Open Command and Control (OpenC2) Language Specification Version 2.0

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)

Previous stage:


Latest stage:

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

Technical Committee:

OASIS Open Command and Control (OpenC2) TC


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


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

This specification replaces or supersedes:


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.


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:


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.


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

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.

1.2.2 Acronyms and abbreviations

Acronym Description
API Application Programming Interface
ASCII American Standard Code for Information Interchange
BCP Best Current Practice
CBOR Concise Binary Object Representation
CIDR Classless Inter-Domain Routing
CoAP Constrained Application Protocol
DOI Digital Object Identifier
EUI Extended Unique Identifier
HTTP Hyper Text Transfer Protocol
HTTPS Hyper Text Transfer Protocol Secure
IACD Integrated Adaptive Cyber Defense
IANA Internet Assigned Numbers Authority
ICMP Internet Control Message Protocol
ID Identifier
IP Internet Protocol
IPR Intellectual Property Rights
JSON JavaScript Object Notation
MAC Media Access Control
MD5 Message Digest
MQTT Message Queuing Telemetry Transfer
OASIS Organization for the Advancement of Structured Information Standards
OODA Observe-Orient-Decide-Act
OpenC2 Open Command and Control
OpenDXL Open Data eXchange Layer
PDF Portable Document Format
RFC Request for Comment
SCTP Stream Control Transmission Protocol
SHA Security Hash Algorithm
SLPF StateLess Packet Filtering
STD Standard
TC Technical Committee
TCP Transmission Control Protocol
UDP User Datagram Control Protocol
UML Unified Modeling Language
URI Uniform Resource Identifier
UTC Coordinated Universal Time
UUID Universally Unique IDentifier
XML eXtensibel Markup Language

1.2.3 Document Conventions Naming Conventions Font Colors and Style

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


    "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.

The Action and Target components are required and are populated by one of the Actions in Section and the Targets in Section 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 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:

Type Description
Primitive Types
Any Anything, used to designate fields with an unspecified value.
Binary A sequence of octets. Length is the number of octets.
Boolean An element with one of two values: true and false.
Integer A whole number.
Number A real number.
Null Nothing, used to designate fields with no value.
String A sequence of characters, each of which has a Unicode codepoint. Length is the number of characters.
Array An ordered list of unnamed fields with positionally-defined semantics. Each field has a position, label, and type.
ArrayOf(vtype) An ordered list of fields with the same semantics. Each field has a position and type vtype.
Choice One field selected from a set of named fields. The API value has a name and a type.
Choice.ID One field selected from a set of fields. The API value has an id and a type.
Enumerated A set of named integral constants. The API value is a name.
Enumerated.ID A set of unnamed integral constants. The API value is an id.
Map An unordered map from a set of specified keys to values with semantics bound to each key. Each field has an id, name and type.
Map.ID An unordered set of fields. The API value of each field has an id, label, and type.
MapOf(ktype, vtype) An unordered set of keys to values with the same semantics. Each key has key type ktype and is mapped to value type vtype.
Record An ordered map from a list of keys with positions to values with positionally-defined semantics. Each key has a position and name, and is mapped to a type. Represents a row in a spreadsheet or database table.

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:

Type Name Type Definition Description
Email-Addr String (email) Email address

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..*})

ID Name Type # Description
1 start_time Date-Time 0..1 The specific date/time to initiate the action
2 stop_time Date-Time 0..1 The specific date/time to terminate the action
3 duration Duration 0..1 The length of time for an action to be in effect

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

Base Type Field Definition Columns
Enumerated.ID ID, Description
Enumerated ID, Name, Description
Array, Choice.ID, Map.ID ID, Type, Multiplicity (#), Description
Choice, Map, Record ID, Name, Type, Multiplicity (#), Description

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.

