Committee Specification Draft 01

16 November 2022

This stage:

https://docs.oasis-open.org/openc2/oc2ls/v2.0/csd01/oc2ls-v2.0-csd01.md (Authoritative)
https://docs.oasis-open.org/openc2/oc2ls/v2.0/csd01/oc2ls-v2.0-csd01.html
https://docs.oasis-open.org/openc2/oc2ls/v2.0/csd01/oc2ls-v2.0-csd01.pdf

Previous stage:

N/A

Latest stage:

https://docs.oasis-open.org/openc2/oc2ls/v2.0/oc2ls-v2.0.md (Authoritative)
https://docs.oasis-open.org/openc2/oc2ls/v2.0/oc2ls-v2.0.html
https://docs.oasis-open.org/openc2/oc2ls/v2.0/oc2ls-v2.0.pdf

Technical Committee:

OASIS Open Command and Control (OpenC2) TC

Chairs:

Duncan Sparrell (duncan@sfractal.com), sFractal Consulting LLC
Michael Rosa (mjrosa@nsa.gov), National Security Agency

Editors:

Duncan Sparrell (duncan@sfractal.com), sFractal Consulting LLC
Toby Considine (toby.considine@unc.edu), University of North Carolina at Chapel Hill

Related work:

This specification replaces or supersedes:

• Open Command and Control (OpenC2) Language Specification Version 1.1. Edited by Duncan Sparrell and Toby Considine. Latest stage: https://docs.oasis-open.org/openc2/oc2ls/v1.1/oc2ls-v1.1.html.
• Open Command and Control (OpenC2) Language Specification Version 1.0. Edited by Jason Romano and Duncan Sparrell. Latest version: https://docs.oasis-open.org/openc2/oc2ls/v1.0/oc2ls-v1.0.html.

Abstract:

Cyberattacks are increasingly sophisticated, less expensive to execute, dynamic and automated. The provision of cyber defense via statically configured products operating in isolation is untenable. Standardized interfaces, protocols and data models will facilitate the integration of the functional blocks within a system and between systems. Open Command and Control (OpenC2) is a concise and extensible language to enable machine-to-machine communications for purposes of command and control of cyber defense components, subsystems and/or systems in a manner that is agnostic of the underlying products, technologies, transport mechanisms or other aspects of the implementation. It should be understood that a language such as OpenC2 is necessary but insufficient to enable coordinated cyber responses that occur within cyber relevant time. Other aspects of coordinated cyber response such as sensing, analytics, and selecting appropriate courses of action are beyond the scope of OpenC2.

Status:

This document was last revised or approved by the OASIS Open Command and Control (OpenC2) TC on the above date. The level of approval is also listed above. Check the "Latest stage" location noted above for possible later revisions of this document. Any other numbered Versions and other technical work produced by the Technical Committee (TC) are listed at https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=openc2#technical.

TC members should send comments on this specification to the TC's email list. Others should send comments to the TC's public comment list, after subscribing to it by following the instructions at the "Send A Comment" button on the TC's web page at https://www.oasis-open.org/committees/openc2/.

This specification is provided under the Non-Assertion Mode of the OASIS IPR Policy, the mode chosen when the Technical Committee was established. For information on whether any patents have been disclosed that may be essential to implementing this specification, and any offers of patent licensing terms, please refer to the Intellectual Property Rights section of the TC's web page (https://www.oasis-open.org/committees/openc2/ipr.php).

Note that any machine-readable content (Computer Language Definitions) declared Normative for this Work Product is provided in separate plain text files. In the event of a discrepancy between any such plain text file and display content in the Work Product's prose narrative document(s), the content in the separate plain text file prevails.

Key words:

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] and [RFC8174] when, and only when, they appear in all capitals, as shown here.

Citation format:

When referencing this specification the following citation format should be used:

[OpenC2-Lang-v2.0]

Open Command and Control (OpenC2) Language Specification Version 2.0. Edited by Toby Considine and Duncan Sparrell. 16 November 2022. OASIS Committee Specification Draft 01. https://docs.oasis-open.org/openc2/oc2ls/v2.0/csd01/oc2ls-v2.0-csd01.html. Latest stage: https://docs.oasis-open.org/openc2/oc2ls/v2.0/oc2ls-v2.0.html.

Notices

Copyright © OASIS Open 2022. All Rights Reserved.

Distributed under the terms of the OASIS IPR Policy.

The name "OASIS" is a trademark of OASIS, the owner and developer of this specification, and should be used only to refer to the organization and its official outputs.

For complete copyright information please see the full Notices section in Appendix G below.

Table of Contents

• 1 Introduction
  • 1.1 Changes From Earlier Versions
  • 1.2 Glossary
    • 1.2.1 Definitions of Terms
    • 1.2.2 Acronyms and abbreviations
    • 1.2.3 Document Conventions
      • 1.2.3.1 Naming Conventions
      • 1.2.3.2 Font Colors and Style
  • 1.4 Purpose and Scope
• 2 OpenC2 Language Description
  • 2.1 OpenC2 Command
  • 2.2 OpenC2 Response
• 3 OpenC2 Language Definition
  • 3.1 Base Components and Structures
    • 3.1.1 Data Types
    • 3.1.2 Semantic Value Constraints
    • 3.1.3 Multiplicity
    • 3.1.4 Extensions
    • 3.1.5 Serialization
      • 3.1.5.1 ID and Name Serialization
  • 3.2 Message
  • 3.3 Content
    • 3.3.1 OpenC2 Command
      • 3.3.1.1 Action
      • 3.3.1.2 Target
      • 3.3.1.3 Profile
      • 3.3.1.4 Command Arguments
    • 3.3.2 OpenC2 Response
      • 3.3.2.1 Response Status Code
      • 3.3.2.2 Response Results
    • 3.3.3 OpenC2 Event
    • 3.3.4 Message Signatures
  • 3.4 Type Definitions
    • 3.4.1 Target Types
      • 3.4.1.1 Artifact
      • 3.4.1.2 Device
      • 3.4.1.3 Domain Name
      • 3.4.1.4 Email Address
      • 3.4.1.5 Features
      • 3.4.1.6 File
      • 3.4.1.7 Internationalized Domain Name
      • 3.4.1.8 Internationalized Email Address
      • 3.4.1.9 IPv4 Address Range
      • 3.4.1.10 IPv4 Connection
      • 3.4.1.11 IPv6 Address Range
      • 3.4.1.12 IPv6 Connection
      • 3.4.1.13 IRI
      • 3.4.1.14 MAC Address
      • 3.4.1.15 Process
      • 3.4.1.16 URI
    • 3.4.2 Data Types
      • 3.4.2.1 Action-Targets
      • 3.4.2.2 Command-ID
      • 3.4.2.3 Date-Time
      • 3.4.2.4 Duration
      • 3.4.2.F Feature
      • 3.4.2.6 Hashes
      • 3.4.2.7 Hostname
      • 3.4.2.8 Internationalized Hostname
      • 3.4.2.9 IPv4 Address
      • 3.4.2.10 IPv6 Address
      • 3.4.2.11 L4 Protocol
      • 3.4.2.12 Message-Type
      • 3.4.2.13 Namespace Identifier
      • 3.4.2.14 Payload
      • 3.4.2.15 Port
      • 3.4.2.16 Response-Type
      • 3.4.2.17 Targets
      • 3.4.2.18 Version
• 4 Mandatory Commands/Responses
  • 4.1 Implementation of 'query features' Command
  • 4.2 Examples of 'query features' Commands and Responses
    • 4.2.1 Example 1
    • 4.2.2 Example 2
• 5 Conformance
  • 5.1 Conformance Clause 1: Command
  • 5.2 Conformance Clause 2: Response
  • 5.3 Conformance Clause 3: Producer
  • 5.4 Conformance Clause 4: Consumer
• Appendix A. References
  • A.1 Normative References
  • A.2 Informative References
• Appendix B. Safety, Security and Privacy Considerations
• Appendix C. Examples
  • C.1 Example 1: Device Quarantine
  • C.2 Example 2: Block Connection
  • C.3 Example 3: Message Signature Processing
• Appendix D. Schema Development With JADN
• Appendix E. Revision History
• Appendix F. Acknowledgments
• Appendix G. Notices

1 Introduction

The content in this section is non-normative, except where it is marked normative.

OpenC2 is a suite of specifications that enables command and control of cyber defense systems and components. OpenC2 typically uses a request-response paradigm where a Command is encoded by a Producer (managing application) and transferred to a Consumer (managed device or virtualized function) using a secure transfer protocol, and the Consumer can respond with status and any requested information. An overview of the concepts that underlie OpenC2 and the structure of the suite of specifications can be found in the OpenC2 Architecture Specification (reference pending spec publication).

