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id: "SA-17(04)" title: "Informal Correspondence" family: "SA" family_name: "System and Services Acquisition" sort_id: "sa-17.04" priority: "P1" implementation_level: "organization" parent: "SA-17" enhancement: True

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Statement

Require the developer of the system, system component, or system service to:

Produce, as an integral part of the development process, an informal descriptive top-level specification that specifies the interfaces to security-relevant hardware, software, and firmware in terms of exceptions, error messages, and effects;

Show via {{ insert: param, sa-17.04_odp }} that the descriptive top-level specification is consistent with the formal policy model;

Show via informal demonstration, that the descriptive top-level specification completely covers the interfaces to security-relevant hardware, software, and firmware;

Show that the descriptive top-level specification is an accurate description of the interfaces to security-relevant hardware, software, and firmware; and

Describe the security-relevant hardware, software, and firmware mechanisms not addressed in the descriptive top-level specification but strictly internal to the security-relevant hardware, software, and firmware.

Guidance

Correspondence is an important part of the assurance gained through modeling. It demonstrates that the implementation is an accurate transformation of the model, and that additional code or implementation detail has no impact on the behaviors or policies being modeled. Consistency between the descriptive top-level specification (i.e., high-level/low-level design) and the formal policy model is generally not amenable to being fully proven. Therefore, a combination of formal and informal methods may be needed to show such consistency. Hardware, software, and firmware mechanisms strictly internal to security-relevant hardware, software, and firmware include mapping registers and direct memory input and output.

Assessment Objective: as an integral part of the development process, the developer of the system, system component, or system service is required to produce an informal, descriptive top-level specification that specifies the interfaces to security-relevant hardware, software, and firmware in terms of exceptions;

Assessment Objective: as an integral part of the development process, the developer of the system, system component, or system service is required to produce an informal, descriptive top-level specification that specifies the interfaces to security-relevant hardware, software, and firmware in terms of error messages;

Assessment Objective: as an integral part of the development process, the developer of the system, system component, or system service is required to produce an informal, descriptive top-level specification that specifies the interfaces to security-relevant hardware, software, and firmware in terms of effects;

Assessment Objective: the developer of the system, system component, or system service is required to show via {{ insert: param, sa-17.04_odp }} that the descriptive top-level specification is consistent with the formal policy model;

Assessment Objective: the developer of the system, system component, or system service is required to show via informal demonstration that the descriptive top-level specification completely covers the interfaces to security-relevant hardware, software, and firmware;

Assessment Objective: the developer of the system, system component, or system service is required to show that the descriptive top-level specification is an accurate description of the interfaces to security-relevant hardware, software, and firmware;

Assessment Objective: the developer of the system, system component, or system service is required to describe the security-relevant hardware, software, and firmware mechanisms that are not addressed in the descriptive top-level specification but are strictly internal to the security-relevant hardware, software, and firmware.

System and services acquisition policy

enterprise architecture policy

formal policy model

procedures addressing developer security architecture and design specifications for the system

solicitation documentation

acquisition documentation

service level agreements

acquisition contracts for the system, system component, or system service

informal, descriptive top-level specification documentation

system security architecture and design documentation

system design documentation

system configuration settings and associated documentation

documentation describing security-relevant hardware, software, and firmware mechanisms not addressed in the informal, descriptive top-level specification documentation

system security plan

other relevant documents or records

Organizational personnel with system and service acquisition responsibilities

organizational personnel with information security responsibilities

system developer

organizational personnel with information security architecture and design responsibilities