这篇谈下c++如何hook网页中的JS函数，即网页可以执行我们修改的JS函数。
相应的步骤可分为：
1.找到需要修改函数的时机。
2.得到需要修改函数的com对象。
3.将我们新的com对象替换修改函数。
第一步，找到需要修改函数的时机，在谈这个问题之前，需要搞清楚JS执行发生在什么时候。
我们知道在网页加载过程中，会根据接收到的html文本，去解析对应里面的脚本和样式以及js。
譬如：
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>了解html页面的渲染过程 - yuezk - 博客园</title>
<link type="text/css" rel="stylesheet" href="/bundles/blog-common.css?v=Rdf1BBttS5_qVaET1myrajVTd62BSCCoJA9fZxGv1ZM1">
<link id="MainCss" type="text/css" rel="stylesheet" href="/skins/LessIsMoreRight/bundle-LessIsMoreRight.css?v=XnHJrmT6UJMtyGfeJjiTUm7BxKWcwdJrxKsGy7z3YZ81">
<link id="mobile-style" media="only screen and (max-width: 768px)" type="text/css" rel="stylesheet" href="/skins/LessIsMoreRight/bundle-LessIsMoreRight-mobile.css?v=9qDppl1UU68AUflWXI5a_NeoqamVC_84o7AG1HNc4Pg1">
<link title="RSS" type="application/rss+xml" rel="alternate" href="http://www.cnblogs.com/yuezk/rss">
<link title="RSD" type="application/rsd+xml" rel="EditURI" href="http://www.cnblogs.com/yuezk/rsd.xml">
<link type="application/wlwmanifest+xml" rel="wlwmanifest" href="http://www.cnblogs.com/yuezk/wlwmanifest.xml">
<script type="text/javascript" src="http://common.cnblogs.com/script/encoder.js"></script><script src="//common.cnblogs.com/script/jquery.js" type="text/javascript"></script>
<script type="text/javascript">var currentBlogApp = 'yuezk', cb_enable_mathjax=false;var isLogined=false;</script>
<script src="/bundles/blog-common.js?v=hH1lCMV8WaIu271Nx7jPuv36TENW9-RsSxziLxUpjtc1" type="text/javascript"></script>
</head>void CWebLoginDlg::OnDocumentComplete(LPDISPATCH pDisp, LPCTSTR szUrl)
{CDHtmlDialog::OnDocumentComplete(pDisp, szUrl);// TODO: Add your specialized code here and/or call the base classIUnknown* pUnk;LPDISPATCH lpWBDisp;HRESULT hr;pUnk = m_wndBrowser.GetControlUnknown();ASSERT(pUnk);hr = pUnk->QueryInterface(IID_IDispatch, (void**)&lpWBDisp);ASSERT(SUCCEEDED(hr));CComPtr<IHTMLDocument2> sphtmlDoc;GetDHtmlDocument(&sphtmlDoc);if (sphtmlDoc != NULL){CWebPage web;VARIANT testV;web.SetDocument(sphtmlDoc);CComPtr<IDispatch> pDispatch = NULL;web.GetJScript(pDispatch);HRESULT result = GetProperty(pDispatch, L"TK_installPage", &testV); //得到修改函数的com对象if (result == S_OK){VARIANT params;params.vt = VT_DISPATCH;params.pdispVal = new JsFunction(button1_onclick);result = SetProperty(pDispatch, L"TK_installPage", ¶ms);//将我们的button1_onclick函数替换修改函数}}if (pDisp == lpWBDisp ){// Top-level Window object, so document has been loadedTRACE("Web document is finished downloading\n");}lpWBDisp->Release();
第二步，得到修改函数的com对象。这里TK_installPage函数就是我们的要修改的函数。首先获取doc对象，然后根据doc对象通过GetJScript获得脚本对象，再次在脚本对象上通过名字TK_installPage得到js对象。具体代码如下：
bool CWebPage::SetDocument(IDispatch* pDisp)
