Make chrome_elf use thunks instead of function pointers.

chrome_elf/create_file/chrome_create_file.cc

 // Copyright 2014 The Chromium 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 "chrome_elf/create_file/chrome_create_file.h"
 
 #include <string>
 
 #include "base/strings/string16.h"
 #include "chrome_elf/chrome_elf_constants.h"
 #include "chrome_elf/chrome_elf_util.h"
 #include "chrome_elf/ntdll_cache.h"
+#include "sandbox/win/src/interception_internal.h"
 #include "sandbox/win/src/nt_internals.h"
 
 namespace {
 
 // From ShlObj.h in the Windows SDK.
 #define CSIDL_LOCAL_APPDATA 0x001c
 
 typedef BOOL (WINAPI *PathIsUNCFunction)(
   IN LPCWSTR path);
 
@@ skipping 175 matching lines @@
   else
     flags |= FILE_NON_DIRECTORY_FILE;
 
 
   if (flags_and_attributes & FILE_FLAG_OPEN_REPARSE_POINT)
     flags |= FILE_OPEN_REPARSE_POINT;
 
   if (flags_and_attributes & FILE_FLAG_OPEN_NO_RECALL)
     flags |= FILE_OPEN_NO_RECALL;
 
-  if (!g_ntdll_lookup["NtCreateFile"] ||
-      !g_ntdll_lookup["RtlInitUnicodeString"]) {
+  if (!g_ntdll_lookup["RtlInitUnicodeString"])
+    return INVALID_HANDLE_VALUE;
+
+  NtCreateFileFunction create_file;
+  char thunk_buffer[sizeof(sandbox::ThunkData)] = {};
+
+  if (g_nt_thunk_storage.data[0] != 0) {
+    create_file = reinterpret_cast<NtCreateFileFunction>(&g_nt_thunk_storage);
+    // Copy the thunk data to a buffer on the stack for debugging purposes.
+    memcpy(&thunk_buffer, &g_nt_thunk_storage, sizeof(sandbox::ThunkData));
+  } else if (g_ntdll_lookup["NtCreateFile"]) {
+    create_file =
+        reinterpret_cast<NtCreateFileFunction>(g_ntdll_lookup["NtCreateFile"]);
+  } else {
     return INVALID_HANDLE_VALUE;
   }
 
-  NtCreateFileFunction create_file =
-      reinterpret_cast<NtCreateFileFunction>(g_ntdll_lookup["NtCreateFile"]);
-
   RtlInitUnicodeStringFunction init_unicode_string =
       reinterpret_cast<RtlInitUnicodeStringFunction>(
           g_ntdll_lookup["RtlInitUnicodeString"]);
 
   UNICODE_STRING path_unicode_string;
 
   // Format the path into an NT path. Arguably this should be done with
   // RtlDosPathNameToNtPathName_U, but afaict this is equivalent for
   // local paths. Using this with a UNC path name will almost certainly
   // break in interesting ways.
@@ skipping 85 matching lines @@
   LPCWSTR file_name = g_path_find_filename_func(file_path);
 
   bool in_userdata_dir = !!g_path_is_prefix_func(local_appdata_path, file_path);
   bool is_settings_file = wcscmp(file_name, kPreferencesFilename) == 0 ||
       wcscmp(file_name, kLocalStateFilename) == 0;
 
   // Check if we are trying to access the Preferences in the UserData dir. If
   // so, then redirect the call to bypass kernel32.
   return in_userdata_dir && is_settings_file;
 }