Building an ISO7816-4 APDU Command

To add functionality to a service provider, you need to know how an ISO7816-4 application protocol data unit (APDU) is built within the base service provider DLLs. The following procedure gives a brief overview of the build process.

Note

The example included here is not necessarily complete; for more information, see the sample applications and DLLs.

 

To build an ISO7816-4 APDU command

1. Create an ISCardCmd object and an ISCardISO7816 object.

   //  Create an ISCardCmd object.
   HRESULT hresult = CoCreateInstance(CLSID_CSCardCmd,
                              NULL,
                              CLSCTX_ALL,
                              IID_ISCardCmd,
                              (LPVOID*) &g_pISCardCmd);
   //  Create an ISCardISO7816 object.
   HRESULT hresult = CoCreateInstance(CLSID_CSCardISO7816,
                              NULL,
                              CLSCTX_ALL,
                              IID_ISCardISO7816,
                              (LPVOID*) &g_pISCardISO7816);
   

   The ISCardCmd interface contains two IByteBuffer buffers. One buffer contains the actual APDU command string (plus any data to send with the command). The other contains any reply information returned by the card after command execution.

2. Using these objects, create a valid ISO7816-4 command as follows:

   //  Do challenge.
   HRESULT hresult = g_pISCardISO7816->GetChallenge(dwLengthOfChallenge,
                                            &g_pISCardCmd);
   

   Here is the code used in the GetChallenge method:

   #include <windows.h>
   
   STDMETHODIMP CSCardISO7816::GetChallenge(IN DWORD dwBytesExpected /*= 0*/,
                               IN OUT LPSCARDCMD *ppCmd)
   {
       //  Locals.
       HRESULT hr = S_OK;
   
       try
       {
           //  Is the ISCardCmd object okay?
           hr = IsSCardCmdValid(ppCmd);
           if (FAILED(hr))
               throw (hr);
   
           //  Do it.
           hr = (*ppCmd)->BuildCmd(m_byClassId,
                                   (BYTE) INS_GET_CHALLENGE,
                                   (BYTE) INS_NULL,  // P1 = 0x00
                                   (BYTE) INS_NULL,  // P2 = 0x00
                                   NULL,
                                   &dwBytesExpected);
           if (FAILED(hr))
               throw (hr);
       }
   }
   

   The ISCardISO7816::GetChallenge method uses the ISCardCmd::BuildCmd method to build the requested APDU. This is done by writing the appropriate information into the ISCardCmd APDU buffer in the following statement:

   hr = (*ppCmd)->BuildCmd;
   

3. Using the built ISCardCmd object, do a transaction with the card, interpret the results, and continue.

Expanding Beyond ISO7816-4

The recommended way to expand the service provider build/execute process described above is to create a new COM object. This COM object should support a new interface that allows creation of non-ISO7816-4 commands and should aggregate the ISCardISO7816 interface.

Example of Building an ISO7816-4 APDU Command

The following example shows the code used in the procedure above.

//  Create an ISCardCmd object.
hresult = CoCreateInstance(CLSID_CSCardCmd,
                           NULL,
                           CLSCTX_ALL,
                           IID_ISCardCmd,
                           (LPVOID*) &g_pISCardCmd);
//  Create an ISCardISO7816 object.
hresult = CoCreateInstance(CLSID_CSCardISO7816,
                           NULL,
                           CLSCTX_ALL,
                           IID_ISCardISO7816,
                           (LPVOID*) &g_pISCardISO7816);
//  Do challenge.
hresult = g_pISCardISO7816->GetChallenge(dwLengthOfChallenge,
                                         &g_pISCardCmd);

STDMETHODIMP
CSCardISO7816::GetChallenge(IN DWORD dwBytesExpected /*= 0*/,
                            IN OUT LPSCARDCMD *ppCmd)
{
    //  Locals.
    HRESULT hr = S_OK;
    
    try
    {
        //  Is the ISCardCmd object okay?
        hr = IsSCardCmdValid(ppCmd);
        if (FAILED(hr))
            throw (hr);

        //  Do it.
        hr = (*ppCmd)->BuildCmd(m_byClassId,
                                (BYTE) INS_GET_CHALLENGE,
                                (BYTE) INS_NULL,  // P1 = 0x00
                                (BYTE) INS_NULL,  // P2 = 0x00
                                NULL,
                                &dwBytesExpected);
        if (FAILED(hr))
            throw (hr);
    }
}