如何使用cloudflare ddos保护从页面获取html？
如何使用cloudflare ddos保护从页面获取html？
提问于 2015-09-07 00:51:16
我使用htmlagility来获取网页数据，但我尝试了所有使用www.cloudflare.com保护网页的方法。重定向页面不可能在htmlagility中处理，因为它们不能用meta或js重定向，我想它们会检查你是否已经用cookie检查过了，我用c#模拟失败了。当我得到这个页面时，html代码来自登陆cloadflare页面。
回答 4
Stack Overflow用户
发布于 2015-09-07 01:01:13
前段时间我也遇到过这个问题。cloudflare真正的解决方案是解决cloudflare网站给你的挑战(你需要使用javascript计算正确的答案，然后把它发回来，然后你会收到一个cookie /你的令牌，你可以用它继续浏览网站)。所以你通常会看到的页面就像这样
最后，我只调用了一个带有shell-execute的python-script。我使用了this github fork中提供的模块。这也可以作为在C#中实现cloudflare anti-dDoS页面规避的起点。
仅供参考，我为个人使用而编写的python脚本只是将cookie写在一个文件中。我稍后使用C#再次阅读了它，并将其存储在CookieJar中，以便继续在C#中浏览页面。
#!/usr/bin/env python
import cfscrape
import sys
scraper = cfscrape.create_scraper() # returns a requests.Session object
fd = open("cookie.txt", "w")
c = cfscrape.get_cookie_string(sys.argv[1])
fd.write(str(c))
fd.close()
print(c)编辑:重复一遍，这与cookie几乎没有什么关系！Cloudflare迫使您使用javascript命令来解决真正的挑战。这并不像接受cookie并在以后使用它那么简单。看看https://github.com/Anorov/cloudflare-scrape/blob/master/cfscrape/.py和大约40行javascript模拟来解决这个挑战。
Edit2:我也看到人们使用完全成熟的浏览器对象(这是，而不是)来访问网站，并在页面加载时订阅某些事件，而不是编写一些东西来规避保护。使用WebBrowser类创建一个无限小的浏览器窗口并订阅适当的事件。
Edit3:好的，我实际上实现了C#的方式来做这件事。它使用.NET的JavaScript Engine Jint，可通过https://www.nuget.org/packages/Jint获得
处理cookie的代码很难看，因为尽管标头包含Set-Cookie部分，但有时HttpResponse类不会提取cookie。
using System;
using System.Net;
using System.IO;
using System.Text.RegularExpressions;
using System.Web;
using System.Collections;
using System.Threading;
namespace Cloudflare_Evader
{
public class CloudflareEvader
{
/// <summary>
/// Tries to return a webclient with the neccessary cookies installed to do requests for a cloudflare protected website.
/// </summary>
/// <param name="url">The page which is behind cloudflare's anti-dDoS protection</param>
/// <returns>A WebClient object or null on failure</returns>
public static WebClient CreateBypassedWebClient(string url)
{
var JSEngine = new Jint.Engine(); //Use this JavaScript engine to compute the result.
//Download the original page
var uri = new Uri(url);
HttpWebRequest req =(HttpWebRequest) WebRequest.Create(url);
req.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:40.0) Gecko/20100101 Firefox/40.0";
//Try to make the usual request first. If this fails with a 503, the page is behind cloudflare.
try
{
var res = req.GetResponse();
string html = "";
using (var reader = new StreamReader(res.GetResponseStream()))
html = reader.ReadToEnd();
return new WebClient();
}
catch (WebException ex) //We usually get this because of a 503 service not available.
{
string html = "";
using (var reader = new StreamReader(ex.Response.GetResponseStream()))
html = reader.ReadToEnd();
//If we get on the landing page, Cloudflare gives us a User-ID token with the cookie. We need to save that and use it in the next request.
var cookie_container = new CookieContainer();
//using a custom function because ex.Response.Cookies returns an empty set ALTHOUGH cookies were sent back.
var initial_cookies = GetAllCookiesFromHeader(ex.Response.Headers["Set-Cookie"], uri.Host);
foreach (Cookie init_cookie in initial_cookies)
cookie_container.Add(init_cookie);
/* solve the actual challenge with a bunch of RegEx's. Copy-Pasted from the python scrapper version.*/
var challenge = Regex.Match(html, "name=\"jschl_vc\" value=\"(\\w+)\"").Groups[1].Value;
var challenge_pass = Regex.Match(html, "name=\"pass\" value=\"(.+?)\"").Groups[1].Value;
var builder = Regex.Match(html, @"setTimeout\(function\(\){\s+(var t,r,a,f.+?\r?\n[\s\S]+?a\.value =.+?)\r?\n").Groups[1].Value;
builder = Regex.Replace(builder, @"a\.value =(.+?) \+ .+?;", "$1");
builder = Regex.Replace(builder, @"\s{3,}[a-z](?: = |\.).+", "");
//Format the javascript..
builder = Regex.Replace(builder, @"[\n\\']", "");
//Execute it.
long solved = long.Parse(JSEngine.Execute(builder).GetCompletionValue().ToObject().ToString());
solved += uri.Host.Length; //add the length of the domain to it.
