Add checks of index operations on string classes

Specifically the index parameter passed in to GetAt(), SetAt() and
operator[] are now being tested to be in bounds.

BUG=chromium:752480, pdfium:828

Change-Id: I9e94d58c98a8eaaaae53cd0e3ffe2123ea17d8c4
Reviewed-on: https://pdfium-review.googlesource.com/10651
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

7 files changed, 155 insertions, 52 deletions

diff --git a/core/fxcrt/cfx_bytestring.cpp b/core/fxcrt/cfx_bytestring.cpp
index c29d24affd..0aba3be12a 100644
--- a/core/fxcrt/cfx_bytestring.cpp
+++ b/core/fxcrt/cfx_bytestring.cpp
@@ -694,14 +694,10 @@ FX_STRSIZE CFX_ByteString::Replace(const CFX_ByteStringC& pOld,
   return nCount;
 }
 
-void CFX_ByteString::SetAt(FX_STRSIZE nIndex, char ch) {
-  if (!m_pData) {
-    return;
-  }
-  ASSERT(nIndex >= 0);
-  ASSERT(nIndex < m_pData->m_nDataLength);
+void CFX_ByteString::SetAt(FX_STRSIZE index, char c) {
+  ASSERT(index >= 0 && index < GetLength());
   ReallocBeforeWrite(m_pData->m_nDataLength);
-  m_pData->m_String[nIndex] = ch;
+  m_pData->m_String[index] = c;
 }
 
 CFX_WideString CFX_ByteString::UTF8Decode() const {
diff --git a/core/fxcrt/cfx_bytestring.h b/core/fxcrt/cfx_bytestring.h
index cf688b4c88..df31751273 100644
--- a/core/fxcrt/cfx_bytestring.h
+++ b/core/fxcrt/cfx_bytestring.h
@@ -107,15 +107,14 @@ class CFX_ByteString {
   const CFX_ByteString& operator+=(const CFX_ByteString& str);
   const CFX_ByteString& operator+=(const CFX_ByteStringC& bstrc);
 
-  uint8_t GetAt(FX_STRSIZE nIndex) const {
-    return m_pData ? m_pData->m_String[nIndex] : 0;
+  uint8_t GetAt(FX_STRSIZE index) const {
+    ASSERT(index >= 0 && index < GetLength());
+    return m_pData->m_String[index];
   }
 
-  uint8_t operator[](FX_STRSIZE nIndex) const {
-    return m_pData ? m_pData->m_String[nIndex] : 0;
-  }
+  uint8_t operator[](FX_STRSIZE index) const { return GetAt(index); }
 
-  void SetAt(FX_STRSIZE nIndex, char ch);
+  void SetAt(FX_STRSIZE index, char c);
   FX_STRSIZE Insert(FX_STRSIZE index, char ch);
   FX_STRSIZE InsertAtFront(char ch) { return Insert(0, ch); }
   FX_STRSIZE InsertAtBack(char ch) { return Insert(GetLength(), ch); }
diff --git a/core/fxcrt/cfx_bytestring_unittest.cpp b/core/fxcrt/cfx_bytestring_unittest.cpp
index b79a765e20..680a37e342 100644
--- a/core/fxcrt/cfx_bytestring_unittest.cpp
+++ b/core/fxcrt/cfx_bytestring_unittest.cpp
@@ -11,13 +11,52 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/base/stl_util.h"
 
