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 49class Auth_SASL_SCRAM extends Auth_SASL_Common 50{ 51 /** 52 * Construct a SCRAM-H client where 'H' is a cryptographic hash function. 53 * 54 * @param string $hash The name cryptographic hash function 'H' as registered by IANA in the "Hash Function Textual 55 * Names" registry. 56 * @link http://www.iana.org/assignments/hash-function-text-names/hash-function-text-names.xml "Hash Function Textual 57 * Names" 58 * format of core PHP hash function. 59 * @access public 60 */ 61 function __construct($hash) 62 { 63 // Though I could be strict, I will actually also accept the naming used in the PHP core hash framework. 64 // For instance "sha1" is accepted, while the registered hash name should be "SHA-1". 65 $hash = strtolower($hash); 66 $hashes = array('md2' => 'md2', 67 'md5' => 'md5', 68 'sha-1' => 'sha1', 69 'sha1' => 'sha1', 70 'sha-224' > 'sha224', 71 'sha224' > 'sha224', 72 'sha-256' => 'sha256', 73 'sha256' => 'sha256', 74 'sha-384' => 'sha384', 75 'sha384' => 'sha384', 76 'sha-512' => 'sha512', 77 'sha512' => 'sha512'); 78 if (function_exists('hash_hmac') && isset($hashes[$hash])) 79 { 80 $this->hash = function($data) use ($hashes, $hash) {return hash($hashes[$hash], $data, true);}; 81 $this->hmac = function($key, $str, $raw) use ($hashes, $hash) {return hash_hmac($hashes[$hash], $str, $key, $raw);}; 82 } 83 elseif ($hash == 'md5') 84 { 85 $this->hash = function($data) {return md5($data, true);}; 86 $this->hmac = array($this, '_HMAC_MD5'); 87 } 88 elseif (in_array($hash, array('sha1', 'sha-1'))) 89 { 90 $this->hash = function($data) {return sha1($data, true);}; 91 $this->hmac = array($this, '_HMAC_SHA1'); 92 } 93 else 94 return $this->raiseError('Invalid SASL mechanism type'); 95 } 96 97 /** 98 * Provides the (main) client response for SCRAM-H. 99 * 100 * @param string $authcid Authentication id (username) 101 * @param string $pass Password 102 * @param string $challenge The challenge sent by the server. 103 * If the challenge is NULL or an empty string, the result will be the "initial response". 104 * @param string $authzid Authorization id (username to proxy as) 105 * @return string|false The response (binary, NOT base64 encoded) 106 * @access public 107 */ 108 public function getResponse($authcid, $pass, $challenge = NULL, $authzid = NULL) 109 { 110 $authcid = $this->_formatName($authcid); 111 if (empty($authcid)) 112 { 113 return false; 114 } 115 if (!empty($authzid)) 116 { 117 $authzid = $this->_formatName($authzid); 118 if (empty($authzid)) 119 { 120 return false; 121 } 122 } 123 124 if (empty($challenge)) 125 { 126 return $this->_generateInitialResponse($authcid, $authzid); 127 } 128 else 129 { 130 return $this->_generateResponse($challenge, $pass); 131 } 132 133 } 134 135 /** 136 * Prepare a name for inclusion in a SCRAM response. 137 * 138 * @param string $username a name to be prepared. 139 * @return string the reformated name. 140 * @access private 141 */ 142 private function _formatName($username) 143 { 144 // TODO: prepare through the SASLprep profile of the stringprep algorithm. 145 // See RFC-4013. 146 147 $username = str_replace('=', '=3D', $username); 148 $username = str_replace(',', '=2C', $username); 149 return $username; 150 } 151 152 /** 153 * Generate the initial response which can be either sent directly in the first message or as a response to an empty 154 * server challenge. 155 * 156 * @param string $authcid Prepared authentication identity. 157 * @param string $authzid Prepared authorization identity. 158 * @return string The SCRAM response to send. 159 * @access private 160 */ 161 private function _generateInitialResponse($authcid, $authzid) 162 { 163 $init_rep = ''; 164 $gs2_cbind_flag = 'n,'; // TODO: support channel binding. 165 $this->gs2_header = $gs2_cbind_flag . (!empty($authzid)? 'a=' . $authzid : '') . ','; 166 167 // I must generate a client nonce and "save" it for later comparison on second response. 168 $this->cnonce = $this->_getCnonce(); 169 // XXX: in the future, when mandatory and/or optional extensions are defined in any updated RFC, 170 // this message can be updated. 171 $this->first_message_bare = 'n=' . $authcid . ',r=' . $this->cnonce; 172 return $this->gs2_header . $this->first_message_bare; 173 } 174 175 /** 176 * Parses and verifies a non-empty SCRAM challenge. 