<?php // +-----------------------------------------------------------------------+ // | Copyright (c) 2011 Jehan | // | All rights reserved. | // | | // | Redistribution and use in source and binary forms, with or without | // | modification, are permitted provided that the following conditions | // | are met: | // | | // | o Redistributions of source code must retain the above copyright | // | notice, this list of conditions and the following disclaimer. | // | o Redistributions in binary form must reproduce the above copyright | // | notice, this list of conditions and the following disclaimer in the | // | documentation and/or other materials provided with the distribution.| // | o The names of the authors may not be used to endorse or promote | // | products derived from this software without specific prior written | // | permission. | // | | // | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | // | "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | // | LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | // | A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | // | OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | // | SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | // | LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | // | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | // | THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | // | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | // | OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | // | | // +-----------------------------------------------------------------------+ // | Author: Jehan <jehan.marmottard@gmail.com | // +-----------------------------------------------------------------------+ // // $Id$ /** * Implementation of SCRAM-* SASL mechanisms. * SCRAM mechanisms have 3 main steps (initial response, response to the server challenge, then server signature * verification) which keep state-awareness. Therefore a single class instanciation must be done and reused for the whole * authentication process. * * @author Jehan <jehan.marmottard@gmail.com> * @access public * @version 1.0 * @package Auth_SASL */ require_once('Auth/SASL/Common.php'); class Auth_SASL_SCRAM extends Auth_SASL_Common { /** * Construct a SCRAM-H client where 'H' is a cryptographic hash function. * * @param string $hash The name cryptographic hash function 'H' as registered by IANA in the "Hash Function Textual * Names" registry. * @link http://www.iana.org/assignments/hash-function-text-names/hash-function-text-names.xml "Hash Function Textual * Names" * format of core PHP hash function. * @access public */ function __construct($hash) { // Though I could be strict, I will actually also accept the naming used in the PHP core hash framework. // For instance "sha1" is accepted, while the registered hash name should be "SHA-1". $hash = strtolower($hash); $hashes = array('md2' => 'md2', 'md5' => 'md5', 'sha-1' => 'sha1', 'sha1' => 'sha1', 'sha-224' > 'sha224', 'sha224' > 'sha224', 'sha-256' => 'sha256', 'sha256' => 'sha256', 'sha-384' => 'sha384', 'sha384' => 'sha384', 'sha-512' => 'sha512', 'sha512' => 'sha512'); if (function_exists('hash_hmac') && isset($hashes[$hash])) { $this->hash = create_function('$data', 'return hash("' . $hashes[$hash] . '", $data, TRUE);'); $this->hmac = create_function('$key,$str,$raw', 'return hash_hmac("' . $hashes[$hash] . '", $str, $key, $raw);'); } elseif ($hash == 'md5') { $this->hash = create_function('$data', 'return md5($data, true);'); $this->hmac = array($this, '_HMAC_MD5'); } elseif (in_array($hash, array('sha1', 'sha-1'))) { $this->hash = create_function('$data', 'return sha1($data, true);'); $this->hmac = array($this, '_HMAC_SHA1'); } else return PEAR::raiseError('Invalid SASL mechanism type'); } /** * Provides the (main) client response for SCRAM-H. * * @param string $authcid Authentication id (username) * @param string $pass Password * @param string $challenge The challenge sent by the server. * If the challenge is NULL or an empty string, the result will be the "initial response". * @param string $authzid Authorization id (username to proxy as) * @return string|false The response (binary, NOT base64 encoded) * @access public */ public function getResponse($authcid, $pass, $challenge = NULL, $authzid = NULL) { $authcid = $this->_formatName($authcid); if (empty($authcid)) { return false; } if (!empty($authzid)) { $authzid = $this->_formatName($authzid); if (empty($authzid)) { return false; } } if (empty($challenge)) { return $this->_generateInitialResponse($authcid, $authzid); } else { return $this->_generateResponse($challenge, $pass); } } /** * Prepare a name for inclusion in a SCRAM response. * * @param string $username a name to be prepared. * @return string the reformated name. * @access private */ private function _formatName($username) { // TODO: prepare through the SASLprep profile of the stringprep algorithm. // See RFC-4013. $username = str_replace('=', '=3D', $username); $username = str_replace(',', '=2C', $username); return $username; } /** * Generate the initial response which can be either sent directly in the first message or as a response to an empty * server challenge. * * @param string $authcid Prepared authentication identity. * @param string $authzid Prepared authorization identity. * @return string The SCRAM response to send. * @access private */ private function _generateInitialResponse($authcid, $authzid) { $init_rep = ''; $gs2_cbind_flag = 'n,'; // TODO: support channel binding. $this->gs2_header = $gs2_cbind_flag . (!empty($authzid)? 