From 1b726018d3b9ad18b492811e82b93dfcc5152017 Mon Sep 17 00:00:00 2001
From: Vineet Garg <grg.vineet@gmail.com>
Date: Thu, 25 Jun 2015 04:20:03 +0530
Subject: [PATCH] Fixed bugs pointed out by Albert on CR

---
 build.gradle                                  |   2 -
 res/layout/activity_pair.xml                  |  33 -----
 res/values/strings.xml                        |   3 +-
 .../kdeconnect/Backends/BaseLinkProvider.java |   1 +
 .../Backends/BasePairingHandler.java          |  35 +++++
 .../Backends/LanBackend/LanLink.java          |   1 +
 .../Backends/LanBackend/LanLinkProvider.java  | 121 +++++++++++-------
 .../LanBackend/LanPairingHandler.java         |  90 +++++++++++++
 .../LoopbackBackend/LoopbackLinkProvider.java |   1 +
 .../LoopbackPairingHandler.java               |  27 ++++
 src/org/kde/kdeconnect/BackgroundService.java |   7 +-
 src/org/kde/kdeconnect/Device.java            |  80 +++++++-----
 .../Helpers/SecurityHelpers/SslHelper.java    |  18 +++
 src/org/kde/kdeconnect/NetworkPackage.java    |  19 +--
 .../UserInterface/PairActivity.java           |  71 +++++-----
 15 files changed, 336 insertions(+), 173 deletions(-)
 create mode 100644 src/org/kde/kdeconnect/Backends/BasePairingHandler.java
 create mode 100644 src/org/kde/kdeconnect/Backends/LanBackend/LanPairingHandler.java
 create mode 100644 src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackPairingHandler.java

diff --git a/build.gradle b/build.gradle
index e8dfd050..b0214fe6 100644
--- a/build.gradle
+++ b/build.gradle
@@ -54,9 +54,7 @@ dependencies {
     compile 'org.apache.sshd:sshd-core:0.8.0'
     compile 'io.netty:netty-all:4.0.23.Final'
     compile 'org.bouncycastle:bcpkix-jdk15on:1.52'
-
     androidTestCompile 'org.mockito:mockito-core:1.10.19'
-
     // Because mockito has some problems with dex environment
     androidTestCompile 'com.google.dexmaker:dexmaker:1.1'
     androidTestCompile 'com.google.dexmaker:dexmaker-mockito:1.1'
diff --git a/res/layout/activity_pair.xml b/res/layout/activity_pair.xml
index 30db79f6..6b73edc3 100644
--- a/res/layout/activity_pair.xml
+++ b/res/layout/activity_pair.xml
@@ -25,39 +25,6 @@
         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"
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 1efe28df..704bae50 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -61,9 +61,10 @@
     <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="encryption_info_title">Encryption Info</string>
+    <string name="encryption_info_msg_no_ssl">The other device doesn\'t use a recent version of KDE Connect, using the legacy encryption method.</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>
diff --git a/src/org/kde/kdeconnect/Backends/BaseLinkProvider.java b/src/org/kde/kdeconnect/Backends/BaseLinkProvider.java
index cfaf621d..5de4fc9a 100644
--- a/src/org/kde/kdeconnect/Backends/BaseLinkProvider.java
+++ b/src/org/kde/kdeconnect/Backends/BaseLinkProvider.java
@@ -30,6 +30,7 @@ import java.util.ArrayList;
 public abstract class BaseLinkProvider {
 
     private final ArrayList<ConnectionReceiver> connectionReceivers = new ArrayList<ConnectionReceiver>();
+    public BasePairingHandler pairingHandler;
 
     public interface ConnectionReceiver {
         public void onConnectionReceived(NetworkPackage identityPackage, BaseLink link);
diff --git a/src/org/kde/kdeconnect/Backends/BasePairingHandler.java b/src/org/kde/kdeconnect/Backends/BasePairingHandler.java
new file mode 100644
index 00000000..dfa989b3
--- /dev/null
+++ b/src/org/kde/kdeconnect/Backends/BasePairingHandler.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2015 Vineet Garg <grg.vineet@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License or (at your option) version 3 or any later version
+ * accepted by the membership of KDE e.V. (or its successor approved
+ * by the membership of KDE e.V.), which shall act as a proxy
+ * defined in Section 14 of version 3 of the license.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package org.kde.kdeconnect.Backends;
+
+import org.kde.kdeconnect.Device;
+import org.kde.kdeconnect.NetworkPackage;
+
+public abstract class BasePairingHandler {
+
+    public void packageReceived(Device device, NetworkPackage np) throws Exception{}
+    public void requestPairing(Device device, NetworkPackage np) {}
+    public void accept_pairing(Device device, NetworkPackage np) {}
+    public void rejectPairing(Device device, NetworkPackage np) {}
+    public void pairingDone(Device device) {}
+    public void unpair(Device device, NetworkPackage np) {}
+
+}
diff --git a/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java b/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java
index 44e956ac..ddc4edf1 100644
--- a/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java
+++ b/src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java
@@ -45,6 +45,7 @@ import javax.net.ssl.SSLServerSocketFactory;
 
