This support function specifies the certificate context for the first certificate in the client's certificate chain.
BOOL ServerSupportFunction(
HCONN ConnID,
DWORD HSE_REQ_GET_CERT_INFO_EX,
LPVOID lpvBuffer,
LPDWORD lpdwSize,
LPDWORD lpdwDataType
);
To use this support function, your ISAPI extension must first create a new CERT_CONTEXT_EX structure. The primary member of that structure is the CryptoAPI CERT_CONTEXT structure. You must allocate the buffer that is embedded in the CERT_CONTEXT structure.