Presented at
DEF CON 31 (2023),
Aug. 11, 2023, 4:30 p.m.
(45 minutes)
TLS is the de facto way of securing network connections. It provides an easy way of ensuring confidentiality, integrity and authentication for any type of communication. However, like most things in life, this is also too good to be true.
TLS allows communicating parties to uniquely authenticate each other by validating each other's certificate. However, many TLS libraries and frameworks have insecure default settings or allow for the developers to skip important aspects of certificate validation in their client implementations.
This talk explores issues in TLS client certificate validation and the underlying reasons why developers still fail to implement TLS correctly. Most importantly, we hack all the things with a new TLS mitm tool: certmitm.
certmitm automatically discovers and exploits insecure certificate validation vulnerabilities in TLS clients. Let's use the tool to hack iOS, Windows 11 and more while we deep dive into the world of insecure TLS certificate validation.
REFERENCES:
My previous TLS talks:
HelSec 20 - Practical attacks against modern TLS implementations - Aapo Oksman: https://www.youtube.com/watch?v=NCm16vLfD60
Disobey 2023 - Your connection is not private Exploiting insecure certificate validation in TLS clients - Aapo Oksman: https://www.youtube.com/watch?v=vZvL6ZRiKls
Moxie Marlinspikes work in SSL/TLS:
DEF CON 17 - Moxie Marlinspike - More Tricks for Defeating SSL: https://www.youtube.com/watch?v=5dhSN9aEljg
DEF CON 19 - Moxie Marlinspike - SSL And The Future Of Authenticity: https://www.youtube.com/watch?v=UawS3_iuHoA
Scientific publications:
Georgiev, Martin, et al. "The most dangerous code in the world: validating SSL certificates in non-browser software." Proceedings of the 2012 ACM conference on Computer and communications security. 2012.
Akhawe, Devdatta, et al. "Here's my cert, so trust me, maybe? Understanding TLS errors on the web." Proceedings of the 22nd international conference on World Wide Web. 2013.
Huang, Lin Shung, et al. "Analyzing forged SSL certificates in the wild." 2014 IEEE Symposium on Security and Privacy. IEEE, 2014.
Sivakorn, Suphannee, et al. "HVLearn: Automated black-box analysis of hostname verification in SSL/TLS implementations." 2017 IEEE Symposium on Security and Privacy (SP). IEEE, 2017.
Alghamdi, Khalid, et al. "Iotverif: An automated tool to verify ssl/tls certificate validation in android mqtt client applications." Proceedings of the Eighth ACM Conference on data and application security and privacy. 2018.
Presenters:
-
Aapo Oksman
- Senior Security Specialist at Nixu Corporation
Aapo Oksman is a Senior Security Specialist at Nixu Corporation working with application, network and device security. His background is in electrical engineering, embedded devices, and test automation. Combining his background with a hobby in hacking lead to a career in cybersecurity focusing on industrial IoT.
In his free time, Bug Bounties and security research keep Aapo motivated and learning. His work in PKI and TLS has resulting in multiple CVEs from vendors such as Microsoft and Apple. Outside work and research Aapos passion is in the community. He takes part in organizing local security meetups and coaches the Finnish national youth CTF team to the yearly European Cybersecurity Challenge competition.
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