AUTH_TRLR_HDR_LEN
if (a->auth_length != MD5_DIGEST_LENGTH + AUTH_TRLR_HDR_LEN) {
AUTH_TRLR_HDR_LEN - MD5_DIGEST_LENGTH) {
*len -= AUTH_TRLR_HDR_LEN + MD5_DIGEST_LENGTH;
a.auth_length = MD5_DIGEST_LENGTH + AUTH_TRLR_HDR_LEN;