{CHECK_POINTER(pDisp);m_spDoc = NULL;CComPtr<IDispatch> spDisp = pDisp;HRESULT hr = spDisp->QueryInterface(IID_IHTMLDocument2,(void**)&m_spDoc);if(FAILED(hr)){ShowError(L"Failed to get HTML document COM object");return false;}return true;
}bool CWebPage::GetJScript(CComPtr<IDispatch>& spDisp)
{CHECK_POINTER(m_spDoc);HRESULT hr = m_spDoc->get_Script(&spDisp);ATLASSERT(SUCCEEDED(hr));return SUCCEEDED(hr);
}DISPID CWebLoginDlg::FindId( IDispatch *pObj, LPOLESTR pName )
{DISPID id = 0;if(FAILED(pObj->GetIDsOfNames(IID_NULL,&pName,1,LOCALE_SYSTEM_DEFAULT,&id))) id = -1;return id;
}HRESULT CWebLoginDlg::GetProperty( IDispatch *pObj, LPOLESTR pName, VARIANT *pValue )
{DISPID dispid = FindId(pObj, pName);if(dispid == -1) return E_FAIL;DISPPARAMS ps;ps.cArgs = 0;ps.rgvarg = NULL;ps.cNamedArgs = 0;ps.rgdispidNamedArgs = NULL;return pObj->Invoke(dispid, IID_NULL, LOCALE_SYSTEM_DEFAULT, DISPATCH_PROPERTYGET, &ps, pValue, NULL, NULL);
}
首先需要构造我们新的com对象，
typedef void _stdcall JsFunction_Callback();class JsFunction:public IDispatch
{long _refNum;JsFunction_Callback *m_pCallback;
public:JsFunction(JsFunction_Callback *pCallback){_refNum = 1;m_pCallback = pCallback;}~JsFunction(void){}
public:// IUnknown MethodsSTDMETHODIMP QueryInterface(REFIID iid,void**ppvObject){*ppvObject = NULL;if (iid == IID_IOleClientSite) *ppvObject = (IOleClientSite*)this;else if (iid == IID_IUnknown) *ppvObject = this;if(*ppvObject){AddRef();return S_OK;}return E_NOINTERFACE;}STDMETHODIMP_(ULONG) AddRef(){return ::InterlockedIncrement(&_refNum);}STDMETHODIMP_(ULONG) Release(){::InterlockedDecrement(&_refNum);if(_refNum == 0){delete this;}return _refNum;}// IDispatch MethodsHRESULT _stdcall GetTypeInfoCount(unsigned int * pctinfo) {return E_NOTIMPL;}HRESULT _stdcall GetTypeInfo(unsigned int iTInfo,LCID lcid,ITypeInfo FAR* FAR* ppTInfo) {return E_NOTIMPL;}HRESULT _stdcall GetIDsOfNames(REFIID riid, OLECHAR FAR* FAR* rgszNames, unsigned int cNames, LCID lcid, DISPID FAR* rgDispId ){//令人费解的是，网页调用函数的call方法时，没有调用GetIDsOfNames获取call的ID，而是直接调用Invokereturn E_NOTIMPL;}HRESULT _stdcall Invoke(DISPID dispIdMember,REFIID riid,LCID lcid,WORD wFlags,DISPPARAMS* pDispParams,VARIANT* pVarResult,EXCEPINFO* pExcepInfo,unsigned int* puArgErr){//这里执行我们的替换函数m_pCallback();return S_OK;}
};static void _stdcall button1_onclick()
{ATLTRACE("test");
}
其次，通过com对象的invoke函数进行替换。代码如下：
HRESULT CWebLoginDlg::SetProperty( IDispatch *pObj, LPOLESTR pName, VARIANT *pValue )
{DISPID dispid = FindId(pObj, pName);if(dispid == -1) return E_FAIL;DISPID dispidNamed = DISPID_PROPERTYPUT;DISPPARAMS ps;ps.cArgs = 1;ps.rgvarg = pValue;ps.cNamedArgs = 1;ps.rgdispidNamedArgs = &dispidNamed;return pObj->Invoke(dispid, IID_NULL, LOCALE_SYSTEM_DEFAULT, DISPATCH_PROPERTYPUT, &ps, NULL, NULL, NULL);
}
最终效果，在网页在执行TK_installPage函数时候，实际上是执行的我们的函数button1_onclick。
