2006-03-25 Olivier Jolly <olivier.jolly@pcedev.com>

    * java/net/URLClassLoader.java (FileURLLoader.getResource): Added test
    to validate all components of a resource path.
    (FileURLLoader.walkPathComponents): Helper which ensures that we are
    allowed to walk through every component of a resource path.

2 files changed, 74 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index e84908b2d..d8016d45a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2006-03-25  Olivier Jolly  <olivier.jolly@pcedev.com>
+
+    * java/net/URLClassLoader.java (FileURLLoader.getResource): Added test
+    to validate all components of a resource path.
+    (FileURLLoader.walkPathComponents): Helper which ensures that we are
+    allowed to walk through every component of a resource path.
+    
 2006-03-25  Michael Koch  <konqueror@gmx.de>
 
 	* NEWS: Added item for CLDR 1.3 update.
diff --git a/java/net/URLClassLoader.java b/java/net/URLClassLoader.java
index ffa73dda6..677a2275a 100644
--- a/java/net/URLClassLoader.java
+++ b/java/net/URLClassLoader.java
@@ -538,9 +538,14 @@ public class URLClassLoader extends SecureClassLoader
     {
       try 
  	{
- 	  File file = new File(dir, name).getCanonicalFile();
- 	  if (file.exists())
- 	    return new FileResource(this, file);
+          // Make sure that all components in name are valid by walking through
+          // them
+          File file = walkPathComponents(name);
+
+          if (file == null)
+            return null;
+
+          return new FileResource(this, file);
  	}
       catch (IOException e)
  	{
@@ -548,6 +553,65 @@ public class URLClassLoader extends SecureClassLoader
  	}
       return null;
     }
+
+    /**
+     * Walk all path tokens and check them for validity. At no moment, we are
+     * allowed to reach a directory located "above" the root directory, stored
+     * in "dir" property. We are also not allowed to enter a non existing
+     * directory or a non directory component (plain file, symbolic link, ...).
+     * An empty or null path is valid. Pathnames components are separated by
+     * <code>File.separatorChar</code>
+     * 
+     * @param resourceFileName the name to be checked for validity.
+     * @return the canonical file pointed by the resourceFileName or null if the
+     *         walking failed
+     * @throws IOException in case of issue when creating the canonical
+     *           resulting file
+     * @see File#separatorChar
+     */
+    private File walkPathComponents(String resourceFileName) throws IOException
+    {
+      StringTokenizer stringTokenizer = new StringTokenizer(resourceFileName, File.separator);
+      File currentFile = dir;
+      int tokenCount = stringTokenizer.countTokens();
+
+      for (int i = 0; i < tokenCount - 1; i++)
+        {
+          String currentToken = stringTokenizer.nextToken();
+          
+          // If we are at the root directory and trying to go up, the walking is
+          // finished with an error
+          if ("..".equals(currentToken) && currentFile.equals(dir))
+            return null;
+          
+          currentFile = new File(currentFile, currentToken);
+
+          // If the current file doesn't exist or is not a directory, the walking is
+          // finished with an error
+          if (! (currentFile.exists() && currentFile.isDirectory()))
+            return null;
+          
+        }
+      
+      // Treat the last token differently, if it exists, because it does not need
+      // to be a directory
+      if (tokenCount > 0)
+        {
+          String currentToken = stringTokenizer.nextToken();
+          
+          if ("..".equals(currentToken) && currentFile.equals(dir))
+            return null;
+          
+          currentFile = new File(currentFile, currentToken);
+
+          // If the current file doesn't exist, the walking is
+          // finished with an error
+          if (! currentFile.exists())
+            return null;
+      }
+      
+      return currentFile.getCanonicalFile();
+    }
   }
 
   static final class FileResource extends Resource