Keyword Applies to Type Constraint
email String Value must be an email address as defined in [RFC5322], Section 3.4.1
eui Binary Value must be an EUI-48 or EUI-64 as defined in [EUI]
hostname String Value must be a hostname as defined in [RFC1034], Section 3.1
idn-email String Value must be an internationalized email address as defined in [RFC6531]
idn-hostname String Value must be an internationalized hostname as defined in [RFC5890], Section
iri String Value must be an Internationalized Resource Identifier (IRI) as defined in [RFC3987]
uri String Value must be a Uniform Resource Identifier (URI) as defined in [RFC3986]

Usage Requirements:

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:

Multiplicity Description Keywords
1 Exactly one instance Required
0..1 No instances or one instance Optional
1..* At least one instance Required, Repeatable
0..* Zero or more instances Optional, Repeatable
m..n At least m but no more than n instances Required, Repeatable

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.,:

Type Name Type Definition Description
Features ArrayOf(Feature){0..10} An array of zero to ten names used to query an actuator for its supported capabilities.

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:

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

The list of Actions in Section SHALL NOT be extended.

Targets, defined in Section, 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) **

ID Name Type Description
13 ipv4_net IPv4-Net Targets defined in the LS
1024 slpf slpf:AP-Target Targets defined in the SLPF AP

Targets defined in the SLPF actuator profile:

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

ID Name Type Description
1 rule_number slpf:Rule-ID

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, MAY also be extended using profile-defined types appearing within the profile property name.

** Type: Args (Map) **

ID Name Type Description
1 start_time Date-Time Args defined in the LS
1024 slpf slpf:AP-Args Args defined in the SLPF AP

Args defined in the SLPF actuator profile:

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

ID Name Type Description
3 direction slpf:Direction

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, 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:

OpenC2 Data Type JSON Serialization Requirement
Binary JSON string containing Base64url encoding of the binary value as defined in [RFC4648], Section 5.
Binary /x JSON string containing Base16 (hex) encoding of a binary value as defined in [RFC4648], Section 8. Note that the Base16 alphabet does not include lower-case letters.
IPv4-Addr JSON string containing the "dotted-quad" representation of an IPv4 address as specified in [RFC2673], Section 3.2.
IPv6-Addr JSON string containing the text representation of an IPv6 address as specified in [RFC5952], Section 4.
MAC-Addr JSON string containing the text representation of a MAC Address in colon hexadecimal format as defined in [EUI].
Boolean JSON true or false
Integer JSON number
Number JSON number
Null JSON null
String JSON string
Array JSON array
Array /ipv4-net JSON string containing the text representation of an IPv4 address range as specified in [RFC4632], Section 3.1.
Array /ipv6-net JSON string containing the text representation of an IPv6 address range as specified in [RFC4291], Section 2.3.
ArrayOf JSON array
Choice JSON object with one member. Member key is the field name.
Choice.ID JSON object with one member. Member key is the integer field id converted to string.
Enumerated JSON string
Enumerated.ID JSON integer
Map JSON object. Member keys are field names.
Map.ID JSON object. Member keys are integer field ids converted to strings.
MapOf JSON object. Member keys are as defined in the specified key type.
Record JSON object. Member keys are field names. 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
Name Type Description
content Message body as specified by content_type and msg_type.
content_type String Media Type that identifies the format of the content, including major version. Incompatible content formats must have different content_types. Content_type application/openc2 identifies content defined by OpenC2 language specification versions 1.x, i.e., all versions that are compatible with version 1.1.
msg_type Message-Type The type of OpenC2 Message.
status Status-Code Populated with a numeric status code in Responses.
request_id String A unique identifier created by the Producer and copied by Consumer into all Responses, in order to support reference to a particular Command, transaction, or event chain.
created Date-Time Creation date/time of the content.
from String Authenticated identifier of the creator of or authority for execution of a message.
to ArrayOf(String) Authenticated identifier(s) of the authorized recipient(s) of a message.

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)

ID Name Type # Description
1 headers Headers 0..1
2 body Body 1
3 signature String 0..1

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..*})

ID Name Type # Description
1 request_id String 0..1
2 created ls:Date-Time 0..1
3 from String 0..1
4 to String 0..*

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)

ID Name Type # Description
1 openc2 OpenC2-Content 1

Type: OpenC2-Content (Choice)

ID Name Type # Description
1 request OpenC2-Command 1
2 response OpenC2-Response 1
3 notification OpenC2-Event 1

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:

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)

ID Name Type # Description
1 action Action 1 The task or activity to be performed (i.e., the 'verb').
2 target Target 1 The object of the Action. The Action is performed on the Target.
3 args Args 0..1 Additional information that applies to the Command.
4 profile Profile 0..1 The actuator profile defining the function to be performed by the Command.
5 command_id Command-ID 0..1 An identifier of this Command.

