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// Copyright (c) 2006-2008 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.
// Wow_helper.exe is a simple Win32 64-bit executable designed to help to
// sandbox a 32 bit application running on a 64 bit OS. The basic idea is to
// perform a 64 bit interception of the target process and notify the 32-bit
// broker process whenever a DLL is being loaded. This allows the broker to
// setup the interceptions (32-bit) properly on the target.
#include <windows.h>
#include <string>
#include "sandbox/wow_helper/service64_resolver.h"
#include "sandbox/wow_helper/target_code.h"
namespace {
// Grabbed from base/string_util.h
template <class string_type>
inline typename string_type::value_type* WriteInto(string_type* str,
size_t length_with_null) {
str->resize(length_with_null - 1);
return &((*str)[0]);
// Grabbed from base/
std::string WideToMultiByte(const std::wstring& wide, UINT code_page) {
if (wide.length() == 0)
return std::string();
// compute the length of the buffer we'll need
int charcount = WideCharToMultiByte(code_page, 0, wide.c_str(), -1,
if (charcount == 0)
return std::string();
// convert
std::string mb;
WideCharToMultiByte(code_page, 0, wide.c_str(), -1,
WriteInto(&mb, charcount), charcount, NULL, NULL);
return mb;
// Grabbed from base/
std::string WideToUTF8(const std::wstring& wide) {
return WideToMultiByte(wide, CP_UTF8);
} // namespace
namespace sandbox {
// Performs the interception of NtMapViewOfSection on the 64-bit version of
// ntdll.dll. 'thunk' is the buffer on the address space of process 'child',
// that will be used to store the information about the patch.
int PatchNtdll(HANDLE child, void* thunk, size_t thunk_bytes) {
wchar_t* ntdll_name = L"ntdll.dll";
HMODULE ntdll_base = ::GetModuleHandle(ntdll_name);
if (!ntdll_base)
return 100;
Service64ResolverThunk resolver(child);
size_t used = resolver.GetThunkSize();
char* code = reinterpret_cast<char*>(thunk) + used;
NTSTATUS ret = resolver.Setup(ntdll_base, NULL, "NtMapViewOfSection", NULL,
code, thunk, thunk_bytes, NULL);
if (!NT_SUCCESS(ret))
return 101;
size_t size = reinterpret_cast<char*>(&TargetEnd) -
if (size + used > thunk_bytes)
return 102;
SIZE_T written;
if (!::WriteProcessMemory(child, code, &TargetNtMapViewOfSection, size,
return 103;
if (size != written)
return 104;
return 0;
} // namespace sandbox
// We must receive two arguments: the process id of the target to intercept and
// the address of a page of memory on that process that will be used for the
// interception. We receive the address because the broker will cleanup the
// patch when the work is performed.
// It should be noted that we don't wait until the real work is done; this
// program quits as soon as the 64-bit interception is performed.
int wWinMain(HINSTANCE, HINSTANCE, wchar_t* command_line, int) {
COMPILE_ASSERT(sizeof(void*) > sizeof(DWORD), unsupported_32_bits);
if (!command_line)
return 1;
wchar_t* next;
DWORD process_id = wcstoul(command_line, &next, 0);
if (!process_id)
return 2;
HANDLE child = ::OpenProcess(access, FALSE, process_id);
if (!child)
return 3;
DWORD buffer = wcstoul(next, NULL, 0);
if (!buffer)
return 4;
void* thunk = reinterpret_cast<void*>(static_cast<ULONG_PTR>(buffer));
const size_t kPageSize = 4096;
return sandbox::PatchNtdll(child, thunk, kPageSize);