Secure Automation and Continuous Monitoring (SACM) Requirements
draft-ietf-sacm-requirements-01

Abstract

This document defines the scope and set of requirements for the Secure Automation and Continuous Monitoring working group. The requirements and scope are based on the agreed upon use cases.

Status of This Memo

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Table of Contents

• 1. Introduction
• 2. Requirements
• 2.1. Requirements for SACM
• 2.2. Requirements based on Use Cases
• 2.3. Requirements for the Architecture
• 2.4. Requirements for the Information Model
• 2.5. Requirements for Transport Protocols
• 3. Acknowledgements
• 4. IANA Considerations
• 5. Security Considerations
• 6. References
• 6.1. Normative References
• 6.2. Informative References
• Authors' Addresses

1. Introduction

Today's environment of rapidly-evolving security threats highlights the need to automate the sharing of such information while protecting user information as well as the systems that store, process, and transmit this information. Security threats can be detected in a number of ways. SACM's 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 particular, for the use cases as exemplified in [I-D.ietf-sacm-use-cases].Also, this document uses terminology defined in [I-D.ietf-sacm-terminology].

2. Requirements

This document defines requirements based on the SACM use cases defined in [I-D.ietf-sacm-use-cases]. This section describes the requirements used by SACM to assess and compare candidate information models and protocols to suit the architecture. These requirements express characteristics or features that a candidate protocol or data model must be capable of offering to ensure security and interoperability.

2.1. Requirements for SACM

In order to address the needs for determining, sharing and using posture information, the following tasks should be considered:

1. Define the assets. This is what we want to know about an asset. For instance, organizations will want to know what software is installed and its many critical security attributes such as patch level.
2. Resolve what assets actually compose an endpoint. This requires populating the data elements and attributes needed to exchange information pertaining to the assets composing an endpoint.
3. Determine the expected values for the data elements and attributes that need to be evaluated against the actual collected instances of asset data. This is how an organization can express its policy for an acceptable data element or attribute value. A system administrator can also identify specific data elements and attributes that represent problems, such as vulnerabilities, that need to be detected on an endpoint.
4. Evaluate the collected instances of the asset data against those expressed in the policy.
5. Report the results of the evaluation.

Many deployment scenarios can be instantiated to address the above tasks and use cases defined in [I-D.ietf-sacm-use-cases]. To ensure interoperability, scalability and flexibility in any of these deployments, the following requirements are defined for all use cases:

G-001

Extensibility: The data models, protocols and transports defined by SACM must be extensible to allow support for non-standard and future extensions. The transport protocol must support easily adding new operations while maintaining backwards compatibility. The query language must allow general inquiries as well as expression of specific paths to follow; retrieval of specific information based on an event, as well as on a continuous basis; and the ability to retrieve specific pieces of information, specific classes of information, and/or the entirety of available information. The information model must accommodate the addition of new data types and/or schemas in a backwards compatible fashion.

G-002

Interoperability: The data models, protocols and transports must be specified with enough details and state machine to ensure interoperability.

G-003

Scalability: The data models, protocols and transports must be scalable. SACM must support a broad set of deployment scenarios. As such, it is possible that the size of posture assessment information can vary from a single assessment that is small in (record or datagram) size to a very large datagram or a very large set of assessments. This must be defined by the SACM specifications defined.

G-004

Agility: The agility requirement is to ensure that the data model, protocols, transports are suitable to implementations are suitable to fit in different deployment models and scenarios. Considerations for the lightweight implementations of data models and transports is required. Use cases, especially in the vulnerability assessment and threat defense applications, require time criticality in both obtaining the information as well as consuming (e.g. parsing) the data.

G-005 / T-001

Transport variability: Moved to the Section 2.5.

G-006 / GN-005

Extensibility: A method for expressing both standard and non-standard (implemention-specific) data attributes while avoiding collisions should be defined. For interoperability and scope boundary, an explicit set of data attributes as mandatory to implement.

G-007 / GN-006/ T-002

Data Integrity: A method for ensuring data integrity must be provided. This method is required to be available (i.e. all data-handling components must support it), but is not required to be used in all cases.

G-008 / T-003

Data Protection: Moved to the Section 2.5.

G-009 / ARCH-004

Topology Flexibility: Moved to the Section 2.3.

G-010 / GN-007

Data Isolation: A method for partitioning data must be supported, to accommodate considerations such as geographic, regulatory, overlay boundaries and federation, where an organization may want to differentiate between information that can be shared outside its own domain and information that cannot. As with the requirement for data integrity, this method is required to be available (i.e. all data-handling components must support it), but is not required to be used in all cases.

G-011 / ARCH-005

Modularity: has been moved to the Section 2.3.

G-012 / GN-008

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

G-013 / GN-009

Discovery: There must be a mechanism 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), and where to go to get a specific piece of that information. For example, providing a method 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-014 / IM-013

Synchronization: has been moved to the Section 2.4.

G-015 / IM-014

Collection separation: has been moved to the Section 2.4.

G-016 / IM-015

Collection composition has been moved to the Section 2.4.

2.2. Requirements based on Use Cases

This section describes the requirements that may apply to information models, data models, protocols or transports as identified by the use cases in [I-D.ietf-sacm-use-cases] and referenced by the section numbers from that draft.

REQ-001

Attribute Dictionary: Use Cases in the whole of Section 2 describe the need for an Attribute Dictionary. With SACM's scope focused on Posture Assessment, the attribute collection and aggregation must have a well understood set of attributes inclusive of their meaning or usage intent.