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelFutureListener;
 
 public class LanLink extends BaseLink {
 
diff --git a/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java b/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java
index 4ac83040..30c4fb7e 100644
--- a/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java
+++ b/src/org/kde/kdeconnect/Backends/LanBackend/LanLinkProvider.java
@@ -27,15 +27,16 @@ import android.util.Base64;
 import android.util.Log;
 
 import org.kde.kdeconnect.Backends.BaseLinkProvider;
+import org.kde.kdeconnect.BackgroundService;
 import org.kde.kdeconnect.Device;
 import org.kde.kdeconnect.Helpers.SecurityHelpers.SslHelper;
 import org.kde.kdeconnect.NetworkPackage;
 import org.kde.kdeconnect.UserInterface.CustomDevicesActivity;
-import org.kde.kdeconnect.UserInterface.MainSettingsActivity;
 
 import java.net.DatagramSocket;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
+import java.net.SocketException;
 import java.security.cert.Certificate;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -47,6 +48,7 @@ import io.netty.bootstrap.ServerBootstrap;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
+import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
@@ -55,6 +57,8 @@ import io.netty.channel.EventLoopGroup;
 import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.DatagramPacket;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.channel.socket.SocketChannelConfig;
 import io.netty.channel.socket.nio.NioDatagramChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
@@ -80,17 +84,22 @@ public class LanLinkProvider extends BaseLinkProvider {
     private final LongSparseArray<Channel> nioChannels = new LongSparseArray<Channel>();
 
     private EventLoopGroup bossGroup, workerGroup, udpGroup, clientGroup;
+    private TcpHandler tcpHandler = new TcpHandler();
+    private UdpHandler udpHandler = new UdpHandler();
 
-    private class TcpHandler extends SimpleChannelInboundHandler{
+    @ChannelHandler.Sharable
+    private class TcpHandler extends SimpleChannelInboundHandler<String>{
         @Override
         public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
             cause.printStackTrace();
-            // If certificate changed, getting SocketException, connection reset by peer
-            // Ssl engines closes by itself, so do channel and link is removed
+            // Close channel for any sudden exception
+            ctx.fireChannelInactive();
         }
 
         @Override
         public void channelInactive(ChannelHandlerContext ctx) throws Exception {
+            // Not called if remote device closes session unexpectedly, like wifi off
+            Log.e("KDE/LanLinkProvider", "Channel inactive");
             try {
                 long id = ctx.channel().hashCode();
                 final LanLink brokenLink = nioLinks.get(id);
@@ -117,7 +126,7 @@ public class LanLinkProvider extends BaseLinkProvider {
                         public void run() {
                             //Wait a bit before emitting connectionLost, in case the same device re-appears
                             try {
-                                Thread.sleep(200);
+                                Thread.sleep(500);
                             } catch (InterruptedException e) {
                             }
                             connectionLost(brokenLink);
@@ -132,19 +141,17 @@ public class LanLinkProvider extends BaseLinkProvider {
             }
         }
 
-
         @Override
-        public void channelRead0(ChannelHandlerContext ctx, Object message) throws Exception {
+        public void channelRead0(ChannelHandlerContext ctx, String message) throws Exception {
 //            Log.e("LanLinkProvider","Incoming package, address: " + ctx.channel().remoteAddress());
 //            Log.e("LanLinkProvider","Received:"+message);
 
-            String theMessage = (String) message;
-            if (theMessage.isEmpty()) {
-                Log.e("KDE/LanLinkProvider","Empty package received");
+            if (message.isEmpty()) {
+                Log.e("KDE/LanLinkProvider", "Empty package received");
                 return;
             }
 
-            final NetworkPackage np = NetworkPackage.unserialize(theMessage);
+            final NetworkPackage np = NetworkPackage.unserialize(message);
 
             if (np.getType().equals(NetworkPackage.PACKAGE_TYPE_IDENTITY)) {
 
@@ -159,9 +166,9 @@ public class LanLinkProvider extends BaseLinkProvider {
                 nioLinks.put(ctx.channel().hashCode(), link);
                 //Log.i("KDE/LanLinkProvider","nioLinks.size(): " + nioLinks.size());
 
