YACRAF-calculator

This is a graphical tool for doing calculations according to YACRAF (https://link.springer.com/article/10.1007/s10207-023-00713-y) used in the KTH courses EP2790 and EP279V.

This tool allows calculations inherent to the threat modeling to be set up and calculated using graphical block diagrams, where one can place, drag, and connect different blocks across various Views. The aim of the tool is to allow for the: (i) automation of the calculation process, where any changes to any block automatically propagate through the system, and (ii) simulation of various scenarios.

Dependecies

The program utilizes Tkinter for its GUI and NumPy for its calculations. If not already installed, Tkinter can on Debian-based Linux distributions (such as Ubuntu) be installed using:

sudo apt install python3-tk

Meanwhile, NumPy can be installed using:

pip install numpy

How to use

Run the program using:

python3 main.py

The graphical interface consists of two types of Views: Configuration Views and Setup Views. Class blocks (for example, an attack event) and their Attributes (for example, the attack event's cost) are defined within Configuration Views, where one may also define connections or relationships between different Attributes. For instance, whether a specific Attribute takes other ones as input and what operation to perform between them. In practical terms, Configuration Views defines the metamodel used during the threat modeling. Meanwhile, Setup Views define the system-specific setup using the configured Class and how they connect/relate to each other.

Views

In the top right corner of the GUI are two columns of buttons, see (1) and (2) in the below figure. The figure shows a Configuration View. These buttons switch between the different Views where the left-most column switches between Configuration Views and the right-most between Setup Views. The button with the + allows for an additional View to be added. The current View can be configured by pressing E (for edit) when no block inside the View is selected (will edit the block otherwise), where one can:

1. Change its name
2. Switch their button order
3. Delete it

The Save button in the bottom left corner ((3) in the below figure) saves the current state of all Configuration Views and Setup Views. Any blocks in the Views can be deleted by pressing backspace when selected.

Configuration View

Class

A new metamodel Class is created by pressing the Add class button in the top left corner, as illustrated by (1) in the below figure. By pressig the (2), one can add an Attriubte to the created Class (result shown in (3)). Pressing an Attribute selects it, as shown by (4), where one can edit it by pressing E. Editing an Attribute allows the following to be configured:

1. Its name
2. Their displayed order
3. The value type of the Attribute, such as a single number or a triangle distribution
4. Hide it from the corresponding Setup Views, meaning it is only visible in the Configuration Views (useful for calculations requiring several steps)

Similarly, the Class itself can be also be edited, enabling:

1. Changing its name
2. Creating a linked copy of this instance to another Configuration View (allowing relations between blocks across Configuration Views), identified by a marker in their upper right corner

Calculation input

By pressing the Add input in the top left corner (see (5) in the above figure), an Input block is created (see (6)). Input blocks function take inputs from one or more Attributes and, through a specified mathematical operation, outputs the result to an adjacent Attribute that it has been dragged next to (see (7)). The Input block can be configured by selecting it and pressing E (see (8)), where one can:

1. Change its mathematical operation, for example AND, OR, multiplication, etc
2. Add a scalar that multiplies the calculated input with a factor (see (10))

Attributes can be added as inputs (connecting them) to the Input block by first right clicking on the corresponding Attribute and then left or right clicking the Input block, creating a Connection between the two, as shown by (9) in the above figure.

Connection

Pressing E when the corner of a Connection is selected opens up its configuration, where one can:

1. Set the Connection as external, meaning it will only be connected to Attributes of other class instances, ignoring connected internal Attributes, such as an attack event only considering the input of another attack event and not that of itself Attribute (indicated by its lines becoming dashed)

The corners can be dragged around to customize the path of the Connection.

Setup View

Shown in the below figure is an example of a Setup View representing the system which the metamodel from the Configuration Views has been applied to. The buttons at (1) in the below figure are used to create Connections between the Classes and calculate the final values, respectively. (2) shows buttons for running custom scripts that can calculate/simulate different scenarious throughout the Setup Views. Scripts are explained later.

Class

An instance of a Class from a Configuration View can be added to the current Setup View by pressing the corresponding button in the top left corner, as shown by (1) in the Setup View in the below figure. The Class instances can be configured by pressing E when selected, where one can:

1. Change the name of the corresponding Class instance
2. Create a linked copy of the instance to another Setup View (any calculated value takes all linked versions into account), identified by a marker in their upper right corner

Connection

Pressing the Connection button at the top ((3) in the above figure) creates a directional Connection that can be attached to Classes by dragging its corresponding ends. The Attributes of the Class that the Connection points to may take input from the other Class, if such a relation has been configured in the Configuration Views. Attaching a Connecton to a Class will automatically disable Attribute entries if the corresponding value is dependent on at least one connected Class. By pressing E after selecting a corner on the directional Connection, one can configure it by:

1. Adding scalar(s) that is applied to input values from the Connection, where the appearing indicator (see (6)) can be dragged along the path of the Connection

Calculate

The calculate button at the top (see (7)) calculates the values of all Attributes that do not have an input entry field. Calculated are the Attributes of all Classes in all Setup Views. In the case of the above figure, the Attribute indicated by (8) has been calculated using the corresponding Attribute values of its input Classes. The input Attributes in question are highlighted when selecting an Attribute.

Scripts

Scripts to visualize or simulate different scenarios, such as finding the most optimal order of implementing defense mechanisms, or enumerating and visualising the several of the easiest attack paths, can be created using Python scripts that interface to the tool. To create a script, go to the scripts directory.