C# 关于爬取网站数据遇到csrf-token的分析与解决

需求

某航空公司物流单信息查询，是一个post请求。通过后台模拟POST HTTP请求发现无法获取页面数据，通过查看航空公司网站后，发现网站使用避免CSRF攻击机制，直接发挥40X错误。

关于CSRF

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网站HTTP请求分析 

Headers 

Form Data

在head里包含了cookie 与 x-csrf-token  formdata 里包含了_csrf （与head里的值是一样的）.

这里通过查看该网站的JS源代码发现_csrf 来自于网页的head标签里

猜测cookie与 x-csrf-token是有一定的有效期，并且他们共同作用来防御CSRF攻击。

解决方案

1，首先请求一下该航空公司的网站，获取cookie与_csrf

2，然后C# 模拟http分别在head和formdata里加入如上参数，发起请求

代码

public class CSRFToken
{
string cookie;//用于请求的站点的cookie
List<string> csrfs;//用于请求站点的token的key 以及 value

public CSRFToken(string url)
{
 //校验传输安全
 if (!string.IsNullOrWhiteSpace(url))
 {
 try
 {
  //设置请求的头信息.获取url的host
  var _http = new HttpHelper(url);
  string cookie;
  string html = _http.CreateGetHttpResponseForPC(out cookie);
  this.cookie = cookie;

string headRegex = @"<meta name=""_csrf.*"" content="".*""/>";

MatchCollection matches = Regex.Matches(html, headRegex);
  Regex re = new Regex("(?<=content=\").*?(?=\")", RegexOptions.None);
  csrfs = new List<string>();
  foreach (Match math in matches)
  {

MatchCollection mc = re.Matches(math.Value);
  foreach (Match ma in mc)
  {
   csrfs.Add(ma.Value);
  }
  }

}
 catch (Exception e)
 {

}
 }
}

public String getCookie()
{
 return cookie;
}
public void setCookie(String cookie)
{
 this.cookie = cookie;
}
public List<string> getCsrf_token()
{
 return csrfs;
}
}

httpHelper

public string CreatePostHttpResponse(IDictionary<string, string> headers, IDictionary<string, string> parameters)
 {
  HttpWebRequest request = null;
  //HTTPSQ请求
  UTF8Encoding encoding = new System.Text.UTF8Encoding();
  ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
  request = WebRequest.Create(_baseIPAddress) as HttpWebRequest;
  request.ProtocolVersion = HttpVersion.Version10;
  ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11;
  request.Method = "POST";
  request.ContentType = "application/x-www-form-urlencoded";
  // request.ContentType = "application/json";
  request.UserAgent = DefaultUserAgent;
  //request.Headers.Add("X-CSRF-TOKEN", "bc0cc533-60cc-484a-952d-0b4c1a95672c");
  //request.Referer = "https://www.asianacargo.com/tracking/viewTraceAirWaybill.do";

//request.Headers.Add("Origin", "https://www.asianacargo.com");
  //request.Headers.Add("Cookie", "JSESSIONID=HP21d2Dq5FoSlG4Fyw4slWwHb0-Sl1CG6jGtj7HE41e5f4aN_R1p!-435435446!117330181");
  //request.Host = "www.asianacargo.com";

if (!(headers == null || headers.Count == 0))
  {

foreach (string key in headers.Keys)
   {
    request.Headers.Add(key, headers[key]);
   }

}

//如果需要POST数据  
  if (!(parameters == null || parameters.Count == 0))
  {
   StringBuilder buffer = new StringBuilder();
   int i = 0;
   foreach (string key in parameters.Keys)
   {
    if (i > 0)
    {
     buffer.AppendFormat("&{0}={1}", key, parameters[key]);
    }
    else
    {
     buffer.AppendFormat("{0}={1}", key, parameters[key]);
    }
    i++;
   }
   byte[] data = encoding.GetBytes(buffer.ToString());
   using (Stream stream = request.GetRequestStream())
   {
    stream.Write(data, 0, data.Length);
   }
  }

HttpWebResponse response;

try
  {
   //获得响应流
   response = (HttpWebResponse)request.GetResponse();
   Stream s = response.GetResponseStream();

StreamReader readStream = new StreamReader(s, Encoding.UTF8);
   string SourceCode = readStream.ReadToEnd();
   response.Close();
   readStream.Close();
   return SourceCode;
  }
  catch (WebException ex)
  {
   response = ex.Response as HttpWebResponse; return null;
  }

}

public string CreateGetHttpResponse(out string cookie)
 {
  HttpWebRequest request = null;
  //HTTPSQ请求
  UTF8Encoding encoding = new System.Text.UTF8Encoding();
  ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
  request = WebRequest.Create(_baseIPAddress) as HttpWebRequest;
  request.ProtocolVersion = HttpVersion.Version10;
  ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11;
  request.Method = "GET";
  request.ContentType = "application/x-www-form-urlencoded";
  request.UserAgent = DefaultUserAgent;

HttpWebResponse response;

try
  {
   //获得响应流
   response = (HttpWebResponse)request.GetResponse();

cookie = response.Headers["Set-Cookie"];
   Stream s = response.GetResponseStream();

StreamReader readStream = new StreamReader(s, Encoding.UTF8);
   string SourceCode = readStream.ReadToEnd();
   response.Close();
   readStream.Close();
   return SourceCode;
  }
  catch (WebException ex)
  {
   response = ex.Response as HttpWebResponse;
   cookie = "";
   return null;
  }

}

爬取程序

爬取结果

浏览器结果

注意事项与结论

1，不同的网站，获取cstf的方式不一样，无论怎么做，只要信息传到前台我们都可以有相应的方法来获取。

2，请求时候的http验证可能不一样，测试的某航空公司物流信息的时候，http请求的安全协议是tis12。

 ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11; 还有其他参数比如UserAgent后台可能也会验证

3,基于如上航空公司，发现它的cookie和cstf_token一定时间内不会改变，那么当实际爬取的时候可以考虑缓存cookie以及cstf_token,只有当请求失败的时候，才重新获取

来源：https://www.cnblogs.com/yibey/p/10870472.html