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wmi_util.cc

// 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.

#include <windows.h>
#include "base/basictypes.h"
#include "base/scoped_bstr_win.h"
#include "base/scoped_comptr_win.h"

#pragma comment(lib, "wbemuuid.lib")

#include "base/wmi_util.h"

namespace {
// Simple class to manage the lifetime of a variant.
// TODO(tommi): Replace this for a more useful class.
class VariantHelper : public VARIANT {
 public:
  VariantHelper() {
    vt = VT_EMPTY;
  }
  explicit VariantHelper(VARTYPE type) {
    vt = type;
  }
  ~VariantHelper() {
    ::VariantClear(this);
  }
 private:
  DISALLOW_COPY_AND_ASSIGN(VariantHelper);
};

}  // namespace

bool WMIUtil::CreateLocalConnection(bool set_blanket,
                                    IWbemServices** wmi_services) {
  ScopedComPtr<IWbemLocator> wmi_locator;
  HRESULT hr = wmi_locator.CreateInstance(CLSID_WbemLocator, NULL,
                                          CLSCTX_INPROC_SERVER);
  if (FAILED(hr))
    return false;

  ScopedComPtr<IWbemServices> wmi_services_r;
  hr = wmi_locator->ConnectServer(StackBstr(L"ROOT\\CIMV2"), NULL, NULL, 0,
                                  NULL, 0, 0, wmi_services_r.Receive());
  if (FAILED(hr))
    return false;

  if (set_blanket) {
    hr = ::CoSetProxyBlanket(wmi_services_r,
                             RPC_C_AUTHN_WINNT,
                             RPC_C_AUTHZ_NONE,
                             NULL,
                             RPC_C_AUTHN_LEVEL_CALL,
                             RPC_C_IMP_LEVEL_IMPERSONATE,
                             NULL,
                             EOAC_NONE);
    if (FAILED(hr))
      return false;
  }

  *wmi_services = wmi_services_r.Detach();
  return true;
}

bool WMIUtil::CreateClassMethodObject(IWbemServices* wmi_services,
                                      const std::wstring& class_name,
                                      const std::wstring& method_name,
                                      IWbemClassObject** class_instance) {
  // We attempt to instantiate a COM object that represents a WMI object plus
  // a method rolled into one entity.
  ScopedBstr b_class_name(class_name.c_str());
  ScopedBstr b_method_name(method_name.c_str());
  ScopedComPtr<IWbemClassObject> class_object;
  HRESULT hr;
  hr = wmi_services->GetObject(b_class_name, 0, NULL,
                               class_object.Receive(), NULL);
  if (FAILED(hr))
    return false;

  ScopedComPtr<IWbemClassObject> params_def;
  hr = class_object->GetMethod(b_method_name, 0, params_def.Receive(), NULL);
  if (FAILED(hr))
    return false;

  if (NULL == params_def) {
    // You hit this special case if the WMI class is not a CIM class. MSDN
    // sometimes tells you this. Welcome to WMI hell.
    return false;
  }

  hr = params_def->SpawnInstance(0, class_instance);
  return(SUCCEEDED(hr));
}

bool SetParameter(IWbemClassObject* class_method,
                  const std::wstring& parameter_name, VARIANT* parameter) {
  HRESULT hr = class_method->Put(parameter_name.c_str(), 0, parameter, 0);
  return SUCCEEDED(hr);
}


// The code in Launch() basically calls the Create Method of the Win32_Process
// CIM class is documented here:
// http://msdn2.microsoft.com/en-us/library/aa389388(VS.85).aspx

bool WMIProcessUtil::Launch(const std::wstring& command_line, int* process_id) {
  ScopedComPtr<IWbemServices> wmi_local;
  if (!WMIUtil::CreateLocalConnection(true, wmi_local.Receive()))
    return false;

  const wchar_t class_name[] = L"Win32_Process";
  const wchar_t method_name[] = L"Create";
  ScopedComPtr<IWbemClassObject> process_create;
  if (!WMIUtil::CreateClassMethodObject(wmi_local, class_name, method_name,
                                        process_create.Receive()))
    return false;

  VariantHelper b_command_line(VT_BSTR);
  b_command_line.bstrVal = ::SysAllocString(command_line.c_str());

  if (!SetParameter(process_create, L"CommandLine", &b_command_line))
    return false;

  ScopedComPtr<IWbemClassObject> out_params;
  HRESULT hr = wmi_local->ExecMethod(StackBstr(class_name),
                                     StackBstr(method_name), 0, NULL,
                                     process_create, out_params.Receive(),
                                     NULL);
  if (FAILED(hr))
    return false;

  VariantHelper ret_value;
  hr = out_params->Get(L"ReturnValue", 0, &ret_value, NULL, 0);
  if (FAILED(hr) || (0 != ret_value.uintVal))
    return false;

  VariantHelper pid;
  hr = out_params->Get(L"ProcessId", 0, &pid, NULL, 0);
  if (FAILED(hr) || (0 == pid.intVal))
    return false;

  if (process_id)
    *process_id = pid.intVal;

  return true;
}

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