From 854397b216463d77561b8adadf880c3fbbcb8885 Mon Sep 17 00:00:00 2001
From: thomascube <thomas@roundcube.net>
Date: Fri, 09 Dec 2011 20:33:58 -0500
Subject: [PATCH] Better CSS url() validation
---
program/include/main.inc | 26 ++++++++++++++++++++------
1 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/program/include/main.inc b/program/include/main.inc
index 2d18567..372e966 100644
--- a/program/include/main.inc
+++ b/program/include/main.inc
@@ -891,15 +891,29 @@
// ignore the whole block if evil styles are detected
$source = rcmail_xss_entity_decode($source);
$stripped = preg_replace('/[^a-z\(:;]/i', '', $source);
- $evilexpr = 'expression|behavior' . (!$allow_remote ? '|url\(|import[^a]' : '');
- if (preg_match("/$evilexpr/i", $stripped) // don't accept No-Gos
- || (strpos($stripped, 'url(') && !preg_match('!url\s*\([ "\'](https?:)//[a-z0-9/._+-]+["\' ]\)!Ui', $source))) // only allow clean urls
+ $evilexpr = 'expression|behavior|javascript:|import[^a]' . (!$allow_remote ? '|url\(' : '');
+ if (preg_match("/$evilexpr/i", $stripped))
return '/* evil! */';
// cut out all contents between { and }
- while (($pos = strpos($source, '{', $last_pos)) && ($pos2 = strpos($source, '}', $pos)))
- {
- $key = $replacements->add(substr($source, $pos+1, $pos2-($pos+1)));
+ while (($pos = strpos($source, '{', $last_pos)) && ($pos2 = strpos($source, '}', $pos))) {
+ $styles = substr($source, $pos+1, $pos2-($pos+1));
+
+ // check every line of a style block...
+ if ($allow_remote) {
+ $a_styles = preg_split('/;[\r\n]*/', $styles, -1, PREG_SPLIT_NO_EMPTY);
+ foreach ($a_styles as $line) {
+ $stripped = preg_replace('/[^a-z\(:;]/i', '', $line);
+ // ... and only allow strict url() values
+ if (stripos($stripped, 'url(') && !preg_match('!url\s*\([ "\'](https?:)//[a-z0-9/._+-]+["\' ]\)!Uims', $line)) {
+ $a_styles = array('/* evil! */');
+ break;
+ }
+ }
+ $styles = join(";\n", $a_styles);
+ }
+
+ $key = $replacements->add($styles);
$source = substr($source, 0, $pos+1) . $replacements->get_replacement($key) . substr($source, $pos2, strlen($source)-$pos2);
$last_pos = $pos+2;
}
--
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