selfbraille/SelfBrailleClient.java - external/eyes-free - Git at Google

 /*
  * Copyright (C) 2012 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  * License for the specific language governing permissions and limitations under
  * the License.
  */

 package com.googlecode.eyesfree.braille.selfbraille;

 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.Signature;
 import android.os.Binder;
 import android.os.Handler;
 import android.os.IBinder;
 import android.os.Message;
 import android.os.RemoteException;
 import android.util.Log;

 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;

 /**
  * Client-side interface to the self brailling interface.
  *
  * Threading: Instances of this object should be created and shut down
  * in a thread with a {@link Looper} associated with it.  Other methods may
  * be called on any thread.
  */
 public class SelfBrailleClient {
     private static final String LOG_TAG =
             SelfBrailleClient.class.getSimpleName();
     private static final String ACTION_SELF_BRAILLE_SERVICE =
             "com.googlecode.eyesfree.braille.service.ACTION_SELF_BRAILLE_SERVICE";
     private static final String BRAILLE_BACK_PACKAGE =
             "com.googlecode.eyesfree.brailleback";
     private static final Intent mServiceIntent =
             new Intent(ACTION_SELF_BRAILLE_SERVICE)
             .setPackage(BRAILLE_BACK_PACKAGE);
     /**
      * SHA-1 hash value of the Eyes-Free release key certificate, used to sign
      * BrailleBack.  It was generated from the keystore with:
      * $ keytool -exportcert -keystore <keystorefile> -alias android.keystore \
      *   > cert
      * $ keytool -printcert -file cert
      */
     // The typecasts are to silence a compiler warning about loss of precision
     private static final byte[] EYES_FREE_CERT_SHA1 = new byte[] {
         (byte) 0x9B, (byte) 0x42, (byte) 0x4C, (byte) 0x2D,
         (byte) 0x27, (byte) 0xAD, (byte) 0x51, (byte) 0xA4,
         (byte) 0x2A, (byte) 0x33, (byte) 0x7E, (byte) 0x0B,
         (byte) 0xB6, (byte) 0x99, (byte) 0x1C, (byte) 0x76,
         (byte) 0xEC, (byte) 0xA4, (byte) 0x44, (byte) 0x61
     };
     /**
      * Delay before the first rebind attempt on bind error or service
      * disconnect.
      */
     private static final int REBIND_DELAY_MILLIS = 500;
     private static final int MAX_REBIND_ATTEMPTS = 5;

     private final Binder mIdentity = new Binder();
     private final Context mContext;
     private final boolean mAllowDebugService;
     private final SelfBrailleHandler mHandler = new SelfBrailleHandler();
     private boolean mShutdown = false;

     /**
      * Written in handler thread, read in any thread calling methods on the
      * object.
      */
     private volatile Connection mConnection;
     /** Protected by synchronizing on mHandler. */
     private int mNumFailedBinds = 0;

     /**
      * Constructs an instance of this class.  {@code context} is used to bind
      * to the self braille service.  The current thread must have a Looper
      * associated with it.  If {@code allowDebugService} is true, this instance
      * will connect to a BrailleBack service without requiring it to be signed
      * by the release key used to sign BrailleBack.
      */
     public SelfBrailleClient(Context context, boolean allowDebugService) {
         mContext = context;
         mAllowDebugService = allowDebugService;
         doBindService();
     }

     /**
      * Shuts this instance down, deallocating any global resources it is using.
      * This method must be called on the same thread that created this object.
      */
     public void shutdown() {
         mShutdown = true;
         doUnbindService();
     }

     public void write(WriteData writeData) {
         writeData.validate();
         ISelfBrailleService localService = getSelfBrailleService();
         if (localService != null) {
             try {
                 localService.write(mIdentity, writeData);
             } catch (RemoteException ex) {
                 Log.e(LOG_TAG, "Self braille write failed", ex);
             }
         }
     }

     private void doBindService() {
         Connection localConnection = new Connection();
         if (!mContext.bindService(mServiceIntent, localConnection,
                 Context.BIND_AUTO_CREATE)) {
             Log.e(LOG_TAG, "Failed to bind to service");
             mHandler.scheduleRebind();
             return;
         }
         mConnection = localConnection;
         Log.i(LOG_TAG, "Bound to self braille service");
     }

