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> What happens if the attacker spoofs DNS? They would also have to get a publicly-trusted TLS certificate for that domain. U2F is HTTPS-only, at least on Chrom
by pfg 9y ago
> What happens if the attacker spoofs DNS?
They would also have to get a publicly-trusted TLS certificate for that domain. U2F is HTTPS-only, at least on Chrome. If the attacker can do that, you have bigger problems.
> Also, the scheme you describe requires the user to trust the web browser. But, if the web browser is, say, on a public computer, it can't necessarily be trusted.
No one has really solved secure authentication on a compromised system. I dare say it's not a problem that can be solved.
- StavrosK 9y agoCan you reuse tokens, or use previous ones? It seems that, even if the browser were compromised, the key should still be safe, as the user has to use one response to log in. If the response can't be reused, and the challenge can't be reused to generate a new response, the user should be safe, no? Basically, if the site sends a random nonce to sign, I don't see how you can reuse things. The most you can do is have the browser sneakily and remotely authenticate you on your computer (if you're the attacker), but the user still needs to press the button.
- pfg 9y agoI think you're making this too complicated, unless I'm missing something. If your system is compromised, the attacker can steal your session key (from your cookies or whatever else the site uses). That's just about as good as your U2F key, with some defense-in-depth exceptions that I mentioned here[1]. [1]: https://news.ycombinator.com/item?id=15044826 https://news.ycombinator.com/item?id=15044826