Details
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Bug
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Status: Closed (View Workflow)
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Minor
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Resolution: Fixed
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3.0.7-PL1
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None
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PHP 5.3.1, MySQL 5.1.41, Opera 10.54 / Firefox 3.0.5
Description
Problem: If e.g. we have a posting text of 76524 characters which includes 359 pairs of [URL=..][IMG] tags and then is encapsulated in one [U] tag phpBB will fail to parse the [U] tag.
Reason: while processing the text each tag gets a UID appended, so the text grows - and at some point exceeds 100000 characters. After this point no more tags get parsed, since all preg_xxx() functions won't give any result (because internally PREG fails). Most PHP settings default to have a PREG backtrace limit of 100000 characters and phpBB never calls preg_last_error() to check for failures (note: failures, not regexp pattern errors).
Workaround: in "/includes/message_parser.php" function parse_bbcode()'s core goes like this:
foreach ($bbcode_data['regexp'] as $regexp => $replacement)
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{
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// The pattern gets compiled and cached by the PCRE extension,
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// it should not demand recompilation
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if (preg_match($regexp, $this->message))
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{
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$this->message = preg_replace($regexp, $replacement, $this->message);
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$bitfield->set($bbcode_data['bbcode_id']);
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}
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}
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To check for PREG failures we can already check preg_match() since this also fails once the text length exceeds the limit. If we only check for a backtrack limit failure we can try to increase the limit for a couple of times. How often and in which steps we increment the limit might be subject of another discussion:
foreach ($bbcode_data['regexp'] as $regexp => $replacement)
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{
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$iSet= 0; // How often did we set a new limit
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while( $iSet< 10 ) { // On default values like 100000 the highest new limit would be 250000
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// The pattern gets compiled and cached by the PCRE extension,
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// it should not demand recompilation
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if (preg_match($regexp, $this->message))
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{
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$this->message = preg_replace($regexp, $replacement, $this->message);
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$bitfield->set($bbcode_data['bbcode_id']);
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}
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if( preg_last_error()== PREG_BACKTRACK_LIMIT_ERROR ) { // Only check for backtrack limit failure
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ini_set( 'pcre.backtrack_limit', (int)ini_get( 'pcre.backtrack_limit' )+ 15000 ); // Get current limit and increase
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$iSet++; // Do not overkill the server
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} else break; // No fail, exit loop
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}
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}
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Attachments
Issue Links
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- Closed
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