The goal of OpenC2 is to provide a language for interoperating between functional elements of cyber defense systems. This language, used in conjunction with OpenC2 Actuator Profiles and OpenC2 Transfer Specifications, allows for vendor-agnostic cybertime response to attacks.

This OpenC2 Language Specification provides the semantics for the essential elements of the language, the structure for Commands and Responses, and the schema that defines the proper syntax for the language elements that represents the Command or Response. It also describes the mechanisms for extending the capabilities of the language.

OpenC2 allows the application producing the commands to discover the set of capabilities supported by the managed devices. These capabilities permit the managing application to adjust its behavior to take advantage of the features exposed by the managed device. The capability definitions can be easily extended in a noncentralized manner, allowing standard and non-standard capabilities to be defined with semantic and syntactic rigor.

1.1 Changes From Earlier Versions

To Be Supplied.

1.2 Glossary

1.2.1 Definitions of Terms

This section is normative.

• Action: The task or activity to be performed (e.g., 'deny').

• Actuator: The Consumer that executes a Command.

• Actuator Profile: The document that defines a category of operations performed by an Actuator (e.g., 'Stateless Packet Filtering').

• Argument: A property of a Command that provides additional information on how to perform the Command, such as date/time, periodicity, duration, etc.

• Command: A Message defined by an Action-Target pair that is sent from a Producer and received by a Consumer.

• Consumer: A managed device / application that receives Commands. Note that a single device / application can have both Consumer and Producer capabilities.

• Message: A content- and transport-independent set of elements conveyed between Consumers and Producers.

• Producer: A manager application that sends Commands.

• Response: A Message from a Consumer to a Producer acknowledging a Command or returning the requested resources or status to a previously received Command.

• Specifier: A property or field that identifies a Target to some level of precision.

• Target: The object of the Action, i.e., the Action is performed on the Target (e.g., IP Address).

1.2.2 Acronyms and abbreviations

1.2.3 Document Conventions

1.2.3.1 Naming Conventions

• All property names and literals are in lowercase, except when referencing canonical names defined in another standard (e.g., literal values from an IANA registry).

• All type names begin with an uppercase character.

• Property names and type names are between 1 and 32 characters long.

• Words in property names are separated with an underscore (_), while words in type names are separated with a hyphen (-).

• "Underscore" refers to Unicode "low line", U+005F; "hyphen" refers to Unicode "hyphen-minus", U+002D.

1.2.3.2 Font Colors and Style

The following color, font and font style conventions are used in this document:

• A fixed width font is used for all type names, property names, and literals.

• Property names are in bold style – 'created_at'.

• All examples in this document are expressed in JSON. They are in fixed width font, with straight quotes, black text and a light shaded background, and 4-space indentation. JSON examples in this document are representations of JSON Objects. They should not be interpreted as string literals. The ordering of object keys is insignificant. Whitespace before or after JSON structural characters in the examples are insignificant [RFC8259].

• Parts of the example may be omitted for conciseness and clarity. These omitted parts are denoted with ellipses (...).

Example:

{
    "action": "deny",
    "target": {
        "file": {
            "hashes": {
                "sha256": "22fe72a34f006ea67d26bb7004e2b6941b5c3953d43ae7ec24d41b1a928a6973"
            }
        }
    }
}

1.4 Purpose and Scope

This OpenC2 Language Specification defines the set of components to assemble a complete command and control Message and provides a framework so that the language can be extended. To achieve this purpose, the scope of this specification includes:

1. the set of Actions and options that may be used in Commands;
2. the set of Targets and Target Specifiers;
3. a syntax that defines the structure of Commands and Responses;
4. a JSON serialization of Commands and Responses;
5. the procedures for extending the language.

The OpenC2 language assumes that the event has been detected, a decision to act has been made, the act is warranted, and the initiator and recipient of the Commands are authenticated and authorized. The OpenC2 language was designed to be agnostic of the other aspects of cyber defense implementations that realize these assumptions. The following items are beyond the scope of this specification:

1. Language elements applicable to some Actuator functions, which may be defined in individual Actuator profiles.

2. Alternate serializations of Commands and Responses.

3. The enumeration of the protocols required for transport, information assurance, sensing, analytics and other external dependencies.

2 OpenC2 Language Description

The content in this section is non-normative.

The OpenC2 language has two distinct content types: Command and Response. The Command is sent from a Producer to a Consumer and describes an Action to be performed by the Consumer on a Target. The Response is sent from a Consumer, usually back to the Producer, and is a means to provide information (such as acknowledgment, status, etc.) as a result of a Command.

2.1 OpenC2 Command

A command has four main components, two required and two optional. The required components are the Action and the Target. The optional components are command Arguments and the Profile identifier. A command can also contain an optional Command identifier, if necessary. Section 3.3.1 defines the syntax of an OpenC2 Command.

The following list summarizes the main four components of a command.

• Action (required): The task or activity to be performed.

• Target (required): The object of the action. The Action is performed on the Target. Properties of the Target, called Target Specifiers, further identify the Target to some level of precision, such as a specific Target, a list of Targets, or a class of Targets.

• Arguments (optional): Provide additional information on how the command is to be performed, such as date/time, periodicity, duration, etc.

• Profile (optional): Specifies the Actuator Profile that defines the function to be performed by the command.

The Action and Target components are required and are populated by one of the Actions in Section 3.3.1.1 and the Targets in Section 3.3.1.2. A particular Target may be further refined by the Target type definitions in Section 3.4.1. Procedures to extend the Targets are described in Section 3.1.4.

Command Arguments, if present, influence the command by providing information such as timing, periodicity, duration, or other details on what is to be executed. They can also be used to convey the need for acknowledgment or additional status information about the execution of a command. The valid Arguments defined in this specification are in Section 3.3.1.4. Procedures to extend Arguments are described in Section 3.1.4.

The Profile field, if present, specifies the profile that defines the function to be performed. A Consumer executes the command if it supports the specified profile, otherwise the command is ignored. The Profile field may be omitted and typically will not be included in implementations where the functions of the recipients are unambiguous or when a high-level effects-based command is desired and tactical decisions on how the effect is achieved is left to the recipient. If Profile is omitted and the recipient supports multiple profiles, the command will be executed in the context of each profile that supports the command's combination of action and target.

2.2 OpenC2 Response

The Response is a Message sent from the recipient of a Command. Response messages provide acknowledgment, status, results from a query, or other information. At a minimum, a Response will contain a status code to indicate the result of performing the Command. Additional status text and response fields optionally provide more detailed information that is specific to or requested by the Command. Section 3.3.2 defines the syntax of an OpenC2 Response.

3 OpenC2 Language Definition

The content in this section is normative.

3.1 Base Components and Structures

3.1.1 Data Types

OpenC2 data types are defined using an abstract notation that is independent of both their representation within applications ("API" values) and their format for transmission between applications ("serialized" values). The data types used in OpenC2 Messages are:

• API values do not affect interoperabilty, and although they must exhibit the characteristics specified above, their representation within applications is unspecified. A Python application might represent the Map type as a dict variable, a javascript application might represent it as an object literal or an ES6 Map type, and a C# application might represent it as a Dictionary or a Hashtable.

• Serialized values are critical to interoperability, and this document defines a set of serialization rules that unambiguously define how each of the above types are serialized using a human-friendly JSON format. Other serialization rules, such as for XML, machine-optimized JSON, and CBOR formats, exist but are out of scope for this document. Both the format-specific serialization rules in Section 3.1.5 and the format-agnostic type definitions in Section 3.4 are Normative.

Types defined with an ".ID" suffix (Choice.ID, Enumerated.ID, Map.ID) are equivalent to the non-suffixed types except:

1. Field definitions and API values are identified only by ID. The non-normative description may include a suggested name.

2. Serialized values of Enumerated types and keys of Choice/Map types are IDs regardless of serialization format.

OpenC2 type definitions are presented in table format. All table columns except Description are Normative. The Description column is always Non-normative.

For types without individual field definitions (Primitive types and ArrayOf), the type definition includes the name of the type being defined and the definition of that type. This table defines a type called Email-Addr that is a String that has a semantic value constraint of email:

For Structure types, the definition includes the name of the type being defined, the built-in type on which it is based, and options applicable to the type as a whole. This is followed by a table defining each of the fields in the structure. This table defines a type called Args that is a Map containing at least one field. Each of the fields has an integer Tag/ID, a Name, and a Type. Each field in this definition is optional (Multiplicity = 0..1), but per the type definition at least one must be present.

