Fix TLS error when connecting to GFE 3.20.4 on Android 4.x

app/src/main/java/com/limelight/nvstream/http/NvHTTP.java

@@ -1,11 +1,14 @@
 package com.limelight.nvstream.http;
 
+import android.os.Build;
+
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.Reader;
 import java.io.StringReader;
+import java.net.InetAddress;
 import java.net.MalformedURLException;
 import java.net.Socket;
 import java.net.URI;
@@ -33,6 +36,8 @@ import javax.net.ssl.SSLContext;
 import javax.net.ssl.SSLHandshakeException;
 import javax.net.ssl.SSLPeerUnverifiedException;
 import javax.net.ssl.SSLSession;
+import javax.net.ssl.SSLSocket;
+import javax.net.ssl.SSLSocketFactory;
 import javax.net.ssl.TrustManager;
 import javax.net.ssl.TrustManagerFactory;
 import javax.net.ssl.X509KeyManager;
@@ -343,7 +348,16 @@ public class NvHTTP {
         try {
             SSLContext sc = SSLContext.getInstance("TLS");
             sc.init(new KeyManager[] { keyManager }, new TrustManager[] { trustManager }, new SecureRandom());
-            return client.newBuilder().sslSocketFactory(sc.getSocketFactory(), trustManager).build();
+
+            // TLS 1.2 is not enabled by default prior to Android 5.0, so we'll need a custom
+            // SSLSocketFactory in order to connect to GFE 3.20.4 which requires TLSv1.2 or later.
+            // We don't just always use TLSv12SocketFactory because explicitly specifying TLS versions
+            // prevents later TLS versions from being negotiated even if client and server otherwise
+            // support them.
+            return client.newBuilder().sslSocketFactory(
+                    Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP ?
+                            sc.getSocketFactory() : new TLSv12SocketFactory(sc),
+                    trustManager).build();
         } catch (NoSuchAlgorithmException | KeyManagementException e) {
             throw new RuntimeException(e);
         }
@@ -727,4 +741,62 @@ public class NvHTTP {
 
         return true;
     }
+
+    // Based on example code from https://blog.dev-area.net/2015/08/13/android-4-1-enable-tls-1-1-and-tls-1-2/
+    private static class TLSv12SocketFactory extends SSLSocketFactory {
+        private SSLSocketFactory internalSSLSocketFactory;
+
+        public TLSv12SocketFactory(SSLContext context) {
+            internalSSLSocketFactory = context.getSocketFactory();
+        }
+
+        @Override
+        public String[] getDefaultCipherSuites() {
+            return internalSSLSocketFactory.getDefaultCipherSuites();
+        }
+
+        @Override
+        public String[] getSupportedCipherSuites() {
+            return internalSSLSocketFactory.getSupportedCipherSuites();
+        }
+
+        @Override
+        public Socket createSocket() throws IOException {
+            return enableTLSv12OnSocket(internalSSLSocketFactory.createSocket());
+        }
+
+        @Override
+        public Socket createSocket(Socket s, String host, int port, boolean autoClose) throws IOException {
+            return enableTLSv12OnSocket(internalSSLSocketFactory.createSocket(s, host, port, autoClose));
+        }
+
+        @Override
+        public Socket createSocket(String host, int port) throws IOException {
+            return enableTLSv12OnSocket(internalSSLSocketFactory.createSocket(host, port));
+        }
+
+        @Override
+        public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException {
+            return enableTLSv12OnSocket(internalSSLSocketFactory.createSocket(host, port, localHost, localPort));
+        }
+
+        @Override
+        public Socket createSocket(InetAddress host, int port) throws IOException {
+            return enableTLSv12OnSocket(internalSSLSocketFactory.createSocket(host, port));
+        }
+
+        @Override
+        public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
+            return enableTLSv12OnSocket(internalSSLSocketFactory.createSocket(address, port, localAddress, localPort));
+        }
+
+        private Socket enableTLSv12OnSocket(Socket socket) {
+            if (socket instanceof SSLSocket) {
+                // TLS 1.2 is not enabled by default prior to Android 5.0. We must enable it
+                // explicitly to ensure we can communicate with GFE 3.20.4 which blocks TLS 1.0.
+                ((SSLSocket)socket).setEnabledProtocols(new String[] {"TLSv1.2"});
+            }
+            return socket;
+        }
+    }
 }