Re: [webauthn] Support a "create or get [or replace]" credential re-association operation (#1568)

If `excludeCredentials` (or something similar) would accept [user ID](https://www.w3.org/TR/webauthn/#dom-publickeycredentialuserentity-id) as the value, then I could use a constant user ID for all our users and prevent creation of a new key if one exists for that user. Using constant ID is against [the standard though](https://www.w3.org/TR/webauthn/#dom-publickeycredentialuserentity-id):

> Note: the [user handle](https://www.w3.org/TR/webauthn/#user-handle) ought not be a constant value across different accounts, even for [non-discoverable credentials](https://www.w3.org/TR/webauthn/#non-discoverable-credential), because some authenticators always create [discoverable credentials](https://www.w3.org/TR/webauthn/#discoverable-credential). Thus a constant [user handle](https://www.w3.org/TR/webauthn/#user-handle) would prevent a user from using such an authenticator with more than one account at the [Relying Party](https://www.w3.org/TR/webauthn/#relying-party).

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Received on Wednesday, 9 July 2025 20:38:47 UTC