Hi I am studying for my operating system programming exam and we been provided with a sample exam but no answers have been given. I have answered a) and b) but I am not sure how to answer c). It will be much appreciated if you explain how you managed to get the answer. Thanks.
Question:
The model of protection in a computer system can be viewed as an access control matrix, with rows representing objects (for
example files), and columns representing domains (for example users). Each entry in the matrix represents the access rights
of the domain to the object. Consider the access control matrix below:
Anna Bill Charles Damian Afile rx r r Bfile x rx x Cfile rx rw rx Dfile r r r rw
a) If the system implements access control lists, what access rights are associated with file Bfile in the table above?
Answer:
Anna Bfile(x)
Bill Bfile(rx)
Charles Bfile(x)
b)If the system implements capabilities, what capabilities are granted to user Anna?
Answer:
Anna Afile(rx), Bfile(x), Dfile(r)
c)Assume that each user (domain) is the owner of the file (object) with the name starting with their initial, i.e. Anna owns
Afile, Bill owns Bfile etc. Represent the access control matrix in the table above using protection scheme available in UNIX.
You will need to define groups of users.