Added support to verify keys during pair

res/layout/activity_pair.xml

@@ -25,6 +25,39 @@
         android:layout_gravity="left|center_vertical"
     />
 
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:visibility="gone"
+        android:id="@+id/secret_keys"
+        android:layout_gravity="center"
+        android:paddingTop="5dp"
+        android:paddingBottom="5dp">
+
+        <TextView
+            android:id="@+id/my_device_key"
+            android:layout_width="fill_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/pairing_accept"
+            android:layout_weight="1"
+            />
+
+        <TextView
+            android:id="@+id/remote_device_key"
+            android:layout_width="fill_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/pairing_reject"
+            android:layout_weight="1" />
+
+        <TextView
+            android:layout_width="fill_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/security_message"
+            android:layout_weight="1"/>
+
+    </LinearLayout>
+
     <Button
         android:id="@+id/pair_button"
         android:layout_width="match_parent"

res/values/strings.xml

@@ -61,6 +61,9 @@
     <string name="error_canceled_by_user">Canceled by user</string>
     <string name="error_canceled_by_other_peer">Canceled by other peer</string>
     <string name="error_invalid_key">Invalid key received</string>
+    <string name="my_device_key">My device key : </string>
+    <string name="remote_device_key">Remote device key : </string>
+    <string name="security_message">Be sure to match these keys before pairing for security purposes</string>
     <string name="pair_requested">Pair requested</string>
     <string name="pairing_request_from">Pairing request from %1s</string>
     <string name="received_url_title">Received link from %1s</string>

src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java

@@ -26,6 +26,7 @@ import org.json.JSONObject;
 import org.kde.kdeconnect.Backends.BaseLink;
 import org.kde.kdeconnect.Backends.BaseLinkProvider;
 import org.kde.kdeconnect.Device;
+import org.kde.kdeconnect.Helpers.SecurityHelpers.RsaHelper;
 import org.kde.kdeconnect.NetworkPackage;
 
 import java.io.IOException;
@@ -88,7 +89,7 @@ public class LanLink extends BaseLink {
 
             //Encrypt if key provided
             if (key != null) {
-                np = np.encrypt(key);
+                np = RsaHelper.encrypt(np, key);
             }
 
             //Send body of the network package
@@ -169,7 +170,7 @@ public class LanLink extends BaseLink {
         if (np.getType().equals(NetworkPackage.PACKAGE_TYPE_ENCRYPTED)) {
 
             try {
-                np = np.decrypt(privateKey);
+                np = RsaHelper.decrypt(np, privateKey);
             } catch(Exception e) {
                 e.printStackTrace();
                 Log.e("KDE/onPackageReceived","Exception reading the key needed to decrypt the package");

src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java

@@ -40,7 +40,6 @@ import java.util.ArrayList;
 import java.util.HashMap;
 
 import javax.net.ssl.SSLEngine;
-import javax.security.auth.login.LoginException;
 
 import io.netty.bootstrap.Bootstrap;
 import io.netty.bootstrap.ServerBootstrap;
@@ -48,13 +47,11 @@ import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandlerContext;
-import io.netty.channel.ChannelInboundHandlerAdapter;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.ChannelPipeline;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.SimpleChannelInboundHandler;
-import io.netty.channel.nio.NioEventLoop;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.DatagramPacket;
 import io.netty.channel.socket.nio.NioDatagramChannel;
@@ -86,8 +83,8 @@ public class LanLinkProvider extends BaseLinkProvider {
     private class TcpHandler extends SimpleChannelInboundHandler{
         @Override
         public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
-            super.exceptionCaught(ctx, cause);
             cause.printStackTrace();
+            // TODO : Add necessary action on ssl handshake failure
         }
 
