Merge branch 'feature/captchapng' into release/5.2

@@ -95,8 +95,21 @@ let verifyMobile = (req, res, next) => {
     let mobile = +req.body.phoneNum;
     let area = +(req.body.areaCode || 86);
     let captcha = (req.body.captcha || '').trim();
+    let diffCaptcha = _.get(req.session, 'phoneReg.captcha');
 
-    if (captcha !== _.get(req.session, 'phoneReg.captcha')) {
+    // error case： 没有验证码
+    if (!diffCaptcha) {
+        return res.json({
+            code: 400,
+            message: '请求失败',
+            refreshCaptcha: true
+        });
+    }
+
+    delete req.session.phoneReg.captcha; // captcha 一次性
+
+    // error case: 验证码不匹配
+    if (captcha !== diffCaptcha) {
         return res.json({
             code: 400,
             message: '校验码不正确',