HOWTO: IObjectSafety Marks ATL Controls Safe for Initializing

• Microsoft Active Template Library (ATL), versions 2.0, 2.1
• Microsoft Active Template Library (ATL), included with:

      - Microsoft Visual C++, 32-bit Editions, version 5.0
  

SUMMARY

You can use the default implementation of IObjectSafetyImpl to mark a control as safe for scripting. In many cases, you will also want to mark the control as safe for initialization.

NOTE: Only mark your control as safe for scripting or initialization if it really is safe. If the control is potentially unsafe and it is marked as safe, you may be held liable for damages. See the REFERENCES section below for more information.

MORE INFORMATION

The steps you need to take to get the desired functionality involve using IObjectSafetyImpl as one of the classes that your control derives from and overriding GetInterfaceSafetyOptions and SetInterfaceSafetyOptions. This allows you to implement the desired functionality, which in this case means marking the control as safe for scripting and initialization.

To use IObjectSafetyImpl, you need to add it to the list of classes your control is derived from. For example, in the Polygon tutorial you see the following:

   class ATL_NO_VTABLE CPolyCtl :
   ...
      public IObjectSafetyImpl<CPolyCtl> // ATL's version of
                                        // IObjectSafety
   {
   public:
      BEGIN_COM_MAP(CPolyCtl)
   ...
         COM_INTERFACE_ENTRY_IMPL(IObjectSafety) // Tie IObjectSafety
                                                 // to this COM map
      END_COM_MAP()

   STDMETHOD(GetInterfaceSafetyOptions)(REFIID riid,
                                     DWORD *pdwSupportedOptions,
                                     DWORD *pdwEnabledOptions)
   {
   ATLTRACE(_T("CObjectSafetyImpl::GetInterfaceSafetyOptions\n"));
   if (!pdwSupportedOptions || !pdwEnabledOptions)
      return E_FAIL;
   LPUNKNOWN pUnk;
   if (_InternalQueryInterface (riid, (void**)&pUnk) == E_NOINTERFACE) {
      // Our object doesn't even support this interface.
      return E_NOINTERFACE;
   }else{
      // Cleanup after ourselves.
      pUnk->Release();
      pUnk = NULL;
   }
   if (riid == IID_IDispatch) {
      // IDispatch is an interface used for scripting. If your
      // control supports other IDispatch or Dual interfaces, you
      // may decide to add them here as well. Client wants to know
      // if object is safe for scripting. Only indicate safe for
      // scripting when the interface is safe.
      *pdwSupportedOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER;
      *pdwEnabledOptions = m_dwSafety &
                           INTERFACESAFE_FOR_UNTRUSTED_CALLER;
      return S_OK;
   }else if ((riid == IID_IPersistStreamInit) ||
             (riid == IID_IPersistStorage)) {
      // IID_IPersistStreamInit and IID_IPersistStorage are
      // interfaces used for Initialization. If your control
      // supports other Persistence interfaces, you may decide to
      // add them here as well. Client wants to know if object is
      // safe for initializing. Only indicate safe for initializing
      // when the interface is safe.
      *pdwSupportedOptions = INTERFACESAFE_FOR_UNTRUSTED_DATA;
      *pdwEnabledOptions = m_dwSafety &
                           INTERFACESAFE_FOR_UNTRUSTED_DATA;
      return S_OK;
   }else{
      // We are saying that no other interfaces in this control are
      // safe for initializing or scripting.
      *pdwSupportedOptions = 0;
      *pdwEnabledOptions = 0;
      return E_FAIL;
   }
   }

   STDMETHOD(SetInterfaceSafetyOptions)(REFIID riid,
                                     DWORD dwOptionSetMask,
                                     DWORD dwEnabledOptions)
   {
   ATLTRACE(_T("CObjectSafetyImpl::SetInterfaceSafetyOptions\n"));
   if (!dwOptionSetMask && !dwEnabledOptions) return E_FAIL;
   LPUNKNOWN pUnk;
   if (_InternalQueryInterface (riid, (void**)&pUnk) == E_NOINTERFACE) {
      // Our object doesn't even support this interface.
      return E_NOINTERFACE;
   }else{
      // Cleanup after ourselves.
      pUnk->Release();
      pUnk = NULL;
   }
   // Store our current safety level to return in
   // GetInterfaceSafetyOptions
   m_dwSafety |= dwEnabledOptions & dwOptionSetMask;
   if ((riid == IID_IDispatch) &&
       (m_dwSafety & INTERFACESAFE_FOR_UNTRUSTED_CALLER)) {
      // Client wants us to disable any functionality that would
      // make the control unsafe for scripting. The same applies to
      // any other IDispatch or Dual interfaces your control may
      // support. Because our control is safe for scripting by
      // default we just return S_OK.
      return S_OK;
   }else if (((riid == IID_IPersistStreamInit) ||
              (riid == IID_IPersistStorage)) &&
             (m_dwSafety & INTERFACESAFE_FOR_UNTRUSTED_DATA)) {
      // Client wants us to make the control safe for initializing
      // from persistent data. For these interfaces, this control
      // is safe so we return S_OK. For Any interfaces that are not
      // safe, we would return E_FAIL.
      return S_OK;
   }else{
      // This control doesn't allow Initialization or Scripting
      // from any other interfaces so return E_FAIL.
      return E_FAIL;
   }
   }
   ...
   }

REFERENCES

For additional information about marking ActiveX controls as safe for scripting and initialization, please see the following articles in the Microsoft Knowledge Base:

   ARTICLE-ID: Q161873
   TITLE     : HOWTO: Mark MFC Controls Safe for Scripting/Initialization

   ARTICLE-ID: Q164119
   TITLE     : SAMPLE: Implementing IObjectSafety in an ActiveX control

   http://microsoft.com/intdev/controls/stoplite/

   http://microsoft.com/intdev/controls/signmark-f.htm

Keywords          : AtlControl AtlIss AXSDKControls MfcOLE kbprg
Technology        : kbAtl kbole kbInetDev kbMfc
Version           : 2.0,2.1,5.0
Platform          : NT WINDOWS
Issue type        : kbhowto