Add CPDF_{Array,Dictionary}Locker to catch illegal iteration patterns.

Move begin/end methods onto locker object which tracks whether
iterators are in existence.

Change-Id: Ia869f313fce48d10a0d0180d0cc083eed6ea1584
Reviewed-on: https://pdfium-review.googlesource.com/c/44070
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

3 files changed, 31 insertions, 26 deletions

diff --git a/core/fpdfapi/page/cpdf_allstates.cpp b/core/fpdfapi/page/cpdf_allstates.cpp
index 9af904cb5d..3e6692b223 100644
--- a/core/fpdfapi/page/cpdf_allstates.cpp
+++ b/core/fpdfapi/page/cpdf_allstates.cpp
@@ -39,7 +39,8 @@ void CPDF_AllStates::SetLineDash(CPDF_Array* pArray, float phase, float scale) {
 
 void CPDF_AllStates::ProcessExtGS(CPDF_Dictionary* pGS,
                                   CPDF_StreamContentParser* pParser) {
-  for (const auto& it : *pGS) {
+  CPDF_DictionaryLocker locker(pGS);
+  for (const auto& it : locker) {
     const ByteString& key_str = it.first;
     CPDF_Object* pElement = it.second.get();
     CPDF_Object* pObject = pElement ? pElement->GetDirect() : nullptr;
diff --git a/core/fpdfapi/page/cpdf_colorspace.cpp b/core/fpdfapi/page/cpdf_colorspace.cpp
index 2266dec9e8..bcfd42d72f 100644
--- a/core/fpdfapi/page/cpdf_colorspace.cpp
+++ b/core/fpdfapi/page/cpdf_colorspace.cpp
@@ -461,7 +461,8 @@ std::unique_ptr<CPDF_ColorSpace> CPDF_ColorSpace::Load(
     if (!pDict)
       return nullptr;
 
-    for (const auto& it : *pDict) {
+    CPDF_DictionaryLocker locker(pDict);
+    for (const auto& it : locker) {
       std::unique_ptr<CPDF_ColorSpace> pRet;
       CPDF_Object* pValue = it.second.get();
       if (ToName(pValue))
diff --git a/core/fpdfapi/page/cpdf_streamcontentparser.cpp b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
index 79fa3d2890..beba208739 100644
--- a/core/fpdfapi/page/cpdf_streamcontentparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
@@ -174,36 +174,39 @@ ByteStringView FindFullName(const AbbrPair* table,
 void ReplaceAbbr(CPDF_Object* pObj) {
   switch (pObj->GetType()) {
     case CPDF_Object::DICTIONARY: {
-      CPDF_Dictionary* pDict = pObj->AsDictionary();
       std::vector<AbbrReplacementOp> replacements;
-      for (const auto& it : *pDict) {
-        ByteString key = it.first;
-        CPDF_Object* value = it.second.get();
-        ByteStringView fullname = FindFullName(
-            InlineKeyAbbr, FX_ArraySize(InlineKeyAbbr), key.AsStringView());
-        if (!fullname.IsEmpty()) {
-          AbbrReplacementOp op;
-          op.is_replace_key = true;
-          op.key = std::move(key);
-          op.replacement = fullname;
-          replacements.push_back(op);
-          key = fullname;
-        }
-
-        if (value->IsName()) {
-          ByteString name = value->GetString();
-          fullname =
-              FindFullName(InlineValueAbbr, FX_ArraySize(InlineValueAbbr),
-                           name.AsStringView());
+      CPDF_Dictionary* pDict = pObj->AsDictionary();
+      {
+        CPDF_DictionaryLocker locker(pDict);
+        for (const auto& it : locker) {
+          ByteString key = it.first;
+          CPDF_Object* value = it.second.get();
+          ByteStringView fullname = FindFullName(
+              InlineKeyAbbr, FX_ArraySize(InlineKeyAbbr), key.AsStringView());
           if (!fullname.IsEmpty()) {
             AbbrReplacementOp op;
-            op.is_replace_key = false;
-            op.key = key;
+            op.is_replace_key = true;
+            op.key = std::move(key);
             op.replacement = fullname;
             replacements.push_back(op);
+            key = fullname;
+          }
+
+          if (value->IsName()) {
+            ByteString name = value->GetString();
+            fullname =
+                FindFullName(InlineValueAbbr, FX_ArraySize(InlineValueAbbr),
+                             name.AsStringView());
+            if (!fullname.IsEmpty()) {
+              AbbrReplacementOp op;
+              op.is_replace_key = false;
+              op.key = key;
+              op.replacement = fullname;
+              replacements.push_back(op);
+            }
+          } else {
+            ReplaceAbbr(value);
           }
-        } else {
-          ReplaceAbbr(value);
         }
       }
       for (const auto& op : replacements) {