Type: Args (Map{1..*})

The field columns present in a structure definition depends on the base type:

The ID column of Array and Record types contains the ordinal position of the field, numbered sequentially starting at 1. The ID column of Choice, Enumerated, and Map types contains tags with arbitrary integer values. IDs and Names are unique within each type definition.

3.1.2 Semantic Value Constraints

Structural validation alone may be insufficient to validate that an instance meets all the requirements of an application. Semantic validation keywords specify value constraints for which an authoritative definition exists.

Usage Requirements:

• Properties identified as conforming to eui should be interpreted according to the values documented in the [IEEE Registration Authority registry].

3.1.3 Multiplicity

Property tables for types based on Array, Choice, Map and Record include a multiplicity column (#) that specifies the minimum and maximum cardinality (number of elements) of a field. As used in the Unified Modeling Language ([UML]), typical examples of multiplicity are:

When a repeatable field type is converted to a separate ArrayOf() Type, multiplicity is converted to the array size, enclosed in curly brackets, e.g.,:

A multiplicity of 0..1 denotes a single optional value of the specified type. A multiplicity of 0..n denotes a field that is either omitted or is an array containing one or more values of the specified type.

An array containing zero or more values of a specified type cannot be created implicitly using multiplicity, it must be defined explicitly as a named ArrayOf type. The named type can then be used as the type of a required field (multiplicity 1). Results are unspecified if an optional field (multiplicity 0..1) is a named ArrayOf type with a minimum length of zero.

3.1.4 Extensions

One of the main design goals of OpenC2 was extensibility. Actuator Profiles define the language extensions that are meaningful and possibly unique to the Actuator.

Each Profile has a unique name used to identify the profile document and a short reference called a namespace identifier (NSID). The NSID is a prefix used to separate types defined in one profile document from types defined in other profiles or this specification.

Example: the OASIS standard Stateless Packet Filtering profile has:

• Namespace: http://docs.oasis-open.org/openc2/oc2slpf/v1.0/oc2slpf-v1.0.md

• NSID: slpf

• Language-defined type: IPv4-Net

• Profile-defined type: slpf:Rule-ID

Example: the fictional, non-standard Superwidget Profile has:

• Namespace: http://www.acme.com/openc2/superwidget-v1.0.html

• NSID: acmesw

• Language-defined type: Device

• Profile-defined type: acmesw:Device

The list of Actions in Section 3.3.1.1 SHALL NOT be extended.

Targets, defined in Section 3.3.1.2, MAY be extended. Extended Target type names MUST be prefixed with a namespace identifier followed by a colon (":"). Extended target properties appear beneath (nested within) a profile property name.

Example: The Stateless Packet Filtering Profile supports both common and profile-specific targets:

Targets used in Consumers that support the SLPF actuator profile:

** Type: Target (Choice) **

Targets defined in the SLPF actuator profile:

** Type: slpf:AP-Target (Choice) **

In this example Command, the extended Target rule_number of type slpf:Rule-ID appears within the SLPF profile property name slpf:

{
    "action": "delete",
    "target": {
        "slpf": {
            "rule_number": 1234
        }
    }
}

Command Arguments, defined in Section 3.3.1.4, MAY also be extended using profile-defined types appearing within the profile property name.

** Type: Args (Map) **

Args defined in the SLPF actuator profile:

** Type: slpf:AP-Args (Map) **

Example: In this example Command, the extended Argument, direction of type slpf:Direction contained in type slpf:AP-Args, appears in the Stateless Packet Filtering property name slpf:

{
    "action": "deny",
    "target": {
        "ipv6_net": {...}
    },
    "args": {
        "slpf": {
            "direction": "ingress"
        }
    }
}

The Profile property of a Command, defined in Section 3.3.1.3, specifies the property name of the Actuator Profile that defines the function to be performed.

Example: In this example Command, the profile name slpf indicates that the deny ipv4_connection command is to be performed as defined by the Stateless Packet Filtering Profile.

{
    "action": "deny",
    "target": {
        "ipv4_connection": {...}
    },
    "profile": "slpf"
}

Response results, defined in Section TBD, MAY be extended using the namespace identifier as the results name, called an extended results namespace. Extended results MUST be defined within the extended results namespace.

Example: In this example Response, the Response results property, rule_number, is defined within the Stateless Packet Filtering Profile namespace, slpf.

{
    "status": 200,
    "results": {
        "slpf": {
            "rule_number": 1234
        }
    }
}

3.1.5 Serialization

OpenC2 is agnostic of any particular serialization; however, implementations MUST support JSON serialization in accordance with [RFC7493] and additional requirements specified in the following table.

JSON Serialization Requirements:

3.1.5.1 ID and Name Serialization

Instances of Enumerated types and keys for Choice and Map types are serialized as ID values except when using serialization formats intended for human consumption, where Name strings are used instead. Defining a type using ".ID" appended to the base type (e.g., Enumerated.ID, Map.ID) indicates that:

1. Type definitions and application values use only the ID. There is no corresponding name except as an optional part of the description.

2. Instances of Enumerated values and Choice/Map keys are serialized as IDs regardless of serialization format.

3.2 Message

This language specification and one or more Actuator Profiles define the content of Commands and Responses, while transfer specifications define the on-the-wire format of a Message over specific secure transport protocols. Transfer specifications are agnostic with regard to content, and content is agnostic with regard to transfer protocol. This decoupling is accomplished by defining a standard message interface used to transfer any type of content over any transfer protocol.

A message is a content- and transport-independent set of elements conveyed between Producers and Consumers. To ensure interoperability all transfer specifications must unambiguously define how the Message elements in Table 3-1 are represented within the secure transport protocol. This does not imply that all Message elements must be used in all Messages. Content, content_type, and msg_type are required in all Messages. Other Message elements are not required by this specification but may be required by other specifications. The internal representation of a Message does not affect interoperability and is therefore beyond the scope of OpenC2.

Table 3-1. Common Message Elements

As an alternative to using protocol-specific mechanisms to convey message elements, transfer specifications MAY collect all message elements into a single Message structure used as a protocol payload. The media type "application/openc2" is reserved with IANA to designate content in OpenC2 Message format. The Message structure and its media type are intended to remain stable across future versions of this specification.

Type: Message (Record)

Headers contains optional common message elements. Additional constraints on common header values may be defined. Additional headers may be defined. The "signature" field is used to contain an option digital signature to provide source authentication and integrity protections of the OpenC2 message.

Type: Headers (Map{1..*})

Body indicates the Message content format and is intended to support new types of OpenC2 Content such as command lists or bundle objects, but OpenC2 may also assign Body types for non-OpenC2 content such as STIX or CACAO objects.

Type: Body (Choice)

Type: OpenC2-Content (Choice)

Example JSON-serialized Message payload (without signature):

{
  "headers": {
    "request_id": "95ad511c-3339-4111-9c47-9156c47d37d3",
    "created": 1595268027000,
    "from": "Producer1@example.com",
    "to": ["consumer1@example.com", "consumer2@example.com", "consumer3@example.com"]
  },
  "body": {
    "openc2": {
      "request": {
        "action": "deny",
        "target": {
          "uri": "http://www.example.com" }}}}}

Usage Requirements:

• A Producer MUST include a request_id in the Message header of a Command if it requests a Response.

• The request_id of a Message SHOULD be a Version 4 UUID as specified in [RFC4122], Section 4.4.

• A Consumer MUST copy the request_id from the Message header of a Command into each Response to that Command.

3.3 Content

The purpose of this specification is to define the Action and Target portions of a Command and the common portions of a Response. The properties of the Command are defined in Section 3.3.1 and the properties of the Response are defined in Section 3.3.2.

In addition to the Action and Target, a Command has an optional Profile field. The semantics associated with Command and Response content are defined in the specified Actuator Profile.

3.3.1 OpenC2 Command

The Command defines an Action to be performed on a Target.

Type: OpenC2-Command (Record)

Usage Requirements:

• A Consumer receiving a Command with command_id absent and request_id present in the header of the Message MUST use the value of request_id as the command_id.

• If present, the args property MUST contain at least one element defined in Section 3.3.1.4.

3.3.1.1 Action

Type: Action (Enumerated)

Usage Requirements:

• Each Command MUST contain exactly one Action defined in Section 3.3.1.1.

3.3.1.2 Target

Type: Target (Choice)

Usage Requirements:

• The target field in a Command MUST contain exactly one type of Target (e.g., ipv4_net).

3.3.1.3 Profile

OpenC2 maintains an administrative document listing current, planned, and extension actuator profile information.

