Unverified Ownership

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

This function is part of a privileged program that takes input from users with potentially lower privileges.

def killProcess(processID):
  os.kill(processID, signal.SIGKILL)

This code does not confirm that the process to be killed is owned by the requesting user, thus allowing an attacker to kill arbitrary processes.

This function remedies the problem by checking the owner of the process before killing it:

def killProcess(processID):

  user = getCurrentUser()

  #Check process owner against requesting user
  if getProcessOwner(processID) == user:
    os.kill(processID, signal.SIGKILL)
    return

  else:
    print("You cannot kill a process you don't own")
    return

See Also