includes/session/Token.php

   1 <?php
   2 /**
   3  * MediaWiki session token
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Session
  22  */
  23
  24 namespace MediaWiki\Session;
  25
  26 /**
  27  * Value object representing a CSRF token
  28  *
  29  * @ingroup Session
  30  * @since 1.27
  31  */
  32 class Token {
  33         /** CSRF token suffix. Plus and terminal backslash are included to stop
  34          * editing from certain broken proxies. */
  35         const SUFFIX = '+\\';
  36
  37         private $secret = '';
  38         private $salt = '';
  39         private $new = false;
  40
  41         /**
  42          * @param string $secret Token secret
  43          * @param string $salt Token salt
  44          * @param bool $new Whether the secret was newly-created
  45          */
  46         public function __construct( $secret, $salt, $new = false ) {
  47                 $this->secret = $secret;
  48                 $this->salt = $salt;
  49                 $this->new = $new;
  50         }
  51
  52         /**
  53          * Decode the timestamp from a token string
  54          *
  55          * Does not validate the token beyond the syntactic checks necessary to
  56          * be able to extract the timestamp.
  57          *
  58          * @param string $token
  59          * @return int|null
  60          */
  61         public static function getTimestamp( $token ) {
  62                 $suffixLen = strlen( self::SUFFIX );
  63                 $len = strlen( $token );
  64                 if ( $len <= 32 + $suffixLen ||
  65                         substr( $token, -$suffixLen ) !== self::SUFFIX ||
  66                         strspn( $token, '0123456789abcdef' ) + $suffixLen !== $len
  67                 ) {
  68                         return null;
  69                 }
  70
  71                 return hexdec( substr( $token, 32, -$suffixLen ) );
  72         }
  73
  74         /**
  75          * Get the string representation of the token at a timestamp
  76          * @param int $timestamp
  77          * @return string
  78          */
  79         protected function toStringAtTimestamp( $timestamp ) {
  80                 return hash_hmac( 'md5', $timestamp . $this->salt, $this->secret, false ) .
  81                         dechex( $timestamp ) .
  82                         self::SUFFIX;
  83         }
  84
  85         /**
  86          * Get the string representation of the token
  87          * @return string
  88          */
  89         public function toString() {
  90                 return $this->toStringAtTimestamp( wfTimestamp() );
  91         }
  92
  93         public function __toString() {
  94                 return $this->toString();
  95         }
  96
  97         /**
  98          * Test if the token-string matches this token
  99          * @param string $userToken
 100          * @param int|null $maxAge Return false if $userToken is older than this many seconds
 101          * @return bool
 102          */
 103         public function match( $userToken, $maxAge = null ) {
 104                 $timestamp = self::getTimestamp( $userToken );
 105                 if ( $timestamp === null ) {
 106                         return false;
 107                 }
 108                 if ( $maxAge !== null && $timestamp < wfTimestamp() - $maxAge ) {
 109                         // Expired token
 110                         return false;
 111                 }
 112
 113                 $sessionToken = $this->toStringAtTimestamp( $timestamp );
 114                 return hash_equals( $sessionToken, $userToken );
 115         }
 116
 117         /**
 118          * Indicate whether this token was just created
 119          * @return bool
 120          */
 121         public function wasNew() {
 122                 return $this->new;
 123         }
 124
 125 }