includes/LinkFilter.php

   1 <?php
   2 /**
   3  * Functions to help implement an external link filter for spam control.
   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  */
  22
  23 /**
  24  * Some functions to help implement an external link filter for spam control.
  25  *
  26  * @todo implement the filter. Currently these are just some functions to help
  27  * maintenance/cleanupSpam.php remove links to a single specified domain. The
  28  * next thing is to implement functions for checking a given page against a big
  29  * list of domains.
  30  *
  31  * Another cool thing to do would be a web interface for fast spam removal.
  32  */
  33 class LinkFilter {
  34
  35         /**
  36          * Check whether $content contains a link to $filterEntry
  37          *
  38          * @param $content Content: content to check
  39          * @param string $filterEntry domainparts, see makeRegex() for more details
  40          * @return Integer: 0 if no match or 1 if there's at least one match
  41          */
  42         static function matchEntry( Content $content, $filterEntry ) {
  43                 if ( !( $content instanceof TextContent ) ) {
  44                         //TODO: handle other types of content too.
  45                         //      Maybe create ContentHandler::matchFilter( LinkFilter ).
  46                         //      Think about a common base class for LinkFilter and MagicWord.
  47                         return 0;
  48                 }
  49
  50                 $text = $content->getNativeData();
  51
  52                 $regex = LinkFilter::makeRegex( $filterEntry );
  53                 return preg_match( $regex, $text );
  54         }
  55
  56         /**
  57          * Builds a regex pattern for $filterEntry.
  58          *
  59          * @param string $filterEntry URL, if it begins with "*.", it'll be
  60          *        replaced to match any subdomain
  61          * @return String: regex pattern, for preg_match()
  62          */
  63         private static function makeRegex( $filterEntry ) {
  64                 $regex = '!http://';
  65                 if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
  66                         $regex .= '(?:[A-Za-z0-9.-]+\.|)';
  67                         $filterEntry = substr( $filterEntry, 2 );
  68                 }
  69                 $regex .= preg_quote( $filterEntry, '!' ) . '!Si';
  70                 return $regex;
  71         }
  72
  73         /**
  74          * Make an array to be used for calls to DatabaseBase::buildLike(), which
  75          * will match the specified string. There are several kinds of filter entry:
  76          *     *.domain.com    -  Produces http://com.domain.%, matches domain.com
  77          *                        and www.domain.com
  78          *     domain.com      -  Produces http://com.domain./%, matches domain.com
  79          *                        or domain.com/ but not www.domain.com
  80          *     *.domain.com/x  -  Produces http://com.domain.%/x%, matches
  81          *                        www.domain.com/xy
  82          *     domain.com/x    -  Produces http://com.domain./x%, matches
  83          *                        domain.com/xy but not www.domain.com/xy
  84          *
  85          * Asterisks in any other location are considered invalid.
  86          *
  87          * @param string $filterEntry domainparts
  88          * @param $prot        String: protocol
  89          * @return Array to be passed to DatabaseBase::buildLike() or false on error
  90          */
  91         public static function makeLikeArray( $filterEntry, $prot = 'http://' ) {
  92                 $db = wfGetDB( DB_MASTER );
  93                 if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
  94                         $subdomains = true;
  95                         $filterEntry = substr( $filterEntry, 2 );
  96                         if ( $filterEntry == '' ) {
  97                                 // We don't want to make a clause that will match everything,
  98                                 // that could be dangerous
  99                                 return false;
 100                         }
 101                 } else {
 102                         $subdomains = false;
 103                 }
 104                 // No stray asterisks, that could cause confusion
 105                 // It's not simple or efficient to handle it properly so we don't
 106                 // handle it at all.
 107                 if ( strpos( $filterEntry, '*' ) !== false ) {
 108                         return false;
 109                 }
 110                 $slash = strpos( $filterEntry, '/' );
 111                 if ( $slash !== false ) {
 112                         $path = substr( $filterEntry, $slash );
 113                         $host = substr( $filterEntry, 0, $slash );
 114                 } else {
 115                         $path = '/';
 116                         $host = $filterEntry;
 117                 }
 118                 // Reverse the labels in the hostname, convert to lower case
 119                 // For emails reverse domainpart only
 120                 if ( $prot == 'mailto:' && strpos( $host, '@' ) ) {
 121                         // complete email address
 122                         $mailparts = explode( '@', $host );
 123                         $domainpart = strtolower( implode( '.', array_reverse( explode( '.', $mailparts[1] ) ) ) );
 124                         $host = $domainpart . '@' . $mailparts[0];
 125                         $like = array( "$prot$host", $db->anyString() );
 126                 } elseif ( $prot == 'mailto:' ) {
 127                         // domainpart of email address only. do not add '.'
 128                         $host = strtolower( implode( '.', array_reverse( explode( '.', $host ) ) ) );
 129                         $like = array( "$prot$host", $db->anyString() );
 130                 } else {
 131                         $host = strtolower( implode( '.', array_reverse( explode( '.', $host ) ) ) );
 132                         if ( substr( $host, -1, 1 ) !== '.' ) {
 133                                 $host .= '.';
 134                         }
 135                         $like = array( "$prot$host" );
 136
 137                         if ( $subdomains ) {
 138                                 $like[] = $db->anyString();
 139                         }
 140                         if ( !$subdomains || $path !== '/' ) {
 141                                 $like[] = $path;
 142                                 $like[] = $db->anyString();
 143                         }
 144                 }
 145                 return $like;
 146         }
 147
 148         /**
 149          * Filters an array returned by makeLikeArray(), removing everything past first pattern placeholder.
 150          *
 151          * @param array $arr array to filter
 152          * @return array filtered array
 153          */
 154         public static function keepOneWildcard( $arr ) {
 155                 if ( !is_array( $arr ) ) {
 156                         return $arr;
 157                 }
 158
 159                 foreach ( $arr as $key => $value ) {
 160                         if ( $value instanceof LikeMatch ) {
 161                                 return array_slice( $arr, 0, $key + 1 );
 162                         }
 163                 }
 164
 165                 return $arr;
 166         }
 167 }