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1 package com.trilead.ssh2.crypto;
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2
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3 import java.io.IOException;
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4
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5 import java.math.BigInteger;
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6
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7 /**
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8 * SimpleDERReader.
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9 *
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10 * @author Christian Plattner, plattner@trilead.com
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11 * @version $Id: SimpleDERReader.java,v 1.1 2007/10/15 12:49:56 cplattne Exp $
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12 */
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13 public class SimpleDERReader {
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14 private static final int CONSTRUCTED = 0x20;
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15
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16 byte[] buffer;
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17 int pos;
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18 int count;
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19
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20 public SimpleDERReader(byte[] b) {
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21 resetInput(b);
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22 }
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23
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24 public SimpleDERReader(byte[] b, int off, int len) {
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25 resetInput(b, off, len);
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26 }
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27
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28 public void resetInput(byte[] b) {
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29 resetInput(b, 0, b.length);
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30 }
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31
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32 public void resetInput(byte[] b, int off, int len) {
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33 buffer = b;
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34 pos = off;
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35 count = len;
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36 }
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37
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38 private byte readByte() throws IOException {
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39 if (count <= 0)
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40 throw new IOException("DER byte array: out of data");
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41
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42 count--;
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43 return buffer[pos++];
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44 }
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45
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46 private byte[] readBytes(int len) throws IOException {
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47 if (len > count)
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48 throw new IOException("DER byte array: out of data");
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49
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50 byte[] b = new byte[len];
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51 System.arraycopy(buffer, pos, b, 0, len);
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52 pos += len;
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53 count -= len;
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54 return b;
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55 }
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56
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57 public int available() {
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58 return count;
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59 }
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60
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61 private int readLength() throws IOException {
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62 int len = readByte() & 0xff;
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63
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64 if ((len & 0x80) == 0)
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65 return len;
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66
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67 int remain = len & 0x7F;
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68
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69 if (remain == 0)
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70 return -1;
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71
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72 len = 0;
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73
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74 while (remain > 0) {
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75 len = len << 8;
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76 len = len | (readByte() & 0xff);
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77 remain--;
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78 }
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79
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80 return len;
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81 }
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82
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83 public int ignoreNextObject() throws IOException {
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84 int type = readByte() & 0xff;
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85 int len = readLength();
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86
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87 if ((len < 0) || len > available())
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88 throw new IOException("Illegal len in DER object (" + len + ")");
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89
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90 readBytes(len);
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91 return type;
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92 }
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93
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94 public BigInteger readInt() throws IOException {
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95 int type = readByte() & 0xff;
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96
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97 if (type != 0x02)
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98 throw new IOException("Expected DER Integer, but found type " + type);
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99
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100 int len = readLength();
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101
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102 if ((len < 0) || len > available())
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103 throw new IOException("Illegal len in DER object (" + len + ")");
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104
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105 byte[] b = readBytes(len);
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106 BigInteger bi = new BigInteger(b);
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107 return bi;
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108 }
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109
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110 public int readConstructedType() throws IOException {
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111 int type = readByte() & 0xff;
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112
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113 if ((type & CONSTRUCTED) != CONSTRUCTED)
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114 throw new IOException("Expected constructed type, but was " + type);
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115
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116 return type & 0x1f;
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117 }
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118
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119 public SimpleDERReader readConstructed() throws IOException {
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120 int len = readLength();
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121
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122 if ((len < 0) || len > available())
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123 throw new IOException("Illegal len in DER object (" + len + ")");
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124
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125 SimpleDERReader cr = new SimpleDERReader(buffer, pos, len);
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126 pos += len;
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127 count -= len;
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128 return cr;
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129 }
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130
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131 public byte[] readSequenceAsByteArray() throws IOException {
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132 int type = readByte() & 0xff;
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133
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134 if (type != 0x30)
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135 throw new IOException("Expected DER Sequence, but found type " + type);
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136
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137 int len = readLength();
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138
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139 if ((len < 0) || len > available())
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140 throw new IOException("Illegal len in DER object (" + len + ")");
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141
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142 byte[] b = readBytes(len);
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143 return b;
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144 }
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145
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146 public String readOid() throws IOException {
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147 int type = readByte() & 0xff;
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148
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149 if (type != 0x06)
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150 throw new IOException("Expected DER OID, but found type " + type);
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151
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152 int len = readLength();
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153
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154 if ((len < 1) || len > available())
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155 throw new IOException("Illegal len in DER object (" + len + ")");
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156
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157 byte[] b = readBytes(len);
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158 long value = 0;
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159 StringBuilder sb = new StringBuilder(64);
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160
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161 switch (b[0] / 40) {
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162 case 0:
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163 sb.append('0');
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164 break;
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165
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166 case 1:
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167 sb.append('1');
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168 b[0] -= 40;
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169 break;
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170
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171 default:
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172 sb.append('2');
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173 b[0] -= 80;
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174 break;
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175 }
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176
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177 for (int i = 0; i < len; i++) {
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178 value = (value << 7) + (b[i] & 0x7F);
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179
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180 if ((b[i] & 0x80) == 0) {
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181 sb.append('.');
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182 sb.append(value);
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183 value = 0;
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184 }
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185 }
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186
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187 return sb.toString();
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188 }
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189
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190 public byte[] readOctetString() throws IOException {
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191 int type = readByte() & 0xff;
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192
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193 if (type != 0x04 && type != 0x03)
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194 throw new IOException("Expected DER Octetstring, but found type " + type);
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195
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196 int len = readLength();
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197
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198 if ((len < 0) || len > available())
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199 throw new IOException("Illegal len in DER object (" + len + ")");
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200
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201 byte[] b = readBytes(len);
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202 return b;
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203 }
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204
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205 }
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