@article{WalzSikora2017,
  author    = {Andreas Walz and Axel Sikora},
  title     = {Exploiting Dissent: Towards Fuzzing-based Differential Black Box Testing of TLS Implementations},
  series   = {IEEE Transactions on Dependable and Secure Computing},
  volume    = {17},
  number    = {2},
  organization    = {IEEE},
  issn      = {1545-5971 (Print)},
  doi       = {10.1109/TDSC.2017.2763947},
  pages     = {278 -- 291},
  year      = {2017},
  abstract  = {The Transport Layer Security (TLS) protocol is one of the most widely used security protocols on the internet. Yet do implementations of TLS keep on suffering from bugs and security vulnerabilities. In large part is this due to the protocol's complexity which makes implementing and testing TLS notoriously difficult. In this paper, we present our work on using differential testing as effective means to detect issues in black-box implementations of the TLS handshake protocol. We introduce a novel fuzzing algorithm for generating large and diverse corpuses of mostly-valid TLS handshake messages. Stimulating TLS servers when expecting a ClientHello message, we find messages generated with our algorithm to induce more response discrepancies and to achieve a higher code coverage than those generated with American Fuzzy Lop, TLS-Attacker, or NEZHA. In particular, we apply our approach to OpenssL, BoringSSL, WolfSSL, mbedTLS, and MatrixSSL, and find several real implementation bugs; among them a serious vulnerability in MatrixSSL 3.8.4. Besides do our findings point to imprecision in the TLS specification. We see our approach as present in this paper as the first step towards fully interactive differential testing of black-box TLS protocol implementations. Our software tools are publicly available as open source projects.},
  language  = {en}
}