1<?php 2// +-----------------------------------------------------------------------+ 3// | Copyright (c) 2011 Jehan | 4// | All rights reserved. | 5// | | 6// | Redistribution and use in source and binary forms, with or without | 7// | modification, are permitted provided that the following conditions | 8// | are met: | 9// | | 10// | o Redistributions of source code must retain the above copyright | 11// | notice, this list of conditions and the following disclaimer. | 12// | o Redistributions in binary form must reproduce the above copyright | 13// | notice, this list of conditions and the following disclaimer in the | 14// | documentation and/or other materials provided with the distribution.| 15// | o The names of the authors may not be used to endorse or promote | 16// | products derived from this software without specific prior written | 17// | permission. | 18// | | 19// | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | 20// | "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | 21// | LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | 22// | A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | 23// | OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | 24// | SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | 25// | LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | 26// | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | 27// | THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | 28// | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | 29// | OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | 30// | | 31// +-----------------------------------------------------------------------+ 32// | Author: Jehan <jehan.marmottard@gmail.com | 33// +-----------------------------------------------------------------------+ 34// 35// $Id$ 36 37/** 38* Implementation of SCRAM-* SASL mechanisms. 39* SCRAM mechanisms have 3 main steps (initial response, response to the server challenge, then server signature 40* verification) which keep state-awareness. Therefore a single class instanciation must be done and reused for the whole 41* authentication process. 42* 43* @author Jehan <jehan.marmottard@gmail.com> 44* @access public 45* @version 1.0 46* @package Auth_SASL 47*/ 48 49require_once('Auth/SASL/Common.php'); 50 51class Auth_SASL_SCRAM extends Auth_SASL_Common 52{ 53 /** 54 * Construct a SCRAM-H client where 'H' is a cryptographic hash function. 55 * 56 * @param string $hash The name cryptographic hash function 'H' as registered by IANA in the "Hash Function Textual 57 * Names" registry. 58 * @link http://www.iana.org/assignments/hash-function-text-names/hash-function-text-names.xml "Hash Function Textual 59 * Names" 60 * format of core PHP hash function. 61 * @access public 62 */ 63 function __construct($hash) 64 { 65 // Though I could be strict, I will actually also accept the naming used in the PHP core hash framework. 66 // For instance "sha1" is accepted, while the registered hash name should be "SHA-1". 67 $hash = strtolower($hash); 68 $hashes = array('md2' => 'md2', 69 'md5' => 'md5', 70 'sha-1' => 'sha1', 71 'sha1' => 'sha1', 72 'sha-224' > 'sha224', 73 'sha224' > 'sha224', 74 'sha-256' => 'sha256', 75 'sha256' => 'sha256', 76 'sha-384' => 'sha384', 77 'sha384' => 'sha384', 78 'sha-512' => 'sha512', 79 'sha512' => 'sha512'); 80 if (function_exists('hash_hmac') && isset($hashes[$hash])) 81 { 82 $this->hash = create_function('$data', 'return hash("' . $hashes[$hash] . '", $data, TRUE);'); 83 $this->hmac = create_function('$key,$str,$raw', 'return hash_hmac("' . $hashes[$hash] . '", $str, $key, $raw);'); 84 } 85 elseif ($hash == 'md5') 86 { 87 $this->hash = create_function('$data', 'return md5($data, true);'); 88 $this->hmac = array($this, '_HMAC_MD5'); 89 } 90 elseif (in_array($hash, array('sha1', 'sha-1'))) 91 { 92 $this->hash = create_function('$data', 'return sha1($data, true);'); 93 $this->hmac = array($this, '_HMAC_SHA1'); 94 } 95 else 96 return PEAR::raiseError('Invalid SASL mechanism type'); 97 } 98 99 /** 100 * Provides the (main) client response for SCRAM-H. 101 * 102 * @param string $authcid Authentication id (username) 103 * @param string $pass Password 104 * @param string $challenge The challenge sent by the server. 105 * If the challenge is NULL or an empty string, the result will be the "initial response". 106 * @param string $authzid Authorization id (username to proxy as) 107 * @return string|false The response (binary, NOT base64 encoded) 108 * @access public 109 */ 110 public function getResponse($authcid, $pass, $challenge = NULL, $authzid = NULL) 111 { 112 $authcid = $this->_formatName($authcid); 113 if (empty($authcid)) 114 { 115 return false; 116 } 117 if (!empty($authzid)) 118 { 119 $authzid = $this->_formatName($authzid); 120 if (empty($authzid)) 121 { 122 return false; 123 } 124 } 125 126 if (empty($challenge)) 127 { 128 return $this->_generateInitialResponse($authcid, $authzid); 129 } 130 else 131 { 132 return $this->_generateResponse($challenge, $pass); 133 } 134 135 } 136 137 /** 138 * Prepare a name for inclusion in a SCRAM response. 139 * 140 * @param string $username a name to be prepared. 141 * @return string the reformated name. 142 * @access private 143 */ 144 private function _formatName($username) 145 { 146 // TODO: prepare through the SASLprep profile of the stringprep algorithm. 147 // See RFC-4013. 148 149 $username = str_replace('=', '=3D', $username); 150 $username = str_replace(',', '=2C', $username); 151 return $username; 152 } 153 154 /** 155 * Generate the initial response which can be either sent directly in the first message or as a response to an empty 156 * server challenge. 