177 * 178 * @param string $challenge The SCRAM challenge 179 * @return string|false The response to send; false in case of wrong challenge or if an initial response has not 180 * been generated first. 181 * @access private 182 */ 183 private function _generateResponse($challenge, $password) 184 { 185 // XXX: as I don't support mandatory extension, I would fail on them. 186 // And I simply ignore any optional extension. 187 $server_message_regexp = "#^r=([\x21-\x2B\x2D-\x7E]+),s=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?),i=([0-9]*)(,[A-Za-z]=[^,])*$#"; 188 if (!isset($this->cnonce, $this->gs2_header) 189 || !preg_match($server_message_regexp, $challenge, $matches)) 190 { 191 return false; 192 } 193 $nonce = $matches[1]; 194 $salt = base64_decode($matches[2]); 195 if (!$salt) 196 { 197 // Invalid Base64. 198 return false; 199 } 200 $i = intval($matches[3]); 201 202 $cnonce = substr($nonce, 0, strlen($this->cnonce)); 203 if ($cnonce <> $this->cnonce) 204 { 205 // Invalid challenge! Are we under attack? 206 return false; 207 } 208 209 $channel_binding = 'c=' . base64_encode($this->gs2_header); // TODO: support channel binding. 210 $final_message = $channel_binding . ',r=' . $nonce; // XXX: no extension. 211 212 // TODO: $password = $this->normalize($password); // SASLprep profile of stringprep. 213 $saltedPassword = $this->hi($password, $salt, $i); 214 $this->saltedPassword = $saltedPassword; 215 $clientKey = call_user_func($this->hmac, $saltedPassword, "Client Key", TRUE); 216 $storedKey = call_user_func($this->hash, $clientKey, TRUE); 217 $authMessage = $this->first_message_bare . ',' . $challenge . ',' . $final_message; 218 $this->authMessage = $authMessage; 219 $clientSignature = call_user_func($this->hmac, $storedKey, $authMessage, TRUE); 220 $clientProof = $clientKey ^ $clientSignature; 221 $proof = ',p=' . base64_encode($clientProof); 222 223 return $final_message . $proof; 224 } 225 226 /** 227 * SCRAM has also a server verification step. On a successful outcome, it will send additional data which must 228 * absolutely be checked against this function. If this fails, the entity which we are communicating with is probably 229 * not the server as it has not access to your ServerKey. 230 * 231 * @param string $data The additional data sent along a successful outcome. 232 * @return bool Whether the server has been authenticated. 233 * If false, the client must close the connection and consider to be under a MITM attack. 234 * @access public 235 */ 236 public function processOutcome($data) 237 { 238 $verifier_regexp = '#^v=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?)$#'; 239 if (!isset($this->saltedPassword, $this->authMessage) 240 || !preg_match($verifier_regexp, $data, $matches)) 241 { 242 // This cannot be an outcome, you never sent the challenge's response. 243 return false; 244 } 245 246 $verifier = $matches[1]; 247 $proposed_serverSignature = base64_decode($verifier); 248 $serverKey = call_user_func($this->hmac, $this->saltedPassword, "Server Key", true); 249 $serverSignature = call_user_func($this->hmac, $serverKey, $this->authMessage, TRUE); 250 return ($proposed_serverSignature === $serverSignature); 251 } 252 253 /** 254 * Hi() call, which is essentially PBKDF2 (RFC-2898) with HMAC-H() as the pseudorandom function. 255 * 256 * @param string $str The string to hash. 257 * @param string $hash The hash value. 258 * @param int $i The iteration count. 259 * @access private 260 */ 261 private function hi($str, $salt, $i) 262 { 263 $int1 = "\0\0\0\1"; 264 $ui = call_user_func($this->hmac, $str, $salt . $int1, true); 265 $result = $ui; 266 for ($k = 1; $k < $i; $k++) 267 { 268 $ui = call_user_func($this->hmac, $str, $ui, true); 269 $result = $result ^ $ui; 270 } 271 return $result; 272 } 273 274 275 /** 276 * Creates the client nonce for the response 277 * 278 * @return string The cnonce value 279 * @access private 280 * @author Richard Heyes <richard@php.net> 281 */ 282 private function _getCnonce() 283 { 284 // TODO: I reused the nonce function from the DigestMD5 class. 285 // I should probably make this a protected function in Common. 286 if (@file_exists('/dev/urandom') && $fd = @fopen('/dev/urandom', 'r')) { 287 return base64_encode(fread($fd, 32)); 288 289 } elseif (@file_exists('/dev/random') && $fd = @fopen('/dev/random', 'r')) { 290 return base64_encode(fread($fd, 32)); 291 292 } else { 293 $str = ''; 294 for ($i=0; $i<32; $i++) { 295 $str .= chr(mt_rand(0, 255)); 296 } 297 298 return base64_encode($str); 299 } 300 } 301}