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Trusted Product Evaluation Questionnaire

National Computer Security Center

9800 Savage Road

Fort George G. Meade, MD 20755-6000

May 2,1992

NCSC-TG-019

Library No. 5-232,458

Version 2

FOREWORD

The National Computer Security Center is publishing the Trusted Product
Evaluation Questionnaire as part of the "Rainbow Series" of documents our
Technical Guidelines Program produces. In the Rainbow Series, we discuss
in detail the features of the Department of Defense Trusted Computer
System Evaluation Criteria (DoD 5200.28-STD) and provide guidance for
meeting each requirement. The National Computer Security Center, through
its Trusted Product Evaluation Program, evaluates the security features of
commercially-produced computer systems. Together, these programs ensure
that organizations are capable of protecting their important data with
trusted computer systems.

The Trusted Product Evaluation Questionnaire is a tool to assist system
developers and vendors in gathering data to assist evaluators and
potentially certifiers in their assessment of the system.

As the Director, National Computer Security Center, I invite your
recommendations for revision to this technical guideline. We plan to
review and update this document periodically in response to the needs of
the community. Please address any proposals for revision through
appropriate channels to:

National Computer Security Center

9800 Savage Road

Ft. George G. Meade, MD 20755-6000

Attention: Chief, Standards, Criteria, and Guidelines Division

Patrick R. G g . May 1992

Director

National Computer Security Center

ACKNOWLEDGMENTS

The National Computer Security Center expresses appreciation to Dr.
Santosh Chokhani and Harriet Goldman, of the MITRE Corporation, as the
principal authors of version I of this document; Mr. Kenneth B. Elliott
III and Dr. Dixie Baker, of The Aerospace Corporation, as the principal
authors of version 2 this document; and ENS Susan L. Mitchell as project
manager.

We also thank the evaluators, vendors, and users in the United States
computer security community who contributed their time and expertise to
the review of this document.

Chapter 1 INTRODUCTION

One of the principal goals of the National Computer Security Center (NCSC)
is to encourage the widespread availability of trusted computer systems.
In support of this goal a metric was created, the Department of Defense
Trusted Computer System Evaluation Criteria (TCSEC), against which
computer systems could be evaluated. The TCSEC was originally published on
15 August 1983 as CSC-STD-001-83. In December 1985 the DoD adopted it,
with a few changes, as a DoD Standard, DoD 5200.28-STD. DoD Directive
5200.28, "Security Requirements for Automatic Information Systems (AISs),"
has been written to require, among other things, the Department of Defense
Trusted Computer System Evaluation Criteria to be used throughout the DoD.
The TCSEC is the standard used for evaluating the effectiveness of
security controls built into ADP systems. The TCSEC is divided into four
divisions: D, C, B, and A, ordered in a hierarchical manner with the
highest division (A) being reserved for systems providing the best
available level of assurance. Within divisions C, B, and A there are
subdivisions known as classes, which are also ordered in a hierarchical
manner to represent different levels of security in these classes.

The National Security Agency (NSA) has established an aggressive program
to study and implement computer security technology and to encourage the
widespread availability of trusted computer products for use by any
organization desiring better protection of their important data and
information processing services. The Trusted Product Evaluation Program
and the open and cooperative business relationship being forged with the
computer and telecommunications industries will result in the fulfillment
of our country's computer security requirement. We are resolved to meet
the challenge of identifying trusted computer products suitable for use in
processing all types and classifications of information.

For definition and clarification of the terms used in this document,
please see the glossary section of this questionnaire.

Sub-questions within the numbered questions have been designated with
letters (e.g., (a), (b), ...) so that answers to all parts of the main
question can be identified.

Review of this document will occur periodically or when the need arises.
Address all proposals for revision through appropriate channels to:

National Computer Security Center

9800 Savage Road

Fort George G. Meade, MD 20755-6000

Attention: Chief, Standards, Criteria, and Guidelines Division

1.1 PURPOSE

The NSA is responsible for evaluating commercial products through an
independent evaluation based on TCSEC requirements by a qualified team of
experts and maintaining a list of those products on the Evaluated Products
List (EPL). To accomplish this mission, the NSA Trusted Product Evaluation
Program has been established to assist vendors in developing, testing, and
evaluating trusted products for the EPL.

During the evaluation process, the TCSEC for classes C1 through Al
requires a determination that the security features of a system are
implemented as designed and that they are adequate for the specified level
of trust. In addition, the TCSEC also requires documentation to support a
system's security. During the various phases of the evaluation process,
the vendor supplies to an evaluation team certain information on system
security and documentation. The purpose of the Trusted Product Evaluation
Questionnaire (prod-uct questionnaire) is to assist system developers and
vendors as a data gathering tool for formalizing the data gathering
process for the various phases of the Trusted Products Evaluation process.
Additionally, the product questionnaire may be used as a data gathering
tool to assist certifiers in the evaluation process for certification and
accreditation if the Final Evaluation Report is unavailable.

Examples in this document are not to be construed as the only
implementations that may answer the question. The examples are suggestions
of appropriate implementations. The recommendations in this document are
also not to be construed as supplementary requirements to the
questionnaire.

1.2 SCOPE

The product questionnaire addresses the TCSEC Criteria Classes C1 through
Al. In an effort to gather a better understanding of the system security,
some questions in the product questionnaire address information in
addition to that required in the Department of Defense Trusted Computer
Systems Evaluation Criteria. This document is generally organized by
Criteria subject area; within each subject area, the questions are broken
down in a manner similar to Appendix D of the Criteria. This breakdown
readily allows the reader to discern the questions that are appropriate to
each of the Criteria levels. Of course, all of the questions at levels
lower than the target level are applicable.

The information provided in the product questionnaire by the vendor is to
assist the evaluator in obtaining an initial understanding of the system
applying for evaluation and its security features of the respective
Criteria class. The product questionnaire is not a statement of
requirements, just an information gathering tool. This document should
give the vendor an idea of the information required by the evaluator
during the evaluation process and prepare the vendor for additional
information needed by the evaluation team later on in the evaluation
process.

