Only interconnection type components support constraints

[aj-stein-gsa]

Describe the bug

When attempting to enhance constraints for different types of components in a system security plan that represent cross-boundary communication, we have confirmed that a prop[@name="direction"] is necessary to describe the direction of network communication. However, you can only use this property on component[@type="interconnection"], not others as applicable. More details can be found in GSA/fedramp-automation#950 to complete work for GSA/fedramp-automation#930.

Below is the relevant constraint that needs to be adjusted.

OSCAL/src/metaschema/oscal_implementation-common_metaschema.xml

Lines 191 to 198 in b123c11

	<allowed-values target="(.)[@type='interconnection']/prop[has-oscal-namespace('http://csrc.nist.gov/ns/oscal')]/@name">
	<enum value="isa-title">Title of the Interconnection Security Agreement (ISA).</enum>
	<enum value="isa-date">Date of the Interconnection Security Agreement (ISA).</enum>
	<enum value="isa-remote-system-name">The name of the remote interconnected system.</enum>
	<enum value="ipv4-address">An Internet Protocol Version 4 interconnection address</enum>
	<enum value="ipv6-address">An Internet Protocol Version 6 interconnection address</enum>
	<enum value="direction">An Internet Protocol Version 6 interconnection address</enum>
	</allowed-values>

https://github.com/usnistgov/OSCAL/blob/v1.1.3/src/metaschema/oscal_implementation-common_metaschema.xml#L191-L198

Who is the bug affecting

Developers and engineers who want to develop or consume constraint-based analysis to know if their OSCAL-based system security plan meets all NIST and FedRAMP-specific requirements.

What is affected by this bug

Metaschema, Modeling

How do we replicate this issue

1. Create a SSP with a component with a type that is not .[@type="interconnection"] and a prop[@name="direction" and @value="incoming"].
2. Run the oscal-cli or other conformant tooling to confirm the constraint does not permit this allowed value.

Expected behavior (i.e. solution)

Different types of components permit the use of this property.

Other comments

FedRAMP can use a @ns flag for the given prop, but we want to align with general use cases NIST supports and that can increase confusion about the difference between the identically named props while also decreasing interoperability.

Revisions

No response

[brian-ruf]

The above property collection needs to be de-coupled.

The following allowed values continue to only apply to interconnection components:

       <enum value="isa-title">Title of the Interconnection Security Agreement (ISA).</enum> 
       <enum value="isa-date">Date of the Interconnection Security Agreement (ISA).</enum> 
       <enum value="isa-remote-system-name">The name of the remote interconnected system.</enum> 

The following allowed values must be allowed on all of the following component types:

• system
• service
• interconnection
• software

       <enum value="ipv4-address">An Internet Protocol Version 4 interconnection address</enum> 
       <enum value="ipv6-address">An Internet Protocol Version 6 interconnection address</enum> 
       <enum value="direction">An Internet Protocol Version 6 interconnection address</enum> 

Happy to provide justification if necessary.