feat(webauthn): parse hints & merge into a transport preference#300
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WebAuthn Level 3 lets a relying party say how it expects the user to authenticate, through the hints array, the authenticator attachment, and per-credential transports. All three were parsed at the IDL layer and then dropped on the way to the internal request, so the preference never reached the caller. Parse them into typed enums and merge them into one ordered, de-duplicated list of transports, exposed through a new TransportHintedRequest trait on both request types, so that a consumer can prioritise its device chooser. Hints outrank the attachment, which outranks per-credential transports. A hybrid hint on its own also demotes the platform authenticator. The result is advisory ordering, never an eligibility filter. Unrecognised values parse as Unknown rather than failing, and are ignored when merging. Both new enums are non_exhaustive, since the WebAuthn enumerations are extensible and a future variant should not be a breaking change. Refs: linux-credentials/credentialsd#183
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A relying party can say how it expects the user to authenticate, through the hints array, the authenticator attachment, and per-credential transports. All three were parsed and then dropped on the way to the internal request, so the preference never reached the caller.
They are now parsed into typed enums and merged into one ordered list of transports. Hints outrank the attachment, which outranks per-credential transports, and a hybrid hint on its own demotes the platform authenticator. The result is advisory ordering, never a filter.
The consumer is credentialsd, which uses it to prioritise its device chooser, so there is deliberately no caller in this repo. This is the design agreed in credentialsd#183.
It is source breaking and wants a 0.10.0 bump: credentialsd builds these request types and will need updating in step.
Refs: linux-credentials/credentialsd#183