Usage Requirements: Action

Type: Action (Enumerated)

ID Name Description
1 scan Systematic examination of some aspect of the entity or its environment.
2 locate Find an object physically, logically, functionally, or by organization.
3 query Initiate a request for information.
6 deny Prevent a certain event or action from completion, such as preventing a flow from reaching a destination or preventing access.
7 contain Isolate a file, process, or entity so that it cannot modify or access assets or processes.
8 allow Permit access to or execution of a Target.
9 start Initiate a process, application, system, or activity.
10 stop Halt a system or end an activity.
11 restart Stop then start a system or an activity.
14 cancel Invalidate a previously issued Action.
15 set Change a value, configuration, or state of a managed entity.
16 update Instruct a component to retrieve, install, process, and operate in accordance with a software update, reconfiguration, or other update.
18 redirect Change the flow of traffic to a destination other than its original destination.
19 create Add a new entity of a known type (e.g., data, files, directories).
20 delete Remove an entity (e.g., data, files, flows).
22 detonate Execute and observe the behavior of a Target (e.g., file, hyperlink) in an isolated environment.
23 restore Return a system to a previously known state.
28 copy Duplicate an object, file, data flow, or artifact.
30 investigate Task the recipient to aggregate and report information as it pertains to a security event or incident.
32 remediate Task the recipient to eliminate a vulnerability or attack point.

Usage Requirements: Target

Type: Target (Choice)

ID Name Type # Description
1 artifact Artifact 1 An array of bytes representing a file-like object or a link to that object.
2 command Command-ID 1 A reference to a previously issued Command.
3 device Device 1 The properties of a hardware device.
7 domain_name Domain-Name 1 A network domain name.
8 email_addr Email-Addr 1 A single email address.
9 features Features 1 A set of items used with the query Action to determine an Actuator's capabilities.
10 file File 1 Properties of a file.
11 idn_domain_name IDN-Domain-Name 1 An internationalized domain name.
12 idn_email_addr IDN-Email-Addr 1 A single internationalized email address.
13 ipv4_net IPv4-Net 1 An IPv4 address range including CIDR prefix length.
14 ipv6_net IPv6-Net 1 An IPv6 address range including prefix length.
15 ipv4_connection IPv4-Connection 1 A 5-tuple of source and destination IPv4 address ranges, source and destination ports, and protocol.
16 ipv6_connection IPv6-Connection 1 A 5-tuple of source and destination IPv6 address ranges, source and destination ports, and protocol.
20 iri IRI 1 An internationalized resource identifier (IRI).
17 mac_addr MAC-Addr 1 A Media Access Control (MAC) address - EUI-48 or EUI-64 as defined in [EUI].
18 process Process 1 Common properties of an instance of a computer program as executed on an operating system.
19 uri URI 1 A uniform resource identifier (URI).

Usage Requirements: Profile

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

Type: Profile (Enumerated)

ID Name Description
1024 slpf Stateless Packet Filtering
1025 sfpf Stateful Packet Filtering
1026 sbom Software Bill of Materials
1027 er Endpoint Response
1028 hop Honeypot Control
1029 av Anti-Virus
1030 ids Intrusion Detection System
1031 log Logging Control
1032 swup Software Update
1034 pf Packet Filtering
1035 pac Security Posture Attribute Collection Command Arguments

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

ID Name Type # Description
1 start_time Date-Time 0..1 The specific date/time to initiate the Command
2 stop_time Date-Time 0..1 The specific date/time to terminate the Command
3 duration Duration 0..1 The length of time for a Command to be in effect
4 response_requested Response-Type 0..1 The type of Response required for the Command: none, ack, status, complete.
5 comment String 0..1 A human-readable note to annotate or provide information regarding the action.

Usage Requirements:

3.3.2 OpenC2 Response

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

Type: OpenC2-Response (Record)

ID Name Type # Description
1 status Status-Code 1 An integer status code.
2 status_text String 0..1 A free-form human-readable description of the Response status.
3 results Results 0..1 Map of key:value pairs that contain additional results based on the invoking Command.


