From d5d574eb95391887ad90cfb8eaae7ed5f8abee74 Mon Sep 17 00:00:00 2001
From: Marek Habersack <grendel@twistedcode.net>
Date: Fri, 26 May 2017 14:40:50 +0200
Subject: [PATCH] A collection of assorted enhancements to AndroidClientHandler

The changes are result of a
bug (https://bugzilla.xamarin.com/show_bug.cgi?id=55477) followup and are based
on code and ideas from Jeremy Cook <jeremy.cook@hp.com>:

 * If `UseProxy == false` instantiate Java URLConnection that doesn't use the
   system proxy. This is important for code that accesses local resources from a
   device otherwise configured to use a proxy.

 * Allow for insecure SSL requests: let the code bypass SSL host name and
   certificate checks. This is necessary for code that connects to devices with
   self-signed or otherwise "invalid" SSL certificates as well as ones which do
   not have valid DNS entries set up for them.
	 The implementation makes it possible to use a custom host name verifier and
   also to provide a custom socket factory.
---
 .../AndroidClientHandler.cs                   | 50 ++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs b/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs
index 036634954fb..357dc2c5556 100644
--- a/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs
+++ b/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs
@@ -219,6 +219,20 @@ string EncodeUrl (Uri url)
 			return bldr.ToString ();
 		}
 
+		/// <summary>
+		/// Returns a custom host name verifier for a HTTPS connection. By default it returns <c>null</c> and
+		/// thus the connection uses whatever host name verification mechanism the operating system defaults to.
+		/// Override in your class to define custom host name verification behavior. The overriding class should
+		/// not set the <see cref="m:HttpsURLConnection.HostnameVerifier"/> property directly on the passed
+		/// <paramref name="connection"/>
+		/// </summary>
+		/// <returns>Instance of IHostnameVerifier to be used for this HTTPS connection</returns>
+		/// <param name="connection">HTTPS connection object.</param>
+		protected virtual IHostnameVerifier GetSSLHostnameVerifier (HttpsURLConnection connection)
+		{
+			return null;
+		}
+
 		/// <summary>
 		/// Creates, configures and processes an asynchronous request to the indicated resource.
 		/// </summary>
@@ -241,7 +255,19 @@ string EncodeUrl (Uri url)
 			};
 			while (true) {
 				URL java_url = new URL (EncodeUrl (redirectState.NewUrl));
-				URLConnection java_connection = java_url.OpenConnection ();
+				URLConnection java_connection;
+				if (UseProxy)
+					java_connection = java_url.OpenConnection ();
+				else
+					java_connection = java_url.OpenConnection (Java.Net.Proxy.NoProxy);
+
+				var httpsConnection = java_connection as HttpsURLConnection;
+				if (httpsConnection != null) {
+					IHostnameVerifier hnv = GetSSLHostnameVerifier (httpsConnection);
+					if (hnv != null)
+						httpsConnection.HostnameVerifier = hnv;
+				}
+
 				if (ConnectTimeout != TimeSpan.Zero)
 					java_connection.ConnectTimeout = checked ((int)ConnectTimeout.TotalMilliseconds);
 
@@ -729,11 +755,33 @@ void AppendEncoding (string encoding, ref List <string> list)
 			return httpConnection;
 		}
 
+		/// <summary>
+		/// Configure and return a custom <see cref="t:SSLSocketFactory"/> for the passed HTTPS <paramref
+		/// name="connection"/>. If the class overriding the method returns anything but the default
+		/// <c>null</c>, the SSL setup code will not call the <see cref="ConfigureKeyManagerFactory"/> nor the
+		/// <see cref="ConfigureTrustManagerFactory"/> methods used to configure a custom trust manager which is
+		/// then used to create a default socket factory.
+		/// Deriving class must perform all the key manager and trust manager configuration to ensure proper
+		/// operation of the returned socket factory.
+		/// </summary>
+		/// <returns>Instance of SSLSocketFactory ready to use with the HTTPS connection.</returns>
+		/// <param name="connection">HTTPS connection to return socket factory for</param>
+		protected virtual SSLSocketFactory ConfigureCustomSSLSocketFactory (HttpsURLConnection connection)
+		{
+			return null;
+		}
+
 		void SetupSSL (HttpsURLConnection httpsConnection)
 		{
 			if (httpsConnection == null)
 				return;
 
+			SSLSocketFactory socketFactory = ConfigureCustomSSLSocketFactory (httpsConnection);
+			if (socketFactory != null) {
+				httpsConnection.SSLSocketFactory = socketFactory;
+				return;
+			}
+
 			KeyStore keyStore = KeyStore.GetInstance (KeyStore.DefaultType);
 			keyStore.Load (null, null);
 			bool gotCerts = TrustedCerts?.Count > 0;