Behavioral Fuzzing Operators for UML Sequence Diagrams

Model-based testing is a recognized method for testing the functionality of a system under test. However, it is not only the functionality of a system that has to be assessed. Also the security aspect has to be tested, especially for systems that provide interfaces to the Internet. In order to find vulnerabilities that could be exploited to break into or to crash a system, fuzzing is an established technique in industry. Model-based fuzzing complements model-based testing of functionality in order to find vulnerabilities by injecting invalid input data into the system. While it focuses on invalid input data, we present a complementary approach called behavioral fuzzing. Behavioral fuzzing does not inject invalid input data but sends an invalid sequence of messages to the system under test. We start with existing UML sequence diagrams --- e.g. functional test cases --- and modify them by applying fuzzing operators in order to generate invalid sequences of messages. We present the identified fuzzing operators and propose a classification for them. A description of a case study from the ITEA-2 research project DIAMONDS as well as preliminary results are presented.