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

Usage Requirements: Response Status Code

Type: Status-Code (Enumerated.ID)

ID Description
102 Processing - an interim Response used to inform the Producer that the Consumer has accepted the Command but has not yet completed it.
200 OK - the Command has succeeded.
400 Bad Request - the Consumer cannot process the Command due to something that is perceived to be a Producer error (e.g., malformed Command syntax).
401 Unauthorized - the Command Message lacks valid authentication credentials for the target resource or authorization has been refused for the submitted credentials.
403 Forbidden - the Consumer understood the Command but refuses to authorize it.
404 Not Found - the Consumer has not found anything matching the Command.
500 Internal Error - the Consumer encountered an unexpected condition that prevented it from performing the Command.
501 Not Implemented - the Consumer does not support the functionality required to perform the Command.
503 Service Unavailable - the Consumer is currently unable to perform the Command due to a temporary overloading or maintenance of the Consumer. Response Results

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

ID Name Type # Description
1 versions Version unique 0..* List of OpenC2 language versions supported by this Consumer
2 profiles Nsid 0..* List of profiles supported by this Consumer
3 pairs Action-Targets 0..1 List of targets applicable to each supported Action
4 rate_limit Number{0..*} 0..1 Maximum number of requests per minute supported by design or policy

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..*})

ID Name Type # Description

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:

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 Artifact

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

ID Name Type # Description
1 media_type String 0..1 Media type description formatted as specified in [RFC6838]
2 payload Payload 0..1 Choice of literal content or URL
3 hashes Hashes 0..1 Hashes of the payload content

Usage Requirement: Device

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

ID Name Type # Description
1 hostname Hostname 0..1 A hostname that can be used to connect to this device over a network
2 idn_hostname IDN-Hostname 0..1 An internationalized hostname that can be used to connect to this device over a network
3 device_id String 0..1 An identifier that refers to this device within an inventory or management system

Usage Requirement: Domain Name

Type Name Type Definition Description
Domain-Name String /hostname [RFC1034], Section 3.5 Email Address

Type Name Type Definition Description
Email-Addr String /email Email address, [RFC5322], Section 3.4.1 Features

Type Name Type Definition # Description
Features Feature unique 0..10 An array of zero to ten names used to query a Consumer for its supported capabilities.

Usage Requirements: File

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

ID Name Type # Description
1 name String 0..1 The name of the file as defined in the file system
2 path String 0..1 The absolute path to the location of the file in the file system
3 hashes Hashes 0..1 One or more cryptographic hash codes of the file contents

Usage Requirement: Internationalized Domain Name

Type Name Type Definition Description
IDN-Domain-Name String /idn-hostname Internationalized Domain Name, [RFC5890], Section Internationalized Email Address

Type Name Type Definition Description
IDN-Email-Addr String /idn-email Internationalized email address, [RFC6531] 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, "" is range of IP addresses with a prefix of 24 (i.e. -

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)

ID Type # Description
1 IPv4-Addr 1 IPv4 address as defined in [RFC0791]
2 Integer 0..1 CIDR prefix-length. If omitted, refers to a single host address. IPv4 Connection

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

ID Name Type # Description
1 src_addr IPv4-Net 0..1 IPv4 source address range
2 src_port Port 0..1 Source service per [RFC6335]
3 dst_addr IPv4-Net 0..1 IPv4 destination address range
4 dst_port Port 0..1 Destination service per [RFC6335]
5 protocol L4-Protocol 0..1 Layer 4 protocol (e.g., TCP) - see Section

Usage Requirement: IPv6 Address Range

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

ID Type # Description
1 IPv6-Addr 1 IPv6 address as defined in [RFC8200]
2 Integer 0..1 prefix-length. If omitted, refers to a single host address. IPv6 Connection

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

ID Name Type # Description
1 src_addr IPv6-Net 0..1 IPv6 source address range
2 src_port Port 0..1 Source service per [RFC6335]
3 dst_addr IPv6-Net 0..1 IPv6 destination address range
4 dst_port Port 0..1 Destination service per [RFC6335]
5 protocol L4-Protocol 0..1 Layer 4 protocol (e.g., TCP) - Section

