From 93181f9a20db7ac706bb9405750303db93762a5b Mon Sep 17 00:00:00 2001
From: Lei Zhang <thestig@chromium.org>
Date: Wed, 9 Dec 2015 20:15:18 -0800
Subject: Prevent infinite looping in CPDF_Parser::LoadAllCrossRefV5().

BUG=pdfium:298
R=weili@chromium.org

Review URL: https://codereview.chromium.org/1496703005 .
---
 .../src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp | 39 ++++++++++++++--------
 1 file changed, 26 insertions(+), 13 deletions(-)

(limited to 'core/src')

diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index f64ba0deb0..bc5d3edc2b 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -582,21 +582,29 @@ bool CPDF_Parser::LoadCrossRefV4(FX_FILESIZE pos,
     }
     m_Syntax.RestorePos(SavedPos + count * recordsize);
   }
-  return !streampos || LoadCrossRefV5(streampos, streampos, FALSE);
+  return !streampos || LoadCrossRefV5(&streampos, FALSE);
 }
 
 FX_BOOL CPDF_Parser::LoadAllCrossRefV5(FX_FILESIZE xrefpos) {
-  if (!LoadCrossRefV5(xrefpos, xrefpos, TRUE)) {
+  if (!LoadCrossRefV5(&xrefpos, TRUE)) {
     return FALSE;
   }
-  while (xrefpos)
-    if (!LoadCrossRefV5(xrefpos, xrefpos, FALSE)) {
+  std::set<FX_FILESIZE> seen_xrefpos;
+  while (xrefpos) {
+    seen_xrefpos.insert(xrefpos);
+    if (!LoadCrossRefV5(&xrefpos, FALSE)) {
+      return FALSE;
+    }
+    // Check for circular references.
+    if (seen_xrefpos.find(xrefpos) != seen_xrefpos.end()) {
       return FALSE;
     }
+  }
   m_ObjectStreamMap.InitHashTable(101, FALSE);
   m_bXRefStream = TRUE;
   return TRUE;
 }
+
 FX_BOOL CPDF_Parser::RebuildCrossRef() {
   m_CrossRef.RemoveAll();
   m_V5Type.RemoveAll();
@@ -975,10 +983,8 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
   return m_pTrailer && m_CrossRef.GetSize() > 0;
 }
 
-FX_BOOL CPDF_Parser::LoadCrossRefV5(FX_FILESIZE pos,
-                                    FX_FILESIZE& prev,
-                                    FX_BOOL bMainXRef) {
-  CPDF_Object* pObject = ParseIndirectObjectAt(m_pDocument, pos, 0, nullptr);
+FX_BOOL CPDF_Parser::LoadCrossRefV5(FX_FILESIZE* pos, FX_BOOL bMainXRef) {
+  CPDF_Object* pObject = ParseIndirectObjectAt(m_pDocument, *pos, 0, nullptr);
   if (!pObject)
     return FALSE;
 
@@ -997,7 +1003,7 @@ FX_BOOL CPDF_Parser::LoadCrossRefV5(FX_FILESIZE pos,
   if (!pStream)
     return FALSE;
 
-  prev = pStream->GetDict()->GetInteger(FX_BSTRC("Prev"));
+  *pos = pStream->GetDict()->GetInteger(FX_BSTRC("Prev"));
   int32_t size = pStream->GetDict()->GetInteger(FX_BSTRC("Size"));
   if (size < 0) {
     pStream->Release();
@@ -1563,7 +1569,7 @@ FX_DWORD CPDF_Parser::StartAsynParse(IFX_FileRead* pFileAccess,
   FX_BOOL bXRefRebuilt = FALSE;
   FX_BOOL bLoadV4 = FALSE;
   if (!(bLoadV4 = LoadCrossRefV4(dwFirstXRefOffset, 0, FALSE, FALSE)) &&
-      !LoadCrossRefV5(dwFirstXRefOffset, dwFirstXRefOffset, TRUE)) {
+      !LoadCrossRefV5(&dwFirstXRefOffset, TRUE)) {
     if (!RebuildCrossRef()) {
       return PDFPARSE_ERROR_FORMAT;
     }
@@ -1623,13 +1629,20 @@ FX_DWORD CPDF_Parser::StartAsynParse(IFX_FileRead* pFileAccess,
   return PDFPARSE_ERROR_SUCCESS;
 }
 FX_BOOL CPDF_Parser::LoadLinearizedAllCrossRefV5(FX_FILESIZE xrefpos) {
-  if (!LoadCrossRefV5(xrefpos, xrefpos, FALSE)) {
+  if (!LoadCrossRefV5(&xrefpos, FALSE)) {
     return FALSE;
   }
-  while (xrefpos)
-    if (!LoadCrossRefV5(xrefpos, xrefpos, FALSE)) {
+  std::set<FX_FILESIZE> seen_xrefpos;
+  while (xrefpos) {
+    seen_xrefpos.insert(xrefpos);
+    if (!LoadCrossRefV5(&xrefpos, FALSE)) {
+      return FALSE;
+    }
+    // Check for circular references.
+    if (seen_xrefpos.find(xrefpos) != seen_xrefpos.end()) {
       return FALSE;
     }
+  }
   m_ObjectStreamMap.InitHashTable(101, FALSE);
   m_bXRefStream = TRUE;
   return TRUE;
-- 
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