157 * 158 * @param string $authcid Prepared authentication identity. 159 * @param string $authzid Prepared authorization identity. 160 * @return string The SCRAM response to send. 161 * @access private 162 */ 163 private function _generateInitialResponse($authcid, $authzid) 164 { 165 $init_rep = ''; 166 $gs2_cbind_flag = 'n,'; // TODO: support channel binding. 167 $this->gs2_header = $gs2_cbind_flag . (!empty($authzid)? 'a=' . $authzid : '') . ','; 168 169 // I must generate a client nonce and "save" it for later comparison on second response. 170 $this->cnonce = $this->_getCnonce(); 171 // XXX: in the future, when mandatory and/or optional extensions are defined in any updated RFC, 172 // this message can be updated. 173 $this->first_message_bare = 'n=' . $authcid . ',r=' . $this->cnonce; 174 return $this->gs2_header . $this->first_message_bare; 175 } 176 177 /** 178 * Parses and verifies a non-empty SCRAM challenge. 179 * 180 * @param string $challenge The SCRAM challenge 181 * @return string|false The response to send; false in case of wrong challenge or if an initial response has not 182 * been generated first. 183 * @access private 184 */ 185 private function _generateResponse($challenge, $password) 186 { 187 // XXX: as I don't support mandatory extension, I would fail on them. 188 // And I simply ignore any optional extension. 189 $server_message_regexp = "#^r=([\x21-\x2B\x2D-\x7E]+),s=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?),i=([0-9]*)(,[A-Za-z]=[^,])*$#"; 190 if (!isset($this->cnonce, $this->gs2_header) 191 || !preg_match($server_message_regexp, $challenge, $matches)) 192 { 193 return false; 194 } 195 $nonce = $matches[1]; 196 $salt = base64_decode($matches[2]); 197 if (!$salt) 198 { 199 // Invalid Base64. 200 return false; 201 } 202 $i = intval($matches[3]); 203 204 $cnonce = substr($nonce, 0, strlen($this->cnonce)); 205 if ($cnonce <> $this->cnonce) 206 { 207 // Invalid challenge! Are we under attack? 208 return false; 209 } 210 211 $channel_binding = 'c=' . base64_encode($this->gs2_header); // TODO: support channel binding. 212 $final_message = $channel_binding . ',r=' . $nonce; // XXX: no extension. 213 214 // TODO: $password = $this->normalize($password); // SASLprep profile of stringprep. 215 $saltedPassword = $this->hi($password, $salt, $i); 216 $this->saltedPassword = $saltedPassword; 217 $clientKey = call_user_func($this->hmac, $saltedPassword, "Client Key", TRUE); 218 $storedKey = call_user_func($this->hash, $clientKey, TRUE); 219 $authMessage = $this->first_message_bare . ',' . $challenge . ',' . $final_message; 220 $this->authMessage = $authMessage; 221 $clientSignature = call_user_func($this->hmac, $storedKey, $authMessage, TRUE); 222 $clientProof = $clientKey ^ $clientSignature; 223 $proof = ',p=' . base64_encode($clientProof); 224 225 return $final_message . $proof; 226 } 227 228 /** 229 * SCRAM has also a server verification step. On a successful outcome, it will send additional data which must 230 * absolutely be checked against this function. If this fails, the entity which we are communicating with is probably 231 * not the server as it has not access to your ServerKey. 232 * 233 * @param string $data The additional data sent along a successful outcome. 234 * @return bool Whether the server has been authenticated. 235 * If false, the client must close the connection and consider to be under a MITM attack. 236 * @access public 237 */ 238 public function processOutcome($data) 239 { 240 $verifier_regexp = '#^v=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?)$#'; 241 if (!isset($this->saltedPassword, $this->authMessage) 242 || !preg_match($verifier_regexp, $data, $matches)) 243 { 244 // This cannot be an outcome, you never sent the challenge's response. 245 return false; 246 } 247 248 $verifier = $matches[1]; 249 $proposed_serverSignature = base64_decode($verifier); 250 $serverKey = call_user_func($this->hmac, $this->saltedPassword, "Server Key", true); 251 $serverSignature = call_user_func($this->hmac, $serverKey, $this->authMessage, TRUE); 252 return ($proposed_serverSignature === $serverSignature); 253 } 254 255 /** 256 * Hi() call, which is essentially PBKDF2 (RFC-2898) with HMAC-H() as the pseudorandom function. 257 * 258 * @param string $str The string to hash. 259 * @param string $hash The hash value. 260 * @param int $i The iteration count. 261 * @access private 262 */ 263 private function hi($str, $salt, $i) 264 { 265 $int1 = "\0\0\0\1"; 266 $ui = call_user_func($this->hmac, $str, $salt . $int1, true); 267 $result = $ui; 268 for ($k = 1; $k < $i; $k++) 269 { 270 $ui = call_user_func($this->hmac, $str, $ui, true); 271 $result = $result ^ $ui; 272 } 273 return $result; 274 } 275 276 277 /** 278 * Creates the client nonce for the response 279 * 280 * @return string The cnonce value 281 * @access private 282 * @author Richard Heyes <richard@php.net> 283 */ 284 private function _getCnonce() 285 { 286 // TODO: I reused the nonce function from the DigestMD5 class. 287 // I should probably make this a protected function in Common. 288 if (@file_exists('/dev/urandom') && $fd = @fopen('/dev/urandom', 'r')) { 289 return base64_encode(fread($fd, 32)); 290 291 } elseif (@file_exists('/dev/random') && $fd = @fopen('/dev/random', 'r')) { 292 return base64_encode(fread($fd, 32)); 293 294 } else { 295 $str = ''; 296 for ($i=0; $i<32; $i++) { 297 $str .= chr(mt_rand(0, 255)); 298 } 299 300 return base64_encode($str); 301 } 302 } 303 304} 305 306?> 307