Orange Book Security Class Delta Requirements

The Orange Book security requirements have been reformulated as a delta (differences only) document for easier comprehension of differences of functionality from one class to the next. Each higher class adds to or modifies the requirements of the lower class. Text is quoted directly from the document TCSEC, DOD 5200.28-STD.

Discretionary Access Control

1 - C1
  The TCB shall define and control access between named users and named objects (e.g., files and programs) in the ADP system. The enforcement mechanism (e.g., self/ group /public controls, access control lists) shall allow users to specify and control sharing of those objects by named individuals or defined groups or both.

2 - C2, B1, B2
  Modified.
  The enforcement mechanism (e.g., self/ group /public controls, access control lists) shall allow users to specify and control sharing of those objects by named individuals, or defined groups of individuals, or by both, and shall provide controls to limit propagation of access rights.

  The discretionary access control mechanism shall, either by explicit user action or by default, provide that objects are protected from unauthorized access. These access controls shall be capable of including or excluding access to the granularity of a single user. Access permission to an object by users not already possessing access permission shall only be assigned by authorized users.

3 - B3, A1
  Modified.
  The enforcement mechanism (e.g., access control lists) shall allow users to specify and control sharing of those objects, and shall provide controls to limit propagation of access rights.

  Modified.
  These access controls shall be capable of specifying, for each named object, a list of named individuals and a list of groups of named individuals with their respective modes of access to that object. Furthermore, for each such named object, it shall be possible to specify a list of named individuals and a list of groups of named individuals for which no access to the object is to be given.

Object Reuse

4 - C2, B1, B2, B3, A1
  All authorizations to the information contained within a storage object shall be revoked prior to initial assignment, allocation or reallocation to a subject from the TCB's pool of unused storage objects. No information, including encrypted representations of information, produced by a prior subject's actions is to be available to any subject that obtains access to an object that has been released back to the system.

Labels

5 - B1
  Sensitivity labels associated with each subject and storage object under its control (e.g., process, file, segment, device) shall be maintained by the TCB. These labels shall be used as the basis for mandatory access control decisions. In order to import non-labeled data, the TCB shall request and receive from an authorized user the security level of the data, and all such actions shall be auditable by the TCB.

6 - B2, B3, A1
  Modified.
  Sensitivity labels associated with each ADP system resource (e.g., subject, storage object, ROM) that is directly or indirectly accessible by subjects external to the TCB shall be maintained by the TCB.

Label Integrity

7 - B1, B2, B3, A1
  Sensitivity labels shall accurately represent security levels of the specific subjects or objects with which they are associated. When exported by the TCB, sensitivity labels shall accurately and unambiguously represent the internal labels and shall be associated with the information being exported.

Exportation of Labeled Information

8 - B1, B2, B3, A1
  The TCB shall designate each communication channel and I/O device as either single-level or multilevel. Any change in this designation shall be done manually and shall be auditable by the TCB. The TCB shall maintain and be able to audit any change in the security level or levels associated with a communication channel or I/O device.

Exportation to Multilevel Devices

9 - B1, B2, B3, A1
  When the TCB exports an object to a multilevel I/O device, the sensitivity label associated with that object shall also be exported and shall reside on the same physical medium as the exported information and shall be in the same form (i.e., machine-readable or human-readable form). When the TCB exports or imports an object over a multilevel communication channel, the protocol used on that channel shall provide for the unambiguous pairing between the sensitivity labels and the associated information that is sent or received.

Exportation to Single-Level Devices

10 - B1, B2, B3, A1
  Single-level I/O devices and single-level communication channels are not required to maintain the sensitivity labels of the information they process. However, the TCB shall include a mechanism by which the TCB and an authorized user reliably communicate to designate the single security level of information imported or exported via single-level communication channels or I/O devices.

Labeling Human-Readable Output

11 - B1, B2, B3, A1
  The ADP system administrator shall be able to specify the printable label names associated with exported sensitivity labels. The TCB shall mark the beginning and end of all human-readable, paged, hardcopy output (e.g., line printer output) with human-readable sensitivity labels that properly (1) represent the sensitivity of the output. The TCB shall, by default, mark the top and bottom of each page of human-readable, paged, hardcopy output (e.g., line printer output) with human-readable sensitivity labels that properly (1) represent the overall sensitivity of the output or that properly (1) represent the sensitivity of the information on the page. The TCB shall, by default and in an appropriate manner, mark other forms of human-readable output (e.g., maps, graphics) with human-readable sensitivity labels that properly (1) represent the sensitivity of the output. Any override of these marking defaults shall be auditable by the TCB.

  (1) The hierarchical classification component in human-readable sensitivity labels shall be equal to the greatest hierarchical classification of any of the information in the output that the labels refer to; the non-hierarchical category component shall include all of the non-hierarchical categories of the information in the output the labels refer to, but no other non-hierarchical categories.

Mandatory Access Control

12 - B1
  The TCB shall enforce a mandatory access control policy over all subjects and storage objects under its control (e.g., processes, files, segments, devices). These subjects and objects shall be assigned sensitivity labels that are a combination of hierarchical classification levels and non-hierarchical categories, and the labels shall be used as the basis for mandatory access control decisions. The TCB shall be able to support two or more such security levels. (See the Mandatory Access Control guidelines.) The following requirements shall hold for all accesses between subjects and objects controlled by the TCB: A subject can read an object only if the hierarchical classification in the subject's security level is greater than or equal to the hierarchical classification in the object's security level and the non-hierarchical categories in the subject's security level include all the non-hierarchical categories in the object's security level. A subject can write an object only if the hierarchical classification in the subject's security level is less than or equal to the hierarchical classification in the object's security level and all the non-hierarchical categories in the subject's security level are included in the non-hierarchical categories in the object's security level. Identification and authentication data shall be used by the TCB to authenticate the user's identity and to ensure that the security level and authorization of subjects external to the TCB that may be created to act on behalf of the individual user are dominated by the clearance and authorization of that user.