-                // Check if ssl supported on other device and enabled on my device, and add ssl handler
+                // Add ssl handler if device uses new protocol
                 try {
-                    if (myIdentityPackage.getBoolean("sslSupported") && np.getBoolean("sslSupported", false)) {
+                    if (NetworkPackage.ProtocolVersion <= np.getInt("protocolVersion")) {
                         Log.e("KDE/LanLinkProvider", "Remote device " + np.getString("deviceName") + " supports ssl");
                         final SSLEngine sslEngine = SslHelper.getSslEngine(context, np.getString("deviceId"), SslHelper.SslMode.Client);
                         SslHandler sslHandler = new SslHandler(sslEngine);
@@ -174,8 +181,22 @@ public class LanLinkProvider extends BaseLinkProvider {
                                     Certificate certificate = sslEngine.getSession().getPeerCertificates()[0];
                                     np.set("certificate", Base64.encodeToString(certificate.getEncoded(), 0));
                                     link.setOnSsl(true);
+                                    addLink(np, link);
+                                    Log.i("KDE/LanLinkProvider","Session with " + np.getString("deviceName") + " secured with " + sslEngine.getSession().getCipherSuite());
+                                } else {
+                                    // Unpair if handshake failed
+                                    Log.e("KDE/LanLinkProvider", "Handshake failed with " + np.getString("deviceName"));
+                                    future.cause().printStackTrace();
+                                    BackgroundService.RunCommand(context, new BackgroundService.InstanceCallback() {
+                                        @Override
+                                        public void onServiceStart(BackgroundService service) {
+                                            Device device = service.getDevice(np.getString("deviceId"));
+                                            if (device == null) return;
+                                            device.unpair();
+                                        }
+                                    });
                                 }
-                                addLink(np, link);
+
                             }
                         });
                     } else {
@@ -183,7 +204,6 @@ public class LanLinkProvider extends BaseLinkProvider {
                     }
                 } catch (Exception e) {
                     e.printStackTrace();
-                    addLink(np, link); // If exception getting ssl engine
                 }
 
             } else {
@@ -198,6 +218,7 @@ public class LanLinkProvider extends BaseLinkProvider {
         }
     }
 
+    @ChannelHandler.Sharable
     private class UdpHandler extends SimpleChannelInboundHandler<DatagramPacket> {
 
         @Override
@@ -223,16 +244,7 @@ public class LanLinkProvider extends BaseLinkProvider {
                     Bootstrap b = new Bootstrap();
                     b.group(clientGroup);
                     b.channel(NioSocketChannel.class);
-                    b.handler(new ChannelInitializer<Channel>() {
-                        @Override
-                        protected void initChannel(Channel ch) throws Exception {
-                            ChannelPipeline pipeline = ch.pipeline();
-                            pipeline.addLast(new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
-                            pipeline.addLast(new StringDecoder());
-                            pipeline.addLast(new StringEncoder());
-                            pipeline.addLast(new TcpHandler());
-                        }
-                    });
+                    b.handler(new TcpInitializer());
                     int tcpPort = identityPackage.getInt("tcpPort", port);
                     final ChannelFuture channelFuture = b.connect(packet.sender().getAddress(), tcpPort).sync();
                     channelFuture.addListener(new ChannelFutureListener() {
@@ -242,14 +254,13 @@ public class LanLinkProvider extends BaseLinkProvider {
 
                             Log.i("KDE/LanLinkProvider", "Connection successful: " + channel.isActive());
 
-                            // If I and remote device supports ssl, add ssl handler to channel
-                            if (PreferenceManager.getDefaultSharedPreferences(context).getBoolean(MainSettingsActivity.KEY_USE_SSL_PREFERENCE, true)
-                                && identityPackage.getBoolean("sslSupported", false)) {
+                            // Add ssl handler if device supports new protocol
+                            if (NetworkPackage.ProtocolVersion <= identityPackage.getInt("protocolVersion")) {
                                 // add ssl handler with start tls true
                                 SSLEngine sslEngine = SslHelper.getSslEngine(context, identityPackage.getString("deviceId"), SslHelper.SslMode.Server);
                                 SslHandler sslHandler = new SslHandler(sslEngine, true);
                                 channel.pipeline().addFirst(sslHandler);
-                                Log.e("KDE/LanLinkProvider", "Remote device supports ssl, ssl handler added");
+                                Log.i("KDE/LanLinkProvider", "Remote device supports ssl, ssl handler added");
                             }
 
                             final LanLink link = new LanLink(context, channel, identityPackage.getString("deviceId"), LanLinkProvider.this);
@@ -277,11 +288,25 @@ public class LanLinkProvider extends BaseLinkProvider {
                                                                 Certificate certificate = sslHandler.engine().getSession().getPeerCertificates()[0];
                                                                 identityPackage.set("certificate", Base64.encodeToString(certificate.getEncoded(), 0));
                                                                 link.setOnSsl(true);
+                                                                addLink(identityPackage, link);
                                                             } catch (Exception e){
                                                                 e.printStackTrace();
                                                             }
+                                                        } else {
+                                                            // Unpair if handshake failed
+                                                            // Any exception or handshake exception ?
+                                                            Log.e("KDE/LanLinkProvider", "Handshake failed with " + identityPackage.getString("deviceName"));
+                                                            future.cause().printStackTrace();
+                                                            BackgroundService.RunCommand(context, new BackgroundService.InstanceCallback() {
+                                                                @Override
+                                                                public void onServiceStart(BackgroundService service) {
+                                                                    Device device = service.getDevice(identityPackage.getString("deviceId"));
+                                                                    if (device == null) return;
+                                                                    device.unpair();
+                                                                }
+                                                            });
                                                         }
-                                                        addLink(identityPackage, link);
+
                                                     }
                                                 });
                                             } else {
@@ -312,6 +337,19 @@ public class LanLinkProvider extends BaseLinkProvider {
 
