C# 关于爬取网站数据遇到csrf-token的分析与解决
作者：yibey
这篇文章主要介绍了C# 关于爬取网站数据遇到csrf-token的分析与解决,帮助大家更好的理解和学习c#，感兴趣的朋友可以了解下
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
读者自行百度
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