Type: Profile (Enumerated)

3.3.1.4 Command Arguments

Type: Args (Map{1..*})

Usage Requirements:

• start_time, stop_time, duration:

  • If none are specified, then start_time is now, stop_time is never, and duration is infinity.

    • Only two of the three are allowed on any given Command and the third is derived from the equation stop_time = start_time + duration.

    • If only start_time is specified then stop_time is never and duration is infinity.

    • If only stop_time is specified then start_time is now and duration is derived.

    • If only duration is specified then start_time is now and stop_time is derived.

• response_requested:

  • If response_requested is specified as none and the Consumer successfully executes the Command then the Consumer SHOULD NOT send a Response.

  • If response_requested is specified as none and the Consumer encounters an error then the Consumer SHOULD send a Response with a status consistent with the error detected.

  • If response_requested is specified as ack then the Consumer SHOULD send a Response acknowledging receipt of the Command: {"status": 102}.

  • If response_requested is specified as status then the Consumer SHOULD send a Response containing the current status of Command execution.

  • If response_requested is specified as complete then the Consumer SHOULD send a Response containing the status or results upon completion of Command execution.

  • If response_requested is not explicitly specified then the Consumer SHOULD respond as if complete was specified.

3.3.2 OpenC2 Response

OpenC2-Response defines the structure of a response to OpenC2-Command.

Type: OpenC2-Response (Record)

Example:

{
    "status": 200,
    "results": {
        "versions": ["1.1"]
    }
}

Usage Requirements:

• All Responses MUST contain a status.

3.3.2.1 Response Status Code

Type: Status-Code (Enumerated.ID)

3.3.2.2 Response Results

Type: Results (Map{1..*})

3.3.3 OpenC2 Event

OpenC2-Event defines the content of a one-way notification. This structure defines no common event fields, but is the point at which profile-defined event content may be added.

Type: OpenC2-Event (Map{1..*})

3.3.4 Message Signatures

Command and control mechanisms need to provide appropriate security controls protecting message content (especially authentication of command origin and protection of command integrity) so that Consumers receiving commands can proceed to execute them with confidence and Producers can have confidence that the feedback in response messages is meaningful. Digital signatures can provide both of those security properties. OpenC2 messages can be protected with digital signatures using standard mechanisms. The following RFCs specify mechanisms for digital signature protection of JSON-encoded content:

• RFC 7515: JSON Web Signature (JWS) [RFC7515]

• RFC 8785: JSON Canonicalization Scheme (JCS) [RFC8785]

• RFC 7493: The I-JSON Format [RFC7493]

OpenC2 messages SHOULD be digitally signed, unless message integrity and source authentication are provided by other mechanisms.

OpenC2 messages serialized in JSON MUST conform to the requirements of RFC 7493 to support canonicalization.

Digitally-signed OpenC2 messages serialized in JSON MUST be signed using JSON Web Signature in accordance with RFC 7515.

Digitally-signed OpenC2 messages serialized in JSON MUST use the JWS Compact Serialization method described in RFC 7515, Section 3.1.

Digitally-signed OpenC2 messages MUST use the “Detached Content” format described in Appendix F of RFC 75151, and MUST NOT include the Base64url-encoded JWS content (i.e., the encoding of the OpenC2 message content) in the transmitted message.

The JWS signature for a digitally-signed OpenC2 message SHALL be placed in the optional “signature” field of the Message structure defined in Section 3.2.

An example of creating and validating an OpenC2 message signature is contained in Annex A, Example 4.

The method for message recipients to identify and validate the appropriate public key to validate a message signature is beyond the scope of this specification. Alternative, appropriate signature mechanisms may need to be specified for serializations other than JSON.

3.4 Type Definitions

3.4.1 Target Types

3.4.1.1 Artifact

Type: Artifact (Record{1..*})

Usage Requirement:

• An "Artifact" Target MUST contain at least one property.
• media_type "Artifact" property values should be intepreted according to the values documented in the IANA Media Types registry.

3.4.1.2 Device

Type: Device (Map{1..*})

Usage Requirement:

• A "Device" Target MUST contain at least one property.

3.4.1.3 Domain Name

3.4.1.4 Email Address

3.4.1.5 Features

Usage Requirements:

• A Producer MUST NOT send a list containing more than one instance of any Feature.

• A Consumer receiving a list containing more than one instance of any Feature SHOULD behave as if the duplicate(s) were not present.

• A Producer MAY send a 'query' Command containing an empty list of features. A Producer could do this to determine if a Consumer is responding to Commands (a heartbeat command) or to generate idle traffic to keep a connection to a Consumer from being closed due to inactivity (a keep-alive command). An active Consumer could return an empty response to this command, minimizing the amount of traffic used to perform heartbeat / keep-alive functions.

3.4.1.6 File

Type: File (Map{1..*})

Usage Requirement:

• A "File" Target MUST contain at least one property.

3.4.1.7 Internationalized Domain Name

3.4.1.8 Internationalized Email Address

3.4.1.9 IPv4 Address Range

An IPv4 address range is a CIDR block per "Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan" [RFC4632] and consists of two values, an IPv4 address and a prefix.

For example, "192.168.17.0/24" is range of IP addresses with a prefix of 24 (i.e. 192.168.17.0 - 192.168.17.255).

JSON serialization of an IPv4 address range SHALL use the 'dotted/slash' textual representation of [RFC4632].

CBOR serialization of an IPv4 address range SHALL use a binary representation of the IP address and the prefix, each in their own field.

Type: IPv4-Net (Array /ipv4-net)

3.4.1.10 IPv4 Connection

Type: IPv4-Connection (Record{1..*})

Usage Requirement:

• An "IPv4-Connection" MUST contain at least one property.

3.4.1.11 IPv6 Address Range

Type: IPv6-Net (Array /ipv6-net)

3.4.1.12 IPv6 Connection

Type: IPv6-Connection (Record{1..*})

Usage Requirement:

• An "IPv6-Connection" Target MUST contain at least one property.

3.4.1.13 IRI

3.4.1.14 MAC Address

3.4.1.15 Process

Type: Process (Map{1..*})

Usage Requirement:

• A "Process" Target MUST contain at least one property.

3.4.1.16 URI

3.4.2 Data Types

3.4.2.1 Action-Targets

3.4.2.2 Command-ID

3.4.2.3 Date-Time

Usage Requirements:

• Value is the number of milliseconds since 00:00:00 UTC, 1 January 1970

3.4.2.4 Duration

Usage Requirements:

• Value is a number of milliseconds

3.4.2.F Feature

Specifies the results to be returned from a query features Command.

Type: Feature (Enumerated)

3.4.2.6 Hashes

Type: Hashes (Map{1..*})

Usage Requirement:

• A "Hashes" data type MUST contain at least one key.

3.4.2.7 Hostname

3.4.2.8 Internationalized Hostname

3.4.2.9 IPv4 Address

3.4.2.10 IPv6 Address

3.4.2.11 L4 Protocol

Value of the IPv4 "protocol" or IPv6 "next header" field in an IP packet. Recognized values for these fields are registered with IANA, according to the process defined in [RFC5237]. The table below identifies a non-exhaustive set of commonly used values.

Type: L4-Protocol (Enumerated)

Usage Requirement:

• The IPv4 Protocol field and IPv6 Next Header field are 8-bit values, therefore L4-Protocol is an enumeration from 0..255.
• Values of L4-Protocol should be interpreted as documented in [IANA_Protocols].

3.4.2.12 Message-Type

Identifies the type of Message.

Type: Message-Type (Enumerated)

3.4.2.13 Namespace Identifier

3.4.2.14 Payload

Type: Payload (Choice)

3.4.2.15 Port

3.4.2.16 Response-Type

Type: Response-Type (Enumerated)

3.4.2.17 Targets

3.4.2.18 Version

Used to report the version(s) of OpenC2 supported by Consumers.

Usage Requirement:

• A Version string MUST contain the major and minor version numbers, represented as integers seperated by a period (e.g., "1.1").

4 Mandatory Commands/Responses

The content in this section is normative, except where it is marked non-normative.

A Command consists of an Action/Target pair and associated Specifiers and Arguments. This section enumerates the allowed Commands, identifies which are required or optional to implement, and presents the associated responses.

4.1 Implementation of 'query features' Command

The 'query features' Command is REQUIRED for all Producers and Consumers implementing OpenC2. This section defines the REQUIRED and OPTIONAL aspects of the 'query features' Command and associated response for Producers and Consumers.

The 'query features' Command is REQUIRED for all Producers. The 'query features' Command MAY include one or more Features as defined in Section 3.4.2.4. The 'query features' Command MAY include the "response_requested": "complete" Argument. The 'query features' Command MUST NOT include any other Argument.