+TEST(fxcrt, ByteStringGetAt) {
+  CFX_ByteString short_string("a");
+  CFX_ByteString longer_string("abc");
+  CFX_ByteString embedded_nul_string("ab\0c", 4);
+
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(-1); }, ".*");
+#endif
+  EXPECT_EQ('a', short_string.GetAt(0));
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(1); }, ".*");
+#endif
+  EXPECT_EQ('c', longer_string.GetAt(2));
+  EXPECT_EQ('b', embedded_nul_string.GetAt(1));
+  EXPECT_EQ('\0', embedded_nul_string.GetAt(2));
+  EXPECT_EQ('c', embedded_nul_string.GetAt(3));
+}
+
 TEST(fxcrt, ByteStringOperatorSubscript) {
-  // CFX_ByteString includes the NUL terminator for non-empty strings.
   CFX_ByteString abc("abc");
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[-1]; }, ".*");
+#endif
   EXPECT_EQ('a', abc[0]);
   EXPECT_EQ('b', abc[1]);
   EXPECT_EQ('c', abc[2]);
-  EXPECT_EQ(0, abc[3]);
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[3]; }, ".*");
+#endif
+}
+
+TEST(fxcrt, ByteStringSetAt) {
+  // CFX_ByteString includes the NUL terminator for non-empty strings.
+  CFX_ByteString abc("abc");
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc.SetAt(-1, 'd'); }, ".*");
+#endif
+  abc.SetAt(0, 'd');
+  EXPECT_EQ("dbc", abc);
+  abc.SetAt(1, 'e');
+  EXPECT_EQ("dec", abc);
+  abc.SetAt(2, 'f');
+  EXPECT_EQ("def", abc);
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc.SetAt(3, 'g'); }, ".*");
+#endif
 }
 
 TEST(fxcrt, ByteStringOperatorLT) {
@@ -905,24 +944,35 @@ TEST(fxcrt, ByteStringCMid) {
 }
 
 TEST(fxcrt, ByteStringCGetAt) {
-  CFX_ByteString short_string("a");
-  CFX_ByteString longer_string("abc");
-  CFX_ByteString embedded_nul_string("ab\0c", 4);
-
-  EXPECT_EQ('a', short_string.GetAt(0));
-  EXPECT_EQ('c', longer_string.GetAt(2));
-  EXPECT_EQ('b', embedded_nul_string.GetAt(1));
-  EXPECT_EQ('\0', embedded_nul_string.GetAt(2));
-  EXPECT_EQ('c', embedded_nul_string.GetAt(3));
+  CFX_ByteStringC short_string("a");
+  CFX_ByteStringC longer_string("abc");
+  CFX_ByteStringC embedded_nul_string("ab\0c", 4);
+
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(-1); }, ".*");
+#endif
+  EXPECT_EQ('a', static_cast<char>(short_string.GetAt(0)));
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(1); }, ".*");
+#endif
+  EXPECT_EQ('c', static_cast<char>(longer_string.GetAt(2)));
+  EXPECT_EQ('b', static_cast<char>(embedded_nul_string.GetAt(1)));
+  EXPECT_EQ('\0', static_cast<char>(embedded_nul_string.GetAt(2)));
+  EXPECT_EQ('c', static_cast<char>(embedded_nul_string.GetAt(3)));
 }
 
 TEST(fxcrt, ByteStringCOperatorSubscript) {
   // CFX_ByteStringC includes the NUL terminator for non-empty strings.
   CFX_ByteStringC abc("abc");
-  EXPECT_EQ('a', abc[0]);
-  EXPECT_EQ('b', abc[1]);
-  EXPECT_EQ('c', abc[2]);
-  EXPECT_EQ(0, abc[3]);
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[-1]; }, ".*");
+#endif
+  EXPECT_EQ('a', static_cast<char>(abc[0]));
+  EXPECT_EQ('b', static_cast<char>(abc[1]));
+  EXPECT_EQ('c', static_cast<char>(abc[2]));
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[3]; }, ".*");
+#endif
 }
 
 TEST(fxcrt, ByteStringCOperatorLT) {
diff --git a/core/fxcrt/cfx_string_c_template.h b/core/fxcrt/cfx_string_c_template.h
index 6a95a05d45..bc0fe1e0a0 100644
--- a/core/fxcrt/cfx_string_c_template.h
+++ b/core/fxcrt/cfx_string_c_template.h
@@ -119,8 +119,13 @@ class CFX_StringCTemplate {
   FX_STRSIZE GetLength() const { return m_Length; }
   bool IsEmpty() const { return m_Length == 0; }
 
