https://api.mch.weixin.qq.com/xdc/apiv2getsignkey/sign/getsignkey

<xml>
<mch_id><![CDATA[1574517161]]></mch_id>
<nonce_str><![CDATA[4909e81afe374ace9c0aa6bcf4e479d8]]></nonce_str>
<sign><![CDATA[7DE73AD24FBC42D02EA4CD1B2A43224D]]></sign>
</xml>

检验正确

返回错误信息

<xml>
  <return_code><![CDATA[FAIL]]></return_code>
  <return_msg><![CDATA["mch_id" is required. "sign" is required. "nonce_str" is required]]></return_msg>
</xml>