The product questionnaire will be initially sent out to the vendor prior
to the Preliminary Technical Review (PTR). The vendor can point to
appropriate documents for the answers. The vendor need not answer the
questions that are not pertinent. Some of the questions may be applicable
at the later stages of the evaluation process and thus may be deferred
until the appropriate time (e.g., a finished copy of the Verification
Plan). Although the vendor is not obligated to send a completed product
questionnaire prior to the PTR, the vendor should have the questionnaire
substantially completed by the PTR date so that the PTR team can use the
Questionnaire as in input into determining the vendor's ability to support
an evaluation. The PTR team will also use the product questionnaire during
the PTR to seek additional information to be used later on in the
evaluation process. When an evaluation team has reached the Design
Analysis Phase and is preparing the Initial Product Assessment Report, it
will use the product questionnaire to seek specific references in vendor
documentation for further details on the answers to these questions.

The completed document is to provide the evaluator an understanding of the
various hardware and software configurations, architecture and design,
testing, and documentation, system security features and their
applicability to security and accountability policy, Trusted Computing
Base (TCB) isolation and non-circumventability, and covert channel
analysis methods. This product questionnaire also requests information on
penetration testing and specification-to-code correspondence for systems
to which these requirements are applicable.

While this product questionnaire is designed for operating systems and
does not specifically address networks, subsystems, or database management
systems, vendors participating in these areas may find it useful to review
this document and answer any applicable questions.

Chapter 2 QUESTIONNAIRE

2.1 SUBJECTS

A subject is an active entity in the system, generally in the form of a
person, process, or device that causes information to flow among objects
or changes the system state. A subject can be viewed as a process/domain
pair whose access controls are checked prior to granting the access to
objects.

C1:

1. (a) List and (b) describe the subjects in your system.

2. (a) When and (b) how are the subjects created? (For example, they can
be created or activated when a user logs on or when a process is spawned.)

3. (a) When and (b) how are the subjects destroyed? (For example, they can
be destroyed or deactivated when a process terminates or when the user
logs off.)

4. (a) What are the security attributes of a subject? (Examples of
security attributes are user name, group id, sensitivity level, etc.) For
each type of subject in your system (e.g., user, process, device), what
mechanisms are available to (b) define and ┐ modify these attributes? (d)
Who can invoke these mechanisms?

5. (a) What are other security-relevant privileges a subject can have?
(Examples of such privileges are: super user, system operator, system
administrator, etc. Your operating system may assign numerous other
privileges to the subjects, such as the ability to use certain devices.)
For each type of subject in your system, what mechanisms are available to
(b) define and ┐ modify these pnvileges? (d) Who can invoke these
mechanisms? (e) Provide a list of subjects within the TCB boundary and (f)
the list of privileges for each of them.

6. When a subject is created, where do its (a) security attributes and (b)
privileges originate; i.e., how are the security attributes and privileges
inherited?

7. List the subjects, if any, which are not controlled by the TCB.

2.2 OBJECTS

An object is a passive entity that contains or receives information.
Access to an object potentially implies access to the information it
contains. Examples of objects are: records, blocks, pages, segments,
files, directories, directory tree, and programs, as well as bits, bytes,
words, fields, processors, video displays, keyboards, clocks, printers,
network nodes.

C1:

1. Provide a list of objects within the TCB (e.g., authentication
database, print queues).

2. List the objects in your system that are protected by the Discretionary
Access Control (DAC) mechanisms.

3. (a) List the objects that are not protected by the DAC mechanism. (b)
Why are they not protected? ┐ Describe other mechanisms used to isolate
and protect objects.

4. (a) List other resources which are not protected by the DAC mechanism
(Examples include temporary data files accessible only to the file's
owner). (b) Why are they not protected by DAC? ┐ Describe the mechanisms
that are used to isolate and protect these resources.

5. How are the various types of objects created (e.g., directories, files,
devices)?

6. How are the various types of objects destroyed?

7. (a) What are the security attributes of an object? For each type of
object in your system, what mechanisms are available to (b) define and ┐
modify these attributes? (d) Who can invoke these mechanisms?

8. When an object is created, where do its security attributes originate
(i.e., how are the security attributes inherited?)

B1:

9. List the objects in your system that are protected by the Mandatory
Access Control (MAC) mechanisms.

10. (a) List the objects that are not protected by the MAC mechanism. (b)
Why are they not protected? ┐ Describe other mechanisms used to isolate
and protect objects.

11. (a) List other resources which are not protected by the MAC mechanism.
(b) Why are they not protected? ┐ Describe the mechanisms that are used to
isolate and protect these resources.

2.3 HARDWARE ARCHITECTURE

If this evaluation is for a family of hardware, the following questions
should be answered for each member of the hardware family. You may choose
to answer each question for each member of the family, or answer each
question for a baseline family member and point out the difference for
each of the remaining family members.

C1:

1. Provide a high-level block diagram of the system. The diagram should at
least depict various Central Processor Units (CPUs), memory controllers,
memory, 1/0 processors, 1/0 controllers, 1/0 devices (e.g. printers,
displays, disks, tapes, communications lines) and relationships (both
control flow and data flow) among them.

2. (a) Describe the portions of the system (if any) which contain
microcode. (b) How is this microcode protected and loaded?

3. (a) Provide a list of privileged instructions for your hardware. (b)
Provide a brief description of each privileged instruction.

4. For each privileged instruction, provide the privileges required to
execute the instruction. (Examples of privileges include the machine
state, the executing ring/segment/domain/ privilege level, physical memory
location of the instruction, etc.)

5. How does the process address translation (logical/virtual to physical)
work in your system?

6. (a) How does 1/0 processing address translation work for the Direct
Memory Access (DMA) controllers/devices? (b) Identify if the address
translation is done through the memory address translation unit or if the
logic is part of the controller. ┐ How are the address translation maps
and/or tables initialized?

7. Describe the hardware protection mechanisms provided by the system.

8. Describe what hardware mechanisms are used to isolate the TCB from
untrusted applications.

9. (a) What are the machine/processor states supported by the system? (b)
How are the states changed? ┐ What data structures are saved as part of
the processor state?

10. List all the (a) interrupts and (b) traps (hardware and software). ┐
How are they serviced by the system?

B1:

11. Provide a high-level block diagram of a CPU. The diagram should
explain the relationship among elements such as: Instruction Processor,
Microsequencer, Microengine, Memory, Cache, Memory Mapping or Address
Translation Unit, I/0 devices and interfaces.

12. Describe the hardware isolation mechanisms for the process memory
(e.g., rings, seg-ments, privilege levels).

13. (a) Provide a description of the hardware process address space. (b)
When and ┐ how is it formed? (d) How does the software use this mechanism,
if it does at all?

