Protection, Pt. 1

Question 1

Principle of Least Privilege

Answer 1

Programs, users, and systems should be given just enough privileges to perform their tasks

Question 2

Need to Know Principle

Answer 2

At any time, a process should be able to access only those resources that it currently requires to complete its task

Question 3

Policies vs. Mechanisms

Answer 3

• Policies decide what should be done

- Mechanisms decide how it should be done

Question 4

A process operates within a…

Answer 4

…protection domain

Question 5

Access Rights

Answer 5

Object name, rights set (subset of all valid operations that can be performed on object)

Question 6

Static Association

Answer 6

• Process remains in its domain forever

- Difficult to maintain Need to Know Principle

Question 7

Dynamic Association

Answer 7

Processes can switch from one domain to another to access objects or perform needed operations

Question 8

What can be a Domain?

Answer 8

• Each user is a domain (domain switching is switching the user)
• Each process is a domain (domain switching is message passing between processes)
• Each procedure is a domain (domain switching is procedure calls)

Question 9

Access Matrix

Answer 9

• Rows represent domains, columns represent objects

- Entry(i,j) defines the set of operations that a process in domain i can invoke on object j

Question 10

Domain Switching in a Matrix

Answer 10

• Consider domains as objects (add them to access matrix)

- Write switches on these domains

Question 11

Dynamic Protection with a Matrix

Answer 11

Change entries of the access matrix dynamically (need to add/remove/copy access rights)

Question 12

Special Access Rights

Answer 12

• Copy (can copy the access right R within the same column, denoted as R*)
• Owner (can add/remove access rights to object i in column j)
• Control (can add/remove access rights to domain i in row j