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…and back `AuthenticationExtensionsClientInputsJSON.hmacGetSecret` was parsed and then dropped: GetAssertionRequestExtensions had no field for it, so a caller of GetAssertionRequest::prepare could only ask for hmac-secret through `prf`, which the platform upgrades to userVerification=required (webauthn#2337). The pre-PRF client extension asks for the raw salts under the request's own userVerification, as browsers served it. It now reaches the CTAP request as GetAssertionHmacOrPrfInput::HmacGetSecret (prf wins when both are present) and the decrypted output comes back as `clientExtensionResults.hmacGetSecret`, not `prf`.
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I apologize, my agent went rouge and opened a PR. |
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AuthenticationExtensionsClientInputsJSON.hmacGetSecretis parsed by the IDL model but then dropped:GetAssertionRequestExtensionshad no field for it, so a caller ofGetAssertionRequest::preparecould only reach hmac-secret throughprf, which the platform upgrades touserVerification=required(#183 / webauthn#2337). The pre-PRF client extension asks for the raw salts under the request's ownuserVerification, as browsers served it.This wires it through: the JSON input becomes
GetAssertionHmacOrPrfInput::HmacGetSecreton the CTAP request (prfwins when both are present), and the decrypted output is returned asclientExtensionResults.hmacGetSecretinstead ofprf. Salts must be 32 bytes, as before (HMACGetSecretInput). Most of the diff is the new field in existing struct literals.Tests:
test_request_from_json_hmac_get_secret_extension(JSON parse, wrong-length salt refused) andhmac_get_secret_input_is_sent_raw_and_answered_as_itself(conversion, prf precedence). Verified end to end against a CanoKey emulated by QEMU withuserVerification: "discouraged": no PIN asked, the same salt agrees across assertions, another salt differs.Motivation: a desktop service that derives a device identity from the security key and wants touch-only assertions (the spec's PRF policy requires UV, which the key's PIN would satisfy at every use).