REQ-002

Information Model: Use Case 2.1.1 describes the need for an Information Model to drive content definition. As SACM endeavors to reuse already existing standards which may have their own data models defined by instantiating an information model, the data models can be mapped to SACM's information model. See [RFC3444] for a description and distinctions between an information and data model.

REQ-003

Data Model to Protocol mapping: Use Case 2.1.1 describes the need to instantiate a data model that can map to the SACM protocols for posture content operations such as publication, query, change detection and asynchronous notifications.

REQ-004

Endpoint Discovery: Use Case 2.1.2 describes the need to discover endpoints and their composition.

REQ-005

Attribute based query: Use Case 2.1.2 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. .

REQ-006

Information based query with filtering: Use Case 2.1.3 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.

REQ-007

Asynchronous publication, updates or change modifications with filtering: Use Cases 2.1.3, 2.1.4 and 2.1.5 describe the need for the data model to support the means for the information to be published asynchronously. Similarly, the data model must support the means for a requestor to obtain updates or change modifications asynchronously. Like the query operation, these update notifications can be set up with a filter to allow for only a subset of posture assessment information to be obtained.

REQ-008

Data model scalability: Use Cases 2.1.4 and 2.1.5 describes 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.

REQ-009

Separation of Collection Request and Collection Action: the data model must distinguish the means to request for a data item to include enough information to properly identify the item to collect but the request could be separate and distinct from the actual method or process used to fulfill the request.

2.3. Requirements for the Architecture

At the simplest abstraction, the SACM architecture represents the core components and interfaces needed to perform the production and consumption of posture assessment information. Requirements relating the SACM's architecture include:

ARCH-001

Scalability: The architectural components must account for a range of deployments, from very small set of endpoints are used to very large deployments of more than several hundreds of thousands of endpoints.

ARCH-002

Agility: The architectural components must account for different deployment scenarios where the architectural components may be implemented, deployed or used within a single application, service, network or may comprise a federated system.

ARCH-003

Separation of Data and Management functions: SACM must define both the configuration and management of the SACM data models and protocols used to transport and share posture assessment information.

ARCH-004

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; systems can utilize an already established mutually agreed upon native data format, which may be standard or implementation-specific.

ARCH-005

Modularity: Announcement and negotiation of functional capabilities (such as authentication protocols, authorization schemes, data models, transport protocols, etc.) must be supported, enabling a SACM component to make inquiries about the capabilities of other components in the SACM ecosystem.

2.4. Requirements for the Information 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 it based on a specific data model. Thus, while there may exist different data models and schemas, they should adhere to a SACM information model that meets a set of requirements defined in this section.

The specific requirements include:

IM-001

Uniqueness of objects of reference, such as endpoints, IP addresses, etc.

IM-002

Mechanism to resolve or tolerate ambiguity in referents (e.g. same IP address used in two separate networks)

IM-003

Support for rootless searches and wildcard searches

IM-004

Ability to start a search anywhere in the tree, rather than at a specific leaf

IM-005

Data lifetime management (longevity or expiration of data)

IM-006

Data ephemerality (update vs. notify)

IM-007

Looseness of coupling between producer and consumer

IM-008

Ability to identify data from a specific producer

IM-009

Metadata cardinality - single-valued vs. multi-valued

IM-010

Capability negotiation - what data types and schemas are supported

IM-011

Provenance of data - for example:

• Publisher identity, classification, trustworthiness, authoritativeness
• Freshness of data
• Method by which data was generated (i.e. self-reported, reported by aggregator, result of scan, etc.)
• Location of data
• Delta results vs. total results

IM-012

Freshness: Published data must be associated with the time of origination - separately from the time of publication required in IM-013. This allows consumers can make decisions about the relevance of the data based on its currency and/or age.

IM-013

Synchronization: Request and response operations must be timestamped, and published information must 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 must be provided.

IM-014

Collection separation: 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 execute nor 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.

IM-015

Collection composition A collection request can be composed of multiple collection requests (which yield collected values). This must be able to 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 requester.

2.5. Requirements for Transport Protocols

The requirements for transport protocols include:

T-001

Transport variability: Different transports must be supported to address different deployment and time constraints. Supporting transports may be at the Layer 2, Layer 3 and higher application layers.

T-002

Data Integrity: A method for ensuring data integrity must be provided if required at the transport layer.

T-003

Data Protection: Transport protocols must ensure data protection for data in transit by encryption and robustness against protocol-based attacks. Protection for data at rest is not in scope for SACM. Data protection may be used for both privacy and non-privacy scenarios.

3. Acknowledgements

The authors would like to thank Barbara Fraser, Jim Bieda and Adam Montville for reviewing and contributing to this draft.

4. IANA Considerations

This memo includes no request to IANA.

5. Security Considerations

This document defines the requirements for SACM. As such, it is expected that several data models, protocols and transports may be defined or reused from already existing standards. This section will highlight security considerations that may apply to SACM based on the architecture and standards applied in SACM.

To address security and privacy considerations, the data model, protocols and transport 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 / data repositories.

In addition, authorization needs to extend to specific information or resources available in the environment. In other words, authorization should be based on both subject (the information requestor) and object (the information requested). The method by which this authorization is applied is unspecified.

6. References

6.1. Normative References

6.2. Informative References

Authors' Addresses