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         /** @var string */
  38         private $secret = '';
  39
  40         /** @var string */
  41         private $salt = '';
  42
  43         /** @var bool */
  44         private $new = false;
  45
  46         /**
  47          * @param string $secret Token secret
  48          * @param string $salt Token salt
  49          * @param bool $new Whether the secret was newly-created
  50          */
  51         public function __construct( $secret, $salt, $new = false ) {
  52                 $this->secret = $secret;
  53                 $this->salt = $salt;
  54                 $this->new = $new;
  55         }
  56
  57         /**
  58          * Decode the timestamp from a token string
  59          *
  60          * Does not validate the token beyond the syntactic checks necessary to
  61          * be able to extract the timestamp.
  62          *
  63          * @param string $token
  64          * @return int|null
  65          */
  66         public static function getTimestamp( $token ) {
  67                 $suffixLen = strlen( self::SUFFIX );
  68                 $len = strlen( $token );
  69                 if ( $len <= 32 + $suffixLen ||
  70                         substr( $token, -$suffixLen ) !== self::SUFFIX ||
  71                         strspn( $token, '0123456789abcdef' ) + $suffixLen !== $len
  72                 ) {
  73                         return null;
  74                 }
  75
  76                 return hexdec( substr( $token, 32, -$suffixLen ) );
  77         }
  78
  79         /**
  80          * Get the string representation of the token at a timestamp
  81          * @param int $timestamp
  82          * @return string
  83          */
  84         protected function toStringAtTimestamp( $timestamp ) {
  85                 return hash_hmac( 'md5', $timestamp . $this->salt, $this->secret, false ) .
  86                         dechex( $timestamp ) .
  87                         self::SUFFIX;
  88         }
  89
  90         /**
  91          * Get the string representation of the token
  92          * @return string
  93          */
  94         public function toString() {
  95                 return $this->toStringAtTimestamp( wfTimestamp() );
  96         }
  97
  98         public function __toString() {
  99                 return $this->toString();
 100         }
 101
 102         /**
 103          * Test if the token-string matches this token
 104          * @param string $userToken
 105          * @param int|null $maxAge Return false if $userToken is older than this many seconds
 106          * @return bool
 107          */
 108         public function match( $userToken, $maxAge = null ) {
 109                 $timestamp = self::getTimestamp( $userToken );
 110                 if ( $timestamp === null ) {
 111                         return false;
 112                 }
 113                 if ( $maxAge !== null && $timestamp < wfTimestamp() - $maxAge ) {
 114                         // Expired token
 115                         return false;
 116                 }
 117
 118                 $sessionToken = $this->toStringAtTimestamp( $timestamp );
 119                 return hash_equals( $sessionToken, $userToken );
 120         }
 121
 122         /**
 123          * Indicate whether this token was just created
 124          * @return bool
 125          */
 126         public function wasNew() {
 127                 return $this->new;
 128         }
 129
 130 }