     }
 
+    public class TcpInitializer extends ChannelInitializer<SocketChannel> {
+        @Override
+        protected void initChannel(SocketChannel ch) throws Exception {
+            ChannelPipeline pipeline = ch.pipeline();
+            ch.config().setAllowHalfClosure(false); // Not sure how it will work, but we certainly don't want half closure
+            ch.config().setKeepAlive(true);
+            pipeline.addLast(new DelimiterBasedFrameDecoder(512 * 1024, Delimiters.lineDelimiter()));
+            pipeline.addLast(new StringDecoder());
+            pipeline.addLast(new StringEncoder());
+            pipeline.addLast(tcpHandler);
+        }
+    }
+
     private void addLink(NetworkPackage identityPackage, LanLink link) {
         String deviceId = identityPackage.getString("deviceId");
         Log.i("KDE/LanLinkProvider","addLink to "+deviceId);
@@ -341,18 +379,8 @@ public class LanLinkProvider extends BaseLinkProvider {
             tcpBootstrap.channel(NioServerSocketChannel.class);
             tcpBootstrap.option(ChannelOption.SO_BACKLOG, 100);
             tcpBootstrap.handler(new LoggingHandler(LogLevel.INFO));
-            tcpBootstrap.childOption(ChannelOption.SO_KEEPALIVE, true);
-            tcpBootstrap.childOption(ChannelOption.SO_REUSEADDR, true);
-            tcpBootstrap.childHandler(new ChannelInitializer<Channel>() {
-                @Override
-                protected void initChannel(Channel ch) throws Exception {
-                    ChannelPipeline pipeline = ch.pipeline();
-                    pipeline.addLast(new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
-                    pipeline.addLast(new StringDecoder());
-                    pipeline.addLast(new StringEncoder());
-                    pipeline.addLast(new TcpHandler());
-                }
-            });
+            tcpBootstrap.option(ChannelOption.SO_REUSEADDR, true);
+            tcpBootstrap.childHandler(new TcpInitializer());
             tcpBootstrap.bind(new InetSocketAddress(port)).sync();
         }catch (Exception e) {
             e.printStackTrace();
@@ -368,10 +396,10 @@ public class LanLinkProvider extends BaseLinkProvider {
                 @Override
                 protected void initChannel(Channel ch) throws Exception {
                     ChannelPipeline pipeline = ch.pipeline();
-                    pipeline.addLast(new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
+                    pipeline.addLast(new DelimiterBasedFrameDecoder(512 * 1024, Delimiters.lineDelimiter()));
                     pipeline.addLast(new StringDecoder());
                     pipeline.addLast(new StringEncoder());
-                    pipeline.addLast(new UdpHandler());
+                    pipeline.addLast(udpHandler);
                 }
             });
             udpBootstrap.bind(new InetSocketAddress(port)).sync();
@@ -381,6 +409,8 @@ public class LanLinkProvider extends BaseLinkProvider {
 
         clientGroup = new NioEventLoopGroup();
 
+        pairingHandler = new LanPairingHandler();
+
     }
 
     @Override
@@ -388,6 +418,7 @@ public class LanLinkProvider extends BaseLinkProvider {
 
         Log.e("KDE/LanLinkProvider", "onStart");
 
+
         new Thread(new Runnable() {
             @Override
             public void run() {
@@ -437,7 +468,7 @@ public class LanLinkProvider extends BaseLinkProvider {
 
     @Override
     public void onNetworkChange() {
-        Log.e("KDE/LanLinkProvider","onNetworkChange");
+        Log.e("KDE/LanLinkProvider", "onNetworkChange");
 
         //FilesHelper.LogOpenFileCount();
 
