Fix the potential integer overflow from "offset + size"

core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
  
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../../include/fpdfapi/fpdf_parser.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../../third_party/numerics/safe_math.h"
@@ skipping 2846 matching lines @@
                         if (key != "Parent") {
                             new_obj_array.Add(value);
                         }
                     }
                 }
                 break;
             case PDFOBJ_REFERENCE: {
                     CPDF_Reference *pRef = (CPDF_Reference*)pObj;
                     FX_DWORD dwNum = pRef->GetRefObjNum();
                     FX_FILESIZE offset;
-                    FX_DWORD size = GetObjectSize(pRef->GetRefObjNum(), offset);
-                    if (!size) {
+                    FX_DWORD original_size = GetObjectSize(dwNum, offset);
+                    base::CheckedNumeric<FX_DWORD> size = original_size;

[palmer, 2014/07/23 17:58:36]

I've already checked in this change
(https://codereview.chromium.org/390983007/).

[jun_fang, 2014/07/24 07:14:39]

Yes. I already merged your change into this fix by resolving the conflicting.

+
+                    if (size.ValueOrDefault(0) == 0 || offset < 0 || offset >= m_dwFileLen)
                         break;
-                    }
-                    size = (FX_DWORD)((FX_FILESIZE)(offset + size + 512) > m_dwFileLen ? m_dwFileLen - offset : size + 512);
-                    if (!m_pFileAvail->IsDataAvail(offset, size)) {
-                        pHints->AddSegment(offset, size);
+                    
+                    size += offset;
+                    size += 512;
+                    if (!size.IsValid())
+                        break;
+
+                    if (size.ValueOrDie() > m_dwFileLen)
+                        size = m_dwFileLen - offset; 
+                    else
+                        size = original_size + 512;
+
+                    if (!size.IsValid())
+                        break;
+
+                    if (!m_pFileAvail->IsDataAvail(offset, size.ValueOrDie())) {
+                        pHints->AddSegment(offset, size.ValueOrDie());
                         ret_array.Add(pObj);
                         count++;
                     } else if (!m_objnum_array.Find(dwNum)) {
                         m_objnum_array.AddObjNum(dwNum);
                         CPDF_Object *pReferred = m_pDocument->GetIndirectObject(pRef->GetRefObjNum(), NULL);
                         if (pReferred) {
                             new_obj_array.Add(pReferred);
                         }
                     }
                 }
@@ skipping 179 matching lines @@
     CPDF_Object *pRet = NULL;
     if (pExistInFile) {
         *pExistInFile = TRUE;
     }
     if (m_pDocument == NULL) {
         FX_FILESIZE offset = m_parser.GetObjectOffset(objnum);
         if (offset < 0) {
             *pExistInFile = FALSE;
             return NULL;
         }
-        FX_DWORD size = (FX_DWORD)m_parser.GetObjectSize(objnum);
-        size = (FX_DWORD)(((FX_FILESIZE)(offset + size + 512)) > m_dwFileLen ? m_dwFileLen - offset : size + 512);
-        if (!m_pFileAvail->IsDataAvail(offset, size)) {
-            pHints->AddSegment(offset, size);
+
+        FX_DWORD original_size = (FX_DWORD)m_parser.GetObjectSize(objnum);
+        base::CheckedNumeric<FX_DWORD> size = original_size;
+        if (size.ValueOrDefault(0) == 0 || offset < 0 || offset >= m_dwFileLen)
+            return NULL;
+  
+        size += offset;
+        size += 512;
+        if (!size.IsValid()) 
+            return NULL;
+
+        if (size.ValueOrDie() > m_dwFileLen)
+            size = m_dwFileLen - offset;
+        else
+            size = original_size + 512;
+
+        if (!size.IsValid())
+            return NULL;
+
+        if (!m_pFileAvail->IsDataAvail(offset, size.ValueOrDie())) {
+            pHints->AddSegment(offset, size.ValueOrDie());
             return NULL;
         }
         pRet = m_parser.ParseIndirectObject(NULL, objnum);
         if (!pRet && pExistInFile) {
             *pExistInFile = FALSE;
         }
         return pRet;
     }
     FX_FILESIZE offset = 0;
-    FX_DWORD size = GetObjectSize(objnum, offset);
-    size = (FX_DWORD)((FX_FILESIZE)(offset + size + 512) > m_dwFileLen ? m_dwFileLen - offset : size + 512);
-    if (!m_pFileAvail->IsDataAvail(offset, size)) {
-        pHints->AddSegment(offset, size);
+    FX_DWORD original_size = GetObjectSize(objnum, offset);
+    base::CheckedNumeric<FX_DWORD> size = original_size;

[palmer, 2014/07/23 17:58:36]

So, this same basic chunk is now repeated 3 times. It's time to separate it out
into its own utility function, if that's possible.

[jun_fang, 2014/07/24 07:14:39]

I will reconstruct this function to remove the redundant parts.

+    if (size.ValueOrDefault(0) == 0 || offset < 0 || offset >= m_dwFileLen)
+        return NULL;
+
+    size += offset;
+    size += 512;
+    if (!size.IsValid())
+        return NULL;
+
+    if (size.ValueOrDie() > m_dwFileLen)
+        size = m_dwFileLen - offset;
+    else
+        size = original_size + 512;
+
+    if (!size.IsValid())
+        return NULL;
+ 
+    if (!m_pFileAvail->IsDataAvail(offset, size.ValueOrDie())) {
+        pHints->AddSegment(offset, size.ValueOrDie());
         return NULL;
     }
     CPDF_Parser *pParser = (CPDF_Parser *)(m_pDocument->GetParser());
     pRet = pParser->ParseIndirectObject(NULL, objnum, NULL);
     if (!pRet && pExistInFile) {
         *pExistInFile = FALSE;
     }
     return pRet;
 }
 FX_BOOL CPDF_DataAvail::CheckInfo(IFX_DownloadHints* pHints)
@@ skipping 1284 matching lines @@
 {
     FX_INT32 iSize = m_childNode.GetSize();
     for (FX_INT32 i = 0; i < iSize; ++i) {
         CPDF_PageNode *pNode = (CPDF_PageNode*)m_childNode[i];
         if (pNode) {
             delete pNode;
         }
     }
     m_childNode.RemoveAll();
 }