92 lines
2.6 KiB
PHP
92 lines
2.6 KiB
PHP
<?php
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/**
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* Some functions to help implement an external link filter for spam control.
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*
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* TODO: implement the filter. Currently these are just some functions to help
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* maintenance/cleanupSpam.php remove links to a single specified domain. The
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* next thing is to implement functions for checking a given page against a big
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* list of domains.
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*
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* Another cool thing to do would be a web interface for fast spam removal.
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*/
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class LinkFilter {
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/**
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* @static
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*/
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function matchEntry( $text, $filterEntry ) {
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$regex = LinkFilter::makeRegex( $filterEntry );
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return preg_match( $regex, $text );
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}
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/**
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* @static
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*/
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function makeRegex( $filterEntry ) {
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$regex = '!http://';
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if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
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$regex .= '([A-Za-z0-9.-]+\.|)';
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$filterEntry = substr( $filterEntry, 2 );
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}
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$regex .= preg_quote( $filterEntry, '!' ) . '!Si';
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return $regex;
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}
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/**
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* Make a string to go after an SQL LIKE, which will match the specified
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* string. There are several kinds of filter entry:
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* *.domain.com - Produces http://com.domain.%, matches domain.com
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* and www.domain.com
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* domain.com - Produces http://com.domain./%, matches domain.com
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* or domain.com/ but not www.domain.com
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* *.domain.com/x - Produces http://com.domain.%/x%, matches
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* www.domain.com/xy
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* domain.com/x - Produces http://com.domain./x%, matches
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* domain.com/xy but not www.domain.com/xy
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*
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* Asterisks in any other location are considered invalid.
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*
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* @static
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*/
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function makeLike( $filterEntry ) {
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if ( substr( $filterEntry, 0, 2 ) == '*.' ) {
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$subdomains = true;
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$filterEntry = substr( $filterEntry, 2 );
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if ( $filterEntry == '' ) {
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// We don't want to make a clause that will match everything,
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// that could be dangerous
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return false;
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}
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} else {
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$subdomains = false;
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}
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// No stray asterisks, that could cause confusion
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// It's not simple or efficient to handle it properly so we don't
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// handle it at all.
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if ( strpos( $filterEntry, '*' ) !== false ) {
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return false;
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}
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$slash = strpos( $filterEntry, '/' );
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if ( $slash !== false ) {
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$path = substr( $filterEntry, $slash );
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$host = substr( $filterEntry, 0, $slash );
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} else {
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$path = '/';
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$host = $filterEntry;
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}
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$host = strtolower( implode( '.', array_reverse( explode( '.', $host ) ) ) );
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if ( substr( $host, -1, 1 ) !== '.' ) {
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$host .= '.';
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}
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$like = "http://$host";
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if ( $subdomains ) {
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$like .= '%';
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}
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if ( !$subdomains || $path !== '/' ) {
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$like .= $path . '%';
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}
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return $like;
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}
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}
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?>
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