         @Override
@@ -181,8 +178,8 @@ public class LanLinkProvider extends BaseLinkProvider {
                                 if (future.isSuccess()) {
                                     Certificate certificate = sslEngine.getSession().getPeerCertificates()[0];
                                     np.set("certificate", Base64.encodeToString(certificate.getEncoded(), 0));
+                                    link.setOnSsl(true);
                                 }
-                                link.setOnSsl(true);
                                 addLink(np, link);
                             }
                         });
@@ -191,7 +188,7 @@ public class LanLinkProvider extends BaseLinkProvider {
                     }
                 } catch (Exception e) {
                     e.printStackTrace();
-                    addLink(np, link);
+                    addLink(np, link); // If error in ssl engine, which is returning null in some cases
                 }
 
             } else {
@@ -285,11 +282,11 @@ public class LanLinkProvider extends BaseLinkProvider {
                                                             try {
                                                                 Certificate certificate = sslHandler.engine().getSession().getPeerCertificates()[0];
                                                                 identityPackage.set("certificate", Base64.encodeToString(certificate.getEncoded(), 0));
+                                                                link.setOnSsl(true);
                                                             } catch (Exception e){
                                                                 e.printStackTrace();
                                                             }
                                                         }
-                                                        link.setOnSsl(true);
                                                         addLink(identityPackage, link);
                                                     }
                                                 });
@@ -450,13 +447,6 @@ public class LanLinkProvider extends BaseLinkProvider {
 
         //FilesHelper.LogOpenFileCount();
 
-        //Keep existing connections open while unbinding the socket
-//        tcpAcceptor.setCloseOnDeactivation(false);
-//        onStop();
-//        tcpAcceptor.setCloseOnDeactivation(true);
-
-        //FilesHelper.LogOpenFileCount();
-
         onStart();
 
         //FilesHelper.LogOpenFileCount();

src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackLink.java

@@ -23,6 +23,7 @@ package org.kde.kdeconnect.Backends.LoopbackBackend;
 import org.kde.kdeconnect.Backends.BaseLink;
 import org.kde.kdeconnect.Backends.BaseLinkProvider;
 import org.kde.kdeconnect.Device;
+import org.kde.kdeconnect.Helpers.SecurityHelpers.RsaHelper;
 import org.kde.kdeconnect.NetworkPackage;
 
 import java.security.PublicKey;
@@ -42,12 +43,12 @@ public class LoopbackLink extends BaseLink {
     public void sendPackageEncrypted(NetworkPackage in, Device.SendPackageStatusCallback callback, PublicKey key) {
         try {
             if (key != null) {
-                in = in.encrypt(key);
+                in = RsaHelper.encrypt(in, key);
             }
             String s = in.serialize();
             NetworkPackage out= NetworkPackage.unserialize(s);
             if (key != null) {
-                out = out.decrypt(privateKey);
+                out = RsaHelper.decrypt(out, privateKey);
             }
             packageReceived(out);
             if (in.hasPayload()) {

src/org/kde/kdeconnect/Helpers/SecurityHelpers/SslHelper.java

@@ -62,6 +62,8 @@ public class SslHelper {
         Server
     }
 
+    public static X509Certificate certificate; //my device's certificate
+
     public static void initialiseCertificate(Context context){
         PrivateKey privateKey;
         PublicKey publicKey;
@@ -94,7 +96,7 @@ public class SslHelper {
                         publicKey
                 );
                 ContentSigner contentSigner = new JcaContentSignerBuilder("SHA256WithRSAEncryption").setProvider(BC).build(privateKey);
-                X509Certificate certificate = new JcaX509CertificateConverter().setProvider(BC).getCertificate(certificateBuilder.build(contentSigner));
+                certificate = new JcaX509CertificateConverter().setProvider(BC).getCertificate(certificateBuilder.build(contentSigner));
 
                 SharedPreferences.Editor edit = settings.edit();
                 edit.putString("certificate", Base64.encodeToString(certificate.getEncoded(), 0));
@@ -106,6 +108,16 @@ public class SslHelper {
                 return;
             }
 
+        } else {
+            try {
+                SharedPreferences globalSettings = PreferenceManager.getDefaultSharedPreferences(context);
+                byte[] certificateBytes = Base64.decode(globalSettings.getString("certificate", ""), 0);
+                X509CertificateHolder certificateHolder = new X509CertificateHolder(certificateBytes);
+                certificate = new JcaX509CertificateConverter().setProvider(new BouncyCastleProvider()).getCertificate(certificateHolder);
+            } catch (Exception e) {
+                Log.e("KDE/SslHelper", "Exception reading own certificate");
+                e.printStackTrace();
+            }
         }
     }
 