2.4 SOFTWARE

The TCB software consists of the elements that are involved in enforcing
the system security policy. Examples of TCB elements include: kernel,
interrupt handlers, process manager, 1/0 handlers, 1/0 manager,
user/process interface, hardware, and command languages/interfaces (for
system generation, operator, administrator, users, etc.). The security
kernel consists of the hardware, firmware and software elements of the TCB
that are involved in implementing the reference monitor concept, i.e., the
ones that mediate all access to objects by subjects.

C1:

1. Provide a (a) description and (b) architecture of the Trusted Computing
Base (TCB) at the element level (see above for examples of elements).

2. Describe the interface between the TCB and user processes that are
outside the TCB.

3. Describe the hardware ring/domain/privilege level/memory
segment/physical location where each TCB element resides.

4. Describe the hardware ring/domain/privilege level/memory
segment/physical location where the user processes reside.

5. (a) List software mechanisms that are used to isolate and protect the
TCB. (b) Provide a brief description of each mechanism.

6. List all the privileges a process can have. Include the privileges
based on the process or user profile, process or user name, or process or
user identification.

7. How are a process's privileges determined?

8. (a) List the process states and (b) briefly state conditions under
which a transition from one state to another occurs.

9. Briefly describe process scheduling.

10. Describe all interprocess communications mechanisms.

11. (a) Describe the file management system. This should include the
directory hierarchy, if any, directory and file attributes. (b) Also
identify all system directories and files and ┐ their access attributes.

12. How are (a) I/0 devices and (b) their queues (if any) managed?

13. How are the (a) batch jobs and (b) their queues managed?

14. What software engineering tools and techniques were used for the TCB
design and implementation?

C2:

15. Describe the interfaces (control and data flow) among the TCB
elements.

16. Describe the interface between the kernel and the rest of the TCB
elements.

17. Describe how the process states are manipulated by the TCB.

18. (a) Describe the data structures for a process context. Describe both
(b) hardware and ┐ software mechanisms used to manipulate/switch the
process context.

B1:

19. (a) List software mechanisms that are used to isolate and protect user
processes. (b)

Provide a brief description of each mechanism.

20. (a) Describe various elements of the process address space and (b)
their location in terms of ring/domain/privilege level/segment/physical
memory.

21. How is a process' sensitivity level determined?

B2:

22. How was the modularity requirement achieved and implemented?

23. (a) For each TCB element, identify protection-critical portions of the
code. (b) Describe the protection-critical functions performed by the
code.

24. (a) Is the TCB layered? (b) If yes, how many layers are in the TCB?
Provide a brief description of ┐ modules and (d) functions in each layer.
(e) How are the lower layers protected from higher layers?

B3:

25. How does the architecture limit or restrict the ability of untrusted
code to exploit covert channels?

26. How is the least privilege requirement achieved and implemented?

27. (a) For each TCB element, identify non-protection-critical portions of
the code. (b)

Explain why the code is part of the TCB.

28. How was the data abstraction and information hiding requirement
achieved and im-plemented?

2.5 DISCRETIONARY ACCESS CONTROL

C1:

1. What mechanisms are used to provide discretionary access controls?
(Examples of mechanisms are: access control lists, protection bits,
capabilities, etc.)

2. (a) Can the access be granted to the users on an individual user basis?
(b) If so, how?

3. (a) How is a group defined? (b) What mechanisms are used to administer
groups (i.e., to create or delete groups or to add or delete individual
users from a group)? ┐ Who can invoke these mechanisms? (d) What
privileges are necessary to invoke these mechanisms?

4. How can the access be revoked on an individual user basis?

5. How can the access be revoked on a group basis?

6. List any objects that can be accessed by users excluded from the DAC
policy (e.g.,

IPC files, process signaling/synchronization flags) ?1

7. For each TCB object identified in question 1, section 2.2, describe the
DAC mechanism which protects that object.

8. (a) List the access modes supported by the system (e.g., read, write,
delete, owner, execute, append). (b) Briefly describe the meaning of each
access mode for each object.

9. (a) Are conflicts between user and group access detected? (b) If so,
how are the conflicts resolved?

10. For each object, list when changes in DAC permissions become
effective.

C2:

11. (a) Can access be granted to groups of individuals? (b) If so, how?

12. (a) What are the initial access permissions when an object is created?
(b) Can the initial access permission be changed? If so, ┐ by whom (e.g.,
user/owner, system administrator, others) and (d) how.

13. (a) Can different initial access permissions be specified for
different users, or is this is a system-wide setting? If the former, (b)
by whom and ┐ how?

1This question is not applicable above class BI, because then all objects
have to be protected.

14. (a) Who can grant the access permissions to an object after the.object
is created?

(Examples include creator, current owner, system administrator, etc.) (b)
How is the permission granted?

15. (a) Can the ability to grant permissions be passed to another user? If
so, (b) by whom and ┐ how? (d) Under what circumstances can the previous
owner of the privilege retain it?

B3:

16. (a) Can access be denied to the users on an individual user basis,
i.e., exclude individual users? (b) If so, how?

17. (a) Can access be denied to groups of individuals? (b) If so, how?

2.6 IDENTIFICATION & AUTHENTICATION

C1:

1. (a) Does the system require the users to provide identification at
login? (b) If yes, what information is requested by the system?

2. Is there any additional device or physical security required for user
identification and authentication (I&A) (e.g., terminal ID, pass key,
smart card, etc.)?

3. (a) Does the system authenticate this identity at the time of login?
(b) If yes, what information is requested by the system? ┐ How does the
system use this information to authenticate the identity?

4. (a) Describe the algorithms used in user authentication. (b) Where in
the system are the code and data for authentication (e.g., user/password
data base) stored?

5. How are the authentication code and data protected?

6. (a) Does the I&A process associate privileges with the user? If so, (b)
what and ┐ how?

C2:

7. Describe how each user is uniquely identified.

B1:

8. How does the I&A process associate a sensitivity level with the user?

2.7 OBJECT REUSE

C2:

1. How is reuse of data in the storage resources (e.g., memory page cache,
CPU registers, disk sectors, magnetic tapes, removable disk media,
terminals) of the system prevented? (Examples include writing predefined
patterns, writing random patterns, preventing reading before writing,
etc.)