13 - B2, B3, A1
  Modified.
  The TCB shall enforce a mandatory access control policy over all resources (i.e., subjects, storage objects, and I/O devices) that are directly or indirectly accessible by subjects external to the TCB.

  Modified.
  The following requirements shall hold for all accesses between all subjects external to the TCB and all objects directly or indirectly accessible by these subjects: A subject can read an object only if the hierarchical classification in the subject's security level is greater than or equal to the hierarchical classification in the object's security level and the non-hierarchical categories in the subject's security level include all the non-hierarchical categories in the object's security level.

Subject Sensitivity Labels

14 - B2, B3, A1
  The TCB shall immediately notify a terminal user of each change in the security level associated with that user during an interactive session. A terminal user shall be able to query the TCB as desired for a display of the subject's complete sensitivity label.

Device Labels

15 - B2, B3, A1
  The TCB shall support the assignment of minimum and maximum security levels to all attached physical devices. These security levels shall be used by the TCB to enforce constraints imposed by the physical environments in which the devices are located.

Identification and Authentication

16 - C1
  The TCB shall require users to identify themselves to it before beginning to perform any other actions that the TCB is expected to mediate. Furthermore, the TCB shall use a protected mechanism (e.g., passwords) to authenticate the user's identity. The TCB shall protect authentication data so that it cannot be accessed by any unauthorized user.

17 - C2
  The TCB shall be able to enforce individual accountability by providing the capability to uniquely identify each individual ADP system user. The TCB shall also provide the capability of associating this identity with all auditable actions taken by that individual.

18 - B1, B2, B3, A1
  Modified.
  Furthermore, the TCB shall maintain authentication data that includes information for verifying the identity of individual users (e.g., passwords) as well as information for determining the clearance and authorizations of individual users. This data shall be used by the TCB to authenticate the user's identity and to ensure that the security level and authorizations of subjects external to the TCB that may be created to act on behalf of the individual user are dominated by the clearance and authorization of that user.

Audit

19 - C2
  The TCB shall be able to create, maintain, and protect from modification or unauthorized access or destruction an audit trail of accesses to the objects it protects. The audit data shall be protected by the TCB so that read access to it is limited to those who are authorized for audit data. The TCB shall be able to record the following types of events: use of identification and authentication mechanisms, introduction of objects into a user's address space (e.g., file open, program initiation), deletion of objects, actions taken by computer operators and system administrators and/or system security officers, and other security relevant events. For each recorded event, the audit record shall identify: date and time of the event, user, type of event, and success or failure of the event. For identification/ authentication events the origin of request (e.g., terminal ID) shall be included in the audit record. For events that introduce an object into a user's address space and for object deletion events the audit record shall include the name of the object. The ADP system administrator shall be able to selectively audit the actions of any one or more users based on individual identity.

20 - B1
  The TCB shall also be able to audit any override of human-readable output markings.

  Modified.
  For events that introduce an object into a user's address space and for object deletion events the audit record shall include the name of the object and the object's security level. The ADP system administrator shall be able to selectively audit the actions of any one or more users based on individual identity and/or object security level.

21 - B2
  The TCB shall be able to audit the identified events that may be used in the exploitation of covert storage channels.

22 - B3, A1
  The TCB shall contain a mechanism that is able to monitor the occurrence or accumulation of security auditable events that may indicate an imminent violation of security policy. This mechanism shall be able to immediately notify the security administrator when thresholds are exceeded and, if the occurrence or accumulation of these security relevant events continues, the system shall take the least disruptive action to terminate the event.

Trusted Path

23 - B2
  The TCB shall support a trusted communication path between itself and user for initial login and authentication. Communications via this path shall be initiated exclusively by a user.

24 - B3, A1
  Modified.
  The TCB shall support a trusted communication path between itself and users for use when a positive TCB-to-user connection is required (e.g., login, change subject security level). Communications via this trusted path shall be activated exclusively by a user or the TCB and shall be logically isolated and unmistakably distinguishable from other paths.

System Architecture

25 - C1
  The TCB shall maintain a domain for its own execution that protects it from external interference or tampering (e.g., by modification of its code or data structures). Resources controlled by the TCB may be a defined subset of the subjects and objects in the ADP system.

26 - C2
  The TCB shall isolate the resources to be protected so that they are subject to the access control and auditing requirements.

27 - B1
  Modified.
  The TCB shall maintain process isolation through the provision of distinct address spaces under its control.

28 - B2
  The TCB shall be internally structured into well-defined largely independent modules. It shall make effective use of available hardware to separate those elements that are protection-critical from those that are not. The TCB modules shall be designed such that the principle of least privilege is enforced. Features in hardware, such as segmentation, shall be used to support logically distinct storage objects with separate attributes (namely: readable, writable). The user interface to the TCB shall be completely defined and all elements of the TCB identified.

29 - B3, A1
  The TCB shall be designed and structured to use a complete, conceptually simple protection mechanism with precisely defined semantics. This mechanism shall play a central role in enforcing the internal structuring of the TCB and the system. The TCB shall incorporate significant use of layering, abstraction and data hiding. Significant system engineering shall be directed toward minimizing the complexity of the TCB and excluding from the TCB modules that are not protection-critical.

System Integrity

30 - C1, C2, B1, B2, B3, A1
  Hardware and/or software features shall be provided that can be used to periodically validate the correct operation of the on-site hardware and firmware elements of the TCB.