@@ -119,12 +131,6 @@ public class SslHelper {
             // Get device private key
             PrivateKey privateKey = RsaHelper.getPrivateKey(context);
 
-            // Get my certificate
-            SharedPreferences globalSettings = PreferenceManager.getDefaultSharedPreferences(context);
-            byte[] myCertificateBytes = Base64.decode(globalSettings.getString("certificate", ""), 0);
-            X509CertificateHolder myCertificateHolder = new X509CertificateHolder(myCertificateBytes);
-            X509Certificate myCertificate = new JcaX509CertificateConverter().setProvider(new BouncyCastleProvider()).getCertificate(myCertificateHolder);
-
             // Get remote device certificate if trusted
             java.security.cert.Certificate remoteDeviceCertificate = null;
             if (isDeviceTrusted){
@@ -137,7 +143,7 @@ public class SslHelper {
             // Setup keystore
             KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
             keyStore.load(null, null);
-            keyStore.setKeyEntry("key", privateKey, "".toCharArray(), new java.security.cert.Certificate[]{myCertificate});;
+            keyStore.setKeyEntry("key", privateKey, "".toCharArray(), new java.security.cert.Certificate[]{certificate});;
             // Set certificate if device trusted
             if (remoteDeviceCertificate != null){
                 keyStore.setCertificateEntry("remoteCertificate", remoteDeviceCertificate);

src/org/kde/kdeconnect/NetworkPackage.java

@@ -193,56 +193,6 @@ public class NetworkPackage {
         return np;
     }
 
-    public NetworkPackage encrypt(PublicKey publicKey) throws GeneralSecurityException {
-
-        String serialized = serialize();
-
-        int chunkSize = 128;
-
-        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING");
-        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
-
-        JSONArray chunks = new JSONArray();
-        while (serialized.length() > 0) {
-            if (serialized.length() < chunkSize) {
-                chunkSize = serialized.length();
-            }
-            String chunk = serialized.substring(0, chunkSize);
-            serialized = serialized.substring(chunkSize);
-            byte[] chunkBytes = chunk.getBytes(Charset.defaultCharset());
-            byte[] encryptedChunk;
-            encryptedChunk = cipher.doFinal(chunkBytes);
-            chunks.put(Base64.encodeToString(encryptedChunk, Base64.NO_WRAP));
-        }
-
-        //Log.i("NetworkPackage", "Encrypted " + chunks.length()+" chunks");
-
-        NetworkPackage encrypted = new NetworkPackage(NetworkPackage.PACKAGE_TYPE_ENCRYPTED);
-        encrypted.set("data", chunks);
-        encrypted.setPayload(mPayload, mPayloadSize);
-        return encrypted;
-
-    }
-
-    public NetworkPackage decrypt(PrivateKey privateKey)  throws GeneralSecurityException, JSONException {
-
-        JSONArray chunks = mBody.getJSONArray("data");
-
-        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING");
-        cipher.init(Cipher.DECRYPT_MODE, privateKey);
-
-        String decryptedJson = "";
-        for (int i = 0; i < chunks.length(); i++) {
-            byte[] encryptedChunk = Base64.decode(chunks.getString(i), Base64.NO_WRAP);
-            String decryptedChunk = new String(cipher.doFinal(encryptedChunk));
-            decryptedJson += decryptedChunk;
-        }
-
-        NetworkPackage decrypted = unserialize(decryptedJson);
-        decrypted.setPayload(mPayload, mPayloadSize);
-        return decrypted;
-    }
-
     static public NetworkPackage createIdentityPackage(Context context) {
 
