includes/LinkFilter.php

   1 <?php
   2
   3 /**
   4  * Some functions to help implement an external link filter for spam control.
   5  *
   6  * @todo implement the filter. Currently these are just some functions to help
   7  * maintenance/cleanupSpam.php remove links to a single specified domain. The
   8  * next thing is to implement functions for checking a given page against a big
   9  * list of domains.
  10  *
  11  * Another cool thing to do would be a web interface for fast spam removal.
  12  */
  13 class LinkFilter {
  14
  15         /**
  16          * Check whether $text contains a link to $filterEntry
  17          *
  18          * @param $text String: text to check
  19          * @param $filterEntry String: domainparts, see makeRegex() for more details
  20          * @return Integer: 0 if no match or 1 if there's at least one match
  21          */
  22         static function matchEntry( $text, $filterEntry ) {
  23                 $regex = LinkFilter::makeRegex( $filterEntry );
  24                 return preg_match( $regex, $text );
  25         }
  26
  27         /**
  28          * Builds a regex pattern for $filterEntry.
  29          *
  30          * @param $filterEntry String: URL, if it begins with "*.", it'll be
  31          *        replaced to match any subdomain
  32          * @return String: regex pattern, for preg_match()
  33          */
  34         private static function makeRegex( $filterEntry ) {
  35                 $regex = '!http://';
  36                 if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
  37                         $regex .= '(?:[A-Za-z0-9.-]+\.|)';
  38                         $filterEntry = substr( $filterEntry, 2 );
  39                 }
  40                 $regex .= preg_quote( $filterEntry, '!' ) . '!Si';
  41                 return $regex;
  42         }
  43
  44         /**
  45          * Make an array to be used for calls to DatabaseBase::buildLike(), which
  46          * will match the specified string. There are several kinds of filter entry:
  47          *     *.domain.com    -  Produces http://com.domain.%, matches domain.com
  48          *                        and www.domain.com
  49          *     domain.com      -  Produces http://com.domain./%, matches domain.com
  50          *                        or domain.com/ but not www.domain.com
  51          *     *.domain.com/x  -  Produces http://com.domain.%/x%, matches
  52          *                        www.domain.com/xy
  53          *     domain.com/x    -  Produces http://com.domain./x%, matches
  54          *                        domain.com/xy but not www.domain.com/xy
  55          *
  56          * Asterisks in any other location are considered invalid.
  57          *
  58          * @param $filterEntry String: domainparts
  59          * @param $prot        String: protocol
  60          * @return Array to be passed to DatabaseBase::buildLike() or false on error
  61          */
  62          public static function makeLikeArray( $filterEntry , $prot = 'http://' ) {
  63                 $db = wfGetDB( DB_MASTER );
  64                 if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
  65                         $subdomains = true;
  66                         $filterEntry = substr( $filterEntry, 2 );
  67                         if ( $filterEntry == '' ) {
  68                                 // We don't want to make a clause that will match everything,
  69                                 // that could be dangerous
  70                                 return false;
  71                         }
  72                 } else {
  73                         $subdomains = false;
  74                 }
  75                 // No stray asterisks, that could cause confusion
  76                 // It's not simple or efficient to handle it properly so we don't
  77                 // handle it at all.
  78                 if ( strpos( $filterEntry, '*' ) !== false ) {
  79                         return false;
  80                 }
  81                 $slash = strpos( $filterEntry, '/' );
  82                 if ( $slash !== false ) {
  83                         $path = substr( $filterEntry, $slash );
  84                         $host = substr( $filterEntry, 0, $slash );
  85                 } else {
  86                         $path = '/';
  87                         $host = $filterEntry;
  88                 }
  89                 // Reverse the labels in the hostname, convert to lower case
  90                 // For emails reverse domainpart only
  91                 if ( $prot == 'mailto:' && strpos($host, '@') ) {
  92                         // complete email adress
  93                         $mailparts = explode( '@', $host );
  94                         $domainpart = strtolower( implode( '.', array_reverse( explode( '.', $mailparts[1] ) ) ) );
  95                         $host = $domainpart . '@' . $mailparts[0];
  96                         $like = array( "$prot$host", $db->anyString() );
  97                 } elseif ( $prot == 'mailto:' ) {
  98                         // domainpart of email adress only. do not add '.'
  99                         $host = strtolower( implode( '.', array_reverse( explode( '.', $host ) ) ) );
 100                         $like = array( "$prot$host", $db->anyString() );
 101                 } else {
 102                         $host = strtolower( implode( '.', array_reverse( explode( '.', $host ) ) ) );
 103                         if ( substr( $host, -1, 1 ) !== '.' ) {
 104                                 $host .= '.';
 105                         }
 106                         $like = array( "$prot$host" );
 107
 108                         if ( $subdomains ) {
 109                                 $like[] = $db->anyString();
 110                         }
 111                         if ( !$subdomains || $path !== '/' ) {
 112                                 $like[] = $path;
 113                                 $like[] = $db->anyString();
 114                         }
 115                 }
 116                 return $like;
 117         }
 118
 119         /**
 120          * Filters an array returned by makeLikeArray(), removing everything past first pattern placeholder.
 121          *
 122          * @param $arr array: array to filter
 123          * @return array filtered array
 124          */
 125         public static function keepOneWildcard( $arr ) {
 126                 if( !is_array( $arr ) ) {
 127                         return $arr;
 128                 }
 129
 130                 foreach( $arr as $key => $value ) {
 131                         if ( $value instanceof LikeMatch ) {
 132                                 return array_slice( $arr, 0, $key + 1 );
 133                         }
 134                 }
 135
 136                 return $arr;
 137         }
 138 }