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1 /* |
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2 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 package sun.security.ssl; |
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27 |
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28 import java.io.IOException; |
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29 import javax.net.ssl.SSLProtocolException; |
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30 |
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31 /* |
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32 * [RFC6066] TLS specifies a fixed maximum plaintext fragment length of |
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33 * 2^14 bytes. It may be desirable for constrained clients to negotiate |
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34 * a smaller maximum fragment length due to memory limitations or bandwidth |
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35 * limitations. |
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36 * |
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37 * In order to negotiate smaller maximum fragment lengths, clients MAY |
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38 * include an extension of type "max_fragment_length" in the (extended) |
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39 * client hello. The "extension_data" field of this extension SHALL |
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40 * contain: |
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41 * |
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42 * enum{ |
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43 * 2^9(1), 2^10(2), 2^11(3), 2^12(4), (255) |
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44 * } MaxFragmentLength; |
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45 * |
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46 * whose value is the desired maximum fragment length. |
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47 */ |
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48 final class MaxFragmentLengthExtension extends HelloExtension { |
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49 |
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50 private static final int MAX_FRAGMENT_LENGTH_512 = 1; // 2^9 |
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51 private static final int MAX_FRAGMENT_LENGTH_1024 = 2; // 2^10 |
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52 private static final int MAX_FRAGMENT_LENGTH_2048 = 3; // 2^11 |
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53 private static final int MAX_FRAGMENT_LENGTH_4096 = 4; // 2^12 |
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54 |
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55 final int maxFragmentLength; |
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56 |
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57 MaxFragmentLengthExtension(int fragmentSize) { |
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58 super(ExtensionType.EXT_MAX_FRAGMENT_LENGTH); |
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59 |
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60 if (fragmentSize < 1024) { |
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61 maxFragmentLength = MAX_FRAGMENT_LENGTH_512; |
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62 } else if (fragmentSize < 2048) { |
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63 maxFragmentLength = MAX_FRAGMENT_LENGTH_1024; |
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64 } else if (fragmentSize < 4096) { |
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65 maxFragmentLength = MAX_FRAGMENT_LENGTH_2048; |
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66 } else { |
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67 maxFragmentLength = MAX_FRAGMENT_LENGTH_4096; |
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68 } |
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69 } |
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70 |
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71 MaxFragmentLengthExtension(HandshakeInStream s, int len) |
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72 throws IOException { |
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73 super(ExtensionType.EXT_MAX_FRAGMENT_LENGTH); |
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74 |
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75 // check the extension length |
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76 if (len != 1) { |
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77 throw new SSLProtocolException("Invalid " + type + " extension"); |
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78 } |
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79 |
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80 maxFragmentLength = s.getInt8(); |
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81 if ((maxFragmentLength > 4) || (maxFragmentLength < 1)) { |
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82 throw new SSLProtocolException("Invalid " + type + " extension"); |
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83 } |
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84 } |
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85 |
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86 // Length of the encoded extension, including the type and length fields |
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87 @Override |
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88 int length() { |
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89 return 5; // 4: extension type and length fields |
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90 // 1: MaxFragmentLength field |
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91 } |
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92 |
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93 @Override |
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94 void send(HandshakeOutStream s) throws IOException { |
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95 s.putInt16(type.id); |
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96 s.putInt16(1); |
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97 s.putInt8(maxFragmentLength); |
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98 } |
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99 |
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100 int getMaxFragLen() { |
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101 switch (maxFragmentLength) { |
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102 case MAX_FRAGMENT_LENGTH_512: |
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103 return 512; |
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104 case MAX_FRAGMENT_LENGTH_1024: |
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105 return 1024; |
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106 case MAX_FRAGMENT_LENGTH_2048: |
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107 return 2048; |
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108 case MAX_FRAGMENT_LENGTH_4096: |
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109 return 4096; |
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110 } |
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111 |
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112 // unlikely to happen |
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113 return -1; |
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114 } |
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115 |
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116 static boolean needFragLenNego(int fragmentSize) { |
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117 return (fragmentSize > 0) && (fragmentSize <= 4096); |
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118 } |
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119 |
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120 static int getValidMaxFragLen(int fragmentSize) { |
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121 if (fragmentSize < 1024) { |
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122 return 512; |
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123 } else if (fragmentSize < 2048) { |
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124 return 1024; |
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125 } else if (fragmentSize < 4096) { |
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126 return 2048; |
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127 } else if (fragmentSize == 4096) { |
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128 return 4096; |
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129 } else { |
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130 return 16384; |
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131 } |
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132 } |
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133 |
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134 @Override |
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135 public String toString() { |
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136 return "Extension " + type + ", max_fragment_length: " + |
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137 "(2^" + (maxFragmentLength + 8) + ")"; |
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138 } |
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139 } |