Phishing for Passkeys - An Analysis of WebAuthn and CTAP
WebAuthn was supposed to replace passwords on the web: uniform, secure, manageable authentication for everyone! One of its unique selling points was supposed to be the impossibility of phishing attacks. When Passkeys were introduced, some of WebAuthn's security principles were watered down in order to achieve some usability improvements and thus reach more widespread adoption.
This presentation discusses the security of Passkeys against phishing attacks. It explains the possibilities for an attacker to gain access to accounts secured with Passkeys using spear phishing, and what conditions must be met for this to happen. It also practically demonstrates such an attack and discusses countermeasures.
Using this attack as motivation, participants will also learn about how Passkeys work under the hood. They will be introduced to the relevant standards and dive into some aspects in more detail. Ultimately, they will be able to determine whether Passkeys are a good fit for their use case.
Passkeys are rapidly becoming the standard for authentication, primarily due to their effectiveness against automated phishing. However, in order to increase usability, the standards have introduced new transport mechanisms. This presentation provides an analysis of Passkey resilience, specifically regarding one such new transport mechanism
Throughout this analysis, we will uncover:
- Passkey Details: What standards are behind Passkeys and how the authentication process actually works
- The Hybrid Transport Flow: An investigation into how "Scan a QR code to sign in" functions
- An Attack: After having understood how hybrid transport works, we can exploit a crucial detail in order to spear-phish a Passkey user
- Risk Assessment: How to interpret these findings to determine if Passkeys are an appropriate fit for specific high-security use cases
This session is designed for developers and security engineers who want to understand the underlying mechanics of WebAuthn and CTAP. By the end of this talk, you will have a deeper understanding of how these standards govern modern authentication and how to critically assess their suitability for your application.
As a fullstack software developer, Michael's main expertise lies in simple software development. But since he is well aware that the happy path is the easy part, he's always had an interest for security and he's always been very security- and privacy-aware in his work. He enjoys developing user experiences that aren't just unobstructed by security, but that are improved because of it.