Mic security model object
To use the Mic security model, you need to create an object or objects of this model. You also need to assign a set of integrity levels for subjects and resources.
A Mic security model object has the following parameters:
configrefers to a set of integrity levels or configuration of a set of integrity levels:degreesrefers to a set of gradations for generating a set of integrity levels.categoriesrefers to a set of categories for generating a set of integrity levels.
Examples:
policy object mic : Mic {
config = ["LOW", "MEDIUM", "HIGH"]
}
policy object mic_po : Mic {
config =
{ degrees : ["low", "high"]
, categories : ["net", "log"]
}
}
A set of integrity levels is a partially ordered set that is linearly ordered or contains incomparable elements. The set {LOW, MEDIUM, HIGH} is linearly ordered because all of its elements are comparable to each other. Incomparable elements arise when a set of integrity levels is defined through a set of gradations and a set of categories. In this case, the set of integrity levels L is a Cartesian product of the Boolean set of categories C multiplied by the set of gradations D:
The degrees and categories parameters in this example define the following set:
{
{}/low, {}/high,
{net}/low, {net}/high,
{log}/low, {log}/high,
{net,log}/low, {net,log}/high
}
In this set, {} means an empty set.
The order relation between elements of the set of integrity levels L is defined as follows:
According to this order relation, the jth element exceeds the ith element if the subset of categories E includes the subset of categories A, and gradation F is greater than or equal to gradation A. Examples of comparing elements of the set of integrity levels L:
- The {net,log}/high element exceeds the {log}/low element because the "high" gradation is greater than the "low" gradation, and the subset of categories {net,log} includes the subset of categories {log}.
- The {net,log}/low element exceeds the {log}/low element because the levels of gradations for these elements are equal, and the subset of categories {net,log} includes the subset of categories {log}.
- The {net,log}/high element is the highest because it exceeds all other elements.
- The {}/low element is the lowest because all other elements exceed this element.
- The {net}/low and {log}/high elements are incomparable because the "high" gradation is greater than the "low" gradation but the subset of categories {log} does not include the subset of categories {net}.
- The {net,log}/low and {log}/high elements are incomparable because the "high" gradation is greater than the "low" gradation but the subset of categories {log} does not include the subset of categories {net,log}.
For subjects and resources that have incomparable integrity levels, the Mic security model provides conditions that are analogous to the conditions that the security model provides for subjects and resources that have comparable integrity levels.
By default, data streams between subjects that have incomparable integrity levels are prohibited. However, you have the option to allow such data streams if you can guarantee that the subjects receiving data will not be compromised. A resource consumer is prohibited from writing data to a resource and read data from a resource if the integrity level of the resource is incomparable to the integrity level of the resource consumer. You have the option to allow the resource consumer to read data from a resource if you can guarantee that the resource consumer will not be compromised.
A Mic security model object can be covered by a security audit. There are no audit conditions specific to the Mic security model.
It is necessary to create multiple objects of the Mic security model in the following cases:
- You need to configure a security audit differently for different objects of the Mic security model (for example, you can apply different audit profiles or different audit configurations of the same profile for different objects).
- You need to distinguish between calls of methods provided by different objects of the Mic security model (audit data includes the name of the security model method and the name of the object that provides this method, so you can verify that the method of a specific object was called).
- You need to use multiple variants of mandatory integrity control that may have different sets of integrity levels for subjects and resources, for example.