webclient https

2018-08-19

https://stackoverflow.com/questions/20064505/requesting-html-over-https-with-c-sharp-webclient

Requesting html over https with c# Webclient

down votefavI am attempting various html resources via c# WebClient class from a site I have no control over. When I attempt to access urls such as "https://archive.org/details/OTRR_In_The_Name_Of_The_Law_Singles"

I get the error: System.Net.WebException: The request was aborted: Could not create SSL/TLS secure channel.

I have found solutions that suggest I use the following code to ignore the certificate requirement and to make the webclient act as a browser, but I still recieve the same error

 ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(
            delegate
            {
                return true;
            });
            using(WebClient webClient = new WebClient()) {
                webClient.Headers["User-Agent"] = "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.6) Gecko/20100625 Firefox/3.6.6 (.NET CLR 3.5.30729)";
                webClient.Headers["Accept"] = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
                webClient.Headers["Accept-Language"] = "en-us,en;q=0.5";
                webClient.Headers["Accept-Encoding"] = "gzip,deflate";
                webClient.Headers["Accept-Charset"] = "ISO-8859-1,utf-8;q=0.7,*;q=0.7";
                StreamReader sr = new StreamReader(webClient.OpenRead(inputString));
}

down vote

The server you are accessing doesn't support TLS so you will need to force it to use SSL3.

Add the following line to your call:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;

Here's a fully working example:

using System;
using System.IO;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;

class Program
{
    static void Main(string[] args)
    {
        Uri address = new Uri("https://archive.org/details/OTRR_In_The_Name_Of_The_Law_Singles");

        ServicePointManager.ServerCertificateValidationCallback += ValidateRemoteCertificate;
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 ;

        using (WebClient webClient = new WebClient())
        {
            var stream = webClient.OpenRead(address);
            using (StreamReader sr =new StreamReader(stream))
            {
                var page = sr.ReadToEnd();
            }
        }
    }

    /// <summary>
    /// Certificate validation callback.
    /// </summary>
    private static bool ValidateRemoteCertificate(object sender, X509Certificate cert, X509Chain chain, SslPolicyErrors error)
    {
        // If the certificate is a valid, signed certificate, return true.
        if (error == System.Net.Security.SslPolicyErrors.None)
        {
            return true;
        }

        Console.WriteLine("X509Certificate [{0}] Policy Error: '{1}'",
            cert.Subject,
            error.ToString());

        return false;
    }

There are 4 SecurityProtocolType options: Ssl3, Tls, Tls11, Tls12. I had to try each one to find that Tls12 worked for me.

Just add this line before var stream = webClient.OpenRead(address);

System.Net.ServicePointManager.ServerCertificateValidationCallback += (send, certificate, chain, sslPolicyErrors) => { return true; };

That should sort out the SSL/TLS error

in .net Framework 4.0 add

ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072; //TLS 1.2