The 'query features' Command is REQUIRED for all Consumers. Consumers that receive and parse the 'query features':

• With any Argument other than "response_requested": "complete"

  • MUST NOT respond with OK/200.

  • SHOULD respond with Bad Request/400.

  • MAY respond with the 500 status code.

• With no Target Specifiers MUST respond with response code 200.

• With the "versions" Target Specifier MUST respond with status 200 and populate the versions field with a list of the OpenC2 Language Versions supported by the consumer.

• With the "profiles" Target Specifier MUST respond with status 200 and populate the profiles field with a list of profiles supported by the consumer.

• With the "pairs" Target Specifier MUST respond with status 200 and populate the pairs field with a list of action target pairs that define valid commands supported by the consumer.

• With the "rate_limit" Target Specifier populated:

  • SHOULD respond with status 200 and populate the rate_limit field with the maximum number of Commands per minute that the Consumer may support.

    • MAY respond with status 200 and with the rate_limit field unpopulated.

4.2 Examples of 'query features' Commands and Responses

This section is non-normative.

This sub-section provides examples of 'query features' Commands and Responses. The examples provided in this section are for illustrative purposes only and are not to be interpreted as operational examples for actual systems.

4.2.1 Example 1

There are no features specified in the 'query features' Command. A simple "OK" Response Message is returned.

Command:

{
    "action": "query",
    "target": {
        "features": []
    }
}

Response:

{
    "status": 200
}

4.2.2 Example 2

There are several features requested in the 'query features' Command. All requested features can be returned in a single Response Message.

Command:

{
    "action": "query",
    "target": {
        "features": ["versions", "profiles", "rate_limit"]
    }
}

Response:

{
    "status": 200,
    "results": {
        "versions": ["1.1"],
        "profiles": ["slpf", "x-lock"],
        "rate_limit": 30
    }
}

5 Conformance

This content in this section is normative.

5.1 Conformance Clause 1: Command

A conformant Command

• 5.1-1 MUST be structured in accordance with Section 3.3.1.

• 5.1-2 MUST include exactly one action property defined in accordance with Section 3.3.1.1.

• 5.1-3 MUST include exactly one target property defined in accordance with Section 3.3.1.2 or exactly one imported target property defined in accordance with Section 3.1.4.

• 5.1-4 MUST include zero or one profile property defined in accordance with Section 3.3.1.3.

• 5.1-5 MUST include zero or one args property defined in accordance with Section 3.3.1.4 or zero or one imported args property defined in accordance with Section 3.1.4.

5.2 Conformance Clause 2: Response

A conformant Response

• 5.2-1 MUST be structured in accordance with Section 3.3.2.

• 5.2-2 MUST include exactly one status property defined in accordance with Section 3.3.2.1.

5.3 Conformance Clause 3: Producer

A conformant Producer

• 5.3-1 MUST issue Commands and process Responses in accordance with Section 4.

• 5.3-2 MUST implement JSON serialization of generated Commands in accordance with [RFC7493].

• 5.3-3 MUST implement JSON serialization of received Responses in accordance with [RFC7493].

5.4 Conformance Clause 4: Consumer

A conformant Consumer

• 5.4-1 MUST process Commands and issue Responses in accordance with Section 4.

• 5.4-2 MUST implement JSON serialization of generated Responses in accordance with [RFC7493].

• 5.4-3 MUST implement JSON serialization of received Commands in accordance with [RFC7493].

Appendix A. References

This appendix contains the normative and informative references that are used in this document. Normative references are specific (identified by date of publication and/or edition number or version number) and Informative references are either specific or non-specific.

While any hyperlinks included in this appendix were valid at the time of publication, OASIS cannot guarantee their long-term validity.

A.1 Normative References

The following documents are referenced in such a way that some or all of their content constitutes requirements of this document.

[JADN-v1.0]

JSON Abstract Data Notation Version 1.0. Edited by David Kemp. 17 August 2021. OASIS Committee Specification 01. https://docs.oasis-open.org/openc2/jadn/v1.0/cs01/jadn-v1.0-cs01.html. Latest stage: https://docs.oasis-open.org/openc2/jadn/v1.0/jadn-v1.0.html.

[OpenC2-HTTPS-v1.0]

Specification for Transfer of OpenC2 Messages via HTTPS Version 1.0. Edited by David Lemire. Latest version: http://docs.oasis-open.org/openc2/open-impl-https/v1.0/open-impl-https-v1.0.html

[OpenC2-SLPF-v1.0]

Open Command and Control (OpenC2) Profile for Stateless Packet Filtering Version 1.0. Edited by Joe Brule, Duncan Sparrell, and Alex Everett. Latest version: http://docs.oasis-open.org/openc2/oc2slpf/v1.0/oc2slpf-v1.0.html

[RFC0768]

Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980, https://www.rfc-editor.org/info/rfc768.

[RFC0791]

Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, https://www.rfc-editor.org/info/rfc791.

[RFC0792]

Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, DOI 10.17487/RFC0792, September 1981, https://www.rfc-editor.org/info/rfc792.

[RFC1034]

Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, https://www.rfc-editor.org/info/rfc1034.

[RFC1123]

Braden, R., Ed., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, DOI 10.17487/RFC1123, October 1989, https://www.rfc-editor.org/info/rfc1123.

[RFC1321]

Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, DOI 10.17487/RFC1321, April 1992, https://www.rfc-editor.org/info/rfc1321.

[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.

[RFC2673]

Crawford, M., "Binary Labels in the Domain Name System", RFC 2673, August 1999, https://tools.ietf.org/html/rfc2673

[RFC3444]

Pras, A., Schoenwaelder, J., "On the Difference between Information Models and Data Models", RFC 3444, January 2003, https://tools.ietf.org/html/rfc3444.

[RFC3986]

Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, https://www.rfc-editor.org/info/rfc3986.

[RFC3987]

Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, January 2005, https://www.rfc-editor.org/info/rfc3987.

[RFC4122]

Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI 10.17487/RFC4122, July 2005, https://www.rfc-editor.org/info/rfc4122.

[RFC4291]

Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, https://www.rfc-editor.org/info/rfc4291.

[RFC4632]

Fuller, V. and T. Li, "Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 2006, https://www.rfc-editor.org/info/rfc4632.

[RFC4648]

Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, https://www.rfc-editor.org/info/rfc4648.

[RFC4960]

Stewart, R., Ed., "Stream Control Transmission Protocol", RFC 4960, DOI 10.17487/RFC4960, September 2007, https://www.rfc-editor.org/info/rfc4960.

[RFC5237]

Arkko, J. and S. Bradner, "IANA Allocation Guidelines for the Protocol Field", BCP 37, RFC 5237, DOI 10.17487/RFC5237, February 2008, https://www.rfc-editor.org/info/rfc5237.

[RFC5322]

Resnick, P., Ed., "Internet Message Format", RFC 5322, DOI 10.17487/RFC5322, October 2008, https://www.rfc-editor.org/info/rfc5322.

[RFC5890]

Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, August 2010, https://www.rfc-editor.org/info/rfc5890.

[RFC5952]

Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 Address Text Representation", RFC 5952, DOI 10.17487/RFC5952, August 2010, https://www.rfc-editor.org/info/rfc5952.

[RFC6234]

Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI 10.17487/RFC6234, May 2011, https://www.rfc-editor.org/info/rfc6234.

[RFC6335]

Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. Cheshire, "Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry", BCP 165, RFC 6335, DOI 10.17487/RFC6335, August 2011, https://www.rfc-editor.org/info/rfc6335.

[RFC6531]

Yao, J. and W. Mao, "SMTP Extension for Internationalized Email", RFC 6531, DOI 10.17487/RFC6531, February 2012, https://www.rfc-editor.org/info/rfc6531.

[RFC6838]

Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, https://www.rfc-editor.org/info/rfc6838.

[RFC7493]

Bray, T., Ed., "The I-JSON Message Format", RFC 7493, DOI 10.17487/RFC7493, March 2015, https://www.rfc-editor.org/info/rfc7493.

[RFC7515]

Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, https://www.rfc-editor.org/info/rfc7515.

[RFC8174]

Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, https://www.rfc-editor.org/info/rfc8174.

[RFC8200]

Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, https://www.rfc-editor.org/info/rfc8200.

[RFC8259]

Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, https://www.rfc-editor.org/info/rfc8259.

[RFC8785]

Rundgren, A., Jordan, B., and S. Erdtman, "JSON Canonicalization Scheme (JCS)", RFC 8785, DOI 10.17487/RFC8785, June 2020, https://www.rfc-editor.org/info/rfc8785.

