Fix TLS 1.2 support for Android 4.4.x devices

Author: Gerardo Pacheco

android/src/main/java/com/RNFetchBlob/RNFetchBlobReq.java

@@ -13,6 +13,7 @@
 
 import com.RNFetchBlob.Response.RNFetchBlobDefaultResp;
 import com.RNFetchBlob.Response.RNFetchBlobFileResp;
+import com.RNFetchBlob.Utils.Tls12SocketFactory;
 import com.facebook.common.logging.FLog;
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.Callback;
@@ -722,32 +723,23 @@ public void onReceive(Context context, Intent intent) {
     public static OkHttpClient.Builder enableTls12OnPreLollipop(OkHttpClient.Builder client) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN && Build.VERSION.SDK_INT <= Build.VERSION_CODES.KITKAT) {
             try {
-                // Code from https://stackoverflow.com/a/40874952/544779
-                TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
-                trustManagerFactory.init((KeyStore) null);
-                TrustManager[] trustManagers = trustManagerFactory.getTrustManagers();
-                if (trustManagers.length != 1 || !(trustManagers[0] instanceof X509TrustManager)) {
-                    throw new IllegalStateException("Unexpected default trust managers:" + Arrays.toString(trustManagers));
-                }
-                X509TrustManager trustManager = (X509TrustManager) trustManagers[0];
-                SSLContext sslContext = SSLContext.getInstance("SSL");
-                sslContext.init(null, new TrustManager[] { trustManager }, null);
-                SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();
-
-                client.sslSocketFactory(sslSocketFactory, trustManager);
+                // Code from https://github.com/square/okhttp/issues/2372#issuecomment-244807676
+                SSLContext sc = SSLContext.getInstance("TLSv1.2");
+                sc.init(null, null, null);
+                client.sslSocketFactory(new Tls12SocketFactory(sc.getSocketFactory()));
 
                 ConnectionSpec cs = new ConnectionSpec.Builder(ConnectionSpec.MODERN_TLS)
                         .tlsVersions(TlsVersion.TLS_1_2)
                         .build();
 
-                List< ConnectionSpec > specs = new ArrayList < > ();
+                List<ConnectionSpec> specs = new ArrayList<>();
                 specs.add(cs);
                 specs.add(ConnectionSpec.COMPATIBLE_TLS);
                 specs.add(ConnectionSpec.CLEARTEXT);
 
                 client.connectionSpecs(specs);
             } catch (Exception exc) {
-                FLog.e("OkHttpClientProvider", "Error while enabling TLS 1.2", exc);
+                FLog.e("OkHttpTLSCompat", "Error while setting TLS 1.2", exc);
             }
         }
 

android/src/main/java/com/RNFetchBlob/Utils/Tls12SocketFactory.java

@@ -0,0 +1,69 @@
+package com.RNFetchBlob.Utils;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.Socket;
+import java.net.UnknownHostException;
+
+import javax.net.ssl.SSLSocket;
+import javax.net.ssl.SSLSocketFactory;
+
+/**
+ * Enables TLS v1.2 when creating SSLSockets.
+ * <p/>
+ * For some reason, android supports TLS v1.2 from API 16, but enables it by
+ * default only from API 20.
+ * @link https://developer.android.com/reference/javax/net/ssl/SSLSocket.html
+ * @see SSLSocketFactory
+ */
+public class Tls12SocketFactory extends SSLSocketFactory {
+    private static final String[] TLS_V12_ONLY = {"TLSv1.2"};
+
+    final SSLSocketFactory delegate;
+
+    public Tls12SocketFactory(SSLSocketFactory base) {
+        this.delegate = base;
+    }
+
+    @Override
+    public String[] getDefaultCipherSuites() {
+        return delegate.getDefaultCipherSuites();
+    }
+
+    @Override
+    public String[] getSupportedCipherSuites() {
+        return delegate.getSupportedCipherSuites();
+    }
+
+    @Override
+    public Socket createSocket(Socket s, String host, int port, boolean autoClose) throws IOException {
+        return patch(delegate.createSocket(s, host, port, autoClose));
+    }
+
+    @Override
+    public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
+        return patch(delegate.createSocket(host, port));
+    }
+
+    @Override
+    public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
+        return patch(delegate.createSocket(host, port, localHost, localPort));
+    }
+
+    @Override
+    public Socket createSocket(InetAddress host, int port) throws IOException {
+        return patch(delegate.createSocket(host, port));
+    }
+
+    @Override
+    public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
+        return patch(delegate.createSocket(address, port, localAddress, localPort));
+    }
+
+    private Socket patch(Socket s) {
+        if (s instanceof SSLSocket) {
+            ((SSLSocket) s).setEnabledProtocols(TLS_V12_ONLY);
+        }
+        return s;
+    }
+}