function parseAuthenticatorData()

in fido.js [319:375]
46 lines of code
5 McCabe index (conditional complexity)

function parseAuthenticatorData(authData) {
    try {
        const rpIdHash = authData.slice(0, 32);
        const flags = authData[32];
        const signCount = (authData[33] << 24) | (authData[34] << 16) | (authData[35] << 8) | (authData[36]);

        /** @type {AuthenticatorData} */
        const authenticatorData = {
            rpIdHash,
            flags,
            signCount,
            attestedCredentialData: undefined,
            extensionDataHex: undefined
        };

        if (flags & 64) {
            //has attestation data
            const aaguid = uuid.unparse(authData.slice(37, 53)).toUpperCase();
            const credentialIdLength = (authData[53] << 8) | authData[54];
            const credentialId = authData.slice(55, 55 + credentialIdLength);
            const publicKeyBuffer = authData.slice(55 + credentialIdLength, authData.length);
            const publicKeyHex = coseToHex(publicKeyBuffer);
            //convert public key to JWK for storage
            const publicKey = coseToJwk(publicKeyBuffer);

            authenticatorData.attestedCredentialData = {
                aaguid,
                credentialId,
                credentialIdLength,
                publicKeyHex,
                publicKey
            };
        }

        if (flags & 128) {
            //has extension data
            let extensionDataCbor;

            if (authenticatorData.attestedCredentialData) {
                extensionDataCbor = cbor.decodeAllSync(authData.slice(55 + authenticatorData.attestedCredentialData.credentialIdLength, authData.length));
                extensionDataCbor = extensionDataCbor[1]; //second element
            } else {
                extensionDataCbor = cbor.decodeFirstSync(authData.slice(37, authData.length));
            }

            authenticatorData.extensionDataHex = cbor.encode(extensionDataCbor).toString('hex').toUpperCase();
        }
        else
        {
            authenticatorData.extensionDataHex = "No extension data";
        }

        return authenticatorData;
    } catch (e) {
        throw new Error("Authenticator Data could not be parsed")
    }
}