[RFC9293]

Eddy, W., "Transmission Control Protocol (TCP)", RFC 9293, DOI: 10.17487/RFC9293, August 2022, https://www.rfc-editor.org/info/rfc8785.

[EUI]

"IEEE Registration Authority Guidelines for use of EUI, OUI, and CID", IEEE, August 2017, https://standards.ieee.org/content/dam/ieee-standards/standards/web/documents/tutorials/eui.pdf

[IEEE_RA]

"IEEE Registration Authority: Assignments", IEEE, August 2022, https://regauth.standards.ieee.org/standards-ra-web/pub/view.html#registries

[IANA_Protocols]

"Internet Assigned Numbers Authority Protocol Numbers", IANA, August 2022, https://www.iana.org/assignments/protocol-numbers

[IANA_Media]

"Internet Assigned Numbers Authority Media Types", IANA, August 2022, https://www.iana.org/assignments/media-types

A.2 Informative References

[RFC3552]

Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on Security Considerations", BCP 72, RFC 3552, DOI 10.17487/RFC3552, July 2003, https://www.rfc-editor.org/info/rfc3552.

[RFC8610]

Birkholz, H., Vigano, C. and Bormann, C., "Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, June 2019, https://www.rfc-editor.org/info/rfc8610

[IACD]

"What is IACD", IACD, Integrated Adaptive Cyber Defense, 3/17/2018, https://www.iacdautomate.org/

[JSON-Schema]

"JSON Schema, a vocabulary that allows you to annotate and validate JSON documents.", retrieved 9/26/2022, https://json-schema.org/

[UML]

"Unified Modeling Language", Version 2.5.1, December 2017, https://www.omg.org/spec/UML/2.5.1/About-UML/

Appendix B. Safety, Security and Privacy Considerations

(Note: OASIS strongly recommends that Technical Committees consider issues that might affect safety, security, privacy, and/or data protection in implementations of their specification and document them for implementers and adopters. For some purposes, you may find it required, e.g. if you apply for IANA registration.

While it may not be immediately obvious how your specification might make systems vulnerable to attack, most specifications, because they involve communications between systems, message formats, or system settings, open potential channels for exploit. For example, IETF [RFC3552] lists “eavesdropping, replay, message insertion, deletion, modification, and man-in-the-middle” as well as potential denial of service attacks as threats that must be considered and, if appropriate, addressed in IETF RFCs.

In addition to considering and describing foreseeable risks, this section should include guidance on how implementers and adopters can protect against these risks.

We encourage editors and TC members concerned with this subject to read Guidelines for Writing RFC Text on Security Considerations, IETF [RFC3552], for more information.

Remove this note before submitting for publication.) {TO DO}

Appendix C. Examples

The content in this section is non-normative.

C.1 Example 1: Device Quarantine

This Command would be used to quarantine a device on the network.

{
    "action": "contain",
    "target": {
        "device": {
            "device_id": "9BCE8431AC106FAA3861C7E771D20E53"
        }
    }
}

C.2 Example 2: Block Connection

This Command blocks a particular connection within the domain. The standard Actuator Profile slpf defines the extended Command Argument drop_process. The Response is a simple acknowledgment that was requested in the Command arguments.

Command:

{
    "action": "deny",
    "target": {
        "ipv4_connection": {
            "protocol": "tcp",
            "src_addr": "1.2.3.4",
            "src_port": 10996,
            "dst_addr": "198.2.3.4",
            "dst_port": 80
        }
    },
    "args": {
        "start_time": 1534775460000,
        "duration": 500,
        "response_requested": "ack",
        "slpf": {
            "drop_process": "none"
        }
    },
    "profile": "slpf"
}

Response:

{
    "status": 102
}

Editor's Note: Replace with an example that does not use "properties".

C.3 Example 3: Message Signature Processing

This example illustrates the creation and validation of a JSON message signature, as specified in 3.3.4 Message Signatures. The example in this section was prepared using the on-line JWS tool at https://mobilepki.org/jws-ct/create, using the ES256 algorithm. Base64url-encoded data and canonicalized JSON in the example are shown with line wrapping for presentation only.

C.3.1 OpenC2 Message Signature

The user embeds the signature field into the end of the payload that carries all the data required to validate authenticity and integrity of the payload. This should be done as a last step before transfer and only for the purposes of transferring the signature along with the payload. Once the payload is received the receiver should strip off the signature field from the payload, validate the signature, validate the content, and then process the contents. The process in which a particular payload will be signed will be determined by the serialization utilized.

In JSON we can accomplish this by utilizing well know [RFC8785] JSON Web Signatures (JWS) and [RFC7515] JSON Canonicalizing Scheme (JCS). Although [RFC7515] supports a variety of configurations, for this example we will use the ES256 algorithm and assume that the receiver has a mechanism to discover the correct public key. The following is a generic approach, many libraries in multiple programming languages exist that can alter/simplify this process.

C.3.2 OpenC2 Signing Operation (JSON)

1. Generate the OpenC2 JSON object as described in the OpenC2 Language Specification.

{
  "headers": {
    "request_id": "95ad511c-3339-4111-9c47-9156c47d37d3",
    "created": 1595268027000,
    "from": "Producer1@example.com",
    "to": ["consumer1@example.com", "consumer2@example.com", "consumer3@example.com"]
  },
  "body": {
    "openc2": {
      "request": {
        "action": "deny",
        "target": {
          "uri": "http://www.example.com"
                }
            }
        }
    }
}

2. Canonicalize JSON Data using the process described in RFC8785.

{"body":{"openc2":{"request":{"action":"deny",
"target":{"uri":"http://www.example.com"}}}},
"headers":{"created":1595268027000,
"from":"Producer1@example.com",
"request_id":"95ad511c-3339-4111-9c47-9156c47d37d3",
"to":["consumer1@example.com","consumer2@example.com","consumer3@example.com"]}}

3. Create a JWS using the process described in RFC7515.

A. Develop a protected header for the type of signature that will be used.

{
    "alg": "ES256",
    "kid": "Producer1@example.com"
}

B. Base64 encode the protected header.

eyJhbGciOiJFUzI1NiIsImtpZCI6IlByb2R1Y2VyMUBleGFtcGxlLmNvbSJ9

C. Base64 encode our canonicalize JSON object from step 2 to create the JWS payload.

eyJib2R5Ijp7Im9wZW5jMiI6eyJyZXF1ZXN0Ijp7ImFjdGlvbiI6ImRlbnkiLCJ0YXJnZXQiOnsidXJpIjoiaHR0cDovL3d3dy5leGFtcGxlLmNvbSJ9fX19LCJoZWFkZXJzIjp7ImNyZWF0ZWQiOjE1OTUyNjgwMjcwMDAsImZyb20iOiJQcm9kdWNlcjFAZXhhbXBsZS5jb20iLCJyZXF1ZXN0X2lkIjoiOTVhZDUxMWMtMzMzOS00MTExLTljNDctOTE1NmM0N2QzN2QzIiwidG8iOlsiY29uc3VtZXIxQGV4YW1wbGUuY29tIiwiY29uc3VtZXIyQGV4YW1wbGUuY29tIiwiY29uc3VtZXIzQGV4YW1wbGUuY29tIl19fQ

D. Concatenate the JWS protected header and the JWS payload using with a period character to create our signing input.

eyJhbGciOiJSUzI1NiIsImtpZCI6IlByb2R1Y2VyMUBleGFtcGxlLmNvbSJ9 . eyJib2R5Ijp7Im9wZW5jMiI6eyJyZXF1ZXN0Ijp7ImFjdGlvbiI6ImRlbnkiLCJ0YXJnZXQiOnsidXJpIjoiaHR0cDovL3d3dy5leGFtcGxlLmNvbSJ9fX19LCJoZWFkZXJzIjp7ImNyZWF0ZWQiOjE1OTUyNjgwMjcwMDAsImZyb20iOiJQcm9kdWNlcjFAZXhhbXBsZS5jb20iLCJyZXF1ZXN0X2lkIjoiOTVhZDUxMWMtMzMzOS00MTExLTljNDctOTE1NmM0N2QzN2QzIiwidG8iOlsiY29uc3VtZXIxQGV4YW1wbGUuY29tIiwiY29uc3VtZXIyQGV4YW1wbGUuY29tIiwiY29uc3VtZXIzQGV4YW1wbGUuY29tIl19fQ

