On Missing Attributes in Access Control: Non-deterministic and Probabilistic Attribute Retrieval
On Missing Attributes in Access Control: Non-deterministic and Probabilistic Attribute Retrieval
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关于访问控制中的缺失属性：非确定性和概率性属性检索
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
Nicola Zannone
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作者：
J. Crampton;C. Morisset;Nicola Zannone
基于属性的访问控制（ABAC）正在成为规范和评估访问控制策略的参考模型。在ABAC中，策略和访问请求是根据属性名/值对来定义的。ABAC策略对请求的适用性通过将请求中的属性与策略中的属性进行匹配来确定。一些支持ABAC的语言（如PTaCL或XACML 3.0）考虑到在评估请求时可能无法正确检索某些属性值的可能性，并使用复杂的决策（通常描述所有可能的评估结果）来解释缺失的属性。在本文中，我们认为ABAC中缺失属性的问题可以被看作是一个非确定性的属性检索过程，并且我们证明了PTaCL或XACML中当前的评估机制可以返回一个不一定与实际可能结果匹配的复杂决策。然而，这对执行机制来说是有问题的，因为执行机制需要将复杂的决定解决为决定性的决定。我们提出了一种新的评估机制，明确地基于给定请求的非确定性属性检索。我们将该机制扩展到概率属性检索，并在概率模型检查器PRISM中实现了PTaCL的概率策略评估机制。
Attribute Based Access Control (ABAC) is becoming the reference model for the specification and evaluation of access control policies. In ABAC policies and access requests are defined in terms of pairs attribute names/values. The applicability of an ABAC policy to a request is determined by matching the attributes in the request with the attributes in the policy. Some languages supporting ABAC, such as PTaCL or XACML 3.0, take into account the possibility that some attributes values might not be correctly retrieved when the request is evaluated, and use complex decisions, usually describing all possible evaluation outcomes, to account for missing attributes. In this paper, we argue that the problem of missing attributes in ABAC can be seen as a non-deterministic attribute retrieval process, and we show that the current evaluation mechanism in PTaCL or XACML can return a complex decision that does not necessarily match with the actual possible outcomes. This, however, is problematic for the enforcing mechanism, which needs to resolve the complex decision into a conclusive one. We propose a new evaluation mechanism, explicitly based on non-deterministic attribute retrieval for a given request. We extend this mechanism to probabilistic attribute retrieval and implement a probabilistic policy evaluation mechanism for PTaCL in PRISM, a probabilistic model-checker.