2. When do these actions take place: prior to allocation or after
deallocation and/or release?

3. Describe the TCB (a) hardware, (b) software and ┐ procedural mechanisms
used to accomplish the clearing for each type of storage resource.

4. Is it possible to read data that have been "logically" deleted, but not
physically removed (e.g., attempting to read past the end-of-file mark)?

2.8 AUDIT

C2:

1. Provide a brief description (preferably in block diagram form) of audit
data flow in terms of how the data are created, transmitted, stored, and
viewed for analysis.

2. How are the audit logs protected?

3. (a) How can the audit log be read? (b) Who can invoke these mechanisms?
┐ What privileges are required to invoke these mechanisms?

4. (a) What tools are available to output raw or processed (i.e., analyzed
and reduced) audit information? (b) Who can invoke these tools? ┐ What do
the tools do in terms of audit data reduction? (d) What are the formats of
the reports/outputs generated by these tools?

5. (a) How can the audit log be written or appended? (b) Who can invoke
these mechanisms? ┐ What privileges are required to invoke these
mechanisms?

6. (a) How can the audit log be deleted? (b) Who can invoke these
mechanisms? ┐

What privileges are required to invoke these mechanisms?

7. What are the internal formats of audit records?

8. Provide a list of auditable events (examples include attempted logins,
logouts, creation of subjects, deletion of subjects, assignment of
privileges to subjects, change of subject privileges, use of privileges by
subjects, creation of objects, deletion of objects, initial access to
objects (introduction of the object into a user's address space),
assumption of the role of security administrator).

9. (a) Which actions by the trusted users are auditable? (b) Which are
not? (Examples of trusted users are system operator, account
administrator, system security officer/administrator, auditor, system
programmer, etc. Trusted users almost always have at least one privilege.)

10. (a) What data are recorded for each audit event? (b) Which of the
following data (if any) are not recorded for each event: date, time, user,
object, object DAC information (e.g., ACL), type of event, invoked or not
invoked, why not invoked, success or failure in execution,terminal
identification?

11. (a) Can the password ever become part of the audit record? (b) If yes,
under what circumstances can this occur?

12. (a) What mechanisms are available to designate and change the
activities being audited? (b) Who can invoke these mechanisms? ┐ What
privileges are needed to invoke these mechanisms?

13. (a) What mechanisms are available for selective auditing (i.e.,
selection of events, subjects, objects, etc., to be audited)? (b) What
parameters (e.g., individual or group of subjects, individual objects,
subjects within a sensitivity range, objects within a sensitivity range,
event type) or combination of parameters can be specified for the
selective auditing? ┐ Who can invoke these mechanisms? (d) What privileges
are needed to invoke these mechanisms?

14. When do changes to the audit parameters take effect (e.g., immediately
for all processes, for new processes)?

15. (a) Are the audit reduction tools part of the TCB? (b) If not, what
trusted mechanism is used to view/output the audit log?

16. (a) Does the system produce multiple audit logs? (b) If yes, what
tools, techniques and methodologies are available to correlate these logs?

17. (a) Who (e.g., operator, system administrator or other trusted user)
is notified when the audit log gets full? (b) What options are available
to handle the situation ?

18. What other action does the TCB take when the audit log becomes full
(e.g., halt the system, do not perform auditable events, overwrite oldest
audit log data).

19. (a) In the worst case, how much audit data can be lost (e.g., when
audit log overflows, system goes down with audit data in memory buffers)?
(b) Describe the worst case scenario. ┐ When can it occur?

BI:

20. Which of the following events auditable: change in the device
designation of single-level or multilevel, change in device level, change
in device minimum or maximum level, override of banner page or page top
and bottom markings?'

21. Are the (a) subject and (b) object sensitivity level recorded as part
of the audit event?

B2:

22. Are events that exploit covert storage channels auditable?

B3:

23. How does the TCB (a) designate and (b) change the occurrence or
accumulation of events that require real-time notification? ┐ Who can
invoke these mechanisms? (d) What privileges are needed to invoke these
mechanisms? (e) Who (e.g., system administrator, president of the company)
gets the real-time notification? (f) What actions/options are available to
the individual being notified? What does the TCB do about (g) the event
and (h) the process that caused this alert?

2.9 LABELS

BI:

1. (a) How many hierarchical sensitivity classifications (such as
unclassified, confidential, secret, top secret), does your system provide
for? (b) What mechanisms are available to define the internal/storage and
external/print format? ┐ What mechanisms are available to change them? (d)
Who can invoke these mechanisms?

2. (a) How many non-hierarchical sensitivity categories (such as FOUO)
does your system provide for? (b) What mechanisms are available to define
the internal/storage and external/print format? ┐ What mechanisms are
available to change them? (d) Who can invoke these mechanisms?

3. (a) What is the internal TCB storage format of the sensitivity label?
(b) If different for different subjects or objects, give all formats.

4. For each type of subject, where is the subject sensitivity label
stored?

5. For each type of object, where is the object sensitivity label stored?

6. (a) List any subjects and objects that are not labeled. (b) Why are
they not labeled?

How are these subjects and objects ┐ accessed and (d) controlled?

7. (a) How is imported data labeled? (b) How is this label determined? Is
a human being involved in ┐ the determination or (d) the actual labeling?
(e) If so, what is the role of the person involved (e.g., system
administrator, system operator)? (f) Does the labeling require special
privileges? (g) If so, what are those privileges?

8. (a) Who can change the labels on a subject? (b) How?

9. (a) Who can change the labels on an object? (b) How?

10. How are the labels associated with objects communicated outside the
TCB?

11. (a) How does the system designate each device to be single-level or
multilevel? (b)

List the ways this designation can be changed. ┐ List the users who can
perform this designation.

12. (a) How does the TCB designate the sensitivity level of a single-level
device? (b) List the ways this designation can be changed. ┐ List the
users who can do this.

13. (a) How does the TCB export the sensitivity label associated with an
object being exported over a multilevel device? (b) What is the format for
the exported label? ┐ How does the TCB ensure that the sensitivity label
is properly associated with the object?

14. (a) What mechanisms are available to specify the human-readable print
label associated with a sensitivity label? (b) Who can invoke these
mechanisms?

15. (a) Is the beginning and end of each hardcopy output marked with the
human-readable print label representing the sensitivity level of the
output (i.e., does each hardcopy output have banner pages)? (b) What
happens if a banner page output is longer and/or wider than a physical
page?