E. Utilize the signing input, ES256 algorithm, and the sender's private key to calculate the signature.

-----BEGIN PRIVATE KEY-----
MIGTAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBHkwdwIBAQQg6XxMFXhcYT5QN9w5TIg2aSKsbcj+
pj4BnZkK7ZOt4B+gCgYIKoZIzj0DAQehRANCAAToErGm3Lxwj57EPMKSH6ChTp1ercxtxjRx3Uto
DGI2tZgm3L1M5uOI9y7dm+QT8kJaEPdbX9g9lfoM3lMVmlHY
-----END PRIVATE KEY-----

Signature value:

PsJmWi726O_HTK-Svp_fIlZ8FdIH6jeWslM9F5Qrv1gFqv7EwREGOUU4rd53hHS59Yr0Zapk4Ryv9XFmPxHObw

F. Normally at this point we would concatenate all 3 with a period character to create our JWS. However, in order to reduce overhead, we will be using detached version of JWS. To do this we replace the JWS payload portion with an empty string.

eyJhbGciOiJSUzI1NiIsImtpZCI6IlByb2R1Y2VyMUBleGFtcGxlLmNvbSJ9..PsJmWi726O_HTK-Svp_fIlZ8FdIH6jeWslM9F5Qrv1gFqv7EwREGOUU4rd53hHS59Yr0Zapk4Ryv9XFmPxHObw

4. Add the detached JWS back into the original OpenC2 JSON object under the property “signature”.

{
  "headers": {
    "request_id": "95ad511c-3339-4111-9c47-9156c47d37d3",
    "created": 1595268027000,
    "from": "Producer1@example.com",
    "to": ["consumer1@example.com", "consumer2@example.com", "consumer3@example.com"]
  },
  "body": {
    "openc2": {
      "request": {
        "action": "deny",
        "target": {
          "uri": "http://www.example.com"
                }
            }
        }
    }
    "signature": "eyJhbGciOiJSUzI1NiIsImtpZCI6IlByb2R1Y2VyMUBleGFtcGxlLmNvbSJ9..PsJmWi726O_HTK-Svp_fIlZ8FdIH6jeWslM9F5Qrv1gFqv7EwREGOUU4rd53hHS59Yr0Zapk4Ryv9XFmPxHObw"
}

5. Serialize the signed OpenC2 JSON object and send to recipient(s).

C.3.3 OpenC2 Signing Validation (JSON)

1. Parse the received OpenC2 JSON object and separate out the signature. This should yield:

A. Original OpenC2 JSON object.

{
  "headers": {
    "request_id": "95ad511c-3339-4111-9c47-9156c47d37d3",
    "created": 1595268027000,
    "from": "Producer1@example.com",
    "to": ["consumer1@example.com", "consumer2@example.com", "consumer3@example.com"]
  },
  "body": {
    "openc2": {
      "request": {
        "action": "deny",
        "target": {
          "uri": "http://www.example.com"
                }
            }
        }
    }
}

B. Original Detached JWS.

eyJhbGciOiJSUzI1NiIsImtpZCI6IlByb2R1Y2VyMUBleGFtcGxlLmNvbSJ9..PsJmWi726O_HTK-Svp_fIlZ8FdIH6jeWslM9F5Qrv1gFqv7EwREGOUU4rd53hHS59Yr0Zapk4Ryv9XFmPxHObw

2. Canonicalize JSON Data using the process described in RFC8785.

{"body":{"openc2":{"request":{"action":"deny","target":{"uri":"http://www.example.com"}}}},
"headers":{"created":1595268027000,"from":"Producer1@example.com","request_id":"95ad511c-3339-4111-9c47-9156c47d37d3",
"to":["consumer1@example.com","consumer2@example.com","consumer3@example.com"]}}

3. Create a JWS using the process described in RFC7515.

A. Base64 encode our canonicalize JSON object from step 2 to create the JWS payload

eyJib2R5Ijp7Im9wZW5jMiI6eyJyZXF1ZXN0Ijp7ImFjdGlvbiI6ImRlbnkiLCJ0YXJnZXQiOnsidXJpIjoiaHR0cDovL3d3dy5leGFtcGxlLmNvbSJ9fX19LCJoZWFkZXJzIjp7ImNyZWF0ZWQiOjE1OTUyNjgwMjcwMDAsImZyb20iOiJQcm9kdWNlcjFAZXhhbXBsZS5jb20iLCJyZXF1ZXN0X2lkIjoiOTVhZDUxMWMtMzMzOS00MTExLTljNDctOTE1NmM0N2QzN2QzIiwidG8iOlsiY29uc3VtZXIxQGV4YW1wbGUuY29tIiwiY29uc3VtZXIyQGV4YW1wbGUuY29tIiwiY29uc3VtZXIzQGV4YW1wbGUuY29tIl19fQ

B. Overwrite the detached JWS empty string between the first and second period characters with the JWS payload to create a standard, non-detached, JWS.

eyJhbGciOiJSUzI1NiIsImtpZCI6IlByb2R1Y2VyMUBleGFtcGxlLmNvbSJ9.eyJib2R5Ijp7Im9wZW5jMiI6eyJyZXF1ZXN0Ijp7ImFjdGlvbiI6ImRlbnkiLCJ0YXJnZXQiOnsidXJpIjoiaHR0cDovL3d3dy5leGFtcGxlLmNvbSJ9fX19LCJoZWFkZXJzIjp7ImNyZWF0ZWQiOjE1OTUyNjgwMjcwMDAsImZyb20iOiJQcm9kdWNlcjFAZXhhbXBsZS5jb20iLCJyZXF1ZXN0X2lkIjoiOTVhZDUxMWMtMzMzOS00MTExLTljNDctOTE1NmM0N2QzN2QzIiwidG8iOlsiY29uc3VtZXIxQGV4YW1wbGUuY29tIiwiY29uc3VtZXIyQGV4YW1wbGUuY29tIiwiY29uc3VtZXIzQGV4YW1wbGUuY29tIl19fQ.PsJmWi726O_HTK-Svp_fIlZ8FdIH6jeWslM9F5Qrv1gFqv7EwREGOUU4rd53hHS59Yr0Zapk4Ryv9XFmPxHObw

4. Follow the JWS validation process described in RFC7515.

A. Save the JWS signing Input (which is the initial substring of the JWS up until but not including the second period character)

eyJhbGciOiJSUzI1NiIsImtpZCI6IlByb2R1Y2VyMUBleGFtcGxlLmNvbSJ9.eyJib2R5Ijp7Im9wZW5jMiI6eyJyZXF1ZXN0Ijp7ImFjdGlvbiI6ImRlbnkiLCJ0YXJnZXQiOnsidXJpIjoiaHR0cDovL3d3dy5leGFtcGxlLmNvbSJ9fX19LCJoZWFkZXJzIjp7ImNyZWF0ZWQiOjE1OTUyNjgwMjcwMDAsImZyb20iOiJQcm9kdWNlcjFAZXhhbXBsZS5jb20iLCJyZXF1ZXN0X2lkIjoiOTVhZDUxMWMtMzMzOS00MTExLTljNDctOTE1NmM0N2QzN2QzIiwidG8iOlsiY29uc3VtZXIxQGV4YW1wbGUuY29tIiwiY29uc3VtZXIyQGV4YW1wbGUuY29tIiwiY29uc3VtZXIzQGV4YW1wbGUuY29tIl19fQ

B. Save the JWS signature (Which is the string following but not including the second period character)

PsJmWi726O_HTK-Svp_fIlZ8FdIH6jeWslM9F5Qrv1gFqv7EwREGOUU4rd53hHS59Yr0Zapk4Ryv9XFmPxHObw

C. Pass the public key, the JWS signature, and the JWS signing input to an ES256 signature verifier. Expect a Boolean response.

-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE6BKxpty8cI+exDzCkh+goU6dXq3MbcY0cd1LaAxi
NrWYJty9TObjiPcu3ZvkE/JCWhD3W1/YPZX6DN5TFZpR2A==
-----END PUBLIC KEY-----

Appendix D. Schema Development With JADN

The content in this section is non-normative.

This appendix provides a brief overview of the JSON Abstract Data Notation (JADN) [JADN-v1.0] information modeling (IM) language and its application to rigorously specifying the OpenC2 language. Unless explicitly labeled otherwise, section references in this appendix are to sections of the JADN specification, rather than this Language Specification.

D.1 JADN Overview

The abstract of the OASIS Committee Specification for JADN describes it as follows:

JSON Abstract Data Notation (JADN) is a UML-based information modeling language that defines data structure independently of data format.

As the specification explains (section 1): RFC 3444, "Information Models and Data Models", notes that the main purpose of an information model is to model objects at a conceptual level, independent of specific implementations or protocols used to transport the data. JADN provides a tool for developing information models, which can be used to define and generate physical data models, validate information instances, and enable lossless translation across data formats.

