Fix infinite loops in CPDF_MeshStream.

BUG=chromium:690501

Change-Id: I74b09d90a8082554a67f737eb6adc3bff82ed93e
Reviewed-on: https://pdfium-review.googlesource.com/2889
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

3 files changed, 42 insertions, 10 deletions

diff --git a/core/fpdfapi/page/cpdf_meshstream.cpp b/core/fpdfapi/page/cpdf_meshstream.cpp
index 75069cab7f..24ef9b271e 100644
--- a/core/fpdfapi/page/cpdf_meshstream.cpp
+++ b/core/fpdfapi/page/cpdf_meshstream.cpp
@@ -154,6 +154,18 @@ bool CPDF_MeshStream::Load() {
   return true;
 }
 
+bool CPDF_MeshStream::CanReadFlag() const {
+  return m_BitStream.BitsRemaining() >= m_nFlagBits;
+}
+
+bool CPDF_MeshStream::CanReadCoords() const {
+  return m_BitStream.BitsRemaining() / 2 >= m_nCoordBits;
+}
+
+bool CPDF_MeshStream::CanReadColor() const {
+  return m_BitStream.BitsRemaining() / m_nComponentBits >= m_nComponents;
+}
+
 uint32_t CPDF_MeshStream::ReadFlag() {
   ASSERT(ShouldCheckBitsPerFlag(m_type));
   return m_BitStream.GetBits(m_nFlagBits) & 0x03;
@@ -209,26 +221,35 @@ std::tuple<FX_FLOAT, FX_FLOAT, FX_FLOAT> CPDF_MeshStream::ReadColor() {
   return std::tuple<FX_FLOAT, FX_FLOAT, FX_FLOAT>(r, g, b);
 }
 
-CPDF_MeshVertex CPDF_MeshStream::ReadVertex(const CFX_Matrix& pObject2Bitmap,
-                                            uint32_t* flag) {
+bool CPDF_MeshStream::ReadVertex(const CFX_Matrix& pObject2Bitmap,
+                                 CPDF_MeshVertex* vertex,
+                                 uint32_t* flag) {
+  if (!CanReadFlag())
+    return false;
   *flag = ReadFlag();
 
-  CPDF_MeshVertex vertex;
-  vertex.position = pObject2Bitmap.Transform(ReadCoords());
-  std::tie(vertex.r, vertex.g, vertex.b) = ReadColor();
-  m_BitStream.ByteAlign();
+  if (!CanReadCoords())
+    return false;
+  vertex->position = pObject2Bitmap.Transform(ReadCoords());
 
-  return vertex;
+  if (!CanReadColor())
+    return false;
+  std::tie(vertex->r, vertex->g, vertex->b) = ReadColor();
+  m_BitStream.ByteAlign();
+  return true;
 }
 
 bool CPDF_MeshStream::ReadVertexRow(const CFX_Matrix& pObject2Bitmap,
                                     int count,
                                     CPDF_MeshVertex* vertex) {
   for (int i = 0; i < count; i++) {
-    if (m_BitStream.IsEOF())
+    if (m_BitStream.IsEOF() || !CanReadCoords())
       return false;
 
     vertex[i].position = pObject2Bitmap.Transform(ReadCoords());
+    if (!CanReadColor())
+      return false;
+
     std::tie(vertex[i].r, vertex[i].g, vertex[i].b) = ReadColor();
     m_BitStream.ByteAlign();
   }
diff --git a/core/fpdfapi/page/cpdf_meshstream.h b/core/fpdfapi/page/cpdf_meshstream.h
index 24f1d66cfd..d40de4a013 100644
--- a/core/fpdfapi/page/cpdf_meshstream.h
+++ b/core/fpdfapi/page/cpdf_meshstream.h
@@ -42,11 +42,17 @@ class CPDF_MeshStream {
 
   bool Load();
 
+  bool CanReadFlag() const;
+  bool CanReadCoords() const;
+  bool CanReadColor() const;
+
   uint32_t ReadFlag();
   CFX_PointF ReadCoords();
   std::tuple<FX_FLOAT, FX_FLOAT, FX_FLOAT> ReadColor();
 
-  CPDF_MeshVertex ReadVertex(const CFX_Matrix& pObject2Bitmap, uint32_t* flag);
+  bool ReadVertex(const CFX_Matrix& pObject2Bitmap,
+                  CPDF_MeshVertex* vertex,
+                  uint32_t* flag);
   bool ReadVertexRow(const CFX_Matrix& pObject2Bitmap,
                      int count,
                      CPDF_MeshVertex* vertex);
diff --git a/core/fpdfapi/page/cpdf_streamcontentparser.cpp b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
index d8e1c1e15d..6211b6a4dd 100644
--- a/core/fpdfapi/page/cpdf_streamcontentparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
@@ -98,8 +98,11 @@ CFX_FloatRect GetShadingBBox(CPDF_ShadingPattern* pShading,
 
   while (!stream.BitStream()->IsEOF()) {
     uint32_t flag = 0;
-    if (type != kLatticeFormGouraudTriangleMeshShading)
+    if (type != kLatticeFormGouraudTriangleMeshShading) {
+      if (!stream.CanReadFlag())
+        break;
       flag = stream.ReadFlag();
+    }
 
     if (!bGouraud && flag) {
       point_count -= 4;
@@ -107,6 +110,8 @@ CFX_FloatRect GetShadingBBox(CPDF_ShadingPattern* pShading,
     }
 
     for (int i = 0; i < point_count; i++) {
+      if (!stream.CanReadCoords())
+        break;
       CFX_PointF origin = stream.ReadCoords();
       if (bStarted) {
         rect.UpdateRect(origin.x, origin.y);