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1 /*
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2 * ConnectBot: simple, powerful, open-source SSH client for Android
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3 * Copyright 2007 Kenny Root, Jeffrey Sharkey
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4 *
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5 * Licensed under the Apache License, Version 2.0 (the "License");
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6 * you may not use this file except in compliance with the License.
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7 * You may obtain a copy of the License at
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8 *
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9 * http://www.apache.org/licenses/LICENSE-2.0
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10 *
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11 * Unless required by applicable law or agreed to in writing, software
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12 * distributed under the License is distributed on an "AS IS" BASIS,
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13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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14 * See the License for the specific language governing permissions and
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15 * limitations under the License.
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16 */
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17
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18 package com.five_ten_sg.connectbot.util;
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19
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20 import java.util.Vector;
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21
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22 import com.five_ten_sg.connectbot.R;
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23 import android.content.Context;
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24 import android.graphics.Canvas;
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25 import android.graphics.Color;
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26 import android.graphics.Paint;
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27 import android.graphics.Paint.FontMetrics;
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28 import android.graphics.Typeface;
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29 import android.util.AttributeSet;
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30 import android.view.MotionEvent;
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31 import android.view.View;
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32
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33 public class EntropyView extends View {
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34 private static final int SHA1_MAX_BYTES = 20;
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35 private static final int MILLIS_BETWEEN_INPUTS = 50;
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36
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37 private Paint mPaint;
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38 private FontMetrics mFontMetrics;
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39 private boolean mFlipFlop;
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40 private long mLastTime;
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41 private Vector<OnEntropyGatheredListener> listeners;
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42
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43 private byte[] mEntropy;
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44 private int mEntropyByteIndex;
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45 private int mEntropyBitIndex;
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46
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47 private int splitText = 0;
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48
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49 private float lastX = 0.0f, lastY = 0.0f;
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50
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51 public EntropyView(Context context) {
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52 super(context);
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53 setUpEntropy();
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54 }
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55
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56 public EntropyView(Context context, AttributeSet attrs) {
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57 super(context, attrs);
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58 setUpEntropy();
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59 }
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60
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61 private void setUpEntropy() {
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62 mPaint = new Paint();
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63 mPaint.setAntiAlias(true);
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64 mPaint.setTypeface(Typeface.DEFAULT);
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65 mPaint.setTextAlign(Paint.Align.CENTER);
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66 mPaint.setTextSize(16);
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67 mPaint.setColor(Color.WHITE);
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68 mFontMetrics = mPaint.getFontMetrics();
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69 mEntropy = new byte[SHA1_MAX_BYTES];
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70 mEntropyByteIndex = 0;
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71 mEntropyBitIndex = 0;
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72 listeners = new Vector<OnEntropyGatheredListener>();
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73 }
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74
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75 public void addOnEntropyGatheredListener(OnEntropyGatheredListener listener) {
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76 listeners.add(listener);
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77 }
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78
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79 public void removeOnEntropyGatheredListener(OnEntropyGatheredListener listener) {
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80 listeners.remove(listener);
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81 }
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82
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83 @Override
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84 public void onDraw(Canvas c) {
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85 String prompt = String.format(getResources().getString(R.string.pubkey_touch_prompt),
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86 (int)(100.0 * (mEntropyByteIndex / 20.0)) + (int)(5.0 * (mEntropyBitIndex / 8.0)));
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87
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88 if (splitText > 0 ||
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89 mPaint.measureText(prompt) > (getWidth() * 0.8)) {
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90 if (splitText == 0)
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91 splitText = prompt.indexOf(" ", prompt.length() / 2);
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92
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93 c.drawText(prompt.substring(0, splitText),
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94 getWidth() / 2.0f,
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95 getHeight() / 2.0f + (mPaint.ascent() + mPaint.descent()),
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96 mPaint);
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97 c.drawText(prompt.substring(splitText),
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98 getWidth() / 2.0f,
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99 getHeight() / 2.0f - (mPaint.ascent() + mPaint.descent()),
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100 mPaint);
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101 }
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102 else {
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103 c.drawText(prompt,
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104 getWidth() / 2.0f,
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105 getHeight() / 2.0f - (mFontMetrics.ascent + mFontMetrics.descent) / 2,
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106 mPaint);
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107 }
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108 }
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109
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110 @Override
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111 public boolean onTouchEvent(MotionEvent event) {
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112 if (mEntropyByteIndex >= SHA1_MAX_BYTES
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113 || lastX == event.getX()
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114 || lastY == event.getY())
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115 return true;
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116
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117 // Only get entropy every 200 milliseconds to ensure the user has moved around.
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118 long now = System.currentTimeMillis();
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119
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120 if ((now - mLastTime) < MILLIS_BETWEEN_INPUTS)
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121 return true;
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122 else
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123 mLastTime = now;
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124
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125 byte input;
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126 lastX = event.getX();
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127 lastY = event.getY();
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128
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129 // Get the lowest 4 bits of each X, Y input and concat to the entropy-gathering
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130 // string.
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131 if (mFlipFlop)
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132 input = (byte)((((int)lastX & 0x0F) << 4) | ((int)lastY & 0x0F));
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133 else
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134 input = (byte)((((int)lastY & 0x0F) << 4) | ((int)lastX & 0x0F));
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135
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136 mFlipFlop = !mFlipFlop;
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137
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138 for (int i = 0; i < 4 && mEntropyByteIndex < SHA1_MAX_BYTES; i++) {
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139 if ((input & 0x3) == 0x1) {
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140 mEntropy[mEntropyByteIndex] <<= 1;
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141 mEntropy[mEntropyByteIndex] |= 1;
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142 mEntropyBitIndex++;
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143 input >>= 2;
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144 }
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145 else if ((input & 0x3) == 0x2) {
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146 mEntropy[mEntropyByteIndex] <<= 1;
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147 mEntropyBitIndex++;
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148 input >>= 2;
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149 }
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150
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151 if (mEntropyBitIndex >= 8) {
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152 mEntropyBitIndex = 0;
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153 mEntropyByteIndex++;
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154 }
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155 }
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156
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157 // SHA1PRNG only keeps 160 bits of entropy.
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158 if (mEntropyByteIndex >= SHA1_MAX_BYTES) {
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159 for (OnEntropyGatheredListener listener : listeners) {
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160 listener.onEntropyGathered(mEntropy);
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161 }
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162 }
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163
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164 invalidate();
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165 return true;
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166 }
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167 }
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