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IWMDMDevice::GetSerialNumber

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The GetSerialNumber method retrieves a serial number that uniquely identifies the device.

Syntax

HRESULT GetSerialNumber(PWMDMIDpSerialNumber,BYTE[WMDM_MAC_LENGTH]abMac);

Parameters

pSerialNumber

[out]  Pointer to a WMDMID structure specifying the serial number information. The WMDID structure is allocated and released by the application.

abMac

[in, out]  Array of bytes specifying the message authentication code for the parameter data of this method.

Return Values

The method returns an HRESULT. All the interface methods in Windows Media Device Manager can return any of the following classes of error codes:

  • Standard COM error codes
  • Windows error codes converted to HRESULT values
  • Windows Media Device Manager error codes

For an extenstive list of possible error codes, see Error Codes.

Possible values include, but are not limited to, those in the following table.

Return code Description
S_OK The method succeeded.
E_INVALIDARG The pSerialNumber parameter is an invalid or NULL pointer.
WMDM_E_NOTSUPPORTED The device does not support serial numbers.
E_FAIL An unspecified error occurred.

Remarks

Not all devices support serial numbers. To determine whether the device supports serial numbers, the caller must always check the return code when calling this function. If a media device supports serial numbers, the serial number of the media device is guaranteed to be unique for that device.

After calling this method, an application can verify that the serial has not been modified during transport by using the abMAC parameter. For example code on this, see Using Secure Authenticated Channels.

Example Code

The following C++ code retrieves the device serial number and verifies the MAC.

//
// Get and verify the serial number.
//
WMDMID serialNumber;
BYTE receivedMAC[WMDM_MAC_LENGTH];
hr = pIWMDMDevice->GetSerialNumber(&serialNumber, receivedMAC);

// Check the MAC to guarantee the serial number has not been tampered with.
if (hr == S_OK)
{
    // Initialize a MAC handle, 
    // next add all parameters to the MAC,
    // and finally retrieve the calculated MAC value.
    HMAC hMAC;
    BYTE calculatedMAC[WMDM_MAC_LENGTH];
    hr = m_pSAC->MACInit(&hMAC);
    hr = m_pSAC->MACUpdate(hMAC, (BYTE*)(&serialNumber), sizeof(serialNumber));
    hr = m_pSAC->MACFinal(hMAC, (BYTE*)calculatedMAC);
    if (memcmp(calculatedMAC, receivedMAC, sizeof(calculatedMAC)) == 0)
    {
        // MAC is authentic. Print the serial number.
        CHAR* serialNumberBuffer = new CHAR[serialNumber.SerialNumberLength + 1];
        ZeroMemory(serialNumberBuffer, (serialNumber.SerialNumberLength + 1) * sizeof(CHAR));
        memcpy(serialNumberBuffer, serialNumber.pID, serialNumber.SerialNumberLength * sizeof(CHAR));
        // TODO: Display the serial number.
        delete serialNumberBuffer;
    }
    else
        // TODO: Display a message indicating that the serial number MAC does not match in EnumDevices
}

Requirements

Header: Defined in mswmdm.h.

Library: mssachlp.lib

See Also