HTTPSUtil: Improve HTTPS Check

- detect and use proxy
- do not use HTTPS in case of SocketException

Author: frauzufall

src/main/java/net/imagej/updater/util/HTTPSUtil.java

@@ -7,10 +7,18 @@
 import javax.net.ssl.SSLHandshakeException;
 import java.io.IOException;
 import java.net.HttpURLConnection;
+import java.net.InetSocketAddress;
 import java.net.ProtocolException;
+import java.net.Proxy;
+import java.net.ProxySelector;
+import java.net.SocketException;
 import java.net.SocketTimeoutException;
+import java.net.URI;
+import java.net.URISyntaxException;
 import java.net.URL;
 import java.net.UnknownHostException;
+import java.util.Iterator;
+import java.util.List;
 
 public class HTTPSUtil {
 
@@ -26,7 +34,13 @@ public class HTTPSUtil {
 	public static void checkHTTPSSupport(LogService log) {
 		HttpURLConnection connection = null;
 		try {
-			connection = (HttpURLConnection) new URL(secureURL).openConnection();
+			Proxy proxy = detectProxy(secureURL);
+			if(proxy != null) {
+				System.out.println("Detected proxy " + proxy);
+				connection = (HttpURLConnection) new URL(secureURL).openConnection(proxy);
+			} else {
+				connection = (HttpURLConnection) new URL(secureURL).openConnection();
+			}
 		} catch (IOException e) {
 			e.printStackTrace();
 		}
@@ -56,11 +70,40 @@ public static void checkHTTPSSupport(LogService log) {
 					"Please contact your system administrator to enable communication via HTTPS.";
 			if (log != null) log.warn(msg);
 			else System.out.println("[WARNING] " + msg);
+		} catch (SocketException e) {
+			secureMode = false;
+			String msg = "SocketException while trying to update securely via HTTPS. Will fall back to HTTP. This is a security risk. " +
+					"Try downloading a new version of this software.";
+			if (log != null) log.warn(msg);
+			else System.out.println("[WARNING] " + msg);
 		} catch (IOException e) {
 			e.printStackTrace();
 		}
 	}
 
+	private static Proxy detectProxy(String url) {
+//		System.setProperty("java.net.useSystemProxies", "true");
+		List l = null;
+		try {
+			l = ProxySelector.getDefault().select(new URI(url));
+		}
+		catch (URISyntaxException e) {
+			e.printStackTrace();
+		}
+		if (l != null) {
+			for (Iterator iter = l.iterator(); iter.hasNext();) {
+				java.net.Proxy proxy = (java.net.Proxy) iter.next();
+
+				InetSocketAddress addr = (InetSocketAddress) proxy.address();
+
+				if (addr != null) {
+					return proxy;
+				}
+			}
+		}
+		return null;
+	}
+
 	/**
 	 * @return whether this ImageJ instance can handle HTTPS
 	 */