Console.WriteLine("***** SOLVED CHALLENGE ******: " + solved);
Thread.Sleep(3000); //This sleeping IS requiered or cloudflare will not give you the token!!
//Retreive the cookies. Prepare the URL for cookie exfiltration.
string cookie_url = string.Format("{0}://{1}/cdn-cgi/l/chk_jschl", uri.Scheme, uri.Host);
var uri_builder = new UriBuilder(cookie_url);
var query = HttpUtility.ParseQueryString(uri_builder.Query);
//Add our answers to the GET query
query["jschl_vc"] = challenge;
query["jschl_answer"] = solved.ToString();
query["pass"] = challenge_pass;
uri_builder.Query = query.ToString();
//Create the actual request to get the security clearance cookie
HttpWebRequest cookie_req = (HttpWebRequest) WebRequest.Create(uri_builder.Uri);
cookie_req.AllowAutoRedirect = false;
cookie_req.CookieContainer = cookie_container;
cookie_req.Referer = url;
cookie_req.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:40.0) Gecko/20100101 Firefox/40.0";
//We assume that this request goes through well, so no try-catch
var cookie_resp = (HttpWebResponse)cookie_req.GetResponse();
//The response *should* contain the security clearance cookie!
if (cookie_resp.Cookies.Count != 0) //first check if the HttpWebResponse has picked up the cookie.
foreach (Cookie cookie in cookie_resp.Cookies)
cookie_container.Add(cookie);
else //otherwise, use the custom function again
{
//the cookie we *hopefully* received here is the cloudflare security clearance token.
if (cookie_resp.Headers["Set-Cookie"] != null)
{
var cookies_parsed = GetAllCookiesFromHeader(cookie_resp.Headers["Set-Cookie"], uri.Host);
foreach (Cookie cookie in cookies_parsed)
cookie_container.Add(cookie);
}
else
{
//No security clearence? something went wrong.. return null.
//Console.WriteLine("MASSIVE ERROR: COULDN'T GET CLOUDFLARE CLEARANCE!");
return null;
}
}
//Create a custom webclient with the two cookies we already acquired.
WebClient modedWebClient = new WebClientEx(cookie_container);
modedWebClient.Headers.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:40.0) Gecko/20100101 Firefox/40.0");
modedWebClient.Headers.Add("Referer", url);
return modedWebClient;
}
}
/* Credit goes to https://stackoverflow.com/questions/15103513/httpwebresponse-cookies-empty-despite-set-cookie-header-no-redirect
(user https://stackoverflow.com/users/541404/cameron-tinker) for these functions
*/
public static CookieCollection GetAllCookiesFromHeader(string strHeader, string strHost)
{
ArrayList al = new ArrayList();
CookieCollection cc = new CookieCollection();
if (strHeader != string.Empty)
{
al = ConvertCookieHeaderToArrayList(strHeader);
cc = ConvertCookieArraysToCookieCollection(al, strHost);
}
return cc;
}
private static ArrayList ConvertCookieHeaderToArrayList(string strCookHeader)
{
strCookHeader = strCookHeader.Replace("\r", "");
strCookHeader = strCookHeader.Replace("\n", "");
string[] strCookTemp = strCookHeader.Split(',');
ArrayList al = new ArrayList();
int i = 0;
int n = strCookTemp.Length;
while (i < n)
{
if (strCookTemp[i].IndexOf("expires=", StringComparison.OrdinalIgnoreCase) > 0)
{
al.Add(strCookTemp[i] + "," + strCookTemp[i + 1]);
i = i + 1;
}
else
al.Add(strCookTemp[i]);
i = i + 1;
}
return al;
}
private static CookieCollection ConvertCookieArraysToCookieCollection(ArrayList al, string strHost)
{
CookieCollection cc = new CookieCollection();
int alcount = al.Count;
string strEachCook;
string[] strEachCookParts;
for (int i = 0; i < alcount; i++)
{
strEachCook = al[i].ToString();
strEachCookParts = strEachCook.Split(';');
int intEachCookPartsCount = strEachCookParts.Length;
string strCNameAndCValue = string.Empty;
string strPNameAndPValue = string.Empty;
string strDNameAndDValue = string.Empty;
