fix(webauthn): allow PRF inputs of any length (fix #209)#211
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AlfioEmanueleFresta
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msirringhaus
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iinuwa
Split PRFValue into PrfInputValue (Vec<u8>) for variable-length salt inputs and PrfOutputValue ([u8; 32]) for the fixed-size hmac-secret output. Per W3C WebAuthn L3 §10.1.4, PRF salt inputs are BufferSources of any length; the existing SHA-256 prefix-hashing already produces a 32-byte salt for CTAP2 hmac-secret regardless of input length. Adds unit tests for variable-length and empty inputs, and a virtual- device test exercising 0-byte, 7-byte, and 100-byte salts.
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Closes #209.
Split
PRFValueintoPrfInputValue(Vec<u8>, variable-length salt inputs) andPrfOutputValue([u8; 32], fixed-length hmac-secret outputs).Spec: W3C WebAuthn L3 §10.1.4 — PRF salt inputs are
BufferSources of any length; the client hashes them viaSHA-256("WebAuthn PRF" || 0x00 || input)before CTAP2 hmac-secret. The hashing was already in place; only the input type was over-constrained.Tests
eval_by_credentialvariable-length, plus un-#[ignore]'dtest_request_from_json_prf_extension.test_webauthn_prf_variable_length_inputexercises 0/7/100-byte salts end-to-end and asserts PRF determinism.