16. (a) Is the top and bottom of each hardcopy output page marked with the
human-readable print label representing the sensitivity level of the
output? (b) What happens if the print label is wider and/or longer than
the space available for the top and/or the bottom?

17. How does the TCB mark the top and bottom page of non-textual type of
output such as graphics, maps, and images?

18. (a) How can the top and bottom page markings be overridden? (b) Who
can override the markings?

19. How can an operator distinguish the TCB-generated banner pages from
user output?

B2:

20. (a) How does the TCB acknowledge a change in the sensitivity level
associated with an interactive user? (b) Is the user notification posted
on the user terminal? ┐ How immediate is this change?

21. (a) How does a user query the system TCB for his or her current
sensitivity label? (b)

What part of the sensitivity label is output? ┐ Where is this output
posted?

22. (a) How does the TCB designate the minimum and maximum sensitivity
levels of a device? (b) List the ways these designations can be changed. ┐
List the users who can invoke these mechanisms.

23. List the circumstances under which the TCB allows input or output of
data that fall outside a device's sensitivity range.

2.10 MANDATORY ACCESS CdNTROL

BI:

1. Define the MAC policy for the possible access modes such as read,
write, append, delete.

2. (a) Does the system use sensitivity labels to enforce the MAC? (b) If
not, what information is used to make the MAC decisions?

3. (a) List the subjects, objects, and circumstances under which the MAC
policy is not enforced.2 (b) Why is it not enforced in these cases?

4. In what sequence does the system perform access mediation? (An example
sequence might be a. check for privileges that supersede MAC and DAC, then
b. check for DAC, then c. check for MAC.)

5. (a) Does the TCB support system-low and system-high sensitivity levels?
If yes, how can they be (b) designated and ┐ changed? Who can invoke the
functions to (d) designate and (e) change them? How are these levels used
by the system in (f) various labeling functions and (g) MAC decisions?

This question is not applicable above class BI, because then all objects
have to be protected.

2.11 TESTING

CI:

1. (a) What routines are available to test the correct operation of the
system hardware and firmware? (b) What elements of the system hardware are
tested through these routines? ┐ What elements of the system firmware are
tested through these routines? (d) What elements of the system hardware
and firmware are not tested through these routines? (e) Does the testing
include boundary and anomalous conditions? (f) Is the emphasis on
diagnosing and pinpointing faults or is it on ensuring the correct
operation of the system hardware and firmware?

2. (a) How are the routines in the previous question invoked? (b) Who can
invoke these routines? ┐ Do they run under the control of the operating
system or do they run in stand-alone mode?

3. (a) When can these routines be run? (b) When should these routines be
run? ┐ If they run automatically, when do they run (e.g., powerup,
booting, rebooting)?

4. Describe the software development testing methodology. In this
description, include a discussion of various testing steps such as unit,
module, integration, subsystem, system testing. This discussion should
include a description of test coverage criteria and test cases development
methodology.

5. Provide (a) a copy of the security test plan, a brief description of
its contents, or an annotated outline. (b) Does the test plan include the
following information: system configuration for testing, procedures to
generate the TCB, procedures to bring up the system, testing schedule,
test procedures, test cases, expected test results? ┐ Provide a schedule
for development of the security test plan if such a test plan doesn't
already exist.

6. (a) How thorough is the security testing? (b) Do the test cases include
nominal, boundary, and anomalous values for each input? ┐ What about the
combinations of inputs? (d) Describe the test coverage criteria.

7. (a) How are the test cases developed? (b) Are they based on the concept
of functional testing, structural testing, or a combination of the two?

8. What tools and techniques (automated, manual, or a combination of the
two) will be used to do the functional and/or structural analysis in order
to develop a thorough set of test cases?

B1:

9. How do you plan to ascertain that errors have been minimized in the
system?

B2:

10. What is the role of the descriptive top-level specification (DTLS) in
the functional and/or structural analysis done in order to develop a
thorough set of test cases?

11. (a) Do you plan to develop scenarios for penetration testing? (b) If
so, what methodologies will be used?

12. How do you plan to compute and verify the bandwidths of covert
channels?

Al:

13. What is the role of the formal top-level specification (FTLS) in the
functional and/or structural analysis done in order to develop a thorough
set of test cases?

2.12 MODELING AND ANALYSIS

B1:

1. Describe the system security policy.

2. How is the system security policy represented in the informal model?

3. What policies are represented in the informal model (e.g., MAC, DAC,
privileges, other protection mechanisms, object reuse )?

4. What tools, techniques and methodologies are used to demonstrate the
model consis-tent with its axioms?

B2:

5. (a) Provide a copy of the Verification Plan, a brief description of its
contents, or an annotated outline. (b) Provide a schedule for completion
of the Verification Plan.

6. What tools, techniques and methodologies are used to represent the
formal model of the system security policy?

7. What policies are represented in the formal model (e.g., MAC, DAC,
privileges, other protection mechanisms, object reuse)?

8. What tools, techniques and methodologies are used to prove the model
consistent with its axioms?

9. (a) What tools, techniques and methodologies are used to represent the
descriptive top-level specification (DTLS)? (b) What portions of the TCB
are represented by the DTLS?

10. What tools, techniques and methodologies are used to identify,
analyze, calculate, and reduce the bandwidths of covert channels?

B3:

11. What tools, techniques and methodologies are used to show that the
DTLS is consistent with the formal security policy model?

12. (a) What tools, techniques and methodologies are used to represent the
formal top-level specification (FTLS)? (b) What portions of the TCB are
represented by the FTLS?

13. What tools, techniques and methodologies are used to verify or show
that the FTLS is consistent with the formal security policy model?

14. What tools, techniques and methodologies are used to identify the
implemented code modules that correspond to the FTLS?

15. What tools, techniques and methodologies are used to show that the
code is correctly implemented vis-a-vis the FTLS?

2.13 OTHER ASSURANCES

Although the configuration management criteria do not appear until class
B2 in the TCSEC, the questions pertaining to configuration management
below are relevant to all classes because of the NSA's Ratings Maintenance
Phase (RAMP) program.

C1:

1. (a) Describe the Configuration Management (CM) system in place in terms
of organizational responsibilities, procedures, and tools and techniques
(automated, manual, or a combination of the two). (b) Describe the version
control or other philosophy to ensure that the elements represent a
consistent system, i.e., object code represents the source code, and the
design documentation accurately describes the source code. ┐ If the CM
system is different for some of the elements listed in question 1 in
section 2.4, answer this question for each of the elements.

