WordPress must not use preg_replace with /e

[BenBE]

When a server runs the Suhosin Patch one option allows web administrators to enable certain security-related functionality like disabling remote URL inclusion or disabling certain functions like eval with much better granularity. One of this options you can choose from is to disable the /e modifier of the preg_replace command as this modifier allows for arbitary code to get executed.

If this option is enabled parts of WordPress stop working. So you either can patch all those locations by hand every time you need to update your WordPress blog or stop using WordPress or kindly ask the developers to cease using preg_replace with /e modifier and instead switch to using preg_replace_callback which in return provides you with much more flexibility.

Affected locations in WordPress 2.7 (DE version) are:

File wordpress\wp-admin\import\blogger.php
     553  		$post_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $post_content);
     606  		$comment_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $comment_content);
File wordpress\wp-admin\import\blogware.php
      92  			$post_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $post_content);
     132  					$comment_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $comment_content);
File wordpress\wp-admin\import\livejournal.php
      73  			$post_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $post_content);
     109  					$comment_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $comment_content);
File wordpress\wp-admin\import\rss.php
     106  			$post_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $post_content);
File wordpress\wp-admin\import\wordpress.php
     384  		$post_excerpt = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $post_excerpt);
     389  		$post_content = preg_replace('|<(/?[A-Z]+)|e', "'<' . strtolower('$1')", $post_content);
File wordpress\wp-content\plugins\ajaxd-wordpress\control\aWP-admin.php
      55  			$options = preg_replace('!s:(\d+):"(.*?)";!e', "'s:'.strlen('$2').':\"$2\";'", $options );
File wordpress\wp-includes\class-phpmailer.php
    1423          $encoded = preg_replace('/([\000-\011\013\014\016-\037\075\077\137\177-\377])/e',
File wordpress\wp-includes\formatting.php
    1151  		$subject = preg_replace('#\=([0-9a-f]{2})#ei', "chr(hexdec(strtolower('$1')))", $subject);
File wordpress\wp-includes\kses.php
     397  	return preg_replace('%((<!--.*?(-->|$))|(<[^>]*(>|$)|>))%e',
    1002  	$string = preg_replace('/&#([0-9]+);/e', 'chr("\\1")', $string);
    1003  	$string = preg_replace('/&#[Xx]([0-9A-Fa-f]+);/e', 'chr(hexdec("\\1"))', $string);
File wordpress\wp-includes\post-template.php
     226  		$output =	preg_replace('/\%u([0-9A-F]{4,4})/e',	"'&#'.base_convert('\\1',16,10).';'", $output);
File wordpress\wp-includes\js\tinymce\plugins\spellchecker\classes\GoogleSpell.php
     109  		$string = preg_replace('~&#x([0-9a-f]+);~ei', 'chr(hexdec("\\1"))', $string);
     110  		$string = preg_replace('~&#([0-9]+);~e', 'chr(\\1)', $string);

In order to quickly find the places where such a call is present, you can use the following regular expression:

/preg_replace\s*\(\s*'(.).+?\1[^']*?e[^']*'/

Two affected are external libraries, which needs to have the defect reported upstream.

1. wordpress\wp-includes\js\tinymce\plugins\spellchecker\classes\GoogleSpell.php
2. wordpress\wp-includes\class-phpmailer.php

One is a plugin, which again needs to be reported at the plugin trac.

The instances in kses, should already be fixed, but it can be looked at again.

The others do need to be corrected.

I thought we tried to banish preg_replaces with eval before...

Seems we missed some.

The attached patch fixes all the occurrences of preg_replace identified in this ticket that are part of the the WP core (doesn't cover external libraries).

(In [10339]) Use preg_replace_callback instead of preg_replace with eval. Props beaulebens. see #8689

(In [10392]) Use preg_replace_callback instead of preg_replace with eval. Props beaulebens. see #8689 for 2.7

/e is still around in 2.8/trunk:

• funky_javascript_fix()
• PHPMailer::EncodeQP()

Here's a patch for the last two reported by Denis-de-Bernardy.

-- tbaboon

tiny suggestion: write the actual functions, or store the lambda function's name. else, using them repeatedly will create unneeded functions and gobble up memory.

OK, here's a second version of the patch.

As an aside, there are a bunch of other similar create_function() problems in the code base already, so you may want to open a separate bug for that (in case there isn't one already).

-- tbaboon

(In [11098]) Eliminate preg_replace with /e. Props tbaboon. fixes #8689

thanks!

WordPress 2.8.4 violates this again in /wp-admin/includes/post.php around line 6800 in function _fix_attachment_links().

Replying to BenBE1987:

WordPress 2.8.4 violates this again in /wp-admin/includes/post.php around line 6800 in function _fix_attachment_links().

Please don't re-open tickets fixed in old releases but instead create a new ticket for the issue.

I have created #10896 to track this issue - patches welcome.