Recognize invalid surrogate characters. JM-1388

git-svn-id: http://svn.igniterealtime.org/svn/repos/openfire/branches/openfire_3_5_2@10508 b35dd754-fafc-0310-a699-88a17e54d16e

src/java/org/jivesoftware/openfire/nio/XMLLightweightParser.java

@@ -2,7 +2,7 @@
  * $Revision: $
  * $Date: $
  *
- * Copyright (C) 2008 Jive Software. All rights reserved.
+ * Copyright (C) 2005-2008 Jive Software. All rights reserved.
  *
  * This software is published under the terms of the GNU Public License (GPL),
  * a copy of which is included in this distribution, or a commercial license
@@ -168,6 +168,11 @@ class XMLLightweightParser {
         char[] buf = charBuffer.array();
         int readByte = charBuffer.remaining();
 
+        // Just return if nothing was read
+        if (readByte == 0) {
+            return;
+        }
+
         // Verify if the last received byte is an incomplete double byte character
         char lastChar = buf[readByte-1];
         if (lastChar >= 0xfff0) {
@@ -197,8 +202,26 @@ class XMLLightweightParser {
         }
         // Robot.
         char ch;
+        boolean isHighSurrogate = false;
         for (int i = 0; i < readByte; i++) {
             ch = buf[i];
+            if (isHighSurrogate) {
+                if (Character.isLowSurrogate(ch)) {
+                    // Everything is fine. Clean up traces for surrogates
+                    isHighSurrogate = false;
+                }
+                else {
+                    // Trigger error. Found high surrogate not followed by low surrogate
+                    throw new Exception("Found high surrogate not followed by low surrogate");
+                }
+            }
+            else if (Character.isHighSurrogate(ch)) {
+                isHighSurrogate = true;
+            }
+            else if (Character.isLowSurrogate(ch)) {
+                // Trigger error. Found low surrogate char without a preceding high surrogate
+                throw new Exception("Found low surrogate char without a preceding high surrogate");
+            }
             if (status == XMLLightweightParser.TAIL) {
                 // Looking for the close tag
                 if (depth < 1 && ch == head.charAt(tailCount)) {