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by dns_snek 144 days ago
WebUSB is a giant gaping hole in the browser sandbox. Innocent use cases are really nice, I've used WebUSB to flash GrapheneOS on my device, but the possibilities for users to shoot themselves in the foot with nefarious website are almost endless.

Consider the fact that Chromium has to specifically blacklist Yubikey and other known WebAuthn vendor IDs, otherwise any website could talk to your Yubikey pretending to be a browser and bypass your 2FA on third party domains.

I'm conflicted on WebUSB because it's convenient but on the balance I think it's too dangerous to expose to the general public. I don't know how it could be made safer without sacrificing its utility and convenience.
1 comments
jorvi 143 days ago
It really isn't. Chromium (since 67) does USB interface class filtering to prevent access to sensitive devices. Then there is the blacklist you mentioned.

On top of that, straight from Yubico's site:

".. The user must approve access on a per website, per device basis .."

This isn't any more a security hole than people clicking "yes" on UAC prompts that try to install malware.

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dns_snek 143 days ago
> ".. The user must approve access on a per website, per device basis .."

Of course, but a phishing website "fake-bank.com" could collect user's username, password, and then prompt them to touch their yubikey. This wouldn't trigger any alarm bells because it's part of the expected flow.

> This isn't any more a security hole than people clicking "yes" on UAC prompts that try to install malware.

Yes it is. The only reason why Yubikeys are immune to phishing and TOTP codes aren't is because a trusted component (the browser) accurately informs the security key about the website origin. When a phishing website at "fake-bank.com" is allowed to directly communicate with the security key there's nothing stopping it from requesting credentials for "bank.com"

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jorvi 142 days ago
Again, that exploit factor is irrelevant now because WebUSB is blacklisted from accessing, among other things, HID class devices. So no site, even with permission, can access U2F devices over WebUSB. There is no special blacklist needed per vendor or anything.

You are right that it was a security hole in Chrome <67. Which is almost a decade in the past by now.

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