Add a fuzzer for CPDF_HintTables.

testing/libfuzzer/pdf_hint_table_fuzzer.cc

Index: testing/libfuzzer/pdf_hint_table_fuzzer.cc
diff --git a/testing/libfuzzer/pdf_hint_table_fuzzer.cc b/testing/libfuzzer/pdf_hint_table_fuzzer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d14d9464f54f8b539c9bfbd078629a96a5819d2e
--- /dev/null
+++ b/testing/libfuzzer/pdf_hint_table_fuzzer.cc
@@ -0,0 +1,94 @@
+// Copyright 2016 The PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <cstdint>
+
+#include "core/fpdfapi/fpdf_parser/cpdf_hint_tables.h"
+#include "core/fpdfapi/fpdf_parser/include/cpdf_dictionary.h"
+
+struct DummyLinearizedDictionary {
+  int end_of_first_page_offset;
+  int number_of_pages;
+  int first_page_object_number;
+  int first_page_number;
+  int primary_hint_stream_offset;
+  int primary_hint_stream_length;
+  int shared_hint_table_offset;
+};
+
+int32_t GetData(const int32_t** data32, const uint8_t** data, size_t* size) {
+  const int32_t* ret = *data32;
+  ++(*data32);
+  *data += 4;
+  *size -= 4;
+  return *ret;
+}
+
+class HintTableForFuzzing : public CPDF_HintTables {
+ public:
+  HintTableForFuzzing(DummyLinearizedDictionary* dict,
+                      CPDF_Dictionary* linearized_dict)
+      : CPDF_HintTables(nullptr, linearized_dict), dict_(dict) {}
+  ~HintTableForFuzzing() {}
+
+  void Fuzz(const uint8_t* data, size_t size) {
+    if (dict_->shared_hint_table_offset <= 0)
+      return;
+
+    if (size < static_cast<size_t>(dict_->shared_hint_table_offset))
+      return;
+
+    CFX_BitStream bs;
+    bs.Init(data, size);
+    if (!ReadPageHintTable(&bs))
+      return;
+    ReadSharedObjHintTable(&bs, dict_->shared_hint_table_offset);
+  }
+
+ private:
+  int GetEndOfFirstPageOffset() const override {
+    return dict_->end_of_first_page_offset;
+  }
+  int GetNumberOfPages() const override { return dict_->number_of_pages; }
+  int GetFirstPageObjectNumber() const override {
+    return dict_->first_page_object_number;
+  }
+  int GetFirstPageNumber() const override { return dict_->first_page_number; }
+  int ReadPrimaryHintStreamOffset() const override {
+    return dict_->primary_hint_stream_offset;
+  }
+  int ReadPrimaryHintStreamLength() const override {
+    return dict_->primary_hint_stream_length;
+  }
+
+  DummyLinearizedDictionary* const dict_;
+};
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  // Need 28 bytes for |dummy_dict|.
+  // The header section of page offset hint table is 36 bytes.
+  // The header section of shared object hint table is 24 bytes.
+  if (size < 28 + 36 + 24)
+    return 0;
+
+  const int32_t* data32 = reinterpret_cast<const int32_t*>(data);
+  DummyLinearizedDictionary dummy_dict;
+  dummy_dict.end_of_first_page_offset = GetData(&data32, &data, &size);
+  dummy_dict.number_of_pages = GetData(&data32, &data, &size);
+  dummy_dict.first_page_object_number = GetData(&data32, &data, &size);
+  dummy_dict.first_page_number = GetData(&data32, &data, &size);
+  dummy_dict.primary_hint_stream_offset = GetData(&data32, &data, &size);
+  dummy_dict.primary_hint_stream_length = GetData(&data32, &data, &size);
+  dummy_dict.shared_hint_table_offset = GetData(&data32, &data, &size);
+
+  CPDF_Dictionary* dummy_linearized_dict = new CPDF_Dictionary;
+
+  {
+    HintTableForFuzzing hint_table(&dummy_dict, dummy_linearized_dict);
+    hint_table.Fuzz(data, size);
+  }
+
+  dummy_linearized_dict->Release();
+  return 0;
+}