minhhungit · January 19, 2023 00:44 · Jul 30, 2016 · Jul 30, 2016 · Jul 30, 2016
diff --git a/CloudflareHttpHandler.cs b/CloudflareHttpHandler.cs
@@ -0,0 +1,76 @@
+using System;
+using System.Net.Http;
+using System.Threading.Tasks;
+using System.Text.RegularExpressions;
+using System.Threading;
+using System.Collections.Generic;
+using System.Linq;
+
+using Microsoft.ClearScript.V8;
+
+using HtmlAgilityPack;
+
+/// <summary>
+/// A custom Http handler for Cloudflare protected servers
+/// </summary>
+public class CloudflareHttpHandler : HttpClientHandler
+{
+	protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+	{
+		var task = base.SendAsync(request, cancellationToken);
+
+		var response = task.Result;
+
+		if(base.CookieContainer.GetCookieHeader(request.RequestUri).Contains("cf_clearance"))
+			return task;
+
+		IEnumerable<string> values;
+
+		if(response.Headers.TryGetValues("refresh", out values) && values.FirstOrDefault().Contains("URL=/cdn-cgi/") && response.Headers.Server.ToString() == "cloudflare-nginx" )
+		{
+			Console.WriteLine("Solving cloudflare challenge . . . ");
+
+			string content = response.Content.ReadAsStringAsync().Result;
+
+			var htmlDocument = new HtmlDocument();
+			htmlDocument.LoadHtml(content);
+
+			var jschl_vc = htmlDocument.DocumentNode.SelectSingleNode(@".//input[@name=""jschl_vc""]").Attributes["value"].Value;
+			var pass = htmlDocument.DocumentNode.SelectSingleNode(@".//input[@name=""pass""]").Attributes["value"].Value;
+
+			var script = htmlDocument.DocumentNode.SelectSingleNode(@".//script").InnerText;
+
+			var regex = new string[3] {
+				@"setTimeout\(function\(\){(.+)},\s*\d*\s*\)\s*;",
+				@"^\n*\s*(var\s+.*?;)",
+				@"(?<=\s+;)(.+t.length;)"
+			};
+
+			string function, vars, calc;
+
+			function = Regex.Match(script, regex[0], RegexOptions.Singleline).Value;
+			vars = Regex.Match(function, regex[1], RegexOptions.Multiline).Value;
+			calc = Regex.Match(function, regex[2], RegexOptions.Singleline).Value
+				.Replace("a.value", "var result")
+            	.Replace("t.length", (request.RequestUri.Host.Length).ToString());;
+
+            object result;
+            using(var engine = new V8ScriptEngine())
+            	result = engine.Evaluate("function getAnswer() {" + vars + calc + "return result;" + "} getAnswer();");
+
+            Thread.Sleep(5000);
+
+            var requestUri = request.RequestUri;
+
+            request.RequestUri = new Uri(requestUri, String.Format("cdn-cgi/l/chk_jschl?jschl_vc={0}&pass={1}&jschl_answer={2}", jschl_vc, pass, result.ToString()));
+
+            base.SendAsync(request, cancellationToken).Wait();
+
+            request.RequestUri = requestUri;
+
+            return base.SendAsync(request, cancellationToken);
+		}
+
+		return task;
+	}
+}