Automatic Verification of Firewall Configuration with Respect to Security Policy Requirements

Firewalls are key security components in computer networks. They filter network traffics based on an ordered list of filtering rules. Firewall configurations must be correct and complete with respect to security policies. Security policy is a set of predicates, which is a high level description of traffic controls. In this paper, we propose an automatic method to verify the correctness of firewall configuration. We have defined a boolean formula representation of security policy. With the boolean formula representations of security policy and firewall configuration, we can formulate the condition that ensures correctness of firewall configuration. We use SAT solver to check the validity of the condition. If the configuration is not correct, our method produces an example of packet to help users to correct the configuration. We have implemented a prototype verifier and had some experimental results. The first results were very promising.