Programming with Privileges

	For this assignment, modify the programs for the last
	assignment to use the actual user and group ID.  That is,
	instead of having -u and -g, see what permissions the
	programs are actually running with.

	The catch: you MUST prevent any access to the repository
	that bypasses the ACLs.  This implies that the repository
	must be protected using OS permissions, which in turn means
	that a separate UID is needed.  The programs must either
	be setUID or use message-passing; that's your choice.

	The objects for user and group names are no longer needed;
	use the system's equivalents.

	You may not use the OS ACL mechanisms; you must implement
	them yourself.

	One important design decision: what UID are you using, root
	or some non-privileged one?  Your README file MUST justify
	your choice.  A correct choice with an incorrect justification
	will lose points.  (Of course, an incorrect choice will
	also lose points.)

	You should run this assignment using a VMware virtual
	machine; see the instructions on the web page.

	If you choose to use message-passing, you need not solve
	the start-up problem; it is acceptable to start the daemon
	manually.

	You must supply a script that will create an empty repository,
	including setting all permissions you rely on for correct,
	secure behavior.  The README file should explain the rationale
	for whatever permissions you choose.

	You may (probably will...) find the getuid() and getpwuid()
	routines (and the corresponding routines for groups) to be
	helpful.

	Also: because a lot of the testing needs to involve stuff running
	as different users, the test script must be run as root.  To run
	something as another user, write

	      su username -c "./objget..."

	      where "username" is whatever username that command should
	      run as.