Computer Security: Art and Science by Matt Bishop. ISBN:978-0321712332 Chapter 2
ID: 657744 • Letter: C
Question
Computer Security: Art and Science by Matt Bishop. ISBN:978-0321712332
Chapter 26 Page 799
Section 26.2.2. Augment the matrix with the change right. This right allows the user to alter the classes of other users in that category. For example, if user Amy had change rights over the class "developers," she could change the class of user Tom, who is currently in the "developers" class, to any of the other four classes.
A)Let Alice be a member of the SSO class, and let her have change rights over the "developers" and "employees" classes. Let Bob be a member of the SSO class, with change rights over "outsiders" and "employees." Redraw the matrix for this situation and write rules describing the allowed transformations of the matrix.
B)Describe any problems that might occur if Alice and Bob were not careful about the changes of classes they made. Could information leak in undesired ways? If so, give an example. If not, show why not.
C)Should members of the SSO class be allowed to apply the change right to members of that class? Justify your answer. In particular, state what damage could occur if this were allowed, and if it were not allowed.
Explanation / Answer
A) Augmented matrix
The transformation rules are :-
B) If Alice and Bob are not careful about the changes they made then it can lead to information leakage and unauthorized data modification.
Yes, information can leak in undesired ways if they were not careful abut the changes they made.
Suppose Tom has only read permission in developer class. Now since Alice has change permission in developer class so she can change the class of Tom. If Alice changes the class of Tom to employees then Tom will accidentally gain change permission over employees class and this would lead to information leakage.
C) Members of the SSO class should not be allowed to apply the change rights to members of that class.
Since Alice is a member of the SSO class she can intentionally modify the class of herself to Outsiders and give her write permission over there. But she is actually having read permission on outsiders class. Thus information leakage can occur leading to data damage.
Developers Employess Outsiders Alice read, write read, write read Bob read read, write read, writeRelated Questions
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