diff --git a/src/org/kde/kdeconnect/Backends/LanBackend/LanPairingHandler.java b/src/org/kde/kdeconnect/Backends/LanBackend/LanPairingHandler.java
new file mode 100644
index 00000000..3def7da8
--- /dev/null
+++ b/src/org/kde/kdeconnect/Backends/LanBackend/LanPairingHandler.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright 2015 Vineet Garg <grg.vineet@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License or (at your option) version 3 or any later version
+ * accepted by the membership of KDE e.V. (or its successor approved
+ * by the membership of KDE e.V.), which shall act as a proxy
+ * defined in Section 14 of version 3 of the license.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package org.kde.kdeconnect.Backends.LanBackend;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.preference.PreferenceManager;
+import android.util.Base64;
+import android.util.Log;
+
+import org.kde.kdeconnect.Backends.BasePairingHandler;
+import org.kde.kdeconnect.Device;
+import org.kde.kdeconnect.NetworkPackage;
+import org.kde.kdeconnect_tp.R;
+
+import java.security.KeyFactory;
+import java.security.cert.CertificateEncodingException;
+import java.security.spec.X509EncodedKeySpec;
+
+public class LanPairingHandler extends BasePairingHandler{
+
+    @Override
+    public void packageReceived(Device device, NetworkPackage np) throws Exception{
+        try {
+            String publicKeyContent = np.getString("publicKey").replace("-----BEGIN PUBLIC KEY-----\n","").replace("-----END PUBLIC KEY-----\n", "");
+            byte[] publicKeyBytes = Base64.decode(publicKeyContent, 0);
+            device.publicKey = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(publicKeyBytes));
+        } catch(Exception e) {
+            e.printStackTrace();
+            Log.e("KDE/Device","Pairing exception: Received incorrect key");
+            throw e;
+        }
+    }
+
+    @Override
+    public void requestPairing(Device device, NetworkPackage np) {
+        SharedPreferences globalSettings = PreferenceManager.getDefaultSharedPreferences(device.getContext());
+        String publicKey = "-----BEGIN PUBLIC KEY-----\n" + globalSettings.getString("publicKey", "").trim()+ "\n-----END PUBLIC KEY-----\n";
+        np.set("publicKey", publicKey);
+    }
+
+    @Override
+    public void accept_pairing(Device device, NetworkPackage np) {
+        SharedPreferences globalSettings = PreferenceManager.getDefaultSharedPreferences(device.getContext());
+        String publicKey = "-----BEGIN PUBLIC KEY-----\n" + globalSettings.getString("publicKey", "").trim()+ "\n-----END PUBLIC KEY-----\n";
+        np.set("publicKey", publicKey);
+    }
+
+    @Override
+    public void pairingDone(Device device) {
+        //Store device information needed to create a Device object in a future
+        SharedPreferences.Editor editor = device.getContext().getSharedPreferences(device.getDeviceId(), Context.MODE_PRIVATE).edit();
+
+        editor.putString("deviceName", device.getName());
+        editor.putString("deviceType", device.getDeviceType().toString());
+        String encodedPublicKey = Base64.encodeToString(device.publicKey.getEncoded(), 0);
+        editor.putString("publicKey", encodedPublicKey);
+        try {
+            String encodedCertificate = Base64.encodeToString(device.certificate.getEncoded(), 0);
+            editor.putString("certificate", encodedCertificate);
+        } catch (NullPointerException n) {
+            Log.e("KDE/PairingDone", "Certificate is null, remote device does not support ssl");
+        } catch (CertificateEncodingException c) {
+            Log.e("KDE/PairingDOne", "Error encoding certificate");
+        } catch (Exception e) {
+            e.printStackTrace();
+            Log.e("KDE/Pairng", "Some exception while encoding string");
+        }
+        editor.apply();
+
+    }
+}
diff --git a/src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackLinkProvider.java b/src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackLinkProvider.java
index c25ae39d..8c06eea2 100644
--- a/src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackLinkProvider.java
+++ b/src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackLinkProvider.java
@@ -31,6 +31,7 @@ public class LoopbackLinkProvider extends BaseLinkProvider {
 
     public LoopbackLinkProvider(Context context) {
         this.context = context;
+        pairingHandler = new LoopbackPairingHandler();
     }
 
     @Override
diff --git a/src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackPairingHandler.java b/src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackPairingHandler.java
new file mode 100644
index 00000000..1abf6f5e
--- /dev/null
+++ b/src/org/kde/kdeconnect/Backends/LoopbackBackend/LoopbackPairingHandler.java
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2015 Vineet Garg <grg.vineet@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License or (at your option) version 3 or any later version
+ * accepted by the membership of KDE e.V. (or its successor approved
+ * by the membership of KDE e.V.), which shall act as a proxy
+ * defined in Section 14 of version 3 of the license.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package org.kde.kdeconnect.Backends.LoopbackBackend;
+
+import org.kde.kdeconnect.Backends.LanBackend.LanPairingHandler;
+
+public class LoopbackPairingHandler extends LanPairingHandler{
+    // Extending from LanPairingHandler, as it is similar to it
+}
diff --git a/src/org/kde/kdeconnect/BackgroundService.java b/src/org/kde/kdeconnect/BackgroundService.java
index 6396617a..75afa8cc 100644
--- a/src/org/kde/kdeconnect/BackgroundService.java
+++ b/src/org/kde/kdeconnect/BackgroundService.java
@@ -28,7 +28,6 @@ import android.content.SharedPreferences;
 import android.os.Binder;
 import android.os.IBinder;
 import android.preference.PreferenceManager;
-import android.util.Base64;
 import android.util.Log;
 
 import org.kde.kdeconnect.Backends.BaseLink;
@@ -38,8 +37,6 @@ import org.kde.kdeconnect.Helpers.SecurityHelpers.RsaHelper;
 import org.kde.kdeconnect.Helpers.SecurityHelpers.SslHelper;
 import org.kde.kdeconnect.UserInterface.MainSettingsActivity;
 