-  UnsignedType GetAt(FX_STRSIZE index) const { return m_Ptr.Get()[index]; }
+  UnsignedType GetAt(FX_STRSIZE index) const {
+    ASSERT(index >= 0 && index < GetLength());
+    return m_Ptr.Get()[index];
+  }
+
   CharType CharAt(FX_STRSIZE index) const {
+    ASSERT(index >= 0 && index < GetLength());
     return static_cast<CharType>(m_Ptr.Get()[index]);
   }
 
@@ -159,9 +164,7 @@ class CFX_StringCTemplate {
     return CFX_StringCTemplate(m_Ptr.Get() + m_Length - count, count);
   }
 
-  const UnsignedType& operator[](size_t index) const {
-    return m_Ptr.Get()[index];
-  }
+  UnsignedType operator[](FX_STRSIZE index) const { return GetAt(index); }
 
   bool operator<(const CFX_StringCTemplate& that) const {
     int result = FXSYS_cmp(reinterpret_cast<const CharType*>(m_Ptr.Get()),
diff --git a/core/fxcrt/cfx_widestring.cpp b/core/fxcrt/cfx_widestring.cpp
index a1fa7ec096..c2e1e4877d 100644
--- a/core/fxcrt/cfx_widestring.cpp
+++ b/core/fxcrt/cfx_widestring.cpp
@@ -841,14 +841,10 @@ FX_STRSIZE CFX_WideString::Replace(const CFX_WideStringC& pOld,
   return nCount;
 }
 
-void CFX_WideString::SetAt(FX_STRSIZE nIndex, wchar_t ch) {
-  if (!m_pData) {
-    return;
-  }
-  ASSERT(nIndex >= 0);
-  ASSERT(nIndex < m_pData->m_nDataLength);
+void CFX_WideString::SetAt(FX_STRSIZE index, wchar_t c) {
+  ASSERT(index >= 0 && index < GetLength());
   ReallocBeforeWrite(m_pData->m_nDataLength);
-  m_pData->m_String[nIndex] = ch;
+  m_pData->m_String[index] = c;
 }
 
 // static
diff --git a/core/fxcrt/cfx_widestring.h b/core/fxcrt/cfx_widestring.h
index ccb1e752f7..b49e898f32 100644
--- a/core/fxcrt/cfx_widestring.h
+++ b/core/fxcrt/cfx_widestring.h
@@ -101,15 +101,14 @@ class CFX_WideString {
 
   bool operator<(const CFX_WideString& str) const;
 
-  wchar_t GetAt(FX_STRSIZE nIndex) const {
-    return m_pData ? m_pData->m_String[nIndex] : 0;
+  wchar_t GetAt(FX_STRSIZE index) const {
+    ASSERT(index >= 0 && index < GetLength());
+    return m_pData->m_String[index];
   }
 
-  wchar_t operator[](FX_STRSIZE nIndex) const {
-    return m_pData ? m_pData->m_String[nIndex] : 0;
-  }
+  wchar_t operator[](FX_STRSIZE index) const { return GetAt(index); }
 
-  void SetAt(FX_STRSIZE nIndex, wchar_t ch);
+  void SetAt(FX_STRSIZE index, wchar_t c);
 
