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1 <?php
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2 // +-----------------------------------------------------------------------+
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3 // | Copyright (c) 2011 Jehan |
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4 // | All rights reserved. |
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5 // | |
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6 // | Redistribution and use in source and binary forms, with or without |
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7 // | modification, are permitted provided that the following conditions |
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8 // | are met: |
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9 // | |
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10 // | o Redistributions of source code must retain the above copyright |
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11 // | notice, this list of conditions and the following disclaimer. |
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12 // | o Redistributions in binary form must reproduce the above copyright |
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13 // | notice, this list of conditions and the following disclaimer in the |
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14 // | documentation and/or other materials provided with the distribution.|
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15 // | o The names of the authors may not be used to endorse or promote |
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16 // | products derived from this software without specific prior written |
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17 // | permission. |
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18 // | |
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19 // | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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20 // | "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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21 // | LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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22 // | A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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23 // | OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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24 // | SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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25 // | LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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26 // | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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27 // | THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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28 // | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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29 // | OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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30 // | |
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31 // +-----------------------------------------------------------------------+
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32 // | Author: Jehan <jehan.marmottard@gmail.com |
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33 // +-----------------------------------------------------------------------+
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34 //
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35 // $Id$
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36
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37 /**
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38 * Implementation of SCRAM-* SASL mechanisms.
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39 * SCRAM mechanisms have 3 main steps (initial response, response to the server challenge, then server signature
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40 * verification) which keep state-awareness. Therefore a single class instanciation must be done and reused for the whole
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41 * authentication process.
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42 *
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43 * @author Jehan <jehan.marmottard@gmail.com>
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44 * @access public
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45 * @version 1.0
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46 * @package Auth_SASL
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47 */
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48
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49 require_once('Auth/SASL/Common.php');
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50
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51 class Auth_SASL_SCRAM extends Auth_SASL_Common
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52 {
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53 /**
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54 * Construct a SCRAM-H client where 'H' is a cryptographic hash function.
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55 *
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56 * @param string $hash The name cryptographic hash function 'H' as registered by IANA in the "Hash Function Textual
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57 * Names" registry.
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58 * @link http://www.iana.org/assignments/hash-function-text-names/hash-function-text-names.xml "Hash Function Textual
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59 * Names"
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60 * format of core PHP hash function.
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61 * @access public
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62 */
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63 function __construct($hash)
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64 {
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65 // Though I could be strict, I will actually also accept the naming used in the PHP core hash framework.
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66 // For instance "sha1" is accepted, while the registered hash name should be "SHA-1".
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67 $hash = strtolower($hash);
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68 $hashes = array('md2' => 'md2',
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69 'md5' => 'md5',
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70 'sha-1' => 'sha1',
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71 'sha1' => 'sha1',
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72 'sha-224' > 'sha224',
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73 'sha224' > 'sha224',
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74 'sha-256' => 'sha256',
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75 'sha256' => 'sha256',
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76 'sha-384' => 'sha384',
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77 'sha384' => 'sha384',
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78 'sha-512' => 'sha512',
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79 'sha512' => 'sha512');
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80 if (function_exists('hash_hmac') && isset($hashes[$hash]))
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81 {
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82 $this->hash = create_function('$data', 'return hash("' . $hashes[$hash] . '", $data, TRUE);');
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83 $this->hmac = create_function('$key,$str,$raw', 'return hash_hmac("' . $hashes[$hash] . '", $str, $key, $raw);');
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84 }
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85 elseif ($hash == 'md5')
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86 {
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87 $this->hash = create_function('$data', 'return md5($data, true);');
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88 $this->hmac = array($this, '_HMAC_MD5');
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89 }
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90 elseif (in_array($hash, array('sha1', 'sha-1')))
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91 {
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92 $this->hash = create_function('$data', 'return sha1($data, true);');
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93 $this->hmac = array($this, '_HMAC_SHA1');
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94 }
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95 else
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96 return PEAR::raiseError('Invalid SASL mechanism type');
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97 }
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98
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99 /**
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100 * Provides the (main) client response for SCRAM-H.
