Re: [PEAR-QA] Re: Maintenance of Auth_SASL PEAR package

From cdff2c6a7e124603179e95d6911d583ea17eb577 Mon Sep 17 00:00:00 2001
From: Jehan <[email protected]>
Date: Thu, 1 Sep 2011 18:25:40 +0200
Subject: [PATCH] - New SCRAM-* mechanisms support.

Working support for basic SCRAM. I don't support yet channel binding
(SCRAM-*-PLUS mechanisms) and there are some formating (with stringprep in
particular) that I don't do yet.

- The SASL factory has also been updated to generate a SCRAM authentifier.

- The mechanism naming is fixed for various mechanisms.

It would refuse for instance "CRAM-MD5" which is the official name of the
mechanism but would authorize "crammd5"!
---
 Auth/SASL.php        |   23 ++++-
 Auth/SASL/Common.php |   40 ++++++-
 Auth/SASL/SCRAM.php  |  306 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 363 insertions(+), 6 deletions(-)
 create mode 100755 Auth/SASL/SCRAM.php

diff --git a/Auth/SASL.php b/Auth/SASL.php
index b2be93c..8657069 100755
--- a/Auth/SASL.php
+++ b/Auth/SASL.php
@@ -55,6 +55,7 @@ class Auth_SASL
     *                             Plain
     *                             CramMD5
     *                             DigestMD5
+    *                             SCRAM-* (any mechanism of the SCRAM family)
     *                     Types are not case sensitive
     */
     function &factory($type)
@@ -81,22 +82,42 @@ class Auth_SASL
                 break;
 
             case 'crammd5':
+                $msg = 'Deprecated mechanism name. Use IANA-registered name: CRAM-MD5.';
+                trigger_error($msg, E_USER_DEPRECATED);
+            case 'cram-md5':
                 $filename  = 'Auth/SASL/CramMD5.php';
                 $classname = 'Auth_SASL_CramMD5';
                 break;
 
             case 'digestmd5':
+                $msg = 'Deprecated mechanism name. Use IANA-registered name: DIGEST-MD5.';
+                trigger_error($msg, E_USER_DEPRECATED);
+            case 'digest-md5':
+                $msg = 'DIGEST-MD5 is a deprecated SASL mechanism as per RFC-6331. Using it could be a security risk.';
+                trigger_error($msg, E_USER_NOTICE);
                 $filename  = 'Auth/SASL/DigestMD5.php';
                 $classname = 'Auth_SASL_DigestMD5';
                 break;
 
             default:
+                $scram = '/^SCRAM-(.{1,9})$/i';
+                if (preg_match($scram, $type, $matches))
+                {
+                    $hash = $matches[1];
+                    $filename = dirname(__FILE__) .'/SASL/SCRAM.php';
+                    $classname = 'Auth_SASL_SCRAM';
+                    $parameter = $hash;
+                    break;
+                }
                 return PEAR::raiseError('Invalid SASL mechanism type');
                 break;
         }
 
         require_once($filename);
-        $obj = new $classname();
+        if (isset($parameter))
+            $obj = new $classname($parameter);
+        else
+            $obj = new $classname();
         return $obj;
     }
 }
diff --git a/Auth/SASL/Common.php b/Auth/SASL/Common.php
index e7a18e2..e0fcb51 100755
--- a/Auth/SASL/Common.php
+++ b/Auth/SASL/Common.php
@@ -46,13 +46,14 @@
 class Auth_SASL_Common
 {
     /**
-    * Function which implements HMAC MD5 digest
+    * Function which implements HMAC-MD5 digest
     *
     * @param  string $key  The secret key
-    * @param  string $data The data to protect
-    * @return string       The HMAC MD5 digest
+    * @param  string $data The data to hash
+    * @param  bool $raw_output Whether the digest is returned in binary or hexadecimal format.
+    * @return string       The HMAC-MD5 digest
     */
-    function _HMAC_MD5($key, $data)
+    function _HMAC_MD5($key, $data, $raw_output = FALSE)
     {
         if (strlen($key) > 64) {
             $key = pack('H32', md5($key));
@@ -66,7 +67,36 @@ class Auth_SASL_Common
         $k_opad = substr($key, 0, 64) ^ str_repeat(chr(0x5C), 64);
 
         $inner  = pack('H32', md5($k_ipad . $data));
-        $digest = md5($k_opad . $inner);
+        $digest = md5($k_opad . $inner, $raw_output);
+
+        return $digest;
+    }
+
+    /**
+    * Function which implements HMAC-SHA-1 digest
+    *
+    * @param  string $key  The secret key
+    * @param  string $data The data to hash
+    * @param  bool $raw_output Whether the digest is returned in binary or hexadecimal format.
+    * @return string       The HMAC-SHA-1 digest
+    * @author Jehan <[email protected]>
+    * @access protected
+    */
+    protected function _HMAC_SHA1($key, $data, $raw_output = FALSE)
+    {
+        if (strlen($key) > 64) {
+            $key = sha1($key, TRUE);
+        }
+
+        if (strlen($key) < 64) {
+            $key = str_pad($key, 64, chr(0));
+        }
+
+        $k_ipad = substr($key, 0, 64) ^ str_repeat(chr(0x36), 64);
+        $k_opad = substr($key, 0, 64) ^ str_repeat(chr(0x5C), 64);
+
+        $inner  = pack('H40', sha1($k_ipad . $data));
+        $digest = sha1($k_opad . $inner, $raw_output);
 
         return $digest;
     }
diff --git a/Auth/SASL/SCRAM.php b/Auth/SASL/SCRAM.php
new file mode 100755
index 0000000..f4a1503
--- /dev/null
+++ b/Auth/SASL/SCRAM.php
@@ -0,0 +1,306 @@
+<?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 <[email protected]                             | 
+// +-----------------------------------------------------------------------+ 
+// 
+// $Id$
+
+/**
+* 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 <[email protected]>
+* @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 <[email protected]>
+    */
+    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);
+        }
+    }
+
+}
+
+?>
-- 
1.7.3.4