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          * @static
  16          */
  17         function matchEntry( $text, $filterEntry ) {
  18                 $regex = LinkFilter::makeRegex( $filterEntry );
  19                 return preg_match( $regex, $text );
  20         }
  21
  22         /**
  23          * @static
  24          */
  25         function makeRegex( $filterEntry ) {
  26                 $regex = '!http://';
  27                 if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
  28                         $regex .= '([A-Za-z0-9.-]+\.|)';
  29                         $filterEntry = substr( $filterEntry, 2 );
  30                 }
  31                 $regex .= preg_quote( $filterEntry, '!' ) . '!Si';
  32                 return $regex;
  33         }
  34
  35         /**
  36          * Make a string to go after an SQL LIKE, which will match the specified
  37          * string. There are several kinds of filter entry:
  38          *     *.domain.com    -  Produces http://com.domain.%, matches domain.com
  39          *                        and www.domain.com
  40          *     domain.com      -  Produces http://com.domain./%, matches domain.com
  41          *                        or domain.com/ but not www.domain.com
  42          *     *.domain.com/x  -  Produces http://com.domain.%/x%, matches
  43          *                        www.domain.com/xy
  44          *     domain.com/x    -  Produces http://com.domain./x%, matches
  45          *                        domain.com/xy but not www.domain.com/xy
  46          *
  47          * Asterisks in any other location are considered invalid.
  48          *
  49          * @static
  50          */
  51         function makeLike( $filterEntry ) {
  52                 if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
  53                         $subdomains = true;
  54                         $filterEntry = substr( $filterEntry, 2 );
  55                         if ( $filterEntry == '' ) {
  56                                 // We don't want to make a clause that will match everything,
  57                                 // that could be dangerous
  58                                 return false;
  59                         }
  60                 } else {
  61                         $subdomains = false;
  62                 }
  63                 // No stray asterisks, that could cause confusion
  64                 // It's not simple or efficient to handle it properly so we don't
  65                 // handle it at all.
  66                 if ( strpos( $filterEntry, '*' ) !== false ) {
  67                         return false;
  68                 }
  69                 $slash = strpos( $filterEntry, '/' );
  70                 if ( $slash !== false ) {
  71                         $path = substr( $filterEntry, $slash );
  72                         $host = substr( $filterEntry, 0, $slash );
  73                 } else {
  74                         $path = '/';
  75                         $host = $filterEntry;
  76                 }
  77                 $host = strtolower( implode( '.', array_reverse( explode( '.', $host ) ) ) );
  78                 if ( substr( $host, -1, 1 ) !== '.' ) {
  79                         $host .= '.';
  80                 }
  81                 $like = "http://$host";
  82
  83                 if ( $subdomains ) {
  84                         $like .= '%';
  85                 }
  86                 if ( !$subdomains || $path !== '/' ) {
  87                         $like .= $path . '%';
  88                 }
  89                 return $like;
  90         }
  91 }
  92 ?>