Fix infinite loop in Lexer.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

NEWS

@@ -28,6 +28,7 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
   spaces and commas are not included as part of URL.  Thanks nAS for fixing.
 - Fix some bad interactions with %HTML.Allowed and injectors.  Thanks
   David Hirtz for reporting.
+- Fix infinite loop in DirectLex. Thanks Ashar Javed for reporting.
 
 4.5.0, released 2013-02-17
 # Fix bug where stacked attribute transforms clobber each other;

library/HTMLPurifier/Lexer/DirectLex.php

@@ -441,11 +441,12 @@ class HTMLPurifier_Lexer_DirectLex extends HTMLPurifier_Lexer
         // space, so let's guarantee that there's always a terminating space.
         $string .= ' ';
 
-        while (true) {
-
-            if ($cursor >= $size) {
-                break;
+        $old_cursor = -1;
+        while ($cursor < $size) {
+            if ($old_cursor >= $cursor) {
+                throw new Exception("Infinite loop detected");
             }
+            $old_cursor = $cursor;
 
             $cursor += ($value = strspn($string, $this->_whitespace, $cursor));
             // grab the key
@@ -463,7 +464,7 @@ class HTMLPurifier_Lexer_DirectLex extends HTMLPurifier_Lexer
                 if ($e) {
                     $e->send(E_ERROR, 'Lexer: Missing attribute key');
                 }
-                $cursor += strcspn($string, $this->_whitespace, $cursor + 1); // prevent infinite loop
+                $cursor += 1 + strcspn($string, $this->_whitespace, $cursor + 1); // prevent infinite loop
                 continue; // empty key
             }
 

tests/HTMLPurifier/HTMLT/style-onload.htmlt

@@ -0,0 +1,6 @@
+--INI--
+Core.CollectErrors = true
+--HTML--
+<style/onload    =    !-alert&#x28;1&#x29;>
+--EXPECT--
+--# vim: et sw=4 sts=4

tests/HTMLPurifier/Lexer/DirectLexTest.php

@@ -56,7 +56,7 @@ class HTMLPurifier_Lexer_DirectLexTest extends HTMLPurifier_Harness
         $expect[11] = array();
 
         $input[12] = '="" =""';
-        $expect[12] = array('"' => ''); // tough to say, just don't throw a loop
+        $expect[12] = array(); // tough to say, just don't throw a loop
 
         $input[13] = 'href="';
         $expect[13] = array('href' => '');