Security in Computing 5th Edition by Shari Lawrence Pfleeger, Charles P Pfleeger, Jonathan Margulies

Exercise 16

Describe a mechanism by which an operating system can enforce limited transfer of capabilities. That is, process A might transfer a capability to process B, but A wants to prevent B from transferring the capability to any other processes.

Your design should include a description of the activities to be performed by A and B, as well as the activities performed by and the information maintained by the operating system.

Step 1 of 2

Transfer of capabilities

Capability uses the ticket mechanism to control the accesses, like the normal ticket it should also not be duplicable. In capability, a ticket is raised for the subject to have certain access to the object. In place of the ticket, the capability term is directly used. For the ticket not to be forged, instead of passing the ticket the pointer to the data structure is passed while the tickets are stored in the operating system or the capabilities are encrypted. Capabilities are backed up more of access control tables to store the access control relations of different objects and subjects. To improve the speed of accessing, the capabilities of the recent objects are kept according to the availability.

The process that requires the capability sends a request to the operating system. The operating system checks for the process access to the resources and grant the capability to it. Now, it is up to the capability holder to pass the capability to other process. This can be done with the help of transfer command. The capability can be stopped from further transmission by deleting the transfer access from the user to whom capability was passed.