[XERCESC-2066] Exception handling mistake in DTDScanner

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1.0, 3.1.1, 3.1.2, 3.1.3
• Fix Version/s: 3.2.0, 3.1.4
• Component/s: Validating Parser (DTD)
• Assignee: Scott Cantor
• Reporter: Scott Cantor
• Created: 09/May/16 15:43
• Updated: 28/Aug/17 23:41
• Resolved: 21/Jun/17 22:32

Description

Index: src/xercesc/validators/DTD/DTDScanner.cpp
==========================================================The DTDScanner fails to account for the fact that peeking characters in the XMLReader class can raise an exception if an invalid character is encountered, and the exception crosses stack frames in an unsafe way that causes a higher level exception handler to access an already-freed object.

The proposed patch below traps the exception locally and records the parser error in the appropriate frame.

We should also review the code for other calls to the XMLReader methods that can throw.

--- src/xercesc/validators/DTD/DTDScanner.cpp	(revision 1741478)
+++ src/xercesc/validators/DTD/DTDScanner.cpp	(working copy)
@@ -2509,7 +2509,15 @@
         {
             while (true)
             {
-                const XMLCh nextCh = fReaderMgr->peekNextChar();
+                XMLCh nextCh;
+                
+                try {
+                    nextCh = fReaderMgr->peekNextChar();
+                }
+                catch (XMLException& ex) {
+                    fScanner->emitError(XMLErrs::XMLException_Fatal, ex.getCode(), ex.getMessage(), NULL, NULL);
+                    nextCh = chNull;
+                }
 
                 if (!nextCh)
                 {