example, where
posture attributes may be collected directly from an endpoint using
the Network Endpoint Assessment (NEA) model [RFC5209], different
transports may be defined to collect them using Posture Transport
Protocol for Extensible Authentication Protocol Tunnel Methods (PT-
EAP) [RFC7171] or Posture Transport Protocol over TLS (PT-TLS)
[RFC6876], depending on the deployment scenario.

T-002 (Data Integrity): SACM transfer protocols MUST be able to
ensure data integrity for data in transit.

T-003 (Data Confidentiality): SACM transfer protocols MUST be able
to support data confidentiality. SACM transfer protocols MUST
ensure data protection for data in transit (e.g., by encryption) to
provide confidentiality, integrity, and robustness against protocol-
based attacks. Note that while the transfer MUST be able to support
data confidentiality, implementations MAY provide a configuration
option that enables and disables confidentiality in deployments.
Protection for data at rest is not in scope for transfer protocols.
Data protection MAY be used for both privacy and non-privacy
scenarios.

T-004 (Transfer Protection): SACM transfer protocols MUST be capable
of supporting mutual authentication and replay protection.

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T-005 (Transfer Reliability): SACM transfer protocols MUST provide
reliable delivery of data. This includes the ability to perform
fragmentation and reassembly and to detect replays. The SACM
transfer may take advantage of reliability features in the network
transport; however, the network transport may be unreliable (e.g.,
UDP), in which case the SACM transfer running over the unreliable
network transport is responsible for ensuring reliability (i.e., by
provisions such as confirmations and retransmits).

T-006 (Transfer-Layer Requirements): Each SACM transfer protocol
MUST clearly specify the transport-layer requirements it needs to
operate correctly. Examples of items that may need to be specified
include connectivity requirements, replay requirements, data link
encryption requirements, and/or channel-binding requirements. These
requirements are needed in order for deployments to be done
correctly.

T-007 (Transfer Protocol Adoption): SACM SHOULD, where reasonably
possible, leverage and use existing IETF transfer protocols versus
defining new ones.

3. IANA Considerations

This document does not require any IANA actions.

4. Security Considerations

This document defines the requirements for SACM. As such, it is
expected that several data models, protocols, and transfer protocols
may be defined or reused from already-existing standards.

To address security and privacy considerations, the data model,
protocols, and transports must consider authorization based on
consumer function and privileges, to only allow authorized consumers
and providers to access specific information being requested or
published.

To enable federation across multiple entities (such as across
organizational or geographic boundaries), authorization must also
extend to infrastructure elements themselves, such as central
controllers, brokers, and data repositories.

In addition, authorization needs to extend to specific information or
resources available in the environment. In other words,
authorization is based on the subject (the information requestor),
the provider (the information responder), the object (the endpoint
the information is being requested on), and the attribute (what piece

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of data is being requested). The method by which this authorization
is applied is unspecified.

SACM's charter focuses on the workflow orchestration and the sharing
of posture information for improving the efficacy of security
applications such as compliance, configuration, assurance, and other
threat and vulnerability reporting and remediation systems. While
the goal is to facilitate the flow of information securely, it is
important to note that participating endpoints may not be cooperative
or trustworthy.

4.1. Trust between Provider and Requestor

The information given from the provider to a requestor may come with
different levels of trustworthiness given the different potential
deployment scenarios and compromise at the provider, the requesting
consumer, or devices that are involved in the transfer between the
provider and requestor. This section will describe the different
considerations that may reduce the level of trustworthiness of the
information provided.

In the information transfer flow, it is possible that some of the
devices may serve as proxies or brokers and, as such, may be able to
observe the communications flowing between an information provider
and requestor. Without appropriate protections, it is possible for
these proxies and brokers to inject and affect man-in-the-middle
attacks.

In general, it is common to distrust the network service provider,
unless the full hop-by-hop communications process flow is well
understood. As such, the posture information provider should protect
the posture information data it provides as well as the transfer it
uses. Similarly, while there may be providers whose goal is to
openly share its information, there may also be providers whose
policy is to grant access to certain posture information based on its
business or regulatory policy. In those situations, a provider may
require full authentication and authorization of the requestor (or
set of requestors) and share only the authorized information to the
authenticated and authorized requestors.

Beyond distrusting the network service provider, a requestor must
also take into account that the information received from the
provider may have been communicated through an undetermined network
communications system. That is, the posture information may have
traversed through many devices before reaching the requestor. SACM
specifications should provide the means for verifying data origin and
data integrity and, at minimum, provide endpoint authentication and
transfer integrity.

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A requestor may require data freshness indications, both knowledge of
data origination as well as time of publication, so that it can make
more informed decisions about the relevance of the data based on its
currency and/or age.

It is also important to note that endpoint assessment reports,
especially as they may be provided by the target endpoint, may pose
untrustworthy information. The considerations for this are described
in Section 8 of [RFC5209].

The trustworthiness of the posture information given by the provider
to one or many requestors is dependent on several considerations.
Some of these include the requestor requiring:

o Full disclosure of the network topology path to the provider(s).

o Direct (peer-to-peer) communication with the provider.

o Authentication and authorization of the provider.

o Either or both confidentiality and integrity at the transfer
layer.

o Either or both confidentiality and integrity at the data layer.

4.2. Privacy Considerations

SACM information may contain sensitive information about the target
endpoint as well as revealing identity information of the producer or
consumer of such information. Similarly, as part of the SACM
discovery mechanism, the capabilities and roles (e.g., SACM
components enabled) advertised by the endpoint may be construed as
private information.

In addition to identity and SACM capabilities information disclosure,
the use of timestamps (or other attributes that can be used as
identifiers) could be further used to determine a target endpoint or
user's behavioral patterns. Such attributes may also be deemed
sensitive and may require further protection or obfuscation to meet
privacy concerns. That is, there may be applications as well as
business and regulatory practices that require that aspects of such
information be hidden from any parties that do not need to know it.

Data confidentiality can provide some level of privacy but may fall
short where unnecessary data is still transmitted. In those cases,
filtering requirements at the data model such as OP-005 must be
applied to ensure that such data is not disclosed. [RFC6973]

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provides guidelines that SACM protocols, information models, and data
models should follow.

5. References

5.1. Normative References

[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>.

5.2. Informative References

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

[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>.

[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/info/rfc6973>.

[RFC7171] Cam-Winget, N. and P. Sangster, "PT-EAP: Posture Transport
(PT) Protocol for Extensible Authentication Protocol (EAP)
Tunnel Methods", RFC 7171, DOI 10.17487/RFC7171, May 2014,
<https://www.rfc-editor.org/info/rfc7171>.

[TERMS] Birkholz, H., Lu, J., Strassner, J., and N. Cam-Winget,
"Security Automation and Continuous Monitoring (SACM)
Terminology", Work in Progress, draft-ietf-sacm-
terminology-13, July 2017.

Acknowledgments

The authors would like to thank Barbara Fraser, Jim Bieda, and Adam
Montville for reviewing and contributing to this document. In
addition, we recognize valuable comments and suggestions made by Jim
Schaad and Chris Inacio.

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Authors' Addresses

Nancy Cam-Winget
Cisco Systems
3550 Cisco Way
San Jose, CA 95134
United States of America

Email: [email protected]

Lisa Lorenzin
Pulse Secure
2700 Zanker Rd., Suite 200
San Jose, CA 95134
United States of America

Email: [email protected]

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