Jeff Brown | cf4db94 | 2010-09-03 10:19:28 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2010 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.example.android.apis.view; |
| 18 | |
| 19 | import com.example.android.apis.R; |
| 20 | |
| 21 | import android.app.Activity; |
| 22 | import android.app.AlertDialog; |
| 23 | import android.os.Bundle; |
| 24 | import android.view.Gravity; |
| 25 | import android.view.MotionEvent; |
| 26 | import android.view.View; |
| 27 | import android.view.View.OnClickListener; |
| 28 | import android.view.View.OnTouchListener; |
| 29 | import android.widget.Button; |
| 30 | import android.widget.Toast; |
| 31 | |
| 32 | |
| 33 | /** |
| 34 | * This activity demonstrates two different ways in which views can be made more secure to |
| 35 | * touch spoofing attacks by leveraging framework features. |
| 36 | * |
| 37 | * The activity presents 3 buttons that obtensibly perform a risky security critical |
| 38 | * function. Under ordinary circumstances, the user would never click on these buttons |
| 39 | * or would at least think long and hard about it. However, a carefully crafted toast can |
| 40 | * overlay the contents of the activity in such a way as to make the user believe the buttons |
| 41 | * are innocuous. Since the toast cannot receive input, the touches are passed down to the |
| 42 | * activity potentially yielding an effect other than what the user intended. |
| 43 | * |
| 44 | * To simulate the spoofing risk, this activity pops up a specially crafted overlay as |
| 45 | * a toast layed out so as to cover the buttons and part of the descriptive text. |
| 46 | * For the purposes of this demonstration, pretend that the overlay was actually popped |
| 47 | * up by a malicious application published by the International Cabal of Evil Penguins. |
| 48 | * |
| 49 | * The 3 buttons are set up as follows: |
| 50 | * |
| 51 | * 1. The "unsecured button" does not apply any touch filtering of any kind. |
| 52 | * When the toast appears, this button remains clickable as usual which creates an |
| 53 | * opportunity for spoofing to occur. |
| 54 | * |
| 55 | * 2. The "built-in secured button" leverages the android:filterTouchesWhenObscured view |
| 56 | * attribute to ask the framework to filter out touches when the window is obscured. |
| 57 | * When the toast appears, the button does not receive the touch and appears to be inoperable. |
| 58 | * |
| 59 | * 3. The "custom secured button" adds a touch listener to the button which intercepts the |
| 60 | * touch event and checks whether the window is obscured. If so, it warns the user and |
| 61 | * drops the touch event. This example is intended to demonstrate how a view can |
| 62 | * perform its own filtering and provide additional feedback by examining the {@MotionEvent} |
| 63 | * flags to determine whether the window is obscured. Here we use a touch listener but |
| 64 | * a custom view subclass could perform the filtering by overriding |
| 65 | * {@link View#onFilterTouchEventForSecurity(MotionEvent)}. |
| 66 | * |
| 67 | * Refer to the comments on {@View} for more information about view security. |
| 68 | */ |
| 69 | public class SecureView extends Activity { |
| 70 | private int mClickCount; |
| 71 | |
| 72 | @Override |
| 73 | protected void onCreate(Bundle savedInstanceState) { |
| 74 | super.onCreate(savedInstanceState); |
| 75 | |
| 76 | setContentView(R.layout.secure_view); |
| 77 | |
| 78 | Button toastButton = (Button) findViewById(R.id.secure_view_toast_button); |
| 79 | toastButton.setOnClickListener(new OnClickListener() { |
| 80 | public void onClick(View v) { |
| 81 | showOverlay(); |
| 82 | } |
| 83 | }); |
| 84 | |
| 85 | Button unsecureButton = (Button) findViewById(R.id.secure_view_unsecure_button); |
| 86 | setClickedAction(unsecureButton); |
| 87 | |
| 88 | Button builtinSecureButton = (Button) findViewById(R.id.secure_view_builtin_secure_button); |
| 89 | setClickedAction(builtinSecureButton); |
| 90 | |
| 91 | Button customSecureButton = (Button) findViewById(R.id.secure_view_custom_secure_button); |
| 92 | setClickedAction(customSecureButton); |
| 93 | setTouchFilter(customSecureButton); |
| 94 | } |
| 95 | |
| 96 | private void showOverlay() { |
| 97 | // Generate a toast view with a special layout that will position itself right |
| 98 | // on top of this view's interesting widgets. Sneaky huh? |
| 99 | SecureViewOverlay overlay = (SecureViewOverlay) |
| 100 | getLayoutInflater().inflate(R.layout.secure_view_overlay, null); |
| 101 | overlay.setActivityToSpoof(this); |
| 102 | |
| 103 | Toast toast = new Toast(getApplicationContext()); |
| 104 | toast.setGravity(Gravity.FILL, 0, 0); |
| 105 | toast.setView(overlay); |
| 106 | toast.show(); |
| 107 | } |
| 108 | |
| 109 | private void setClickedAction(Button button) { |
| 110 | button.setOnClickListener(new OnClickListener() { |
| 111 | public void onClick(View v) { |
| 112 | String[] messages = getResources().getStringArray(R.array.secure_view_clicked); |
| 113 | String message = messages[mClickCount++ % messages.length]; |
| 114 | |
| 115 | new AlertDialog.Builder(SecureView.this) |
| 116 | .setTitle(R.string.secure_view_action_dialog_title) |
| 117 | .setMessage(message) |
| 118 | .setNeutralButton(getResources().getString( |
| 119 | R.string.secure_view_action_dialog_dismiss), null) |
| 120 | .show(); |
| 121 | } |
| 122 | }); |
| 123 | } |
| 124 | |
| 125 | private void setTouchFilter(Button button) { |
| 126 | button.setOnTouchListener(new OnTouchListener() { |
| 127 | public boolean onTouch(View v, MotionEvent event) { |
| 128 | if ((event.getFlags() & MotionEvent.FLAG_WINDOW_IS_OBSCURED) != 0) { |
| 129 | if (event.getAction() == MotionEvent.ACTION_UP) { |
| 130 | new AlertDialog.Builder(SecureView.this) |
| 131 | .setTitle(R.string.secure_view_caught_dialog_title) |
| 132 | .setMessage(R.string.secure_view_caught_dialog_message) |
| 133 | .setNeutralButton(getResources().getString( |
| 134 | R.string.secure_view_caught_dialog_dismiss), null) |
| 135 | .show(); |
| 136 | } |
| 137 | // Return true to prevent the button from processing the touch. |
| 138 | return true; |
| 139 | } |
| 140 | return false; |
| 141 | } |
| 142 | }); |
| 143 | } |
| 144 | } |