用 .NET Core 生成微信JS-SDK需要的签名

在使用微信的 JS-SDK 进行微信公众号开发或是企业微信开发时，首先需要通过服务端程序去生成对应于前端每个页面的签名。本文演示如何在 .NET Core 3.1 以上版本中生成该签名。

获取企业通讯的Token

要生成 JS-SDK 的签名，首先需要通过微信服务端API获取对应的通讯 JS Ticket，而要获取 JS Ticket, 必须先获取与企业API访问相关的 Token。

为获取 Token , 我们使用微信服务端API, URL 为(可参考):

1	https://qyapi.weixin.qq.com/cgi-bin/gettoken

示例代码如下:

private async Task<CropToken> getWxToken(string corpId, string secret)
{

    using (HttpClient client = new HttpClient())
    {
        string url = "https://qyapi.weixin.qq.com/cgi-bin/gettoken";
        url += "?corpid=" + corpId;
        url += "&corpsecret=" + secret;


        HttpResponseMessage response = await client.GetAsync(url);
        response.EnsureSuccessStatusCode();

        string responseBody = await response.Content.ReadAsStringAsync();

        var res = JsonSerializer.Deserialize<WxApiGetToken>(responseBody);

        using (var db = new WxContext())
        {
            CropToken cropToken = db.CropTokens.SingleOrDefault<CropToken>(t => t.CorpId == this.corpId);
            if (cropToken != null)
            {
                cropToken.AccessToken = res.accessToken;
                cropToken.ExpiresIn = res.expiresIn;
                cropToken.LastUpdateTime = new DateTimeOffset(DateTime.Now).ToUnixTimeSeconds();
                db.CropTokens.Update(cropToken);
            }
            else
            {
                cropToken = new CropToken();
                cropToken.CorpId = corpId;
                cropToken.AppSecret = secret;
                cropToken.AccessToken = res.accessToken;
                cropToken.ExpiresIn = res.expiresIn;
                cropToken.LastUpdateTime = new DateTimeOffset(DateTime.Now).ToUnixTimeSeconds();
                db.CropTokens.Add(cropToken);
            }

            await db.SaveChangesAsync();
            return cropToken;
        }

    }
}

注意: 在上面的代码中，为了避免频繁的访问微信服务端API, 我们将获取到的token 保存在本地数据库中

获取 JS Ticket

获取了 Token 以后，就可以用该 Token 继续获取 JS Ticket 了。参考微信服务端API文档, 对应的代码如下:

private async Task<JsTicket> GetJsTicket()
{

    using (HttpClient client = new HttpClient())
    {

        using (var db = new WxContext())
        {

             CropToken cropToken = db.CropTokens.SingleOrDefault<CropToken>(t => t.CorpId == this.corpId);

            if (cropToken == null)
            {

                cropToken = await getWxToken(this.corpId, this.secret);
            }

            string url = "https://qyapi.weixin.qq.com/cgi-bin/get_jsapi_ticket";
            url += "?access_token=" + cropToken.AccessToken;

            HttpResponseMessage response = await client.GetAsync(url);
            response.EnsureSuccessStatusCode();

            string responseBody = await response.Content.ReadAsStringAsync();

            var res = JsonSerializer.Deserialize<WxApiJsTicket>(responseBody);

            JsTicket jsTicket = new JsTicket();
            jsTicket.CorpId = this.corpId;
            jsTicket.Ticket = res.ticket;
            jsTicket.ExpiresIn = res.expiresIn;
            jsTicket.LastUpdateTime = new DateTimeOffset(DateTime.Now).ToUnixTimeSeconds();

            db.JsTickets.Add(jsTicket);

            await db.SaveChangesAsync();

            return jsTicket;

        }
    }
}

生成 JS-SDK 需要的签名

因为 JS-SDK 签名是针对前端的每个页面的，因此需要前端将当前页面的 URL 作为参数传到后端，后端的示例代码如下:

[HttpGet("enable")]
public async Task<ApiResult> enableJsSDK()
{
    string url = Request.Query["url"];

    _logger.LogDebug("enableJsSDK, url = {0}", url);

    long timestamp = (new DateTimeOffset(DateTime.Now).ToUnixTimeSeconds()) / 1000;
    string noncestr = getRandomStr();
    string jsapiTicket = (await GetJsTicket()).Ticket;
    string signature = SHA1_Hash("jsapi_ticket=" + jsapiTicket + "&noncestr=" + noncestr + "&timestamp=" + timestamp + "&url=" + url);

    ApiResult result = new ApiResult();
    result.Succ = true;

    ConfigVo config = new ConfigVo();
    config.Timestamp = timestamp;
    config.NonceStr = noncestr;
    config.Signature = signature;
    config.AppId = this.corpId;

    result.Data = config;

    return result;
}

返回的数据为前端在页面上配置 js-sdk 时需要的信息。

其中分别调用生成随机串和生成 SHA1 加密串的程序，如下:

private string getRandomStr() {

     Random rnd = new Random();
     string res = "";
     for (int i = 0; i < 16; i++) {
         res += RANDOM_STR.ElementAt(rnd.Next(RANDOM_STR.Length));
     }
     
     return res;
 }


 //SHA1哈希加密算法  
 public string SHA1_Hash(string str_sha1_in)  
 {  
     SHA1 sha1 = new SHA1CryptoServiceProvider();  
     byte[] bytes_sha1_in = System.Text.UTF8Encoding.Default.GetBytes(str_sha1_in);  
     byte[] bytes_sha1_out = sha1.ComputeHash(bytes_sha1_in);  
     string str_sha1_out = BitConverter.ToString(bytes_sha1_out);  
     str_sha1_out = str_sha1_out.Replace("-", "").ToLower();  
     return str_sha1_out;  
 }