-import java.security.KeyPair;
-import java.security.KeyPairGenerator;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Set;
@@ -99,6 +96,10 @@ public class BackgroundService extends Service {
 
     }
 
+    public ArrayList<BaseLinkProvider> getLinkProviders() {
+        return linkProviders;
+    }
+
     public Device getDevice(String id) {
         return devices.get(id);
     }
diff --git a/src/org/kde/kdeconnect/Device.java b/src/org/kde/kdeconnect/Device.java
index 7424f117..4992ddd6 100644
--- a/src/org/kde/kdeconnect/Device.java
+++ b/src/org/kde/kdeconnect/Device.java
@@ -39,6 +39,7 @@ import org.bouncycastle.cert.X509CertificateHolder;
 import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
 import org.bouncycastle.jce.provider.BouncyCastleProvider;
 import org.kde.kdeconnect.Backends.BaseLink;
+import org.kde.kdeconnect.Backends.BaseLinkProvider;
 import org.kde.kdeconnect.Plugins.Plugin;
 import org.kde.kdeconnect.Plugins.PluginFactory;
 import org.kde.kdeconnect.UserInterface.PairActivity;
@@ -175,6 +176,10 @@ public class Device implements BaseLink.PackageReceiver {
         return deviceId;
     }
 
+    public Context getContext() {
+        return context;
+    }
+
     //Returns 0 if the version matches, < 0 if it is older or > 0 if it is newer
     public int compareProtocolVersion() {
         return protocolVersion - NetworkPackage.ProtocolVersion;
@@ -236,9 +241,14 @@ public class Device implements BaseLink.PackageReceiver {
             return;
         }
 
-        //Send our own public key
-        NetworkPackage np = NetworkPackage.createPublicKeyPackage(context);
-        sendPackage(np, new SendPackageStatusCallback(){
+        // Each link can set whatever they want in pair package
+        NetworkPackage pairPackage = new NetworkPackage(NetworkPackage.PACKAGE_TYPE_PAIR);
+        for (BaseLinkProvider linkProvider : ((BackgroundService)context).getLinkProviders()) {
+            linkProvider.pairingHandler.requestPairing(this, pairPackage);
+        }
+        pairPackage.set("pair", true);
+
+        sendPackage(pairPackage, new SendPackageStatusCallback() {
             @Override
             public void onSuccess() {
                 if (pairingTimer != null) pairingTimer.cancel();
@@ -281,7 +291,13 @@ public class Device implements BaseLink.PackageReceiver {
         SharedPreferences preferences = context.getSharedPreferences("trusted_devices", Context.MODE_PRIVATE);
         preferences.edit().remove(deviceId).apply();
 
+        SharedPreferences devicePreferences = context.getSharedPreferences(deviceId, Context.MODE_PRIVATE);
+        devicePreferences.edit().clear().apply();
+
         NetworkPackage np = new NetworkPackage(NetworkPackage.PACKAGE_TYPE_PAIR);
+        for (BaseLinkProvider linkProvider : ((BackgroundService)context).getLinkProviders()) {
+            linkProvider.pairingHandler.unpair(this, np);
+        }
         np.set("pair", false);
         sendPackage(np);
 
@@ -303,20 +319,8 @@ public class Device implements BaseLink.PackageReceiver {
         SharedPreferences preferences = context.getSharedPreferences("trusted_devices", Context.MODE_PRIVATE);
         preferences.edit().putBoolean(deviceId,true).apply();
 
-        //Store device information needed to create a Device object in a future
-        SharedPreferences.Editor editor = settings.edit();
-        try {
-            editor.putString("deviceName", getName());
-            editor.putString("deviceType", deviceType.toString());
-            String encodedPublicKey = Base64.encodeToString(publicKey.getEncoded(), 0);
-            editor.putString("publicKey", encodedPublicKey);
-            String encodedCertificate = Base64.encodeToString(certificate.getEncoded(), 0);
-            editor.putString("certificate", encodedCertificate);
-        } catch (Exception e){
-            Log.e("KDE/Device", "Exception pairing done");
-            e.printStackTrace();
-        } finally {
-            editor.apply();
+        for (BaseLinkProvider linkProvider : ((BackgroundService)context).getLinkProviders()) {
+            linkProvider.pairingHandler.pairingDone(this);
         }
 
         reloadPluginsFromSettings();
@@ -329,10 +333,16 @@ public class Device implements BaseLink.PackageReceiver {
 
     public void acceptPairing() {
 
-        Log.i("KDE/Device","Accepted pair request started by the other device");
+        Log.i("KDE/Device", "Accepted pair request started by the other device");
+
+        final NetworkPackage np = new NetworkPackage(NetworkPackage.PACKAGE_TYPE_PAIR);
+        for (BaseLinkProvider linkProvider : ((BackgroundService)context).getLinkProviders()) {
+            linkProvider.pairingHandler.accept_pairing(this, np);
+        }
+        np.set("pair", true);
 