A JADN specification consists of:

• type definitions that comprise the information model, and
• serialization rules that define how information instances are represented as data.

The model is documented using a compact and expressive interface definition language, property tables, or entity relationship diagrams, easing integration with existing design processes and architecture tools.

JADN defines a set of base types that includes five "primitives" (e.g., boolean, string), and seven complex types (e.g., array, map, record). JADN type definitions have a fixed structure designed to be easily describable, easily processed, stable, and extensible. Every definition in a JADN document is described in terms of five elements (JADN specification section 3.1):

1. TypeName: a string containing the name of the type being defined
2. BaseType: a choice from the JADN predefined types (Table 3-1) of the type being defined
3. TypeOptions: an array of zero or more TypeOption (Section 3.2.1) applicable to BaseType
4. TypeDescription: a string containing a non-normative comment
5. Fields: an array of Item or Field definitions

From this starting point JADN enables creation of a rich information model readily expressed in any of several representations. Section 3.2 describes an extensive set of options (e.g., semantic validation, size and value constraints, multiplicity constraints) that provide the means to define a wide variety of information types in a representation-independent manner.

As an information modeling language, JADN supports only two kinds of relationships: "contain" and "reference". A JADN information model is a set of type definitions, where each definition may be basic or structured. Each field in a structured type may be associated with another model-defined type, and the set of associations between types forms a directed graph. Each association is either a container or a reference, and the direction of each edge is toward the contained or referenced type.

The native format of JADN is JSON, but JADN content can be represented in others ways that are more useful for documentation. The JADN Specification identifies three formats (Section 5) in addition to the native format:

• JADN Interface Definition Language (JIDL)
• Table Style
• Entity Relationship Diagrams

Automated tooling makes it straightforward to translate among all four of these formats. Table style presentation is often used in specifications (e.g., as property tables such as are found in the body of this specification). Entity relationship diagrams are helpful for visualization of an information model. The JIDL format, a simple text structure, is easy to edit, making it a good format for the initial creation of a JADN model.

D.2 Deriving Other Schemas and Serializations

Once the information model is developed, its use in applications requires serialization and deserialization of the information in some specific format to permit transmisssion or storage of the data corresponding to the model. Serialization is the process for converting application information, regardless of its internal representation, into a form that can be transmitted (i.e., into a "document"). JADN information models can be translated into a number of schema formats, such as [JSON schema] or CDDL [RFC8610], or can be used directly as a format-independent schema language. As with translation among JADN representations, the use of automated tools to create schemas ensures the schemas are an accurate, repeatable representation of the JADN information model.

Converting an information model to a data model means applying serialization rules for each base type that produce physical data in the desired format. The JADN specification defines serialization rules for four different representations of an information mode (Section 4):

In addition, the specification identifies the constraints that must be satisifed to define how a JADN IM is represented in other serializations (Section 4). Because each serialization represents the same information model, translation between serialization formats is simplified.

D.3 JADN Example: OpenC2 Subset

This section provide a brief example of a JADN information model, using data types from OpenC2.

D.3.1 Basic and Complex Data Types

This example illustrates the use of basic and complex types to describe a network connection. A 5-tuple is a common means of representing a TCP or UDP session, recording the source and destination IP addresses and ports, and identifying the Layer 4 protocol in use. The corresponding OpenC2 target type is called an IPv4-Connection (see section 3.4.1.10 of this specification). A group of basic (i.e., binary, integer) and complex (i.e., record, array, enumeration) types and their use in the definition of an IPv4 Connection information model are represented in JIDL as follows:

// An IPv4 address is a binary value representing a 32-bit integer

IPv4-Addr = Binary /ipv4-addr                     // 32 bit IPv4 address as defined in [[RFC0791]](#rfc0791)


// the IPv4-Connection type is a record

IPv4-Connection = Record{1..*}                    // 5-tuple that specifies a tcp/ip connection
   1 src_addr         IPv4-Net optional           // IPv4 source address range
   2 src_port         Port optional               // Source service per [RFC6335]
   3 dst_addr         IPv4-Net optional           // IPv4 destination address range
   4 dst_port         Port optional               // Destination service per [RFC6335]
   5 protocol         L4-Protocol optional        // Layer 4 protocol (e.g., TCP) - see [Section 3.4.2.10](#34210-l4-protocol)


// the IPv4-Net type is an array used to represent a CIDR block

IPv4-Net = Array /ipv4-net                        // IPv4 address and prefix length
   1  IPv4-Addr                                   // ipv4_addr:: IPv4 address as defined in [RFC0791]
   2  Integer optional                            // prefix_length:: CIDR prefix-length. If omitted, refers to a single host address.


// L4-Protocol is an 8-bit value therefore L4-Protocol is an enumeration from 0..255.
// The interpretation of this value is handled through an external registry
// See the usage requirements in Section 3.4.2.11, which also contains the following
// commonly-used example values for the field.

L4-Protocol = Enumerated                          // Value of the protocol (IPv4) or next header (IPv6) field in an IP packet. Any IANA value, [[RFC5237]](#rfc5237)
   1 icmp                                         // Internet Control Message Protocol - [RFC0792]
   6 tcp                                          // Transmission Control Protocol - [RFC0793]
  17 udp                                          // User Datagram Protocol - [RFC0768]
 132 sctp                                         // Stream Control Transmission Protocol - [RFC4960]


// Port is a 16-bit integer

Port = Integer{0..65535}                          // Transport Protocol Port Number, [RFC6335]

The equivalent property table representations can be found in the respective section of this specification for each type (ordered as above):

• 3.4.2.9: IPv4-Addr
• 3.4.1.10: IPv4-Connection
• 3.4.1.9: IPv4-Net
• 3.4.2.11: L4-Protocol
• 3.4.2.15: Port

The example above also makes use of a pair of JADN semantic validation keywords: "ipv4-addr" and "ipv4-net". These keywords specify validation requirements for the data types where they are used (see section 3.2.1.5 of the JADN specification). For example, "ipv4-addr" is used to force the representation of a binary address in the commonly used "dotted quad" format.

D.3.2 JADN Representation

This section shows the JADN representation of the types defined using JIDL in the preceding section.

["IPv4-Addr", "Binary", ["/ipv4-addr"], "32 bit IPv4 address as defined in [RFC0791]"],

["IPv4-Connection", "Record", ["{1"], "5-tuple that specifies a tcp/ip connection", [
    [1, "src_addr", "IPv4-Net", ["[0"], "IPv4 source address range"],
    [2, "src_port", "Port", ["[0"], "Source service per [RFC6335],
    [3, "dst_addr", "IPv4-Net", ["[0"], "IPv4 destination address range"],
    [4, "dst_port", "Port", ["[0"], "Destination service per [RFC6335],
    [5, "protocol", "L4-Protocol", ["[0"], "Layer 4 protocol (e.g., TCP) - see Section 3.4.2.10"]
]],

["IPv4-Net", "Array", ["/ipv4-net"], "IPv4 address and prefix length", [
    [1, "ipv4_addr", "IPv4-Addr", [], "IPv4 address as defined in [RFC0791],
    [2, "prefix_length", "Integer", ["[0"], "CIDR prefix-length. If omitted, refers to a single host address."]
]],

["L4-Protocol", "Enumerated", [], "Value of the protocol (IPv4) or next header (IPv6) field in an IP packet. Any IANA value, [[RFC5237]](#rfc5237)", [
    [1, "icmp", "Internet Control Message Protocol - [RFC0792],
    [6, "tcp", "Transmission Control Protocol - [RFC0793],
    [17, "udp", "User Datagram Protocol - [RFC0768],
    [132, "sctp", "Stream Control Transmission Protocol - [RFC4960]"]
]]

["Port", "Integer", ["{0", "}65535"], "Transport Protocol Port Number, [RFC6335]"]

D.3.3 Translation To JSON Schema

TBD: JADN translation to JSON schema

D.4 Additional Information

JADN supports organizing features to facilitate the creation and management of JADN schemas. In particular:

• Schemas can be broken up into a collection of packages. A package is a collection of type definitions along with information about the package, such as the namespace the package defines, its version, and other administrative and technical information.
• The use of namespaces enables one packages toi reference type definitions from other packages.

TBD: Reference to, description of OpenC2 JADN schema external artifact

Appendix E. Revision History

Appendix F. Acknowledgments

The content in this section is non-normative.

The following individuals have participated in the creation of this specification and are gratefully acknowledged:

OpenC2 TC Members:

Appendix G. Notices

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