Usage Requirement: IRI

Type Name Type Definition Description
IRI String /iri Internationalized Resource Identifier, [RFC3987]. MAC Address

Type Name Type Definition Description
MAC-Addr Binary /eui Media Access Control / Extended Unique Identifier address - EUI-48 or EUI-64 as defined in [EUI]. Process

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

ID Name Type # Description
1 pid Integer{0..*} 0..1 Process ID of the process
2 name String 0..1 Name of the process
3 cwd String 0..1 Current working directory of the process
4 executable File 0..1 Executable that was executed to start the process
5 parent Process 0..1 Process that spawned this one
6 command_line String 0..1 The full command line invocation used to start this process, including all arguments

Usage Requirement: URI

Type Name Type Definition Description
URI String (uri) Uniform Resource Identifier, [RFC3986].

3.4.2 Data Types Action-Targets

Type Name Type Definition Description
Action-Targets MapOf(Action, Targets){1..*} Map of each action supported by this actuator function to the list of targets applicable to that action. Command-ID

Type Name Type Definition Description
Command-ID String (%^\S{0,36}$%) Command Identifier Date-Time

Type Name Type Definition Description
Date-Time Integer{0..*} Date and Time

Usage Requirements: Duration

Type Name Type Definition Description
Duration Integer{0..*} A length of time

Usage Requirements:

3.4.2.F Feature

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

Type: Feature (Enumerated)

ID Name Description
1 versions List of OpenC2 Language versions supported by this Consumer
2 profiles List of Actuator profiles supported by this Consumer
3 pairs List of supported Actions and applicable Targets
4 rate_limit Maximum number of Commands per minute supported by design or policy Hashes

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

ID Name Type # Description
1 md5 Binary /x 0..1 MD5 hash as defined in [RFC1321]
2 sha1 Binary /x 0..1 SHA1 hash as defined in [RFC6234]
3 sha256 Binary /x 0..1 SHA256 hash as defined in [RFC6234]

Usage Requirement: Hostname

Type Name Type Definition Description
Hostname String /hostname Internet host name as specified in [RFC1123] Internationalized Hostname

Type Name Type Definition Description
IDN-Hostname String /idn-hostname Internationalized Internet host name as specified in [RFC5890], Section IPv4 Address

Type Name Type Definition Description
IPv4-Addr Binary /ipv4-addr 32 bit IPv4 address as defined in [RFC0791] IPv6 Address

Type Name Type Definition Description
IPv6-Addr Binary /ipv6-addr 128 bit IPv6 address as defined in [RFC8200] 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)

ID Name Description
1 icmp Internet Control Message Protocol - [RFC0792]
6 tcp Transmission Control Protocol - [RFC9293]
17 udp User Datagram Protocol - [RFC0768]
28 ipv6_icmp ICMP for IPv6 - [RFC8200]
132 sctp Stream Control Transmission Protocol - [RFC4960]

Usage Requirement: Message-Type

Identifies the type of Message.

Type: Message-Type (Enumerated)

ID Name Description
1 command The Message content is an OpenC2 Command
2 response The Message content is an OpenC2 Response Namespace Identifier

Type Name Type Definition Description
Nsid String{1..16} A short identifier that refers to a namespace. Payload

Type: Payload (Choice)

ID Name Type # Description
1 bin Binary 1 Specifies the data contained in the artifact
2 url URI 1 MUST be a valid URL that resolves to the un-encoded content Port

Type Name Type Definition Description
Port Integer{0..65535} Transport Protocol Port Number, [RFC6335] Response-Type

Type: Response-Type (Enumerated)

ID Name Description
0 none No response
1 ack Respond when Command received
2 status Respond with progress toward Command completion
3 complete Respond when all aspects of Command completed Targets

Type Name Type Definition Description
Targets ArrayOf(Enum(Target)){1..*} unique List of Target fields Version

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

Type Name Type Definition Description
Version String OpenC2 version in "Major.Minor" format

Usage Requirement:

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 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':

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.


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


    "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.


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


    "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

5.2 Conformance Clause 2: Response

A conformant Response

5.3 Conformance Clause 3: Producer

A conformant Producer

5.4 Conformance Clause 4: Consumer

A conformant Consumer

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.