2. (a) When was this system placed under configuration management? (b)
Provide the approximate date, as well as the life-cycle phase (e.g.,
design, development, testing). Answer this question for each system
element so controlled (as listed in the previous question).

3. List the elements that are and are not under the Configuration
Management (e.g., hardware, firmware, formal security policy model, FTLS,
DTLS, design data and documentation, source code, object code, test plans,
Security Features User's Guide, Trusted Facilities Manual).

4. Describe the protection mechanisms in place to safeguard the CM
elements.

5. (a) List separately the functions that can be performed by each of the
trusted users (e.g., operator, security administrator, accounts
administrator, auditor, systems programmer). (b) For each of these
persons/roles, list the system data bases that can be accessed and their
access modes. ┐ Also list the privileges provided to each of these roles.

6. (a) How does the TCB recognize that a user has assumed one of the
above-mentioned trusted roles? (b) Which of the above-mentioned functions
can be performed without the TCB recognizing this role?

7. (a) Does the system have a degraded mode of operation? (b) What can
cause this to occur? ┐ How long can the system keep running in this mode?
(d) How does an operator get the system back to full operation? (e) What
security-related services are provided in the degraded mode? (f) What
security-related services are not provided?

B2:

8. Describe the version control or other philosophy to ensure that the
object code cor-responds to the correct source code, which in turn is
accurately abstracted in the DTLS.

9. (a) When (e.g., before user authentication) and (b) how (e.g., by
typing a specific control character sequence) can the trusted path be
invoked by the user? ┐ What TCB elements are involved in establishing the
trusted path?

10. How does the TCB ensure that the trusted path is unspoofable?

11. How do you plan to show consistency between the DTLS and the code?

B3:

12. What security relevant actions are able to be performed under trusted
path?

13. Are there other system interfaces which support the same functionality
as provided in the trusted path?

14. (a) How does the system recovery work? What system resources (e.g.,
memory, disks blocks, files) are protected (b) prior to and ┐ during the
system recovery? (d) How are they protected? (e) What resources are not
protected?

Al:

15. Describe the version control or other philosophy which ensures that
the FTLS continues to accurately describe the system through system
changes.

16. How do you plan to show consistency among the FTLS, DTLS and the code?

17. Describe the tools, techniques and procedures used to ensure the
integrity of the TCB elements (hardware, firmware, software, documents,
etc.) supplied to the customers (e.g., trusted courier, electronic seals,
physical seals).

2.14 OTHER DOCUMENTATION

C1:

1. (a) Describe the methodology used in the design of the system. (b)
Provide a list of documents that capture the system design. ┐ For each
document, provide a copy, a brief description of its contents, or an
annotated outline. (d) Provide a schedule for development of the design
documents.

2. Does the SFUG describe (a) the protection mechanisms provided by the
TCB, (b) guidelines on their use, and ┐ how they interact?

3. Does the SFUG explain to users the underlying philosophy of protection
for the system?

4. Does the SFUG discuss the need for exercising sound security practices
in protecting the information processed and/or stored in the system,
including all input and output?

5. Does the SFUG describe users' responsibilities with respect to assuring
the effectiveness of the protective features (e.g., password selection and
protection)?

6. Does the SFUG describe security-related commands available to users?

7. Does the SFUG explain how to use the DAC mechanism(s) provided by the
system to protect objects?

8. Does the SFUG explain how removable media are to be handled (if
applicable)?

9. Does the SFUG discuss the auditing of security-relevant events?

10. Does the SFUG include and clearly highlight warnings where needed?

11. (a) Does the TFM ~~ontain procedures to configure the secure system?
(b) Does it list the devices and hardware elements that are part of the
evaluated configuration? Does it contain procedures ┐ for configuring each
of the devices, (d) for connecting them, and (e) for configuring the
entire system? (f) Does it list the devices that are not part of the
evaluated configuration? (g) Does it list the procedures for securely
configuring them out and for disconnecting them?

12. Does the TFM list the (a) functions, (b) privileges, and ┐ data bases
that are to be controlled? (d) Does it describe how these are controlled?
(e) Does it describe the consequences of granting access to them as
warnings?

13. (a) Does the TFM contain the procedures and warnings relating to the
secure operation of the computing facility? (b) Does it address the
physical, personnel, and administrative aspects of security in order to
ensure the protection of computing hardware, firmware, software, and
privileged devices such as the operator terminals?

27

14. Does the TFM contain the procedures for securely
starting/booting/initializing the system?

C2:

15. (a) Does the TFM provide procedures for maintaining the audit log? (b)
Does it describe how ihe audit log can be turned on, turned off, combined
with other audit logs, and backed up? ┐ Does it describe how to detect
that the audit log is getting full, or is full, and what actions to take
in order to minirnize the loss of audit data?

16. Does the TFM contain the (a) structure of the audit log file and the
(b) format of the audit records? ┐ Does it describe how the audit records
can be viewed? Does it (d) describe the capabilities of the audit
reduction tool, (e) how to invoke these capabilities, and (f) the format
of the tool output?

BI:

17. Does the TFM address the protection of hard-copy outputs?

18. (a) Does the TFM provide a list of trusted users (e.g., system
operator, security administrator, accounts administrator, auditor) and
trusted processes (device queue manipulation, user profile editor)? (b)
For each trusted user or process, does it list the functions (e.g.,
creating and deleting users, changing user security profile, setting up
defaults for discretionary and mandatory access controls, selecting
auditing events), privileges, and data bases (e.g., user security
profiles, authentication data base) to be accessed?

B2:

19. (a) Does the TFM contain procedures to generate the TCB from source
code? (b)

For each system parameter or input, does the TFM list valid values for a
secure TCB generation?

20. Does the TFM include a list of TCB modules that make up the security
kernel?

21. Are the separate operator and administrator functions clearly
identified and described?

B3:

22. Does the TFM contain the procedures for secureJy restarting/resuming
the system after a lapse in system operation, or a system failure?

28

Chapter 3

GLOSSARY

Access A specific type of interaction between a subject and an object that
results in the flow of information from one to the other.

Access List A list of users, programs, and/or processes and the
specifications of access categories to which each is assigned.