'a=' . $authzid : '') . ','; // I must generate a client nonce and "save" it for later comparison on second response. $this->cnonce = $this->_getCnonce(); // XXX: in the future, when mandatory and/or optional extensions are defined in any updated RFC, // this message can be updated. $this->first_message_bare = 'n=' . $authcid . ',r=' . $this->cnonce; return $this->gs2_header . $this->first_message_bare; } /** * Parses and verifies a non-empty SCRAM challenge. * * @param string $challenge The SCRAM challenge * @return string|false The response to send; false in case of wrong challenge or if an initial response has not * been generated first. * @access private */ private function _generateResponse($challenge, $password) { // XXX: as I don't support mandatory extension, I would fail on them. // And I simply ignore any optional extension. $server_message_regexp = "#^r=([\x21-\x2B\x2D-\x7E]+),s=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?),i=([0-9]*)(,[A-Za-z]=[^,])*$#"; if (!isset($this->cnonce, $this->gs2_header) || !preg_match($server_message_regexp, $challenge, $matches)) { return false; } $nonce = $matches[1]; $salt = base64_decode($matches[2]); if (!$salt) { // Invalid Base64. return false; } $i = intval($matches[3]); $cnonce = substr($nonce, 0, strlen($this->cnonce)); if ($cnonce <> $this->cnonce) { // Invalid challenge! Are we under attack? return false; } $channel_binding = 'c=' . base64_encode($this->gs2_header); // TODO: support channel binding. $final_message = $channel_binding . ',r=' . $nonce; // XXX: no extension. // TODO: $password = $this->normalize($password); // SASLprep profile of stringprep. $saltedPassword = $this->hi($password, $salt, $i); $this->saltedPassword = $saltedPassword; $clientKey = call_user_func($this->hmac, $saltedPassword, "Client Key", TRUE); $storedKey = call_user_func($this->hash, $clientKey, TRUE); $authMessage = $this->first_message_bare . ',' . $challenge . ',' . $final_message; $this->authMessage = $authMessage; $clientSignature = call_user_func($this->hmac, $storedKey, $authMessage, TRUE); $clientProof = $clientKey ^ $clientSignature; $proof = ',p=' . base64_encode($clientProof); return $final_message . $proof; } /** * SCRAM has also a server verification step. On a successful outcome, it will send additional data which must * absolutely be checked against this function. If this fails, the entity which we are communicating with is probably * not the server as it has not access to your ServerKey. * * @param string $data The additional data sent along a successful outcome. * @return bool Whether the server has been authenticated. * If false, the client must close the connection and consider to be under a MITM attack. * @access public */ public function processOutcome($data) { $verifier_regexp = '#^v=((?:[A-Za-z0-9/+]{4})*(?:[A-Za-z0-9]{3}=|[A-Xa-z0-9]{2}==)?)$#'; if (!isset($this->saltedPassword, $this->authMessage) || !preg_match($verifier_regexp, $data, $matches)) { // This cannot be an outcome, you never sent the challenge's response. return false; } $verifier = $matches[1]; $proposed_serverSignature = base64_decode($verifier); $serverKey = call_user_func($this->hmac, $this->saltedPassword, "Server Key", true); $serverSignature = call_user_func($this->hmac, $serverKey, $this->authMessage, TRUE); return ($proposed_serverSignature === $serverSignature); } /** * Hi() call, which is essentially PBKDF2 (RFC-2898) with HMAC-H() as the pseudorandom function. * * @param string $str The string to hash. * @param string $hash The hash value. * @param int $i The iteration count. * @access private */ private function hi($str, $salt, $i) { $int1 = "\0\0\0\1"; $ui = call_user_func($this->hmac, $str, $salt . $int1, true); $result = $ui; for ($k = 1; $k < $i; $k++) { $ui = call_user_func($this->hmac, $str, $ui, true); $result = $result ^ $ui; } return $result; } /** * Creates the client nonce for the response * * @return string The cnonce value * @access private * @author Richard Heyes <richard@php.net> */ private function _getCnonce() { // TODO: I reused the nonce function from the DigestMD5 class. // I should probably make this a protected function in Common. if (@file_exists('/dev/urandom') && $fd = @fopen('/dev/urandom', 'r')) { return base64_encode(fread($fd, 32)); } elseif (@file_exists('/dev/random') && $fd = @fopen('/dev/random', 'r')) { return base64_encode(fread($fd, 32)); } else { $str = ''; for ($i=0; $i<32; $i++) { $str .= chr(mt_rand(0, 255)); } return base64_encode($str); } } } ?>