Re: [webauthn] §6.1.1. Signature Counter Considerations does not explicitly mention constant-zero case (#1734)

> Should we also consider offering advice to RP's on what to do if an authenticator _stops_ providing a non-zero counter in subsequent authentications? Touch ID registered via Chrome on macOS used to return responses with (atomic?) timestamps for a counter, but now those kinds of responses return `0`. I think Chrome only returns zeroes now so perhaps it's less of an issue, but that's not to say this scenario can't play out again with future authenticators.

Webauthn-RS rejects any credential where it was registered with a counter of 0, and then attempts to authenticate with a counter of > 0, since this changes the dynamic of the trust relationship we had between registration to authentication. We can't rule out some kind of tampering or forgery, so it's rejected. I think we should definitely have advice related to this scenario. 

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Received on Sunday, 29 May 2022 23:55:51 UTC