string[] NameValuePairTemp;
Cookie cookTemp = new Cookie();
for (int j = 0; j < intEachCookPartsCount; j++)
{
if (j == 0)
{
strCNameAndCValue = strEachCookParts[j];
if (strCNameAndCValue != string.Empty)
{
int firstEqual = strCNameAndCValue.IndexOf("=");
string firstName = strCNameAndCValue.Substring(0, firstEqual);
string allValue = strCNameAndCValue.Substring(firstEqual + 1, strCNameAndCValue.Length - (firstEqual + 1));
cookTemp.Name = firstName;
cookTemp.Value = allValue;
}
continue;
}
if (strEachCookParts[j].IndexOf("path", StringComparison.OrdinalIgnoreCase) >= 0)
{
strPNameAndPValue = strEachCookParts[j];
if (strPNameAndPValue != string.Empty)
{
NameValuePairTemp = strPNameAndPValue.Split('=');
if (NameValuePairTemp[1] != string.Empty)
cookTemp.Path = NameValuePairTemp[1];
else
cookTemp.Path = "/";
}
continue;
}
if (strEachCookParts[j].IndexOf("domain", StringComparison.OrdinalIgnoreCase) >= 0)
{
strPNameAndPValue = strEachCookParts[j];
if (strPNameAndPValue != string.Empty)
{
NameValuePairTemp = strPNameAndPValue.Split('=');
if (NameValuePairTemp[1] != string.Empty)
cookTemp.Domain = NameValuePairTemp[1];
else
cookTemp.Domain = strHost;
}
continue;
}
}
if (cookTemp.Path == string.Empty)
cookTemp.Path = "/";
if (cookTemp.Domain == string.Empty)
cookTemp.Domain = strHost;
cc.Add(cookTemp);
}
return cc;
}
}
/*Credit goes to https://stackoverflow.com/questions/1777221/using-cookiecontainer-with-webclient-class
(user https://stackoverflow.com/users/129124/pavel-savara) */
public class WebClientEx : WebClient
{
public WebClientEx(CookieContainer container)
{
this.container = container;
}
public CookieContainer CookieContainer
{
get { return container; }
set { container = value; }
}
private CookieContainer container = new CookieContainer();
protected override WebRequest GetWebRequest(Uri address)
{
WebRequest r = base.GetWebRequest(address);
var request = r as HttpWebRequest;
if (request != null)
{
request.CookieContainer = container;
}
return r;
}
protected override WebResponse GetWebResponse(WebRequest request, IAsyncResult result)
{
WebResponse response = base.GetWebResponse(request, result);
ReadCookies(response);
return response;
}
protected override WebResponse GetWebResponse(WebRequest request)
{
WebResponse response = base.GetWebResponse(request);
ReadCookies(response);
return response;
}
private void ReadCookies(WebResponse r)
{
var response = r as HttpWebResponse;
if (response != null)
{
CookieCollection cookies = response.Cookies;
container.Add(cookies);
}
}
}
}该函数将返回一个webclient，其中包含已解决的挑战和cookie。您可以按如下方式使用它：
static void Main(string[] args)
{
WebClient client = null;
while (client == null)
{
Console.WriteLine("Trying..");
client = CloudflareEvader.CreateBypassedWebClient("http://anilinkz.tv");
}
Console.WriteLine("Solved! We're clear to go");
Console.WriteLine(client.DownloadString("http://anilinkz.tv/anime-list"));
Console.ReadLine();
}Stack Overflow用户
发布于 2018-12-06 15:57:21
一个“简单”的工作方法，如果你不使用库(有时不起作用)，它可以绕过Cloudflare。
- 打开一个“隐藏”的WebBrowser (大小为1,1左右)。
- 打开您的目标Cloudflare站点的根目录。
- 从WebClient中获取这些cookies。
确保WebBrowser和WebClient的UserAgent相同。如果在WebClient上不匹配，Cloudflare会给你一个503。
您将需要在堆栈上搜索如何从WebBrowser获取cookies以及如何修改WebClient，以便您可以将其cookies容器+修改cookies容器设置为1，或者两者都设置为相同。
由于Cloudflare中的cookies似乎永远不会过期，因此您可以将cookies序列化到某个临时位置，并在每次运行应用程序时加载它，如果失败，可能会进行验证并重新获取。
这样做已经有一段时间了，效果很好。当C#库在其他站点上工作时，无法让它们在特定的Cloudflare站点上工作。目前还不知道原因。
这也可以在IIS服务器的幕后运行，但是您必须设置“不允许”的设置。也就是说，以SYSTEM或ADMIN身份运行应用程序池，并将其设置为Classic模式。
Stack Overflow用户
发布于 2021-07-21 21:39:23
现在的答案应该包括Flaresolverr项目。它的目的是使用Docker将其部署为容器，因此您只需传递一个端口，它就会运行。
它不会影响您的项目，因为您不需要导入库。目前支持。我看到的唯一的缺点是，你需要安装Docker才能让它工作。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/32425973
复制相关文章
相似问题
腾讯云开发者