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101 *
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102 * @param string $authcid Authentication id (username)
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103 * @param string $pass Password
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104 * @param string $challenge The challenge sent by the server.
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105 * If the challenge is NULL or an empty string, the result will be the "initial response".
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106 * @param string $authzid Authorization id (username to proxy as)
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107 * @return string|false The response (binary, NOT base64 encoded)
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108 * @access public
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109 */
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110 public function getResponse($authcid, $pass, $challenge = NULL, $authzid = NULL)
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111 {
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112 $authcid = $this->_formatName($authcid);
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113 if (empty($authcid))
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114 {
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115 return false;
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116 }
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117 if (!empty($authzid))
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118 {
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119 $authzid = $this->_formatName($authzid);
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120 if (empty($authzid))
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121 {
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122 return false;
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123 }
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124 }
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125
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126 if (empty($challenge))
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127 {
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128 return $this->_generateInitialResponse($authcid, $authzid);
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129 }
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130 else
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131 {
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132 return $this->_generateResponse($challenge, $pass);
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133 }
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134
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135 }
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136
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137 /**
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138 * Prepare a name for inclusion in a SCRAM response.
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139 *
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140 * @param string $username a name to be prepared.
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141 * @return string the reformated name.
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142 * @access private
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143 */
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144 private function _formatName($username)
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145 {
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146 // TODO: prepare through the SASLprep profile of the stringprep algorithm.
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147 // See RFC-4013.
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148
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149 $username = str_replace('=', '=3D', $username);
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150 $username = str_replace(',', '=2C', $username);
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151 return $username;
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152 }
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153
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154 /**
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155 * Generate the initial response which can be either sent directly in the first message or as a response to an empty
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156 * server challenge.
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157 *
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158 * @param string $authcid Prepared authentication identity.
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159 * @param string $authzid Prepared authorization identity.
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160 * @return string The SCRAM response to send.
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161 * @access private
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162 */
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163 private function _generateInitialResponse($authcid, $authzid)
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164 {
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165 $init_rep = '';
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166 $gs2_cbind_flag = 'n,'; // TODO: support channel binding.
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167 $this->gs2_header = $gs2_cbind_flag . (!empty($authzid)? 'a=' . $authzid : '') . ',';
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168
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169 // I must generate a client nonce and "save" it for later comparison on second response.
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170 $this->cnonce = $this->_getCnonce();
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171 // XXX: in the future, when mandatory and/or optional extensions are defined in any updated RFC,
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172 // this message can be updated.
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173 $this->first_message_bare = 'n=' . $authcid . ',r=' . $this->cnonce;
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174 return $this->gs2_header . $this->first_message_bare;
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175 }
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176
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177 /**
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178 * Parses and verifies a non-empty SCRAM challenge.
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179 *
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180 * @param string $challenge The SCRAM challenge
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181 * @return string|false The response to send; false in case of wrong challenge or if an initial response has not
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182 * been generated first.
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183 * @access private
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184 */
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185 private function _generateResponse($challenge, $password)
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186 {
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187 // XXX: as I don't support mandatory extension, I would fail on them.
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188 // And I simply ignore any optional extension.
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189 $server_message_regexp = "#^r=([\x21-\x2B\x2D-\x7E]+),s=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?),i=([0-9]*)(,[A-Za-z]=[^,])*$#";
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190 if (!isset($this->cnonce, $this->gs2_header)
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191 || !preg_match($server_message_regexp, $challenge, $matches))
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192 {
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193 return false;
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194 }
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195 $nonce = $matches[1];
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196 $salt = base64_decode($matches[2]);
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197 if (!$salt)
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198 {
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199 // Invalid Base64.
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200 return false;
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201 }
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202 $i = intval($matches[3]);
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203
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204 $cnonce = substr($nonce, 0, strlen($this->cnonce));
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205 if ($cnonce <> $this->cnonce)
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206 {
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207 // Invalid challenge! Are we under attack?
