Access Control

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Access Control
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Access Control

• Access control principles
• Mandatory Access Control (MAC)
• Discretionary Access Control (DAC)
• Role-based Access Control
• Matrix model

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Access Control Principles

• Access control is not a stand alone component of
  a security system
• Access control coexists with other security
  services
• Access control works closely with audit control
• Access matrix is a good tool to specify
  permissions
• Access Control List (ACL) details are placed in
  Access Matrix

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Access Control Example
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Access Control Example
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Access Control

• Reference Access Control Principles and
  Practice by R. S. Sandhu and P.Samarati, IEEE
  Communications Magazine, Vol. 32, Sept. 1994, 40
  48.

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Mandatory Access Control

• Why MAC is needed?
• Enhances security of database
• Gives consistent view of operations
• General rule is all allowed accesses are provided
  by MAC
• Access that is not part of MAC is discretionary
• MAC adds to complexity

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Mandatory Access Control

• MAC is used for type enforcement (TE) as is done
  in programming languages
• MAC protects organizational data
• MAC deals with database queries, reports and
  statistical studies
• Data protection for a class is determined by its
  label
• Relabel privileges follow a set of rules since
  label makes a difference in access

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Mandatory Access Control

• Relabels are used for declassification of
  existing objects or for approvability
• Relabels do not allow changing or observing the
  content
• Information flow is specified between MAC labels
• Information flow restrictions are essential for
  maintaining confidentiality

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Mandatory Access Control

• Examples
• Official reports (DAC permission allows DAC copy)
• Statistical analysis of medical records
  (providers and researchers have different view of
  same data)
• Accounting records (updated by structured
  programs and accessed by unstructured programs)

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Discretionary Access Control

• DACs provide flexibility in allowing access to
  database
• DACs protect unstructured work in progress
• DAC objects contain information protected by MAC
• DAC also includes privileges associated with
  email
• DAC labels are derived from MAC labels

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Discretionary Access Control

• Access decisions in DAC do not take into account
  the users role or programs functionality
• Linux has benefited from DAC

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Role-based Access Control

• Reference Role-based Access Control Models by
  R. S. Sandhu et al, IEEE Computer, Vol. 29, Feb.
  1996, 38-47.
• Databases are used by multiple users for multiple
  applications
• Role-based access control (RBAC) is one way to
  handle security for the users and applications

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Role-based Access Control

• Role of the user in the organization determines
  the access level for the database
• DBAs create roles and assign permissions to roles
• DBAs and others can place users in appropriate
  roles
• Roles can define specific individuals allowed
  access or extent of access to resources for
  multiple individuals

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Role-based Access Control

• SQL3 standard (NIST) recognizes the importance of
  RBAC
• Oracle 7 is the first commercial system to
  implement RBAC
• Roles can be mutually exclusive
• Role-role relations enforce security policies
• Permissions assigned to roles change less
  frequently than permissions assigned to
  individuals

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Role-based Access Control

• RBAC is policy-neutral
• RBAC supports the following security principles
• Least privilege (only the needed permissions are
  assigned to roles)
• Separation of duties (use of mutually exclusive
  roles e.g., accountant writes check and manger
  signs the check)
• Data Abstraction (instead of read/write/execute
  permissions such as credit/debit are established)

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Role-based Access Control

• RBAC is independent of MAC and DAC
• RBAC can support MAC and DAC separately

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RBAC Example
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RBAC Example
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RBAC Example

• RBAC0 denotes the minimum requirements for an
  RBAC system
• RBAC1 adds role hierarchies and includes RBAC0
• RBAC2 adds constraints and includes RBAC0
• RBAC3 includes RBAC1 and RBAC2 and transitively
  RBAC0

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RBAC Example
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Matrix Model

• Matrix model consists of
• Objects (data)
• Subjects (user processes like queries)
• Rights (permissions for read, etc)
• Rows of the matrix are objects and columns are
  subjects and the content of each cell is the
  rights
• Protection domain consists of a collection of
  access rights

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Matrix Model

• Matrix model consists of
• Access lists
• Capability lists
• Access list identifies people who have access to
  a particular object
• Capability list identifies each object and its
  operations