/*
* Copyright (C) 2010 The Android Open Source Project
*
* 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.example.android.apis.view;
import com.example.android.apis.R;
import android.app.Activity;
import android.app.AlertDialog;
import android.os.Bundle;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.Toast;
/**
* This activity demonstrates two different ways in which views can be made more secure to
* touch spoofing attacks by leveraging framework features.
*
* The activity presents 3 buttons that obtensibly perform a risky security critical
* function. Under ordinary circumstances, the user would never click on these buttons
* or would at least think long and hard about it. However, a carefully crafted toast can
* overlay the contents of the activity in such a way as to make the user believe the buttons
* are innocuous. Since the toast cannot receive input, the touches are passed down to the
* activity potentially yielding an effect other than what the user intended.
*
* To simulate the spoofing risk, this activity pops up a specially crafted overlay as
* a toast layed out so as to cover the buttons and part of the descriptive text.
* For the purposes of this demonstration, pretend that the overlay was actually popped
* up by a malicious application published by the International Cabal of Evil Penguins.
*
* The 3 buttons are set up as follows:
*
* 1. The "unsecured button" does not apply any touch filtering of any kind.
* When the toast appears, this button remains clickable as usual which creates an
* opportunity for spoofing to occur.
*
* 2. The "built-in secured button" leverages the android:filterTouchesWhenObscured view
* attribute to ask the framework to filter out touches when the window is obscured.
* When the toast appears, the button does not receive the touch and appears to be inoperable.
*
* 3. The "custom secured button" adds a touch listener to the button which intercepts the
* touch event and checks whether the window is obscured. If so, it warns the user and
* drops the touch event. This example is intended to demonstrate how a view can
* perform its own filtering and provide additional feedback by examining the {@MotionEvent}
* flags to determine whether the window is obscured. Here we use a touch listener but
* a custom view subclass could perform the filtering by overriding
* {@link View#onFilterTouchEventForSecurity(MotionEvent)}.
*
* Refer to the comments on {@View} for more information about view security.
*/
public class SecureView extends Activity {
private int mClickCount;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.secure_view);
Button toastButton = (Button) findViewById(R.id.secure_view_toast_button);
toastButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
showOverlay();
}
});
Button unsecureButton = (Button) findViewById(R.id.secure_view_unsecure_button);
setClickedAction(unsecureButton);
Button builtinSecureButton = (Button) findViewById(R.id.secure_view_builtin_secure_button);
setClickedAction(builtinSecureButton);
Button customSecureButton = (Button) findViewById(R.id.secure_view_custom_secure_button);
setClickedAction(customSecureButton);
setTouchFilter(customSecureButton);
}
private void showOverlay() {
// Generate a toast view with a special layout that will position itself right
// on top of this view's interesting widgets. Sneaky huh?
SecureViewOverlay overlay = (SecureViewOverlay)
getLayoutInflater().inflate(R.layout.secure_view_overlay, null);
overlay.setActivityToSpoof(this);
Toast toast = new Toast(getApplicationContext());
toast.setGravity(Gravity.FILL, 0, 0);
toast.setView(overlay);
toast.show();
}
private void setClickedAction(Button button) {
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
String[] messages = getResources().getStringArray(R.array.secure_view_clicked);
String message = messages[mClickCount++ % messages.length];
new AlertDialog.Builder(SecureView.this)
.setTitle(R.string.secure_view_action_dialog_title)
.setMessage(message)
.setNeutralButton(getResources().getString(
R.string.secure_view_action_dialog_dismiss), null)
.show();
}
});
}
private void setTouchFilter(Button button) {
button.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
if ((event.getFlags() & MotionEvent.FLAG_WINDOW_IS_OBSCURED) != 0) {
if (event.getAction() == MotionEvent.ACTION_UP) {
new AlertDialog.Builder(SecureView.this)
.setTitle(R.string.secure_view_caught_dialog_title)
.setMessage(R.string.secure_view_caught_dialog_message)
.setNeutralButton(getResources().getString(
R.string.secure_view_caught_dialog_dismiss), null)
.show();
}
// Return true to prevent the button from processing the touch.
return true;
}
return false;
}
});
}
}