         //Send our own public key
-        NetworkPackage np = NetworkPackage.createPublicKeyPackage(context);
+//        NetworkPackage np = NetworkPackage.createPublicKeyPackage(context);
         sendPackage(np, new SendPackageStatusCallback() {
             @Override
             protected void onSuccess() {
@@ -358,6 +368,9 @@ public class Device implements BaseLink.PackageReceiver {
         pairStatus = PairStatus.NotPaired;
 
         NetworkPackage np = new NetworkPackage(NetworkPackage.PACKAGE_TYPE_PAIR);
+        for (BaseLinkProvider linkProvider : ((BackgroundService)context).getLinkProviders()) {
+            linkProvider.pairingHandler.rejectPairing(this, np);
+        }
         np.set("pair", false);
         sendPackage(np);
 
@@ -445,7 +458,7 @@ public class Device implements BaseLink.PackageReceiver {
 
         link.removePackageReceiver(this);
         links.remove(link);
-        Log.i("KDE/Device","removeLink: "+link.getLinkProvider().getName() + " -> "+getName() + " active links: "+ links.size());
+        Log.i("KDE/Device", "removeLink: " + link.getLinkProvider().getName() + " -> " + getName() + " active links: " + links.size());
         if (links.isEmpty()) {
             reloadPluginsFromSettings();
         }
@@ -456,7 +469,7 @@ public class Device implements BaseLink.PackageReceiver {
 
         if (np.getType().equals(NetworkPackage.PACKAGE_TYPE_PAIR)) {
 
-            Log.i("KDE/Device","Pair package");
+            Log.i("KDE/Device", "Pair package");
 
             boolean wantsPair = np.getBoolean("pair");
 
@@ -468,24 +481,27 @@ public class Device implements BaseLink.PackageReceiver {
                     for (PairingCallback cb : pairingCallback) {
                         cb.pairingFailed(context.getString(R.string.error_canceled_by_other_peer));
                     }
+                    return;
+                } if (pairStatus == PairStatus.Paired) {
+                    // Simple unpair without sending pair package
+                    pairStatus = PairStatus.NotPaired;
+                    for (PairingCallback cb : pairingCallback) cb.unpaired();
+                    reloadPluginsFromSettings();
                 }
-                return;
             }
 
             if (wantsPair) {
 
                 //Retrieve their public key
-                try {
-                    String publicKeyContent = np.getString("publicKey").replace("-----BEGIN PUBLIC KEY-----\n","").replace("-----END PUBLIC KEY-----\n", "");
-                    byte[] publicKeyBytes = Base64.decode(publicKeyContent, 0);
-                    publicKey = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(publicKeyBytes));
-                } catch(Exception e) {
-                    e.printStackTrace();
-                    Log.e("KDE/Device","Pairing exception: Received incorrect key");
-                    for (PairingCallback cb : pairingCallback) {
-                        cb.pairingFailed(context.getString(R.string.error_invalid_key));
+                for (BaseLinkProvider linkProvider : ((BackgroundService)context).getLinkProviders()) {
+                    try {
+                        linkProvider.pairingHandler.packageReceived(this, np);
+                    } catch (Exception e) {
+                        for (Device.PairingCallback cb : pairingCallback) {
+                            cb.pairingFailed(context.getString(R.string.error_invalid_key));
+                        }
+                        return;
                     }
-                    return;
                 }
 
                 if (pairStatus == PairStatus.Requested)  { //We started pairing
diff --git a/src/org/kde/kdeconnect/Helpers/SecurityHelpers/SslHelper.java b/src/org/kde/kdeconnect/Helpers/SecurityHelpers/SslHelper.java
index f972fbb3..6304e1a3 100644
--- a/src/org/kde/kdeconnect/Helpers/SecurityHelpers/SslHelper.java
+++ b/src/org/kde/kdeconnect/Helpers/SecurityHelpers/SslHelper.java
@@ -38,11 +38,13 @@ import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
 
 import java.math.BigInteger;
 import java.security.KeyStore;
+import java.security.MessageDigest;
 import java.security.PrivateKey;
 import java.security.PublicKey;
 import java.security.SecureRandom;
 import java.security.cert.X509Certificate;
 import java.util.Date;
+import java.util.Formatter;
 