     private void doUnbindService() {
         if (mConnection != null) {
             ISelfBrailleService localService = getSelfBrailleService();
             if (localService != null) {
                 try {
                     localService.disconnect(mIdentity);
                 } catch (RemoteException ex) {
                     // Nothing to do.
                 }
             }
             mContext.unbindService(mConnection);
             mConnection = null;
         }
     }

     private ISelfBrailleService getSelfBrailleService() {
         Connection localConnection = mConnection;
         if (localConnection != null) {
             return localConnection.mService;
         }
         return null;
     }

     private boolean verifyPackage() {
         PackageManager pm = mContext.getPackageManager();
         PackageInfo pi;
         try {
             pi = pm.getPackageInfo(BRAILLE_BACK_PACKAGE,
                     PackageManager.GET_SIGNATURES);
         } catch (PackageManager.NameNotFoundException ex) {
             Log.w(LOG_TAG, "Can't verify package " + BRAILLE_BACK_PACKAGE,
                     ex);
             return false;
         }
         MessageDigest digest;
         try {
             digest = MessageDigest.getInstance("SHA-1");
         } catch (NoSuchAlgorithmException ex) {
             Log.e(LOG_TAG, "SHA-1 not supported", ex);
             return false;
         }
         // Check if any of the certificates match our hash.
         for (Signature signature : pi.signatures) {
             digest.update(signature.toByteArray());
             if (MessageDigest.isEqual(EYES_FREE_CERT_SHA1, digest.digest())) {
                 return true;
             }
             digest.reset();
         }
         if (mAllowDebugService) {
             Log.w(LOG_TAG, String.format(
                 "*** %s connected to BrailleBack with invalid (debug?) "
                 + "signature ***",
                 mContext.getPackageName()));
             return true;
         }
         return false;
     }
     private class Connection implements ServiceConnection {
         // Read in application threads, written in main thread.
         private volatile ISelfBrailleService mService;

         @Override
         public void onServiceConnected(ComponentName className,
                 IBinder binder) {
             if (!verifyPackage()) {
                 Log.w(LOG_TAG, String.format("Service certificate mismatch "
                                 + "for %s, dropping connection",
                                 BRAILLE_BACK_PACKAGE));
                 mHandler.unbindService();
                 return;
             }
             Log.i(LOG_TAG, "Connected to self braille service");
             mService = ISelfBrailleService.Stub.asInterface(binder);
             synchronized (mHandler) {
                 mNumFailedBinds = 0;
             }
         }

         @Override
         public void onServiceDisconnected(ComponentName className) {
             Log.e(LOG_TAG, "Disconnected from self braille service");
             mService = null;
             // Retry by rebinding.
             mHandler.scheduleRebind();
         }
     }

     private class SelfBrailleHandler extends Handler {
         private static final int MSG_REBIND_SERVICE = 1;
         private static final int MSG_UNBIND_SERVICE = 2;

         public void scheduleRebind() {
             synchronized (this) {
                 if (mNumFailedBinds < MAX_REBIND_ATTEMPTS) {
                     int delay = REBIND_DELAY_MILLIS << mNumFailedBinds;
                     sendEmptyMessageDelayed(MSG_REBIND_SERVICE, delay);
                     ++mNumFailedBinds;
                 }
             }
         }

         public void unbindService() {
             sendEmptyMessage(MSG_UNBIND_SERVICE);
         }

