Change type of RemoteCertificate property in TlsHandler to X509Certif…

…icate2 (#231)

* Change type of RemoteCertificate property in TlsHandler to X509Certificate2

* Add null check for RemoteCertificate

* Address comments

src/DotNetty.Handlers/Tls/TlsHandler.cs

@@ -62,21 +62,15 @@ public TlsHandler(Func<Stream, SslStream> sslStreamFactory, TlsSettings settings
 
         public static TlsHandler Server(X509Certificate certificate) => new TlsHandler(new ServerTlsSettings(certificate));
 
-        public X509Certificate LocalCertificate => this.sslStream.LocalCertificate;
+        // using workaround mentioned here: https://github.com/dotnet/corefx/issues/4510
+        public X509Certificate2 LocalCertificate => this.sslStream.LocalCertificate as X509Certificate2 ?? new X509Certificate2(this.sslStream.LocalCertificate?.Export(X509ContentType.Cert));
 
-        public X509Certificate RemoteCertificate => this.sslStream.RemoteCertificate;
+        public X509Certificate2 RemoteCertificate => this.sslStream.RemoteCertificate as X509Certificate2 ?? new X509Certificate2(this.sslStream.RemoteCertificate?.Export(X509ContentType.Cert));
 
         bool IsServer => this.settings is ServerTlsSettings;
 
         public void Dispose() => this.sslStream?.Dispose();
 
-        public X509Certificate2 GetRemoteCertificate()
-        {
-            // Cannot cast from X509Certificate to X509Certificate2
-            // using workaround mentioned here: https://github.com/dotnet/corefx/issues/4510
-            return new X509Certificate2(this.sslStream.RemoteCertificate.Export(X509ContentType.Cert));
-        }
-
         public override void ChannelActive(IChannelHandlerContext context)
         {
             base.ChannelActive(context);