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-"; 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