1

I try to create an app in "Microsoft Visual Studio 2017" Xamarin Android App.

If i repelasd with http and not (https) it works fine

My qustion is: How can i reguest a https call?

Basic code:

using Android.App;
using Android.Widget;
using Android.OS;
using Android.Support.V7.App;
using System.Net.Http;
using System;
using System.Text;
using System.Net;
using System.IO;

//System.Net.WebException: Error: TrustFailure (The authentication or decryption has failed.)

namespace httprequest
{
    [Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : AppCompatActivity
    {
        private static readonly HttpClient client = new HttpClient();
        Button btn1;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.activity_main);


            if (Build.Brand.Equals("GENERIC", StringComparison.InvariantCultureIgnoreCase))
            {
                ServicePointManager.ServerCertificateValidationCallback +=
                    (sender, cert, chain, sslPolicyErrors) => true;
            }


            btn1 = FindViewById<Button>(Resource.Id.httpbtn1);

            btn1.Click += delegate
            {
                using (var wb = new WebClient())
                {
                    var request = (HttpWebRequest)WebRequest.Create("https://???");

                    request.KeepAlive = false;
                    request.ProtocolVersion = HttpVersion.Version10;

                    var response = (HttpWebResponse)request.GetResponse();

                    var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

                    Console.WriteLine(responseString);
                }
            };
        }
    }
}

Here is what i get:

Unhandled Exception: System.Net.WebException: Error: TrustFailure (One or more errors occurred.)

In Advanced Adnroid Properites:

HttpClient implementation: Android

SSL/TLS implementation: Native TLS 1.2+

Hossam Hassan
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Frederik L. Frandsen
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1 Answers1

1

Maybe it's still helping OP or someone else stumbling over this question: I wanted to access our company API that is using a certificate issued by a trusted Third Party via an Samsung S7 (Android 8) connected to our Blackberry Server. The device itself had the necessary certificate installed, but I still got the Trust Failure Exception until I switched the HTTPS-Implementation like OP said:

Right click on the Android project -> Settings -> Android-Options -> Advanced

Change the HTTPClient implementation to Android and the SSL/TLS implementation to Native TLS 1.2+

Then I got the following error:

java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.

So it seems you need to point Android to its own certificate stores. To do this follow these steps:

Create a subdirectory xml in your Resources directory

Inside, create network_security_config.xml with the following content

<?xml version="1.0" encoding="utf-8" ?>
 <network-security-config>
  <base-config>
   <trust-anchors>
    <!-- Trust preinstalled CAs -->
    <certificates src="system" />
    <!-- Additionally trust user added CAs -->
    <certificates src="user" />
  </trust-anchors>
 </base-config>
</network-security-config>

Open your AndroidManifest.xml and add the following attribute to the application-Tag

<application [...] android:networkSecurityConfig="@xml/network_security_config">

In my case it got the whole thing working without errors afterwards.

Svartkabel
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