关于IObjectSafety的思考

讨论了COM组件在浏览器中使用时的安全问题,特别是通过实现IObjectSafety接口来避免IE的安全提示,以及这种做法可能带来的风险。
经常在网页里嵌入COM组件,而且为了避免IE的提示,我们常常让其实现IObjectSafety接口,以告诉IE说我是安全的,请不要提示啦!还真奇怪,IE就乖乖的听话,不提示了.我一直很怀疑微软这样做的道理是什么?因为COM对象只要实现这个接口,IE就相信它,这样还有什么意义呢?

后来,我想明白了,因为COM组件在使用前需要首先安装/注册,这时候一般都需要用户进行参与,所以也算是用户同意和相信该COM组件了.

现在,我又想到了一个问题.我写的COM组件也完全有可能被人利用啊,因为在HTML里,所有的代码都是公开的!如果一个人写的COM组件有一些比较危险的操作,比如操作本地文件...这个问题是在我尝试使用MSXML打开本地文件的时候遇到的,当访问Web上页面的时候,MSXML对象是不允许打开本地对象的--这让我想起了Cross-Domain脚本的安全限制问题。如果没有这一点的话,打开一个危险的网页的话,这个网页就可以窃取本地数据的信息或者进行破坏!另一个对象Scripting.FileSystemObject虽然没有这个限制,但是其没有实现IObjectSafety接口,IE会弹出警告提示窗口!

难怪说IE的安全漏洞比较多呢,因为有太多的COM组件.FireFox好像干脆就不支持COM组件,看你还有什么漏洞!

还是回到开头的话题,一个负责任的COM组件,不应该随随便便把自己声明为脚本安全,即实现IObjectSafety接口,以免被外人利用.想想看,访问一个恶意的网站,其页面调用了你的COM组件,没有任何提示,就对用户的数据进行了窃取和破坏...这是助纣为虐啊!

所以,是让IE出现提示呢,还是不出现?这是一个问题.
需要用来获得所需的功能在步骤涉及到 IObjectSafetyImpl 用作您的控件派生的类之一,和重写 GetInterfaceSafetyOptions 和 SetInterfaceSafetyOptions。 这使您实现所需的功能在这种情况下意味着将标记为可安全编写脚本和初始化该控件。 若要将 IObjectSafetyImpl 需要将其添加到您的控件派生的类的列表。 是例如多边形教程中您看到以下: class ATL_NO_VTABLE CPolyCtl : ... public IObjectSafetyImpl // 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; } } ... } ATL 3.0 中, IObjectSafetyImpl 的实现已更改,使您现在可以作为模板参数提供安全选项。 例如,上述类的声明将显示为 class ATL_NO_VTABLE CPolyCtl : ... public IObjectSafetyImpl { public: BEGIN_COM_MAP(CPolyCtl) ... ,您将不必重写两个方法。 有关其他信息,单击下面,文章编号,以查看 Microsoft 知识库中相应: 192093 PRB: 编译器错误时移植到 ATL 3.0 IObjectSafetyImpl
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