Systematic Fuzzing and Testing of TLS Libraries

We present TLS-Attacker, an open source framework for evaluating the security of TLS libraries. TLS-Attacker allows security engineers to create custom TLS message flows and arbitrarily modify message contents using a simple interface in order to test the behavior of their libraries. Based on TLS-Attacker, we present a two-stage fuzzing approach to evaluate TLS server behavior. Our approach automatically searches for cryptographic failures and boundary violation vulnerabilities. It allowed us to find unusual padding oracle vulnerabilities and overflows/overreads in widely used TLS libraries, including OpenSSL, Botan, and MatrixSSL.