   int Compare(const wchar_t* str) const;
   int Compare(const CFX_WideString& str) const;
diff --git a/core/fxcrt/cfx_widestring_unittest.cpp b/core/fxcrt/cfx_widestring_unittest.cpp
index 6e7b63c5fa..a23763218d 100644
--- a/core/fxcrt/cfx_widestring_unittest.cpp
+++ b/core/fxcrt/cfx_widestring_unittest.cpp
@@ -10,13 +10,51 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 
+TEST(fxcrt, WideStringGetAt) {
+  CFX_WideString short_string(L"a");
+  CFX_WideString longer_string(L"abc");
+  CFX_WideString embedded_nul_string(L"ab\0c", 4);
+
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(-1); }, ".*");
+#endif
+  EXPECT_EQ(L'a', short_string.GetAt(0));
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(1); }, ".*");
+#endif
+  EXPECT_EQ(L'c', longer_string.GetAt(2));
+  EXPECT_EQ(L'b', embedded_nul_string.GetAt(1));
+  EXPECT_EQ(L'\0', embedded_nul_string.GetAt(2));
+  EXPECT_EQ(L'c', embedded_nul_string.GetAt(3));
+}
+
 TEST(fxcrt, WideStringOperatorSubscript) {
-  // CFX_WideString includes the NUL terminator for non-empty strings.
   CFX_WideString abc(L"abc");
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[-1]; }, ".*");
+#endif
   EXPECT_EQ(L'a', abc[0]);
   EXPECT_EQ(L'b', abc[1]);
   EXPECT_EQ(L'c', abc[2]);
-  EXPECT_EQ(L'\0', abc[3]);
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[4]; }, ".*");
+#endif
+}
+
+TEST(fxcrt, WideStringSetAt) {
+  CFX_WideString abc(L"abc");
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc.SetAt(-1, L'd'); }, ".*");
+#endif
+  abc.SetAt(0, L'd');
+  EXPECT_EQ(L"dbc", abc);
+  abc.SetAt(1, L'e');
+  EXPECT_EQ(L"dec", abc);
+  abc.SetAt(2, L'f');
+  EXPECT_EQ(L"def", abc);
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc.SetAt(3, L'g'); }, ".*");
+#endif
 }
 
 TEST(fxcrt, WideStringOperatorLT) {
@@ -742,13 +780,35 @@ TEST(fxcrt, WideStringCFromVector) {
   EXPECT_EQ(nullptr, cleared_string.raw_str());
 }
 
+TEST(fxcrt, WideStringCGetAt) {
+  CFX_WideStringC short_string(L"a");
+  CFX_WideStringC longer_string(L"abc");
+  CFX_WideStringC embedded_nul_string(L"ab\0c", 4);
+
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(-1); }, ".*");
+#endif
+  EXPECT_EQ(L'a', static_cast<wchar_t>(short_string.GetAt(0)));
+#ifndef NDEBUG
+  EXPECT_DEATH({ short_string.GetAt(1); }, ".*");
+#endif
+  EXPECT_EQ(L'c', static_cast<wchar_t>(longer_string.GetAt(2)));
+  EXPECT_EQ(L'b', static_cast<wchar_t>(embedded_nul_string.GetAt(1)));
+  EXPECT_EQ(L'\0', static_cast<wchar_t>(embedded_nul_string.GetAt(2)));
+  EXPECT_EQ(L'c', static_cast<wchar_t>(embedded_nul_string.GetAt(3)));
+}
+
 TEST(fxcrt, WideStringCOperatorSubscript) {
-  // CFX_WideStringC includes the NUL terminator for non-empty strings.
   CFX_WideStringC abc(L"abc");
-  EXPECT_EQ(L'a', abc.CharAt(0));
-  EXPECT_EQ(L'b', abc.CharAt(1));
-  EXPECT_EQ(L'c', abc.CharAt(2));
-  EXPECT_EQ(L'\0', abc.CharAt(3));
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[-1]; }, ".*");
+#endif
+  EXPECT_EQ(L'a', static_cast<wchar_t>(abc[0]));
+  EXPECT_EQ(L'b', static_cast<wchar_t>(abc[1]));
+  EXPECT_EQ(L'c', static_cast<wchar_t>(abc[2]));
+#ifndef NDEBUG
+  EXPECT_DEATH({ abc[4]; }, ".*");
+#endif
 }
 
 TEST(fxcrt, WideStringCOperatorLT) {