Before reading this chapter, a few key terms must be explained. This will hopefully
clear up any confusion that may occur and avoid the abrupt introduction of new terms and
information.
compartment: A compartment is a
set of programs and data to be partitioned or separated, where users are given explicit
access to specific components of a system. Also, a compartment represents a grouping,
such as a work group, department, project, or topic. Using compartments, it is possible
to implement a need-to-know security policy.
high water mark: A high water
mark policy is one which permits the raising of security levels for the purpose of
accessing higher level information. In most cases, the original level is restored after
the process is complete. Currently, the FreeBSD MAC
framework does not have a policy for this, but the definition is included for
completeness.
integrity: Integrity, as a key
concept, is the level of trust which can be placed on data. As the integrity of the data
is elevated, so does the ability to trust that data.
label: A label is a security
attribute which can be applied to files, directories, or other items in the system. It
could be considered a confidentiality stamp; when a label is placed on a file it
describes the security properties for that specific file and will only permit access by
files, users, resources, etc. with a similar security setting. The meaning and
interpretation of label values depends on the policy configuration: while some policies
might treat a label as representing the integrity or secrecy of an object, other policies
might use labels to hold rules for access.
level: The increased or
decreased setting of a security attribute. As the level increases, its security is
considered to elevate as well.
low water mark: A low water mark
policy is one which permits lowering of the security levels for the purpose of accessing
information which is less secure. In most cases, the original security level of the user
is restored after the process is complete. The only security policy module in FreeBSD to
use this is mac_lomac(4).
multilabel: The multilabel property is a file system option which can be set in
single user mode using the tunefs(8) utility,
during the boot operation using the fstab(5) file, or
during the creation of a new file system. This option will permit an administrator to
apply different MAC labels on different objects. This
option only applies to security policy modules which support labeling.
object: An object or system
object is an entity through which information flows under the direction of a subject. This includes directories,
files, fields, screens, keyboards, memory, magnetic storage, printers or any other data
storage/moving device. Basically, an object is a data container or a system resource;
access to an object effectively
means access to the data.
policy: A collection of rules
which defines how objectives are to be achieved. A policy usually documents how certain items are to be handled.
This chapter will consider the term policy in this context as a security policy; i.e. a collection of rules which will
control the flow of data and information and define whom will have access to that data
and information.
sensitivity: Usually used when
discussing MLS. A sensitivity level is a term used to
describe how important or secret the data should be. As the sensitivity level increases,
so does the importance of the secrecy, or confidentiality of the data.
single label: A single label is
when the entire file system uses one label to enforce access control over the flow of
data. When a file system has this set, which is any time when the multilabel option is not set, all files will conform to the same
label setting.
subject: a subject is any active
entity that causes information to flow between objects; e.g. a user, user processor, system process, etc. On
FreeBSD, this is almost always a thread acting in a process on behalf of a user.