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.


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


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


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


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


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


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


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.


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


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.


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


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


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.


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


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.


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.


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.


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


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


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.


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


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.


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.


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.


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.


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.


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.


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


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.


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.


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.


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.


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.


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


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


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


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

A.2 Informative References


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.


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


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


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


"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.


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


    "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.


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.


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


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.

Signature value:


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.


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.


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


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


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.


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)


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


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

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:

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):

Serialization Type Description
Verbose JSON Human-readable JSON format using name-value encoding for tabular data
Compact JSON Human-readable JSON format using positional encoding for tabular data
Concise JSON Represents JADN data types in a format optimized for minimum size
CBOR Concise Binary Object Representation format of JADN types

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 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](#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, 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):

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 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"]

["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:

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

Appendix E. Revision History

Revision Date Editor Changes Made
v1.1-wd01 10/31/2017 Sparrell, Considine Initial working draft
Issue #388, item 1, #390 08/xx/2022 Lemire Add guidance in 3.1.2,, regarding types that depend on external registries, and add associated references; update RFC reference for TCP
Issue #388, item 4 08/xx/2022 Lemire Add usage requirement for Version format in
Issue #386, #387 08/xx/2022 Lemire Adjust response_requested handling ( to consider Consumer error situations
Issues #389, #392 8/24/2022 Lemire Remove Properties target type, per 8/10/2022 working meeting discussion
Issue #369 7/27/2022 Lemire * Add "comment" as command argument
Issue #393 8/2/2022 Lemire * Change ArrayOf() to multiplicity where possible
Issue #396 8/xx/2022 Lemire * Fixed malformed table in
* Reordered data types alphabetically
Administrative 9/07/2022 Lemire Changes for version update, v1.1 to v2.0
Issue #361 9/xx/2022 Lemire Add explanatory JADN appendix
Create WD01 11/11/2022 Lemire Create first WD package for v2.0

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:

First Name Last Name Company
Philippe Alcoy Arbor Networks
Darren Anstee Arbor Networks
Michelle Barry AT&T
Brian Berliner Symantec Corp.
Adam Bradbury EclecticIQ
Joe Brule National Security Agency
Michael Butt NC4
Toby Considine University of North Carolina at Chapel Hill
Trey Darley New Context Services Inc.
David Darnell North American Energy Standards Board
Sudeep Das McAfee
Andrea De Bernardi Moviri SPA
Blake Essing AT&T
Alex Everett University of North Carolina at Chapel Hill
Joyce Fai National Security Agency
Travis Farral Anomali
David Girard Trend Micro
Andy Gray ForeScout
John-Mark Gurney New Context Services Inc.
Stefan Hagen Individual
David Hamilton AT&T
Nick Humphrey Huntsman Security
Christian Hunt New Context Services Inc.
April Jackson G2
Sridhar Jayanthi Individual
Bret Jordan Symantec Corp.
Jason Keirstead IBM
David Kemp National Security Agency
David Lemire G2
Jason Liu Northrop Grumman
Radu Marian Bank of America
Danny Martinez G2
Lisa Mathews National Security Agency
James Meck FireEye Inc.
Efrain Ortiz Symantec Corp.
Paul Patrick FireEye Inc.
Michael Pepin NC4
Nirmal Rajarathnam ForeScout
Chris Ricard Financial Services Information Sharing and Analysis Center (FS-ISAC)
Daniel Riedel New Context Services Inc.
Jason Romano National Security Agency
Philip Royer Splunk Inc.
Thomas Schreck Siemens AG
Duane Skeen Northrop Grumman
Duncan Sparrell sFractal Consulting LLC
Michael Stair AT&T
Andrew Storms New Context Services Inc.
Gerald Stueve Fornetix
Rodney Sullivan NCI Agency
Allan Thomson LookingGlass
Bill Trost AT&T
Raymon van der Velde EclecticIQ
Jyoti Verma Cisco Systems
David Waltermire NIST
Jason Webb LookingGlass
Sean Welsh AT&T
Charles White Fornetix
Sounil Yu Bank of America
Vasileios Mavroeidis University of Oslo

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