Extensible access control for a hierarchy of servers

  • Authors:
  • Jean Bacon;Richard Hayton;Sai Lai Lo;Ken Moody

  • Affiliations:
  • University of Cambridge, Computer Laboratory, New Museums Site, Pembroke Street, Cambridge CB2 3QG England;University of Cambridge, Computer Laboratory, New Museums Site, Pembroke Street, Cambridge CB2 3QG England;University of Cambridge, Computer Laboratory, New Museums Site, Pembroke Street, Cambridge CB2 3QG England;University of Cambridge, Computer Laboratory, New Museums Site, Pembroke Street, Cambridge CB2 3QG England

  • Venue:
  • ACM SIGOPS Operating Systems Review
  • Year:
  • 1994

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Abstract

We discuss the protection requirements of a distributed storage service comprising a two-level hierarchy of storage servers with value-adding service layers above them. A flexible and extensible access control mechanism is required. Our scheme uses Access Control Lists (ACLs) to allow fine grained expression of policy together with capabilities for efficient runtime access after a once-off ACL check. Our capabilities are principal- specific and transient and their design ensures that access to objects is via the correct service hierarchy; for example, a directory object may only be manipulated via a directory service. The implementation of this protection is stateless at the servers above the storage service. The scheme also provides a convenient means to delegate rights for an object, temporarily, to an unprivileged server, for example a print-server. The fact that our capabilities are short-lived alleviates the requirement for selective revocation and crash recovery.