Access Control

EAL

• Note: product with high EAL may not be more secure than one with lower EAL
• Why?
• Similarly, product with an EAL may not be any more secure than one without
• Why?

EAL 1 thru 7

• EAL1  functionally tested
• EAL2  structurally tested
• EAL3  methodically tested, checked
• EAL4  designed, tested, reviewed
• EAL5  semiformally designed, tested
• EAL6  verified, designed, tested
• EAL7  formally … (blah blah blah)

Common Criteria

• EAL4 is most commonly sought
• Minimum needed to sell to government
• EAL7 requires formal proofs
• Author could only find 2 EAL7 products…
• Who performs evaluations?
• Government accredited labs, of course (for a hefty fee, like 6 figures)

Authentication vs Authorization

• Authentication  Are you who you say you are?
• Restrictions on who (or what) can access system
• Authorization  Are you allowed to do that?
• Restrictions on actions of authenticated users
• Authorization is a form of access control
• Classic view of authorization…
• Access Control Lists (ACLs)
• Capabilities (C-lists)

Lampson’s Access Control Matrix

rx	rx	r		
rx	rx	r	rw	rw
rwx	rwx	r	rw	rw
rx	rx	rw	rw	rw

OS
Accounting
program
Accounting
data
Insurance
data
Payroll
data
Bob
Alice
Sam
Accounting
program

• Subjects (users) index the rows
• Objects (resources) index the columns

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