Fix out of bound access in CPDF_Parser::ParseIndirectObject().

This regressed in commit f6dafc9.

BUG=576915
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1582763002 .

2 files changed, 20 insertions, 3 deletions

diff --git a/core/include/fpdfapi/fpdf_parser.h b/core/include/fpdfapi/fpdf_parser.h
index 84eacf6bf5..fda4557119 100644
--- a/core/include/fpdfapi/fpdf_parser.h
+++ b/core/include/fpdfapi/fpdf_parser.h
@@ -475,6 +475,7 @@ class CPDF_Parser {
   void SetEncryptDictionary(CPDF_Dictionary* pDict);
 
   FX_FILESIZE GetObjectPositionOrZero(FX_DWORD objnum) const;
+  void ShrinkObjectMap(FX_DWORD size);
 
   CPDF_Document* m_pDocument;
 
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 641e1e18ff..73da3619bb 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -143,6 +143,22 @@ FX_FILESIZE CPDF_Parser::GetObjectPositionOrZero(FX_DWORD objnum) const {
   return it != m_ObjectInfo.end() ? it->second.pos : 0;
 }
 
+void CPDF_Parser::ShrinkObjectMap(FX_DWORD objnum) {
+  if (objnum == 0) {
+    m_ObjectInfo.clear();
+    return;
+  }
+
+  auto it = m_ObjectInfo.lower_bound(objnum);
+  while (it != m_ObjectInfo.end()) {
+    auto saved_it = it++;
+    m_ObjectInfo.erase(saved_it);
+  }
+
+  if (!pdfium::ContainsKey(m_ObjectInfo, objnum - 1))
+    m_ObjectInfo[objnum - 1].pos = 0;
+}
+
 void CPDF_Parser::CloseParser(FX_BOOL bReParse) {
   m_bVersionUpdated = FALSE;
   if (!bReParse) {
@@ -379,7 +395,7 @@ FX_BOOL CPDF_Parser::LoadAllCrossRefV4(FX_FILESIZE xrefpos) {
   if (xrefsize <= 0 || xrefsize > kMaxXRefSize) {
     return FALSE;
   }
-  m_ObjectInfo[0].pos = 0;
+  ShrinkObjectMap(xrefsize);
   m_V5Type.SetSize(xrefsize);
   CFX_FileSizeArray CrossRefList;
   CFX_FileSizeArray XRefStreamList;
@@ -1029,7 +1045,7 @@ FX_BOOL CPDF_Parser::LoadCrossRefV5(FX_FILESIZE* pos, FX_BOOL bMainXRef) {
   }
   if (bMainXRef) {
     m_pTrailer = ToDictionary(pStream->GetDict()->Clone());
-    m_ObjectInfo[0].pos = 0;
+    ShrinkObjectMap(size);
     if (m_V5Type.SetSize(size)) {
       FXSYS_memset(m_V5Type.GetData(), 0, size);
     }
@@ -1607,7 +1623,7 @@ FX_DWORD CPDF_Parser::StartAsynParse(IFX_FileRead* pFileAccess,
 
     int32_t xrefsize = GetDirectInteger(m_pTrailer, "Size");
     if (xrefsize > 0) {
-      m_ObjectInfo[0].pos = 0;
+      ShrinkObjectMap(xrefsize);
       m_V5Type.SetSize(xrefsize);
     }
   }