Fuzzing for Detecting Access Policy Violations in REST APIs

Due to their widespread use in industry, several techniques have been proposed in the literature to fuzz REST APIs. Existing fuzzers for REST APIs have been focusing on detecting crashes (e.g., 500 HTTP server error status code). However, security vulnerabilities can have major drastic consequences on existing cloud infrastructures.In this paper, we propose a series of novel automated oracles aimed at detecting violations of access policies in REST APIs. These novel automated oracles can be integrated into existing fuzzers, in which, once the fuzzing session is completed, a 'security testing' phase is executed to verify these oracles.Our novel techniques are integrated as an extension of EVO-MASTER, a state-of-the-art fuzzer for REST APIs. Experiments are carried out on a series of artificial examples and 13 real-world REST APIs. Results show that our novel oracles and their automated integration in a fuzzing process can lead to detect security issues in some of these APIs.