DiVerT

About

DiVerT (Disjunctive Verification with Types) is a prototype tool for verifying disjunctive security policies in database-backed application.

Install

• DiVerT requires Z3 and its Python bindings.

• To begin, you should Install Z3 on your platform, make sure it is in your PATH, and then proceed to install z3-solver bindings using the command pip install z3-solver.

• DiVerT was tested and is known to work with Z3 version 4.8.7.

• Clone the repo, or download it as a ZIP file.

Running the use cases

You can run the tests or the use cases using the following commnad:

python main.py -i examples/DataPublishing/get_data.txt -d -r -o usr

Available arguments

• To specify the input source program, one should use the -i argument. In this case it is examples/DataPublishing/get_data.txt, which is the secure example of the Data Publishing use case.
• Debug information, including the final Gamma environment, the observer's dependency set, program labels, and policy labels, can be displayed by specifying the -d argument.
• In instances where the program is insecure, specifying the -r argument will provide insights into the reasons for the program's rejection.
• The observer's identifier can be (optionally) defined using the -o argument. In this case (and by default) it is usr.

Example

For example, test number 10 is a simple insecure program with the following code:

@Table(emp, n:str, r:str, s:int)@
@Policy(SELECT n,s FROM emp WHERE s > 1000; | SELECT n,r FROM emp; )@

x = @Query(SELECT n FROM emp WHERE s > 0;)@;
out(x,usr);

We can run this program with:

python main.py -i examples/Tests/test10.imp -r -d

The output of DiVerT for this program would look like:

######################### DEBUG #########################
Gamma final : 
		pc ↦ { {'pc'} }
		usr ↦ { {'pc', 'usr', Query<<SELECT n FROM emp WHERE s > 0;>>} }
		x ↦ { {'pc', Query<<SELECT n FROM emp WHERE s > 0;>>} }

usr's Dependency:
		usr ↦ { {'pc', 'usr', Query<<SELECT n FROM emp WHERE s > 0;>>} }

Program Labels : 
		{ < {'emp'}, (s>0), {'n'} > }


Policy Labels : 
		{ < {'emp'}, true, {'n', 'r'} > }
		{ < {'emp'}, (s>1000), {'n', 's'} > }


######################### REASON(S) #########################
Because: 
	< {'emp'}, (s>0), {'n'} > ⋢ < {'emp'}, true, {'n', 'r'} >
		Reason dep((s>0)) ∪ {'n'} ⊄ {'n', 'r'}

	< {'emp'}, (s>0), {'n'} > ⋢ < {'emp'}, (s>1000), {'n', 's'} >
		Reason (s>0) ⊭ (s>1000)

######################### VERDICT #########################

>>> The program is insecure. ⨉

Which clearly states that the program is insecure because none of the disjuncts of the policy allow query SELECT n FROM emp WHERE s > 0.