Administrative User A user assigned to supervise all or a portion of an
ADP system.

Audit To conduct the independent review and examination of system records
and activities.

Audit Trail A chronological record of system activities that is sufficient
to enable the reconstruction, reviewing, and examination of the sequence
of environments and activ-ities surrounding or leading to an operation, a
procedure, or an event in a transaction from its inception to final
results.

Auditor An authorized individual, or role, with administrative duties,
which include selecting the events to be audited on the system, setting up
the audit flags that enable the recording of those events, and analyzing
the trail of audit events.

Authenticate (l) To verify the identity of a user, device, or other entity
in a computer system, often as a prerequisite to allowing access to
resources in a system. (2) To verify the integrity of data that have been
stored, transmitted, or otherwise exposed to possible unauthorized
modification.

Authenticated User A user who has accessed an ADP system with a valid
identifier nd authentication combination.Authorization The granting of
access rights to a user, program, or process.

Bandwidth A characteristic of a communication channel that is the amount
of information that can be passed through it in a given amount of time,
usually expressed in bits per second.

Bell-LaPadula Model A formal state transition model of computer security
policy that describes a set of access control rules. In this formal model,
the entities in a computer system are divided into abstract sets of
subjects and objects. The notion of a secure state is defined, and it is
proven that each state transition preserves security by moving from secure
state to secure state, thereby inductively proving that the system is
secure. A system state is defined to be "secure" if the only permitted
access modes of subjects to objects are in accordance with a specific
security policy. In order to determine whether or not a specific access
mode is allowed, the clearance of a subject is compared to the
classification of the object, and a determination is made as to whether
the subject is authorized for the specific access mode. The
clearance/classification scheme is expressed in terms of a lattice. See
Star Property (*-property) and Simple Security Property.

Channel An information transfer path within a system. May also refer to
the mechanism by which the path is effected.

Covert Channel A communication channel that allows an untrusted subject
with legitimate access to information to transfer that information in a
manner that violates the system's security policy, using a mechanism in
some way not intended by the system developers.

Covert Storage Channel A covert channel that involves the direct or
indirect writing of a storage location by one process and the direct or
indirect reading of the storage location by another process. Covert
storage channels typically involve a finite resource (e.g., sectors on a
disk) that is shared by two subjects at different security levels.

Covert Timing Channel A covert channel in which one process signals
information to another by modulating its own use of system resources
(e.g., CPU time) in such a way that this manipulation affects the real
response time observed by the second process.Coverage Analysis Qualitative
or quantitative assessment of the extent to which the test conditions and
data show compliance with required properties (e.g., security model and
TCB primitive properties). See: Test Condition, Test Data, Security Policy
Model.Data Information with a specific physical representation.

Data Integrity The property that data meet an a priori expectation of
quality.

Degauss To reduce magnetic flux density to zero by applying a reverse
magnetizing field.

Descriptive Top-Level Specification (DTLS) A top-level specification that
is written in a natural language (e.g.,English), an informal program
design notation, or a combination of the two.

Discretionary Access Control (DAC) A means of restricting access to
objects based on the identity and need-to-know of the user, process and/or
groups to which they belong. The controls are discretionary in the sense
that a subject with a certain access permission is capable of passing that
permission (perhaps indirectly) on to any other subject.

Dominate Security level S1 is said to dominate security level S2 if the
hierarchical classification of S1 is greater than or equal to that of S2
and the non-hierarchical categories of S1 include all those of 52 as a
subset.

Exploitable Channel Any channel that is usable or detectable by subjects
external to the Trusted Computing Base whose purpose is to violate the
security policy of the system.

Flaw An error of commission, omission, or oversight in a system that
allows protection mechanisms to be bypassed.

Flaw Hypothesis Methodology A system analysis and penetration technique in
which specifications and documentation for the system are analyzed and
then flaws in the system are hypothesized. The list of hypothesized flaws
is prioritized on the basis of the estimated probability that a flaw
actually exists and, assuming a flaw does exist, on the ease of exploiting
it and on the extent of control or compromise it would provide. The
prioritized list is used to direct a penetration attack against the
system.

Formal Proof A complete and convincing mathematical argument, presenting
the full logical justification for each proof step, for the truth of a
theorem or set of theorems.

Formal Security Policy Model A mathematically precise statement of a
security policy. To be adequately precise, such a model must represent the
initial state of a system, the way in which the system progresses from one
state to another, and a definition of a "secure" state of the system. To
be acceptable as a basis for a TCB, the model must be supported by a
formal proof that if the initial state of the system satisfies the
definition of a "secure" state and if all assumptions required by the
model hold, then all future states of the system will be secure. Some
formal modeling tech-niques include: state transition models, temporal
logic models, denotational semantics models, algebraic specification
models.

Formal Top-Level Specification (FTLS) A top-level specification that is
written in a formal mathematical language to allow theorems showing the
correspondence of the system specification to its formal requirements ~o
be hypothesized and formally proven.

Formal Verification The process of using formal proofs to demonstrate the
consistency between a formal specification of a system and a formal
security policy model (design verification) or between the formal
specification and its program implementa-tion (implementation
verification).

Functional Testing The segment of security testing in which the advertised
mechanisms of a system are tested, under operational conditions, for
correct operation.

Identification The process that enables recognition of an entity by a
system, generally by the use of unique machine-readable user names.

Integrity Sound, unimpaired or perfect condition.

Internal Security Controls Hardware, firmware, and software features
within a system that restrict access to resources (hardware, software, and
data) to authorized subjects only (persons, programs, or devices).

Isolation The containment of subjects and objects in a system in such a
way that they are separated from one another, as well as from the
protection controls of the operating system.

Lattice A non-empty set X with a reflexive partial order such that for
every pair x,y of members X, there is a unique smallest element greater
than each x and y and a unique largest element that is smaller than each x
and y.

Least Privilege This principle requires that each subject in a system be
granted the most restrictive set of privileges (or lowest clearance)
needed for the performance of authorized tasks. The application of this
principle limits the damage that can result from accident, error, or
unauthorized use.

Mandatory Access Control (MAC) A means of restricting access to objects
based on the sensitivity (as represented by a label) of the information
contained in the objects and the formal authorization (i.e., clearance) of
subjects to access information of such sensitivity.

