fix(ctap2): preserve raw authenticatorData bytes#249
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The authenticator signs over the exact authData bytes, including the extensions block. Rebuilding authData from the parsed struct could drop unmodeled extensions or reorder keys, breaking the relying party's signature verification. Keep the device bytes and return them unchanged. Platform-synthesized U2F authData still rebuilds from the fields.
AlfioEmanueleFresta
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This was referenced Jun 7, 2026
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The client rebuilt the authenticator data from a parsed structure instead of keeping the exact bytes the authenticator produced. An authenticator signature covers those exact bytes, so re-encoding could drop extension entries the client did not model or reorder map keys, which would make a relying party reject an otherwise-valid signature. This was confirmed against a real device response carrying an extension the client did not model.
This keeps the authenticator data verbatim and returns it unchanged. Platform-synthesized data is still built from fields.
Includes a regression test confirming the bytes round-trip unchanged, including an unmodeled extension.