From 11cb134490bc2e6c0643a3baacc6acb5929fd54c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9D=8E=E5=85=89=E6=98=A5?= <gc@dtapp.net>
Date: Fri, 2 Sep 2022 17:44:51 +0800
Subject: [PATCH] - add sign.decrypt

---
 const.go        |  2 +-
 sign.decrypt.go | 87 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+), 1 deletion(-)
 create mode 100644 sign.decrypt.go

diff --git a/const.go b/const.go
index 234c104..78a4619 100644
--- a/const.go
+++ b/const.go
@@ -3,5 +3,5 @@ package wechatopen
 const (
 	apiUrl   = "https://api.weixin.qq.com"
 	logTable = "wechatopen"
-	Version  = "1.0.23"
+	Version  = "1.0.24"
 )
diff --git a/sign.decrypt.go b/sign.decrypt.go
new file mode 100644
index 0000000..d90900a
--- /dev/null
+++ b/sign.decrypt.go
@@ -0,0 +1,87 @@
+package wechatopen
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"strings"
+)
+
+type SignDecryptParams struct {
+	Signature    string `json:"signature"`
+	Timestamp    string `json:"timestamp"`
+	Nonce        string `json:"nonce"`
+	EncryptType  string `json:"encrypt_type"`
+	MsgSignature string `json:"msg_signature"`
+	AppId        string `json:"app_id"`
+	Encrypt      string `json:"encrypt"`
+}
+
+// SignDecrypt 解密
+func (c *Client) SignDecrypt(ctx context.Context, params SignDecryptParams, strXml interface{}) ([]byte, error) {
+
+	if params.Signature == "" {
+		return nil, errors.New("找不到签名参数")
+	}
+
+	if params.Timestamp == "" {
+		return nil, errors.New("找不到时间戳参数")
+	}
+
+	if params.Nonce == "" {
+		return nil, errors.New("未找到随机数参数")
+	}
+
+	wantSignature := Sign(c.GetMessageToken(), params.Timestamp, params.Nonce)
+	if params.Signature != wantSignature {
+		return nil, errors.New("签名错误")
+	}
+
+	// 进入事件执行
+	if params.EncryptType != "aes" {
+		return nil, errors.New("未知的加密类型: " + params.EncryptType)
+	}
+	if params.Encrypt == "" {
+		return nil, errors.New("找不到签名参数")
+	}
+
+	cipherData, err := base64.StdEncoding.DecodeString(params.Encrypt)
+	if err != nil {
+		return nil, errors.New(fmt.Sprintf("Encrypt 解码字符串错误：%v", err))
+	}
+
+	AesKey, err := base64.StdEncoding.DecodeString(c.GetMessageKey() + "=")
+	if err != nil {
+		return nil, errors.New(fmt.Sprintf("messageKey 解码字符串错误：%v", err))
+	}
+
+	msg, err := AesDecrypt(cipherData, AesKey)
+	if err != nil {
+		return nil, errors.New(fmt.Sprintf("AES解密错误：%v", err))
+	}
+
+	str := string(msg)
+
+	left := strings.Index(str, "<xml>")
+	if left <= 0 {
+		return nil, errors.New(fmt.Sprintf("匹配不到<xml>：%v", left))
+	}
+	right := strings.Index(str, "</xml>")
+	if right <= 0 {
+		return nil, errors.New(fmt.Sprintf("匹配不到</xml>：%v", right))
+	}
+	msgStr := str[left:right]
+	if len(msgStr) == 0 {
+		return nil, errors.New(fmt.Sprintf("提取错误：%v", msgStr))
+	}
+
+	strByte := []byte(msgStr + "</xml>")
+	err = xml.Unmarshal(strByte, strXml)
+	if err != nil {
+		return nil, errors.New(fmt.Sprintf("解析错误：%v", err))
+	}
+
+	return strByte, nil
+}