Enforcing SSoD policies by SMER Constraints Hong Chen Motivation Terminology SoD Separation of Duty RBAC Role Based Access Control SMER Static Mutually Exclusive Role SoD is important in RBAC systems Directly enforcing SoD in RBAC is difficult We can use SMER to enforce RBAC Definitions 1 Domains U the set of all possible users R the set of all possible roles P the set of all possible permissions RBAC state Definitions 2 SSoD policy SSoD safety SMER constraint RBAC state satisfies SMER constraint Enforcing SSoD by SMER Example Example borrowed from Ninghui Li Ziad Bizri and Mahesh V Tripunitara On Mutually Exclusive Roles and Separation of Duty ccs 2004 Current Research Result Directly enforcing SSoD policies in RBAC is intractable Enforcing SMER constraints is efficient Verification problem is intractable Generation of singleton SMER constraints Precise enforcement is not always possible Enforcing is not enough Compatibility Example C1 and C2 both enforce E C1 is not a good choice Comparing SMER constraints Compare two SMER constraints C1 is at least as restrictive as C2 under RH denoted by if and only if If both C1 and C2 are in a set of SMERs and C1 is more restrictive than C2 than we can simply remove C2 from the set Generation of SMER constraints 1 Na ve Generation 2 2 n Even for small n not efficient Generating all set of SMERs that can minimally implement given SSoD policies Starting from most restrictive SMERs Generation of SMER constraints 2 Most Restrictive set of SMERs Restrictive SMERs that implement SSoD SMERs that minimally implement SSoD SMERs that do not implement SSoD Not Restrictive Summary Notion of implementation Comparison between different SMERs Comparison between different SSoDs Algorithm to generate all set of SMERs that minimally implement SSoD Future Work When can we precisely implement SSoD More efficient generation algorithm How to choose from a set of implementations How to compare different SMER constraints according to the given SSoD policies
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