DSTC: DNS-Based Strict TLS Configurations

  • Eman Salem AlashwaliEmail author
  • Pawel Szalachowski
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11391)


Most TLS clients such as modern web browsers enforce coarse-grained TLS security configurations. They support legacy versions of the protocol that have known design weaknesses, and weak ciphersuites that provide fewer security guarantees (e.g. non Forward-Secrecy), mainly to provide backward compatibility. This opens doors to downgrade attacks, as is the case of the POODLE attack [18], which exploits the client’s silent fallback to downgrade the protocol version to exploit the legacy version’s flaws. To achieve a better balance between security and backward compatibility, we propose a DNS-based mechanism that enables TLS servers to advertise their support for the latest version of the protocol and strong ciphersuites (that provide Forward-Secrecy and Authenticated-Encryption simultaneously). This enables clients to consider prior knowledge about the servers’ TLS configurations to enforce a fine-grained TLS configurations policy. That is, the client enforces strict TLS configurations for connections going to the advertising servers, while enforcing default configurations for the rest of the connections. We implement and evaluate the proposed mechanism and show that it is feasible, and incurs minimal overhead. Furthermore, we conduct a TLS scan for the top 10,000 most visited websites globally, and show that most of the websites can benefit from our mechanism.



We thank Prof. Andrew Martin for feedback and Monica Kaminska for proofreading. Pawel’s work was supported by the SUTD SRG ISTD 2017 128 grant.


  1. 1.
    Adrian, D., et al.: Imperfect forward secrecy: how Diffie-Hellman fails in practice. In: Computer and Communications Security (CCS), pp. 5–17 (2015)Google Scholar
  2. 2.
    Alashwali, E., Rasmussen, K.: On the feasibility of fine-grained TLS security configurations in web browsers based on the requested domain name. In: Security and Privacy in Communication Networks (SecureComm) (2018)Google Scholar
  3. 3.
    Alashwali, E., Rasmussen, K.: What’s in a downgrade? A taxonomy of downgrade attacks in the TLS protocol and application protocols using TLS. In: Applications and Techniques in Cyber Security (ATCS) (2018)Google Scholar
  4. 4.
    Amann, J., Gasser, O., Scheitle, Q., Brent, L., Carle, G., Holz, R.: Mission accomplished? HTTPS security after diginotar. In: Internet Measurement Conference (IMC), pp. 325–340 (2017)Google Scholar
  5. 5.
    AmazonWS: Alexa Top 1M Global Sites (2018). Accessed 5 May 2018
  6. 6.
    Apache: Apache HTTP Server Project (2018). Accessed 6 July 2018
  7. 7.
    Arends, R., Austein, R., Larson, M., Massey, D., Rose, S.: DNS Security Introduction and Requirements (2005). Accessed 6 July2018
  8. 8.
    Aviram, N., et al.: DROWN: breaking TLS using SSLv2. In: USENIX Security Symposium, pp. 689–706 (2016)Google Scholar
  9. 9.
    Beurdouche, B., et al.: A messy state of the union: taming the composite state machines of TLS. In: Security and Privacy (SP), pp. 535–552 (2015)Google Scholar
  10. 10.
    Beurdouche, B., Delignat-Lavaud, A., Kobeissi, N., Pironti, A., Bhargavan, K.: FLEXTLS a tool for testing TLS implementations. In: USENIX Workshop on Offensive Technologies (WOOT) (2014)Google Scholar
  11. 11.
    Bhargavan, K., Brzuska, C., Fournet, C., Green, M., Kohlweiss, M., Zanella-Béguelin, S.: Downgrade resilience in key-exchange protocols. In: Security and Privacy (SP), pp. 506–525 (2016)Google Scholar
  12. 12.
    Bhargavan, K., Leurent, G.: Transcript collision attacks: breaking authentication in TLS, IKE, and SSH. In: Network and Distributed System Security Symposium (NDSS) (2016)Google Scholar
  13. 13.
    Dukhovni, V., Hardaker, W.: The DNS-Based Authentication of Named Entities (DANE) Protocol: Updates and Operational Guidance (2015). Accessed 6 July 2018
  14. 14.
    Hallam-Baker, P.: DNS Certification Authority Authorization (CAA) Resource Record (2013). Accessed 6 July 2018
  15. 15.
    Internet Systems Consortium: Bind Open Source DNS Server (2018). Accessed 6 July 2018
  16. 16.
    Menezes, A.J., Van Oorschot, P.C., Vanstone, S.A.: Handbook of Applied Cryptography. CRC Press, Boca Raton (1996)CrossRefGoogle Scholar
  17. 17.
    Mockapetris, P.: Domain Names - Implementation and Specification (1987). Accessed 6 July 2018
  18. 18.
    Möller, B., Duong, T., Kotowicz, K.: This POODLE Bites: Exploiting the SSL 3.0 Fallback (2014). Accessed 6 July 2018
  19. 19.
    Oracle: Virtualbox (2018). Accessed 6 July 2018
  20. 20.
    Python: Python (2018). Accessed 6 July 2018
  21. 21.
    Python: ssl - TLS/SSL Wrapper for Socket Objects (2018). Accessed 6 July 2018
  22. 22.
    Python: time-Time Access and Conversions (2018). Accessed 6 July 2018
  23. 23.
    rbsec: sslscan Tests SSL/TLS Enabled Services to Discover Supported Cipher Suites (2018). Accessed 6 July 2018
  24. 24.
    Rescorla, E.: The Transport Layer Security (TLS) Protocol Version 1.2 (2008). Accessed 6 July 2018
  25. 25.
    Rescorla, E.: The Transport Layer Security (TLS) Protocol Version 1.3 draft-ietf-tls-tls13-28 (2018). Accessed 6 July 2018
  26. 26.
    Schechter, S.: Storing HTTP Security Requirements in the Domain Name System (2007). Accessed 6 July 2018
  27. 27.
    Sullivan, N.: Padding Oracles and the Decline of CBC-mode Cipher Suites (2016). Accessed 6 July 2018
  28. 28.
    Varshney, G., Szalachowski, P.: A Metapolicy Framework for Enhancing Domain Expressiveness on the Internet. In: Security and Privacy in Communication Networks (SecureComm) (2018)Google Scholar
  29. 29.
    Vaudenay, S.: Security Flaws Induced by CBC Padding-Applications to SSL, IPSEC, WTLS.... In: Theory and Applications of Cryptographic Techniques (2002)Google Scholar
  30. 30.
    Wagner, D., Schneier, B.: Analysis of the SSL 3.0 Protocol. In: USENIX Workshop on Electronic Commerce (EC), pp. 29–40 (1996)Google Scholar

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.University of OxfordOxfordUK
  2. 2.King Abdulaziz University (KAU)JeddahSaudi Arabia
  3. 3.Singapore University of Technology and Design (SUTD)SingaporeSingapore

Personalised recommendations