Fix two bugs in MakeAbsolute filter involving base URIs that have empty path.

The bugs are:
* Undefined $is_folder variable when path is empty, and
* Improper concatenation of host and path together.

Signed-off-by: Edward Z. Yang <edwardzyang@thewritingpot.com>

NEWS

@@ -22,6 +22,8 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
   use on hand-written HTML.
 ! Add error-cases for unsupported elements in MakeWellFormed. This enables
   the strategy to be used, standalone, on untrusted input.
+- Fix two bugs in %URI.MakeAbsolute; one involving empty paths in base URLs,
+  the other involving an undefined $is_folder error.
 . Strategy_MakeWellFormed now operates in-place, saving memory and allowing
   for more interesting filter-backtracking
 . New HTMLPurifier_Injector->rewind() functionality, allows injectors to rewind

library/HTMLPurifier/URIFilter/MakeAbsolute.php

@@ -51,10 +51,13 @@ class HTMLPurifier_URIFilter_MakeAbsolute extends HTMLPurifier_URIFilter
         }
         if ($uri->path === '') {
             $uri->path = $this->base->path;
-        }elseif ($uri->path[0] !== '/') {
+        } elseif ($uri->path[0] !== '/') {
             // relative path, needs more complicated processing
             $stack = explode('/', $uri->path);
             $new_stack = array_merge($this->basePathStack, $stack);
+            if ($new_stack[0] !== '' && !is_null($this->base->host)) {
+                array_unshift($new_stack, '');
+            }
             $new_stack = $this->_collapseStack($new_stack);
             $uri->path = implode('/', $new_stack);
         }
@@ -71,6 +74,7 @@ class HTMLPurifier_URIFilter_MakeAbsolute extends HTMLPurifier_URIFilter
      */
     private function _collapseStack($stack) {
         $result = array();
+        $is_folder = false;
         for ($i = 0; isset($stack[$i]); $i++) {
             $is_folder = false;
             // absorb an internally duplicated slash

tests/HTMLPurifier/URIFilter/MakeAbsoluteTest.php

@@ -114,6 +114,13 @@ class HTMLPurifier_URIFilter_MakeAbsoluteTest extends HTMLPurifier_URIFilterHarn
         $this->assertFiltering('javascript: window.location = \'http://www.example.com\';', false);
     }
     
+    // miscellaneous
+    
+    function testFilterDomainWithNoSlash() {
+        $this->setBase('http://example.com');
+        $this->assertFiltering('foo', 'http://example.com/foo');
+    }
+    
     // error case
     
     function testErrorNoBase() {