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          */
  36         const SUFFIX = '+\\';
  37
  38         /** @var string */
  39         private $secret = '';
  40
  41         /** @var string */
  42         private $salt = '';
  43
  44         /** @var bool */
  45         private $new = false;
  46
  47         /**
  48          * @param string $secret Token secret
  49          * @param string $salt Token salt
  50          * @param bool $new Whether the secret was newly-created
  51          */
  52         public function __construct( $secret, $salt, $new = false ) {
  53                 $this->secret = $secret;
  54                 $this->salt = $salt;
  55                 $this->new = $new;
  56         }
  57
  58         /**
  59          * Decode the timestamp from a token string
  60          *
  61          * Does not validate the token beyond the syntactic checks necessary to
  62          * be able to extract the timestamp.
  63          *
  64          * @param string $token
  65          * @return int|null
  66          */
  67         public static function getTimestamp( $token ) {
  68                 $suffixLen = strlen( self::SUFFIX );
  69                 $len = strlen( $token );
  70                 if ( $len <= 32 + $suffixLen ||
  71                         substr( $token, -$suffixLen ) !== self::SUFFIX ||
  72                         strspn( $token, '0123456789abcdef' ) + $suffixLen !== $len
  73                 ) {
  74                         return null;
  75                 }
  76
  77                 return hexdec( substr( $token, 32, -$suffixLen ) );
  78         }
  79
  80         /**
  81          * Get the string representation of the token at a timestamp
  82          * @param int $timestamp
  83          * @return string
  84          */
  85         protected function toStringAtTimestamp( $timestamp ) {
  86                 return hash_hmac( 'md5', $timestamp . $this->salt, $this->secret, false ) .
  87                         dechex( $timestamp ) .
  88                         self::SUFFIX;
  89         }
  90
  91         /**
  92          * Get the string representation of the token
  93          * @return string
  94          */
  95         public function toString() {
  96                 return $this->toStringAtTimestamp( wfTimestamp() );
  97         }
  98
  99         public function __toString() {
 100                 return $this->toString();
 101         }
 102
 103         /**
 104          * Test if the token-string matches this token
 105          * @param string $userToken
 106          * @param int|null $maxAge Return false if $userToken is older than this many seconds
 107          * @return bool
 108          */
 109         public function match( $userToken, $maxAge = null ) {
 110                 $timestamp = self::getTimestamp( $userToken );
 111                 if ( $timestamp === null ) {
 112                         return false;
 113                 }
 114                 if ( $maxAge !== null && $timestamp < wfTimestamp() - $maxAge ) {
 115                         // Expired token
 116                         return false;
 117                 }
 118
 119                 $sessionToken = $this->toStringAtTimestamp( $timestamp );
 120                 return hash_equals( $sessionToken, $userToken );
 121         }
 122
 123         /**
 124          * Indicate whether this token was just created
 125          * @return bool
 126          */
 127         public function wasNew() {
 128                 return $this->new;
 129         }
 130
 131 }