         @Override
         public void handleMessage(Message msg) {
             switch (msg.what) {
                 case MSG_REBIND_SERVICE:
                     handleRebindService();
                     break;
                 case MSG_UNBIND_SERVICE:
                     handleUnbindService();
                     break;
             }
         }

         private void handleRebindService() {
             if (mShutdown) {
                 return;
             }
             if (mConnection != null) {
                 doUnbindService();
             }
             doBindService();
         }

         private void handleUnbindService() {
             doUnbindService();
         }
     }
 }
	/*
	* Copyright (C) 2012 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may not
	* use this file except in compliance with the License. You may obtain a copy of
	* the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	* License for the specific language governing permissions and limitations under
	* the License.
	*/

	package com.googlecode.eyesfree.braille.selfbraille;

	import android.content.ComponentName;
	import android.content.Context;
	import android.content.Intent;
	import android.content.ServiceConnection;
	import android.content.pm.PackageInfo;
	import android.content.pm.PackageManager;
	import android.content.pm.Signature;
	import android.os.Binder;
	import android.os.Handler;
	import android.os.IBinder;
	import android.os.Message;
	import android.os.RemoteException;
	import android.util.Log;

	import java.security.MessageDigest;
	import java.security.NoSuchAlgorithmException;

	/**
	* Client-side interface to the self brailling interface.
	*
	* Threading: Instances of this object should be created and shut down
	* in a thread with a {@link Looper} associated with it. Other methods may
	* be called on any thread.
	*/
	public class SelfBrailleClient {
	private static final String LOG_TAG =
	SelfBrailleClient.class.getSimpleName();
	private static final String ACTION_SELF_BRAILLE_SERVICE =
	"com.googlecode.eyesfree.braille.service.ACTION_SELF_BRAILLE_SERVICE";
	private static final String BRAILLE_BACK_PACKAGE =
	"com.googlecode.eyesfree.brailleback";
	private static final Intent mServiceIntent =
	new Intent(ACTION_SELF_BRAILLE_SERVICE)
	.setPackage(BRAILLE_BACK_PACKAGE);
	/**
	* SHA-1 hash value of the Eyes-Free release key certificate, used to sign
	* BrailleBack. It was generated from the keystore with:
	* $ keytool -exportcert -keystore <keystorefile> -alias android.keystore \
	* > cert
	* $ keytool -printcert -file cert
	*/
	// The typecasts are to silence a compiler warning about loss of precision
	private static final byte[] EYES_FREE_CERT_SHA1 = new byte[] {
	(byte) 0x9B, (byte) 0x42, (byte) 0x4C, (byte) 0x2D,
	(byte) 0x27, (byte) 0xAD, (byte) 0x51, (byte) 0xA4,
	(byte) 0x2A, (byte) 0x33, (byte) 0x7E, (byte) 0x0B,
	(byte) 0xB6, (byte) 0x99, (byte) 0x1C, (byte) 0x76,
	(byte) 0xEC, (byte) 0xA4, (byte) 0x44, (byte) 0x61
	};
	/**
	* Delay before the first rebind attempt on bind error or service
	* disconnect.
	*/
	private static final int REBIND_DELAY_MILLIS = 500;
	private static final int MAX_REBIND_ATTEMPTS = 5;

	private final Binder mIdentity = new Binder();
	private final Context mContext;
	private final boolean mAllowDebugService;
	private final SelfBrailleHandler mHandler = new SelfBrailleHandler();
	private boolean mShutdown = false;

	/**
	* Written in handler thread, read in any thread calling methods on the
	* object.
	*/
	private volatile Connection mConnection;
	/** Protected by synchronizing on mHandler. */
	private int mNumFailedBinds = 0;

	/**
	* Constructs an instance of this class. {@code context} is used to bind
	* to the self braille service. The current thread must have a Looper
	* associated with it. If {@code allowDebugService} is true, this instance
	* will connect to a BrailleBack service without requiring it to be signed
	* by the release key used to sign BrailleBack.
	*/
	public SelfBrailleClient(Context context, boolean allowDebugService) {
	mContext = context;
	mAllowDebugService = allowDebugService;
	doBindService();
	}

