Enable TLS 1.2 (See Issue facebook#7192)

Credits to Alex Gotev (@gotev) for the nice implementation.

ReactAndroid/src/main/java/com/facebook/react/modules/network/OkHttpClientProvider.java

@@ -9,11 +9,19 @@
 
 package com.facebook.react.modules.network;
 
+import android.os.Build;
+import android.util.Log;
+
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.TimeUnit;
 
 import javax.annotation.Nullable;
+import javax.net.ssl.SSLContext;
 
+import okhttp3.ConnectionSpec;
 import okhttp3.OkHttpClient;
+import okhttp3.TlsVersion;
 
 /**
  * Helper class that provides the same OkHttpClient instance that will be used for all networking
@@ -39,11 +47,43 @@ public static void replaceOkHttpClient(OkHttpClient client) {
 
   private static OkHttpClient createClient() {
     // No timeouts by default
-    return new OkHttpClient.Builder()
+    OkHttpClient.Builder client = new OkHttpClient.Builder()
       .connectTimeout(0, TimeUnit.MILLISECONDS)
       .readTimeout(0, TimeUnit.MILLISECONDS)
       .writeTimeout(0, TimeUnit.MILLISECONDS)
-      .cookieJar(new ReactCookieJarContainer())
-      .build();
+      .cookieJar(new ReactCookieJarContainer());
+
+    return enableTls12OnPreLollipop(client).build();
   }
+
+  /*
+    On Android 4.1-4.4 (API level 16 to 19) TLS 1.1 and 1.2 are
+    available but not enabled by default. The following method
+    enables it.
+
+    See also https://github.com/facebook/react-native/issues/7192
+   */
+  public static OkHttpClient.Builder enableTls12OnPreLollipop(OkHttpClient.Builder client) {
+    if (Build.VERSION.SDK_INT >= 16 && Build.VERSION.SDK_INT < 20) {
+      try {
+        client.sslSocketFactory(new TLSSocketFactory());
+
+        ConnectionSpec cs = new ConnectionSpec.Builder(ConnectionSpec.MODERN_TLS)
+                .tlsVersions(TlsVersion.TLS_1_2)
+                .build();
+
+        List<ConnectionSpec> specs = new ArrayList<>();
+        specs.add(cs);
+        specs.add(ConnectionSpec.COMPATIBLE_TLS);
+        specs.add(ConnectionSpec.CLEARTEXT);
+
+        client.connectionSpecs(specs);
+      } catch (Exception exc) {
+        Log.e("OkHttpClientProvider", "Error while enabling TLS 1.2", exc);
+      }
+    }
+
+    return client;
+  }
+
 }

ReactAndroid/src/main/java/com/facebook/react/modules/network/TLSSocketFactory.java

@@ -0,0 +1,78 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+package com.facebook.react.modules.network;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.Socket;
+import java.net.UnknownHostException;
+import java.security.KeyManagementException;
+import java.security.NoSuchAlgorithmException;
+
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.SSLSocket;
+import javax.net.ssl.SSLSocketFactory;
+
+/**
+ *
+ * This class is needed for TLS 1.2 support on Android 4.x
+ *
+ * Source: http://blog.dev-area.net/2015/08/13/android-4-1-enable-tls-1-1-and-tls-1-2/
+ */
+public class TLSSocketFactory extends SSLSocketFactory {
+    private SSLSocketFactory internalSSLSocketFactory;
+
+    public TLSSocketFactory() throws KeyManagementException, NoSuchAlgorithmException {
+        SSLContext context = SSLContext.getInstance("TLS");
+        context.init(null, null, null);
+        internalSSLSocketFactory = context.getSocketFactory();
+    }
+
+    @Override
+    public String[] getDefaultCipherSuites() {
+        return internalSSLSocketFactory.getDefaultCipherSuites();
+    }
+
+    @Override
+    public String[] getSupportedCipherSuites() {
+        return internalSSLSocketFactory.getSupportedCipherSuites();
+    }
+
+    @Override
+    public Socket createSocket(Socket s, String host, int port, boolean autoClose) throws IOException {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(s, host, port, autoClose));
+    }
+
+    @Override
+    public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(host, port));
+    }
+
+    @Override
+    public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(host, port, localHost, localPort));
+    }
+
+    @Override
+    public Socket createSocket(InetAddress host, int port) throws IOException {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(host, port));
+    }
+
+    @Override
+    public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
+        return enableTLSOnSocket(internalSSLSocketFactory.createSocket(address, port, localAddress, localPort));
+    }
+
+    private Socket enableTLSOnSocket(Socket socket) {
+        if(socket != null && (socket instanceof SSLSocket)) {
+            ((SSLSocket)socket).setEnabledProtocols(new String[] {"TLSv1.1", "TLSv1.2"});
+        }
+        return socket;
+    }
+}