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