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208 return false;
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209 }
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210
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211 $channel_binding = 'c=' . base64_encode($this->gs2_header); // TODO: support channel binding.
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212 $final_message = $channel_binding . ',r=' . $nonce; // XXX: no extension.
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213
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214 // TODO: $password = $this->normalize($password); // SASLprep profile of stringprep.
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215 $saltedPassword = $this->hi($password, $salt, $i);
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216 $this->saltedPassword = $saltedPassword;
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217 $clientKey = call_user_func($this->hmac, $saltedPassword, "Client Key", TRUE);
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218 $storedKey = call_user_func($this->hash, $clientKey, TRUE);
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219 $authMessage = $this->first_message_bare . ',' . $challenge . ',' . $final_message;
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220 $this->authMessage = $authMessage;
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221 $clientSignature = call_user_func($this->hmac, $storedKey, $authMessage, TRUE);
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222 $clientProof = $clientKey ^ $clientSignature;
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223 $proof = ',p=' . base64_encode($clientProof);
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224
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225 return $final_message . $proof;
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226 }
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227
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228 /**
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229 * SCRAM has also a server verification step. On a successful outcome, it will send additional data which must
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230 * absolutely be checked against this function. If this fails, the entity which we are communicating with is probably
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231 * not the server as it has not access to your ServerKey.
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232 *
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233 * @param string $data The additional data sent along a successful outcome.
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234 * @return bool Whether the server has been authenticated.
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235 * If false, the client must close the connection and consider to be under a MITM attack.
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236 * @access public
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237 */
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238 public function processOutcome($data)
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239 {
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240 $verifier_regexp = '#^v=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?)$#';
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241 if (!isset($this->saltedPassword, $this->authMessage)
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242 || !preg_match($verifier_regexp, $data, $matches))
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243 {
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244 // This cannot be an outcome, you never sent the challenge's response.
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245 return false;
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246 }
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247
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248 $verifier = $matches[1];
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249 $proposed_serverSignature = base64_decode($verifier);
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250 $serverKey = call_user_func($this->hmac, $this->saltedPassword, "Server Key", true);
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251 $serverSignature = call_user_func($this->hmac, $serverKey, $this->authMessage, TRUE);
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252 return ($proposed_serverSignature === $serverSignature);
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253 }
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254
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255 /**
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256 * Hi() call, which is essentially PBKDF2 (RFC-2898) with HMAC-H() as the pseudorandom function.
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257 *
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258 * @param string $str The string to hash.
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259 * @param string $hash The hash value.
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260 * @param int $i The iteration count.
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261 * @access private
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262 */
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263 private function hi($str, $salt, $i)
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264 {
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265 $int1 = "\0\0\0\1";
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266 $ui = call_user_func($this->hmac, $str, $salt . $int1, true);
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267 $result = $ui;
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268 for ($k = 1; $k < $i; $k++)
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269 {
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270 $ui = call_user_func($this->hmac, $str, $ui, true);
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271 $result = $result ^ $ui;
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272 }
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273 return $result;
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274 }
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275
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276
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277 /**
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278 * Creates the client nonce for the response
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279 *
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280 * @return string The cnonce value
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281 * @access private
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282 * @author Richard Heyes <richard@php.net>
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283 */
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284 private function _getCnonce()
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285 {
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286 // TODO: I reused the nonce function from the DigestMD5 class.
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287 // I should probably make this a protected function in Common.
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288 if (@file_exists('/dev/urandom') && $fd = @fopen('/dev/urandom', 'r')) {
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289 return base64_encode(fread($fd, 32));
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290
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291 } elseif (@file_exists('/dev/random') && $fd = @fopen('/dev/random', 'r')) {
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292 return base64_encode(fread($fd, 32));
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293
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294 } else {
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295 $str = '';
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296 for ($i=0; $i<32; $i++) {
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297 $str .= chr(mt_rand(0, 255));
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298 }
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299
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300 return base64_encode($str);
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301 }
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302 }
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303
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304 }
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305
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306 ?>
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