fix(ctap1): emit Le on U2F APDUs to support case 4#200
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fix(ctap1): emit Le on U2F APDUs to support case 4#200AlfioEmanueleFresta wants to merge 2 commits into
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U2F REGISTER and AUTHENTICATE are Case 4 APDUs per FIDO U2F Raw Message Formats v1.2 sections 3 and 4. The encoder previously stopped after the Lc + data field, silently dropping the response_max_length that callers were setting. Strict authenticators reject these as Case 3 (no response expected) requests. Append a 2-byte big-endian Le when response_max_length is Some, with values >= 65536 encoded as the 0x0000 wildcard.
The From<&ApduRequest> for Command impl was calling Command::new_with_payload, which produced a Case 3 APDU and dropped the response_max_length field. U2F REGISTER and AUTHENTICATE require a Case 4 APDU per FIDO U2F NFC section 3.1. Switch to new_with_payload_le so Le is included when the request asks for a response. For the typical short-form request (le=256), apdu-core encodes Le as a single 0x00 byte.
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U2F REGISTER and AUTHENTICATE produce a response payload, so per FIDO U2F Raw Message Formats v1.2 section 3.1 the request APDU must include
Le(omittingLeis reserved for instructions not expected to yield response bytes). libwebauthn was settingresponse_max_lengthon theApduRequestbut both encoders silently dropped it:ApduRequest::raw_longstopped after theLc + datafield. Withresponse_max_length = Some(0x100)the byte stream came out as a Case 3 extended APDU (noLe).From<&ApduRequest> for CommandusedCommand::new_with_payload, which does not carryLeat all.Strict authenticators reject Case 3 register/authenticate. The in-tree virtual
fido-authenticatoris lenient about it, so CI never caught the gap.Changes
ApduRequest::raw_longnow appends a 2-byte big-endianLewhenresponse_max_lengthisSome(_), matching the extended-length encodingLe1 Le2from FIDO U2F Raw Message Formats v1.2 section 3.1.3. Values>= 65536collapse to0x0000(the spec's wildcard forNe = 65536). This is the path used by HID, BLE, and caBLE, all of which mandate extended-length encoding (FIDO U2F HID v1.2 section 2.4; FIDO U2F BT v1.2 sections 5.1 and 5.2).From<&ApduRequest> for Commandswitches toCommand::new_with_payload_le, soresponse_max_lengthis propagated throughapdu-core. Withlonger_payloadsdisabled (the default in this crate),apdu-corewritesLeas a single byte; for the typical request withresponse_max_length = 256this yieldsLe = 0x00, which is short-form Case 4 and valid under FIDO U2F NFC v1.2 section 3 ("either short or extended length APDU encoding is allowed").raw_longand the NFC encoder, including the wildcardLe = 0x0000.Spec references