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Unformatted text preview: 12/19/2010 Unit 4: Discretionary Access Control
Click Here To Start Audio Subject and Objects
Subject - Explicitly Control Process Object - Data Store Both have security attributes (clearance vs. label) Subjects can create objects or children (subjects) Implementing Access Controls
Revoking Privileges Is Always an Issue Capabilities - Token-based Access Control Lists - Object Based ACLs are the clear winner. 1 12/19/2010 Directory Access Control File Access Options Ownership
Objects are “owned” by users. Ownership can be transferred. Over-ride ownership Group Ownership 2 12/19/2010 Access Control Matrix
Bishop, Figure 2-1 Processes are Rows Subjects/Objects are Columns Rights (own, read, write, execute) are entries.. Very Flexible Model Extended to Database Access via “verbs”. Protection States
Mathematical Basis is Required for Modeling. States are convenient for computer models. Basic Theory
◦ Define a Secure State (Initial Condition) ◦ Restrict Transformations to Prevent moving to Insecure States Important Rights
Copy (Grant) Right -> “Grant” Rights to another user. Own -> Change Privileges for yourself. Attenuation of Privilege - “A subject may not give rights it does not possess to another.” Basis of Formal Models of Chapter 3
◦ Take/Grant, Schematic Protection Model 3 ...
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- Spring '11