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 use Stringable;
  27
  28 /**
  29  * Value object representing a CSRF token
  30  *
  31  * @ingroup Session
  32  * @since 1.27
  33  */
  34 class Token implements Stringable {
  35         /** CSRF token suffix. Plus and terminal backslash are included to stop
  36          * editing from certain broken proxies.
  37          */
  38         public const SUFFIX = '+\\';
  39
  40         /** @var string */
  41         private $secret;
  42
  43         /** @var string */
  44         private $salt;
  45
  46         /** @var bool */
  47         private $new;
  48
  49         /**
  50          * @param string $secret Token secret
  51          * @param string $salt Token salt
  52          * @param bool $new Whether the secret was newly-created
  53          */
  54         public function __construct( $secret, $salt, $new = false ) {
  55                 $this->secret = $secret;
  56                 $this->salt = $salt;
  57                 $this->new = $new;
  58         }
  59
  60         /**
  61          * Decode the timestamp from a token string
  62          *
  63          * Does not validate the token beyond the syntactic checks necessary to
  64          * be able to extract the timestamp.
  65          *
  66          * @param string $token
  67          * @return int|null
  68          */
  69         public static function getTimestamp( $token ) {
  70                 $suffixLen = strlen( self::SUFFIX );
  71                 $len = strlen( $token );
  72                 if ( $len <= 32 + $suffixLen ||
  73                         substr( $token, -$suffixLen ) !== self::SUFFIX ||
  74                         strspn( $token, '0123456789abcdef' ) + $suffixLen !== $len
  75                 ) {
  76                         return null;
  77                 }
  78
  79                 return hexdec( substr( $token, 32, -$suffixLen ) );
  80         }
  81
  82         /**
  83          * Get the string representation of the token at a timestamp
  84          * @param int $timestamp
  85          * @return string
  86          */
  87         protected function toStringAtTimestamp( $timestamp ) {
  88                 return hash_hmac( 'md5', $timestamp . $this->salt, $this->secret, false ) .
  89                         dechex( $timestamp ) .
  90                         self::SUFFIX;
  91         }
  92
  93         /**
  94          * Get the string representation of the token
  95          * @return string
  96          */
  97         public function toString() {
  98                 return $this->toStringAtTimestamp( (int)wfTimestamp( TS_UNIX ) );
  99         }
 100
 101         public function __toString() {
 102                 return $this->toString();
 103         }
 104
 105         /**
 106          * Test if the token-string matches this token
 107          * @param string|null $userToken
 108          * @param int|null $maxAge Return false if $userToken is older than this many seconds
 109          * @return bool
 110          */
 111         public function match( $userToken, $maxAge = null ) {
 112                 if ( !$userToken ) {
 113                         return false;
 114                 }
 115                 $timestamp = self::getTimestamp( $userToken );
 116                 if ( $timestamp === null ) {
 117                         return false;
 118                 }
 119                 if ( $maxAge !== null && $timestamp < (int)wfTimestamp( TS_UNIX ) - $maxAge ) {
 120                         // Expired token
 121                         return false;
 122                 }
 123
 124                 $sessionToken = $this->toStringAtTimestamp( $timestamp );
 125                 return hash_equals( $sessionToken, $userToken );
 126         }
 127
 128         /**
 129          * Indicate whether this token was just created
 130          * @return bool
 131          */
 132         public function wasNew() {
 133                 return $this->new;
 134         }
 135
 136 }