         NetworkPackage np = new NetworkPackage(NetworkPackage.PACKAGE_TYPE_IDENTITY);

src/org/kde/kdeconnect/UserInterface/PairActivity.java

@@ -25,14 +25,21 @@ import android.content.Context;
 import android.os.Bundle;
 import android.support.v7.app.ActionBar;
 import android.support.v7.app.ActionBarActivity;
+import android.util.Base64;
+import android.util.Log;
 import android.view.View;
 import android.widget.Button;
+import android.widget.LinearLayout;
 import android.widget.TextView;
 
 import org.kde.kdeconnect.BackgroundService;
 import org.kde.kdeconnect.Device;
+import org.kde.kdeconnect.Helpers.SecurityHelpers.SslHelper;
 import org.kde.kdeconnect_tp.R;
 
+import java.security.MessageDigest;
+import java.util.Formatter;
+
 public class PairActivity extends ActionBarActivity {
 
     private String deviceId;
@@ -48,6 +55,7 @@ public class PairActivity extends ActionBarActivity {
                     ((TextView) findViewById(R.id.pair_message)).setText(R.string.pair_requested);
                     findViewById(R.id.pair_progress).setVisibility(View.GONE);
                     findViewById(R.id.pair_button).setVisibility(View.GONE);
+                    findViewById(R.id.secret_keys).setVisibility(View.VISIBLE);
                     findViewById(R.id.pair_request).setVisibility(View.VISIBLE);
                 }
             });
@@ -67,6 +75,7 @@ public class PairActivity extends ActionBarActivity {
                 public void run() {
                     ((TextView) findViewById(R.id.pair_message)).setText(error);
                     findViewById(R.id.pair_progress).setVisibility(View.GONE);
+                    findViewById(R.id.secret_keys).setVisibility(View.VISIBLE);
                     findViewById(R.id.pair_button).setVisibility(View.VISIBLE);
                     findViewById(R.id.pair_request).setVisibility(View.GONE);
                 }
@@ -104,12 +113,39 @@ public class PairActivity extends ActionBarActivity {
 
         });
 
+        // Show secret keys based on certificate if device are connected using ssl
+        BackgroundService.RunCommand(PairActivity.this, new BackgroundService.InstanceCallback() {
+            @Override
+            public void onServiceStart(BackgroundService service) {
+                device = service.getDevice(deviceId);
+                if (device == null) {
+                    Log.e("KDE/PairActivity", "Device is null");
+                    return;
+                }
+
+                if (device.certificate == null) {
+                    Log.e("KDE/PairActivity", "Device certificate is null");
+                    return;
+                }
+
+                try {
+                    ((TextView) findViewById(R.id.remote_device_key)).setText(getApplicationContext().getResources().getString(R.string.remote_device_key) + byteArray2Hex(MessageDigest.getInstance("SHA-1").digest(device.certificate.getEncoded())).toUpperCase());
+                    ((TextView) findViewById(R.id.my_device_key)).setText(getApplicationContext().getResources().getString(R.string.my_device_key) + byteArray2Hex(MessageDigest.getInstance("SHA-1").digest(SslHelper.certificate.getEncoded())).toUpperCase());
+                    findViewById(R.id.secret_keys).setVisibility(View.VISIBLE);
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+
+            }
+        });
+
         final Button pairButton = (Button)findViewById(R.id.pair_button);
         pairButton.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View view) {
                 pairButton.setVisibility(View.GONE);
                 ((TextView) findViewById(R.id.pair_message)).setText("");
+                findViewById(R.id.secret_keys).setVisibility(View.GONE);
                 findViewById(R.id.pair_progress).setVisibility(View.VISIBLE);
                 BackgroundService.RunCommand(PairActivity.this, new BackgroundService.InstanceCallback() {
                     @Override
@@ -173,4 +209,13 @@ public class PairActivity extends ActionBarActivity {
         super.onStop();
     }
 
+    private static String byteArray2Hex(final byte[] hash) {
+        Formatter formatter = new Formatter();
+        // Using first 4 bytes out of 20, is this secure ?
+        for (int i=0 ; i<4 ; i++) {
+            formatter.format("%02x", hash[i]);
+        }
+        return formatter.toString();
+    }
+
 }