 import javax.net.ssl.KeyManagerFactory;
 import javax.net.ssl.SSLContext;
@@ -209,4 +211,20 @@ public class SslHelper {
         }
         return null;
     }
+
+    public static String getCertificateHash(X509Certificate certificate) {
+        try {
+            byte[] hash = MessageDigest.getInstance("SHA-1").digest(certificate.getEncoded());
+            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().toUpperCase();
+        } catch (Exception e) {
+            return null;
+        }
+
+    }
+
 }
diff --git a/src/org/kde/kdeconnect/NetworkPackage.java b/src/org/kde/kdeconnect/NetworkPackage.java
index b290ff52..14cdf660 100644
--- a/src/org/kde/kdeconnect/NetworkPackage.java
+++ b/src/org/kde/kdeconnect/NetworkPackage.java
@@ -22,6 +22,7 @@ package org.kde.kdeconnect;
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.os.Build;
 import android.preference.PreferenceManager;
 import android.provider.Settings;
 import android.util.Base64;
@@ -45,7 +46,7 @@ import javax.crypto.Cipher;
 
 public class NetworkPackage {
 
-    public final static int ProtocolVersion = 5;
+    public final static int ProtocolVersion = 6;
 
     //TODO: Move these to their respective plugins
     public final static String PACKAGE_TYPE_IDENTITY = "kdeconnect.identity";
@@ -206,7 +207,6 @@ public class NetworkPackage {
                             DeviceHelper.getDeviceName()));
             np.mBody.put("protocolVersion", NetworkPackage.ProtocolVersion);
             np.mBody.put("deviceType", DeviceHelper.isTablet()? "tablet" : "phone");
-            np.mBody.put("sslSupported", PreferenceManager.getDefaultSharedPreferences(context).getBoolean(MainSettingsActivity.KEY_USE_SSL_PREFERENCE, true));
         } catch (Exception e) {
             e.printStackTrace();
             Log.e("NetworkPacakge","Exception on createIdentityPackage");
@@ -216,21 +216,6 @@ public class NetworkPackage {
 
     }
 
-
-    static public NetworkPackage createPublicKeyPackage(Context context) {
-
-        NetworkPackage np = new NetworkPackage(NetworkPackage.PACKAGE_TYPE_PAIR);
-
-        np.set("pair", true);
-
-        SharedPreferences globalSettings = PreferenceManager.getDefaultSharedPreferences(context);
-        String publicKey = "-----BEGIN PUBLIC KEY-----\n" + globalSettings.getString("publicKey", "").trim()+ "\n-----END PUBLIC KEY-----\n";
-        np.set("publicKey", publicKey);
-
-        return np;
-
-    }
-
     public void setPayload(byte[] data) {
         setPayload(new ByteArrayInputStream(data), data.length);
     }
diff --git a/src/org/kde/kdeconnect/UserInterface/PairActivity.java b/src/org/kde/kdeconnect/UserInterface/PairActivity.java
index 3aba436f..ad40dd23 100644
--- a/src/org/kde/kdeconnect/UserInterface/PairActivity.java
+++ b/src/org/kde/kdeconnect/UserInterface/PairActivity.java
@@ -20,12 +20,15 @@
 
 package org.kde.kdeconnect.UserInterface;
 
+import android.app.AlertDialog;
 import android.app.NotificationManager;
 import android.content.Context;
+import android.content.DialogInterface;
 import android.os.Bundle;
 import android.support.v7.app.ActionBar;
 import android.support.v7.app.ActionBarActivity;
-import android.util.Log;
+import android.view.Menu;
+import android.view.MenuItem;
 import android.view.View;
 import android.widget.Button;
 import android.widget.TextView;
@@ -35,9 +38,6 @@ 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;
@@ -53,7 +53,6 @@ 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);
                 }
             });
@@ -73,7 +72,6 @@ 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);
                 }
@@ -111,32 +109,6 @@ 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
@@ -206,13 +178,32 @@ 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();
-    }
+    @Override
+    public boolean onPrepareOptionsMenu(Menu menu) {
+        super.onPrepareOptionsMenu(menu);
+        menu.clear();
+        menu.add(R.string.encryption_info_title).setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
+            @Override
+            public boolean onMenuItemClick(MenuItem menuItem) {
+                Context context = PairActivity.this;
+                AlertDialog.Builder builder = new AlertDialog.Builder(context);
+                builder.setTitle(context.getResources().getString(R.string.encryption_info_title));
+                builder.setPositiveButton(context.getResources().getString(R.string.ok), new DialogInterface.OnClickListener() {
+                    public void onClick(DialogInterface dialog, int id) {
+                        dialog.dismiss();
+                    }
+                });
 
+                if (device.certificate == null) {
+                    builder.setMessage(R.string.encryption_info_msg_no_ssl);
+                } else {
+                    builder.setMessage(context.getResources().getString(R.string.my_device_key) + " " + SslHelper.getCertificateHash(device.certificate) + "\n"
+                            + context.getResources().getString(R.string.remote_device_key) + " " + SslHelper.getCertificateHash(SslHelper.certificate));
+                }
+                builder.create().show();
+                return true;
+            }
+        });
+        return true;
+    }
 }