Change TLS 1.0 to TLS1.2 for Push notifications (#766)

Author: ggallotti

dotnet/src/dotnetframework/SDNetAPI/IOSNotifications.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -177,7 +177,7 @@ private static bool DoCall(string server, string p12path, int port, Action<SslSt
 
                         try
                         {
-                            sslStream.AuthenticateAsClient(server, clientCertificateCollection, SslProtocols.Tls, true);
+                            sslStream.AuthenticateAsClient(server, clientCertificateCollection, SslProtocols.Tls12, true);
                         }
                         catch (Exception e)
                         {

dotnet/src/dotnetframework/SDNetAPI/PushSharp/Platforms/Apple/ApplePushChannel.cs

@@ -384,8 +384,7 @@ void connect()
 
 				try
 				{
-					stream.AuthenticateAsClient(this.appleSettings.Host, this.certificates, System.Security.Authentication.SslProtocols.Tls, false);
-					//stream.AuthenticateAsClient(this.appleSettings.Host);
+					stream.AuthenticateAsClient(this.appleSettings.Host, this.certificates, System.Security.Authentication.SslProtocols.Tls12, false);					
 				}
 				catch (System.Security.Authentication.AuthenticationException ex)
 				{

dotnet/src/dotnetframework/SDNetAPI/PushSharp/Platforms/Apple/FeedbackService.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -44,7 +44,7 @@ public void Run(ApplePushChannelSettings settings/*, CancellationToken cancelTok
 				(sender, cert, chain, sslErrs) => { return true; },
 				(sender, targetHost, localCerts, remoteCert, acceptableIssuers) => { return certificate; });
 
-			stream.AuthenticateAsClient(settings.FeedbackHost, certificates, System.Security.Authentication.SslProtocols.Tls, false);
+			stream.AuthenticateAsClient(settings.FeedbackHost, certificates, System.Security.Authentication.SslProtocols.Tls12, false);
 
 
 			//Set up