Multilevel Device A device that is used in a manner that permits it to
simultaneously process data of two or more security levels without risk of
compromise. To accomplish this, sensitivity labels are normally stored on
the same physical medium and in the same form (i.e., machine-readable or
human-readable) as the data being processed.

Object A passive entity that contains or receives information. Access to
an object potentially implies access to the information it contains.
Examples of objects are: records, blocks, pages, segments, files,
directories, directory tree, and programs, as well as bits, bytes, words,
fields, processors, video displays, keyboards, clocks, printers, network
nodes.

Object Reuse The reassignment and reuse of a storage medium (e.g., cage
frame, disk sector, magnetic tape) that once contained one or more
objects. To be securely reused and assigned to a new subject, storage
media must contain no residual data (magnetic remanence) from the
object(s) previously contained in the media.

Partial Ordering A partial order on a set X is a relation R having the
property that if (x,y) is in R and (y,z) is in R, then (x,z) is in R. A
partial order is reflexive if (x,x) is in R for each x in X.

Penetration The successful act of bypassing the security mechanisms of a
system.

Process A program in execution.

Protection-Critical Portions of the TCB Those portions of the TCB whose
normal function is to deal with the control of access between subjects and
objects. Their correct operation is essential to the protection of data on
the system.

Read A fundamental operation that results only in the flow of information
from an object to a subject.

Read Access (Privilege) Permission to read information.

Reference Monitor Concept An access-control concept that refers to an
abstract machine that mediates all accesses to objects by subjects.

Security Level The combination of a hierarchical classification and a set
of non-hierarchical categories that represents the sensitivity of
information.

Security Policy The set of laws, rules, and practices that regulate how an
organization manages, protects, and distributes sensitive information.

Security Policy Model A formal presentation of the security policy
enforced by the system. It must ideAtify the set of rules and practices
that regulate how a system manages, protects, and distributes sensitive
information. See Bell-LaPadula Model and Formal Security Policy Model.

Security-Relevant Event Any event that attempts to change tide security
state of the system, (e.g., change discretionary access controls, change
the security level of the subject, change user password). Also, any event
that attempts to violate the security policy of the system, (e.g., too
many attempts to log in, attempts to violate the mandatory access control
limits of a device, attempts to downgrade a file).

Security Testing A process used to determine that the security features of
a system are implemented as designed. This includes hands-on functional
testing, penetration testing, and verification.

Simple Security Property A Bell-LaPadula security model rule allowing a
subject read access to an object only if the security level of the subject
dominates the security level of the object. Also called simple security
condition.

Single-Level Device An automated information systems device that is used
to process data of a single security level at any one time.

Spoofing An attempt to gain access to a system by posing as an authorized
user. Synonymous with impersonating, masquerading or mimicking.

Star Property A Bell-LaPadula security model rule allowing a subject write
access to an object only if the security level of the object dominates the
security level of the subject. Also called confinement property,
*-property.

Subject An active entity, generally in the form of a person, process, or
device, that causes information to flow among objects or changes the
system state. Technically, a process/domain pair.

Subject Security Level A subject's security level is equal to the security
level of the objects to which it has both read and write access. A
subject's security level must always be dominated by the clearance of the
user the subject is associated with.

Terminal Identification The means used to provide unique identification of
a terminal to a system.

Test Condition A statement defining a constraint that must be satisfied by
the program under test.

Test Data The set of specific objects and variables that must be used to
demonstrate that a program produces a set of given outcomes.

Test Plan A document or a section of a document which describes the test
conditions, data, and coverage of a particular test of group of tests. See
also: Test Condition, Test Data, Coverage Analysis.

Test Procedure (Script) A set of steps necessary to carry; out one or a
group of tests. These include steps for test environment initialization,
test execution, and result analysis. The test procedures are carried out
by test operators.

Test Program A program which implements the test conditions when
initialized with the test data and which collects the results produced by
the program being tested.

Top-Level Specification A nonprocedural description of system behavior at
the most abstract level, typically, a functional specification that omits
all implementation details.

Trusted Computer System A system that employs sufficient hardware and
software integrity measures to allow its use for processing simultaneously
a range of sensitive or classified information.

Trusted Computing Base (TCB) The totality of protection mechanisms within
a computer system-including hardware, firmware, and software-the
combination of which is responsible for enforcing a security policy. It
creates a basic protection envi-ronment and provides additional user
services required for a trusted computer system. The ability of a trusted
computing base to correctly enforce a security policy depends solely on
the mechanisms within the TCB and on the correct input by system
ad-ministrative personnel of parameters (e.g., a user's clearance) related
to the security policy.

Trusted Path A mechanism by which a person at a terminal can communicate
directly with the Trusted Computing Base. This mechanism can only be
activated by the person or the Trusted Computing Base and cannot be
imitated by untrusted software. Person or process accessing an AIS either
by direct connections (i.e., via terminals), or indirect connections
(i.e., prepare input data or receive output that is not reviewed for
content or classification by a responsible individual).

Verification The process of comparing two levels of system specification
for proper correspondence (e.g., security policy model with top-level
specification, top-level spec-ification with source code, or source code
with object code). This process may or may not be automated.

Verification Plan A deliverable as specified in the Trusted Product
Evaluation Management Plan. It indicates how the system design will be
verified. It should include identification of the specification
language/system to be used, an indication of any spe-cial features of the
language that will be used, and the planned number of levels that
specifications will be written for. The method to be used for theorem
proving, either manual, interactive 6r automated, should be indicated. The
plan will be submitted to the team for review.

Write A fundamental operation that results only in the flow of information
from a subject to an object.

Write Access (Privilege) Permission to write an object.

Chapter 4

REFERENCES

1. Department of Defense, Trusted Computer System Evaluation Criteria, DoD
5200.28-STD, December 1985.

2. Department of Defense, Security Requirements for Automated Information
Systems (AISs), DoD Directive 5200.28, 21 March 1988.

3. Aerospace Report No. TOR-0086 (6777-25)1, Trusted Computer System
Eval-uation Management Plan, 1 October 1985.

4. National Computer Security Center, NCSC-TG-002 Version-I, Trusted
Prod-uct Evaluations - A Guide For Vendors, 1 March 1988(DRAFT).

5. National Computer Security Center, NCSC-TG-004 Version l, Glossary of
Computer Security Terms, 21 October 1988.

6. National Computer Security Center, NCSC-TG-013 Version I, Rating
Main-tenance Phase - Program Document, 23 June 1989.