	/**
	* Shuts this instance down, deallocating any global resources it is using.
	* This method must be called on the same thread that created this object.
	*/
	public void shutdown() {
	mShutdown = true;
	doUnbindService();
	}

	public void write(WriteData writeData) {
	writeData.validate();
	ISelfBrailleService localService = getSelfBrailleService();
	if (localService != null) {
	try {
	localService.write(mIdentity, writeData);
	} catch (RemoteException ex) {
	Log.e(LOG_TAG, "Self braille write failed", ex);
	}
	}
	}

	private void doBindService() {
	Connection localConnection = new Connection();
	if (!mContext.bindService(mServiceIntent, localConnection,
	Context.BIND_AUTO_CREATE)) {
	Log.e(LOG_TAG, "Failed to bind to service");
	mHandler.scheduleRebind();
	return;
	}
	mConnection = localConnection;
	Log.i(LOG_TAG, "Bound to self braille service");
	}

	private void doUnbindService() {
	if (mConnection != null) {
	ISelfBrailleService localService = getSelfBrailleService();
	if (localService != null) {
	try {
	localService.disconnect(mIdentity);
	} catch (RemoteException ex) {
	// Nothing to do.
	}
	}
	mContext.unbindService(mConnection);
	mConnection = null;
	}
	}

	private ISelfBrailleService getSelfBrailleService() {
	Connection localConnection = mConnection;
	if (localConnection != null) {
	return localConnection.mService;
	}
	return null;
	}

	private boolean verifyPackage() {
	PackageManager pm = mContext.getPackageManager();
	PackageInfo pi;
	try {
	pi = pm.getPackageInfo(BRAILLE_BACK_PACKAGE,
	PackageManager.GET_SIGNATURES);
	} catch (PackageManager.NameNotFoundException ex) {
	Log.w(LOG_TAG, "Can't verify package " + BRAILLE_BACK_PACKAGE,
	ex);
	return false;
	}
	MessageDigest digest;
	try {
	digest = MessageDigest.getInstance("SHA-1");
	} catch (NoSuchAlgorithmException ex) {
	Log.e(LOG_TAG, "SHA-1 not supported", ex);
	return false;
	}
	// Check if any of the certificates match our hash.
	for (Signature signature : pi.signatures) {
	digest.update(signature.toByteArray());
	if (MessageDigest.isEqual(EYES_FREE_CERT_SHA1, digest.digest())) {
	return true;
	}
	digest.reset();
	}
	if (mAllowDebugService) {
	Log.w(LOG_TAG, String.format(
	"*** %s connected to BrailleBack with invalid (debug?) "
	+ "signature ***",
	mContext.getPackageName()));
	return true;
	}
	return false;
	}
	private class Connection implements ServiceConnection {
	// Read in application threads, written in main thread.
	private volatile ISelfBrailleService mService;

	@Override
	public void onServiceConnected(ComponentName className,
	IBinder binder) {
	if (!verifyPackage()) {
	Log.w(LOG_TAG, String.format("Service certificate mismatch "
	+ "for %s, dropping connection",
	BRAILLE_BACK_PACKAGE));
	mHandler.unbindService();
	return;
	}
	Log.i(LOG_TAG, "Connected to self braille service");
	mService = ISelfBrailleService.Stub.asInterface(binder);
	synchronized (mHandler) {
	mNumFailedBinds = 0;
	}
	}

	@Override
	public void onServiceDisconnected(ComponentName className) {
	Log.e(LOG_TAG, "Disconnected from self braille service");
	mService = null;
	// Retry by rebinding.
	mHandler.scheduleRebind();
	}
	}

	private class SelfBrailleHandler extends Handler {
	private static final int MSG_REBIND_SERVICE = 1;
	private static final int MSG_UNBIND_SERVICE = 2;

	public void scheduleRebind() {
	synchronized (this) {
	if (mNumFailedBinds < MAX_REBIND_ATTEMPTS) {
	int delay = REBIND_DELAY_MILLIS << mNumFailedBinds;
	sendEmptyMessageDelayed(MSG_REBIND_SERVICE, delay);
	++mNumFailedBinds;
	}
	}
	}

	public void unbindService() {
	sendEmptyMessage(MSG_UNBIND_SERVICE);
	}

	@Override
	public void handleMessage(Message msg) {
	switch (msg.what) {
	case MSG_REBIND_SERVICE:
	handleRebindService();
	break;
	case MSG_UNBIND_SERVICE:
	handleUnbindService();
	break;
	}
	}

	private void handleRebindService() {
	if (mShutdown) {
	return;
	}
	if (mConnection != null) {
	doUnbindService();
	}
	doBindService();
	}

	private void handleUnbindService() {
	doUnbindService();
	}
	}
	}